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Sample records for electrocatalysts

  1. Electrocatalysts for oxygen electrodes

    SciTech Connect

    Yeager, E.B. )

    1991-10-01

    The objectives of the research were: to develop further understanding of the factors controlling O{sub 2} reduction and generation on various electrocatalysts, including transition metal macrocycles and oxides: to use this understanding to identify and develop much higher activity catalysts, both monofunction and bifunction; and to establish how catalytic activity for a given O{sub 2} electrocatalyst depends on catalyst-support interactions and to identify stable catalyst supports for bifunctional electrodes.

  2. Impurity tolerant electrocatalysts

    SciTech Connect

    Paffett, M.T.

    1990-01-01

    This project has two central goals. The primary research effort addresses fundamental aspects of Pt electrocatalyst poisoning by CO and an understanding of practical schemes for improving the CO tolerance of electrocatalytic materials. The second mission of this work is an attempt to address, on a fundamental level, the surface chemical properties that enhance the direct electrooxidation of methanol at binary Pt alloy electrode surfaces. 8 refs., 4 figs.

  3. Palladium-based electrocatalysts and fuel cells employing such electrocatalysts

    SciTech Connect

    Masel; Richard I. , Zhu; Yimin , Larsen; Robert T.

    2010-08-31

    A direct organic fuel cell includes a fluid fuel comprising formic acid, an anode having an electrocatalyst comprising palladium nanoparticles, a fluid oxidant, a cathode electrically connected to the anode, and an electrolyte interposed between the anode and the cathode.

  4. Electrocatalysts for oxygen electrodes

    SciTech Connect

    Yeager, E. . Dept. of Chemistry Case Western Reserve Univ., Cleveland, OH . Case Center for Electrochemical Sciences)

    1990-10-01

    The overall objective of this research was an in-depth understanding of the factors controlling O{sub 2} reduction and generation on various electrocatalysts and the use of this understanding to identify much higher activity, stable catalysts. The following is a brief summary of the research for the period 1 April 1989 to 31 March 1990. (1) Transition metal monomeric and sheet-polymeric macrocycle catalysts -- The iron tetrasulfonated phthalocyanine (FeTsPc) complex adsorbed on an electrode surface has high activity for the 4-electron reduction of O{sub 2} to water or OH{sup {minus}} in alkaline solutions. (2) Polymer-modified electrodes -- Poly(4-vinyl pyridine) (PVP)-modified electrodes with adsorbed CoTsPc exhibited much higher catalytic activity for O{sub 2} reduction than the electrode with only adsorbed CoTsPc in acid solutions. (3) Transition metal oxide catalysts and bifunctional electrodes -- Anion-exchange membranes were found to greatly improve the performance of the pyrochlore-based bifunctional oxygen electrodes when operating in the O{sub 2} generation mode. (4) Catalyst supports -- The use of mildly fluorinated carbon blacks as catalyst supports for platinum was explored in cooperation with the Electrosynthesis Company (ESC). 23 refs., 28 figs., 7 tabs.

  5. Electrocatalysts for carbon dioxide conversion

    SciTech Connect

    Masel, Richard I; Salehi-Khojin, Amin

    2015-04-21

    Electrocatalysts for carbon dioxide conversion include at least one catalytically active element with a particle size above 0.6 nm. The electrocatalysts can also include a Helper Catalyst. The catalysts can be used to increase the rate, modify the selectivity or lower the overpotential of electrochemical conversion of CO.sub.2. Chemical processes and devices using the catalysts also include processes to produce CO, HCO.sup.-, H.sub.2CO, (HCO.sub.2).sup.-, H.sub.2CO.sub.2, CH.sub.3OH, CH.sub.4, C.sub.2H.sub.4, CH.sub.3CH.sub.2OH, CH.sub.3COO.sup.-, CH.sub.3COOH, C.sub.2H.sub.6, (COOH).sub.2, or (COO.sup.-).sub.2, and a specific device, namely, a CO.sub.2 sensor.

  6. Electrocatalysts using porous polymers and method of preparation

    DOEpatents

    Liu, Di-Jia; Yuan, Shengwen; Goenaga, Gabriel A.

    2016-08-02

    A method of producing an electrocatalyst article using porous polymers. The method creates a porous polymer designed to receive transition metal groups disposed at ligation sites and activating the transition metals to form an electrocatalyst which can be used in a fuel cell. Electrocatalysts prepared by this method are also provided. A fuel cell which includes the electrocatalyst is also provided.

  7. Photocatalytic methods for preparation of electrocatalyst materials

    DOEpatents

    Nwoga, Tochi Tudor; Kawahara, Kazuo; Li, Wen; Song, Yujiang; Shelnutt, John A; Miller, James E; Medforth, Craig John; Ueno, Yukiyoshi; Kawamura, Tetsuo

    2013-12-17

    The invention relates to methods of preparing metal particles on a support material, including platinum-containing nanoparticles on a carbon support. Such materials can be used as electrocatalysts, for example as improved electrocatalysts in proton exchange membrane fuel cells (PEM-FCs).

  8. Photocatalytic methods for preparation of electrocatalyst materials

    DOEpatents

    Li, Wen; Kawamura, Tetsuo; Nagami, Tetsuo; Takahashi, Hiroaki; Muldoon, John; Shelnutt, John A; Song, Yujiang; Miller, James E; Hickner, Michael A; Medforth, Craig

    2013-09-24

    The invention relates to methods of preparing metal particles on a support material, including platinum-containing nanoparticles on a carbon support. Such materials can be used as electrocatalysts, for example as improved electrocatalysts in polymer electrolyte membrane fuel cells (PEM-FCs).

  9. Lead-ruthenium pyrochlores as oxygen electrocatalysts

    NASA Technical Reports Server (NTRS)

    Anderson, E. B.; Taylor, E. J.; Moniz, G. A.

    1990-01-01

    An investigation of lead-ruthenium pyrochlores of the structure Pb2(Ru/2-x/Pb/x/) O7-y for use as oxygen electrocatalysts in alkaline media is discussed. Lead-ruthenium pyrochlore mixed metal oxides were prepared and characterized by X-ray diffraction, BET surface area, dry powder conductivity, and chemical stability. Gas diffusion electrodes were developed specifically for the lead-ruthenium pyrochlore materials. Also investigated were the effects of varying electrode fabrication parameters on the oxygen reduction performance of the lead-ruthenium pyrochlore electrocatalyst. Long-term stability performance was also evaluated. The oxygen reduction performance of the pyrochlore electrocatalyst is considerably higher than that of the state-of-the-art gold-platinum alloy electrocatalyst currently used by NASA. Furthermore, the pyrochlore electrocatalysts are attractive candidates for high-performance pressurized alkaline fuel cells.

  10. Electrocatalyst for alcohol oxidation in fuel cells

    DOEpatents

    Adzic, Radoslav R.; Marinkovic, Nebojsa S.

    2001-01-01

    Binary and ternary electrocatalysts are provided for oxidizing alcohol in a fuel cell. The binary electrocatalyst includes 1) a substrate selected from the group consisting of NiWO.sub.4 or CoWO.sub.4 or a combination thereof, and 2) Group VIII noble metal catalyst supported on the substrate. The ternary electrocatalyst includes 1) a substrate as described above, and 2) a catalyst comprising Group VIII noble metal, and ruthenium oxide or molybdenum oxide or a combination thereof, said catalyst being supported on said substrate.

  11. Electrocatalysts for oxygen electrodes. Final report

    SciTech Connect

    Yeager, E.B.

    1991-10-01

    The objectives of the research were: to develop further understanding of the factors controlling O{sub 2} reduction and generation on various electrocatalysts, including transition metal macrocycles and oxides: to use this understanding to identify and develop much higher activity catalysts, both monofunction and bifunction; and to establish how catalytic activity for a given O{sub 2} electrocatalyst depends on catalyst-support interactions and to identify stable catalyst supports for bifunctional electrodes.

  12. New Electrocatalysts by Combinatorial Methods

    NASA Astrophysics Data System (ADS)

    Smotkin, Eugene S.; Diaz-Morales, Robert R.

    2003-08-01

    Combinatorial methods provide a means for accelerating the discovery of fuel cell catalysts. The first example of parallel fuel cell catalysts screening was an indirect method that used fluorescent chemosensors to detect changes in pH in proximity to electrocatalyst spots. Serial direct electrochemical methods have been developed that use voltammetry, chronoamperometry, and scanning electrochemical microscopy. An array fuel cell screens catalysts simultaneously, using high-performance fuel cell components. Heuristic models based on mechanistic and spectroscopic studies provide guidance for library development, and detailed studies of discovered catalysts can help to refine these models. The remaining challenges are the development of high throughput synthetic methods that can enable the use of discovery level and focus level screening. Until these synthetic methods are developed, a greater emphasis should be placed on smaller libraries with design of experiment strategies leveraged with informatics and data mining.

  13. Electrocatalyst for alcohol oxidation at fuel cell anodes

    DOEpatents

    Adzic, Radoslav; Kowal, Andrzej

    2011-11-02

    In some embodiments a ternary electrocatalyst is provided. The electrocatalyst can be used in an anode for oxidizing alcohol in a fuel cell. In some embodiments, the ternary electrocatalyst may include a noble metal particle having a surface decorated with clusters of SnO.sub.2 and Rh. The noble metal particles may include platinum, palladium, ruthenium, iridium, gold, and combinations thereof. In some embodiments, the ternary electrocatalyst includes SnO.sub.2 particles having a surface decorated with clusters of a noble metal and Rh. Some ternary electrocatalysts include noble metal particles with clusters of SnO.sub.2 and Rh at their surfaces. In some embodiments the electrocatalyst particle cores are nanoparticles. Some embodiments of the invention provide a fuel cell including an anode incorporating the ternary electrocatalyst. In some aspects a method of using ternary electrocatalysts of Pt, Rh, and SnO.sub.2 to oxidize an alcohol in a fuel cell is described.

  14. Electrocatalysts for oxygen electrodes. Final report

    SciTech Connect

    Yeager, E.

    1993-02-01

    Object was to understand factors controlling the activity of O{sub 2} reduction and generation electrocatalysts, in order to attain higher activity and longer-term stability. Two broad classes of catalysts were developed: transition metal macrocycles in monomeric and polymeric forms, and transition metal oxides including perovskites and pyrochlores. 20 refs., 14 figs.

  15. Recent Progress in Nanostructured Electrocatalysts for PEM Fuel Cells

    SciTech Connect

    Zhang, Sheng; Shao, Yuyan; Yin, Geping; Lin, Yuehe

    2013-03-30

    Polymer electrolyte membrane (PEM) fuel cells are attracting much attention as promising clean power sources and an alternative to conventional internal combustion engines, secondary batteries, and other power sources. Much effort from government laboratories, industry, and academia has been devoted to developing PEM fuel cells, and great advances have been achieved. Although prototype cars powered by fuel cells have been delivered, successful commercialization requires fuel cell electrocatalysts, which are crucial components at the heart of fuel cells, meet exacting performance targets. In this review, we present a brief overview of the recent progress in fuel cell electrocatalysts, which involves catalyst supports, Pt and Pt-based electrocatalysts, and non-Pt electrocatalysts.

  16. Electrocatalyst advances for hydrogen oxidation in phosphoric acid fuel cells

    NASA Technical Reports Server (NTRS)

    Stonehart, P.

    1984-01-01

    The important considerations that presently exist for achieving commercial acceptance of fuel cells are centered on cost (which translates to efficiency) and lifetime. This paper addresses the questions of electrocatalyst utilization within porous electrode structures and the preparation of low-cost noble metal electrocatalyst combinations with extreme dispersions of the metal. Now that electrocatalyst particles can be prepared with dimensions of 10 A, either singly or in alloy combinations, a very large percentage of the noble metal atoms in a crystallite are available for reaction. The cost savings for such electrocatalysts in the present commercially driven environment are considerable.

  17. Development of Molecular Electrocatalysts for Energy Storage

    SciTech Connect

    DuBois, Daniel L.

    2014-02-20

    Molecular electrocatalysts can play an important role in energy storage and utilization reactions needed for intermittent renewable energy sources. This manuscript describes three general themes that our laboratories have found useful in the development of molecular electrocatalysts for reduction of CO2 to CO and for H2 oxidation and production. The first theme involves a conceptual partitioning of catalysts into first, second, and outer coordination spheres. This is illustrated with the design of electrocatalysts for CO2 reduction to CO using first and second coordination spheres and for H2 production catalysts using all three coordination spheres. The second theme focuses on the development of thermodynamic models that can be used to design catalysts to avoid high energy and low energy intermediates. In this research, new approaches to the measurement of thermodynamic hydride donor and acceptor abilities of transition metal complexes were developed. Combining this information with other thermodynamic information such as pKa values and redox potentials led to more complete thermodynamic descriptions of transition metal hydride, dihydride, and related species. Relationships extracted from this information were then used to develop models that are powerful tools for predicting and understanding the relative free energies of intermediates in catalytic reactions. The third theme is the control of proton movement during electrochemical fuel generation and utilization reactions. This research involves the incorporation of pendant amines in the second coordination sphere that can facilitate H-H bond heterolysis and heteroformation, intramolecular and intermolecular proton transfer steps, and the coupling of proton and electron transfer steps. Studies also indicate an important role for outer coordination sphere in the delivery of protons to the second coordination sphere. Understanding these proton transfer reactions and their

  18. Fuel cell with Pt/Pd electrocatalyst electrode

    DOEpatents

    Stonehart, Paul

    1983-01-01

    An electrode for use in a phosphoric acid fuel cell comprising a graphitized or partially graphitized carbon support having a platinum/palladium electrocatalyst thereon. Preferably, the platinum/palladium catalyst comprises 20 to 65 weight percent palladium.

  19. Cathodic electrocatalyst layer for electrochemical generation of hydrogen peroxide

    NASA Technical Reports Server (NTRS)

    Rhodes, Christopher P. (Inventor); Tennakoon, Charles L. K. (Inventor); Singh, Waheguru Pal (Inventor); Anderson, Kelvin C. (Inventor)

    2011-01-01

    A cathodic gas diffusion electrode for the electrochemical production of aqueous hydrogen peroxide solutions. The cathodic gas diffusion electrode comprises an electrically conductive gas diffusion substrate and a cathodic electrocatalyst layer supported on the gas diffusion substrate. A novel cathodic electrocatalyst layer comprises a cathodic electrocatalyst, a substantially water-insoluble quaternary ammonium compound, a fluorocarbon polymer hydrophobic agent and binder, and a perfluoronated sulphonic acid polymer. An electrochemical cell using the novel cathodic electrocatalyst layer has been shown to produce an aqueous solution having between 8 and 14 weight percent hydrogen peroxide. Furthermore, such electrochemical cells have shown stable production of hydrogen peroxide solutions over 1000 hours of operation including numerous system shutdowns.

  20. PtRu/C electrocatalysts prepared using γ-irradiation

    NASA Astrophysics Data System (ADS)

    Silva, Dionísio F.; Neto, Almir Oliveira; Pino, Eddy S.; Linardi, Marcelo; Spinacé, Estevam V.

    PtRu/C electrocatalysts (carbon-supported PtRu nanoparticles) were prepared submitting water/ethylene glycol solutions containing Pt(IV) and Ru(III) ions and the carbon support to γ-irradiation. The water/ethylene glycol ratio (v/v) and the total dose (kGy) were evaluated as synthesis parameters. The electrocatalysts were characterized by energy dispersive X-ray analysis (EDX), X-ray diffraction (XRD), transmission electron microscopy (TEM) and cyclic voltammetry and tested for methanol electro-oxidation aiming fuel cell application. The obtained PtRu/C electrocatalysts were more active for methanol electro-oxidation than the commercial PtRu/C electrocatalyst at ambient temperature and the electrocatalytic activity depends on the water/ethylene glycol ratio used in the preparation.

  1. A metal-organic framework-derived bifunctional oxygen electrocatalyst

    NASA Astrophysics Data System (ADS)

    Xia, Bao Yu; Yan, Ya; Li, Nan; Wu, Hao Bin; Lou, Xiong Wen (David); Wang, Xin

    2016-01-01

    Oxygen electrocatalysis is of great importance for many energy storage and conversion technologies, including fuel cells, metal-air batteries and water electrolysis. Replacing noble metal-based electrocatalysts with highly efficient and inexpensive non-noble metal-based oxygen electrocatalysts is critical for the practical applications of these technologies. Here we report a general approach for the synthesis of hollow frameworks of nitrogen-doped carbon nanotubes derived from metal-organic frameworks, which exhibit higher electrocatalytic activity and stability for oxygen reduction and evolution than commercial Pt/C electrocatalysts. The remarkable electrochemical properties are mainly attributed to the synergistic effect from chemical compositions and the robust hollow structure composed of interconnected crystalline nitrogen-doped carbon nanotubes. The presented strategy for controlled design and synthesis of metal-organic framework-derived functional nanomaterials offers prospects in developing highly active electrocatalysts in electrochemical energy devices.

  2. Simple model to study heterogeneous electrocatalysts

    NASA Astrophysics Data System (ADS)

    Franco-Junior, Edison; Lopes, Ana Carolina G.; Suffredini, Hugo B.; Homem-de-Mello, Paula

    2015-01-01

    New electrocatalyst materials have been proposed to increase the performance of fuel cells. Experimental studies show that Pt and Pb metallic and oxide materials are quite efficient in the oxidation of alcohols and small organic molecules such as formic acid in advanced fuel cells. This work proposes a model for studying morphologically heterogeneous catalysts through quantum chemistry methods such as density functional calculations. For testing the model, we have experimentally studied the adsorption of small organic molecules, namely formic acid and methanol, on Pt and Pb electrodes. All methodologies we have tested can be employed for this kind of study, but M06 functional results correlate best with previous simulations of homogeneous catalysts and with experimental data obtained for homogeneous and heterogeneous electrodes. Our model indicates that the presence of a Pt-Pb interface is responsible for higher adsorption energies of these molecules, most likely due to the orientation of the organic molecules that should facilitate the oxidation process.

  3. Nanostructured electrocatalysts with tunable activity and selectivity

    NASA Astrophysics Data System (ADS)

    Mistry, Hemma; Varela, Ana Sofia; Kühl, Stefanie; Strasser, Peter; Cuenya, Beatriz Roldan

    2016-04-01

    The field of electrocatalysis has undergone tremendous advancement in the past few decades, in part owing to improvements in catalyst design at the nanoscale. These developments have been crucial for the realization of and improvement in alternative energy technologies based on electrochemical reactions such as fuel cells. Through the development of novel synthesis methods, characterization techniques and theoretical methods, rationally designed nanoscale electrocatalysts with tunable activity and selectivity have been achieved. This Review explores how nanostructures can be used to control electrochemical reactivity, focusing on three model reactions: O2 electroreduction, CO2 electroreduction and ethanol electrooxidation. The mechanisms behind nanoscale control of reactivity are discussed, such as the presence of low-coordinated sites or facets, strain, ligand effects and bifunctional effects in multimetallic materials. In particular, studies of how particle size, shape and composition in nanostructures can be used to tune reactivity are highlighted.

  4. Recent Advances in Electrocatalysts for Oxygen Reduction Reaction.

    PubMed

    Shao, Minhua; Chang, Qiaowan; Dodelet, Jean-Pol; Chenitz, Regis

    2016-03-23

    The recent advances in electrocatalysis for oxygen reduction reaction (ORR) for proton exchange membrane fuel cells (PEMFCs) are thoroughly reviewed. This comprehensive Review focuses on the low- and non-platinum electrocatalysts including advanced platinum alloys, core-shell structures, palladium-based catalysts, metal oxides and chalcogenides, carbon-based non-noble metal catalysts, and metal-free catalysts. The recent development of ORR electrocatalysts with novel structures and compositions is highlighted. The understandings of the correlation between the activity and the shape, size, composition, and synthesis method are summarized. For the carbon-based materials, their performance and stability in fuel cells and comparisons with those of platinum are documented. The research directions as well as perspectives on the further development of more active and less expensive electrocatalysts are provided. PMID:26886420

  5. Support materials for PEMFC and DMFC electrocatalysts-A review

    NASA Astrophysics Data System (ADS)

    Sharma, Surbhi; Pollet, Bruno G.

    2012-06-01

    Polymer electrolyte membrane fuel cells (PEMFC) and direct methanol fuel cells (DMFC) have found a wide variety of commercial applications. Their performance is essentially governed by the electrocatalyst support materials as they strongly influence the electrocatalyst performance, durability and efficiency. It is well known that carbonaceous support materials suffer from carbon corrosion (oxidation) especially at high potentials over time and thus alternative low-cost, high-performing and non-corrosive electrocatalyst support materials are urgently required. This review highlights the performance and issues associated with a variety of carbon based materials such as carbon nanotubes (CNT), carbon nanofibers (CNF), mesoporous carbon and graphene as well as non-carbonaceous based materials, e.g. titania, indium oxides, alumina, silica and tungsten oxide and carbide, ceria, zirconia nanostructures and conducting polymers catalyst support materials. Comparisons and advantages and disadvantages of the various supports are clearly described in this review.

  6. Platinum-based oxygen reduction electrocatalysts.

    PubMed

    Wu, Jianbo; Yang, Hong

    2013-08-20

    An efficient oxygen reduction reaction (ORR) offers the potential for clean energy generation in low-temperature, proton-exchange membrane fuel cells running on hydrogen fuel and air. In the past several years, researchers have developed high-performance electrocatalysts for the ORR to address the obstacles of high cost of the Pt catalyst per kilowatt of output power and of declining catalyst activity over time. Current efforts are focused on new catalyst structures that add a secondary metal to change the d-band center and the surface atomic arrangement of the catalyst, altering the chemisorption of those oxygencontaining species that have the largest impact on the ORR kinetics and improving the catalyst activity and cost effectiveness. This Account reviews recent progress in the design of Pt-based ORR electrocatalysts, including improved understanding of the reaction mechanisms and the development of synthetic methods for producing catalysts with high activity and stability. Researchers have made several types of highly active catalysts, including an extended single crystal surface of Pt and its alloy, bimetallic nanoparticles, and self-supported, low-dimensional nanostructures. We focus on the design and synthetic strategies for ORR catalysts including controlling the shape (or facet) and size of Pt and its bimetallic alloys, and controlling the surface composition and structure of core-shell, monolayer, and hollow porous structures. The strong dependence of ORR performance on facet and size suggests that synthesizing nanocrystals with large, highly reactive {111} facets could be as important, if not more important, to increasing their activity as simply making smaller nanoparticles. A newly developed carbon-monoxide (CO)-assisted reduction method produces Pt bimetallic nanoparticles with controlled facets. This CO-based approach works well to control shapes because of the selective CO binding on different, low-indexed metal surfaces. Post-treatment under

  7. Metal oxide electrocatalysts for alternative energy technologies

    NASA Astrophysics Data System (ADS)

    Pacquette, Adele Lawren

    This dissertation focuses on the development of metal oxide electrocatalysts with varying applications for alternative energy technologies. Interest in utilizing clean, renewable and sustainable sources of energy for powering the planet in the future has received much attention. This will address the growing concern of the need to reduce our dependence on fossil fuels. The facile synthesis of metal oxides from earth abundant metals was explored in this work. The electrocatalysts can be incorporated into photoelectrochemical devices, fuel cells, and other energy storage devices. The first section addresses the utilization of semiconductors that can harness solar energy for water splitting to generate hydrogen. An oxysulfide was studied in order to combine the advantageous properties of the stability of metal oxides and the visible light absorbance of metal chalcogenides. Bi 2O2S was synthesized under facile hydrothermal conditions. The band gap of Bi2O2S was smaller than that of its oxide counterpart, Bi2O3. Light absorption by Bi 2O2S was extended to the visible region (>600 nm) in comparison to Bi2O3. The formation of a composite with In 2O3 was formed in order to create a UV irradiation protective coating of the Bi2O2S. The Bi2O2S/In 2O3 composite coupled with a dye CrTPP(Cl) and cocatalysts Pt and Co3O4 was utilized for water splitting under light irradiation to generate hydrogen and oxygen. The second section focuses on improving the stability and light absorption of semiconductors by changing the shapes and morphologies. One of the limitations of semiconductor materials is that recombination of electron-hole pairs occur within the bulk of the materials instead of migration to the surface. Three-dimensional shapes, such as nanorods, can prevent this recombination in comparison to spherical particles. Hierarchical structures, such as dendrites, cubes, and multipods, were synthesized under hydrothermal conditions, in order to reduce recombination and improve

  8. Palladium-cobalt particles as oxygen-reduction electrocatalysts

    DOEpatents

    Adzic, Radoslav; Huang, Tao

    2009-12-15

    The present invention relates to palladium-cobalt particles useful as oxygen-reducing electrocatalysts. The invention also relates to oxygen-reducing cathodes and fuel cells containing these palladium-cobalt particles. The invention additionally relates to methods for the production of electrical energy by using the palladium-cobalt particles of the invention.

  9. Transforming chitosan into N-doped graphitic carbon electrocatalysts.

    PubMed

    Wu, T X; Wang, G Z; Zhang, X; Chen, C; Zhang, Y X; Zhao, H J

    2015-01-25

    Chitosan, the only alkaline polysaccharide in nature with rich nitrogen content, is used as the sole precursor to obtain N-doped graphitic carbon-based ORR electrocatalysts. The findings of this work demonstrate that cheap, plentiful and renewable biomasses can be transformed into high value functional carbon materials. PMID:25486248

  10. Synthesis and characterization of catalysts and electrocatalysts using combinatorial methods

    NASA Astrophysics Data System (ADS)

    Ramanathan, Ramnarayanan

    This thesis documents attempts at solving three problems. Bead-based parallel synthetic and screening methods based on matrix algorithms were developed. The method was applied to search for new heterogeneous catalysts for dehydrogenation of methylcyclohexane. The most powerful use of the method to date was to optimize metal adsorption and evaluate catalysts as a function of incident energy, likely to be important in the future, should availability of energy be an optimization parameter. This work also highlighted the importance of order of addition of metal salts on catalytic activity and a portion of this work resulted in a patent with UOP LLC, Desplaines, Illinois. Combinatorial methods were also investigated as a tool to search for carbon-monoxide tolerant anode electrocatalysts and methanol tolerant cathode electrocatalysts, resulting in discovery of no new electrocatalysts. A physically intuitive scaling criterion was developed to analyze all experiments on electrocatalysts, providing insight for future experiments. We attempted to solve the CO poisoning problem in polymer electrolyte fuel cells using carbon molecular sieves as a separator. This approach was unsuccessful in solving the CO poisoning problem, possibly due to the tendency of the carbon molecular sieves to concentrate CO and CO 2 in pore walls.

  11. Slow step of oxygen ionization at oxide electrocatalysts

    SciTech Connect

    Trunov, A.M.

    1987-02-01

    The authors construct a mathematical model which depicts the electrochemical behavior of an oxide powder electrocatalyst and the chemisorption and ionization of the oxygen molecule on the electrode. The model is used to construct both the anodic and cathodic polarization curves as well as assess the electrochemical reaction rate and the electron behavior.

  12. Synthesis and characterization of nanostructured palladium-based alloy electrocatalysts

    NASA Astrophysics Data System (ADS)

    Sarkar, Arindam

    Low temperature fuel cells like proton exchange membrane fuel cells (PEMFC) are expected to play a crucial role in the future hydrogen economy, especially for transportation applications. These electrochemical devices offer significantly higher efficiency compared to conventional heat engines. However, use of exotic and expensive platinum as the electrocatalyst poses serious problems for commercial viability. In this regard, there is an urgent need to develop low-platinum or non-platinum electrocatalysts with electrocatalytic activity for the oxygen reduction reaction (ORR) superior or comparable to that of platinum. This dissertation first investigates non-platinum, palladium-based alloy electrocatalysts for ORR. Particularly, Pd-M (M = Mo and W) alloys are synthesized by a novel thermal decomposition of organo-metallic precursors. The carbon-supported Pd-M (M = Mo, W) electrocatalyts are then heat treated up to 900°C in H2 atmosphere and investigated for their phase behavior. Cyclic voltammetry (CV) and rotating disk electrode (RDE) measurements reveal that the alloying of Pd with Mo or W significantly enhances the catalytic activity for ORR as well as the stability (durability) of the electrocatalysts. Additionally, both the alloy systems exhibit high tolerance to methanol, which is particularly advantageous for direct methanol fuel cells (DMFC). The dissertation then focuses on one-pot synthesis of carbon-supported multi-metallic Pt-Pd-Co nanoalloys by a rapid microwave-assisted solvothermal (MW-ST) method. The multi-metallic alloy compositions synthesized by the MW-ST method show much higher catalytic activity for ORR compared to their counterparts synthesized by the conventional borohydride reduction method. Additionally, a series of Pt encapsulated Pd-Co nanoparticle electrocatalysts are synthesized by the MW-ST method and characterized to understand their phase behavior, surface composition, and electrocatalytic activity for ORR. Finally, the dissertation

  13. Preparation and evaluation of advanced electrocatalysts for phosphoric acid fuel cells

    NASA Technical Reports Server (NTRS)

    Stonehart, P.; Baris, J.; Pagliaro, P.

    1980-01-01

    Results are presented for hydrogen oxidation and hydrogen oxidation poisoned by carbon monoxide at levels between 0 and 30%. Due to the high activities that are now being observed for our platinum based electrocatalysts, the hydrogen concentrations were reduced to 10% levels in the gas supplies. Perturbation techniques were used to determine that a mechanism for the efficient operation of our porous gas diffusion electrodes is diffusion of the carbon monoxide out of the electrode structure through the electrolyte film on the electro-catalyst. A survey of the literature on platinum group materials (PGM) was carried out so that an identification of successful electrocatalysts could be made. Two PGM electrocatalysts were prepared and performance data for hydrogen oxidation in hot phosphoric acid in the presence of high carbon monoxide concentrations showed that they matched the best platinum on carbon electrocatalysts but with an electrocatalyst cost that was half of the platinum catalyst cost.

  14. Preparation and evaluation of advanced electrocatalysts for phosphoric acid fuel cells

    NASA Technical Reports Server (NTRS)

    Stonehart, P.; Baris, J.; Hochmuth, J.; Pagliaro, P.

    1981-01-01

    Two cooperative phenomena are required the development of highly efficient porous electrocatalysts: (1) is an increase in the electrocatalytic activity of the catalyst particle; and (2) is the availability of that electrocatalyst particle for the electromechanical reaction. The two processes interact with each other so that improvements in the electrochemical activity must be coupled with improvements in the availability of the electrocatalyst for reaction. Cost effective and highly reactive electrocatalysts were developed. The utilization of the electrocatalyst particles in the porous electrode structures was analyzed. It is shown that a large percentage of the electrocatalyst in anode structures is not utilized. This low utilization translates directly into a noble metal cost penalty for the fuel cell.

  15. Preparation and evaluation of advanced electrocatalysts for phosphoric acid fuel cells

    NASA Technical Reports Server (NTRS)

    Stonehart, P.; Baris, J.; Hochmutt, J.; Pagliaro, P.

    1980-01-01

    Alloy electrocatalysts on carbon supports were developed for hydrogen oxidation in the presence of carbon monoxide. These electrocatalysts match the best platinum on carbon catalysts for performance yet cost half as much. The results demonstrate that a significant reduction in anode electrocatalyst material cost can be achieved by replacing the platinum. Since surface characterization of this catalyst is important to explain its performance, several approaches and pitfalls to the elucidation of the surface characterization are presented.

  16. Intermetallics as Novel Supports for Pt Monolayer O2 Reduction Electrocatalysts: Potential for Significantly Improving Properties

    SciTech Connect

    Ghosh, T.; Vukmirovic, M.; DiSalvo, F.J.; Adzic, R.R.

    2010-01-27

    We report on a new class of core-shell electrocatalysts for the oxygen-reduction reaction. These electrocatalysts comprise a Pt monolayer shell and ordered intermetallic compounds cores and have enhanced activity and stability compared with conventional ones. These advantages are derived from combining the unique properties of Pt monolayer catalysts (high activity, low metal content) and of the intermetallic compounds (high stability and, possibly, low price). This method holds excellent potential for creating efficient fuel cell electrocatalysts.

  17. High-surface-area, dual-function oxygen electrocatalysts for space power applications

    NASA Technical Reports Server (NTRS)

    Ham, David O.; Moniz, Gary; Taylor, E. Jennings

    1987-01-01

    The processes of hydration/dehydration and carbonation/decarbonation are investigated as an approach to provide higher surface area mixed metal oxides that are more active electrochemically. These materials are candidates for use as electrocatalysts and electrocatalyst supports for alkaline electrolyzers and fuel cells. For the case of the perovskite, LaCoO3 , higher surface areas were achieved with no change in structure and a more active oxygen electrocatalyst.

  18. Combinatorial discovery of alloy electrocatalysts for amperometric glucose sensors.

    PubMed

    Sun, Y; Buck, H; Mallouk, T E

    2001-04-01

    Combinatorial methods were used to search for active alloy electrocatalysts for use in enzyme-free amperometric glucose sensors. Electrode arrays (715-member) containing combinations of Pt, Pb, Au, Pd, and Rh were prepared and screened by converting anodic current to visible fluorescence. The most active compositions contained both Pt and Pb. Bulk quantities of catalysts with compositions corresponding to those identified in the screening experiments were prepared and characterized. The best alloy electrocatalysts catalyzed glucose oxidation at substantially more negative potentials than pure platinum in enzyme-free voltammetric measurements. They were also insensitive to potential interfering agents (ascorbic and uric acids, and 4-acetamidophenol), which are oxidized at slightly more positive potentials. Rotating disk electrode (RDE) experiments were carried out to study the catalytic mechanism. The improvement in catalytic performance was attributed to the inhibition of adsorption of oxidation products, which poison Pt electrodes. PMID:11321315

  19. Highly Efficient Oxygen Reduction Electrocatalysts based on Winged Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Cheng, Yingwen; Zhang, Hongbo; Varanasi, Chakrapani V.; Liu, Jie

    2013-11-01

    Developing electrocatalysts with both high selectivity and efficiency for the oxygen reduction reaction (ORR) is critical for several applications including fuel cells and metal-air batteries. In this work we developed high performance electrocatalysts based on unique winged carbon nanotubes. We found that the outer-walls of a special type of carbon nanotubes/nanofibers, when selectively oxidized, unzipped and exfoliated, form graphene wings strongly attached to the inner tubes. After doping with nitrogen, the winged nanotubes exhibited outstanding activity toward catalyzing the ORR through the four-electron pathway with excellent stability and methanol/carbon monoxide tolerance. While the doped graphene wings with high active site density bring remarkable catalytic activity, the inner tubes remain intact and conductive to facilitate electron transport during electrocatalysis.

  20. A Perovskite Electrocatalyst for Efficient Hydrogen Evolution Reaction.

    PubMed

    Xu, Xiaomin; Chen, Yubo; Zhou, Wei; Zhu, Zhonghua; Su, Chao; Liu, Meilin; Shao, Zongping

    2016-08-01

    Perovskite oxides are demonstrated for the first time as efficient electrocatalysts for the hydrogen evolution reaction (HER) in alkaline solutions. A-site praseodymium-doped Pr0.5 (Ba0.5 Sr0.5 )0.5 Co0.8 Fe0.2 O3- δ (Pr0.5BSCF) exhibits dramatically enhanced HER activity and stability compared to Ba0.5 Sr0.5 Co0.8 Fe0.2 O3- δ (BSCF), superior to many well-developed bulk/nanosized nonprecious electrocatalysts. The improved HER performance originates from the modified surface electronic structures and properties of Pr0.5BSCF induced by the Pr-doping. PMID:27185219

  1. Highly Efficient Oxygen Reduction Electrocatalysts based on Winged Carbon Nanotubes

    PubMed Central

    Cheng, Yingwen; Zhang, Hongbo; Varanasi, Chakrapani V.; Liu, Jie

    2013-01-01

    Developing electrocatalysts with both high selectivity and efficiency for the oxygen reduction reaction (ORR) is critical for several applications including fuel cells and metal-air batteries. In this work we developed high performance electrocatalysts based on unique winged carbon nanotubes. We found that the outer-walls of a special type of carbon nanotubes/nanofibers, when selectively oxidized, unzipped and exfoliated, form graphene wings strongly attached to the inner tubes. After doping with nitrogen, the winged nanotubes exhibited outstanding activity toward catalyzing the ORR through the four-electron pathway with excellent stability and methanol/carbon monoxide tolerance. While the doped graphene wings with high active site density bring remarkable catalytic activity, the inner tubes remain intact and conductive to facilitate electron transport during electrocatalysis. PMID:24217312

  2. Highly efficient oxygen reduction electrocatalysts based on winged carbon nanotubes.

    PubMed

    Cheng, Yingwen; Zhang, Hongbo; Varanasi, Chakrapani V; Liu, Jie

    2013-01-01

    Developing electrocatalysts with both high selectivity and efficiency for the oxygen reduction reaction (ORR) is critical for several applications including fuel cells and metal-air batteries. In this work we developed high performance electrocatalysts based on unique winged carbon nanotubes. We found that the outer-walls of a special type of carbon nanotubes/nanofibers, when selectively oxidized, unzipped and exfoliated, form graphene wings strongly attached to the inner tubes. After doping with nitrogen, the winged nanotubes exhibited outstanding activity toward catalyzing the ORR through the four-electron pathway with excellent stability and methanol/carbon monoxide tolerance. While the doped graphene wings with high active site density bring remarkable catalytic activity, the inner tubes remain intact and conductive to facilitate electron transport during electrocatalysis. PMID:24217312

  3. Preparation of supported electrocatalyst comprising multiwalled carbon nanotubes

    SciTech Connect

    Wu, Gang; Zelenay, Piotr

    2013-08-27

    A process for preparing a durable non-precious metal oxygen reduction electrocatalyst involves heat treatment of a ball-milled mixture of polyaniline and multiwalled carbon nanotubes in the presence of a Fe species. The catalyst is more durable than catalysts that use carbon black supports. Performance degradation was minimal or absent after 500 hours of operation at constant cell voltage of 0.40 V.

  4. Copper as a robust and transparent electrocatalyst for water oxidation.

    PubMed

    Du, Jialei; Chen, Zuofeng; Ye, Shengrong; Wiley, Benjamin J; Meyer, Thomas J

    2015-02-01

    Copper metal is in theory a viable oxidative electrocatalyst based on surface oxidation to Cu(III) and/or Cu(IV) , but its use in water oxidation has been impeded by anodic corrosion. The in situ formation of an efficient interfacial oxygen-evolving Cu catalyst from Cu(II) in concentrated carbonate solutions is presented. The catalyst necessitates use of dissolved Cu(II) and accesses the higher oxidation states prior to decompostion to form an active surface film, which is limited by solution conditions. This observation and restriction led to the exploration of ways to use surface-protected Cu metal as a robust electrocatalyst for water oxidation. Formation of a compact film of CuO on Cu surface prevents anodic corrosion and results in sustained catalytic water oxidation. The Cu/CuO surface stabilization was also applied to Cu nanowire films, which are transparent and flexible electrocatalysts for water oxidation and are an attractive alternative to ITO-supported catalysts for photoelectrochemical applications. PMID:25581365

  5. Nanoparticle Superlattices as Efficient Bifunctional Electrocatalysts for Water Splitting.

    PubMed

    Li, Jun; Wang, Yongcheng; Zhou, Tong; Zhang, Hui; Sun, Xuhui; Tang, Jing; Zhang, Lijuan; Al-Enizi, Abdullah M; Yang, Zhongqin; Zheng, Gengfeng

    2015-11-18

    The solar-driven water splitting process is highly attractive for alternative energy utilization, while developing efficient, earth-abundant, bifunctional catalysts for both oxygen evolution reaction and hydrogen evolution reaction has remained as a major challenge. Herein, we develop an ordered CoMnO@CN superlattice structure as an efficient bifunctional water-splitting electrocatalyst, in which uniform Co-Mn oxide (CoMnO) nanoparticles are coated with a thin, continuous nitrogen-doped carbon (CN) framework. The CoMnO nanoparticles enable optimized OER activity with effective electronic structure configuration, and the CN framework serves as an excellent HER catalyst. Importantly, the ordered superlattice structure is beneficial for enhanced reactive sites, efficient charge transfer, and structural stability. This bifunctional superlattice catalyst manifests optimized current densities and electrochemical stability in overall water splitting, outperforming most of the previously reported single- or bifunctional electrocatalysts. Combining with a silicon photovoltaic cell, this CoMnO@CN superlattice bifunctional catalyst enables unassisted solar water splitting continuously for ∼5 days with a solar-to-hydrogen conversion efficiency of ∼8.0%. Our discovery suggests that these transition metal oxide-based superlattices may serve as a unique structure modality for efficient bifunctional water splitting electrocatalysts with scale-up potentials. PMID:26496655

  6. Unusual High Oxygen Reduction Performance in All-Carbon Electrocatalysts

    PubMed Central

    Wei, Wei; Tao, Ying; Lv, Wei; Su, Fang-Yuan; Ke, Lei; Li, Jia; Wang, Da-Wei; Li, Baohua; Kang, Feiyu; Yang, Quan-Hong

    2014-01-01

    Carbon-based electrocatalysts are more durable and cost-effective than noble materials for the oxygen reduction reaction (ORR), which is an important process in energy conversion technologies. Heteroatoms are considered responsible for the excellent ORR performance in many carbon-based electrocatalysts. But whether an all-carbon electrocatalyst can effectively reduce oxygen is unknown. We subtly engineered the interfaces between planar graphene sheets and curved carbon nanotubes (G-CNT) and gained a remarkable activity/selectivity for ORR (larger current, and n = 3.86, ~93% hydroxide + ~7% peroxide). This performance is close to that of Pt; and the durability is much better than Pt. We further demonstrate the application of this G-CNT hybrid as an all-carbon cathode catalyst for lithium oxygen batteries.We speculate that the high ORR activity of this G-CNT hybrid stems from the localized charge separation at the interface of the graphene and carbon nanotube, which results from the tunneling electron transfer due to the Fermi level mismatch on the planar and curved sp2 surfaces. Our result represents a conceptual breakthrough and pioneers the new avenues towards practical all-carbon electrocatalysis. PMID:25189141

  7. Preparation and evaluation of advanced electrocatalysts for phosphoric acid fuel cells

    NASA Technical Reports Server (NTRS)

    Stonehart, P.; Baris, J.; Hochmuth, J.; Pagliaro, P.

    1981-01-01

    A number of electrocatalyst combinations were prepared and characterized. These electrocatalysts were formulated to contain platinum combined with transition metal carbide forming elements (W, Mo, V) for cathodes and platinum combined with palladium for anodes. High resolution electron microscopy was used to determine the crystallite size and dispersion of platinum-palladium alloy electrocatalysts in order to provide analytical support for the electrochemical determinations of the particle dispersions. An equation was derived which correlates palladium crystallite size with electrochemical hydrogen adsorption. Based on comparisons of electrocatalyst performances in the presence of pure hydrogen and hydrogen containing carbon monoxide, it was shown that the apparent poisoning of the electrocatalyst by carbon monoxide is influenced by the electrode structure.

  8. Electrocatalyst approaches and challenges for automotive fuel cells.

    PubMed

    Debe, Mark K

    2012-06-01

    Fuel cells powered by hydrogen from secure and renewable sources are the ideal solution for non-polluting vehicles, and extensive research and development on all aspects of this technology over the past fifteen years has delivered prototype cars with impressive performances. But taking the step towards successful commercialization requires oxygen reduction electrocatalysts--crucial components at the heart of fuel cells--that meet exacting performance targets. In addition, these catalyst systems will need to be highly durable, fault-tolerant and amenable to high-volume production with high yields and exceptional quality. Not all the catalyst approaches currently being pursued will meet those demands. PMID:22678278

  9. Noble Metal Aerogels—Synthesis, Characterization, and Application as Electrocatalysts

    PubMed Central

    2015-01-01

    Conspectus Metallic and catalytically active materials with high surface area and large porosity are a long-desired goal in both industry and academia. In this Account, we summarize the strategies for making a variety of self-supported noble metal aerogels consisting of extended metal backbone nanonetworks. We discuss their outstanding physical and chemical properties, including their three-dimensional network structure, the simple control over their composition, their large specific surface area, and their hierarchical porosity. Additionally, we show some initial results on their excellent performance as electrocatalysts combining both high catalytic activity and high durability for fuel cell reactions such as ethanol oxidation and the oxygen reduction reaction (ORR). Finally, we give some hints on the future challenges in the research area of metal aerogels. We believe that metal aerogels are a new, promising class of electrocatalysts for polymer electrolyte fuel cells (PEFCs) and will also open great opportunities for other electrochemical energy systems, catalysis, and sensors. The commercialization of PEFCs encounters three critical obstacles, viz., high cost, insufficient activity, and inadequate long-term durability. Besides others, the sluggish kinetics of the ORR and alcohol oxidation and insufficient catalyst stability are important reasons for these obstacles. Various approaches have been taken to overcome these obstacles, e.g., by controlling the catalyst particle size in an optimized range, forming multimetallic catalysts, controlling the surface compositions, shaping the catalysts into nanocrystals, and designing supportless catalysts with extended surfaces such as nanostructured thin films, nanotubes, and porous nanostructures. These efforts have produced plenty of excellent electrocatalysts, but the development of multisynergetic functional catalysts exhibiting low cost, high activity, and high durability still faces great challenges. In this

  10. High throughput screening of electrocatalysts for fuel cell applications

    NASA Astrophysics Data System (ADS)

    Prochaska, Mark; Jin, Jing; Rochefort, Dominic; Zhuang, Lin; DiSalvo, Francis J.; Abruña, Héctor D.; van Dover, R. B.

    2006-05-01

    We describe methodologies for the generation and screening of combinatorial libraries of electrocatalyst materials for fuel cell applications, generated by cosputtering of three elements onto a Si substrate coated with a Ta adhesion underlayer. Screening was carried out via a fluorescence assay as well as by scanning electrochemical microscopy. Whereas the former provided rapid qualitative screening with limited spatial resolution, the latter provided high spatial resolution. The fluorescence screening method was tested on Pt, PtBi, PtPb, and PtRu nanoparticles, while both methods were tested on a film containing a Pt-Bi-Pb ternary composition spread.

  11. Electrocatalysts for Nonaqueous Lithium–Air Batteries: Status, Challenges, and Perspective

    SciTech Connect

    Shao, Yuyan; Park, Seh Kyu; Xiao, Jie; Zhang, Jiguang; Wang, Yong; Liu, Jun

    2012-05-04

    Li-air battery has recently emerged as a potentially transformational energy storage technology for both transportation and stationary energy storage applications due to its very high specific energy. However, its practical application is currently limited by the poor power capability, poor cyclability and low energy efficiency, all of which are largely determined by interfacial reactions on oxygen electrocatalysts in air electrode. In this article, we review the fundamental understanding of oxygen electrocatalysis in nonaqueous electrolytes, the status and challenges of oxygen electrocatalysts, and provide a perspective on new electrocatalysts design and development.

  12. Metal-free carbonaceous electrocatalysts and photocatalysts for water splitting.

    PubMed

    Xu, You; Kraft, Markus; Xu, Rong

    2016-05-31

    Water splitting driven by sunlight or renewable resource-derived electricity has attracted great attention for sustainable production of hydrogen from water. Current research interest in this field is focused on the development of earth-abundant photo- or electrocatalytic materials with high activity and long-term stability for hydrogen and/or oxygen evolution reactions. Due to their unique properties and characteristics, carbon and related carbon-based materials show great potential to replace some of the existing precious metal catalysts in water splitting technology. This tutorial review summarizes the recent significant progress in the fabrication and application of metal-free carbonaceous materials as photo- or electrocatalysts for water splitting. Synthetic strategies and applications of various carbonaceous materials, including graphitic carbon nitride (g-C3N4), graphene, carbon nanotubes (CNTs) as well as other forms of carbon-containing materials, for electrochemical or photochemical water splitting are presented, accompanied by a discussion of the key scientific issues and prospects for the future development of metal-free photo- and electrocatalysts. PMID:27094875

  13. Preparation and evaluation of advanced electrocatalysts for phosphoric acid fuel cells

    NASA Technical Reports Server (NTRS)

    Stonehart, P.; Baris, J.; Hochmuth, J.; Pagliaro, P.

    1981-01-01

    The highest performance fuel cell cathode electrocatalyst combination ever observed gives 755 mV vs hydrogen at 100 ASF on air at 180 C and shows a potential improvement to 775 mV vs hydrogen for better electrode structures. A pressurized fuel cell (UTC at 5 atm) would then give 805 mV at 320 ASF and 180 C. Another activity diagnostic is the performance of this electrocatalyst on oxygen at 900 mV vs hydrogen. The value for electrocatalyst is 44 mA per milligram of platinum and is projected to reach 60 mA per milligram of platinum with improved electrode structures. Since the electrocatalyst surface area and the electrode structure are not yet optimized there is considerable room for performance enhancement beyond these values, especially at higher temperatures.

  14. Electrocatalyst for oxygen reduction with reduced platinum oxidation and dissolution rates

    SciTech Connect

    Adzic, Radoslav; Zhang, Junliang; Vukmirovic, Miomir

    2012-11-13

    The invention relates to platinum-metal oxide composite particles and their use as electrocatalysts in oxygen-reducing cathodes and fuel cells. The invention particularly relates to methods for preventing the oxidation of the platinum electrocatalyst in the cathodes of fuel cells by use of these platinum-metal oxide composite particles. The invention additionally relates to methods for producing electrical energy by supplying such a fuel cell with an oxidant, such as oxygen, and a fuel source, such as hydrogen.

  15. Electrocatalysts having gold monolayers on platinum nanoparticle cores, and uses thereof

    DOEpatents

    Adzic, Radoslav; Zhang, Junliang

    2010-04-27

    The invention relates to gold-coated particles useful as fuel cell electrocatalysts. The particles are composed of an electrocatalytically active core at least partially encapsulated by an outer shell of gold or gold alloy. The invention more particularly relates to such particles having a noble metal-containing core, and more particularly, a platinum or platinum alloy core. In other embodiments, the invention relates to fuel cells containing these electrocatalysts and methods for generating electrical energy therefrom.

  16. Electrocatalyst for oxygen reduction with reduced platinum oxidation and dissolution rates

    DOEpatents

    Adzic, Radoslav; Zhang, Junliang; Vukmirovic, Miomir

    2011-11-22

    The invention relates to platinum-metal oxide composite particles and their use as electrocatalysts in oxygen-reducing cathodes and fuel cells. The invention particularly relates to methods for preventing the oxidation of the platinum electrocatalyst in the cathodes of fuel cells by use of these platinum-metal oxide composite particles. The invention additionally relates to methods for producing electrical energy by supplying such a fuel cell with an oxidant, such as oxygen, and a fuel source, such as hydrogen.

  17. Oxygen Electrocatalysts for Water Electrolyzers and Reversible Fuel Cells: Status and Perspective

    SciTech Connect

    Park, Seh Kyu; Shao, Yuyan; Liu, Jun; Wang, Yong

    2012-11-01

    Hydrogen production by electrochemical water electrolysis has received great attention as an alternative technology for energy conversion and storage. The oxygen electrode has a substantial effect on the performance and durability in water electrolyzers and reversible fuel cells because of its intrinsically slow kinetics for oxygen evolution/reduction and poor durability under harsh operating environments. To improve oxygen kinetics and durability of the electrode, extensive studies for highly active and stable oxygen electrocatalyst have been performed. However, due to the thermodynamic instability of transition metals in acidic media, noble metal compounds have been primarily utilized as electrocatalysts in water electrolyzers and reversible fuel cells. For water electrolyzer applications, single noble metal oxides such as ruthenium oxide and iridium oxide have been studied, and binary or ternary metal oxides have been developed to take synergestic effects of each component. On the other hand, a variety of bifunctional electrocatalysts with a combination of monofunctional electrocatalysts such as platinum for oxygen reduction and iridium oxide for oxygen evolution for reversible fuel cell applications have been mainly proposed. Practically, supported iridium oxide-on-platinum, its reverse type, and non-precious metal-supported platinum and iridium bifunctional electrocatalysts have been developed. Recent theoretical calculations and experimental studies in terms of water electrolysis and fuel cell technology suggest effective ways to cope with current major challenges of cost and durability of oxygen electrocatalysts for technical applications.

  18. Bio-inspired routes for synthesizing efficient nanoscale platinum electrocatalysts

    SciTech Connect

    Cha, Jennifer N.; Wang, Joseph

    2014-08-31

    The overall objective of the proposed research is to use fundamental advances in bionanotechnology to design powerful platinum nanocrystal electrocatalysts for fuel cell applications. The new economically-viable, environmentally-friendly, bottom-up biochemical synthetic strategy will produce platinum nanocrystals with tailored size, shape and crystal orientation, hence leading to a maximum electrochemical reactivity. There are five specific aims to the proposed bio-inspired strategy for synthesizing efficient electrocatalytic platinum nanocrystals: (1) isolate peptides that both selectively bind particular crystal faces of platinum and promote the nucleation and growth of particular nanocrystal morphologies, (2) pattern nanoscale 2-dimensional arrays of platinum nucleating peptides from DNA scaffolds, (3) investigate the combined use of substrate patterned peptides and soluble peptides on nanocrystal morphology and growth (4) synthesize platinum crystals on planar and large-area carbon electrode supports, and (5) perform detailed characterization of the electrocatalytic behavior as a function of catalyst size, shape and morphology. Project Description and Impact: This bio-inspired collaborative research effort will address key challenges in designing powerful electrocatalysts for fuel cell applications by employing nucleic acid scaffolds in combination with peptides to perform specific, environmentally-friendly, simultaneous bottom-up biochemical synthesis and patterned assembly of highly uniform and efficient platinum nanocrystal catalysts. Bulk synthesis of nanoparticles usually produces a range of sizes, accessible catalytic sites, crystal morphologies, and orientations, all of which lead to inconsistent catalytic activities. In contrast, biological systems routinely demonstrate exquisite control over inorganic syntheses at neutral pH and ambient temperature and pressures. Because the orientation and arrangement of the templating biomolecules can be precisely

  19. Carbon-based electrocatalysts for advanced energy conversion and storage

    PubMed Central

    Zhang, Jintao; Xia, Zhenhai; Dai, Liming

    2015-01-01

    Oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) play curial roles in electrochemical energy conversion and storage, including fuel cells and metal-air batteries. Having rich multidimensional nanoarchitectures [for example, zero-dimensional (0D) fullerenes, 1D carbon nanotubes, 2D graphene, and 3D graphite] with tunable electronic and surface characteristics, various carbon nanomaterials have been demonstrated to act as efficient metal-free electrocatalysts for ORR and OER in fuel cells and batteries. We present a critical review on the recent advances in carbon-based metal-free catalysts for fuel cells and metal-air batteries, and discuss the perspectives and challenges in this rapidly developing field of practical significance. PMID:26601241

  20. Carbon-based electrocatalysts for advanced energy conversion and storage.

    PubMed

    Zhang, Jintao; Xia, Zhenhai; Dai, Liming

    2015-08-01

    Oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) play curial roles in electrochemical energy conversion and storage, including fuel cells and metal-air batteries. Having rich multidimensional nanoarchitectures [for example, zero-dimensional (0D) fullerenes, 1D carbon nanotubes, 2D graphene, and 3D graphite] with tunable electronic and surface characteristics, various carbon nanomaterials have been demonstrated to act as efficient metal-free electrocatalysts for ORR and OER in fuel cells and batteries. We present a critical review on the recent advances in carbon-based metal-free catalysts for fuel cells and metal-air batteries, and discuss the perspectives and challenges in this rapidly developing field of practical significance. PMID:26601241

  1. Nanostructured Electrocatalysts for All-Vanadium Redox Flow Batteries.

    PubMed

    Park, Minjoon; Ryu, Jaechan; Cho, Jaephil

    2015-10-01

    Vanadium redox reactions have been considered as a key factor affecting the energy efficiency of the all-vanadium redox flow batteries (VRFBs). This redox reaction determines the reaction kinetics of whole cells. However, poor kinetic reversibility and catalytic activity towards the V(2+)/V(3+) and VO(2+)/VO2(+) redox couples on the commonly used carbon substrate limit broader applications of VRFBs. Consequently, modified carbon substrates have been extensively investigated to improve vanadium redox reactions. In this Focus Review, recent progress on metal- and carbon-based nanomaterials as an electrocatalyst for VRFBs is discussed in detail, without the intention to provide a comprehensive review on the whole components of the system. Instead, the focus is mainly placed on the redox chemistry of vanadium ions at a surface of various metals, different dimensional carbons, nitrogen-doped carbon nanostructures, and metal-carbon composites. PMID:25899910

  2. Degradation of Bimetallic Model Electrocatalysts ___ an in situ XAS Study

    SciTech Connect

    Friebel, Daniel

    2011-06-22

    One of the major challenges in the development of clean energy fuel cells is the performance degradation of the electrocatalyst, which, apart from poisoning effects, can suffer from corrosion due to its exposure to a harsh environment under high potentials. In this communication, we demonstrate how interactions of Pt with a transition metal support affect not only, as commonly intended, the catalytic activity, but also the reactivity of Pt towards oxide formation or dissolution. We use two well-defined single-crystal model systems, Pt/Rh(111) and Pt/Au(111) and a unique x-ray spectroscopy technique with enhanced energy resolution to monitor the potential-dependent oxidation state of Pt, and find two markedly different oxidation mechanisms on the two different substrates. This information can be of great significance for future design of more active and more stable catalysts. We have studied the potential-induced degradation of Pt monolayer model electrocatalysts on Rh(111) and Au(111) single-crystal substrates. The anodic formation of Pt oxides was monitored using in situ high energy resolution fluorescence detection x-ray absorption spectroscopy (HERFD XAS). Although Pt was deposited on both substrates in a three-dimensional island growth mode, we observed remarkable differences during oxide formation that can only be understood in terms of strong Pt-substrate interactions throughout the Pt islands. Anodic polarization of Pt/Rh(111) up to +1.6 V vs. RHE (reversible hydrogen electrode) leads to formation an incompletely oxidized passive layer, whereas formation of PtO2 and partial Pt dissolution is observed for Pt/Au(111).

  3. Correcting for electrocatalyst desorption and inactivation in chronoamperometry experiments.

    PubMed

    Fourmond, Vincent; Lautier, Thomas; Baffert, Carole; Leroux, Fanny; Liebgott, Pierre-Pol; Dementin, Sébastien; Rousset, Marc; Arnoux, Pascal; Pignol, David; Meynial-Salles, Isabelle; Soucaille, Phillippe; Bertrand, Patrick; Léger, Christophe

    2009-04-15

    Chronoamperometric experiments with adsorbed electrocatalysts are commonly performed either for analytical purposes or for studying the catalytic mechanism of a redox enzyme. In the context of amperometric sensors, the current may be recorded as a function of time while the analyte concentration is being increased to determine a linearity range. In mechanistic studies of redox enzymes, chronoamperometry proved powerful for untangling the effects of electrode potential and time, which are convoluted in cyclic voltammetric measurements, and for studying the energetics and kinetics of inhibition. In all such experiments, the fact that the catalyst's coverage and/or activity decreases over time distorts the data. This may hide meaningful features, introduce systematic errors, and limit the accuracy of the measurements. We propose a general and surprisingly simple method for correcting for electrocatalyst desorption and inactivation, which greatly increases the precision of chronoamperometric experiments. Rather than subtracting a baseline, this consists in dividing the current, either by a synthetic signal that is proportional to the instant electroactive coverage or by the signal recorded in a control experiment. In the latter, the change in current may result from film loss only or from film loss plus catalyst inactivation. We describe the different strategies for obtaining the control signal by analyzing various data recorded with adsorbed redox enzymes: nitrate reductase, NiFe hydrogenase, and FeFe hydrogenase. In each case we discuss the trustfulness and the benefit of the correction. This method also applies to experiments where electron transfer is mediated, rather than direct, providing the current is proportional to the time-dependent concentration of catalyst. PMID:19298055

  4. Palladium Monolayer and Palladium Alloy Electrocatalysts for Oxygen Reduction

    SciTech Connect

    Shao,M.; Huang, T.; Liu, P.; Zhang, J.; Sasaki, K.; Vukmirovic, M.; Adzic, R.

    2006-01-01

    We investigated the oxygen-reduction reaction (ORR) on Pd monolayers on various surfaces and on Pd alloys to obtain a substitute for Pt and to elucidate the origin of their activity. The activity of Pd monolayers supported on Ru(0001), Rh(111), Ir(111), Pt(111), and Au(111) increased in the following order: Pd/Ru(0001) < Pd/Ir(111) < Pd/Rh(111) < Pd/Au(111) < Pd/Pt(111). Their activity was correlated with their d-band centers, which were calculated using density functional theory (DFT). We found a volcano-type dependence of activity on the energy of the d-band center of Pd monolayers, with Pd/Pt(111) at the top of the curve. The activity of the non-Pt Pd{sub 2}Co/C alloy electrocatalyst nanoparticles that we synthesized was comparable to that of commercial Pt-containing catalysts. The kinetics of the ORR on this electrocatalyst predominantly involves a four-electron step reduction with the first electron transfer being the rate-determining step. The downshift of the d-band center of the Pd 'skin', which constitutes the alloy surface due to the strong surface segregation of Pd at elevated temperatures, determined its high ORR activity. Additionally, it showed very high methanol tolerance, retaining very high catalytic activity for the ORR at high concentrations of methanol. Provided its stability is satisfactory, this catalyst might possibly replace Pt in fuel-cell cathodes, especially those of direct methanol oxidation fuel cells (DMFCs).

  5. A class of high performance metal-free oxygen reduction electrocatalysts based on cheap carbon blacks.

    PubMed

    Sun, Xiujuan; Song, Ping; Zhang, Yuwei; Liu, Changpeng; Xu, Weilin; Xing, Wei

    2013-01-01

    For the goal of practical industrial development of fuel cells, cheap, sustainable and high performance electrocatalysts for oxygen reduction reactions (ORR) which rival those based on platinum (Pt) and other rare materials are highly desirable. In this work, we report a class of cheap and high-performance metal-free oxygen reduction electrocatalysts obtained by co-doping carbon blacks with nitrogen and fluorine (CB-NF).The CB-NF electrocatalysts are highly active and exhibit long-term operation stability and tolerance to poisons during oxygen reduction process in alkaline medium. The alkaline direct methanol fuel cell with the best CB-NF as cathode (3 mg/cm(2)) outperforms the one with commercial platinum-based cathode (3 mg Pt/cm(2)). To the best of our knowledge, these are among the most efficient non-Pt based electrocatalysts. Since carbon blacks are 10,000 times cheaper than Pt, these CB-NF electrocatalysts possess the best price/performance ratio for ORR, and are the most promising alternatives to Pt-based ones to date. PMID:23974295

  6. Efficient ceramic anodes infiltrated with binary and ternary electrocatalysts for SOFCs operating at low temperatures

    NASA Astrophysics Data System (ADS)

    Hussain, A. Mohammed; Høgh, Jens V. T.; Zhang, Wei; Bonanos, Nikolaos

    2012-10-01

    Electrocatalyst precursor of various combinations: Pt, Ru, Pd, Ni and Gd-doped CeO2 (CGO) were infiltrated into a porous Sr0.94Ti0.9Nb0.1O3 (STN) backbone, to study the electrode performance of infiltrated ceramic anodes at low temperature ranges of 400-600 °C. The performance of the binary electrocatalyst infiltrated ceramic backbones are Pt-CGO>Ru-CGO>Pd-CGO>Ni-CGO. Ternary electrocatalyst of Ni-Pd-CGO and Ni-Pt-CGO showed the lowest polarization resistance of 0.31 and 0.11 Ωcm2, respectively at 600 °C in H2/3% H2O. The average particle size of the ternary electrocatalyst was larger than the binary Pd-CGO and Pt-CGO due to the particle coarsening of Ni nanoparticles. High resolution transmission electron microscopic analysis on the best performing Ni-Pt-CGO electrocatalyst infiltrated anode reveals the formation of Ni-Pt nanocrystalline alloy and a homogenous distribution of nanoparticles on STN backbone.

  7. Reversible adapting layer produces robust single-crystal electrocatalyst for oxygen evolution

    NASA Astrophysics Data System (ADS)

    Tung, Ching-Wei; Hsu, Ying-Ya; Shen, Yen-Ping; Zheng, Yixin; Chan, Ting-Shan; Sheu, Hwo-Shuenn; Cheng, Yuan-Chung; Chen, Hao Ming

    2015-08-01

    Electrochemically converting water into oxygen/hydrogen gas is ideal for high-density renewable energy storage in which robust electrocatalysts for efficient oxygen evolution play crucial roles. To date, however, electrocatalysts with long-term stability have remained elusive. Here we report that single-crystal Co3O4 nanocube underlay with a thin CoO layer results in a high-performance and high-stability electrocatalyst in oxygen evolution reaction. An in situ X-ray diffraction method is developed to observe a strong correlation between the initialization of the oxygen evolution and the formation of active metal oxyhydroxide phase. The lattice of skin layer adapts to the structure of the active phase, which enables a reversible facile structural change that facilitates the chemical reactions without breaking the scaffold of the electrocatalysts. The single-crystal nanocube electrode exhibits stable, continuous oxygen evolution for >1,000 h. This robust stability is attributed to the complementary nature of defect-free single-crystal electrocatalyst and the reversible adapting layer.

  8. Reversible adapting layer produces robust single-crystal electrocatalyst for oxygen evolution

    PubMed Central

    Tung, Ching-Wei; Hsu, Ying-Ya; Shen, Yen-Ping; Zheng, Yixin; Chan, Ting-Shan; Sheu, Hwo-Shuenn; Cheng, Yuan-Chung; Chen, Hao Ming

    2015-01-01

    Electrochemically converting water into oxygen/hydrogen gas is ideal for high-density renewable energy storage in which robust electrocatalysts for efficient oxygen evolution play crucial roles. To date, however, electrocatalysts with long-term stability have remained elusive. Here we report that single-crystal Co3O4 nanocube underlay with a thin CoO layer results in a high-performance and high-stability electrocatalyst in oxygen evolution reaction. An in situ X-ray diffraction method is developed to observe a strong correlation between the initialization of the oxygen evolution and the formation of active metal oxyhydroxide phase. The lattice of skin layer adapts to the structure of the active phase, which enables a reversible facile structural change that facilitates the chemical reactions without breaking the scaffold of the electrocatalysts. The single-crystal nanocube electrode exhibits stable, continuous oxygen evolution for >1,000 h. This robust stability is attributed to the complementary nature of defect-free single-crystal electrocatalyst and the reversible adapting layer. PMID:26315066

  9. A Class of High Performance Metal-Free Oxygen Reduction Electrocatalysts based on Cheap Carbon Blacks

    NASA Astrophysics Data System (ADS)

    Sun, Xiujuan; Song, Ping; Zhang, Yuwei; Liu, Changpeng; Xu, Weilin; Xing, Wei

    2013-08-01

    For the goal of practical industrial development of fuel cells, cheap, sustainable and high performance electrocatalysts for oxygen reduction reactions (ORR) which rival those based on platinum (Pt) and other rare materials are highly desirable. In this work, we report a class of cheap and high-performance metal-free oxygen reduction electrocatalysts obtained by co-doping carbon blacks with nitrogen and fluorine (CB-NF).The CB-NF electrocatalysts are highly active and exhibit long-term operation stability and tolerance to poisons during oxygen reduction process in alkaline medium. The alkaline direct methanol fuel cell with the best CB-NF as cathode (3 mg/cm2) outperforms the one with commercial platinum-based cathode (3 mg Pt/cm2). To the best of our knowledge, these are among the most efficient non-Pt based electrocatalysts. Since carbon blacks are 10,000 times cheaper than Pt, these CB-NF electrocatalysts possess the best price/performance ratio for ORR, and are the most promising alternatives to Pt-based ones to date.

  10. Effect of anode electrocatalyst for direct hydrazine fuel cell using proton exchange membrane

    NASA Astrophysics Data System (ADS)

    Yamada, Koji; Yasuda, Kazuaki; Tanaka, Hirohisa; Miyazaki, Yoshinori; Kobayashi, Tetsuhiko

    Hydrazine was examined as a fuel in a direct-liquid-fueled fuel cell that uses proton exchange membrane (PEM) such as Nafion ®. Different kinds of noble metals were examined as anode electrocatalysts for direct hydrazine fuel cells (DHFCs). In DHFC using platinum or palladium as the anode electrocatalyst, more than 1 V of cell voltage was obtained in the low-current density region. The I- V characteristics changed drastically depending on the kind of anode electrocatalyst used. Compositions of the exhaust materials from each electrode were analyzed to investigate the reaction occurring at the electrodes. The analysis revealed that the catalytic decomposition reaction of hydrazine proceeded further than the electro-oxidation reaction on the anode side using rhodium or ruthenium.

  11. Recent Advances in Platinum Monolayer Electrocatalysts for Oxygen Reduction Reaction: Scale-up Synthesis Structure and Activity of Pt Shells on Pd Cores

    SciTech Connect

    Sasaki K.; Wang J.X.; Naohara H.; Marinkovic N.; More K.; Inada H.; Adzic R.R.

    2010-03-01

    We have established a scale-up synthesis method to produce gram-quantities of Pt monolayer electrocatalysts. The core-shell structure of the Pt/Pd/C electrocatalyst has been verified using the HAADF-STEM Z-contrast images, STEM/EELS, and STEM/EDS line profile analysis. The atomic structure of this electrocatalyst and formation of a Pt monolayer on Pd nanoparticle surfaces were examined using in situ EXAFS. The Pt mass activity of the Pt/Pd/C electrocatalyst for ORR is considerably higher than that of commercial Pt/C electrocatalysts. The results with Pt monolayer electrocatalysts may significantly impact science of electrocatalysis and fuel-cell technology, as they have demonstrated an exceptionally effective way of using Pt that can resolve problems of other approaches, including electrocatalysts inadequate activity and high Pt content.

  12. Palladium modified gold nanoparticles as electrocatalysts for ethanol electrooxidation

    NASA Astrophysics Data System (ADS)

    Chen, Huimei; Xing, Zelong; Zhu, Shangqiang; Zhang, Lulu; Chang, Qiaowan; Huang, Jiale; Cai, Wen-Bin; Kang, Ning; Zhong, Chuan-Jian; Shao, Minhua

    2016-07-01

    Resemblin, g core-shell electrocatalysts consisting of a Au core and Pd shell (Au@Pd) are synthesized via a Cu underpotential deposition (UPD)-Pd-displacement method. The Pd shell is non-uniform consisting of tiny Pd clusters with a coverage of 0.5-0.6. The ethanol oxidation reaction (EOR) activity of this kind of structure is much higher than Pd/C in an alkaline solution. The forward peak current density of Au@Pd is 5.4 times higher than that of Pd/C. Furthermore, the onset potential for EOR of the former is ∼100 mV more negative. An interesting particle size dependent EOR activity is also observed. With increasing the Au particle size (2.9, 5.8 and 6.5 nm), the EOR activity increases. The strain and ligand effects from the Au core, together with the bifunctional reaction mechanism in the Au-Pd system may be reasons for the enhanced activity in Au@Pd catalysts.

  13. A soluble copper-bipyridine water-oxidation electrocatalyst

    NASA Astrophysics Data System (ADS)

    Barnett, Shoshanna M.; Goldberg, Karen I.; Mayer, James M.

    2012-06-01

    The oxidation of water to O2 is a key challenge in the production of chemical fuels from electricity. Although several catalysts have been developed for this reaction, substantial challenges remain towards the ultimate goal of an efficient, inexpensive and robust electrocatalyst. Reported here is the first copper-based catalyst for electrolytic water oxidation. Copper-bipyridine-hydroxo complexes rapidly form in situ from simple commercially available copper salts and bipyridine at high pH. Cyclic voltammetry of these solutions at pH 11.8-13.3 shows large, irreversible currents, indicative of catalysis. The production of O2 is demonstrated both electrochemically and with a fluorescence probe. Catalysis occurs at about 750 mV overpotential. Electrochemical, electron paramagnetic resonance and other studies indicate that the catalyst is a soluble molecular species, that the dominant species in the catalytically active solutions is (2,2‧-bipyridine)Cu(OH)2 and that this is among the most rapid homogeneous water-oxidation catalysts, with a turnover frequency of ~100 s-1.

  14. Pt/Pd electrocatalyst electrons for fuel cells

    DOEpatents

    Stonehart, P.

    1981-11-03

    This invention relates to improved electrochemical cells and to novel electrodes for use therein. In particular, the present invention comprises a fuel cell used primarily for the consumption of impure hydrogen fuels containing carbon monoxide or carbonaceous fuels where the electrode in contact with the fuel is not substantially poisoned by carbon monoxide. The anode of the fuel cell comprises a Pd/Pt alloy supported on a graphitized or partially graphitized carbon material. Fuel cells which comprise as essential elements a fuel electrode, an oxidizing electrode, and an electrolyte between said electrodes are devices for the direct production of electricity through the electrochemical combustion of a fuel and oxidant. These devices are recognized for their high efficiency as energy conversion units, since unlike conventional combustion engines, they are not subject to the limitations of the Carnot heat cycle. It is the primary object of the present invention to provide an electrode having high electrochemical activity for an electrochemical cell. It is another object of the present invention to provide an electrode having an electro-catalyst which is highly resistant to the corrosive environment of an electrochemical cell.

  15. Combinatorial search for oxygen reduction reaction electrocatalysts: A review

    NASA Astrophysics Data System (ADS)

    Jeon, Min Ku; Lee, Chang Hwa; Park, Geun Il; Kang, Kweon Ho

    2012-10-01

    Oxygen reduction reaction (ORR) is one of the most interesting research issues in the academia and industries due to its importance in polymer electrolyte membrane fuel cells. Development of new ORR catalysts with low cost and high activity is under intensive research, but it is a time-consuming process because of wide range of alloys to be explored. Combinatorial synthesis and high-throughput screening techniques were suggested as new experimental approaches to accelerate the ORR electrocatalyst research. The combinatorial method is focused on the synthesis of concentrated arrays and quick evaluation of the arrays via various screening techniques. In this report, the combinatorial approaches for the ORR catalyst research were reviewed based on the screening methods. Four screening techniques of optical screening, scanning electrochemical microscopy, multielectrode half cell, and multielectrode full cell were introduced as the representative ones. Other approaches were also briefly introduced. Merits and limitations of each method were discussed and representative research results of each method were shown in detail.

  16. An NMR determination of CO diffusion on platinum electrocatalysts.

    PubMed

    Kobayashi, Takeshi; Babu, Panakkattu K; Gancs, Lajos; Chung, Jong Ho; Oldfield, Eric; Wieckowski, Andrzej

    2005-10-19

    We report the first direct measurement of CO diffusion on nanoparticle Pt electrocatalysts at the solid/liquid interface, carried out using 13C nuclear magnetic resonance (NMR) with a spin-labeling pulse sequence. Diffusion parameters were measured in the temperature range of 253-293 K for CO adsorbed on commercial Pt-black under saturation coverage. 2H NMR of the same system indicates that the electrolyte remains in the liquid state at temperatures where the CO diffusion experiments were performed. The CO diffusion parameters follow typical Arrhenius behavior with an activation energy of 6.0 +/- 0.4 kcal/mol and a pre-exponential factor of (1.1 +/- 0.6) x 10-8 cm2/s. Exchange between different CO populations, driven by a chemical potential gradient, is suggested to be the main mechanism for CO diffusion. The presence of the electrolyte medium considerably slows down the diffusion of CO as compared to that seen on surfaces of bulk metals under UHV conditions. This work opens up a new approach to the study of surface diffusion of adsorbed molecules on nanoparticle electrode catalysts, including the possibility of correlating diffusion parameters to catalytic activity in real world applications of broad general interest. PMID:16218593

  17. An efficient bifunctional electrocatalyst for water splitting based on cobalt phosphide

    NASA Astrophysics Data System (ADS)

    Yang, Libin; Qi, Honglan; Zhang, Chengxiao; Sun, Xuping

    2016-06-01

    The development of highly efficient electrocatalysts for water splitting is critical for various renewable-energy technologies. In this letter, we demonstrate a cobalt phosphide nanowire array grown on a Ti mesh (CoP/TM) behaving as a bifunctional electrocatalyst for water splitting. The CoP/TM electrode delivers 10 mA cm‑2 at an overpotential of 72 mV for the hydrogen evolution reaction (HER) and 310 mV for the oxygen evolution reaction (OER) in 1.0 M KOH. Furthermore, its corresponding two-electrode alkaline electrolyzer displays 10 mA cm‑2 at 1.64 V.

  18. Carbon monoxide tolerant electrocatalyst with low platinum loading and a process for its preparation

    DOEpatents

    Adzic, Radoslav; Brankovic, Stanko; Wang, Jia

    2003-12-30

    An electrocatalyst is provided for use in a fuel cell that has low platinum loading and a high tolerance to carbon monoxide poisoning. The fuel cell anode includes an electrocatalyst that has a conductive support material, ruthenium nanoparticles reduced in H.sub.2 and a Group VIII noble metal in an amount of between about 0.1 and 25 wt % of the ruthenium nanoparticles, preferably between about 0.5 and 15 wt %. The preferred Group VIII noble metal is platinum. In one embodiment, the anode can also have a perfluorinated polymer membrane on its surface.

  19. Hydrogen Economy: The Role of Nano-scaled Support Material for Electrocatalysts Aimed for Water Electrolysis

    NASA Astrophysics Data System (ADS)

    Paunović, Perica; Popovski, Orce; Dimitrov, Aleksandar T.

    The role and importance of support materials for electrocatalysts aimed for water electrolysis is given. Besides their superior support characteristics such as electroconductivity, a high developed surface area and chemical stability, support materials should be an active participant in the catalytic activity through strong metal-support interactions (SMSI) with the metallic catalytic phase. Subject of this paper are several support materials: (i) Vulcan XC-72, (ii) Vulcan XC-72 with TiO2, (iii) multiwalled carbon nanotubes (MWCNTs) and (iv) Magneli phases, i.e. nonstoichiometric titanium oxides. A comparison of catalytic activity of Co-based electrocatalysts deposited on all support materials mentioned is given.

  20. Structure-activity relationship in high-performance iron-based electrocatalysts for oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Song, Ping; Wang, Ying; Pan, Jing; Xu, Weilin; Zhuang, Lin

    2015-12-01

    A sustainable Iron (Fe), Nitrogen (N) co-doped high performance Fe-Nx/C electrocatalyst for oxygen reduction reaction (ORR) is synthesized simply based on nitric acid oxidation of cheap carbon black. The obtained optimal nonprecious metal electrocatalyst shows high ORR performance in both alkaline and acidic conditions and possesses appreciable performance/price ratio due to its low cost. Furthermore, the structure-activity relationship of different active sites on Fe-Nx/C is revealed systematically: Fe-N4/2-C > Fe4-N-C > N-C >> Fe4-C ≥ C, from both experimental and theoretical points of view.

  1. An efficient bifunctional electrocatalyst for water splitting based on cobalt phosphide.

    PubMed

    Yang, Libin; Qi, Honglan; Zhang, Chengxiao; Sun, Xuping

    2016-06-10

    The development of highly efficient electrocatalysts for water splitting is critical for various renewable-energy technologies. In this letter, we demonstrate a cobalt phosphide nanowire array grown on a Ti mesh (CoP/TM) behaving as a bifunctional electrocatalyst for water splitting. The CoP/TM electrode delivers 10 mA cm(-2) at an overpotential of 72 mV for the hydrogen evolution reaction (HER) and 310 mV for the oxygen evolution reaction (OER) in 1.0 M KOH. Furthermore, its corresponding two-electrode alkaline electrolyzer displays 10 mA cm(-2) at 1.64 V. PMID:27146428

  2. Highly efficient and durable TiN nanofiber electrocatalyst supports

    NASA Astrophysics Data System (ADS)

    Kim, Hyun; Cho, Min Kyung; Kwon, Jeong An; Jeong, Yeon Hun; Lee, Kyung Jin; Kim, Na Young; Kim, Min Jung; Yoo, Sung Jong; Jang, Jong Hyun; Kim, Hyoung-Juhn; Nam, Suk Woo; Lim, Dong-Hee; Cho, Eunae; Lee, Kwan-Young; Kim, Jin Young

    2015-11-01

    To date, carbon-based materials including various carbon nanostructured materials have been extensively used as an electrocatalyst support for proton exchange membrane fuel cell (PEMFC) applications due to their practical nature. However, carbon dissolution or corrosion caused by high electrode potential in the presence of O2 and/or water has been identified as one of the main failure modes for the device operation. Here, we report the first TiN nanofiber (TNF)-based nonwoven structured materials to be constructed via electrospinning and subsequent two-step thermal treatment processes as a support for the PEMFC catalyst. Pt catalyst nanoparticles (NPs) deposited on the TNFs (Pt/TNFs) were electrochemically characterized with respect to oxygen reduction reaction (ORR) activity and durability in an acidic medium. From the electrochemical tests, the TNF-supported Pt catalyst was better and more stable in terms of its catalytic performance compared to a commercially available carbon-supported Pt catalyst. For example, the initial oxygen reduction performance was comparable for both cases, while the Pt/TNF showed much higher durability from an accelerated degradation test (ADT) configuration. It is understood that the improved catalytic roles of TNFs on the supported Pt NPs for ORR are due to the high electrical conductivity arising from the extended connectivity, high inertness to the electrochemical environment and strong catalyst-support interactions.To date, carbon-based materials including various carbon nanostructured materials have been extensively used as an electrocatalyst support for proton exchange membrane fuel cell (PEMFC) applications due to their practical nature. However, carbon dissolution or corrosion caused by high electrode potential in the presence of O2 and/or water has been identified as one of the main failure modes for the device operation. Here, we report the first TiN nanofiber (TNF)-based nonwoven structured materials to be constructed via

  3. Manganese-Based Molecular Electrocatalysts for Oxidation of Hydrogen

    SciTech Connect

    Hulley, Elliott; Kumar, Neeraj; Raugei, Simone; Bullock, R. Morris

    2015-10-05

    Oxidation of H2 (1 atm) is catalyzed by the manganese electrocatalysts [(P2N2)MnI(CO)(bppm)]+ and [(PNP)MnI(CO)(bppm)]+ (P2N2= 1,5-dibenzyl-3,7-diphenyl-1,5-diaza-3,7-diphosphacyclooctane; PNP = (Ph2PCH2)2NMe); bppm = (PArF2)2CH2, and ArF = 3,5-(CF3)2C6H3). In fluorobenzene solvent using 2,6-lutidine as the exogeneous base, the turnover frequency for [(P2N2)MnI(CO)(bppm)]+ is 3.5 s-1 with an estimated overpotential of 590 mV. For [(PNP)MnI(CO)(bppm)], in fluorobenzene solvent using N-methylpyrrolidine as the exogeneous base, the turnover frequency is 1.4 s-1 with an estimated overpotential of 700 mV. Density functional theory calculations suggest that the slow step in the catalytic cycle is proton transfer from the oxidized 17-electron manganese hydride, e.g., [(P2N2)MnIIH(CO)(bppm)]+ to the pendant amine. The computed activation barrier for intramolecular proton transfer from the metal to the pendant amine is 20.4 kcal/mol in [(P2N2)MnIIH(CO)(bppm)]+ and 21.3 kcal/mol in [(PNP)MnI(CO)(bppm)]. The high barrier appears to result from both the unfavorability of metal-to-nitrogen proton transfer (thermodynamically uphill by 6.6 pKa units, 9 kcal/mol), as well as the relatively long manganese-nitrogen separation in the MnIIH complexes.

  4. Significant Enhancement of Water Splitting Activity of N-Carbon Electrocatalyst by Trace Level Co Doping.

    PubMed

    Bayatsarmadi, Bita; Zheng, Yao; Tang, Youhong; Jaroniec, Mietek; Qiao, Shi-Zhang

    2016-07-01

    Replacement of precious metal electrocatalysts with highly active and cost efficient alternatives for complete water splitting at low voltage has attracted a growing attention in recent years. Here, this study reports a carbon-based composite co-doped with nitrogen and trace amount of metallic cobalt (1 at%) as a bifunctional electrocatalyst for water splitting at low overpotential and high current density. An excellent electrochemical activity of the newly developed electrocatalyst originates from its graphitic nanostructure and highly active Co-Nx sites. In the case of carefully optimized sample of this electrocatalyst, 10 mA cm(-2) current density can be achieved for two half reactions in alkaline solutions-hydrogen evolution reaction and oxygen evolution reaction-at low overpotentials of 220 and 350 mV, respectively, which are smaller than those previously reported for nonprecious metal and metal-free counterparts. Based on the spectroscopic and electrochemical investigations, the newly identified Co-Nx sites in the carbon framework are responsible for high electrocatalytic activity of the Co,N-doped carbon. This study indicates that a trace level of the introduced Co into N-doped carbon can significantly enhance its electrocatalytic activity toward water splitting. PMID:27246288

  5. Bimetallic nanowires as electrocatalysts for nonenzymatic real-time impedancimetric detection of glucose.

    PubMed

    Mayorga-Martinez, Carmen C; Guix, Maria; Madrid, Rossana E; Merkoçi, Arben

    2012-02-01

    Gold-platinum nanowires are proposed as electrocatalysts for a real-time nonenzymatic impedancimetric detection of glucose. The electrochemical behavior of the obtained platform toward electrocatalytic oxidation of glucose, including a proposal for the detection mechanism, is shown. PMID:22183014

  6. Noble metal-free bifunctional oxygen evolution and oxygen reduction acidic media electro-catalysts.

    PubMed

    Patel, Prasad Prakash; Datta, Moni Kanchan; Velikokhatnyi, Oleg I; Kuruba, Ramalinga; Damodaran, Krishnan; Jampani, Prashanth; Gattu, Bharat; Shanthi, Pavithra Murugavel; Damle, Sameer S; Kumta, Prashant N

    2016-01-01

    Identification of low cost, highly active, durable completely noble metal-free electro-catalyst for oxygen reduction reaction (ORR) in proton exchange membrane (PEM) fuel cells, oxygen evolution reaction (OER) in PEM based water electrolysis and metal air batteries remains one of the major unfulfilled scientific and technological challenges of PEM based acid mediated electro-catalysts. In contrast, several non-noble metals based electro-catalysts have been identified for alkaline and neutral medium water electrolysis and fuel cells. Herein we report for the very first time, F doped Cu1.5Mn1.5O4, identified by exploiting theoretical first principles calculations for ORR and OER in PEM based systems. The identified novel noble metal-free electro-catalyst showed similar onset potential (1.43 V for OER and 1 V for ORR vs RHE) to that of IrO2 and Pt/C, respectively. The system also displayed excellent electrochemical activity comparable to IrO2 for OER and Pt/C for ORR, respectively, along with remarkable long term stability for 6000 cycles in acidic media validating theory, while also displaying superior methanol tolerance and yielding recommended power densities in full cell configurations. PMID:27380719

  7. Core-Protected Platinum Monolayer Shell High-Stability Electrocatalysts for Fuel-Cell Cathodes

    SciTech Connect

    K Sasaki; H Naohara; Y Cai; Y Choi; P Liu; M Vukmirovic; J Wang; R Adzic

    2011-12-31

    Platinum monolayers can act as shells for palladium nanoparticles to lead to electrocatalysts with high activities and an ultralow platinum content, but high platinum utilization. The stability derives from the core protecting the shell from dissolution. In fuel-cell tests, no loss of platinum was observed in 200,000 potential cycles, whereas loss of palladium was significant.

  8. Core-Protected Platinum Monolayer Shell High-Stability Electrocatalysts for Fuel-Cell Cathodes

    SciTech Connect

    Adzic, R.R.; Sasaki, K.; Naohara, H.; Cai, Y.; Choi, Y.M.; Liu, P.; Vukmirovic, M.B.; Wang, J.X.

    2010-11-08

    More than skin deep: Platinum monolayers can act as shells for palladium nanoparticles to lead to electrocatalysts with high activities and an ultralow platinum content, but high platinum utilization. The stability derives from the core protecting the shell from dissolution. In fuel-cell tests, no loss of platinum was observed in 200?000 potential cycles, whereas loss of palladium was significant.

  9. Noble metal-free bifunctional oxygen evolution and oxygen reduction acidic media electro-catalysts

    DOE PAGESBeta

    Patel, Prasad Prakash; Datta, Moni Kanchan; Velikokhatnyi, Oleg I.; Kuruba, Ramalinga; Damodaran, Krishnan; Jampani, Prashanth; Gattu, Bharat; Shanthi, Pavithra Murugavel; Damle, Sameer S.; Kumta, Prashant N.

    2016-07-06

    We report that identification of low cost, highly active, durable completely noble metal-free electro-catalyst for oxygen reduction reaction (ORR) in proton exchange membrane (PEM) fuel cells, oxygen evolution reaction (OER) in PEM based water electrolysis and metal air batteries remains one of the major unfulfilled scientific and technological challenges of PEM based acid mediated electro-catalysts. In contrast, several non-noble metals based electro-catalysts have been identified for alkaline and neutral medium water electrolysis and fuel cells. Furthermore, we report for the very first time, F doped Cu1.5Mn1.5O4, identified by exploiting theoretical first principles calculations for ORR and OER in PEM basedmore » systems. The identified novel noble metal-free electro-catalyst showed similar onset potential (1.43 V for OER and 1 V for ORR vs RHE) to that of IrO2 and Pt/C, respectively. The system also displayed excellent electrochemical activity comparable to IrO2 for OER and Pt/C for ORR, respectively, along with remarkable long term stability for 6000 cycles in acidic media validating theory, while also displaying superior methanol tolerance and yielding recommended power densities in full cell configurations.« less

  10. A highly durable fuel cell electrocatalyst based on double-polymer-coated carbon nanotubes

    PubMed Central

    Berber, Mohamed R.; Hafez, Inas H.; Fujigaya, Tsuyohiko; Nakashima, Naotoshi

    2015-01-01

    Driven by the demand for the commercialization of fuel cell (FC) technology, we describe the design and fabrication of a highly durable FC electrocatalyst based on double-polymer-coated carbon nanotubes for use in polymer electrolyte membrane fuel cells. The fabricated electrocatalyst is composed of Pt-deposited polybenzimidazole-coated carbon nanotubes, which are further coated with Nafion. By using this electrocatalyst, a high FC performance with a power density of 375 mW/cm2 (at 70 ˚C, 50% relative humidity using air (cathode)/H2(anode)) was obtained, and a remarkable durability of 500,000 accelerated potential cycles was recorded with only a 5% loss of the initial FC potential and 20% loss of the maximum power density, which were far superior properties compared to those of the membrane electrode assembly prepared using carbon black in place of the carbon nanotubes. The present study indicates that the prepared highly durable fuel cell electrocatalyst is a promising material for the next generation of PEMFCs. PMID:26594045

  11. Porous MoO2 Nanosheets as Non-noble Bifunctional Electrocatalysts for Overall Water Splitting.

    PubMed

    Jin, Yanshuo; Wang, Haotian; Li, Junjie; Yue, Xin; Han, Yujie; Shen, Pei Kang; Cui, Yi

    2016-05-01

    A porous MoO2 nanosheet as an active and stable bifunctional electrocatalyst for overall water splitting, is presented. It needs a cell voltage of only about 1.53 V to achieve a current density of 10 mA cm(-2) and maintains its activity for at least 24 h in a two-electrode configuration. PMID:26996884

  12. Copper-modified covalent triazine frameworks as non-noble-metal electrocatalysts for oxygen reduction.

    PubMed

    Iwase, Kazuyuki; Yoshioka, Tatsuro; Nakanishi, Shuji; Hashimoto, Kazuhito; Kamiya, Kazuhide

    2015-09-14

    The electrochemical oxygen reduction reaction (ORR) is an important cathode reaction of various types of fuel cells. The development of electrocatalysts composed only of abundant elements is a key goal because currently only platinum is a suitable catalyst for ORR. Herein, we synthesized copper-modified covalent triazine frameworks (CTF) hybridized with carbon nanoparticles (Cu-CTF/CPs) as efficient electrocatalysts for the ORR in neutral solutions. The ORR onset potential of the synthesized Cu-CTF/CP was 810 mV versus the reversible hydrogen electrode (RHE; pH 7), the highest reported value at neutral pH for synthetic Cu-based electrocatalysts. Cu-CTF/CP also displayed higher stability than a Cu-based molecular complex at neutral pH during the ORR, a property that was likely as a result of the covalently cross-linked structure of CTF. This work may provide a new platform for the synthesis of durable non-noble-metal electrocatalysts for various target reactions. PMID:26227987

  13. Noble metal-free bifunctional oxygen evolution and oxygen reduction acidic media electro-catalysts

    NASA Astrophysics Data System (ADS)

    Patel, Prasad Prakash; Datta, Moni Kanchan; Velikokhatnyi, Oleg I.; Kuruba, Ramalinga; Damodaran, Krishnan; Jampani, Prashanth; Gattu, Bharat; Shanthi, Pavithra Murugavel; Damle, Sameer S.; Kumta, Prashant N.

    2016-07-01

    Identification of low cost, highly active, durable completely noble metal-free electro-catalyst for oxygen reduction reaction (ORR) in proton exchange membrane (PEM) fuel cells, oxygen evolution reaction (OER) in PEM based water electrolysis and metal air batteries remains one of the major unfulfilled scientific and technological challenges of PEM based acid mediated electro-catalysts. In contrast, several non-noble metals based electro-catalysts have been identified for alkaline and neutral medium water electrolysis and fuel cells. Herein we report for the very first time, F doped Cu1.5Mn1.5O4, identified by exploiting theoretical first principles calculations for ORR and OER in PEM based systems. The identified novel noble metal-free electro-catalyst showed similar onset potential (1.43 V for OER and 1 V for ORR vs RHE) to that of IrO2 and Pt/C, respectively. The system also displayed excellent electrochemical activity comparable to IrO2 for OER and Pt/C for ORR, respectively, along with remarkable long term stability for 6000 cycles in acidic media validating theory, while also displaying superior methanol tolerance and yielding recommended power densities in full cell configurations.

  14. Noble metal-free bifunctional oxygen evolution and oxygen reduction acidic media electro-catalysts

    PubMed Central

    Patel, Prasad Prakash; Datta, Moni Kanchan; Velikokhatnyi, Oleg I.; Kuruba, Ramalinga; Damodaran, Krishnan; Jampani, Prashanth; Gattu, Bharat; Shanthi, Pavithra Murugavel; Damle, Sameer S.; Kumta, Prashant N.

    2016-01-01

    Identification of low cost, highly active, durable completely noble metal-free electro-catalyst for oxygen reduction reaction (ORR) in proton exchange membrane (PEM) fuel cells, oxygen evolution reaction (OER) in PEM based water electrolysis and metal air batteries remains one of the major unfulfilled scientific and technological challenges of PEM based acid mediated electro-catalysts. In contrast, several non-noble metals based electro-catalysts have been identified for alkaline and neutral medium water electrolysis and fuel cells. Herein we report for the very first time, F doped Cu1.5Mn1.5O4, identified by exploiting theoretical first principles calculations for ORR and OER in PEM based systems. The identified novel noble metal-free electro-catalyst showed similar onset potential (1.43 V for OER and 1 V for ORR vs RHE) to that of IrO2 and Pt/C, respectively. The system also displayed excellent electrochemical activity comparable to IrO2 for OER and Pt/C for ORR, respectively, along with remarkable long term stability for 6000 cycles in acidic media validating theory, while also displaying superior methanol tolerance and yielding recommended power densities in full cell configurations. PMID:27380719

  15. Electrodeposition of Metals in Catalyst Synthesis: The Case of Platinum Monolayer Electrocatalysts

    SciTech Connect

    Vukmirovic, M.B.; Bliznakov, S.T.; Sasaki, K.; Wang, J.X.; Adzic, R.R.

    2011-07-01

    The concern about energy sources, their availability, and related environmental effects, is at an all time high. Proton Exchange Membrane Fuel Cells (PEMFCs) - with an efficiency higher than that of internal combustion engines, light weight, low operating temperature, and fast-start-up capability - are strong candidates for automotive applications. Transportation applications could be especially important in shaping up the new energy economy since they may entail a substantial decrease in the adverse environmental effects linked to the use of fossil fuels and prolong their availability. The largest portion of the cost of PEMFCs reflects the large amount of Pt needed in the cathode's catalytic layer due to the low catalytic activity of Pt for the oxygen reduction reaction (ORR). Recently, considerable advances have been made in fuel cell electrocatalysis yielding improved electrocatalysts, and increasing our understanding of the kinetics of the ORR in combination with significant advances in theoretical treatments. Some of these studies involved: (1) alloying Pt to synthesize bi-metallic catalysts, (2) core-shell nanoparticles catalysts, (3) the role of size, structure, and shape of nanoparticles, and (4) de-alloying of bimetallic alloys. However, a complete understanding of the ORR kinetics on Pt, the best single element catalyst, and of its low efficiency, is yet to be achieved. These problems, compounded with the high Pt content in current cathode catalysts, and with their gradual loss of performance under operating conditions, still hamper commercialization of fuel cells. In order to minimize the amount of noble metal electrocatalysts and maximize their utilization, while achieving high catalytic activity, numerous synthetic approaches have been attempted. The electrocatalysts were prepared using vacuum deposition methods, wet chemistry methods, or electrodeposition techniques. Electrodeposition in particular has several attractive features with respect to the

  16. Semiconductor-Electrocatalyst Interfaces: Theory, Experiment, and Applications in Photoelectrochemical Water Splitting.

    PubMed

    Nellist, Michael R; Laskowski, Forrest A L; Lin, Fuding; Mills, Thomas J; Boettcher, Shannon W

    2016-04-19

    Light-absorbing semiconductor electrodes coated with electrocatalysts are key components of photoelectrochemical energy conversion and storage systems. Efforts to optimize these systems have been slowed by an inadequate understanding of the semiconductor-electrocatalyst (sem|cat) interface. The sem|cat interface is important because it separates and collects photoexcited charge carriers from the semiconductor. The photovoltage generated by the interface drives "uphill" photochemical reactions, such as water splitting to form hydrogen fuel. Here we describe efforts to understand the microscopic processes and materials parameters governing interfacial electron transfer between light-absorbing semiconductors, electrocatalysts, and solution. We highlight the properties of transition-metal oxyhydroxide electrocatalysts, such as Ni(Fe)OOH, because they are the fastest oxygen-evolution catalysts known in alkaline media and are (typically) permeable to electrolyte. We describe the physics that govern the charge-transfer kinetics for different interface types, and show how numerical simulations can explain the response of composite systems. Emphasis is placed on "limiting" behavior. Electrocatalysts that are permeable to electrolyte form "adaptive" junctions where the interface energetics change during operation as charge accumulates in the catalyst, but is screened locally by electrolyte ions. Electrocatalysts that are dense, and thus impermeable to electrolyte, form buried junctions where the interface physics are unchanged during operation. Experiments to directly measure the interface behavior and test the theory/simulations are challenging because conventional photoelectrochemical techniques do not measure the electrocatalyst potential during operation. We developed dual-working-electrode (DWE) photoelectrochemistry to address this limitation. A second electrode is attached to the catalyst layer to sense or control current/voltage independent from that of the

  17. Electrocatalysts having platium monolayers on palladium, palladium alloy, and gold alloy core-shell nanoparticles, and uses thereof

    DOEpatents

    Adzic, Radoslav; Mo, Yibo; Vukmirovic, Miomir; Zhang, Junliang

    2010-12-21

    The invention relates to platinum-coated particles useful as fuel cell electrocatalysts. The particles are composed of a noble metal or metal alloy core at least partially encapsulated by an atomically thin surface layer of platinum atoms. The invention particularly relates to such particles having a palladium, palladium alloy, gold alloy, or rhenium alloy core encapsulated by an atomic monolayer of platinum. In other embodiments, the invention relates to fuel cells containing these electrocatalysts and methods for generating electrical energy therefrom.

  18. Synthesis of platinum nanoparticle electrocatalysts by atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Lubers, Alia Marie

    successful hydrogen pumping catalysts, comparable to a commercial Pt/C catalyst. Synthesized Pt/C materials were also used as PEMFC catalysts. We found the ALD catalysts with lower platinum loading to be competitive with a commercial fuel cell catalyst, especially when exhibiting similar platinum particle characteristics. The functionalized carbon helped produce smaller and more dispersed platinum particles; however, it encouraged carbon corrosion within an electrode, severing electrical connections and lowering energy production. The most suitable chemistry for competitive Pt/C catalysts was produced by platinum ALD on unmodified carbon using hydrogen as a reactant. ALD is a promising method for fabricating electrocatalysts, which could help fuel cells become an economically viable alternative to fossil fuels.

  19. Non-noble electrocatalysts for alkaline fuel cells

    NASA Technical Reports Server (NTRS)

    Sarangapani, S.; Lessner, P.; Manoukian, M.; Giner, J.

    1989-01-01

    Carbons activated with macrocyclics have attracted increasing attention as alternative electrocatalysts for oxygen reduction. Initial activity of these catalysts is good, but performance declines rapidly. Pyrolyzing the macrocyclic on the carbon support leads to enhanced stability and the catalysts retain good activity. The approach described is designed to develop bulk doped catalysts with similar structures to pyrolyzed macrocyclic catalysts. The transition metal and coordinated ligands are dispersed throughout the bulk of the conductive carbon skeleton. Two approaches to realizing this concept are being pursued, both involving the doping of carbon precursors. In one approach, the precursor is a solid phase carbon-containing ion-exchange resin. The precursor is doped with a transition metal and/or nitrogen, and the resulting mixture is pyrolyzed. In the other approach, the precursor is a gas-phase hydrocarbon. This is introduced with a transition metal species and nitrogen species into a reactor and pyrolyzed. Several studies have been conducted to determine if there is a synergistic effect between the transition metal and nitrogen and the effect of different methods of introducing the metal-nitrogen (M-N) coordination on performance. One approach was to introduce the metal and nitrogen separately, for example, by sequentially doping FeCl3 and NH4OH into the resin. Catalysts were prepared from an undoped ion-exchange resin, a resin doped only with N, a resin doped only with Fe, and a resin doped with both Fe and N. Introduction of nitrogen alone has no beneficial effect on the performance of the catalysts. The introduction of the Fe alone significantly improves the performance in both the high and low current density regions. When both Fe and N are introduced, the performance at lower current densities (catalytic activity) is increased beyond that of the Fe-doped carbon, but the performance at higher current densities is similar to the carbon containing only Fe

  20. Tungsten carbides as potential alternative direct methanol fuel cell anode electrocatalysts

    NASA Astrophysics Data System (ADS)

    Zellner, Michael

    The reduction of precious metal loading and the improvement of sluggish kinetics at the anode electrocatalyst are two primary concerns for economical development of direct methanol fuel cells (DMFC). The purpose of this research is to examine the feasibility of using tungsten carbides as alternative fuel cell anode electrocatalysts. The anodic chemistry of the direct methanol fuel cell requires the oxidation of methanol and the decomposition of water to produce protons, electrons, and gas-phase CO2. Currently, the most effective anode electrocatalyst for DMFC is the Pt/Ru bimetallic catalyst, which efficiently oxidizes methanol, as well as decomposes water for the oxidation and removal of adsorbed CO species. Although the Pt/Ru bimetallic system exhibits desirable electrochemical activities, both Pt and Ru are expensive due to limited supplies. In addition, strong chemisorption of CO on Pt and Ru makes the electrocatalyst susceptible to CO poisoning, blocking the active sites for methanol oxidation. This work began by examining the reactions of methanol, water, and CO on carbide-modified tungsten (C/W) single crystal surfaces, with and without submonolayer coverages of Pt. These fundamental surface science results demonstrated the potential for tungsten carbides to be used as anode catalysts in DMFC, exhibiting decomposition of both methanol and water along with significantly lowered CO desorption temperatures. Additionally, submonolayer Pt-modification of the C/W surfaces resulted in a synergistic effect, eliminating the undesired reaction pathway on the C/W surface that produced gas-phase CH4. To bridge the materials gap between model single crystal surfaces and the more realistic thin film electrocatalysts, polycrystalline tungsten carbide thin films were created via physical vapor deposition (PVD) and carburization of polycrystalline tungsten foil. Fundamental surface science techniques were applied to the PVD films to examine the reaction pathways of DMFC

  1. Local atomic structure modulations activate metal oxide as electrocatalyst for hydrogen evolution in acidic water

    PubMed Central

    Li, Yu Hang; Liu, Peng Fei; Pan, Lin Feng; Wang, Hai Feng; Yang, Zhen Zhong; Zheng, Li Rong; Hu, P.; Zhao, Hui Jun; Gu, Lin; Yang, Hua Gui

    2015-01-01

    Modifications of local structure at atomic level could precisely and effectively tune the capacity of materials, enabling enhancement in the catalytic activity. Here we modulate the local atomic structure of a classical but inert transition metal oxide, tungsten trioxide, to be an efficient electrocatalyst for hydrogen evolution in acidic water, which has shown promise as an alternative to platinum. Structural analyses and theoretical calculations together indicate that the origin of the enhanced activity could be attributed to the tailored electronic structure by means of the local atomic structure modulations. We anticipate that suitable structure modulations might be applied on other transition metal oxides to meet the optimal thermodynamic and kinetic requirements, which may pave the way to unlock the potential of other promising candidates as cost-effective electrocatalysts for hydrogen evolution in industry. PMID:26286479

  2. Alloys of platinum and early transition metals as oxygen reduction electrocatalysts.

    PubMed

    Greeley, J; Stephens, I E L; Bondarenko, A S; Johansson, T P; Hansen, H A; Jaramillo, T F; Rossmeisl, J; Chorkendorff, I; Nørskov, J K

    2009-10-01

    The widespread use of low-temperature polymer electrolyte membrane fuel cells for mobile applications will require significant reductions in the amount of expensive Pt contained within their cathodes, which drive the oxygen reduction reaction (ORR). Although progress has been made in this respect, further reductions through the development of more active and stable electrocatalysts are still necessary. Here we describe a new set of ORR electrocatalysts consisting of Pd or Pt alloyed with early transition metals such as Sc or Y. They were identified using density functional theory calculations as being the most stable Pt- and Pd-based binary alloys with ORR activity likely to be better than Pt. Electrochemical measurements show that the activity of polycrystalline Pt(3)Sc and Pt(3)Y electrodes is enhanced relative to pure Pt by a factor of 1.5-1.8 and 6-10, respectively, in the range 0.9-0.87 V. PMID:21378936

  3. Efficient and durable hydrogen evolution electrocatalyst based on nonmetallic nitrogen doped hexagonal carbon

    NASA Astrophysics Data System (ADS)

    Liu, Yanming; Yu, Hongtao; Quan, Xie; Chen, Shuo; Zhao, Huimin; Zhang, Yaobin

    2014-10-01

    The feasibility of renewable energy technology, hydrogen production by water electrolysis, depends on the design of efficient and durable electrocatalyst composed of earth-abundant elements. Herein, a highly active and stable nonmetallic electrocatalyst, nitrogen doped hexagonal carbon (NHC), was developed for hydrogen production. It exhibited high activity for hydrogen evolution with a low overpotential of only 65 mV, an apparent exchange current density of 5.7 × 10-2 mA cm-2 and a high hydrogen production rate of 20.8 mL cm-2 h-1 at -0.35 V. The superior hydrogen evolution activity of NHC stemmed from the intrinsic electrocatalytic property of hexagonal nanodiamond, the rapid charge transfer and abundance of electrocatalytic sites after nitrogen doping. Moreover, NHC was stable in a corrosive acidic solution during electrolysis under high current density.

  4. Local atomic structure modulations activate metal oxide as electrocatalyst for hydrogen evolution in acidic water.

    PubMed

    Li, Yu Hang; Liu, Peng Fei; Pan, Lin Feng; Wang, Hai Feng; Yang, Zhen Zhong; Zheng, Li Rong; Hu, P; Zhao, Hui Jun; Gu, Lin; Yang, Hua Gui

    2015-01-01

    Modifications of local structure at atomic level could precisely and effectively tune the capacity of materials, enabling enhancement in the catalytic activity. Here we modulate the local atomic structure of a classical but inert transition metal oxide, tungsten trioxide, to be an efficient electrocatalyst for hydrogen evolution in acidic water, which has shown promise as an alternative to platinum. Structural analyses and theoretical calculations together indicate that the origin of the enhanced activity could be attributed to the tailored electronic structure by means of the local atomic structure modulations. We anticipate that suitable structure modulations might be applied on other transition metal oxides to meet the optimal thermodynamic and kinetic requirements, which may pave the way to unlock the potential of other promising candidates as cost-effective electrocatalysts for hydrogen evolution in industry. PMID:26286479

  5. An ex-situ and in-situ evaluation of carbides as potential electrocatalysts

    NASA Astrophysics Data System (ADS)

    Weigert, Erich

    One of the most prominent challenges facing the commercialization of the direct methanol fuel cell (DMFC) is the high cost of its electrocatalyst components, particularly the anode. The anode typically requires a high loading of precious metal electrocatalyst (Pt-Ru) to obtain a useful amount of electrical energy from the electrooxidation of methanol (CH3OH). The complete electrooxidation of methanol on these catalysts produces strongly adsorbed CO on the surface, which reduces the activity of Pt. The presence of Ru in these electrocatalysts assists with the decomposition of H2O to more efficiently remove the poisoning CO species as CO2(g). The primary disadvantage of these electrocatalyst components is the scarcity and consequently high price of both Pt and Ru. A series of surface science studies ultrahigh vacuum (UHV) have identified molybdenum and tungsten carbide materials as potential alternative DMFC anode electrocatalysts. Both of these materials demonstrated activity towards the decomposition of methanol and water molecules. The purpose of this research was to extend these investigations by the synthesis and characterization of more realistic carbide materials. This was accomplished by a combination of surface science and electrochemical experiments. The electrochemical studies were performed both in-situ and ex-situ in order to better address the "materials gap" and "pressure gap" that often separate findings in UHV studies from results in more realistic environments. Thin film surfaces of molybdenum carbide could be produced on various carbon substrates in a vacuum system by physical vapor deposition (PVD). When modified with low coverages of Pt, MoC phase molybdenum carbides were found to be more active towards the electrooxidation of hydrogen in an acidic electrolyte than Ptmodified carbon substrates in cyclic voltammetry (CV) studies. These surfaces demonstrated a limited range of electrochemical stability in this acid solution. Mo2C surfaces have

  6. Efficient and durable hydrogen evolution electrocatalyst based on nonmetallic nitrogen doped hexagonal carbon

    PubMed Central

    Liu, Yanming; Yu, Hongtao; Quan, Xie; Chen, Shuo; Zhao, Huimin; Zhang, Yaobin

    2014-01-01

    The feasibility of renewable energy technology, hydrogen production by water electrolysis, depends on the design of efficient and durable electrocatalyst composed of earth-abundant elements. Herein, a highly active and stable nonmetallic electrocatalyst, nitrogen doped hexagonal carbon (NHC), was developed for hydrogen production. It exhibited high activity for hydrogen evolution with a low overpotential of only 65 mV, an apparent exchange current density of 5.7 × 10−2 mA cm−2 and a high hydrogen production rate of 20.8 mL cm−2 h−1 at −0.35 V. The superior hydrogen evolution activity of NHC stemmed from the intrinsic electrocatalytic property of hexagonal nanodiamond, the rapid charge transfer and abundance of electrocatalytic sites after nitrogen doping. Moreover, NHC was stable in a corrosive acidic solution during electrolysis under high current density. PMID:25354806

  7. Nickel sulfide microsphere film on Ni foam as an efficient bifunctional electrocatalyst for overall water splitting.

    PubMed

    Zhu, Wenxin; Yue, Xiaoyue; Zhang, Wentao; Yu, Shaoxuan; Zhang, Yuhuan; Wang, Jing; Wang, Jianlong

    2016-01-25

    Developing low-cost, efficient, and bifunctional electrocatalysts for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is an appealing yet challenging task. Herein, for the first time, a NiS microsphere film was grown in situ on Ni foam (NiS/Ni foam) via a sulfurization reaction as an efficient bifunctional electrocatalyst for overall water splitting with superior activity and good durability. This NiS/Ni foam electrode delivers 20 mA cm(-2) at an overpotential of 158 mV for the HER and 50 mA cm(-2) at an overpotential of 335 mV for the OER in 1.0 M KOH. This bifunctional electrode also enables a high-efficiency alkaline water electrolyzer with 10 mA cm(-2) at a cell voltage of only 1.64 V, which could be promising in water splitting devices for large-scale hydrogen production. PMID:26661579

  8. Durability Enhancement of Intermetallics Electrocatalysts via N-anchor Effect for Fuel Cells

    PubMed Central

    Li, Xiang; An, Li; Chen, Xin; Zhang, Nanlin; Xia, Dingguo; Huang, Weifeng; Chu, Wangsheng; Wu, Ziyu

    2013-01-01

    Insufficient durability and catalytic activity of oxygen reduction reaction (ORR) electrocatalyst are key issues that have to be solved for the practical application of low temperature fuel cell. This paper introduces a new catalyst design strategy using N-anchor to promote the corrosion resistance of electrocatalyst. The as-synthesized N-Pt3Fe1/C shows a high electrocatalytic activity and a superior durability towards ORR. The kinetic current density of N-Pt3Fe1/C as normalized by ECSA is still as high as 0.145 mA cm−2 and only 7% loss after 20000 potential cycles from 0.6 to 1.2 V (vs. NHE) in O2-bubbling perchloric acid solution, whereas Pt3Fe1/C shows 49% loss under the same tests. The N-anchor approach offers novel opportunities for the development of ORR catalyst with excellent electrochemical properties. PMID:24240982

  9. Binary and ternary palladium based electrocatalysts for alkaline direct glycerol fuel cell

    NASA Astrophysics Data System (ADS)

    Geraldes, Adriana Napoleão; da Silva, Dionisio Furtunato; e Silva, Leonardo Gondim de Andrade; Spinacé, Estevam Vitório; Neto, Almir Oliveira; dos Santos, Mauro Coelho

    2015-10-01

    Pd/C, PdAu/C 50:50, PdSn/C 50:50, PdAuSn/C 50:40:10 and PdAuSn/C 50:10:40 electrocatalysts are prepared using an electron beam irradiation reduction method and tested for glycerol electro-oxidation in alkaline medium. X-Ray diffraction (XRD), Energy dispersive X-ray analysis (EDX), Transmission electron Microscopy (TEM) and Cyclic Voltammetry (CV) are used to characterize the resulting materials. The activity for glycerol electro-oxidation is tested in alkaline medium at room temperature using Cyclic Voltammetry and Chronoamperometry (CA) and in a single alkaline direct glycerol fuel cell (ADGFC) at temperature range of 60-90 °C. EDX analysis demonstrate that Pd:Au:Sn atomic ratios are very similar to the nominal ones. X-ray diffractograms of PdAuSn/C electrocatalysts evidence the presence of Pd (fcc), Au (fcc) and SnO2 phases. TEM analysis demonstrates a good dispersion of the nanoparticles on the carbon support with some agglomerates. Cyclic Voltammetry experiments suggest that PdAuSn/C electrocatalysts demonstrate better results. In single fuel cell tests, at 85 °C, using 2.0 mol L-1 glycerol in 2.0 mol L-1 KOH solutions, the electrocatalyst PdAuSn/C 50:40:10 demonstrate highest power density (51 mW cm-2) and the 120 h durability tests demonstrate a 210 μV h-1 degradation rate.

  10. Synthesis and Characterization of CO- and H2S-Tolerant Electrocatalysts for PEM Fuel Cell

    SciTech Connect

    Shamsuddin Ilias

    2006-05-18

    The present state-of-art Proton Exchange Membrane Fuel Cell (PEMFC) technology is based on platinum (Pt) as a catalyst for both the fuel (anode) and air (cathode) electrodes. This catalyst is highly active but susceptible to poisoning by CO, which may be present in the H{sub 2}-fuel used or may be introduced during the fuel processing. Presence of trace amount of CO and H{sub 2}S in the H{sub 2}-fuel poisons the anode irreversibly and decreases the performance of the PEMFCs. In an effort to reduce the Pt-loading and improve the PEMFC performance, we propose to synthesize a number of Pt-based binary, ternary, and quaternary electrocatalysts using Ru, Mo, Ir, Ni, and Co as a substitute for Pt. By fine-tuning the metal loadings and compositions of candidate electrocatalysts, we plan to minimize the cost and optimize the catalyst activity and performance in PEMFC. The feasibility of the novel electrocatalysts will be demonstrated in the proposed effort with gas phase CO and H{sub 2}S concentrations typical of those found in reformed fuel gas with coal/natural gas/methanol feedstocks. During this reporting period we used four Pt-based electrocatalysts (Pt/Ru/Mo/Se, Pt/Ru/Mo/Ir, Pt/Ru/Mo/W, Ptr/Ru/Mo/Co) in MEAs and these were evaluated for CO-tolerance with 20 and 100 ppm CO concentration in H{sub 2}-fuel. From current-voltage performance study, the catalytic activity was found in the increasing order of Pt/Ru/Mo/Ir > Pt/Ru/Mo/W > Pt/Ru/Mo/Co > Pt/Ru/MO/Se. From preliminary cost analysis it appears that could of the catalyst metal loading can reduced by 40% to 60% depending on the selection of metal combinations without compromising the fuel cell performance.

  11. Synthesis and Characterization of CO- and H2S-Tolerant Electrocatalysts for PEM Fuel Cell

    SciTech Connect

    Shamsuddin Ilias

    2006-09-30

    The present state-of-art Proton Exchange Membrane Fuel Cell (PEMFC) technology is based on platinum (Pt) as a catalyst for both the fuel (anode) and air (cathode) electrodes. This catalyst is highly active but susceptible to poisoning by CO, which may be present in the H{sub 2}-fuel used or may be introduced during the fuel processing. Presence of trace amount of CO and H{sub 2}S in the H{sub 2}-fuel poisons the anode irreversibly and decreases the performance of the PEMFCs. In an effort to reduce the Pt-loading and improve the PEMFC performance, we propose to synthesize a number of Pt-based binary, ternary, and quaternary electrocatalysts using Ru, Mo, Ir, Ni, and Co as a substitute for Pt. By fine-tuning the metal loadings and compositions of candidate electrocatalysts, we plan to minimize the cost and optimize the catalyst activity and performance in PEMFC. The feasibility of the novel electrocatalysts will be demonstrated in the proposed effort with gas phase CO and H{sub 2}S concentrations typical of those found in reformed fuel gas with coal/natural gas/methanol feedstocks. In this work binary, ternary, and quaternary platinum-based electrocatalysts were synthesized for the purpose of lowering the cost and increasing the CO tolerance of the membrane electrode assembly (MEA) in the fuel cell. The metals Ru, Mo, W, Ir, Co and Se were alloyed with platinum on a carbon support using a modified reduction method. These catalysts were fabricated into MEAs and evaluated for electrical performance and CO tolerance with polarization experiments. The quaternary system Pt/Ru/Mo/Ir system is the most CO tolerant in the PEMFC and has a low total metal loading of 0.4 mg/cm{sup 2} in the electrode of the cell.

  12. Synthesis and Characterization of CO- and H2S-Tolerant Electrocatalysts for PEM Fuel Cell

    SciTech Connect

    Shamsuddin Ilias

    2005-07-20

    The present state-of-art Proton Exchange Membrane Fuel Cell (PEMFC) technology is based on platinum (Pt) as a catalyst for both the fuel (anode) and air (cathode) electrodes. This catalyst is highly active but susceptible to poisoning by CO, which may be present in the H{sub 2}-fuel used or may be introduced during the fuel processing. Presence of trace amount of CO and H{sub 2}S in the H{sub 2}-fuel poisons the anode irreversibly and decreases the performance of the PEMFCs. In an effort to reduce the Pt-loading and improve the PEMFC performance, we propose to synthesize a number of Pt-based binary, ternary, and quaternary electrocatalysts using Ru, Mo, Ir, Ni, and Co as a substitute for Pt. By fine-tuning the metal loadings and compositions of candidate electrocatalysts, we plan to minimize the cost and optimize the catalyst activity and performance in PEMFC. The feasibility of the novel electrocatalysts will be demonstrated in the proposed effort with gas phase CO and H{sub 2}S concentrations typical of those found in reformed fuel gas with coal/natural gas/methanol feedstocks. During this reporting period we synthesized several tri-metallic electrocatalysts catalysts (Pt/Ru/Mo, Pt/Ru/Ir, Pt/Ru/W, Ptr/Ru/Co, and Pt/Ru/Se on Vulcan XG72 Carbon) by ultrasonication method. These catalysts were tested in MEAs for CO tolerance at 20 and 100 ppm CO concentrations. From Galvonstatic study the catalytic activity was found in the order of: Pt/Ru/Mo/C > Pt/Ru/Ir/C > Pt/Ru/W/C > Ptr/Ru/Co/C > and Pt/Ru/Se. The catalysts performed very well at 20 ppm CO but at 100 ppm CO performance dropped significantly.

  13. Cu,N-codoped Hierarchical Porous Carbons as Electrocatalysts for Oxygen Reduction Reaction.

    PubMed

    Yu, Haiyan; Fisher, Adrian; Cheng, Daojian; Cao, Dapeng

    2016-08-24

    It remains a huge challenge to develop nonprecious electrocatalysts with high activity to substitute commercial Pt catalysts for oxygen reduction reactions (ORR). Here, the Cu,N-codoped hierarchical porous carbon (Cu-N-C) with a high content of pyridinic N was synthesized by carbonizing Cu-containing ZIF-8. Results indicate that Cu-N-C shows excellent ORR electrocatalyst properties. First of all, it nearly follows the four-electron route, and its electron transfer number reaches 3.92 at -0.4 V. Second, both the onset potential and limited current density of Cu-N-C are almost equal to those of a commercial Pt/C catalyst. Third, it exhibits a better half-wave potential (∼16 mV) than a commercial Pt/C catalyst. More importantly, the Cu-N-C displays better stability and methanol tolerance than the Pt/C catalyst. All of these good properties are attributed to hierarchical structure, high pyridinic N content, and the synergism of Cu and N dopants. The metal-N codoping strategy can significantly enhance the activity of electrocatalysts, and it will provide reference for the design of novel N-doped porous carbon ORR catalysts. PMID:27490846

  14. Highly Porous Carbon Derived from MOF-5 as a Support of ORR Electrocatalysts for Fuel Cells.

    PubMed

    Khan, Inayat Ali; Qian, Yuhong; Badshah, Amin; Nadeem, Muhammad Arif; Zhao, Dan

    2016-07-13

    The development of highly competent electrocatalysts for the sluggish oxygen reduction reaction (ORR) at cathodes of proton-exchange membrane fuel cells (PEMFCs) is extremely important for their long-term operation and wide applications. Herein, we present highly efficient ORR electrocatalysts based on Pt/Ni bimetallic nanoparticles dispersed on highly porous carbon obtained via pyrolysis of a metal-organic framework MOF-5. In comparison to the commercial Pt/C (20%), the electrocatalyst Pt-Ni/PC 950 (15:15%) in this study exhibits a pronounced positive shift of 90 mV in Eonset. In addition, it also demonstrates excellent long-term stability and durability during the 500-cycle continue-oxygen-supply (COS) accelerating durability tests (ADTs). The significantly improved activity and stability of Pt-Ni/PC 950 (15:15%) can be attributed to the Pt electron interaction with Ni and carbon support as has been proved in X-ray and microscopic analysis. PMID:27327655

  15. Platinum Monolayer on IrFe Core-Shell Nanoparticle Electrocatalysts for the Oxygen Reduction Reaction

    SciTech Connect

    K Sasaki; K Kuttiyiel; D Su; R Adzic

    2011-12-31

    We synthesized high activity and stability platinum monolayer on IrFe core-shell nanoparticle electrocatalysts. Carbon-supported IrFe core-shell nanoparticles were synthesized by chemical reduction and subsequent thermal annealing. The formation of Ir shells on IrFe solid-solution alloy cores has been verified by scanning transmission electron microscopy coupled with energy-loss spectroscopy (EELS) and in situ X-ray absorption spectroscopy. The Pt monolayers were deposited on IrFe core-shell nanoparticles by galvanic replacement of underpotentially deposited Cu adatoms on the Ir shell surfaces. The specific and Pt mass activities for the ORR on the Pt monolayer on IrFe core-shell nanoparticle electrocatalyst are 0.46 mA/cm{sup 2} and 1.1 A/mg{sub Pt}, which are much higher than those on a commercial Pt/C electrocatalyst. High durability of Pt{sub ML}/IrFe/C has also been demonstrated by potential cycling tests. These high activity and durability observed can be ascribed to the structural and electronic interaction between the Pt monolayer and the IrFe core-shell nanoparticles.

  16. Platinum Monolayer on IrFe Core–Shell Nanoparticle Electrocatalysts for the Oxygen Reduction Reaction

    SciTech Connect

    Sasaki K.; Kuttiyiel, K.A.; Su, D.; Adzic, R.R.

    2012-04-19

    We synthesized high activity and stability platinum monolayer on IrFe core-shell nanoparticle electrocatalysts. Carbon-supported IrFe core-shell nanoparticles were synthesized by chemical reduction and subsequent thermal annealing. The formation of Ir shells on IrFe solid-solution alloy cores has been verified by scanning transmission electron microscopy coupled with energy-loss spectroscopy (EELS) and in situ X-ray absorption spectroscopy. The Pt monolayers were deposited on IrFe core-shell nanoparticles by galvanic replacement of underpotentially deposited Cu adatoms on the Ir shell surfaces. The specific and Pt mass activities for the ORR on the Pt monolayer on IrFe core-shell nanoparticle electrocatalyst are 0.46 mA/cm{sup 2} and 1.1 A/mg{sub Pt}, which are much higher than those on a commercial Pt/C electrocatalyst. High durability of Pt{sub ML}/IrFe/C has also been demonstrated by potential cycling tests. These high activity and durability observed can be ascribed to the structural and electronic interaction between the Pt monolayer and the IrFe core-shell nanoparticles.

  17. Novel cobalt quantum dot/graphene nanocomposites as highly efficient electrocatalysts for water splitting.

    PubMed

    Govindhan, Maduraiveeran; Mao, Brennan; Chen, Aicheng

    2016-01-21

    A cost-effective, non-noble metal based high-performance electrocatalyst for the oxygen evolution reaction (OER) is critical to energy conversion and storage processes. Here, we report on a facile and effective in situ strategy for the synthesis of an advanced nanocomposite material that is comprised of cobalt quantum dots (Co QDs, ∼3.2 nm), uniformly dispersed on reduced graphene oxide (rGO) as a highly efficient OER electrocatalyst platform. This nanocomposite electrocatalyst afforded a mass activity of 1250 A g(-1) at a low overpotential (η) of 0.37 V, a small Tafel slope of ∼37 mV dec(-1) and a turnover frequency (TOF) of 0.188 s(-1) in 0.1 M KOH, comparing favorably with state-of-the-art RuO2, IrO2 and Pt/C catalysts. The synergy between abundant catalytically active sites through the fine dispersion of Co QDs, and enhanced electron transfer generated from the graphene resulted in first-rate electrocatalytic properties toward the OER. These merits coupled with the higher stability of the nanocomposite hold great promise for triggering breakthroughs in electrocatalysis for water splitting. PMID:26677009

  18. Ammonia intercalated flower-like MoS2 nanosheet film as electrocatalyst for high efficient and stable hydrogen evolution

    PubMed Central

    Wang, F. Z.; Zheng, M. J.; Zhang, B.; Zhu, C. Q.; Li, Q.; Ma, L.; Shen, W. Z.

    2016-01-01

    Ammonia intercalated flower-like MoS2 electrocatalyst film assembled by vertical orientated ultrathin nanosheet on graphite sheethas been successfully synthesized using one-step hydrothermal method. In this strategy, ammonia can effectively insert into the parallel plane of the MoS2 nanosheets, leading to the expansion of lattice and phase transfer from 2H to 1T, generating more active unsaturated sulfur atoms. The flower-like ammoniated MoS2 electrocatalysts with more active sites and large surface area exhibited excellent HER activity with a small Tafel slope and low onset overpotential, resulting a great enhancement in hydrogen evolution. The high efficient activity and recyclable utilization, as well as large-scale, indicate that it is a very promising electrocatalyst to replace Pt in industry application. PMID:27538812

  19. Single-Molecule Nanocatalysis Shows In Situ Deactivation of Pt/C Electrocatalysts during the Hydrogen-Oxidation Reaction.

    PubMed

    Zhang, Yuwei; Chen, Tao; Alia, Shaun; Pivovar, Bryan S; Xu, Weilin

    2016-02-24

    By coupling a Pt-catalyzed fluorogenic reaction with the Pt-electrocatalyzed hydrogen-oxidation reaction (HOR), we combine single-molecule fluorescence microscopy with traditional electrochemical methods to study the real-time deactivation kinetics of a Pt/C electrocatalyst at single-particle level during electrocatalytic hydrogen-oxidation reaction. The decay of the catalytic performance of Pt/C could be mainly attributed to the electrocatalysis-induced etching or dissolution of Pt nanoparticles. Spontaneous regeneration of activity and incubation period of the Pt electrocatalyst were also observed at single-particle level. All these new insights are practically useful for the understanding and rational design of highly efficient electrocatalysts for application in fuel cells. PMID:26821777

  20. Highly active and durable methanol oxidation electrocatalyst based on the synergy of platinum–nickel hydroxide–graphene

    PubMed Central

    Huang, Wenjing; Wang, Hongtao; Zhou, Jigang; Wang, Jian; Duchesne, Paul N.; Muir, David; Zhang, Peng; Han, Na; Zhao, Feipeng; Zeng, Min; Zhong, Jun; Jin, Chuanhong; Li, Yanguang; Lee, Shuit-Tong; Dai, Hongjie

    2015-01-01

    Active and durable electrocatalysts for methanol oxidation reaction are of critical importance to the commercial viability of direct methanol fuel cell technology. Unfortunately, current methanol oxidation electrocatalysts fall far short of expectations and suffer from rapid activity degradation. Here we report platinum–nickel hydroxide–graphene ternary hybrids as a possible solution to this long-standing issue. The incorporation of highly defective nickel hydroxide nanostructures is believed to play the decisive role in promoting the dissociative adsorption of water molecules and subsequent oxidative removal of carbonaceous poison on neighbouring platinum sites. As a result, the ternary hybrids exhibit exceptional activity and durability towards efficient methanol oxidation reaction. Under periodic reactivations, the hybrids can endure at least 500,000 s with negligible activity loss, which is, to the best of our knowledge, two to three orders of magnitude longer than all available electrocatalysts. PMID:26602295

  1. Ammonia intercalated flower-like MoS2 nanosheet film as electrocatalyst for high efficient and stable hydrogen evolution.

    PubMed

    Wang, F Z; Zheng, M J; Zhang, B; Zhu, C Q; Li, Q; Ma, L; Shen, W Z

    2016-01-01

    Ammonia intercalated flower-like MoS2 electrocatalyst film assembled by vertical orientated ultrathin nanosheet on graphite sheethas been successfully synthesized using one-step hydrothermal method. In this strategy, ammonia can effectively insert into the parallel plane of the MoS2 nanosheets, leading to the expansion of lattice and phase transfer from 2H to 1T, generating more active unsaturated sulfur atoms. The flower-like ammoniated MoS2 electrocatalysts with more active sites and large surface area exhibited excellent HER activity with a small Tafel slope and low onset overpotential, resulting a great enhancement in hydrogen evolution. The high efficient activity and recyclable utilization, as well as large-scale, indicate that it is a very promising electrocatalyst to replace Pt in industry application. PMID:27538812

  2. Pomegranate-Inspired Design of Highly Active and Durable Bifunctional Electrocatalysts for Rechargeable Metal-Air Batteries.

    PubMed

    Li, Ge; Wang, Xiaolei; Fu, Jing; Li, Jingde; Park, Moon Gyu; Zhang, Yining; Lui, Gregory; Chen, Zhongwei

    2016-04-11

    Rational design of highly active and durable electrocatalysts for oxygen reactions is critical for rechargeable metal-air batteries. Herein, we report the design and development of composite electrocatalysts based on transition metal oxide nanocrystals embedded in a nitrogen-doped, partially graphitized carbon framework. Benefiting from the unique pomegranate-like architecture, the composite catalysts possess abundant active sites, strong synergetic coupling, enhanced electron transfer, and high efficiencies in the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). The Co3O4-based composite electrocatalyst exhibited a high half-wave potential of 0.842 V for ORR, and a low overpotential of only 450 mV at the current density of 10 mA cm(-2) for OER. A single-cell zinc-air battery was also fabricated with superior durability, holding great promise in the practical implementation of rechargeable metal-air batteries. PMID:26970076

  3. Highly active and durable methanol oxidation electrocatalyst based on the synergy of platinum-nickel hydroxide-graphene.

    PubMed

    Huang, Wenjing; Wang, Hongtao; Zhou, Jigang; Wang, Jian; Duchesne, Paul N; Muir, David; Zhang, Peng; Han, Na; Zhao, Feipeng; Zeng, Min; Zhong, Jun; Jin, Chuanhong; Li, Yanguang; Lee, Shuit-Tong; Dai, Hongjie

    2015-01-01

    Active and durable electrocatalysts for methanol oxidation reaction are of critical importance to the commercial viability of direct methanol fuel cell technology. Unfortunately, current methanol oxidation electrocatalysts fall far short of expectations and suffer from rapid activity degradation. Here we report platinum-nickel hydroxide-graphene ternary hybrids as a possible solution to this long-standing issue. The incorporation of highly defective nickel hydroxide nanostructures is believed to play the decisive role in promoting the dissociative adsorption of water molecules and subsequent oxidative removal of carbonaceous poison on neighbouring platinum sites. As a result, the ternary hybrids exhibit exceptional activity and durability towards efficient methanol oxidation reaction. Under periodic reactivations, the hybrids can endure at least 500,000 s with negligible activity loss, which is, to the best of our knowledge, two to three orders of magnitude longer than all available electrocatalysts. PMID:26602295

  4. Investigating the effects of proton exchange membrane fuel cell conditions on carbon supported platinum electrocatalyst composition and performance

    SciTech Connect

    A. Patel; K. Artyushkova; P. Atanassov; V. Colbow; M. Dutta; D. Harvey; S. Wessel

    2012-04-30

    Changes that carbon-supported platinum electrocatalysts undergo in a proton exchange membrane fuel cell environment were simulated by ex situ heat treatment of catalyst powder samples at 150 C and 100% relative humidity. In order to study modifications that are introduced to chemistry, morphology, and performance of electrocatalysts, XPS, HREELS and three-electrode rotating disk electrode experiments were performed. Before heat treatment, graphitic content varied by 20% among samples with different types of carbon supports, with distinct differences between bulk and surface compositions within each sample. Following the aging protocol, the bulk and surface chemistry of the samples were similar, with graphite content increasing or remaining constant and Pt-carbide decreasing for all samples. From the correlation of changes in chemical composition and losses in performance of the electrocatalysts, we conclude that relative distribution of Pt particles on graphitic and amorphous carbon is as important for electrocatalytic activity as the absolute amount of graphitic carbon present

  5. Investigating the effects of proton exchange membrane fuel cell conditions on carbon supported platinum electrocatalyst composition and performance

    SciTech Connect

    Patel, Anant; Artyushkova, Kateryna; Atanassov, Plamen; Colbow, Vesna; Dutta, Monica; Harvey, Davie; Wessel, Silvia

    2012-04-01

    Changes that carbon-supported platinum electrocatalysts undergo in a proton exchange membrane fuel cell environment were simulated by ex situ heat treatment of catalyst powder samples at 150 #2;C and 100% relative humidity. In order to study modifications that are introduced to chemistry, morphology, and performance of electrocatalysts, XPS, HREELS and three-electrode rotating disk electrode experiments were performed. Before heat treatment, graphitic content varied by 20% among samples with different types of carbon supports, with distinct differences between bulk and surface compositions within each sample. Following the aging protocol, the bulk and surface chemistry of the samples were similar, with graphite content increasing or remaining constant and Pt-carbide decreasing for all samples. From the correlation of changes in chemical composition and losses in performance of the electrocatalysts, we conclude that relative distribution of Pt particles on graphitic and amorphous carbon is as important for electrocatalytic activity as the absolute amount of graphitic carbon present

  6. Porous one-dimensional Mo2C-amorphous carbon composites: high-efficient and durable electrocatalysts for hydrogen generation.

    PubMed

    Zhang, Kai; Li, Chunyan; Zhao, Yang; Yu, Xianbo; Chen, Yujin

    2015-07-01

    Porous one-dimensional Mo2C-amorphous carbon composites, fabricated by in situ solid state reactions, are exhibited as effective and high-performance electrocatalysts towards the hydrogen evolution reaction (HER). The morphological and structural characteristics of the Mo2C based electrocatalysts were analyzed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). The analyses showed that they had various advantages for the HER, including a high crystallinity, porous and tubular characteristics and good conductivity. The porous one-dimensional Mo2C-amorphous carbon composites with a larger content of Mo2C and moderate thickness of the carbon layers exhibited superior catalytic activities for HER to most of the Mo2C based electrocatalysts recently reported. PMID:26055048

  7. Bioinspired synthesis of nitrogen/sulfur co-doped graphene as an efficient electrocatalyst for oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Zhang, Huanhuan; Liu, Xiangqian; He, Guangli; Zhang, Xiaoxing; Bao, Shujuan; Hu, Weihua

    2015-04-01

    Efficient electrocatalyst of oxygen reduction reaction (ORR) is crucial for a variety of renewable energy applications and heteroatom-doped carbon materials have demonstrated promising catalytic performance towards ORR. In this paper we report a bioinspired method to synthesize nitrogen/sulfur (N/S) co-doped graphene as an efficient ORR electrocatalyst via self-polymerization of polydopamine (PDA) thin layer on graphene oxide sheets, followed by reacting with cysteine and finally thermal annealing in Argon (Ar) atmosphere. As-prepared N/S co-doped graphene exhibits significantly enhanced ORR catalytic activity in alkaline solution compared with pristine graphene or N-doped graphene. It also displays long-term operation stability and strong tolerance to methanol poison effect, indicating it a promising ORR electrocatalyst.

  8. Highly active and durable methanol oxidation electrocatalyst based on the synergy of platinum-nickel hydroxide-graphene

    NASA Astrophysics Data System (ADS)

    Huang, Wenjing; Wang, Hongtao; Zhou, Jigang; Wang, Jian; Duchesne, Paul N.; Muir, David; Zhang, Peng; Han, Na; Zhao, Feipeng; Zeng, Min; Zhong, Jun; Jin, Chuanhong; Li, Yanguang; Lee, Shuit-Tong; Dai, Hongjie

    2015-11-01

    Active and durable electrocatalysts for methanol oxidation reaction are of critical importance to the commercial viability of direct methanol fuel cell technology. Unfortunately, current methanol oxidation electrocatalysts fall far short of expectations and suffer from rapid activity degradation. Here we report platinum-nickel hydroxide-graphene ternary hybrids as a possible solution to this long-standing issue. The incorporation of highly defective nickel hydroxide nanostructures is believed to play the decisive role in promoting the dissociative adsorption of water molecules and subsequent oxidative removal of carbonaceous poison on neighbouring platinum sites. As a result, the ternary hybrids exhibit exceptional activity and durability towards efficient methanol oxidation reaction. Under periodic reactivations, the hybrids can endure at least 500,000 s with negligible activity loss, which is, to the best of our knowledge, two to three orders of magnitude longer than all available electrocatalysts.

  9. SYNTHESIS AND CHARACTERIZATION OF CO-AND H2S-TOLERANT ELECTROCATALYSTS FOR PEM FUEL CELL

    SciTech Connect

    Shamsuddin Ilias

    2005-03-29

    The present state-of-art Proton Exchange Membrane Fuel Cell (PEMFC) technology is based on platinum (Pt) as a catalyst for both the fuel (anode) and air (cathode) electrodes. This catalyst is highly active but susceptible to poisoning by CO, which may be present in the H{sub 2}-fuel used or may be introduced during the fuel processing. Presence of trace amount of CO and H{sub 2}S in the H{sub 2}-fuel poisons the anode irreversibly and decreases the performance of the PEMFCs. In an effort to reduce the Pt-loading and improve the PEMFC performance, we propose to synthesize a number of Pt-based binary, ternary, and quaternary electrocatalysts using Ru, Mo, Ir, Ni, and Co as a substitute for Pt. By fine-tuning the metal loadings and compositions of candidate electrocatalysts, we plan to minimize the cost and optimize the catalyst activity and performance in PEMFC. The feasibility of the novel electrocatalysts will be demonstrated in the proposed effort with gas phase CO and H{sub 2}S concentrations typical of those found in reformed fuel gas with coal/natural gas/methanol feedstocks. During this reporting period several bi-metallic electrocatalysts were synthesized using ultra-sonication. These catalysts (Pt/Ru, Pt/Mo and Pt/Ir) were tested in MEAs. From Galvonstatic study the catalytic activity was found in the order of: Pt/Ru/C > Pt/Mo/C > Pt/Ir/C. It appears that electrocatalysts prepared by ultra-sonication process are more active compared to the conventional technique. Work is in progress to further study these catalysts for CO-tolerance in PEMFC and identify potential candidate metals for synthesis of tri-metallic electrocatalysts.

  10. Novel cobalt quantum dot/graphene nanocomposites as highly efficient electrocatalysts for water splitting

    NASA Astrophysics Data System (ADS)

    Govindhan, Maduraiveeran; Mao, Brennan; Chen, Aicheng

    2016-01-01

    A cost-effective, non-noble metal based high-performance electrocatalyst for the oxygen evolution reaction (OER) is critical to energy conversion and storage processes. Here, we report on a facile and effective in situ strategy for the synthesis of an advanced nanocomposite material that is comprised of cobalt quantum dots (Co QDs, ~3.2 nm), uniformly dispersed on reduced graphene oxide (rGO) as a highly efficient OER electrocatalyst platform. This nanocomposite electrocatalyst afforded a mass activity of 1250 A g-1 at a low overpotential (η) of 0.37 V, a small Tafel slope of ~37 mV dec-1 and a turnover frequency (TOF) of 0.188 s-1 in 0.1 M KOH, comparing favorably with state-of-the-art RuO2, IrO2 and Pt/C catalysts. The synergy between abundant catalytically active sites through the fine dispersion of Co QDs, and enhanced electron transfer generated from the graphene resulted in first-rate electrocatalytic properties toward the OER. These merits coupled with the higher stability of the nanocomposite hold great promise for triggering breakthroughs in electrocatalysis for water splitting.A cost-effective, non-noble metal based high-performance electrocatalyst for the oxygen evolution reaction (OER) is critical to energy conversion and storage processes. Here, we report on a facile and effective in situ strategy for the synthesis of an advanced nanocomposite material that is comprised of cobalt quantum dots (Co QDs, ~3.2 nm), uniformly dispersed on reduced graphene oxide (rGO) as a highly efficient OER electrocatalyst platform. This nanocomposite electrocatalyst afforded a mass activity of 1250 A g-1 at a low overpotential (η) of 0.37 V, a small Tafel slope of ~37 mV dec-1 and a turnover frequency (TOF) of 0.188 s-1 in 0.1 M KOH, comparing favorably with state-of-the-art RuO2, IrO2 and Pt/C catalysts. The synergy between abundant catalytically active sites through the fine dispersion of Co QDs, and enhanced electron transfer generated from the graphene resulted in

  11. Atomically monodisperse nickel nanoclusters as highly active electrocatalysts for water oxidation

    NASA Astrophysics Data System (ADS)

    Joya, Khurram S.; Sinatra, Lutfan; Abdulhalim, Lina G.; Joshi, Chakra P.; Hedhili, M. N.; Bakr, Osman M.; Hussain, Irshad

    2016-05-01

    Achieving water splitting at low overpotential with high oxygen evolution efficiency and stability is important for realizing solar to chemical energy conversion devices. Herein we report the synthesis, characterization and electrochemical evaluation of highly active nickel nanoclusters (Ni NCs) for water oxidation at low overpotential. These atomically precise and monodisperse Ni NCs are characterized by using UV-visible absorption spectroscopy, single crystal X-ray diffraction and mass spectrometry. The molecular formulae of these Ni NCs are found to be Ni4(PET)8 and Ni6(PET)12 and are highly active electrocatalysts for oxygen evolution without any pre-conditioning. Ni4(PET)8 are slightly better catalysts than Ni6(PET)12 which initiate oxygen evolution at an amazingly low overpotential of ~1.51 V (vs. RHE; η ~ 280 mV). The peak oxygen evolution current density (J) of ~150 mA cm-2 at 2.0 V (vs. RHE) with a Tafel slope of 38 mV dec-1 is observed using Ni4(PET)8. These results are comparable to the state-of-the-art RuO2 electrocatalyst, which is highly expensive and rare compared to Ni-based materials. Sustained oxygen generation for several hours with an applied current density of 20 mA cm-2 demonstrates the long-term stability and activity of these Ni NCs towards electrocatalytic water oxidation. This unique approach provides a facile method to prepare cost-effective, nanoscale and highly efficient electrocatalysts for water oxidation.Achieving water splitting at low overpotential with high oxygen evolution efficiency and stability is important for realizing solar to chemical energy conversion devices. Herein we report the synthesis, characterization and electrochemical evaluation of highly active nickel nanoclusters (Ni NCs) for water oxidation at low overpotential. These atomically precise and monodisperse Ni NCs are characterized by using UV-visible absorption spectroscopy, single crystal X-ray diffraction and mass spectrometry. The molecular formulae of these

  12. Triblock polymer mediated synthesis of Ir-Sn oxide electrocatalysts for oxygen evolution reaction

    NASA Astrophysics Data System (ADS)

    Li, Guangfu; Yu, Hongmei; Wang, Xunying; Yang, Donglei; Li, Yongkun; Shao, Zhigang; Yi, Baolian

    2014-03-01

    Over the past several decades, tremendous effort has been put into developing cost-effective, highly active and durable electrocatalysts for oxygen evolution reaction (OER) in the proton exchange membrane water electrolyzer. This report explores an advanced and effective "soft" material-assistant method to fabricate Ir0.6Sn0.4O2 electrocatalysts with a 0.6/0.4 ratio of Ir/Sn in precursors. Adopting a series of characterization methods, the collective results suggest that the surfactant-material F127 content, as an important factor, can efficiently control the formation of Ir-Sn oxides with varying surface properties and morphologies, such as the grainy and rod-shaped structures. Associating with the half-cell and single electrolyzer, it is affirmed that the optimal ratio of (Ir + Sn)/F127 is 100 for the preparation of S100-Ir0.6Sn0.4O2 with obviously enhanced activity and sufficient durability under the electrolysis circumstances. The lowest cell voltages obtained at 80 °C are 1.631 V at 1000 mA cm-2, and 1.820 V at 2000 mA cm-2, when applying S100-Ir0.6Sn0.4O2 OER catalyst and Ti-material diffusion layer on the anode side and Nafion® 115 membrane. Furthermore, the noble-metal Ir loading in the same cell decreases to 0.77 mg cm-2. These results highlight that Ir-Sn oxide synthesized by the soft-material method is a promising OER electrocatalyst.

  13. Effects of ligand modification and protonation on metal oxime hydrogen evolution electrocatalysts.

    PubMed

    Solis, Brian H; Yu, Yinxi; Hammes-Schiffer, Sharon

    2013-06-17

    The design of hydrogen-evolving electrocatalysts that operate at modest overpotentials is important for solar energy devices. The M(II/I) reduction potential for metal diimine-dioxime and diglyoxime electrocatalysts is often related to the overpotential required for hydrogen evolution. Herein the impact of ligand modification and protonation on the M(II/I) reduction potentials for cobalt, nickel, and iron diimine-dioxime and diglyoxime complexes is investigated with computational methods. The calculations are consistent with experimental data available for some of these complexes and additionally provide predictions for complexes that have not yet been synthesized. The calculated pKa's imply that ligand protonation is likely to occur at the O-H-O bridge but not at other ligand sites for these complexes. Moreover, the calculations imply that a ligand-protonated Co(III)-hydride intermediate is formed along the H2 production pathway for catalysts containing an O-H-O bridge in the presence of sufficiently strong acid. The calculated M(II/I) reduction potentials indicate that the anodic shift due to protonation of the O-H-O bridge is greater than that due to replacing the O-H-O bridge with an O-BF2-O bridge for cobalt and nickel but not for iron complexes. Experiments suggest degradation for complexes with two O-H-O bridges and alternative mechanisms for certain iron complexes with two O-BF2-O bridges. Asymmetric cobalt, nickel, and strongly electron withdrawing substituted iron diimine-dioxime and diglyoxime complexes containing a single O-H-O bridge are proposed to be effective hydrogen evolution electrocatalysts with relatively low overpotentials in acetonitrile and water. These insights are important for the design of efficient aqueous-based hydrogen-evolving catalysts. PMID:23701462

  14. Atomically monodisperse nickel nanoclusters as highly active electrocatalysts for water oxidation.

    PubMed

    Joya, Khurram S; Sinatra, Lutfan; AbdulHalim, Lina G; Joshi, Chakra P; Hedhili, M N; Bakr, Osman M; Hussain, Irshad

    2016-05-14

    Achieving water splitting at low overpotential with high oxygen evolution efficiency and stability is important for realizing solar to chemical energy conversion devices. Herein we report the synthesis, characterization and electrochemical evaluation of highly active nickel nanoclusters (Ni NCs) for water oxidation at low overpotential. These atomically precise and monodisperse Ni NCs are characterized by using UV-visible absorption spectroscopy, single crystal X-ray diffraction and mass spectrometry. The molecular formulae of these Ni NCs are found to be Ni4(PET)8 and Ni6(PET)12 and are highly active electrocatalysts for oxygen evolution without any pre-conditioning. Ni4(PET)8 are slightly better catalysts than Ni6(PET)12 which initiate oxygen evolution at an amazingly low overpotential of ∼1.51 V (vs. RHE; η≈ 280 mV). The peak oxygen evolution current density (J) of ∼150 mA cm(-2) at 2.0 V (vs. RHE) with a Tafel slope of 38 mV dec(-1) is observed using Ni4(PET)8. These results are comparable to the state-of-the-art RuO2 electrocatalyst, which is highly expensive and rare compared to Ni-based materials. Sustained oxygen generation for several hours with an applied current density of 20 mA cm(-2) demonstrates the long-term stability and activity of these Ni NCs towards electrocatalytic water oxidation. This unique approach provides a facile method to prepare cost-effective, nanoscale and highly efficient electrocatalysts for water oxidation. PMID:27109550

  15. Pt/C-Electrocatalyst Painting on Polymer Electrolyte Membrane by Electrostatic Spray Deposition

    NASA Astrophysics Data System (ADS)

    Umeda, Minoru; Kawaguchi, Syunsuke; Yamada, Akifumi; Uchida, Isamu

    2005-02-01

    An electrocatalyst painting technique for use in a limited surface area of a polymer electrolyte membrane has been developed by employing electrostatic spray deposition (ESD). ESD is a process in which an aerosol of a solution is ejected from a metal syringe nozzle with a high applied voltage under atmosphere to obtain a thin film on the counter electrode. First, a dispersion containing Pt-loading carbon (Pt/C) powder and Nafion solution was sprayed by using the ESD technique. As a result, the dispersion was deposited over the entire surface area of a polymer electrolyte membrane of Nafion that was placed on the counter Au electrode, whereas, the dispersion was neither deposited on an electric-insulating poly(ethylene telephthalete) (PET) nor on the Nafion membrane on the PET. For the experiment, the Nafion membrane was pretreated to give it ionic conductivity. Next, a dye solution containing Rhodamine B was sprayed in the same manner, with the same result. In the case where the sizes of Nafion membrane and Au electrode were the same, the deposition only occurred on the Nafion/Au layered structure. According to these results, the aerosol generated at the syringe nozzle is introduced to the conductive area and kept away from the insulating area. Finally, for the untreated Nafion membrane on which a water droplet was placed, ESD of the Pt/C dispersion was conducted. Consequently, an electrocatalyst layer was successfully formed only at the wetted point of the Nafion membrane. This technique enables the painting of an electrocatalyst layer over a limited area without the use of any surface mask.

  16. Semiconductor-electrocatalyst contacts: theory, experiment, and applications to solar water photoelectrolysis

    SciTech Connect

    Boettcher, Shannon W.

    2015-10-21

    Semiconductor photoelectrodes coated with electrocatalysts are key components of photoelectrochemical (PEC) energy conversion and storage systems. Such systems could provide a way to convert the energy in sunlight directly into energy stored in a fuel like hydrogen gas to power our modern society without using fossil fuels. Despite an intense effort aimed at optimizing these materials, there has been little systematic work focused on the semiconductor-electrocatalyst (SC|EC) interface. The SC|EC interface is important because it is responsible for collecting the photoexcited electron-hole pairs generated in the semiconductor. During the performance period we initiated a fundamental effort to understand interfacial electron transfer between electrocatalysts and bulk semiconductors. We developed an experimental technique, dual-working-electrode (DWE) photoelectrochemistry, allowing for direct electrical measurement of the SC-EC interface in situ. We also developed the first theory of the SC|EC interface and applied the theory through numerical simulation to explain the measured interfacial charge transfer properties of the SC|EC junction. We discovered that porous, ion-permeable, redox-active catalysts such as Ni-(Fe) oxyhydroxides form so-called “adaptive” junctions where the effective interfacial barrier height for electron transfer depends on the charge state of the catalyst. This is in sharp contrast to interface properties of dense ion-impermeable catalysts, which we found form buried junctions that could be described by simple equivalent electrical circuits. These results elucidated a design principle for catalyzed photoelectrodes - high-performance photoelectrodes with direct SC|EC junctions use soft deposition techniques that yield ion-permeable catalysts. This work thus provides a foundation for the development of improved photoelectrodes that are practically relevant because they provide a mechanism to directly convert and store solar energy in the form

  17. Development of ruthenium-based bimetallic electrocatalysts for oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Liu, Lingyun; Lee, Jong-Won; Popov, Branko N.

    Ruthenium-based bimetallic electrocatalysts with non-noble metals such as Ti, Cr, Fe, Co and Pb were synthesized on a porous carbon support using a chelation process. Rotating ring disk electrode measurements indicated that RuFeN x/C showed the catalytic activity and selectivity toward the four-electron reduction of oxygen to water comparable to those of the conventional Pt/C catalysts. The performance of the membrane-electrode assembly prepared with the RuFeN x/C cathode catalyst was evaluated for 150 h of continuous operation.

  18. Nanostructured electrocatalyst for fuel cells : silica templated synthesis of Pt/C composites.

    SciTech Connect

    Stechel, Ellen Beth; Switzer, Elise E.; Fujimoto, Cy H.; Atanassov, Plamen Borissov; Cornelius, Christopher James; Hibbs, Michael R.

    2007-09-01

    Platinum-based electrocatalysts are currently required for state-of-the-art fuel cells and represent a significant portion of the overall fuel cell cost. If fuel cell technology is to become competitive with other energy conversion technologies, improve the utilization of precious metal catalysts is essential. A primary focus of this work is on creating enhanced nanostructured materials which improve precious-metal utilization. The goal is to engineer superior electrocatalytic materials through the synthesis, development and investigation of novel templated open frame structures synthesized in an aerosol-based approach. Bulk templating methods for both Pt/C and Pt-Ru composites are evaluated in this study and are found to be limited due to the fact that the nanostructure is not maintained throughout the entire sample. Therefore, an accurate examination of structural effects was previously impossible. An aerosol-based templating method of synthesizing nanostructured Pt-Ru electrocatalysts has been developed wherein the effects of structure can be related to electrocatalytic performance. The aerosol-based templating method developed in this work is extremely versatile as it can be conveniently modified to synthesize alternative materials for other systems. The synthesis method was able to be extended to nanostructured Pt-Sn for ethanol oxidation in alkaline media. Nanostructured Pt-Sn electrocatalysts were evaluated in a unique approach tailored to electrocatalytic studies in alkaline media. At low temperatures, nanostructured Pt-Sn electrocatalysts were found to have significantly higher ethanol oxidation activity than a comparable nanostructured Pt catalyst. At higher temperatures, the oxygen-containing species contribution likely provided by Sn is insignificant due to a more oxidized Pt surface. The importance of the surface coverage of oxygen-containing species in the reaction mechanism is established in these studies. The investigations in this work present

  19. An ultrastable bimetallic carbide as platinum electrocatalyst support for highly active oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Yan, Zaoxue; Zhang, Mingmei; Xie, Jimin; Shen, Pei Kang

    2015-11-01

    Stable bimetallic carbide (Fe2MoC) with graphitized carbon (GC) as matrix has been synthesized through an ion-exchange method. The Pt nanoparticles are loaded on the GC-Fe2MoC composite to form Pt/GC-Fe2MoC electrocatalyst which shows much higher activity and stability than those of commercial Pt/C for oxygen reduction reaction in acidic media. The excellent performances of Pt/GC-Fe2MoC are mainly due to the inherent stability of GC-Fe2MoC and the promotion effect between Fe2MoC and Pt.

  20. Tuning the surface structure of supported PtNi(x) bimetallic electrocatalysts for the methanol electro-oxidation reaction.

    PubMed

    Zhang, Bingsen; Niu, Yiming; Xu, Junyuan; Pan, Xiaoli; Chen, Cheng-Meng; Shi, Wen; Willinger, Marc-Georg; Schlögl, Robert; Su, Dang Sheng

    2016-03-11

    The structures of PtNix nanoalloy particles were modified through thermal annealing in different atmospheres. The evolution of surface structures was uncovered by advanced transmission electron microscopy, and the structure-function correlation in methanol electro-oxidation was probed. It provided new insights into the design and synthesis of highly efficient electrocatalysts. PMID:26871308

  1. Metal-Carbon Hybrid Electrocatalysts Derived from Ion-Exchange Resin Containing Heavy Metals for Efficient Hydrogen Evolution Reaction.

    PubMed

    Zhou, Yucheng; Zhou, Weijia; Hou, Dongman; Li, Guoqiang; Wan, Jinquan; Feng, Chunhua; Tang, Zhenghua; Chen, Shaowei

    2016-05-01

    Transition metal-carbon hybrids have been proposed as efficient electrocatalysts for hydrogen evolution reaction (HER) in acidic media. Herein, effective HER electrocatalysts based on metal-carbon composites are prepared by controlled pyrolysis of resin containing a variety of heavy metals. For the first time, Cr2 O3 nanoparticles of 3-6 nm in diameter homogeneously dispersed in the resulting porous carbon framework (Cr-C hybrid) is synthesized as efficient HER electrocatalyst. Electrochemical measurements show that Cr-C hybrids display a high HER activity with an onset potential of -49 mV (vs reversible hydrogen electrode), a Tafel slope of 90 mV dec(-1) , a large catalytic current density of 10 mA cm(-2) at -123 mV, and the prominent electrochemical durability. X-ray photoelectron spectroscopic measurements confirm that electron transfer occurs from Cr2 O3 into carbon, which is consistent with the reported metal@carbon systems. The obtained correlation between metals and HER activities may be exploited as a rational guideline in the design and engineering of HER electrocatalysts. PMID:27061759

  2. Metallic Co4N Porous Nanowire Arrays Activated by Surface Oxidation as Electrocatalysts for the Oxygen Evolution Reaction.

    PubMed

    Chen, Pengzuo; Xu, Kun; Fang, Zhiwei; Tong, Yun; Wu, Junchi; Lu, Xiuli; Peng, Xu; Ding, Hui; Wu, Changzheng; Xie, Yi

    2015-12-01

    Designing highly efficient electrocatalysts for oxygen evolution reaction (OER) plays a key role in the development of various renewable energy storage and conversion devices. In this work, we developed metallic Co4N porous nanowire arrays directly grown on flexible substrates as highly active OER electrocatalysts for the first time. Benefiting from the collaborative advantages of metallic character, 1D porous nanowire arrays, and unique 3D electrode configuration, surface oxidation activated Co4N porous nanowire arrays/carbon cloth achieved an extremely small overpotential of 257 mV at a current density of 10 mA cm(-2), and a low Tafel slope of 44 mV dec(-1) in an alkaline medium, which is the best OER performance among reported Co-based electrocatalysts to date. Moreover, in-depth mechanistic investigations demonstrate the active phases are the metallic Co4N core inside with a thin cobalt oxides/hydroxides shell during the OER process. Our finding introduces a new concept to explore the design of high-efficiency OER electrocatalysts. PMID:26437900

  3. Characterizing structural overpotentials for bubble evolution on nanostructured semiconductor-electrocatalyst interfaces

    NASA Astrophysics Data System (ADS)

    Coridan, Robert H.

    Nanostructured electrocatalysts can improve the kinetics of solar-driven photocatalysis at a semiconductor-liquid junction while minimizing the effect on the energetics of that junction. A relevant example is Pt-decorated Si electrodes for hydrogen evolution from water splitting. Nanostructuring can also impair the reaction kinetics by introducing mass transport overpotentials. For reactions that evolve gas, the active surface area can be blocked by bubbles on discrete catalytic sites, possibly halting the reaction entirely. Here, we explore these issues by measuring the high-frequency dynamics of bubbles evolved from nanostructured electrocatalysts at a semiconductor-electrolyte interface. Using transmission x-ray phase contrast microscopy, we can image gas-evolving reactions as a way to directly measure the effects of adhesion, catalyst structure, and buoyancy on the reaction kinetics. From these measurements, we develop a model for electrolytic bubble evolution and transport that considers coalescence on neighboring sites, surface interactions, and the non-equilibrium shape dynamics of bubbles. This model can be used to identify favorable catalyst motifs that promote bubble clearance and mitigate their influence on reaction kinetics for water splitting applications.

  4. Gold-doped graphene: A highly stable and active electrocatalysts for the oxygen reduction reaction

    SciTech Connect

    Stolbov, Sergey Alcántara Ortigoza, Marisol

    2015-04-21

    In addressing the growing need of renewable and sustainable energy resources, hydrogen-fuel-cells stand as one of the most promising routes to transform the current energy paradigm into one that integrally fulfills environmental sustainability. Nevertheless, accomplishing this technology at a large scale demands to surpass the efficiency and enhance the cost-effectiveness of platinum-based cathodes, which catalyze the oxygen reduction reaction (ORR). In this work, our first-principles calculations show that Au atoms incorporated into graphene di-vacancies form a highly stable and cost-effective electrocatalyst that is, at the same time, as or more (dependently of the dopant concentration) active toward ORR than the best-known Pt-based electrocatalysts. We reveal that partial passivation of defected-graphene by gold atoms reduces the reactivity of C dangling bonds and increases that of Au, thus optimizing them for catalyzing the ORR and yielding a system of high thermodynamic and electrochemical stabilities. We also demonstrate that the linear relation among the binding energies of the reaction intermediates assumed in computational high-throughput material screening does not hold, at least for this non-purely transition-metal material. We expect Au-doped graphene to finally overcome the cathode-related challenge hindering the realization of hydrogen-fuel cells as the leading means of powering transportation and portable devices.

  5. Development of gold electrocatalysts for alkaline media. Final report on phase 2

    SciTech Connect

    Taylor, E.J.

    1992-04-01

    A research program for the development of carbon-based gold electrode technologies for oxygen reduction in alkali media was conducted. A Phase I feasibility study established very favorable oxygen reduction kinetics on the Au(100) surface and developed a fabrication technique for producing small (less than 20A), highly dispersed gold electrocatalysts. The Phase II program consisted of two parts: (1) development of small, highly dispersed supported gold electrocatalysts and development of corrosion resistant support material for chlor-alkali applications, and (2) development of low-cost, high performance gold electrodes for a commercial oxygen gas sensor. For the oxygen sensor application, thirty electrodes, demonstrated for a period of six months, passed all performance criteria. The chlor-alkali applications included three fuel cell derived technologies: (1) fuel cell, (2) electrochemical concentrator, and (3) air-depolarized cell. Researchers investigated the effect of carbon support, gold catalyst content, and catalyst heat treatment temperature on electrode performance. An economic analysis of each of these technologies incorporated at a chlor-alkali facility was conducted.

  6. Recent Advances in Inorganic Heterogeneous Electrocatalysts for Reduction of Carbon Dioxide.

    PubMed

    Zhu, Dong Dong; Liu, Jin Long; Qiao, Shi Zhang

    2016-05-01

    In view of the climate changes caused by the continuously rising levels of atmospheric CO2 , advanced technologies associated with CO2 conversion are highly desirable. In recent decades, electrochemical reduction of CO2 has been extensively studied since it can reduce CO2 to value-added chemicals and fuels. Considering the sluggish reaction kinetics of the CO2 molecule, efficient and robust electrocatalysts are required to promote this conversion reaction. Here, recent progress and opportunities in inorganic heterogeneous electrocatalysts for CO2 reduction are discussed, from the viewpoint of both experimental and computational aspects. Based on elemental composition, the inorganic catalysts presented here are classified into four groups: metals, transition-metal oxides, transition-metal chalcogenides, and carbon-based materials. However, despite encouraging accomplishments made in this area, substantial advances in CO2 electrolysis are still needed to meet the criteria for practical applications. Therefore, in the last part, several promising strategies, including surface engineering, chemical modification, nanostructured catalysts, and composite materials, are proposed to facilitate the future development of CO2 electroreduction. PMID:26996295

  7. Hierarchically porous carbons with optimized nitrogen doping as highly active electrocatalysts for oxygen reduction

    NASA Astrophysics Data System (ADS)

    Liang, Hai-Wei; Zhuang, Xiaodong; Brüller, Sebastian; Feng, Xinliang; Müllen, Klaus

    2014-09-01

    Development of efficient, low-cost and stable electrocatalysts as the alternative to platinum for the oxygen reduction reaction is of significance for many important electrochemical devices, such as fuel cells, metal-air batteries and chlor-alkali electrolysers. Here we report a highly active nitrogen-doped, carbon-based, metal-free oxygen reduction reaction electrocatalyst, prepared by a hard-templating synthesis, for which nitrogen-enriched aromatic polymers and colloidal silica are used as precursor and template, respectively, followed by ammonia activation. Our protocol allows for the simultaneous optimization of both porous structures and surface functionalities of nitrogen-doped carbons. Accordingly, the prepared catalysts show the highest oxygen reduction reaction activity (half-wave potential of 0.85 V versus reversible hydrogen electrode with a low loading of 0.1 mg cm-2) in alkaline media among all reported metal-free catalysts. Significantly, when used for constructing the air electrode of zinc-air battery, our metal-free catalyst outperforms the state-of the-art platinum-based catalyst.

  8. Hierarchically porous carbons with optimized nitrogen doping as highly active electrocatalysts for oxygen reduction.

    PubMed

    Liang, Hai-Wei; Zhuang, Xiaodong; Brüller, Sebastian; Feng, Xinliang; Müllen, Klaus

    2014-01-01

    Development of efficient, low-cost and stable electrocatalysts as the alternative to platinum for the oxygen reduction reaction is of significance for many important electrochemical devices, such as fuel cells, metal-air batteries and chlor-alkali electrolysers. Here we report a highly active nitrogen-doped, carbon-based, metal-free oxygen reduction reaction electrocatalyst, prepared by a hard-templating synthesis, for which nitrogen-enriched aromatic polymers and colloidal silica are used as precursor and template, respectively, followed by ammonia activation. Our protocol allows for the simultaneous optimization of both porous structures and surface functionalities of nitrogen-doped carbons. Accordingly, the prepared catalysts show the highest oxygen reduction reaction activity (half-wave potential of 0.85 V versus reversible hydrogen electrode with a low loading of 0.1 mg cm(-2)) in alkaline media among all reported metal-free catalysts. Significantly, when used for constructing the air electrode of zinc-air battery, our metal-free catalyst outperforms the state-of the-art platinum-based catalyst. PMID:25229121

  9. Carbon monoxide tolerant platinum electrocatalysts on niobium doped titania and carbon nanotube composite supports

    NASA Astrophysics Data System (ADS)

    Rigdon, William A.; Huang, Xinyu

    2014-12-01

    In the anode of electrochemical cells operating at low temperature, the hydrogen oxidation reaction is susceptible to poisoning from carbon monoxide (CO) which strongly adsorbs on platinum (Pt) catalysts and increases activation overpotential. Adsorbed CO is removed by oxidative processes such as electrochemical stripping, though cleaning can also cause corrosion. One approach to improve the tolerance of Pt is through alloying with less-noble metals, but the durability of alloyed electrocatalysts is a critical concern. Without sacrificing stability, tolerance can be improved by careful design of the support composition using metal oxides. The bifunctional mechanism is promoted at junctions of the catalyst and metal oxides used in the support. Stable metal oxides can also form strong interactions with catalysts, as is the case for platinum on titania (TiOx). In this study, niobium (Nb) serves as an electron donor dopant in titania. The transition metal oxides are joined to functionalized multi-wall carbon nanotube (CNT) supports in order to synthesize composite supports. Pt is then deposited to form electrocatalysts which are characterized before fabrication into anodes for tests as an electrochemical hydrogen pump. Comparisons are made between the control from Pt-CNT to Pt-TiOx-CNT and Pt-Ti0.9Nb0.1Ox-CNT in order to demonstrate advantages.

  10. Blending Cr2O3 into a NiO-Ni electrocatalyst for sustained water splitting.

    PubMed

    Gong, Ming; Zhou, Wu; Kenney, Michael James; Kapusta, Rich; Cowley, Sam; Wu, Yingpeng; Lu, Bingan; Lin, Meng-Chang; Wang, Di-Yan; Yang, Jiang; Hwang, Bing-Joe; Dai, Hongjie

    2015-10-01

    The rising H2 economy demands active and durable electrocatalysts based on low-cost, earth-abundant materials for water electrolysis/photolysis. Here we report nanoscale Ni metal cores over-coated by a Cr2 O3 -blended NiO layer synthesized on metallic foam substrates. The Ni@NiO/Cr2 O3 triphase material exhibits superior activity and stability similar to Pt for the hydrogen-evolution reaction in basic solutions. The chemically stable Cr2 O3 is crucial for preventing oxidation of the Ni core, maintaining abundant NiO/Ni interfaces as catalytically active sites in the heterostructure and thus imparting high stability to the hydrogen-evolution catalyst. The highly active and stable electrocatalyst enables an alkaline electrolyzer operating at 20 mA cm(-2) at a voltage lower than 1.5 V, lasting longer than 3 weeks without decay. The non-precious metal catalysts afford a high efficiency of about 15 % for light-driven water splitting using GaAs solar cells. PMID:26307213

  11. A biosynthetic model of cytochrome c oxidase as an electrocatalyst for oxygen reduction.

    PubMed

    Mukherjee, Sohini; Mukherjee, Arnab; Bhagi-Damodaran, Ambika; Mukherjee, Manjistha; Lu, Yi; Dey, Abhishek

    2015-01-01

    Creating an artificial functional mimic of the mitochondrial enzyme cytochrome c oxidase (CcO) has been a long-term goal of the scientific community as such a mimic will not only add to our fundamental understanding of how CcO works but may also pave the way for efficient electrocatalysts for oxygen reduction in hydrogen/oxygen fuel cells. Here we develop an electrocatalyst for reducing oxygen to water under ambient conditions. We use site-directed mutants of myoglobin, where both the distal Cu and the redox-active tyrosine residue present in CcO are modelled. In situ Raman spectroscopy shows that this catalyst features very fast electron transfer rates, facile oxygen binding and O-O bond lysis. An electron transfer shunt from the electrode circumvents the slow dissociation of a ferric hydroxide species, which slows down native CcO (bovine 500 s(-1)), allowing electrocatalytic oxygen reduction rates of 5,000 s(-1) for these biosynthetic models. PMID:26455726

  12. A biosynthetic model of cytochrome c oxidase as an electrocatalyst for oxygen reduction

    PubMed Central

    Mukherjee, Sohini; Mukherjee, Arnab; Bhagi-Damodaran, Ambika; Mukherjee, Manjistha; Lu, Yi; Dey, Abhishek

    2015-01-01

    Creating an artificial functional mimic of the mitochondrial enzyme cytochrome c oxidase (CcO) has been a long-term goal of the scientific community as such a mimic will not only add to our fundamental understanding of how CcO works but may also pave the way for efficient electrocatalysts for oxygen reduction in hydrogen/oxygen fuel cells. Here we develop an electrocatalyst for reducing oxygen to water under ambient conditions. We use site-directed mutants of myoglobin, where both the distal Cu and the redox-active tyrosine residue present in CcO are modelled. In situ Raman spectroscopy shows that this catalyst features very fast electron transfer rates, facile oxygen binding and O–O bond lysis. An electron transfer shunt from the electrode circumvents the slow dissociation of a ferric hydroxide species, which slows down native CcO (bovine 500 s−1), allowing electrocatalytic oxygen reduction rates of 5,000 s−1 for these biosynthetic models. PMID:26455726

  13. A new electrocatalyst and its application method for vanadium redox flow battery

    NASA Astrophysics Data System (ADS)

    Wei, Guanjie; Jing, Minghua; Fan, Xinzhuang; Liu, Jianguo; Yan, Chuanwei

    2015-08-01

    The edge plane in carbon structure has good electrocatalytic activity toward vanadium redox reaction. To apply it in vanadium redox flow battery (VRFB) practically, the graphite nanopowders (GNPs) containing amounts of edge planes are used as electrocatalyst and embedded in the electrospun carbon nanofibers (ECNFs) by different mass ratios to make composite electrodes. The morphology and electrochemical activity of the GNPs and the composite electrodes containing them are characterized. Compared with the pristine ECNFs, the composite electrodes show much higher electrochemical activity. With the increase of GNPs content in composite electrodes, the electrochemical reversibility of the vanadium redox couples also increases. It proves the addition of GNPs can surely improve the electrochemical activity of ECNFs. Among the composite electrodes, the ECNFs containing 30 nm GNP by mass ratio of 1:50 show the best electrochemical activity, largest active surface area and excellent stability. Due to the high performance of GNP/ECNFs composite electrode and its relatively low cost preparation process, the GNPs are expected to be used as electrocatalyst in VRFB on a large scale to improve the cell performance.

  14. Vanadium carbide and graphite promoted Pd electrocatalyst for ethanol oxidation in alkaline media

    NASA Astrophysics Data System (ADS)

    Yan, Zaoxue; Zhang, Mingmei; Xie, Jimin; Shen, Pei Kang

    2013-12-01

    The vanadium carbide particles with the diameter of 1-3 nm on graphitized resin (GC-V8C7) are synthesized through ionic exchange process. The materials are characterized by XRD, Raman, TEM, SEM and EDS measurements. The results prove that the ion-exchange resin as both carbon source and dispersion media favors the formation of very uniform and small (1-3 nm) V8C7 particles, and protect the V8C7 from conglomeration even at the temperature of 1500 °C. Meanwhile, the vanadium compound is found efficient catalytic effect on graphitization of ion-exchange resin, leading to high graphitization degree of GC-V8C7. Pd particles are loaded on the GC-V8C7 materials as electrocatalyst (Pd/GC-V8C7) for ethanol oxidation in alkaline media. The cyclic voltammograms measurements show that both V8C7 and GC (graphitized ion-exchange resin) give Pd electrocatalyst improved catalytic performance in activity, stability and overpotential, compared with that of Pd supporting on Vulcan XC-72 carbon (Pd/C). The present synthesizing method of GC-V8C7 is simple and effective, which can be readily scaled up for mass production of other nanomaterials.

  15. Advanced Evaluation of the Long-Term Stability of Oxygen Evolution Electrocatalysts.

    PubMed

    Maljusch, Artjom; Conradi, Oliver; Hoch, Sascha; Blug, Matthias; Schuhmann, Wolfgang

    2016-08-01

    Evaluation of the long-term stability of electrocatalysts is typically performed using galvanostatic polarization at a predefined current density. A stable or insignificant increase in the applied potential is usually interpreted as high long-term stability of the tested catalyst. However, effects such as (i) electrochemical degradation of a catalyst due to its oxidation, (ii) blocking of the catalyst surface by evolved gas bubbles, and (iii) detachment of the catalyst from the electrode surface may lead to a decrease of the catalyst's active surface area being exposed to the electrolyte. In order to separate these effects and to evaluate the true electrochemical degradation of electrocatalysts, an advanced evaluation protocol based on subsequently performed electrochemical impedance, double layer capacitance, cyclic voltammetry, and galvanostatic polarization measurements was developed and used to evaluate the degradation of IrO2 particles drop-coated on glassy carbon rotating disk electrode using Nafion as a binder. A flow-through electrochemical cell was developed enabling circulation of the electrolyte leading to an efficient removal of evolved oxygen bubbles even at high current densities of up to 250 mA/cm(2). The degradation rate of IrO2 was evaluated over 225 test cycles (0.733 ± 0.022 mV/h) with a total duration of galvanostatic polarization measurements of over 55 h. PMID:27398712

  16. Nanostructured F doped IrO2 electro-catalyst powders for PEM based water electrolysis

    NASA Astrophysics Data System (ADS)

    Kadakia, Karan Sandeep; Jampani, Prashanth H.; Velikokhatnyi, Oleg I.; Datta, Moni Kanchan; Park, Sung Kyoo; Hong, Dae Ho; Chung, Sung Jae; Kumta, Prashant N.

    2014-12-01

    Fluorine doped iridium oxide (IrO2:F) powders with varying F content ranging from 0 to 20 wt.% has been synthesized by using a modification of the Adams fusion method. The precursors (IrCl4 and NH4F) are mixed with NaNO3 and heated to elevated temperatures to form high surface area nanomaterials as electro-catalysts for PEM based water electrolysis. The catalysts were then coated on a porous Ti substrate and have been studied for the oxygen evolution reaction in PEM based water electrolysis. The IrO2:F with an optimum composition of IrO2:10 wt.% F shows remarkably superior electrochemical activity and chemical stability compared to pure IrO2. The results have also been supported via kinetic studies by conducting rotating disk electrode (RDE) experiments. The RDE studies confirm that the electro-catalysts follow the two electron transfer reaction for electrolysis with calculated activation energy of ∼25 kJ mol-1. Single full cell tests conducted also validate the superior electrochemical activity of the 10 wt.% F doped IrO2.

  17. Gram-Scale-Synthesized Pd2Co-Supported Pt Monolayer Electrocatalysts for Oxygen Reduction Reaction

    SciTech Connect

    Zhou, W.; Sasaki, K; Su, D; Zhu, Y; Wang, J; Adzic, R

    2010-01-01

    Gram-scale synthesis of Pt{sub ML} electrocatalysts with a well-defined core-shell structure has been carried out using method involving galvanic displacement of an underpotential deposition Cu layer. The Pt shell thickness can be controlled by stepwise deposition. The Pt{at}Pd{sub 2}Co/C nanoparticles were characterized by X-ray powder diffraction, aberration-corrected scanning transmission electron microscopy, high-resolution energy-loss spectrometry, and in situ X-ray absorption spectroscopy. A complete Pt shell of 0.6 nm on a Pd{sub 2}Co core has been confirmed. The Pt{at}Pd{sub 2}Co/C core-shell electrocatalysts showed a very high activity for the oxygen reduction reaction; the Pt mass and specific activity were 0.72 A mg{sub Pt}{sup -1} and 0.5 mA cm{sup -2}, respectively (3.5 and 2.5 times higher than the corresponding values for commercial Pt catalysts), at 0.9 V in 0.1 M HClO{sub 4} at room temperature. In an accelerated potential cycling test, a loss in active surface area and a decrease in catalytic activity for gram-scale-synthesized Pt{sub ML} catalysts were also determined.

  18. Cobalt Phosphide Hollow Polyhedron as Efficient Bifunctional Electrocatalysts for the Evolution Reaction of Hydrogen and Oxygen.

    PubMed

    Liu, Mengjia; Li, Jinghong

    2016-01-27

    The development of efficient and low-cost hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) electrocatalysts for renewable-energy conversion techniques is highly desired. A kind of hollow polyhedral cobalt phosphide (CoP hollow polyhedron) is developed as efficient bifunctional electrocatalysts for HER and OER templated by Co-centered metal-organic frameworks. The as-prepared CoP hollow polyhedron, which have large specific surface area and high porosity providing rich catalytic active sites, show excellent electrocatalytic performances for both HER and OER in acidic and alkaline media, respectively, with onset overpotentials of 35 and 300 mV, Tafel slopes of 59 and 57 mV dec(-1), and a current density of 10 mA cm(-2) at overpotentials of 159 and 400 mV for HER and OER, respectively, which are remarkably superior to those of particulate CoP (CoP particles) and comparable to those of commercial noble-metal catalysts. In addition, the CoP hollow polyhedron also show good durability after long-term operations. PMID:26711014

  19. Blending Cr2O3 into a NiO-Ni electrocatalyst for sustained water splitting

    DOE PAGESBeta

    Gong, Ming; Zhou, Wu; Kenney, Michael James; Kapusta, Rich; Cowley, Sam; Wu, Yingpeng; Lu, Bingan; Lin, Meng -Chang; Wang, Di -Yan; Yang, Jiang; et al

    2015-08-24

    The rising H2 economy demands active and durable electrocatalysts based on low-cost, earth-abundant materials for water electrolysis/photolysis. Here we report nanoscale Ni metal cores over-coated by a Cr2O3-blended NiO layer synthesized on metallic foam substrates. The Ni@NiO/Cr2O3 triphase material exhibits superior activity and stability similar to Pt for the hydrogen-evolution reaction in basic solutions. The chemically stable Cr2O3 is crucial for preventing oxidation of the Ni core, maintaining abundant NiO/Ni interfaces as catalytically active sites in the heterostructure and thus imparting high stability to the hydrogen-evolution catalyst. The highly active and stable electrocatalyst enables an alkaline electrolyzer operating at 20more » mA cm–2 at a voltage lower than 1.5 V, lasting longer than 3 weeks without decay. Thus, the non-precious metal catalysts afford a high efficiency of about 15 % for light-driven water splitting using GaAs solar cells.« less

  20. Carbon-Free Electrocatalyst for Oxygen Reduction and Oxygen Evolution Reactions.

    PubMed

    Yang, Yang; Fei, Huilong; Ruan, Gedeng; Li, Lei; Wang, Gunuk; Kim, Nam Dong; Tour, James M

    2015-09-23

    A nanoporous Ag-embedded SnO2 thin film was fabricated by anodic treatment of electrodeposited Ag-Sn alloy layers. The ordered nanoporous structure formed by anodization played a key role in enhancing the electrocatalytic performance of the Ag-embedded SnO2 layer in several ways: (1) the roughness factor of the thin film is greatly increased from 23 in the compact layer to 145 in the nanoporous layer, creating additional active sites that are involved in oxygen electrochemical reactions; (2) a trace amount of Ag (∼1.7 at %, corresponding to a Ag loading of ∼3.8 μg cm(-2)) embedded in the self-organized SnO2 nanoporous matrix avoids the agglomeration of nanoparticles, which is a common problem leading to the electrocatalyst deactivation; (3) the fabricated nanoporous thin film is active without additional additives or porous carbon that is usually necessary to support and stabilize the electrocatalyst. More importantly, the Ag-embedded SnO2 nanoporous thin film shows outstanding bifunctional oxygen electrochemical performance (oxygen reduction and evolution reactions) that is considered a promising candidate for use in metal-air batteries. The present technique has a wide range of applications for the preparation of other carbon-free electrocatalytic nanoporous films that could be useful for renewable energy production and storage applications. PMID:26320368

  1. Bimetallic electrocatalysts on titanium dioxide-based supports for methanol oxidation and oxygen evolution

    NASA Astrophysics Data System (ADS)

    Fuentes, Roderick Eliel

    Electrocatalysts are essential for the development of active and durable fuel cells and hydrogen production technologies. Generally, electrochemical processes of energy conversion and hydrogen generation in a Proton Exchange Membrane (PEM) utilize precious metals, such as platinum, iridium and ruthenium, as electrocatalysts. For the methanol oxidation and oxygen evolution reaction, a bimetallic structure can be used to enhance kinetics and increase stability. It is desired to support electrocatalysts to disperse nanoparticles on the surface and promote better catalyst utilization. Traditionally, carbon has been used as an electrochemical support because it has a high surface area and high electrical conductivity. The problem with carbon is that it is not a very stable material and can corrode at voltages more than 0.9 V, affecting performance of the electrochemical reaction. Therefore, it would be useful to support electrocatalysts in a stable material with suitable conductivity. Using titanium dioxide as a support can be advantageous due to its corrosion-resistant capability. TiO2 exhibit different crystalline structures, such as anatase and rutile, which can have an effect on catalytic activity. Unfortunately, it is not conductive; hence, it is not used in electrochemical applications. However, it can be doped with niobium to increase electronic conductivity; but, it usually come at the expense of surface area. In this work, TiO 2 and Nb-TiO2 were studied as platinum/ruthenium and iridium/ruthenium nanoparticles supports for the electrochemical oxidation of methanol and oxygen evolution, respectively. Even though the conductivity of our supports was very low, adding a considerable loading of nanoparticles increased conductivity of the composite material (support + catalyst) to acceptable levels. Using cyclic voltammetry (CV) and direct methanol fuel cell tests creating a membrane electrode assembly (MEA), Pt-Ru supported on Nb-TiO2 and TiO 2 showed superior

  2. A Highly-Durable CO-Tolerant Poly(vinylphosphonic acid)-Coated Electrocatalyst Supported on a Nanoporous Carbon.

    PubMed

    Yang, Zehui; Moriguchi, Isamu; Nakashima, Naotoshi

    2016-04-13

    For direct methanol fuel cells (DMFCs) to be commercialized, the durability of the anodic electrocatalyst needs to be highly considered, especially under high temperature and methanol concentration conditions. Low durability caused by carbon corrosion as well as carbon monoxide (CO) poisoning of the platinum nanoparticles (Pt-NP) leads to a decrease in active Pt-NPs and increases inactive Pt-NPs covered by CO species. In this study, we deposited Pt-NPs on poly[2,2'-(2,6-pyridine)-5,5'-bibenzimidazole] (PyPBI)-wrapped nanoporous carbon (NanoPC) and coated the as-synthesized electrocatalyst with poly(vinylphosphonic acid) (PVPA). The durability of the as-synthesized NanoPC/PyPBI/Pt/PVPA was tested in 0.1 M HClO4 electrolyte at 60 °C by cycling the potential from 1.0 to 1.5 V relative to RHE, and the results indicated that NanoPC/PyPBI/Pt/PVPA showed ∼5 times better durability relative to that of the commercial CB/Pt. The methanol oxidation reaction (MOR) of the electrocatalyst was tested before and after the potential cycling in the presence of 4 or 8 M methanol at 60 °C and found that the CO tolerance of the electrocatalyst was ∼3 times higher than that of the commercial CB/Pt. Such a higher CO tolerance is due to the coating of the PVPA, which was proven by an EDX mapping measurement. The NanoPC/PyPBI/Pt/PVPA showed a high durability and CO tolerance under high temperature and high methanol concentration conditions, indicating that the electrocatalyst could be used in real fuel applications. PMID:26807598

  3. SYNTHESIS AND CHARACTERIZATION OF CO-AND H2S-TOLERANT ELECTROCATALYSTS FOR PEM FUEL CELL

    SciTech Connect

    Shamsuddin Ilias

    2004-03-31

    The present state-of-art Proton Exchange Membrane Fuel Cell (PEMFC) technology is based on platinum (Pt) as a catalyst for both the fuel (anode) and air (cathode) electrodes. This catalyst is highly active but susceptible to poisoning by CO, which may be present in the H{sub 2}-fuel used or may be introduced during the fuel processing. Presence of trace amount of CO and H{sub 2}S in the H{sub 2}-fuel poisons the anode irreversibly and decreases the performance of the PEMFCs. In an effort to reduce the Pt-loading and improve the PEMFC performance, we propose to synthesize a number of Pt-based binary, ternary, and quaternary electrocatalysts using Ru, Mo, Ir, Ni, and Co as a substitute for Pt. By fine-tuning the metal loadings and compositions of candidate electrocatalysts, we plan to minimize the cost and optimize the catalyst activity and performance in PEMFC. The feasibility of the novel electrocatalysts will be demonstrated in the proposed effort with gas phase CO and H{sub 2}S concentrations typical of those found in reformed fuel gas with coal/natural gas/methanol feedstocks. During this reporting period several bi-metallic electrocatalysts were synthesized and tested in MEAs. From Galvonstatic study the catalytic activity was found in the order of: Pt/Ru/C > Pt/Mo/C > Pt/Ir/C > Pt/Ni/C > Pt/Cr/C. Work in progress to further study these catalysts for CO-tolerance in PEMFC and identify potential candidate metals for synthesis of trimetallic electrocatalysts.

  4. SYNTHESIS AND CHARACTERIZATION OF CO- AND H{sub 2}S-TOLERANT ELECTROCATALYSTS FOR PEM FUEL CELL

    SciTech Connect

    Shamsuddin Ilias

    2005-04-05

    The present state-of-art Proton Exchange Membrane Fuel Cell (PEMFC) technology is based on platinum (Pt) as a catalyst for both the fuel (anode) and air (cathode) electrodes. This catalyst is highly active but susceptible to poisoning by CO, which may be present in the H{sub 2}-fuel used or may be introduced during the fuel processing. Presence of trace amount of CO and H{sub 2}S in the H{sub 2}-fuel poisons the anode irreversibly and decreases the performance of the PEMFCs. In an effort to reduce the Pt-loading and improve the PEMFC performance, we propose to synthesize a number of Pt-based binary, ternary, and quaternary electrocatalysts using Ru, Mo, Ir, Ni, and Co as a substitute for Pt. By fine-tuning the metal loadings and compositions of candidate electrocatalysts, we plan to minimize the cost and optimize the catalyst activity and performance in PEMFC. The feasibility of the novel electrocatalysts will be demonstrated in the proposed effort with gas phase CO and H{sub 2}S concentrations typical of those found in reformed fuel gas with coal/natural gas/methanol feedstocks. During this reporting period several tri-metallic electrocatalysts were synthesized using both ultra-sonication and conventional method. These catalysts (Pt/Ru/Mo, Pt/Ru/Ir, Pt/Ru/W, Ptr/Ru/Co, and Pt/Ru/Se on carbon) were tested in MEAs. From Galvonstatic study the catalytic activity was found in the order of: Pt/Ru/Mo/C > Pt/Ru/Ir/C > Pt/Ru/W/C > Ptr/Ru/Co/C > and Pt/Ru/Se. It appears that electrocatalysts prepared by ultra-sonication process are more active compared to the conventional technique. Work is in progress to further study these catalysts for CO-tolerance in PEMFC.

  5. A simple preparation of very high methanol tolerant cathode electrocatalyst for direct methanol fuel cell based on polymer-coated carbon nanotube/platinum

    PubMed Central

    Yang, Zehui; Nakashima, Naotoshi

    2015-01-01

    The development of a durable and methanol tolerant electrocatalyst with a high oxygen reduction reaction activity is highly important for the cathode side of direct methanol fuel cells. Here, we describe a simple and novel methodology to fabricate a practically applicable electrocatalyst with a high methanol tolerance based on poly[2,2′-(2,6-pyridine)-5,5′-bibenzimidazole]-wrapped multi-walled carbon nanotubes, on which Pt nanoparticles have been deposited, then coated with poly(vinylphosphonic acid) (PVPA). The polymer coated electrocatalyst showed an ~3.3 times higher oxygen reduction reaction activity compared to that of the commercial CB/Pt and methanol tolerance in the presence of methanol to the electrolyte due to a 50% decreased methanol adsorption on the Pt after coating with the PVPA. Meanwhile, the peroxide generation of the PVPA coated electrocatalyst was as low as 0.8% with 2 M methanol added to the electrolyte, which was much lower than those of the non-PVPA-coated electrocatalyst (7.5%) and conventional CB/Pt (20.5%). Such a high methanol tolerance is very important for the design of a direct methanol fuel cell cathode electrocatalyst with a high performance. PMID:26192397

  6. Bipolar Electrochemistry for Concurrently Evaluating the Stability of Anode and Cathode Electrocatalysts and the Overall Cell Performance during Long-Term Water Electrolysis.

    PubMed

    Eßmann, Vera; Barwe, Stefan; Masa, Justus; Schuhmann, Wolfgang

    2016-09-01

    Electrochemical efficiency and stability are among the most important characteristics of electrocatalysts. These parameters are usually evaluated separately for the anodic and cathodic half-cell reactions in a three-electrode system or by measuring the overall cell voltage between the anode and cathode as a function of current or time. Here, we demonstrate how bipolar electrochemistry can be exploited to evaluate the efficiency of electrocatalysts for full electrochemical water splitting while simultaneously and independently monitoring the individual performance and stability of the half-cell electrocatalysts. Using a closed bipolar electrochemistry setup, all important parameters such as overvoltage, half-cell potential, and catalyst stability can be derived from a single galvanostatic experiment. In the proposed experiment, none of the half-reactions is limiting on the other, making it possible to precisely monitor the contribution of the individual half-cell reactions on the durability of the cell performance. The proposed approach was successfully employed to investigate the long-term performance of a bifunctional water splitting catalyst, specifically amorphous cobalt boride (Co2B), and the durability of the electrocatalyst at the anode and cathode during water electrolysis. Additionally, by periodically alternating the polarization applied to the bipolar electrode (BE) modified with a bifunctional oxygen electrocatalyst, it was possible to explicitly follow the contributions of the oxygen reduction (ORR) and the oxygen evolution (OER) half-reactions on the overall long-term durability of the bifunctional OER/ORR electrocatalyst. PMID:27469162

  7. Fundamental study of nanostructured electro-catalysts with reduced noble metal content for PEM based water electrolysis

    NASA Astrophysics Data System (ADS)

    Kadakia, Sandeep Karan

    Identification and development of non-noble metal based electro-catalysts or electro-catalysts with significant reduction of expensive noble metal contents (E.g. IrO2, Pt) with comparable electrochemical performance as the standard noble metal/metal oxide for proton exchange membrane (PEM) based water electrolysis would constitute a major breakthrough in the generation of hydrogen by water electrolysis. Accomplishing such a system would not only result reduction of the overall capital costs of PEM based water electrolyzers, but also help attain the targeted hydrogen production cost [< $ 3.0 / gallon gasoline equivalent (gge)] comparable to conventional liquid fuels. In line with these goals, it was demonstrated that fluorine doped IrO 2 thin films and nanostructured high surface area powders display remarkably higher electrochemical activity, and comparable durability as pure IrO 2 electro-catalyst for the oxygen evolution reaction (OER) in PEM based water electrolysis. Furthermore, corrosion resistant SnO2 and NbO 2 support has been doped with F and coupled with IrO2 or RuO2 for use as an OER electro-catalyst. A solid solution of SnO 2:F or NbO2:F with only 20 - 30 mol.% IrO2 or RuO2 yielding a rutile structure in the form of thin films and bulk nanoparticles displays similar electrochemical activity and stability as pure IrO2/RuO2. This would lead to more than 70 mol.% reduction in the noble metal oxide content. Novel nanostructured ternary (Ir,Sn,Nb)O 2 thin films of different compositions have also been studied. It has been shown that (Ir0.40Sn0.30Nb 0.30)O2 shows similar electrochemical activity and enhanced chemical robustness as compared to pure IrO2. F doping of the ternary (Ir,Sn,Nb)O2 catalyst helps in further decreasing the noble metal oxide content of the catalyst. As a result, these reduced noble metal oxide catalyst systems would potentially be preferred as OER electro-catalysts for PEM electrolysis. The excellent performance of the catalysts coupled

  8. Highly branched platinum nanolance assemblies by polyallylamine functionalization as superior active, stable, and alcohol-tolerant oxygen reduction electrocatalysts

    NASA Astrophysics Data System (ADS)

    Fu, Gengtao; Jiang, Xian; Gong, Mingxing; Chen, Yu; Tang, Yawen; Lin, Jun; Lu, Tianhong

    2014-06-01

    The chemical functionalization of platinum (Pt) nanostructures is becoming a new trend in electrocatalysts designs. Meanwhile, highly branched Pt nanostructures are highly exciting electrocatalysts with high activity and stability owing to their specific physical and chemical properties. In this work, the polyallylamine (PAH) functionalized Pt nanolance assemblies (Pt NLAs) have been successfully synthesized by chemical reduction of PAH-PtII complex using formaldehyde (HCHO) in a two-phase water-complex system. The as-prepared Pt NLAs are highly branched and three-dimensionally (3D) interconnected nanostructures, which are composed of many long Pt nanolances in various directions. PAH functionalization improves the electrocatalytic activity of the Pt NLAs for an oxygen reduction reaction (ORR) because of high interface proton concentration on the Pt surface and excellent anti-oxidation ability of the Pt nanolances. Meanwhile, the PAH molecules bound on the Pt NLAs surface act as barrier networks to restrain accessibility of alcohol, exhibiting a high ORR selectivity. In addition, the PAH functionalized Pt NLAs show excellent durability for the ORR due to their particular 3D interconnected structure. The work demonstrates that the PAH functionalized Pt NLAs are indeed promising cathodic electrocatalysts for practical application in direct alcohol fuel cells.The chemical functionalization of platinum (Pt) nanostructures is becoming a new trend in electrocatalysts designs. Meanwhile, highly branched Pt nanostructures are highly exciting electrocatalysts with high activity and stability owing to their specific physical and chemical properties. In this work, the polyallylamine (PAH) functionalized Pt nanolance assemblies (Pt NLAs) have been successfully synthesized by chemical reduction of PAH-PtII complex using formaldehyde (HCHO) in a two-phase water-complex system. The as-prepared Pt NLAs are highly branched and three-dimensionally (3D) interconnected nanostructures

  9. Enabling direct H2O2 production through rational electrocatalyst design.

    PubMed

    Siahrostami, Samira; Verdaguer-Casadevall, Arnau; Karamad, Mohammadreza; Deiana, Davide; Malacrida, Paolo; Wickman, Björn; Escudero-Escribano, María; Paoli, Elisa A; Frydendal, Rasmus; Hansen, Thomas W; Chorkendorff, Ib; Stephens, Ifan E L S; Stephens, Ifan E; Rossmeisl, Jan

    2013-12-01

    Future generations require more efficient and localized processes for energy conversion and chemical synthesis. The continuous on-site production of hydrogen peroxide would provide an attractive alternative to the present state-of-the-art, which is based on the complex anthraquinone process. The electrochemical reduction of oxygen to hydrogen peroxide is a particularly promising means of achieving this aim. However, it would require active, selective and stable materials to catalyse the reaction. Although progress has been made in this respect, further improvements through the development of new electrocatalysts are needed. Using density functional theory calculations, we identify Pt-Hg as a promising candidate. Electrochemical measurements on Pt-Hg nanoparticles show more than an order of magnitude improvement in mass activity, that is, A g(-1) precious metal, for H2O2 production, over the best performing catalysts in the literature. PMID:24240242

  10. Radiation Effects on Platinum Nanostructured Electrocatalysts for Polymer Electrolyte Fuel Cells

    NASA Astrophysics Data System (ADS)

    Cemmi, A.; Paoletti, C.; Pozio, A.; Baccaro, S.; Giorgi, L.; Serra, E.

    2008-06-01

    Polymer Electrolyte Fuel Cells (PEFCs) offer low weight and high power density and are being considered for automotive and stationary power production besides space and electronic applications. In this work, gamma radiation effects on carbon materials (carbon powder and multiwalled carbon nanotubes) used as substrates in PEFCs electrodes, were studied. The enhancing of free radicals formation (especially on carbon powder) was observed and studied by EPR spectroscopy. This evidence leads to a significant activation of carbon materials because paramagnetic sites represent the preferential position for platinum electrocatalyst nucleation. Galvanostatic techniques were applied to deposits platinum nanoparticles on carbon substrates while FEG-SEM characterization and cyclic voltammetry (CV) were carried out to study the morphology and the electrochemical performances of PEFCs electrodes.

  11. Solution-processed PEDOT:PSS/graphene composites as the electrocatalyst for oxygen reduction reaction.

    PubMed

    Zhang, Miao; Yuan, Wenjing; Yao, Bowen; Li, Chun; Shi, Gaoquan

    2014-03-12

    Composites of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and reduced graphene oxide (rGO) have been prepared by solution mixing and applied as electrocatalysts for oxygen reduction reaction (ORR) after treatment with concentrated H2SO4. The blending of rGO induces the conformational change of PEDOT chains from benzoid to quionoid structure and charge transfer from rGO to PEDOT. H2SO4 post-treatment can remove part of insulating PSS from the surface of the PEDOT:PSS/rGO composite film, resulting in a significant conductivity enhancement of the composite. This synergistic effect makes the H2SO4-treated PEDOT:PSS/rGO composite a promising catalyst for ORR. It exhibits enhanced electrocatalytic activity, better tolerance to a methanol crossover effect and CO poisoning, and longer durability than those of the platinum/carbon catalyst. PMID:24456474

  12. Nanostructured Electrocatalysts for PEM Fuel Cells and Redox Flow Batteries: A Selected Review

    SciTech Connect

    Shao, Yuyan; Cheng, Yingwen; Duan, Wentao; Wang, Wei; Lin, Yuehe; Wang, Yong; Liu, Jun

    2015-12-04

    PEM fuel cells and redox flow batteries are two very similar technologies which share common component materials and device design. Electrocatalysts are the key components in these two devices. In this Review, we discuss recent progress of electrocatalytic materials for these two technologies with a focus on our research activities at Pacific Northwest National Laboratory (PNNL) in the past years. This includes (1) nondestructive functionalization of graphitic carbon as Pt support to improve its electrocatalytic performance, (2) triple-junction of metal–carbon–metal oxides to promote Pt performance, (3) nitrogen-doped carbon and metal-doped carbon (i.e., metal oxides) to improve redox reactions in flow batteries. A perspective on future research and the synergy between the two technologies are also discussed.

  13. Platinum monolayer electrocatalyst on gold nanostructures on silicon for photoelectrochemical hydrogen evolution.

    PubMed

    Kye, Joohong; Shin, Muncheol; Lim, Bora; Jang, Jae-Won; Oh, Ilwhan; Hwang, Seongpil

    2013-07-23

    Pt monolayer decorated gold nanostructured film on planar p-type silicon is utilized for photoelectrochemical H2 generation in this work. First, gold nanostructured film on silicon was spontaneously produced by galvanic displacement of the reduction of gold ion and the oxidation of silicon in the presence of fluoride anion. Second, underpotential deposition (UPD) of copper under illumination produced Cu monolayer on gold nanostructured film followed by galvanic exchange of less-noble Cu monolayer with more-noble PtCl6(2-). Pt(shell)/Au(core) on p-type silicon showed the similar activity with platinum nanoparticle on silicon for photoelectrochemical hydrogen evolution reaction in spite of low platinum loading. From Tafel analysis, Pt(shell)/Au(core) electrocatalyst shows the higher area-specific activity than platinum nanoparticle on silicon demonstrating the significant role of underlying gold for charge transfer reaction from silicon to H(+) through platinum catalyst. PMID:23750804

  14. Electrochemical Reconstitution of Biomolecules for Applications as Electrocatalysts for the Bionanofuel Cell

    NASA Technical Reports Server (NTRS)

    Kim, Jae-Woo; Choi, Sang H.; Lillehei, Peter T.; King, Glen C.; Watt, Gerald D.; Chu, Sang-Hyon; Park, Yeonjoon; Thibeault, Sheila

    2004-01-01

    Platinum-cored ferritins were synthesized as electrocatalysts by electrochemical biomineralization of immobilized apoferritin with platinum. The platinum cored ferritin was fabricated by exposing the immobilized apoferritin to platinum ions at a reduction potential. On the platinum-cored ferritin, oxygen is reduced to water with four protons and four electrons generated from the anode. The ferritin acts as a nano-scale template, a biocompatible cage, and a separator between the nanoparticles. This results in a smaller catalyst loading of the electrodes for fuel cells or other electrochemical devices. In addition, the catalytic activity of the ferritin-stabilized platinum nanoparticles is enhanced by the large surface area and particle size phenomena. The work presented herein details the immobilization of ferritin with various surface modifications, the electrochemical biomineralization of ferritin with different inorganic cores, and the fabrication of self-assembled 2-D arrays with thiolated ferritin.

  15. Electrodeposited noble metal particles in polyelectrolyte multilayer matrix as electrocatalyst for oxygen reduction studied using SECM.

    PubMed

    Shen, Yan; Träuble, Markus; Wittstock, Gunther

    2008-07-01

    Taking the advantage of the stability and penetrability of polyelectrolyte films formed by layer-by-layer (LbL) deposition, noble metal particles of Pd and Pt were fabricated in a preformed polyeletrolyte multilayer film by galvanic deposition. The metal deposition occurred as metal particles and they were tested for their properties as electrocatalyst for oxygen reduction. Atomic force microscopy (AFM) was used to characterize the morphology of the particle films. The noble metal particles were investigated by cyclic voltammetry (CV) and scanning electrochemical microscopy (SECM) with respect to oxygen reduction. The results show that the electrocatalytic properties of the Pd particle film can be adjusted by the electrodeposition time. The hydrogen peroxide formed as an intermediate during electroreduction of dioxygen was conveniently measured in the SECM using the substrate-generation/tip-collection mode. The relevance of the main reduction pathways could be extracted from fitting the current transients to an analytical model. PMID:18563224

  16. Structural effects of a carbon matrix in non-precious metal O2-reduction electrocatalysts.

    PubMed

    He, Wenhui; Wang, Ying; Jiang, Chunhuan; Lu, Lehui

    2016-05-01

    Developing non-precious metal electrocatalysts (NPMCs) for the oxygen reduction reaction (ORR) is of paramount importance for commercial implementation of several clean energy techniques (e.g. proton exchange membrane fuel cells). However, limited understanding of the ORR catalytic mechanism of NPMCs greatly hinders the progress in the precise fabrication of NPMCs at the molecular or atomic level. Recently, an increasing number of studies have demonstrated the crucial role of a carbon matrix in exposing, stabilizing, and activating the catalytic sites, thus providing a platform to identify the nature of NPMCs. Herein, the unique structural effects of a carbon matrix in NPMCs are first reviewed to inspire the development of more advanced NPMCs for the ORR. PMID:26955940

  17. Metal molybdate nanorods as non-precious electrocatalysts for the oxygen reduction

    NASA Astrophysics Data System (ADS)

    Wu, Tian; Zhang, Lieyu

    2015-12-01

    Development of non-precious electrocatalysts with applicable electrocatalytic activity towards the oxygen reduction reaction (ORR) is important to fulfill broad-based and large-scale applications of metal/air batteries and fuel cells. Herein, nickel and cobalt molybdates with uniform nanorod morphology are synthesized using a facile one-pot hydrothermal method. The ORR activity of the prepared metal molybdate nanorods in alkaline media are investigated by using cyclic voltammetry (CV), linear sweep voltammetry (LSV) and chronoamperomety in rotating disk electrode (RDE) techniques. The present study suggests that the prepared metal molybdate nanorods exhibit applicable electrocatalytic activities towards the ORR in alkaline media, promising the applications as non-precious cathode in fuel cells and metal-air batteries.

  18. Nitrogen-doped Graphene-Supported Transition-metals Carbide Electrocatalysts for Oxygen Reduction Reaction

    PubMed Central

    Chen, Minghua; Liu, Jilei; Zhou, Weijiang; Lin, Jianyi; Shen, Zexiang

    2015-01-01

    A novel and facile two-step strategy has been designed to prepare high performance bi-transition-metals (Fe- and Mo-) carbide supported on nitrogen-doped graphene (FeMo-NG) as electrocatalysts for oxygen reduction reactions (ORR). The as-synthesized FeMo carbide -NG catalysts exhibit excellent electrocatalytic activities for ORR in alkaline solution, with high onset potential (−0.09 V vs. saturated KCl Ag/AgCl), nearly four electron transfer number (nearly 4) and high kinetic-limiting current density (up to 3.5 mA cm−2 at −0.8 V vs. Ag/AgCl). Furthermore, FeMo carbide -NG composites show good cycle stability and much better toxicity tolerance durability than the commercial Pt/C catalyst, paving their application in high-performance fuel cell and lithium-air batteries. PMID:25997590

  19. Nitrogen-doped Graphene-Supported Transition-metals Carbide Electrocatalysts for Oxygen Reduction Reaction.

    PubMed

    Chen, Minghua; Liu, Jilei; Zhou, Weijiang; Lin, Jianyi; Shen, Zexiang

    2015-01-01

    A novel and facile two-step strategy has been designed to prepare high performance bi-transition-metals (Fe- and Mo-) carbide supported on nitrogen-doped graphene (FeMo-NG) as electrocatalysts for oxygen reduction reactions (ORR). The as-synthesized FeMo carbide -NG catalysts exhibit excellent electrocatalytic activities for ORR in alkaline solution, with high onset potential (-0.09 V vs. saturated KCl Ag/AgCl), nearly four electron transfer number (nearly 4) and high kinetic-limiting current density (up to 3.5 mA cm(-2) at -0.8 V vs. Ag/AgCl). Furthermore, FeMo carbide -NG composites show good cycle stability and much better toxicity tolerance durability than the commercial Pt/C catalyst, paving their application in high-performance fuel cell and lithium-air batteries. PMID:25997590

  20. Nitrogen-doped Graphene-Supported Transition-metals Carbide Electrocatalysts for Oxygen Reduction Reaction

    NASA Astrophysics Data System (ADS)

    Chen, Minghua; Liu, Jilei; Zhou, Weijiang; Lin, Jianyi; Shen, Zexiang

    2015-05-01

    A novel and facile two-step strategy has been designed to prepare high performance bi-transition-metals (Fe- and Mo-) carbide supported on nitrogen-doped graphene (FeMo-NG) as electrocatalysts for oxygen reduction reactions (ORR). The as-synthesized FeMo carbide -NG catalysts exhibit excellent electrocatalytic activities for ORR in alkaline solution, with high onset potential (-0.09 V vs. saturated KCl Ag/AgCl), nearly four electron transfer number (nearly 4) and high kinetic-limiting current density (up to 3.5 mA cm-2 at -0.8 V vs. Ag/AgCl). Furthermore, FeMo carbide -NG composites show good cycle stability and much better toxicity tolerance durability than the commercial Pt/C catalyst, paving their application in high-performance fuel cell and lithium-air batteries.

  1. Active and stable carbon nanotube/nanoparticle composite electrocatalyst for oxygen reduction

    PubMed Central

    Chung, Hoon T.; Won, Jong H.; Zelenay, Piotr

    2013-01-01

    Nanostructured carbon-based materials, such as nitrogen-doped carbon nanotube arrays, Co3O4/nitrogen-doped graphene hybrids and carbon nanotube–graphene complexes have shown respectable oxygen reduction reaction activity in alkaline media. Although certainly promising, the performance of these materials does not yet warrant implementation in the energy conversion/storage devices utilizing basic electrolytes, for example, alkaline fuel cells, metal-air batteries and certain electrolysers. Here we demonstrate a new type of nitrogen-doped carbon nanotube/nanoparticle composite oxygen reduction reaction electrocatalyst obtained from iron acetate as an iron precursor and from cyanamide as a nitrogen and carbon nanotube precursor in a simple, scalable and single-step method. The composite has the highest oxygen reduction reaction activity in alkaline media of any non-precious metal catalysts. When used at a sufficiently high loading, this catalyst also outperforms the most active platinum-based catalysts. PMID:23715281

  2. Cobalt-Boride: An efficient and robust electrocatalyst for Hydrogen Evolution Reaction

    NASA Astrophysics Data System (ADS)

    Gupta, Suraj; Patel, Nainesh; Miotello, Antonio; Kothari, D. C.

    2015-04-01

    This work presents Cobalt-Boride (Co-B) as a non-noble, efficient and robust electrocatalyst for Hydrogen Evolution Reaction (HER) active in aqueous solution of wide pH values. In neutral solution, amorphous Co-B nanoparticles (30-50 nm size) generate high current density (10 mA/cm2) at low overpotential (250 mV) with Tafel slope of 75 mV/dec following Volmer-Heyrovsky reaction mechanism. Highly active Co surface sites created by electronic transfer from B to Co (as inferred from XPS analysis and supported by theoretical calculations) are responsible for this significant HER activity in wide range of pH (4-9) values. Stability and reusability tests also demonstrate the robust nature of the catalyst.

  3. Enhanced methanol electro-oxidation reaction on Pt-CoOx/MWCNTs hybrid electro-catalyst

    NASA Astrophysics Data System (ADS)

    Nouralishahi, Amideddin; Rashidi, Ali Morad; Mortazavi, Yadollah; Khodadadi, Abbas Ali; Choolaei, Mohammadmehdi

    2015-04-01

    The electro-catalytic behavior of Pt-CoOx/MWCNTs in methanol electro-oxidation reaction (MOR) is investigated and compared to that of Pt/MWCNTs. The electro-catalysts were synthesized by an impregnation method using NaBH4 as the reducing agent. The morphological and physical characteristics of samples are examined by XRD, TEM, ICP and EDS techniques. In the presence of CoOx, Pt nanoparticles were highly distributed on the support with an average particle size of 2 nm, an obvious decrease from 5.1 nm for Pt/MWCNTs. Cyclic voltammetry, CO-stripping, Chronoamperometry, and electrochemical impedance spectroscopy (EIS) measurements are used to study the electrochemical behavior of the electro-catalysts. The results revealed a considerable enhancement in the oxidation kinetics of COads on Pt active sites by the participation of CoOx. Compared to Pt/MWCNTs, Pt-CoOx/MWCNTs sample has a larger electrochemical active surface area (ECSA) and higher electro-catalytic activity and stability toward methanol electro-oxidation. According to the results of cyclic voltammetry, the forward anodic peak current density enhances more than 89% at the optimum atomic ratio of Pt:Co = 2:1. Furthermore, inclusion of cobalt oxide species causes the onset potential of methanol electro-oxidation reaction to shift 84 mV to negative values compared to that on Pt/MWCNTs. Based on EIS data, dehydrogenation of methanol is the rate-determining step of MOR on both Pt/MWCNTs and Pt-CoOx/MWCNTs, at small overpotentials. However, at higher overpotentials, the oxidation of adsorbed oxygen-containing groups controls the total rate of MOR process.

  4. Hydrogen Production Using Nickel Electrocatalysts with Pendant Amines: Ligand Effects on Rates and Overpotentials

    SciTech Connect

    Wiese, Stefan; Kilgore, Uriah J.; Ho, Ming-Hsun; Raugei, Simone; DuBois, Daniel L.; Bullock, R. Morris; Helm, Monte L.

    2013-11-01

    A Ni-based electrocatalyst for H2 production, [Ni(8PPh2NC6H4Br)2](BF4)2, featuring eight-membered cyclic diphosphine ligands incorporating a single amine base, 1-para-bromo-phenyl-3,7-triphenyl-1-aza-3,7-diphosphacycloheptane (8PPh2NC6H4Br) has been synthesized and characterized. X-ray diffraction studies reveal that the cation of [Ni(8PPh2NC6H4Br)2(CH3CN)](BF4)2 has a distorted trigonal bipyramidal geometry. In CH3CN [Ni(8PPh2NC6H4Br)2]2+ is an electrocatalyst for reduction of protons, and it has a maximum turnover frequency for H2 production of 800 s-1 with a 700 mV overpotential (at Ecat/2) when using [(DMF)H]OTf as the acid. Addition of H2O to acidic CH3CN solutions of [Ni(8PPh2NC6H4Br)2]2+ results in an increase of the turnover frequency for H2 production to a maximum of 3,300 s-1 with an overpotential of 760 mV at Ecat/2. Computational studies carried out on [Ni(8PPh2NC6H4Br)2]2+ indicate the observed catalytic rate is limited by formation of non-productive protonated isomers, diverting active catalyst from the catalytic cycle. The results of this research show that proton delivery from the exogenous acid to the correct position on the proton relay of the metal complex is essential for fast H2 production. This research was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences. Pacific Northwest National Laboratory is operated by Battelle for the U.S. Department of Energy.

  5. A cobalt-nitrogen complex on N-doped three-dimensional graphene framework as a highly efficient electrocatalyst for oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Jiang, Yuanyuan; Lu, Yizhong; Wang, Xiaodan; Bao, Yu; Chen, Wei; Niu, Li

    2014-11-01

    The high cost and limited natural abundance of platinum hinder its widespread applications as the oxygen reduction reaction (ORR) electrocatalyst for fuel cells. Carbon-supported materials containing metals such as Fe or Co as well as nitrogen have been proposed to reduce the cost without obvious lowering the performance compared to Pt-based electrocatalysts. In this work, based on the pyrolyzed corrin structure of vitamin B12 on the simultaneously reduced graphene support (g-VB12), we construct an efficient oxygen reduction electrocatalyst with very positive half-wave potential (only ~30 mV deviation from Pt/C), high selectivity (electron transfer number close to 4) and excellent durability (only 11 mV shift of the half-wave potential after 10 000 potential cycles). The admirable performance of this electrocatalyst can be attributed to the homogeneous distribution of abundant Co-Nx active sites, and a well-defined three-dimensional mesoporous structure of the N-doped graphene support. The high activity and long-term stability of the low cost g-VB12 make it a promising ORR electrocatalyst in alkaline fuel cells.The high cost and limited natural abundance of platinum hinder its widespread applications as the oxygen reduction reaction (ORR) electrocatalyst for fuel cells. Carbon-supported materials containing metals such as Fe or Co as well as nitrogen have been proposed to reduce the cost without obvious lowering the performance compared to Pt-based electrocatalysts. In this work, based on the pyrolyzed corrin structure of vitamin B12 on the simultaneously reduced graphene support (g-VB12), we construct an efficient oxygen reduction electrocatalyst with very positive half-wave potential (only ~30 mV deviation from Pt/C), high selectivity (electron transfer number close to 4) and excellent durability (only 11 mV shift of the half-wave potential after 10 000 potential cycles). The admirable performance of this electrocatalyst can be attributed to the homogeneous

  6. A rhodium/silicon co-electrocatalyst design concept to surpass platinum hydrogen evolution activity at high overpotentials.

    PubMed

    Zhu, Lili; Lin, Haiping; Li, Youyong; Liao, Fan; Lifshitz, Yeshayahu; Sheng, Minqi; Lee, Shuit-Tong; Shao, Mingwang

    2016-01-01

    Currently, platinum-based electrocatalysts show the best performance for hydrogen evolution. All hydrogen evolution reaction catalysts should however obey Sabatier's principle, that is, the adsorption energy of hydrogen to the catalyst surface should be neither too high nor too low to balance between hydrogen adsorption and desorption. To overcome the limitation of this principle, here we choose a composite (rhodium/silicon nanowire) catalyst, in which hydrogen adsorption occurs on rhodium with a large adsorption energy while hydrogen evolution occurs on silicon with a small adsorption energy. We show that the composite is stable with better hydrogen evolution activity than rhodium nanoparticles and even exceeding those of commercial platinum/carbon at high overpotentials. The results reveal that silicon plays a key role in the electrocatalysis. This work may thus open the door for the design and fabrication of electrocatalysts for high-efficiency electric energy to hydrogen energy conversion. PMID:27447292

  7. Two dimensional MoS2/graphene composites as promising supports for Pt electrocatalysts towards methanol oxidation

    NASA Astrophysics Data System (ADS)

    Zhai, Chunyang; Zhu, Mingshan; Bin, Duan; Ren, Fangfang; Wang, Caiqin; Yang, Ping; Du, Yukou

    2015-02-01

    Two dimensional (2D) molybdenum disulfide (MoS2)/reduced graphene oxide (RGO) nanocomposites are synthesized by a hydrothermal method and served as supports for Pt electrocatalysts towards electrocatalytic methanol oxidation. The Pt nanoclusters with uniform size of 3.41 nm are well-dispersed on the surface of MoS2/RGO sheets. Compare to commercial Pt/C and Pt-MoS2 electrodes, the as-prepared Pt-MoS2/RGO composites display 5.65 and 1.73 times higher electrocatalytic activity of methanol oxidation, respectively. This outstanding electrocatalytic performance evidences 2D MoS2/graphene nanocomposites as promising electrocatalyst supports for the commercialization of fuel cells.

  8. Evaluation of the performance degradation at PAFC investigation of dealloying process of electrocatalysts with in-situ XRD

    SciTech Connect

    Nakajima, Noriyuki; Uchida, Hiroyuki; Watanabe, Masahiro

    1996-12-31

    As a complementary research project to the demonstration project of 5MW and 1 MW PAFC plants, the mechanism and rate of deterioration of the cells and stacks have been studied from 1995 FY, with the objective of establishing an estimation method for the service life-time of the cell stacks. This work has been performed in the Basic Research Project, as part of that project on PAFC`s, selecting four subjects (Electrocatalysts degradation, Electrolyte fill-level, Cell material corrosion, Electrolyte loss) as the essential factors relating to the life-time. In this study, the effect of temperature and potential on the dealloying process of electrocatalysts was examined in H{sub 3}PO{sub 4} electrolyte with X-ray diffraction measurement.

  9. A facile approach to synthesize stable CNTs@MnO electrocatalyst for high energy lithium oxygen batteries

    PubMed Central

    Luo, Wen-Bin; Chou, Shu-Lei; Jia-Zhao Wang; Zhai, Yu-Chun; Liu, Hua-Kun

    2015-01-01

    A composite of manganese monoxide loaded onto carbon nanotubes (CNTs@MnO) has been synthesized by a facile approach, in which the CNTs form a continuous conductive network connecting the electrocatalyst MnO nanoparticles together to facilitate good electrochemical performance. The electrocatalyst MnO shows favourable rechargeability, and good phase and morphology stability in lithium oxygen batteries. Excellent cycling performance is also demonstrated, in which the terminal voltage is higher than 2.4 V after 100 cycles at 0.4 mA cm−2, with 1000 mAh g−1(composite) capacity. Therefore, this hybrid material is promising for use as a cathode material for lithium oxygen batteries. PMID:25634100

  10. A facile approach to synthesize stable CNTs@MnO electrocatalyst for high energy lithium oxygen batteries.

    PubMed

    Luo, Wen-Bin; Chou, Shu-Lei; Jia-Zhao Wang; Zhai, Yu-Chun; Liu, Hua-Kun

    2015-01-01

    A composite of manganese monoxide loaded onto carbon nanotubes (CNTs@MnO) has been synthesized by a facile approach, in which the CNTs form a continuous conductive network connecting the electrocatalyst MnO nanoparticles together to facilitate good electrochemical performance. The electrocatalyst MnO shows favourable rechargeability, and good phase and morphology stability in lithium oxygen batteries. Excellent cycling performance is also demonstrated, in which the terminal voltage is higher than 2.4 V after 100 cycles at 0.4 mA cm(-2), with 1000 mAh g(-1)(composite) capacity. Therefore, this hybrid material is promising for use as a cathode material for lithium oxygen batteries. PMID:25634100

  11. A rhodium/silicon co-electrocatalyst design concept to surpass platinum hydrogen evolution activity at high overpotentials

    PubMed Central

    Zhu, Lili; Lin, Haiping; Li, Youyong; Liao, Fan; Lifshitz, Yeshayahu; Sheng, Minqi; Lee, Shuit-Tong; Shao, Mingwang

    2016-01-01

    Currently, platinum-based electrocatalysts show the best performance for hydrogen evolution. All hydrogen evolution reaction catalysts should however obey Sabatier's principle, that is, the adsorption energy of hydrogen to the catalyst surface should be neither too high nor too low to balance between hydrogen adsorption and desorption. To overcome the limitation of this principle, here we choose a composite (rhodium/silicon nanowire) catalyst, in which hydrogen adsorption occurs on rhodium with a large adsorption energy while hydrogen evolution occurs on silicon with a small adsorption energy. We show that the composite is stable with better hydrogen evolution activity than rhodium nanoparticles and even exceeding those of commercial platinum/carbon at high overpotentials. The results reveal that silicon plays a key role in the electrocatalysis. This work may thus open the door for the design and fabrication of electrocatalysts for high-efficiency electric energy to hydrogen energy conversion. PMID:27447292

  12. Carbon-coated MoS2 nanosheets as highly efficient electrocatalysts for the hydrogen evolution reaction.

    PubMed

    Dou, Shuo; Wu, Jianghong; Tao, Li; Shen, Anli; Huo, Jia; Wang, Shuangyin

    2016-01-29

    As a green and highly efficient energy resource, hydrogen (H2) has attracted much attention in recent years. Electrochemical water splitting is an economic process to generate H2. MoS2 is a promising candidate to replace traditional Pt-based electrocatalysts for the hydrogen evolution reaction (HER) under acidic conditions. But low electrical conductivity is one of bottlenecks for the large-scale application of MoS2. In this work, a carbon-coated MoS2 hybrid electrocatalyst was prepared with a chemical vapour deposition (CVD) approach to improve the electrical conductivity of MoS2. In addition to the surface-coating carbon, a small graphene-like layer could also be inserted into the interlayers of MoS2 during the CVD process which resulted in more active sites being exposed in MoS2. Enhanced electrical conductivity and more exposed active sites lead to excellent HER activity. PMID:26657536

  13. Carbon-coated MoS2 nanosheets as highly efficient electrocatalysts for the hydrogen evolution reaction

    NASA Astrophysics Data System (ADS)

    Dou, Shuo; Wu, Jianghong; Tao, Li; Shen, Anli; Huo, Jia; Wang, Shuangyin

    2016-01-01

    As a green and highly efficient energy resource, hydrogen (H2) has attracted much attention in recent years. Electrochemical water splitting is an economic process to generate H2. MoS2 is a promising candidate to replace traditional Pt-based electrocatalysts for the hydrogen evolution reaction (HER) under acidic conditions. But low electrical conductivity is one of bottlenecks for the large-scale application of MoS2. In this work, a carbon-coated MoS2 hybrid electrocatalyst was prepared with a chemical vapour deposition (CVD) approach to improve the electrical conductivity of MoS2. In addition to the surface-coating carbon, a small graphene-like layer could also be inserted into the interlayers of MoS2 during the CVD process which resulted in more active sites being exposed in MoS2. Enhanced electrical conductivity and more exposed active sites lead to excellent HER activity.

  14. Synthesis and Characterization of CO-and H2S-Tolerant Electrocatalysts for PEM Fuel Cell

    SciTech Connect

    Shamsuddin Ilias

    2005-12-22

    The present state-of-art Proton Exchange Membrane Fuel Cell (PEMFC) technology is based on platinum (Pt) as a catalyst for both the fuel (anode) and air (cathode) electrodes. This catalyst is highly active but susceptible to poisoning by CO, which may be present in the H{sub 2}-fuel used or may be introduced during the fuel processing. Presence of trace amount of CO and H{sub 2}S in the H{sub 2}-fuel poisons the anode irreversibly and decreases the performance of the PEMFCs. In an effort to reduce the Pt-loading and improve the PEMFC performance, we propose to synthesize a number of Pt-based binary, ternary, and quaternary electrocatalysts using Ru, Mo, Ir, Ni, and Co as a substitute for Pt. By fine-tuning the metal loadings and compositions of candidate electrocatalysts, we plan to minimize the cost and optimize the catalyst activity and performance in PEMFC. The feasibility of the novel electrocatalysts will be demonstrated in the proposed effort with gas phase CO and H{sub 2}S concentrations typical of those found in reformed fuel gas with coal/natural gas/methanol feedstocks. During this reporting period we synthesized four Pt-based electrocatalysts catalysts (Pt/Ru/Mo/Se, Pt/Ru/Mo/Ir, Pt/Ru/Mo/W, Ptr/Ru/Mo/Co) on Vulcan XG72 Carbon support by both conventional and ultra-sonication method. From current-voltage performance study, the catalytic activity was found in the increasing order of Pt/Ru/Mo/Ir > Pt/Ru/Mo/W > Pt/Ru/Mo/Co > Pt/Ru/MO/Se. Sonication method appears to provide better dispersion of catalysts on carbon support.

  15. A high efficiency CoCr₂O₄/carbon nanotubes nanocomposite electrocatalyst for dye-sensitised solar cells.

    PubMed

    Guo, Mingxing; Tang, Beibei; Zhang, Haimin; Yin, Shuhui; Jiang, Wei; Zhang, Yiming; Li, Mengying; Wang, Hui; Jiao, Liqi

    2014-07-14

    A CoCr2O4/carbon nanotubes (CoCr2O4/CNTs) nanocomposite was successfully synthesised by a facile solution route, and used as an electrocatalyst for dye-sensitised solar cells (DSSCs) for the first time, exhibiting a comparable power conversion efficiency of 8.40% to Pt-based DSSCs (η = 8.68%) owing to the superior electrocatalytic activity of the nanocomposite. PMID:24869626

  16. Fluorine-Doped and Partially Oxidized Tantalum Carbides as Nonprecious Metal Electrocatalysts for Methanol Oxidation Reaction in Acidic Media.

    PubMed

    Yue, Xin; He, Chunyong; Zhong, Chengyong; Chen, Yuanping; Jiang, San Ping; Shen, Pei Kang

    2016-03-16

    A nonprecious metal electrocatalyst based on fluorine-doped tantalum carbide with an oxidative surface on graphitized carbon (TaCx FyOz/(g)C) is developed by using a simple one-pot in situ ion exchange and adsorption method, and the TaCxFyOz/(g)C shows superior performance and durability for methanol oxidation reaction and extreme tolerance to CO poisoning in acidic media. PMID:26779940

  17. Synthesis and Characterization of Bimetallic Core-Shell-Supported Platinum Monolayer Electrocatalysts for the Oxygen Reduction Reaction

    NASA Astrophysics Data System (ADS)

    Kuttiyiel, Kurian Abraham

    Fuel cells are expected to be one of the major clean energy sources in the near future. However, the slow kinetics of electrocatalytic oxygen reduction reaction (ORR) and the high loading of Platinum (Pt) for the cathode material are the urgent issues to be addressed since they determine the efficiency and the cost of this energy source. In this study, a new approach was developed for designing electrocatalysts for the ORR in fuel cells. These electrocatalysts consist of only one Pt monolayer on suitable carbon-supported Iridium-Nickel (IrNi) core-shell nanoparticles. The synthesis involved depositing a monolayer of Copper (Cu) on IrNi metal alloy surface at under-potentials, followed by galvanic displacement of the Cu monolayer with Pt. It was found that the electronic properties of Pt monolayer could be fine-tuned by the electronic and geometric effects introduced by the substrate metal. The Pt mass activity of the new Pt monolayer IrNi electrocatalysts was up to six times higher than the state-of-the-art commercial Pt/C catalysts. The structure and composition of the core-shell nanoparticles were verified using transmission electron microscopy and in situ X-ray absorption spectroscopy, while potential cycling test was employed to confirm the stability of the electrocatalyst. The formation of Ir shell on IrNi alloy during annealing due to thermal segregation was monitored by time-resolved synchrotron XRD measurements. Our experimental results, supported by computations, demonstrated an effective way of using Pt that can resolve key ORR problems which include inadequate activity and durability while minimizing the Pt loading.

  18. In situ anomalous small-angle X-ray scattering studies of platinum nanoparticle fuel cell electrocatalyst degradation.

    PubMed

    Gilbert, James A; Kariuki, Nancy N; Subbaraman, Ram; Kropf, A Jeremy; Smith, Matt C; Holby, Edward F; Morgan, Dane; Myers, Deborah J

    2012-09-12

    Polymer electrolyte fuel cells (PEFCs) are a promising high-efficiency energy conversion technology, but their cost-effective implementation, especially for automotive power, has been hindered by degradation of the electrochemically active surface area (ECA) of the Pt nanoparticle electrocatalysts. While numerous studies using ex situ post-mortem techniques have provided insight into the effect of operating conditions on ECA loss, the governing mechanisms and underlying processes are not fully understood. Toward the goal of elucidating the electrocatalyst degradation mechanisms, we have followed Pt nanoparticle growth during potential cycling of the electrocatalyst in an aqueous acidic environment using in situ anomalous small-angle X-ray scattering (ASAXS). ASAXS patterns were analyzed to obtain particle size distributions (PSDs) of the Pt nanoparticle electrocatalysts at periodic intervals during the potential cycling. Oxide coverages reached under the applied potential cycling protocols were both calculated and determined experimentally. Changes in the PSD, mean diameter, and geometric surface area identify the mechanism behind Pt nanoparticle coarsening in an aqueous environment. Over the first 80 potential cycles, the dominant Pt surface area loss mechanism when cycling to 1.0-1.1 V was found to be preferential dissolution or loss of the smallest particles with varying extents of reprecipitation of the dissolved species onto existing particles, resulting in particle growth, depending on potential profile. Correlation of ASAXS-determined particle growth with both calculated and voltammetrically determined oxide coverages demonstrates that the oxide coverage is playing a key role in the dissolution process and in the corresponding growth of the mean Pt nanoparticle size and loss of ECA. This understanding potentially reduces the complex changes in PSD and ECA resulting from various voltage profiles to a response dependent on oxide coverage. PMID:22857132

  19. Ternary Electrocatalysts for Oxidizing Ethanol to Carbon Dioxide: Making Ir Capable of Splitting C-C bond

    SciTech Connect

    Li, Meng; Cullen, David A; Sasaki, Kotaro; Marinkovic, N.; More, Karren Leslie; Adzic, Radoslav R.

    2013-01-01

    Splitting the C-C bond is the main obstacle to electroxidation of ethanol (EOR) to CO2. We recently demonstrated that the ternary PtRhSnO2 electrocatalyst can accomplish that reaction at room temperature with Rh having a unique capability to split the C-C bond. In this article we report the finding that Ir can be induced to split the C-C bond as a component of the ternary catalyst. We synthesized, characterized and compared the properties of several ternary electrocatalysts. Carbon-supported nanoparticle (NP) electrocatalysts comprising a SnO2 NP core decorated with multi-metallic nanoislands (MM = PtIr, PtRh, IrRh, PtIrRh) were prepared using a seeded growth approach. An array of characterization techniques were employed to establish the composition and architecture of the synthesized MM /SnO2 NPs, while electrochemical and in situ infrared reflection absorption spectroscopy studies elucidated trends in activity and the nature of the reaction intermediates and products. Both EOR reactivity and selectivity towards CO2 formation of several of these MM /SnO2/C electrocatalysts are significantly higher compared to conventional Pt/C and Pt/SnO2/C catalysts. We demonstrate that the PtIr/SnO2/C catalyst with high Ir content shows outstanding catalytic property with the most negative EOR onset potential and reasonably good selectivity towards ethanol complete oxidation to CO2. PtRh/SnO2/C catalysts with a moderate Rh content exhibit the highest EOR selectivity, as deduced from infrared studies.

  20. Strongly Coupled CoCr2 O4 /Carbon Nanosheets as High Performance Electrocatalysts for Oxygen Evolution Reaction.

    PubMed

    Al-Mamun, Mohammad; Su, Xintai; Zhang, Haimin; Yin, Huajie; Liu, Porun; Yang, Huagui; Wang, Dan; Tang, Zhiyong; Wang, Yun; Zhao, Huijun

    2016-06-01

    A strongly coupled CoCr2 O4 /carbon nanosheet composite is concurrently grown via a facile one-step molten-salt calcination approach. The strong coupling between carbon and CoCr2 O4 has improved the electrical conductivity and preserved the active sites in catalysts. These results may pave the way to improve the performance of spinel oxides as electrocatalysts for oxygen evolution reactions. PMID:27087475

  1. Nitrogen and carbon doped titanium oxide as an alternative and durable electrocatalyst support in polymer electrolyte fuel cells

    NASA Astrophysics Data System (ADS)

    Dhanasekaran, P.; Vinod Selvaganesh, S.; Bhat, Santoshkumar D.

    2016-02-01

    Nitrogen and carbon doped titanium oxide as an alternative and ultra-stable support to platinum catalysts is prepared and its efficiency is determined by polymer electrolyte fuel cell. Nitrogen and carbon doped titanium oxide is prepared by varying the melamine ratio followed by calcination at 900 °C. Platinum nanoparticles are deposited onto doped and undoped titanium oxide by colloidal method. The doping effect, surface morphology, chemical oxidation state and metal/metal oxide interfacial contact are studied by X-ray diffraction, Raman spectroscopy, high resolution transmission electron microscopy and X-ray photo electron spectroscopy. The nitrogen and carbon doping changes both electronic and structural properties of titanium oxide resulting in enhanced oxygen reduction reaction activity. The platinum deposited on optimum level of nitrogen and carbon doped titanium oxide exhibits improved cell performance in relation to platinum on titanium oxide electrocatalysts. The effect of metal loading on cathode electrocatalyst is investigated by steady-state cell polarization. Accelerated durability test over 50,000 cycles for these electrocatalysts suggested the improved interaction between platinum and nitrogen and carbon doped titanium oxide, retaining the electrochemical surface area and oxygen reduction performance as comparable to platinum on carbon support.

  2. Preparation and characterization of carbon-supported PtOs electrocatalysts via polyol reduction method for methanol oxidation reaction

    NASA Astrophysics Data System (ADS)

    Li, Zuopeng; Li, Muwu; Han, Mingjia; Zeng, Jianhuang; Li, Yuexia; Guo, Yanqin; Liao, Shijun

    2014-12-01

    A polyol reduction approach was employed to prepare carbon-supported PtOs/C electrocatalysts (PtOs-1/C was obtained via the co-reduction of H2PtCl6 and K2OsCl6 precursors and PtOs-2/C was obtained via a sequential deposition method in which Pt was deposited on the preformed Os nanoparticles). The home-made electrocatalysts were extensively characterized via transmission electron microscopy, thermogravimetric analysis, X-ray diffraction, and X-ray photoelectron spectroscopy. The evaluation results of the catalytic activities obtained via cyclic voltammetry, CO stripping voltammetry, and chronoamperometry showed that the successively reduced PtOs-2/C out-performed PtOs-1/C in terms of specific/mass activity (528 mA mg-1PtOs and 0.98 mA cm-2) and CO tolerance in room temperature methanol electrooxidation reaction. The physical characteristics of the electrocatalysts correlated well with their electrochemical performances. The higher activity of PtOs-2/C was attributed to a combination of factors, such as a mix of nanoparticles (isolated Os, PtOs alloys or bimetallic nanoparticles), higher metallic Os content, and smaller particle sizes.

  3. Spinel-type lithium cobalt oxide as a bifunctional electrocatalyst for the oxygen evolution and oxygen reduction reactions.

    PubMed

    Maiyalagan, Thandavarayan; Jarvis, Karalee A; Therese, Soosairaj; Ferreira, Paulo J; Manthiram, Arumugam

    2014-01-01

    Development of efficient, affordable electrocatalysts for the oxygen evolution reaction and the oxygen reduction reaction is critical for rechargeable metal-air batteries. Here we present lithium cobalt oxide, synthesized at 400 °C (designated as LT-LiCoO2) that adopts a lithiated spinel structure, as an inexpensive, efficient electrocatalyst for the oxygen evolution reaction. The catalytic activity of LT-LiCoO2 is higher than that of both spinel cobalt oxide and layered lithium cobalt oxide synthesized at 800 °C (designated as HT-LiCoO2) for the oxygen evolution reaction. Although LT-LiCoO2 exhibits poor activity for the oxygen reduction reaction, the chemically delithiated LT-Li1-xCoO2 samples exhibit a combination of high oxygen reduction reaction and oxygen evolution reaction activities, making the spinel-type LT-Li0,5CoO2 a potential bifunctional electrocatalyst for rechargeable metal-air batteries. The high activities of these delithiated compositions are attributed to the Co4O4 cubane subunits and a pinning of the Co(3+/4+):3d energy with the top of the O(2-):2p band. PMID:24862287

  4. Spinel-type lithium cobalt oxide as a bifunctional electrocatalyst for the oxygen evolution and oxygen reduction reactions

    NASA Astrophysics Data System (ADS)

    Maiyalagan, Thandavarayan; Jarvis, Karalee A.; Therese, Soosairaj; Ferreira, Paulo J.; Manthiram, Arumugam

    2014-05-01

    Development of efficient, affordable electrocatalysts for the oxygen evolution reaction and the oxygen reduction reaction is critical for rechargeable metal-air batteries. Here we present lithium cobalt oxide, synthesized at 400 °C (designated as LT-LiCoO2) that adopts a lithiated spinel structure, as an inexpensive, efficient electrocatalyst for the oxygen evolution reaction. The catalytic activity of LT-LiCoO2 is higher than that of both spinel cobalt oxide and layered lithium cobalt oxide synthesized at 800 °C (designated as HT-LiCoO2) for the oxygen evolution reaction. Although LT-LiCoO2 exhibits poor activity for the oxygen reduction reaction, the chemically delithiated LT-Li1-xCoO2 samples exhibit a combination of high oxygen reduction reaction and oxygen evolution reaction activities, making the spinel-type LT-Li0,5CoO2 a potential bifunctional electrocatalyst for rechargeable metal-air batteries. The high activities of these delithiated compositions are attributed to the Co4O4 cubane subunits and a pinning of the Co3+/4+:3d energy with the top of the O2-:2p band.

  5. Investigation of nano Pt and Pt-based alloys electrocatalysts for direct methanol fuel cells and their properties

    NASA Astrophysics Data System (ADS)

    Suo, Chunguang; Zhang, Wenbin; Shi, Xinghua; Ma, Chuxia

    2014-03-01

    The electrocatalysts used in micro direct methanol fuel cell (μDMFC), such as Pt/C and Pt alloy/C, prepared by liquid-phase NaBH4 reduction method have been investigated. XC-72 (Cobalt corp. Company, U.S.A) is chosen as the activated carrier for the electrocatalysts to keep the catalysts powder in the range of several nanometers. The XRD, SEM, EDX analyses indicated that the catalysts had small particle size in several nanometers, in excellent dispersed phase and the molar ratio of the precious metals was found to be optimal. The performances of the DMFCs using cathodic catalyst with Pt percentage of 30wt% and different anodic catalysts (Pt-Ru, Pt-Ru-Mo) were tested. The polarization curves and power density curves of the cells were measured to determine the optimal alloy composition and condition for the electrocatalysts. The results showed that the micro direct methanol fuel cell with 30wt% Pt/C as the cathodic catalyst and n(Pt):n(Ru):n(Mo) = 3:2:2 PtRuMo/C as the anodic catalyst at room temperature using 2.0mol/L methanol solution has the best performances.

  6. High performance robust F-doped tin oxide based oxygen evolution electro-catalysts for PEM based water electrolysis

    SciTech Connect

    Datta, Moni Kanchan; Kadakia, Karan; Velikokhatnyi, Oleg I; Jampani, Prashanth H; Chung, Sung Jae; Poston, James A; Manivannan, Ayyakkannu; Kumta, Prashant N

    2013-01-01

    Identification and development of non-noble metal based electro-catalysts or electro-catalysts comprising compositions with significantly reduced amounts of expensive noble metal contents (e.g. IrO{sub 2}, Pt) with comparable electrochemical performance to the standard noble metal/metal oxide for proton exchange membrane (PEM) based water electrolysis would signify a major breakthrough in hydrogen generation via water electrolysis. Development of such systems would lead to two primary outcomes: first, a reduction in the overall capital costs of PEM based water electrolyzers, and second, attainment of the targeted hydrogen production costs (<$3.00/gge delivered by 2015) comparable to conventional liquid fuels. In line with these goals, by exploiting a two-pronged theoretical first principles and experimental approach herein, we demonstrate for the very first time a solid solution of SnO{sub 2}:10 wt% F containing only 20 at.% IrO{sub 2} [e.g. (Sn{sub 0.80}Ir{sub 0.20})O{sub 2}:10F] displaying remarkably similar electrochemical activity and comparable or even much improved electrochemical durability compared to pure IrO{sub 2}, the accepted gold standard in oxygen evolution electro-catalysts for PEM based water electrolysis. We present the results of these studies.

  7. Bioreduction of Precious Metals by Microorganism: Efficient Gold@N-Doped Carbon Electrocatalysts for the Hydrogen Evolution Reaction.

    PubMed

    Zhou, Weijia; Xiong, Tanli; Shi, Chaohong; Zhou, Jian; Zhou, Kai; Zhu, Nengwu; Li, Ligui; Tang, Zhenghua; Chen, Shaowei

    2016-07-11

    The uptake of precious metals from electronic waste is of environmental significance and potential commercial value. A facile bioreductive synthesis is described for Au nanoparticles (ca. 20 nm) supported on N-doped carbon (Au@NC), which was derived from Au/Pycnoporus sanguineus cells. The interface and charge transport between Au and N-doped carbon were confirmed by HRTEM and XPS. Au@NC was employed as an electrocatalyst for the hydrogen evolution reaction (HER), exhibiting a small onset potential of -54.1 mV (vs. RHE), a Tafel slope of 76.8 mV dec(-1) , as well as robust stability in acidic medium. Au@NC is a multifunctional electrocatalyst, which demonstrates high catalytic activity in the oxygen reduction reaction (ORR), as evidenced by an onset potential of +0.97 V, excellent tolerance toward methanol, and long-term stability. This work exemplifies dual recovery of precious Au and fabrication of multifunctional electrocatalysts in an environmentally benign and application-oriented manner. PMID:27218302

  8. Boron/nitrogen co-doped helically unzipped multiwalled carbon nanotubes as efficient electrocatalyst for oxygen reduction.

    PubMed

    Zehtab Yazdi, Alireza; Fei, Huilong; Ye, Ruquan; Wang, Gunuk; Tour, James; Sundararaj, Uttandaraman

    2015-04-15

    Bamboo structured nitrogen doped multiwalled carbon nanotubes have been helically unzipped, and nitrogen doped graphene oxide nanoribbons (CNx-GONRs) with a multifaceted microstructure have been obtained. CNx-GONRs have then been codoped with nitrogen and boron by simultaneous thermal annealing in ammonia and boron oxide atmospheres, respectively. The effects of the codoping time and temperature on the concentration of the dopants and their functional groups have been extensively investigated. X-ray photoelectron spectroscopy results indicate that pyridinic and BC3 are the main nitrogen and boron functional groups, respectively, in the codoped samples. The oxygen reduction reaction (ORR) properties of the samples have been measured in an alkaline electrolyte and compared with the state-of-the-art Pt/C (20%) electrocatalyst. The results show that the nitrogen/boron codoped graphene nanoribbons with helically unzipped structures (CNx/CBx-GNRs) can compete with the Pt/C (20%) electrocatalyst in all of the key ORR properties: onset potential, exchange current density, four electron pathway selectivity, kinetic current density, and stability. The development of such graphene nanoribbon-based electrocatalyst could be a harbinger of precious metal-free carbon-based nanomaterials for ORR applications. PMID:25793636

  9. Strong-Coupled Cobalt Borate Nanosheets/Graphene Hybrid as Electrocatalyst for Water Oxidation Under Both Alkaline and Neutral Conditions.

    PubMed

    Chen, Pengzuo; Xu, Kun; Zhou, Tianpei; Tong, Yun; Wu, Junchi; Cheng, Han; Lu, Xiuli; Ding, Hui; Wu, Changzheng; Xie, Yi

    2016-02-12

    Developing highly active catalysts for the oxygen evolution reaction (OER) is of paramount importance for designing various renewable energy storage and conversion devices. Herein, we report the synthesis of a category of Co-Pi analogue, namely cobalt-based borate (Co-Bi ) ultrathin nanosheets/graphene hybrid by a room-temperature synthesis approach. Benefiting from the high surface active sites exposure yield, enhanced electron transfer capacity, and strong synergetic coupled effect, this Co-Bi NS/G hybrid shows high catalytic activity with current density of 10 mA cm(-2) at overpotential of 290 mV and Tafel slope of 53 mV dec(-1) in alkaline medium. Moreover, Co-Bi NS/G electrocatalysts also exhibit promising performance under neutral conditions, with a low onset potential of 235 mV and high current density of 14.4 mA cm(-2) at 1.8 V, which is the best OER performance among well-developed Co-based OER electrocatalysts to date. Our finding paves a way to develop highly active OER electrocatalysts. PMID:26757358

  10. Nanofibrous electrocatalysts

    DOEpatents

    Liu, Di Jia; Shui, Jianglan; Chen, Chen

    2016-05-24

    A nanofibrous catalyst and method of manufacture. A precursor solution of a transition metal based material is formed into a plurality of interconnected nanofibers by electro-spinning the precursor solution with the nanofibers converted to a catalytically active material by a heat treatment. Selected subsequent treatments can enhance catalytic activity.

  11. Electrocatalyst compositions

    DOEpatents

    Mallouk, Thomas E.; Chan, Benny C.; Reddington, Erik; Sapienza, Anthony; Chen, Guoying; Smotkin, Eugene; Gurau, Bogdan; Viswanathan, Rameshkrishnan; Liu, Renxuan

    2001-09-04

    Compositions for use as catalysts in electrochemical reactions are described. The compositions are alloys prepared from two or more elemental metals selected from platinum, molybdenum, osmium, ruthenium, rhodium, and iridium. Also described are electrode compositions including such alloys and electrochemical reaction devices including such catalysts.

  12. Development of electrocatalysts for fuel cell cathodes: Experimental studies and mathematical modeling

    NASA Astrophysics Data System (ADS)

    Subramanian, Nalini Palaniappan

    The primary objective of this dissertation is to develop electrocatalysts for fuel cell cathodes and to understanding the performance of various cathode materials using mathematical modeling. Recent advances in Proton Exchange Membrane Fuel Cells (PEMFCs) have made them a promising alternative to internal combustion and gasoline driven vehicles. PEMFCs are the best choice for a wide range of portable, stationary and automotive applications because of their high power density and relatively low-temperature operation. However, a major impediment in the commercialization of the fuel cell technology is the cost involved due to the large amount of platinum electrocatalyst used for Oxygen Reduction Reaction (ORR). For example, PEMFCs today do not meet the Department of Energy (DOE) targets for transportation applications (which is 0.4 A/cm2 at 0.8 V and 0.1 A/cm2 at 0.85 V with an MEA cost under $10/kW). To achieve this, precious metal loadings must be reduced to less than 0.2 g/peak kW or 0.05 mg/cm2 of platinum. Platinum loading can be reduced by (i) increasing the utilization of platinum, (ii) alloying platinum with other transition metals, and (iii) developing platinum-free catalysts. In this dissertation, the third approach has been adopted, where a platinum-free cobalt-chelate catalyst supported on modified carbon black substrates has been developed. This catalyst shows less than 100 mV higher overpotential compared to commercial E-TEK 19.1% Pt/C. The modified carbon substrate used in this catalyst can itself act as an ORR catalyst. Here, a highly active metal-free carbon catalyst has been developed for ORR. The second approach to reducing platinum loading has also been adopted by developing 18.8% Pt2.5Co1 catalysts using electroless co-deposition, which showed a performance close to commercial E-TEK 20% Pt 3Co1/C. Finally, a three-phase homogeneous model has been developed for the cathode in a Molten Carbonate Fuel Cell (MCFC) to extract kinetic and conductivity

  13. Development of Molecular Electrocatalysts for CO2 Reduction and H2 Production/Oxidation

    SciTech Connect

    Rakowski DuBois, Mary; DuBois, Daniel L.

    2009-12-15

    The conversion of solar energy to fuels in both natural and artificial photosynthesis requires components for both light harvesting and catalysis. The light-harvesting component generates the electrochemical potentials required to drive fuel-generating reactions that would otherwise be thermodynamically uphill. This review focuses on work from our laboratories on developing molecular electrocatalysts for CO2 reduction and for hydrogen production. A true analog of natural photosynthesis will require the ability to capture CO2 from the atmosphere and reduce it to a useful fuel. Work in our laboratories has focused on both aspects of this problem. Organic compounds such as quinones and inorganic metal complexes can serve as redox active CO2 carriers for concentrating CO2. Catalysts for CO2 reduction to form CO have also been developed based on a [Pd(triphosphine)(solvent)]2+ platform. A required feature for catalytic activity is the presence of a weakly coordinating solvent molecule that can dissociate during the catalytic cycle and provide a vacant coordination site for binding water and assisting C-O bond cleavage. Participation of a second metal in CO2 binding also appears to be required for achieving very active catalysts as suggested by structures of [NiFe] CO dehydrogenase enzymes and the results of studies on complexes containing two [Pd(triphosphine)(solvent)]2+ units. Molecular electrocatalysts for H2 production and oxidation based on [Ni(diphosphine)2]2+ complexes are also described. These catalysts require the optimization of both first and second coordination spheres similar to that of the palladium CO2 reduction catalysts. In this case, structural features of the first coordination sphere can be used to optimize the hydride acceptor ability of nickel needed to achieve heterolytic cleavage of H2. The second coordination sphere can be used to incorporate pendant bases that assist in a number of important functions including H2 binding, H2 cleavage, and the

  14. Operando Analysis of NiFe and Fe Oxyhydroxide Electrocatalysts for Water Oxidation: Detection of Fe⁴⁺ by Mössbauer Spectroscopy.

    PubMed

    Chen, Jamie Y C; Dang, Lianna; Liang, Hanfeng; Bi, Wenli; Gerken, James B; Jin, Song; Alp, E Ercan; Stahl, Shannon S

    2015-12-01

    Nickel-iron oxides/hydroxides are among the most active electrocatalysts for the oxygen evolution reaction. In an effort to gain insight into the role of Fe in these catalysts, we have performed operando Mössbauer spectroscopic studies of a 3:1 Ni:Fe layered hydroxide and a hydrous Fe oxide electrocatalyst. The catalysts were prepared by a hydrothermal precipitation method that enabled catalyst growth directly on carbon paper electrodes. Fe(4+) species were detected in the NiFe hydroxide catalyst during steady-state water oxidation, accounting for up to 21% of the total Fe. In contrast, no Fe(4+) was detected in the Fe oxide catalyst. The observed Fe(4+) species are not kinetically competent to serve as the active site in water oxidation; however, their presence has important implications for the role of Fe in NiFe oxide electrocatalysts. PMID:26601790

  15. Sulfur and Nitrogen Codoped Carbon Tubes as Bifunctional Metal-Free Electrocatalysts for Oxygen Reduction and Hydrogen Evolution in Acidic Media.

    PubMed

    Sun, Tao; Wu, Qiang; Jiang, Yufei; Zhang, Zhiqi; Du, Lingyu; Yang, Lijun; Wang, Xizhang; Hu, Zheng

    2016-07-18

    The technological combination of fuel cells with water electrolysis is an ideal approach to address the problems of growing energy needs and environmental pollution, in which exploring cheap and stable electrocatalysts is the main challenge. Sulfur and nitrogen codoped carbon tubes (SNCTs), prepared by annealing the mixture of amorphous carbonaceous tubes and cysteine, are found to be active bifunctional metal-free electrocatalysts for both oxygen reduction and hydrogen evolution in acidic medium. The optimized SNCT catalyst exhibits a record high onset potential of 851 mV (vs. RHE) for oxygen reduction and concurrent a low overpotential of 76 mV for hydrogen evolution, with superior stability and low cost. The SNCT electrocatalyst could have great potential in proton exchange membrane fuel cells and water splitting devices. PMID:27150558

  16. Graphene-Co3O4 nanocomposite as electrocatalyst with high performance for oxygen evolution reaction

    PubMed Central

    Zhao, Yufei; Chen, Shuangqiang; Sun, Bing; Su, Dawei; Huang, Xiaodan; Liu, Hao; Yan, Yiming; Sun, Kening; Wang, Guoxiu

    2015-01-01

    Graphene-Co3O4 composite with a unique sandwich-architecture was successfully synthesized and applied as an efficient electrocatalyst for oxygen evolution reaction. Field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) analyses confirmed that Co3O4 nanocrystals were homogeneously distributed on both sides of graphene nanosheets. The obtained composite shows enhanced catalytic activities in both alkaline and neutral electrolytes. The onset potential towards the oxygen evolution reaction is 0.406 V (vs. Ag/AgCl) in 1 M KOH solution, and 0.858 V (vs. Ag/AgCl) in neutral phosphate buffer solution (PBS), respectively. The current density of 10 mA/cm2 has been achieved at the overpotential of 313 mV in 1 M KOH and 498 mV in PBS. The graphene-Co3O4 composite also exhibited an excellent stability in both alkaline and neutral electrolytes. In particular, no obvious current density decay was observed after 10 hours testing in alkaline solution and the morphology of the material was well maintained, which could be ascribed to the synergistic effect of combining Co3O4 and graphene. PMID:25559459

  17. Platinum nanocuboids supported on reduced graphene oxide as efficient electrocatalyst for the hydrogen evolution reaction

    NASA Astrophysics Data System (ADS)

    Xu, Guang-Rui; Hui, Jiao-Jiao; Huang, Tan; Chen, Yu; Lee, Jong-Min

    2015-07-01

    Active and stable electrocatalysts for the hydrogen evolution reaction (HER) are highly desirable for hydrogen production. Herein, the cuboid-like platinum nanocrystals (Pt-CNSs) are achieved through a facile L-lysine-assisted hydrothermal reduction method. Then, reduced graphene oxide (RGO) supported Pt-CNSs (Pt-CNSs/RGO) nanohybrids are obtained through the self-assemble of Pt-CNSs on graphene oxide (GO) and followed by NaBH4 reduction. The resulting Pt-CNSs/RGO nanohybrids are characterized by transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, thermogravimetric analysis and Raman, showing that the well-defined Pt-CNSs with 5.8 nm length and 3.0 nm width are uniformly and firmly attached on the RGO surface. Electrochemical tests demonstrate that Pt-CNSs/RGO nanohybrids have superior electrocatalytic activity and stability for the HER than pure Pt-CNSs, demonstrating RGO is an excellent cathode support materials for Pt-CNSs. Meanwhile, the present results indicate that the as-prepared Pt-CNSs/RGO nanohybrids have great potential application in HER.

  18. Hydrogel-derived non-precious electrocatalysts for efficient oxygen reduction

    NASA Astrophysics Data System (ADS)

    You, Bo; Yin, Peiqun; Zhang, Junli; He, Daping; Chen, Gaoli; Kang, Fei; Wang, Huiqiao; Deng, Zhaoxiang; Li, Yadong

    2015-07-01

    The development of highly active, cheap and robust oxygen reduction reaction (ORR) electrocatalysts to replace precious metal platinum is extremely urgent and challenging for renewable energy devices. Herein we report a novel, green and especially facile hydrogel strategy to construct N and B co-doped nanocarbon embedded with Co-based nanoparticles as an efficient non-precious ORR catalyst. The agarose hydrogel provides a general host matrix to achieve a homogeneous distribution of key precursory components including cobalt (II) acetate and buffer salts, which, upon freeze-drying and carbonization, produces the highly active ORR catalyst. The gel buffer containing Tris base, boric acid and ethylenediaminetetraacetic acid, commonly adopted for pH and ionic strength control, plays distinctively different roles here. These include a green precursor for N- and B-doping, a salt porogen and a Co2+ chelating agent, all contributing to the excellent ORR activity. This hydrogel-based process is potentially generalizable for many other catalytic materials.

  19. Coupled molybdenum carbide and reduced graphene oxide electrocatalysts for efficient hydrogen evolution.

    PubMed

    Li, Ji-Sen; Wang, Yu; Liu, Chun-Hui; Li, Shun-Li; Wang, Yu-Guang; Dong, Long-Zhang; Dai, Zhi-Hui; Li, Ya-Fei; Lan, Ya-Qian

    2016-01-01

    Electrochemical water splitting is one of the most economical and sustainable methods for large-scale hydrogen production. However, the development of low-cost and earth-abundant non-noble-metal catalysts for the hydrogen evolution reaction remains a challenge. Here we report a two-dimensional coupled hybrid of molybdenum carbide and reduced graphene oxide with a ternary polyoxometalate-polypyrrole/reduced graphene oxide nanocomposite as a precursor. The hybrid exhibits outstanding electrocatalytic activity for the hydrogen evolution reaction and excellent stability in acidic media, which is, to the best of our knowledge, the best among these reported non-noble-metal catalysts. Theoretical calculations on the basis of density functional theory reveal that the active sites for hydrogen evolution stem from the pyridinic nitrogens, as well as the carbon atoms, in the graphene. In a proof-of-concept trial, an electrocatalyst for hydrogen evolution is fabricated, which may open new avenues for the design of nanomaterials utilizing POMs/conducting polymer/reduced-graphene oxide nanocomposites. PMID:27032372

  20. A dinuclear copper(II) electrocatalyst both water reduction and oxidation

    NASA Astrophysics Data System (ADS)

    Zhou, Ling-Ling; Fang, Ting; Cao, Jie-Ping; Zhu, Zhi-Hong; Su, Xiao-Ting; Zhan, Shu-Zhong

    2015-01-01

    Splitting water is a key challenge in the production of chemical fuels from electricity. Although several catalysts have been developed for these reactions, substantial challenges remain towards the ultimate goal of an efficient, inexpensive and robust electrocatalyst. Until now, there is as yet no report on both water oxidation and reduction by identical catalyst. Reported here is the first soluble copper-based catalyst, Cu(Me2oxpn)Cu(OH)2] 1 (Me2oxpn: N,N‧-bis(2,2‧-dimethyl-3-aminopropyl)oxamido) for both electrolytic water oxidation and reduction. Water oxidation occurs at an overpotential of 636 mV vs SHE to give O2 with a turnover frequency (TOF) of ∼2.14 s-1. Electrochemical studies also indicate that 1 is a soluble molecular species, that is among the most rapid homogeneous water reduction catalysts, with a TOF of 654 mol of hydrogen per mole of catalyst per hour at an overpotential of 789 mV vs SHE (pH 7.0). Sustained water reduction catalysis occurs at glassy carbon (GC) to give H2 over a 32 h electrolysis period with 95% Faradaic yield and no observable decomposition of the catalyst.

  1. Impact of Polymer Electrolyte Membrane Degradation Products on Oxygen Reduction Reaction Activity for Platinum Electrocatalysts

    SciTech Connect

    Christ, J. M.; Neyerlin, K. C.; Wang, H.; Richards, R.; Dinh, H. N.

    2014-10-30

    The impact of model membrane degradation compounds on the relevant electrochemical parameters for the oxygen reduction reaction (i.e. electrochemical surface area and catalytic activity), was studied for both polycrystalline Pt and carbon supported Pt electrocatalysts. Model compounds, representing previously published, experimentally determined polymer electrolyte membrane degradation products, were in the form of perfluorinated organic acids that contained combinations of carboxylic and/or sulfonic acid functionality. Perfluorinated carboxylic acids of carbon chain length C1 – C6 were found to have an impact on electrochemical surface area (ECA). The longest chain length acid also hindered the observed oxygen reduction reaction (ORR) performance, resulting in a 17% loss in kinetic current (determined at 0.9 V). Model compounds containing sulfonic acid functional groups alone did not show an effect on Pt ECA or ORR activity. Lastly, greater than a 44% loss in ORR activity at 0.9V was observed for diacid model compounds DA-Naf (perfluoro(2-methyl-3-oxa-5-sulfonic pentanoic) acid) and DA-3M (perfluoro(4-sulfonic butanoic) acid), which contained both sulfonic and carboxylic acid functionalities.

  2. Impact of Polymer Electrolyte Membrane Degradation Products on Oxygen Reduction Reaction Activity for Platinum Electrocatalysts

    DOE PAGESBeta

    Christ, J. M.; Neyerlin, K. C.; Wang, H.; Richards, R.; Dinh, H. N.

    2014-10-30

    The impact of model membrane degradation compounds on the relevant electrochemical parameters for the oxygen reduction reaction (i.e. electrochemical surface area and catalytic activity), was studied for both polycrystalline Pt and carbon supported Pt electrocatalysts. Model compounds, representing previously published, experimentally determined polymer electrolyte membrane degradation products, were in the form of perfluorinated organic acids that contained combinations of carboxylic and/or sulfonic acid functionality. Perfluorinated carboxylic acids of carbon chain length C1 – C6 were found to have an impact on electrochemical surface area (ECA). The longest chain length acid also hindered the observed oxygen reduction reaction (ORR) performance, resultingmore » in a 17% loss in kinetic current (determined at 0.9 V). Model compounds containing sulfonic acid functional groups alone did not show an effect on Pt ECA or ORR activity. Lastly, greater than a 44% loss in ORR activity at 0.9V was observed for diacid model compounds DA-Naf (perfluoro(2-methyl-3-oxa-5-sulfonic pentanoic) acid) and DA-3M (perfluoro(4-sulfonic butanoic) acid), which contained both sulfonic and carboxylic acid functionalities.« less

  3. Highly porous non-precious bimetallic electrocatalysts for efficient hydrogen evolution

    SciTech Connect

    Lu, Qi; Hutchings, Gregory S.; Yu, Weiting; Zhou, Yang; Forest, Robert V.; Tao, Runzhe; Rosen, Jonathan; Yonemoto, Bryan T.; Cao, Zeyuan; Zheng, Haimei; Xiao, John Q.; Jiao, Feng; Chen, Jingguang G.

    2015-03-16

    One of the key components of carbon dioxide-free hydrogen production is a robust and efficient non-precious metal catalyst for the hydrogen evolution reaction. We report that a hierarchical nanoporous copper-titanium bimetallic electrocatalyst is able to produce hydrogen from water under a mild overpotential at more than twice the rate of state-of-the- art carbon-supported platinum catalyst. Although both copper and titanium are known to be poor hydrogen evolution catalysts, the combination of these two elements creates unique copper-copper-titanium hollow sites, which have a hydrogen-binding energy very similar to that of platinum, resulting in an exceptional hydrogen evolution activity. Moreover, the hierarchical porosity of the nanoporous-copper titanium catalyst also contributes to its high hydrogen evolution activity, because it provides a large-surface area for electrocatalytic hydrogen evolution, and improves the mass transport properties. Moreover, the catalyst is self-supported, eliminating the overpotential associated with the catalyst/support interface.

  4. Rapid room-temperature synthesis of nanocrystalline spinels as oxygen reduction and evolution electrocatalysts.

    PubMed

    Cheng, Fangyi; Shen, Jian; Peng, Bo; Pan, Yuede; Tao, Zhanliang; Chen, Jun

    2011-01-01

    Spinels can serve as alternative low-cost bifunctional electrocatalysts for oxygen reduction/evolution reactions (ORR/OER), which are the key barriers in various electrochemical devices such as metal-air batteries, fuel cells and electrolysers. However, conventional ceramic synthesis of crystalline spinels requires an elevated temperature, complicated procedures and prolonged heating time, and the resulting product exhibits limited electrocatalytic performance. It has been challenging to develop energy-saving, facile and rapid synthetic methodologies for highly active spinels. In this Article, we report the synthesis of nanocrystalline M(x)Mn(3-x)O(4) (M = divalent metals) spinels under ambient conditions and their electrocatalytic application. We show rapid and selective formation of tetragonal or cubic M(x)Mn(3-x)O(4) from the reduction of amorphous MnO(2) in aqueous M(2+) solution. The prepared Co(x)Mn(3-x)O(4) nanoparticles manifest considerable catalytic activity towards the ORR/OER as a result of their high surface areas and abundant defects. The newly discovered phase-dependent electrocatalytic ORR/OER characteristics of Co-Mn-O spinels are also interpreted by experiment and first-principle theoretical studies. PMID:21160522

  5. Cobalt/copper-decorated carbon nanofibers as novel non-precious electrocatalyst for methanol electrooxidation

    NASA Astrophysics Data System (ADS)

    Barakat, Nasser A. M.; El-Newehy, Mohamed; Al-Deyab, Salem S.; Kim, Hak Yong

    2014-01-01

    In this study, Co/Cu-decorated carbon nanofibers are introduced as novel electrocatalyst for methanol oxidation. The introduced nanofibers have been prepared based on graphitization of poly(vinyl alcohol) which has high carbon content compared to many polymer precursors for carbon nanofiber synthesis. Typically, calcination in argon atmosphere of electrospun nanofibers composed of cobalt acetate tetrahydrate, copper acetate monohydrate, and poly(vinyl alcohol) leads to form carbon nanofibers decorated by CoCu nanoparticles. The graphitization of the poly(vinyl alcohol) has been enhanced due to presence of cobalt which acts as effective catalyst. The physicochemical characterization affirmed that the metallic nanoparticles are sheathed by thin crystalline graphite layer. Investigation of the electrocatalytic activity of the introduced nanofibers toward methanol oxidation indicates good performance, as the corresponding onset potential was small compared to many reported materials; 310 mV (vs. Ag/AgCl electrode) and a current density of 12 mA/cm2 was obtained. Moreover, due to the graphite shield, good stability was observed. Overall, the introduced study opens new avenue for cheap and stable transition metals-based nanostructures as non-precious catalysts for fuel cell applications.

  6. Highly porous non-precious bimetallic electrocatalysts for efficient hydrogen evolution

    PubMed Central

    Lu, Qi; Hutchings, Gregory S.; Yu, Weiting; Zhou, Yang; Forest, Robert V.; Tao, Runzhe; Rosen, Jonathan; Yonemoto, Bryan T.; Cao, Zeyuan; Zheng, Haimei; Xiao, John Q.; Jiao, Feng; Chen, Jingguang G.

    2015-01-01

    A robust and efficient non-precious metal catalyst for hydrogen evolution reaction is one of the key components for carbon dioxide-free hydrogen production. Here we report that a hierarchical nanoporous copper-titanium bimetallic electrocatalyst is able to produce hydrogen from water under a mild overpotential at more than twice the rate of state-of-the-art carbon-supported platinum catalyst. Although both copper and titanium are known to be poor hydrogen evolution catalysts, the combination of these two elements creates unique copper-copper-titanium hollow sites, which have a hydrogen-binding energy very similar to that of platinum, resulting in an exceptional hydrogen evolution activity. In addition, the hierarchical porosity of the nanoporous copper-titanium catalyst also contributes to its high hydrogen evolution activity, because it provides a large-surface area for electrocatalytic hydrogen evolution, and improves the mass transport properties. Moreover, the catalyst is self-supported, eliminating the overpotential associated with the catalyst/support interface. PMID:25910892

  7. Is Ammonium Peroxydisulate Indispensable for Preparation of Aniline-Derived Iron-Nitrogen-Carbon Electrocatalysts?

    PubMed

    Xie, Nan-Hong; Yan, Xiang-Hui; Xu, Bo-Qing

    2016-09-01

    Iron and nitrogen co-doped carbon (Fe-N-C) materials are among the most active non-precious metal catalysts that could replace Pt-based electrocatalysts for the oxygen reduction reaction (ORR) in fuel cells and metal-air batteries. The synthesis of the Fe-N-C catalysts often involves the use of aniline as the precursor for both N and C and ammonium peroxydisulfate (APS) as an indispensable oxidative initiator for aniline polymerization. Herein, a detailed structure and catalytic ORR performance comparison of aniline-derived Fe-N-C catalysts synthesized with and without the use of APS is reported. The APS-free preparation, which uses Fe(III) ions as the Fe source as well as the aniline polymerization initiator, results in a simple Fe-N-C catalyst with a high activity for the ORR. We show that APS is not necessary for the preparation and even detrimental to the performance of the catalyst. PMID:27514790

  8. Pentlandite rocks as sustainable and stable efficient electrocatalysts for hydrogen generation.

    PubMed

    Konkena, Bharathi; Junge Puring, Kai; Sinev, Ilya; Piontek, Stefan; Khavryuchenko, Oleksiy; Dürholt, Johannes P; Schmid, Rochus; Tüysüz, Harun; Muhler, Martin; Schuhmann, Wolfgang; Apfel, Ulf-Peter

    2016-01-01

    The need for sustainable catalysts for an efficient hydrogen evolution reaction is of significant interest for modern society. Inspired by comparable structural properties of [FeNi]-hydrogenase, here we present the natural ore pentlandite (Fe4.5Ni4.5S8) as a direct 'rock' electrode material for hydrogen evolution under acidic conditions with an overpotential of 280 mV at 10 mA cm(-2). Furthermore, it reaches a value as low as 190 mV after 96 h of electrolysis due to surface sulfur depletion, which may change the electronic structure of the catalytically active nickel-iron centres. The 'rock' material shows an unexpected catalytic activity with comparable overpotential and Tafel slope to some well-developed metallic or nanostructured catalysts. Notably, the 'rock' material offers high current densities (≤650 mA cm(-2)) without any loss in activity for approximately 170 h. The superior hydrogen evolution performance of pentlandites as 'rock' electrode labels this ore as a promising electrocatalyst for future hydrogen-based economy. PMID:27461840

  9. Fast and efficient molecular electrocatalysts for H{sub 2} production: Using hydrogenase enzymes as guides

    SciTech Connect

    Yang, Jenny Y.; Bullock, R. Morris; DuBois, M. Rakowski; DuBois, Daniel L.

    2011-01-01

    Hydrogen generation using solar energy will require the development of efficient electrocatalysts for proton reduction. This article discusses the important role that proton movement plays in hydrogenase enzymes and potential devices for solar generation. Studies of hydrogenase enzymes provide many important design principles for the development of simpler molecular catalysts. These principles are illustrated with examples from the literature and from the authors’ laboratories. In particular, pendant bases incorporated in the second coordination sphere of catalytic molecules play a number of important roles that are crucial to efficient catalysis. These roles include acting as relays to move protons between the metal center and solution, promoting intra- and intermolecular proton transfer reactions, coupling proton and electron transfer reactions, assisting heterolytic cleavage of hydrogen, and stabilizing critical reaction intermediates. The importance of controlling proton movement on the molecular scale underscores the importance of a similar degree of control in devices designed for the solar production of hydrogen or any fuel generation process involving multiple electrons and protons.

  10. Fast and efficient molecular electrocatalysts for H2 production: Using hydrogenase enzymes as guides

    SciTech Connect

    Yang, Jenny Y.; Bullock, R. Morris; Rakowski DuBois, Mary; DuBois, Daniel L.

    2011-01-15

    Hydrogen generation using solar energy will require the development of efficient electrocatalysts for proton reduction. This article discusses the important role that proton movement plays in hydrogenase enzymes and potentials devices for solar generation. Studies of hydrogenase enzymes provide many import design principles for the development of simpler molecular catalysts. These principles are illustrated with examples from the literature and from the authors’ laboratories. In particular, pendant bases incorporated in the second coordination sphere of catalytic molecules play a number of important roles that are crucial to efficient catalysis. These include acting as relays to move protons between the metal center and solution, promoting intra- and inter-molecular proton transfer reactions, coupling proton and electron transfer reactions, assisting heterolytic cleavage of hydrogen, and stabilizing critical reaction intermediates. The importance of controlling proton movement on the molecular scale underscores the importance of a similar degree of control in devices designed for the solar production of hydrogen or any fuel generation process involving multiple electrons and protons. This material is based upon work supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the US Department of Energy, Office of Science, Office of Basic Energy Sciences.

  11. Supported Core@Shell Electrocatalysts for Fuel Cells: Close Encounter with Reality

    PubMed Central

    Hwang, Seung Jun; Yoo, Sung Jong; Shin, Jungho; Cho, Yong-Hun; Jang, Jong Hyun; Cho, Eunae; Sung, Yung-Eun; Nam, Suk Woo; Lim, Tae-Hoon; Lee, Seung-Cheol; Kim, Soo-Kil

    2013-01-01

    Core@shell electrocatalysts for fuel cells have the advantages of a high utilization of Pt and the modification of its electronic structures toward enhancement of the activities. In this study, we suggest both a theoretical background for the design of highly active and stable core@shell/C and a novel facile synthetic strategy for their preparation. Using density functional theory calculations guided by the oxygen adsorption energy and vacancy formation energy, Pd3Cu1@Pt/C was selected as the most suitable candidate for the oxygen reduction reaction in terms of its activity and stability. These predictions were experimentally verified by the surfactant-free synthesis of Pd3Cu1/C cores and the selective Pt shell formation using a Hantzsch ester as a reducing agent. In a similar fashion, Pd@Pd4Ir6/C catalyst was also designed and synthesized for the hydrogen oxidation reaction. The developed catalysts exhibited high activity, high selectivity, and 4,000 h of long-term durability at the single-cell level. PMID:23419683

  12. Hybrid NiCoOx adjacent to Pd nanoparticles as a synergistic electrocatalyst for ethanol oxidation

    NASA Astrophysics Data System (ADS)

    Wang, Wei; Yang, Yan; Liu, Yanqin; Zhang, Zhe; Dong, Wenkui; Lei, Ziqiang

    2015-01-01

    To improve the electrocatalytic activity of Pd for ethanol oxidation, hybrid NiCoOx adjacent to Pd catalyst (Pd-NiCoOx/C) is successfully synthesized. Physical characterization shows NiCoOx is closely adjacent to Pd nanoparticles in Pd-NiCoOx/C catalyst, which leads to Strong Metal-Support Interactions (SMSI) between the NiCoOx and Pd nanoparticles, in favor of the electrocatalytic properties. The Pd-NiCoOx/C catalyst is estimated to own larger electrochemically active surface area than Pd/C and Pd-NiO/C catalysts. Moreover, compared to Pd/C catalyst, the onset potential of Pd-NiCoOx/C catalyst is negative 40 mV for ethanol oxidation. Noticeably, the current density of Pd-NiCoOx/C catalyst is 2.05 and 1.43 times higher contrasted to Pd/C and Pd-NiO/C catalysts accordingly. Importantly, the Pd-NiCoOx/C catalyst exhibits better stability during ethanol oxidation, which is a promising electrocatalyst for application in direct alkaline alcohol fuel cells.

  13. Advanced oxygen reduction electrocatalyst based on nitrogen-doped graphene derived from edible sugar and urea.

    PubMed

    Pan, Fuping; Jin, Jutao; Fu, Xiaogang; Liu, Qiao; Zhang, Junyan

    2013-11-13

    Designing and fabricating advanced oxygen reduction reaction (ORR) electrocatalysts is critical importance for the sake of promoting widespread application of fuel cells. In this work, we report that nitrogen-doped graphene (NG), synthesized via one-step pyrolysis of naturally available sugar in the presence of urea, can serve as metal-free ORR catalyst with excellent electrocatalytic activity, outstanding methanol crossover resistance as well as long-term operation stability in alkaline medium. The resultant NG1000 (annealed at 1000 °C) exhibits a high kinetic current density of 21.33 mA/cm(2) at -0.25 V (vs Ag/AgCl) in O2-saturated 0.1 M KOH electrolyte, compared with 16.01 mA/cm(2) at -0.25 V for commercial 20 wt % Pt/C catalyst. Notably, the NG1000 possesses comparable ORR half-wave potential to Pt/C. The effects of pyrolysis temperature on the physical prosperity and ORR performance of NG are also investigated. The obtained results demonstrate that high activation temperature (1000 °C) results in low nitrogen doping level, high graphitization degree, enhanced electrical conductivity, and high surface area and pore volume, which make a synergetic contribution to enhancing the ORR performance for NG. PMID:24099362

  14. Highly active oxygen reduction non-platinum group metal electrocatalyst without direct metal-nitrogen coordination

    NASA Astrophysics Data System (ADS)

    Strickland, Kara; Miner, Elise; Jia, Qingying; Tylus, Urszula; Ramaswamy, Nagappan; Liang, Wentao; Sougrati, Moulay-Tahar; Jaouen, Frédéric; Mukerjee, Sanjeev

    2015-06-01

    Replacement of noble metals in catalysts for cathodic oxygen reduction reaction with transition metals mostly create active sites based on a composite of nitrogen-coordinated transition metal in close concert with non-nitrogen-coordinated carbon-embedded metal atom clusters. Here we report a non-platinum group metal electrocatalyst with an active site devoid of any direct nitrogen coordination to iron that outperforms the benchmark platinum-based catalyst in alkaline media and is comparable to its best contemporaries in acidic media. In situ X-ray absorption spectroscopy in conjunction with ex situ microscopy clearly shows nitrided carbon fibres with embedded iron particles that are not directly involved in the oxygen reduction pathway. Instead, the reaction occurs primarily on the carbon-nitrogen structure in the outer skin of the nitrided carbon fibres. Implications include the potential of creating greater active site density and the potential elimination of any Fenton-type process involving exposed iron ions culminating in peroxide initiated free-radical formation.

  15. Plasma nitriding induced growth of Pt-nanowire arrays as high performance electrocatalysts for fuel cells.

    PubMed

    Du, Shangfeng; Lin, Kaijie; Malladi, Sairam K; Lu, Yaxiang; Sun, Shuhui; Xu, Qiang; Steinberger-Wilckens, Robert; Dong, Hanshan

    2014-01-01

    In this work, we demonstrate an innovative approach, combing a novel active screen plasma (ASP) technique with green chemical synthesis, for a direct fabrication of uniform Pt nanowire arrays on large-area supports. The ASP treatment enables in-situ N-doping and surface modification to the support surface, significantly promoting the uniform growth of tiny Pt nuclei which directs the growth of ultrathin single-crystal Pt nanowire (2.5-3 nm in diameter) arrays, forming a three-dimensional (3D) nano-architecture. Pt nanowire arrays in-situ grown on the large-area gas diffusion layer (GDL) (5 cm(2)) can be directly used as the catalyst electrode in fuel cells. The unique design brings in an extremely thin electrocatalyst layer, facilitating the charge transfer and mass transfer properties, leading to over two times higher power density than the conventional Pt nanoparticle catalyst electrode in real fuel cell environment. Due to the similar challenges faced with other nanostructures and the high availability of ASP for other material surfaces, this work will provide valuable insights and guidance towards the development of other new nano-architectures for various practical applications. PMID:25241800

  16. Cobalt/copper-decorated carbon nanofibers as novel non-precious electrocatalyst for methanol electrooxidation

    PubMed Central

    2014-01-01

    In this study, Co/Cu-decorated carbon nanofibers are introduced as novel electrocatalyst for methanol oxidation. The introduced nanofibers have been prepared based on graphitization of poly(vinyl alcohol) which has high carbon content compared to many polymer precursors for carbon nanofiber synthesis. Typically, calcination in argon atmosphere of electrospun nanofibers composed of cobalt acetate tetrahydrate, copper acetate monohydrate, and poly(vinyl alcohol) leads to form carbon nanofibers decorated by CoCu nanoparticles. The graphitization of the poly(vinyl alcohol) has been enhanced due to presence of cobalt which acts as effective catalyst. The physicochemical characterization affirmed that the metallic nanoparticles are sheathed by thin crystalline graphite layer. Investigation of the electrocatalytic activity of the introduced nanofibers toward methanol oxidation indicates good performance, as the corresponding onset potential was small compared to many reported materials; 310 mV (vs. Ag/AgCl electrode) and a current density of 12 mA/cm2 was obtained. Moreover, due to the graphite shield, good stability was observed. Overall, the introduced study opens new avenue for cheap and stable transition metals-based nanostructures as non-precious catalysts for fuel cell applications. PMID:24387682

  17. Advanced zinc-air batteries based on high-performance hybrid electrocatalysts.

    PubMed

    Li, Yanguang; Gong, Ming; Liang, Yongye; Feng, Ju; Kim, Ji-Eun; Wang, Hailiang; Hong, Guosong; Zhang, Bo; Dai, Hongjie

    2013-01-01

    Primary and rechargeable Zn-air batteries could be ideal energy storage devices with high energy and power density, high safety and economic viability. Active and durable electrocatalysts on the cathode side are required to catalyse oxygen reduction reaction during discharge and oxygen evolution reaction during charge for rechargeable batteries. Here we developed advanced primary and rechargeable Zn-air batteries with novel CoO/carbon nanotube hybrid oxygen reduction catalyst and Ni-Fe-layered double hydroxide oxygen evolution catalyst for the cathode. These catalysts exhibited higher catalytic activity and durability in concentrated alkaline electrolytes than precious metal Pt and Ir catalysts. The resulting primary Zn-air battery showed high discharge peak power density ~265 mW cm(-2), current density ~200 mA cm(-2) at 1 V and energy density >700 Wh kg(-1). Rechargeable Zn-air batteries in a tri-electrode configuration exhibited an unprecedented small charge-discharge voltage polarization of ~0.70 V at 20 mA cm(-2), high reversibility and stability over long charge and discharge cycles. PMID:23651993

  18. Highly Active and Durable Nanocrystal-Decorated Bifunctional Electrocatalyst for Rechargeable Zinc-Air Batteries.

    PubMed

    Lee, Dong Un; Park, Moon Gyu; Park, Hey Woong; Seo, Min Ho; Wang, Xiaolei; Chen, Zhongwei

    2015-09-21

    A highly active and durable bifunctional electrocatalyst that consists of cobalt oxide nanocrystals (Co3 O4 NC) decorated on the surface of N-doped carbon nanotubes (N-CNT) is introduced as effective electrode material for electrically rechargeable zinc-air batteries. This active hybrid catalyst is synthesized by a facile surfactant-assisted method to produce Co3 O4 NC that are then decorated on the surface of N-CNT through hydrophobic attraction. Confirmed by half-cell testing, Co3 O4 NC/N-CNT demonstrates superior oxygen reduction and oxygen evolution catalytic activities and has a superior electrochemical stability compared to Pt/C and Ir/C. Furthermore, rechargeable zinc-air battery testing of Co3 O4 NC/N-CNT reveals superior galvanodynamic charge and discharge voltages with a significantly extended cycle life of over 100 h, which suggests its potential as a replacement for precious-metal-based catalysts for electric vehicles and grid energy storage applications. PMID:26373363

  19. Nanoscale conductive niobium oxides made through low temperature phase transformation for electrocatalyst support

    SciTech Connect

    Huang, K; Li, YF; Yan, LT; Xing, YC

    2014-01-01

    We report an effective approach to synthesize nanoscale Nb2O5 coated on carbon nanotubes (CNTs) and transform it at low temperatures to the conductive form of NbO2. The latter, when used as a Pt electrocatalyst support, shows significant enhancement in catalyst activity and durability in the oxygen reduction reaction (ORR). Direct phase transformation of Nb2O5 to NbO2 often requires temperatures above 1000 degrees C. Here we show that this can be achieved at a much lower temperature (e.g. 700 degrees C) if the niobium oxide is first activated with carbon. Low temperature processing allows retaining nanostructures of the oxide without sintering, keeping its high surface areas needed for being a catalyst support. We further show that Pt supported on the conductive oxides on CNTs has two times higher mass activity for the ORR than on bare CNTs. The electrochemical stability of Pt was also outstanding, with only ca. 5% loss in electrochemical surface areas and insignificant reduction in half-wave potential in ORR after 5000 potential cycles.

  20. Highly Efficient and Robust Nickel Phosphides as Bifunctional Electrocatalysts for Overall Water-Splitting.

    PubMed

    Li, Jiayuan; Li, Jing; Zhou, Xuemei; Xia, Zhaoming; Gao, Wei; Ma, Yuanyuan; Qu, Yongquan

    2016-05-01

    To search for the efficient non-noble metal based and/or earth-abundant electrocatalysts for overall water-splitting is critical to promote the clean-energy technologies for hydrogen economy. Herein, we report nickel phosphide (NixPy) catalysts with the controllable phases as the efficient bifunctional catalysts for water electrolysis. The phases of NixPy were determined by the temperatures of the solid-phase reaction between the ultrathin Ni(OH)2 plates and NaH2PO2·H2O. The NixPy with the richest Ni5P4 phase synthesized at 325 °C (NixPy-325) delivered efficient and robust catalytic performance for hydrogen evolution reaction (HER) in the electrolytes with a wide pH range. The NixPy-325 catalysts also exhibited a remarkable performance for oxygen evolution reaction (OER) in a strong alkaline electrolyte (1.0 M KOH) due to the formation of surface NiOOH species. Furthermore, the bifunctional NixPy-325 catalysts enabled a highly performed overall water-splitting with ∼100% Faradaic efficiency in 1.0 M KOH electrolyte, in which a low applied external potential of 1.57 V led to a stabilized catalytic current density of 10 mA/cm(2) over 60 h. PMID:27064172

  1. Coupled molybdenum carbide and reduced graphene oxide electrocatalysts for efficient hydrogen evolution

    PubMed Central

    Li, Ji-Sen; Wang, Yu; Liu, Chun-Hui; Li, Shun-Li; Wang, Yu-Guang; Dong, Long-Zhang; Dai, Zhi-Hui; Li, Ya-Fei; Lan, Ya-Qian

    2016-01-01

    Electrochemical water splitting is one of the most economical and sustainable methods for large-scale hydrogen production. However, the development of low-cost and earth-abundant non-noble-metal catalysts for the hydrogen evolution reaction remains a challenge. Here we report a two-dimensional coupled hybrid of molybdenum carbide and reduced graphene oxide with a ternary polyoxometalate-polypyrrole/reduced graphene oxide nanocomposite as a precursor. The hybrid exhibits outstanding electrocatalytic activity for the hydrogen evolution reaction and excellent stability in acidic media, which is, to the best of our knowledge, the best among these reported non-noble-metal catalysts. Theoretical calculations on the basis of density functional theory reveal that the active sites for hydrogen evolution stem from the pyridinic nitrogens, as well as the carbon atoms, in the graphene. In a proof-of-concept trial, an electrocatalyst for hydrogen evolution is fabricated, which may open new avenues for the design of nanomaterials utilizing POMs/conducting polymer/reduced-graphene oxide nanocomposites. PMID:27032372

  2. Tungsten disulphide nanorattle: A new type of high performance electrocatalyst for hydrogen evolution reaction

    NASA Astrophysics Data System (ADS)

    Wen, Yan; Xia, Yongde; Zhang, Shaowei

    2016-03-01

    A new form of nanorattle, WS2@WS2 nanorattle, is prepared for the first time by direct sulphidation of pre-synthesised W@WS2 nanorattle template at 350 °C. Its microstructural and crystalline structures are characterized, and its electrocatalytic activity and stability in the hydrogen evolution reaction examined. WS2 nanoflakes are formed in-situ from sulphidation of the original W cores, and remain in the final WS2@WS2 nanorattles. They are well dispersed, exposing effectively their edges (catalytically active sites) to the reacting species. Consequently, the as-prepared WS2@WS2 nanorattles exhibit excellent electrocatalytic activity and stability. This finding, along with the novel synthesis technique developed, makes WS2@WS2 nanorattle a very promising electrocatalyst for future hydrogen generation. Furthermore, the synthesis strategy used in this work can be readily extended/modified to fabricate other important types of transitional metal nanorattles (e.g., MoS2@MoS2 MoSe2@MoS2 and WC@WS2), potentially benefiting more application areas.

  3. Stabilization of Platinum Nanoparticle Electrocatalysts for Oxygen Reduction Using Poly(diallyldimethylammonium chloride)

    SciTech Connect

    Zhang, Sheng; Shao, Yuyan; Yin, Geping; Lin, Yuehe

    2009-10-29

    A long-chain polyelectrolyte, poly(diallyldimethylammonium chloride) (PDDA), has been employed to stabilize platinum nanoparticles for oxygen reduction in polymer electrolyte membrane (PEM) fuel cells. Pt nanoparticles were synthesized by reducing H2PtCl6 with NaBH4 in the presence of PDDA and then deposited on carbon support (PDDA-Pt/C). Transmission electron microscope images showed that Pt nanoparticles of PDDA-Pt/C are uniformly dispersed on carbon support with a mean size of about 2.2 nm (2.1 nm for commercial Etek-Pt/C). PDDA-Pt/C exhibited a higher activity towards oxygen reduction reaction (ORR) than Etek-Pt/C. The durability of PDDA-Pt/C was improved by a factor of 2 as compared with Etek-Pt/C. X-ray photoelectron spectroscopy characterization of PDDA-Pt/C revealed the interaction between Pt nanoparticles and PDDA, which increased Pt oxidation potential. PDDA-Nafion ionic crosslinking "entraps" Pt nanoparticles and prevents Pt nanoparticles from migrating/agglomerating on or detaching from carbon support. This provides a promising strategy to improve both the durability and activity of electrocatalysts for fuel cells.

  4. Hydrogel-derived non-precious electrocatalysts for efficient oxygen reduction

    PubMed Central

    You, Bo; Yin, Peiqun; Zhang, Junli; He, Daping; Chen, Gaoli; Kang, Fei; Wang, Huiqiao; Deng, Zhaoxiang; Li, Yadong

    2015-01-01

    The development of highly active, cheap and robust oxygen reduction reaction (ORR) electrocatalysts to replace precious metal platinum is extremely urgent and challenging for renewable energy devices. Herein we report a novel, green and especially facile hydrogel strategy to construct N and B co-doped nanocarbon embedded with Co-based nanoparticles as an efficient non-precious ORR catalyst. The agarose hydrogel provides a general host matrix to achieve a homogeneous distribution of key precursory components including cobalt (II) acetate and buffer salts, which, upon freeze-drying and carbonization, produces the highly active ORR catalyst. The gel buffer containing Tris base, boric acid and ethylenediaminetetraacetic acid, commonly adopted for pH and ionic strength control, plays distinctively different roles here. These include a green precursor for N- and B-doping, a salt porogen and a Co2+ chelating agent, all contributing to the excellent ORR activity. This hydrogel-based process is potentially generalizable for many other catalytic materials. PMID:26130371

  5. A novel sputtered Pd mesh architecture as an advanced electrocatalyst for highly efficient hydrogen production

    NASA Astrophysics Data System (ADS)

    de Lucas-Consuegra, Antonio; de la Osa, Ana R.; Calcerrada, Ana B.; Linares, José J.; Horwat, David

    2016-07-01

    This study reports the preparation, characterization and testing of a sputtered Pd mesh-like anode as an advanced electrocatalyst for H2 production from alkaline ethanol solutions in an Alkaline Membrane Electrolyzer (AEM). Pd anodic catalyst is prepared by magnetron sputtering technique onto a microfiber carbon paper support. Scanning Electron Microscopy images reveal that the used preparation technique enables to cover the surface of the carbon microfibers exposed to the Pd target, leading to a continuous network that also maintains part of the original carbon paper macroporosity. Such novel anodic architecture (organic binder free) presents an excellent electro-chemical performance, with a maximum current density of 700 mA cm-2 at 1.3 V, and, concomitantly, a large H2 production rate with low energy requirement compared to water electrolysis. Potassium hydroxide emerges as the best electrolyte, whereas temperature exerts the expected promotional effect up to 90 °C. On the other hand, a 1 mol L-1 ethanol solution is enough to guarantee an efficient fuel supply without any mass transfer limitation. The proposed system also demonstrates to remain stable over 150 h of operation along five consecutives cycles, producing highly pure H2 (99.999%) at the cathode and potassium acetate as the main anodic product.

  6. An oxygen reduction electrocatalyst based on carbon nanotube-graphene complexes.

    PubMed

    Li, Yanguang; Zhou, Wu; Wang, Hailiang; Xie, Liming; Liang, Yongye; Wei, Fei; Idrobo, Juan-Carlos; Pennycook, Stephen J; Dai, Hongjie

    2012-06-01

    Oxygen reduction reaction catalysts based on precious metals such as platinum or its alloys are routinely used in fuel cells because of their high activity. Carbon-supported materials containing metals such as iron or cobalt as well as nitrogen impurities have been proposed to increase scalability and reduce costs, but these alternatives usually suffer from low activity and/or gradual deactivation during use. Here, we show that few-walled carbon nanotubes, following outer wall exfoliation via oxidation and high-temperature reaction with ammonia, can act as an oxygen reduction reaction electrocatalyst in both acidic and alkaline solutions. Under a unique oxidation condition, the outer walls of the few-walled carbon nanotubes are partially unzipped, creating nanoscale sheets of graphene attached to the inner tubes. The graphene sheets contain extremely small amounts of irons originated from nanotube growth seeds, and nitrogen impurities, which facilitate the formation of catalytic sites and boost the activity of the catalyst, as revealed by atomic-scale microscopy and electron energy loss spectroscopy. Whereas the graphene sheets formed from the unzipped part of the outer wall of the nanotubes are responsible for the catalytic activity, the inner walls remain intact and retain their electrical conductivity, which facilitates charge transport during electrocatalysis. PMID:22635099

  7. Synthesis of highly active and dual-functional electrocatalysts for methanol oxidation and oxygen reduction reactions

    NASA Astrophysics Data System (ADS)

    Zhao, Qi; Zhang, Geng; Xu, Guangran; Li, Yingjun; Liu, Baocang; Gong, Xia; Zheng, Dafang; Zhang, Jun; Wang, Qin

    2016-12-01

    The promising Pt-based ternary catalyst is crucial for polymer electrolyte membrane fuel cells (PEMFCs) due to improving catalytic activity and durability for both methanol oxidation reaction and oxygen reduction reaction. In this work, a facile strategy is used for the synthesis ternary RuMPt (M = Fe, Co, Ni, and Cu) nanodendrities catalysts. The ternary RuMPt alloys exhibit enhanced specific and mass activity, positive half-wave potential, and long-term stability, compared with binary Pt-based alloy and the commercial Pt/C catalyst, which is attributed to the high electron density and upshifting of the d-band center for Pt atoms, and synergistic catalytic effects among Pt, M, and Ru atoms by introducing a transition metal. Impressively, the ternary RuCoPt catalyst exhibits superior mass activity (801.59 mA mg-1) and positive half-wave potential (0.857 V vs. RHE) towards MOR and ORR, respectively. Thus, the RuMPt nanocomposite is a very promising material to be used as dual electrocatalyst in the application of PEMFCs.

  8. Development of a highly active electrocatalyst via ultrafine Pd nanoparticles dispersed on pristine graphene.

    PubMed

    Zhao, Jian; Liu, Zhensheng; Li, Hongqi; Hu, Wenbin; Zhao, Changzhi; Zhao, Peng; Shi, Donglu

    2015-03-01

    A unique synthesis was developed to immobilize Pd nanoparticles on pristine graphene (PG) sheets via a facile supercritical carbon dioxide route. Pristine graphene was obtained by sonication-assisted exfoliation of graphite in an organic solvent. Finely dispersed worm-like Pd nanoparticles are homogeneously deposited on the hydrophobic graphene surfaces. The combination of pristine graphene sheets and well-dispersed Pd nanoparticles provided large electrochemically active surface areas (ECSA) for both direct formic acid fuel cell (DFAFC) and methanol fuel cell (DMFC). The ECSA values are more than twice as large as those of reduced graphene oxide and carbon nanotube based counterparts or six times those of conventional XC-72 carbon black. Significant enhancements were also observed in the electrocatalytic activity and stability measurements. The excellent electrochemical property of Pd/PG is attributable to the well-preserved graphene structure that ensures electrical conductivity and stability of the composite. Its large surface area also allows for the deposition of small size and high dispersion of the Pd nanoparticles. This straightforward synthesis offers a new pathway for developing highly active electrocatalysts based on pristine graphene with fully optimized properties. PMID:25692321

  9. Oxygen reduction and evolution reactions of air electrodes using a perovskite oxide as an electrocatalyst

    NASA Astrophysics Data System (ADS)

    Nishio, Koji; Molla, Sergio; Okugaki, Tomohiko; Nakanishi, Shinji; Nitta, Iwao; Kotani, Yukinari

    2015-03-01

    The oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) of air electrodes consisting of La0.5Sr0.5CoO3 and/or carbon in the electrocatalyst layer are studied by using two types of gas diffusion electrodes. Cyclic voltammetry and square wave voltammetry studies reveal very low ORR activity of carbon-free perovskite and remarkably enhanced ORR of perovskite-carbon composites. The ORR current density at -0.5 V vs. Hg/HgO is higher than 200 mA cm-2 in a wide range of perovskite-carbon composition, suggesting good peroxide reducing capability of the perovskite. The ORR mechanisms of perovskite-carbon composites are consistent with the 2+2-electron mechanisms. The ORR and OER properties of perovskite-carbon composite electrodes are significantly influenced by the carbon species. The electrode exhibits a higher ORR current density, but inferior cycling performances when a carbon material with a higher specific surface area is used, and vice versa. Under a current density of 20 mA cm-2 and ORR and OER durations of 30 min, a gas diffusion type electrode consists of La0.5Sr0.5CoO3 and a low surface area carbon are capable of more than 150 cycles.

  10. Cobalt and nickel diimine-dioxime complexes as molecular electrocatalysts for hydrogen evolution with low overvoltages.

    PubMed

    Jacques, Pierre-André; Artero, Vincent; Pécaut, Jacques; Fontecave, Marc

    2009-12-01

    Hydrogen production through the reduction of water appears to be a convenient solution for the long-run storage of renewable energies. However, economically viable hydrogen production requests platinum-free catalysts, because this expensive and scarce (only 37 ppb in the Earth's crust) metal is not a sustainable resource [Gordon RB, Bertram M, Graedel TE (2006) Proc Natl Acad Sci USA 103:1209-1214]. Here, we report on a new family of cobalt and nickel diimine-dioxime complexes as efficient and stable electrocatalysts for hydrogen evolution from acidic nonaqueous solutions with slightly lower overvoltages and much larger stabilities towards hydrolysis as compared to previously reported cobaloxime catalysts. A mechanistic study allowed us to determine that hydrogen evolution likely proceeds through a bimetallic homolytic pathway. The presence of a proton-exchanging site in the ligand, furthermore, provides an exquisite mechanism for tuning the electrocatalytic potential for hydrogen evolution of these compounds in response to variations of the acidity of the solution, a feature only reported for native hydrogenase enzymes so far. PMID:19948953

  11. Cobalt and nickel diimine-dioxime complexes as molecular electrocatalysts for hydrogen evolution with low overvoltages

    PubMed Central

    Jacques, Pierre-André; Artero, Vincent; Pécaut, Jacques; Fontecave, Marc

    2009-01-01

    Hydrogen production through the reduction of water appears to be a convenient solution for the long-run storage of renewable energies. However, economically viable hydrogen production requests platinum-free catalysts, because this expensive and scarce (only 37 ppb in the Earth's crust) metal is not a sustainable resource [Gordon RB, Bertram M, Graedel TE (2006) Proc Natl Acad Sci USA 103:1209–1214]. Here, we report on a new family of cobalt and nickel diimine-dioxime complexes as efficient and stable electrocatalysts for hydrogen evolution from acidic nonaqueous solutions with slightly lower overvoltages and much larger stabilities towards hydrolysis as compared to previously reported cobaloxime catalysts. A mechanistic study allowed us to determine that hydrogen evolution likely proceeds through a bimetallic homolytic pathway. The presence of a proton-exchanging site in the ligand, furthermore, provides an exquisite mechanism for tuning the electrocatalytic potential for hydrogen evolution of these compounds in response to variations of the acidity of the solution, a feature only reported for native hydrogenase enzymes so far. PMID:19948953

  12. Hydrogel-derived non-precious electrocatalysts for efficient oxygen reduction.

    PubMed

    You, Bo; Yin, Peiqun; Zhang, Junli; He, Daping; Chen, Gaoli; Kang, Fei; Wang, Huiqiao; Deng, Zhaoxiang; Li, Yadong

    2015-01-01

    The development of highly active, cheap and robust oxygen reduction reaction (ORR) electrocatalysts to replace precious metal platinum is extremely urgent and challenging for renewable energy devices. Herein we report a novel, green and especially facile hydrogel strategy to construct N and B co-doped nanocarbon embedded with Co-based nanoparticles as an efficient non-precious ORR catalyst. The agarose hydrogel provides a general host matrix to achieve a homogeneous distribution of key precursory components including cobalt (II) acetate and buffer salts, which, upon freeze-drying and carbonization, produces the highly active ORR catalyst. The gel buffer containing Tris base, boric acid and ethylenediaminetetraacetic acid, commonly adopted for pH and ionic strength control, plays distinctively different roles here. These include a green precursor for N- and B-doping, a salt porogen and a Co(2+) chelating agent, all contributing to the excellent ORR activity. This hydrogel-based process is potentially generalizable for many other catalytic materials. PMID:26130371

  13. Pentlandite rocks as sustainable and stable efficient electrocatalysts for hydrogen generation

    PubMed Central

    Konkena, Bharathi; junge Puring, Kai; Sinev, Ilya; Piontek, Stefan; Khavryuchenko, Oleksiy; Dürholt, Johannes P.; Schmid, Rochus; Tüysüz, Harun; Muhler, Martin; Schuhmann, Wolfgang; Apfel, Ulf-Peter

    2016-01-01

    The need for sustainable catalysts for an efficient hydrogen evolution reaction is of significant interest for modern society. Inspired by comparable structural properties of [FeNi]-hydrogenase, here we present the natural ore pentlandite (Fe4.5Ni4.5S8) as a direct ‘rock' electrode material for hydrogen evolution under acidic conditions with an overpotential of 280 mV at 10 mA cm−2. Furthermore, it reaches a value as low as 190 mV after 96 h of electrolysis due to surface sulfur depletion, which may change the electronic structure of the catalytically active nickel–iron centres. The ‘rock' material shows an unexpected catalytic activity with comparable overpotential and Tafel slope to some well-developed metallic or nanostructured catalysts. Notably, the ‘rock' material offers high current densities (≤650 mA cm−2) without any loss in activity for approximately 170 h. The superior hydrogen evolution performance of pentlandites as ‘rock' electrode labels this ore as a promising electrocatalyst for future hydrogen-based economy. PMID:27461840

  14. Porous Nickel-Iron Selenide Nanosheets as Highly Efficient Electrocatalysts for Oxygen Evolution Reaction.

    PubMed

    Wang, Zhaoyang; Li, Jiantao; Tian, Xiaocong; Wang, Xuanpeng; Yu, Yang; Owusu, Kwadwo Asare; He, Liang; Mai, Liqiang

    2016-08-01

    Exploring non-noble and high-efficiency electrocatalysts is critical to large-scale industrial applications of electrochemical water splitting. Currently, nickel-based selenide materials are promising candidates for oxygen evolution reaction due to their low cost and excellent performance. In this work, we report the porous nickel-iron bimetallic selenide nanosheets ((Ni0.75Fe0.25)Se2) on carbon fiber cloth (CFC) by selenization of the ultrathin NiFe-based nanosheet precursor. The as-prepared three-dimensional oxygen evolution electrode exhibits a small overpotential of 255 mV at 35 mA cm(-2) and a low Tafel slope of 47.2 mV dec(-1) and keeps high stability during a 28 h measurement in alkaline solution. The outstanding catalytic performance and strong durability, in comparison to the advanced non-noble metal catalysts, are derived from the porous nanostructure fabrication, Fe incorporation, and selenization, which result in fast charge transportation and large electrochemically active surface area and enhance the release of oxygen bubbles from the electrode surface. PMID:27400679

  15. Highly porous non-precious bimetallic electrocatalysts for efficient hydrogen evolution

    DOE PAGESBeta

    Lu, Qi; Hutchings, Gregory S.; Yu, Weiting; Zhou, Yang; Forest, Robert V.; Tao, Runzhe; Rosen, Jonathan; Yonemoto, Bryan T.; Cao, Zeyuan; Zheng, Haimei; et al

    2015-03-16

    One of the key components of carbon dioxide-free hydrogen production is a robust and efficient non-precious metal catalyst for the hydrogen evolution reaction. We report that a hierarchical nanoporous copper-titanium bimetallic electrocatalyst is able to produce hydrogen from water under a mild overpotential at more than twice the rate of state-of-the- art carbon-supported platinum catalyst. Although both copper and titanium are known to be poor hydrogen evolution catalysts, the combination of these two elements creates unique copper-copper-titanium hollow sites, which have a hydrogen-binding energy very similar to that of platinum, resulting in an exceptional hydrogen evolution activity. Moreover, the hierarchicalmore » porosity of the nanoporous-copper titanium catalyst also contributes to its high hydrogen evolution activity, because it provides a large-surface area for electrocatalytic hydrogen evolution, and improves the mass transport properties. Moreover, the catalyst is self-supported, eliminating the overpotential associated with the catalyst/support interface.« less

  16. Highly active oxygen reduction non-platinum group metal electrocatalyst without direct metal–nitrogen coordination

    PubMed Central

    Strickland, Kara; Miner, Elise; Jia, Qingying; Tylus, Urszula; Ramaswamy, Nagappan; Liang, Wentao; Sougrati, Moulay-Tahar; Jaouen, Frédéric; Mukerjee, Sanjeev

    2015-01-01

    Replacement of noble metals in catalysts for cathodic oxygen reduction reaction with transition metals mostly create active sites based on a composite of nitrogen-coordinated transition metal in close concert with non-nitrogen-coordinated carbon-embedded metal atom clusters. Here we report a non-platinum group metal electrocatalyst with an active site devoid of any direct nitrogen coordination to iron that outperforms the benchmark platinum-based catalyst in alkaline media and is comparable to its best contemporaries in acidic media. In situ X-ray absorption spectroscopy in conjunction with ex situ microscopy clearly shows nitrided carbon fibres with embedded iron particles that are not directly involved in the oxygen reduction pathway. Instead, the reaction occurs primarily on the carbon–nitrogen structure in the outer skin of the nitrided carbon fibres. Implications include the potential of creating greater active site density and the potential elimination of any Fenton-type process involving exposed iron ions culminating in peroxide initiated free-radical formation. PMID:26059552

  17. Atomic Structure of Pt3Ni Nanoframe Electrocatalysts by in Situ X-ray Absorption Spectroscopy.

    PubMed

    Becknell, Nigel; Kang, Yijin; Chen, Chen; Resasco, Joaquin; Kornienko, Nikolay; Guo, Jinghua; Markovic, Nenad M; Somorjai, Gabor A; Stamenkovic, Vojislav R; Yang, Peidong

    2015-12-23

    Understanding the atomic structure of a catalyst is crucial to exposing the source of its performance characteristics. It is highly unlikely that a catalyst remains the same under reaction conditions when compared to as-synthesized. Hence, the ideal experiment to study the catalyst structure should be performed in situ. Here, we use X-ray absorption spectroscopy (XAS) as an in situ technique to study Pt3Ni nanoframe particles which have been proven to be an excellent electrocatalyst for the oxygen reduction reaction (ORR). The surface characteristics of the nanoframes were probed through electrochemical hydrogen underpotential deposition and carbon monoxide electrooxidation, which showed that nanoframe surfaces with different structure exhibit varying levels of binding strength to adsorbate molecules. It is well-known that Pt-skin formation on Pt-Ni catalysts will enhance ORR activity by weakening the binding energy between the surface and adsorbates. Ex situ and in situ XAS results reveal that nanoframes which bind adsorbates more strongly have a rougher Pt surface caused by insufficient segregation of Pt to the surface and consequent Ni dissolution. In contrast, nanoframes which exhibit extremely high ORR activity simultaneously demonstrate more significant segregation of Pt over Ni-rich subsurface layers, allowing better formation of the critical Pt-skin. This work demonstrates that the high ORR activity of the Pt3Ni hollow nanoframes depends on successful formation of the Pt-skin surface structure. PMID:26652294

  18. Electrospun carbon nanofibers/electrocatalyst hybrids as asymmetric electrodes for vanadium redox flow battery

    NASA Astrophysics Data System (ADS)

    Wei, Guanjie; Fan, Xinzhuang; Liu, Jianguo; Yan, Chuanwei

    2015-05-01

    To improve the electrochemical activity of polyacrylonitrile (PAN)-based electrospun carbon nanofibers (ECNFs) toward vanadium redox couples, the multi-wall carbon nanotubes (CNTs) and Bi-based compound as electrocatalyst have been embedded in the ECNFs to make composite electrode, respectively. The morphology and electrochemical properties of pristine ECNFs, CNTs/ECNFs and Bi/ECNFs have been characterized. Among the three kinds of electrodes, the CNTs/ECNFs show best electrochemical activity toward VO2+/VO2+ redox couple, while the Bi/ECNFs present the best electrochemical activity toward V2+/V3+ redox couple. Furthermore, the high overpotential of hydrogen evolution on Bi/ECNFs makes the side-reaction suppressed. Because of the large property difference between the two composite electrodes, the CNTs/ECNFs and Bi/ECNFs are designed to act as positive and negative electrode for vanadium redox flow battery (VRFB), respectively. It not only does improve the kinetics of two electrode reactions at the same time, but also reduce the kinetics difference between them. Due to the application of asymmetric electrodes, performance of the cell is improved greatly.

  19. Pentlandite rocks as sustainable and stable efficient electrocatalysts for hydrogen generation

    NASA Astrophysics Data System (ADS)

    Konkena, Bharathi; Junge Puring, Kai; Sinev, Ilya; Piontek, Stefan; Khavryuchenko, Oleksiy; Dürholt, Johannes P.; Schmid, Rochus; Tüysüz, Harun; Muhler, Martin; Schuhmann, Wolfgang; Apfel, Ulf-Peter

    2016-07-01

    The need for sustainable catalysts for an efficient hydrogen evolution reaction is of significant interest for modern society. Inspired by comparable structural properties of [FeNi]-hydrogenase, here we present the natural ore pentlandite (Fe4.5Ni4.5S8) as a direct `rock' electrode material for hydrogen evolution under acidic conditions with an overpotential of 280 mV at 10 mA cm-2. Furthermore, it reaches a value as low as 190 mV after 96 h of electrolysis due to surface sulfur depletion, which may change the electronic structure of the catalytically active nickel-iron centres. The `rock' material shows an unexpected catalytic activity with comparable overpotential and Tafel slope to some well-developed metallic or nanostructured catalysts. Notably, the `rock' material offers high current densities (<=650 mA cm-2) without any loss in activity for approximately 170 h. The superior hydrogen evolution performance of pentlandites as `rock' electrode labels this ore as a promising electrocatalyst for future hydrogen-based economy.

  20. Plasma nitriding induced growth of Pt-nanowire arrays as high performance electrocatalysts for fuel cells

    NASA Astrophysics Data System (ADS)

    Du, Shangfeng; Lin, Kaijie; Malladi, Sairam K.; Lu, Yaxiang; Sun, Shuhui; Xu, Qiang; Steinberger-Wilckens, Robert; Dong, Hanshan

    2014-09-01

    In this work, we demonstrate an innovative approach, combing a novel active screen plasma (ASP) technique with green chemical synthesis, for a direct fabrication of uniform Pt nanowire arrays on large-area supports. The ASP treatment enables in-situ N-doping and surface modification to the support surface, significantly promoting the uniform growth of tiny Pt nuclei which directs the growth of ultrathin single-crystal Pt nanowire (2.5-3 nm in diameter) arrays, forming a three-dimensional (3D) nano-architecture. Pt nanowire arrays in-situ grown on the large-area gas diffusion layer (GDL) (5 cm2) can be directly used as the catalyst electrode in fuel cells. The unique design brings in an extremely thin electrocatalyst layer, facilitating the charge transfer and mass transfer properties, leading to over two times higher power density than the conventional Pt nanoparticle catalyst electrode in real fuel cell environment. Due to the similar challenges faced with other nanostructures and the high availability of ASP for other material surfaces, this work will provide valuable insights and guidance towards the development of other new nano-architectures for various practical applications.

  1. Highly porous non-precious bimetallic electrocatalysts for efficient hydrogen evolution.

    PubMed

    Lu, Qi; Hutchings, Gregory S; Yu, Weiting; Zhou, Yang; Forest, Robert V; Tao, Runzhe; Rosen, Jonathan; Yonemoto, Bryan T; Cao, Zeyuan; Zheng, Haimei; Xiao, John Q; Jiao, Feng; Chen, Jingguang G

    2015-01-01

    A robust and efficient non-precious metal catalyst for hydrogen evolution reaction is one of the key components for carbon dioxide-free hydrogen production. Here we report that a hierarchical nanoporous copper-titanium bimetallic electrocatalyst is able to produce hydrogen from water under a mild overpotential at more than twice the rate of state-of-the-art carbon-supported platinum catalyst. Although both copper and titanium are known to be poor hydrogen evolution catalysts, the combination of these two elements creates unique copper-copper-titanium hollow sites, which have a hydrogen-binding energy very similar to that of platinum, resulting in an exceptional hydrogen evolution activity. In addition, the hierarchical porosity of the nanoporous copper-titanium catalyst also contributes to its high hydrogen evolution activity, because it provides a large-surface area for electrocatalytic hydrogen evolution, and improves the mass transport properties. Moreover, the catalyst is self-supported, eliminating the overpotential associated with the catalyst/support interface. PMID:25910892

  2. A novel electroless method to prepare a platinum electrocatalyst on diamond for fuel cell applications

    NASA Astrophysics Data System (ADS)

    Lyu, Xiao; Hu, Jingping; Foord, John S.; Wang, Qiang

    2013-11-01

    A novel electroless deposition method was demonstrated to prepare a platinum electrocatalyst on boron doped diamond (BDD) substrates without the need for pre-activation. This green method addresses the uniformity and particle size issues associated with electrodeposition and circumvents the pre-activation procedure which is necessary for conventional electroless deposition. The inert BDD substrate formed a galvanic couple with an iron wire, to overcome the activation barrier associated with conventional electroless deposition on diamond, leading to the formation of Pt nanoparticles on the electrode surface in a galvanic process coupled to a chemical process. When sodium hypophosphite was employed as the reducing agent to drive the electroless reaction Pt deposits which were contaminated with iron and phosphorus resulted. In contrast, the reducing agent ascorbic acid gave rise to high purity Pt nanoparticles. Optimal deposition conditions with respect to bath temperature, pH value and stabilizing additives are identified. Using this approach, high purity and uniformly distributed platinum nanoparticles are obtained on the diamond electrode surface, which demonstrate a high electrochemical activity towards methanol oxidation.

  3. Plasma nitriding induced growth of Pt-nanowire arrays as high performance electrocatalysts for fuel cells

    PubMed Central

    Du, Shangfeng; Lin, Kaijie; Malladi, Sairam K.; Lu, Yaxiang; Sun, Shuhui; Xu, Qiang; Steinberger-Wilckens, Robert; Dong, Hanshan

    2014-01-01

    In this work, we demonstrate an innovative approach, combing a novel active screen plasma (ASP) technique with green chemical synthesis, for a direct fabrication of uniform Pt nanowire arrays on large-area supports. The ASP treatment enables in-situ N-doping and surface modification to the support surface, significantly promoting the uniform growth of tiny Pt nuclei which directs the growth of ultrathin single-crystal Pt nanowire (2.5–3 nm in diameter) arrays, forming a three-dimensional (3D) nano-architecture. Pt nanowire arrays in-situ grown on the large-area gas diffusion layer (GDL) (5 cm2) can be directly used as the catalyst electrode in fuel cells. The unique design brings in an extremely thin electrocatalyst layer, facilitating the charge transfer and mass transfer properties, leading to over two times higher power density than the conventional Pt nanoparticle catalyst electrode in real fuel cell environment. Due to the similar challenges faced with other nanostructures and the high availability of ASP for other material surfaces, this work will provide valuable insights and guidance towards the development of other new nano-architectures for various practical applications. PMID:25241800

  4. Ordered PdCu-Based Nanoparticles as Bifunctional Oxygen-Reduction and Ethanol-Oxidation Electrocatalysts.

    PubMed

    Jiang, Kezhu; Wang, Pengtang; Guo, Shaojun; Zhang, Xu; Shen, Xuan; Lu, Gang; Su, Dong; Huang, Xiaoqing

    2016-07-25

    The development of superior non-platinum electrocatalysts for enhancing the electrocatalytic activity and stability for the oxygen-reduction reaction (ORR) and liquid fuel oxidation reaction is very important for the commercialization of fuel cells, but still a great challenge. Herein, we demonstrate a new colloidal chemistry technique for making structurally ordered PdCu-based nanoparticles (NPs) with composition control from PdCu to PdCuNi and PtCuCo. Under the dual tuning on the composition and intermetallic phase, the ordered PdCuCo NPs exhibit better activity and much enhanced stability for ORR and ethanol-oxidation reaction (EOR) than those of disordered PdCuM NPs, the commercial Pt/C and Pd/C catalysts. The density functional theory (DFT) calculations reveal that the improved ORR activity on the PdCuM NPs stems from the catalytically active hollow sites arising from the ligand effect and the compressive strain on the Pd surface owing to the smaller atomic size of Cu, Co, and Ni. PMID:27253520

  5. Carbothermal synthesis of titanium oxycarbide as electrocatalyst support with high oxygen evolution reaction activity

    SciTech Connect

    Huang, K; Li, YF; Xing, YC

    2012-11-09

    Carbothermal reduction of semiconducting TiO2 into highly conductive titanium oxycarbide (TiOxCy) was investigated. The thermally produced uniform carbon layer on TiO2 (Degussa P25) protects the TiO2 nanoparticles from sintering and, at the same time, supplies the carbon source for doping TiO2 with carbon. At low temperatures (e. g., 700 degrees C), carbon only substitutes part of the oxide and distorts the TiO2 lattice to form TiO2-xCx with only substitutional carbon. When the carbon-doped TiO2 is annealed at a higher temperature (1100 degrees C), x-ray diffraction and x-ray photoelectron spectroscopy results showed that TiOxCy, a solid solution of TiO and TiC, was formed, which displays different diffraction peaks and binding energies. It was shown that TiOxCy has much better oxygen revolution reaction activity than TiO2 or TiO2-xCx. Further studies showed that the TiOxCy obtained can be used as a support for metal electrocatalyst, leading to a bifunctional catalyst effective for both oxygen reduction and evolution reactions.

  6. Ruthenium-based electrocatalysts supported on reduced graphene oxide for lithium-air batteries.

    PubMed

    Jung, Hun-Gi; Jeong, Yo Sub; Park, Jin-Bum; Sun, Yang-Kook; Scrosati, Bruno; Lee, Yun Jung

    2013-04-23

    Ruthenium-based nanomaterials supported on reduced graphene oxide (rGO) have been investigated as air cathodes in non-aqueous electrolyte Li-air cells using a TEGDME-LiCF3SO3 electrolyte. Homogeneously distributed metallic ruthenium and hydrated ruthenium oxide (RuO2·0.64H2O), deposited exclusively on rGO, have been synthesized with average size below 2.5 nm. The synthesized hybrid materials of Ru-based nanoparticles supported on rGO efficiently functioned as electrocatalysts for Li2O2 oxidation reactions, maintaining cycling stability for 30 cycles without sign of TEGDME-LiCF3SO3 electrolyte decomposition. Specifically, RuO2·0.64H2O-rGO hybrids were superior to Ru-rGO hybrids in catalyzing the OER reaction, significantly reducing the average charge potential to ∼3.7 V at the high current density of 500 mA g(-1) and high specific capacity of 5000 mAh g(-1). PMID:23540570

  7. Coupled molybdenum carbide and reduced graphene oxide electrocatalysts for efficient hydrogen evolution

    NASA Astrophysics Data System (ADS)

    Li, Ji-Sen; Wang, Yu; Liu, Chun-Hui; Li, Shun-Li; Wang, Yu-Guang; Dong, Long-Zhang; Dai, Zhi-Hui; Li, Ya-Fei; Lan, Ya-Qian

    2016-04-01

    Electrochemical water splitting is one of the most economical and sustainable methods for large-scale hydrogen production. However, the development of low-cost and earth-abundant non-noble-metal catalysts for the hydrogen evolution reaction remains a challenge. Here we report a two-dimensional coupled hybrid of molybdenum carbide and reduced graphene oxide with a ternary polyoxometalate-polypyrrole/reduced graphene oxide nanocomposite as a precursor. The hybrid exhibits outstanding electrocatalytic activity for the hydrogen evolution reaction and excellent stability in acidic media, which is, to the best of our knowledge, the best among these reported non-noble-metal catalysts. Theoretical calculations on the basis of density functional theory reveal that the active sites for hydrogen evolution stem from the pyridinic nitrogens, as well as the carbon atoms, in the graphene. In a proof-of-concept trial, an electrocatalyst for hydrogen evolution is fabricated, which may open new avenues for the design of nanomaterials utilizing POMs/conducting polymer/reduced-graphene oxide nanocomposites.

  8. A DFT-based genetic algorithm search for AuCu nanoalloy electrocatalysts for CO₂ reduction.

    PubMed

    Lysgaard, Steen; Mýrdal, Jón S G; Hansen, Heine A; Vegge, Tejs

    2015-11-14

    Using a DFT-based genetic algorithm (GA) approach, we have determined the most stable structure and stoichiometry of a 309-atom icosahedral AuCu nanoalloy, for potential use as an electrocatalyst for CO2 reduction. The identified core-shell nano-particle consists of a copper core interspersed with gold atoms having only copper neighbors and a gold surface with a few copper atoms in the terraces. We also present an adsorbate-dependent correction scheme, which enables an accurate determination of adsorption energies using a computationally fast, localized LCAO-basis set. These show that it is possible to use the LCAO mode to obtain a realistic estimate of the molecular chemisorption energy for systems where the computation in normal grid mode is not computationally feasible. These corrections are employed when calculating adsorption energies on the Cu, Au and most stable mixed particles. This shows that the mixed Cu135@Au174 core-shell nanoalloy has a similar adsorption energy, for the most favorable site, as a pure gold nano-particle. Cu, however, has the effect of stabilizing the icosahedral structure because Au particles are easily distorted when adding adsorbates. PMID:25924775

  9. Aligned Carbon Nanotube Array Functionalization for Enhanced Atomic Layer Deposition of Platinum Electrocatalysts

    SciTech Connect

    Dameron, A. A.; Pylypenko, S.; Bult, J. B.; Neyerlin, K. C.; Engtrakul, C.; Bochert, C.; Leong, G. J.; Frisco, S. L.; Simpson, L.; Dinh, H. N.; Pivovar, B.

    2012-04-15

    Uniform metal deposition onto high surface area supports is a key challenge of developing successful efficient catalyst materials. Atomic layer deposition (ALD) circumvents permeation difficulties, but relies on gas-surface reactions to initiate growth. Our work demonstrates that modified surfaces within vertically aligned carbon nanotube (CNT) arrays, from plasma and molecular precursor treatments, can lead to improved catalyst deposition. Gas phase functionalization influences the number of ALD nucleation sites and the onset of ALD growth and, in turn, affects the uniformity of the coating along the length of the CNTs within the aligned arrays. The induced chemical changes for each functionalization route are identified by X-ray photoelectron and Raman spectroscopies. The most effective functionalization routes increase the prevalence of oxygen moieties at defect sites on the carbon surfaces. The striking effects of the functionalization are demonstrated with ALD Pt growth as a function of surface treatment and ALD cycles examined by electron microscopy of the arrays and the individual CNTs. Finally, we demonstrate applicability of these materials as fuel cell electrocatalysts and show that surface functionalization affects their performance towards oxygen reduction reaction.

  10. Cerium(III) Complex Modified Gold Electrode: An Efficient Electrocatalyst for the Oxygen Evolution Reaction.

    PubMed

    Garain, Samiran; Barman, Koushik; Sinha, Tridib Kumar; Jasimuddin, Sk; Haeberle, Jörg; Henkel, Karsten; Schmeisser, Dieter; Mandal, Dipankar

    2016-08-24

    Exploring efficient and inexpensive electrocatalysts for the oxidation of water is of great importance for various electrochemical energy storage and conversion technologies. In the present study, a new water-soluble [Ce(III)(DMF) (HSO4)3] complex was synthesized and characterized by UV-vis, photoluminescence, and high-resolution X-ray photoelectron spectroscopy techniques. Owing to classic 5d → 4f transitions, an intense photoluminescence in the UV region was observed from the water-soluble [Ce(III)(DMF) (HSO4)3] complex. A stacking electrode was designed where self-assembled l-cysteine monolayer modified gold was immobilized with the synthesized cerium complex and was characterized by scanning electron microscopy, electrochemical impedance spectroscopy, and cyclic voltammetry. The resulting electrode, i.e., [Ce(III)(DMF) (HSO4)3]-l-cysteine-Au stacks shows high electrocatalytic water oxidation behavior at an overpotential of η ≈ 0.34 V under neutral pH conditions. We also demonstrated a way where the overpotential is possible to decrease upon irradiation of UV light. PMID:27490440

  11. A Molecular Surface Functionalization Approach to Tuning Nanoparticle Electrocatalysts for Carbon Dioxide Reduction.

    PubMed

    Cao, Zhi; Kim, Dohyung; Hong, Dachao; Yu, Yi; Xu, Jun; Lin, Song; Wen, Xiaodong; Nichols, Eva M; Jeong, Keunhong; Reimer, Jeffrey A; Yang, Peidong; Chang, Christopher J

    2016-07-01

    Conversion of the greenhouse gas carbon dioxide (CO2) to value-added products is an important challenge for sustainable energy research, and nanomaterials offer a broad class of heterogeneous catalysts for such transformations. Here we report a molecular surface functionalization approach to tuning gold nanoparticle (Au NP) electrocatalysts for reduction of CO2 to CO. The N-heterocyclic (NHC) carbene-functionalized Au NP catalyst exhibits improved faradaic efficiency (FE = 83%) for reduction of CO2 to CO in water at neutral pH at an overpotential of 0.46 V with a 7.6-fold increase in current density compared to that of the parent Au NP (FE = 53%). Tafel plots of the NHC carbene-functionalized Au NP (72 mV/decade) vs parent Au NP (138 mV/decade) systems further show that the molecular ligand influences mechanistic pathways for CO2 reduction. The results establish molecular surface functionalization as a complementary approach to size, shape, composition, and defect control for nanoparticle catalyst design. PMID:27322487

  12. An iron complex with pendant amines as a molecular electrocatalyst for oxidation of hydrogen

    SciTech Connect

    Liu, Tianbiao L.; DuBois, Daniel L.; Bullock, R. Morris

    2013-02-17

    Addressing the worldwide problems of escalating energy demand and increasing emissions of CO2 requires an increase in utilization of carbon-neutral, sustainable energy sources. Electrocatalysts are needed for conversion between chemical energy (bonds such as the H-H bond of hydrogen) and electricity in future systems for storage and use of energy. Hydrogen is an attractive energy carrier, but a major barrier to more widespread use of hydrogen is the need for efficient, inexpensive catalysts. Electricity is produced from oxidation of hydrogen in low-temperature fuel cells, but the best catalyst is platinum, a precious metal of low abundance.1 Here we show that a synthetic iron complex is a catalyst for the oxidation of hydrogen. A burgeoning effort by chemists studying many areas of catalysis has focused on "Cheap Metals for Noble Tasks."2 Iron is particularly attractive because of its very high earth-abundance along with its low cost and toxicity, leading Bolm to suggest the advent of a "new iron age."3 Our results demonstrate that rationally designed catalysts based on abundant, inexpensive metals offer substantial promise as alternatives to precious metal catalysts. We thank the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences and Biosciences, for support of this research. Pacific Northwest National Laboratory is operated by Battelle for the U.S. Department of Energy.

  13. Carbon Nitrogen Nanotubes as Efficient Bifunctional Electrocatalysts for Oxygen Reduction and Evolution Reactions.

    PubMed

    Yadav, Ram Manohar; Wu, Jingjie; Kochandra, Raji; Ma, Lulu; Tiwary, Chandra Sekhar; Ge, Liehui; Ye, Gonglan; Vajtai, Robert; Lou, Jun; Ajayan, Pulickel M

    2015-06-10

    Oxygen reduction and evolution reactions are essential for broad range of renewable energy technologies such as fuel cells, metal-air batteries and hydrogen production through water splitting, therefore, tremendous effort has been taken to develop excellent catalysts for these reactions. However, the development of cost-effective and efficient bifunctional catalysts for both reactions still remained a grand challenge. Herein, we report the electrocatalytic investigations of bamboo-shaped carbon nitrogen nanotubes (CNNTs) having different diameter distribution synthesized by liquid chemical vapor deposition technique using different nitrogen containing precursors. These CNNTs are found to be efficient bifunctional electrocatalyst for oxygen reduction and evolution reactions. The electrocatalytic activity strongly depends on the nanotube diameter as well as nitrogen functionality type. The higher diameter CNNTs are more favorable for these reactions. The increase in nanotube diameter itself enhances the catalytic activity by lowering the oxygen adsorption energy, better conductivity, and further facilitates the reaction by increasing the percentage of catalytically active nitrogen moieties in CNNTs. PMID:25970133

  14. Rational Design of Efficient Electrocatalysts for Hydrogen Evolution Reaction: Single Layers of WS2 Nanoplates Anchored to Hollow Nitrogen-Doped Carbon Nanofibers.

    PubMed

    Yu, Sunmoon; Kim, Jaehoon; Yoon, Ki Ro; Jung, Ji-Won; Oh, Jihun; Kim, Il-Doo

    2015-12-30

    To exploit the benefits of nanostructuring for enhanced hydrogen evolution reaction (HER), we employed coaxial electrospinning to synthesize single-layered WS2 nanoplates anchored to hollow nitrogen-doped carbon nanofibers (WS2@HNCNFs) as efficient electrocatalysts. For comparison, bulk WS2 powder and single layers of WS2 embedded in nitrogen-doped carbon nanofibers (WS2@NCNFs) were synthesized and electrochemically tested. The distinctive design of the WS2@HNCNFs enables remarkable electrochemical performances showing a low overpotential with reduced charge transfer resistance, a small Tafel slope, and excellent durability. The experimental results highlight the importance of nanostructure engineering in electrocatalysts for enhanced HER. PMID:26654256

  15. Synthesis of metal-metal oxide catalysts and electrocatalysts using a metal cation adsorption/reduction and adatom replacement by more noble ones

    DOEpatents

    Adzic, Radoslav; Vukmirovic, Miomir; Sasaki, Kotaro

    2010-04-27

    The invention relates to platinum-metal oxide composite particles and their use as electrocatalysts in oxygen-reducing cathodes and fuel cells. The invention particularly relates to methods for preventing the oxidation of the platinum electrocatalyst in the cathodes of fuel cells by use of these platinum-metal oxide composite particles. The invention additionally relates to methods for producing electrical energy by supplying such a fuel cell with an oxidant, such as oxygen, and a fuel source, such as hydrogen. The invention also relates to methods of making the metal-metal oxide composites.

  16. Investigation of PdIr/C electrocatalysts as anode on the performance of direct ammonia fuel cell

    NASA Astrophysics Data System (ADS)

    Assumpção, M. H. M. T.; da Silva, S. G.; De Souza, R. F. B.; Buzzo, G. S.; Spinacé, E. V.; Santos, M. C.; Neto, A. O.; Silva, J. C. M.

    2014-12-01

    This work investigates the ammonia electro-oxidation considering electrochemical and direct ammonia fuel cell (DAFC) experiments. The working electrodes/anodes are composed of Pd/C, PdIr/C (90:10, 70:30, 50:50, 30:70 and 10:90 atomic ratios) and Ir/C. Solutions of 1 mol L-1 NH4OH and 1 mol L-1 KOH were used for electrochemical experiments while 1.0, 3.0 and 5.0 mol L-1 NH4OH in 1.0 mol L-1 KOH were used in DAFC. X-ray diffraction analysis of PdIr/C electrocatalysts suggests the formation of PdIr alloy, while transmission electron micrographs show the average particle diameters between 4.6 and 6.2 nm. Electrochemical experiments indicate PdIr/C 30:70 as the best electrocatalyst in accordance with DAFC. The maximum power densities obtained with PdIr/C 30:70 as anode using 5 mol L-1 NH4OH and 1 mol L-1 KOH at 40 °C are 60% and 30% higher than the ones obtained with Pd/C and Ir/C electrocatalysts, respectively. The enhanced synergic effect in this specific composition may be assigned to an optimal ratio of palladium sites that dehydrogenates ammonia at lower overpotential with the lower surface coverage of Nads on iridium. Furthermore, electronic effect between palladium and iridium might also contribute to the decrease of poisoning on catalyst surface by Nads.

  17. Manganese oxide-induced strategy to high-performance iron/nitrogen/carbon electrocatalysts with highly exposed active sites

    NASA Astrophysics Data System (ADS)

    Sun, Tao; Wu, Qiang; Zhuo, Ou; Jiang, Yufei; Bu, Yongfeng; Yang, Lijun; Wang, Xizhang; Hu, Zheng

    2016-04-01

    Iron/nitrogen/carbon (Fe/N/C) catalyst is so far the most promising non-precious metal electrocatalyst for oxygen reduction reaction (ORR) in acidic medium, whose performance depends closely on the synthesis chemistry. Herein, we report a MnOx-induced strategy to construct the Fe/N/C with highly exposed Fe-Nx active sites, which involves the uniform spreading of polyaniline on hierarchical N-doped carbon nanocages by a reactive-template polymerization, followed by the successive iron incorporation and polyaniline pyrolysis. The resulting Fe/N/C demonstrates an excellent ORR performance, including an onset potential of 0.92 V (vs. RHE), four electron selectivity, superb stability and immunity to methanol crossover. The excellent performance is well correlated with the greatly enhanced surface active sites of the catalyst stemming from the unique MnOx-induced strategy. This study provides an efficient approach for exploring the advanced ORR electrocatalysts by increasing the exposed active sites.Iron/nitrogen/carbon (Fe/N/C) catalyst is so far the most promising non-precious metal electrocatalyst for oxygen reduction reaction (ORR) in acidic medium, whose performance depends closely on the synthesis chemistry. Herein, we report a MnOx-induced strategy to construct the Fe/N/C with highly exposed Fe-Nx active sites, which involves the uniform spreading of polyaniline on hierarchical N-doped carbon nanocages by a reactive-template polymerization, followed by the successive iron incorporation and polyaniline pyrolysis. The resulting Fe/N/C demonstrates an excellent ORR performance, including an onset potential of 0.92 V (vs. RHE), four electron selectivity, superb stability and immunity to methanol crossover. The excellent performance is well correlated with the greatly enhanced surface active sites of the catalyst stemming from the unique MnOx-induced strategy. This study provides an efficient approach for exploring the advanced ORR electrocatalysts by increasing the

  18. Distant protonated pyridine groups in water-soluble iron porphyrin electrocatalysts promote selective oxygen reduction to water

    SciTech Connect

    Matson, Benjamin D.; Carver, Colin T.; Von Ruden, Amber L.; Yang, Jenny Y.; Raugei, Simone; Mayer, James M.

    2012-11-08

    Fe(III)-meso-tetra(pyridyl)porphines are selective electrocatalysts for the reduction of dioxygen to water in aqueous acidic solution. The 2-pyridyl derivatives, both the triflate and chloride salts, are more selective than the isomeric 4-pyridyl complexes. The improved selectivity of is ascribed to the inward-pointing pyridinium groups acting as intramolecular proton relays. This research was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the US Department of Energy, Office of Science. Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy.

  19. Highly Selective and Stable Reduction of CO2 to CO by a Graphitic Carbon Nitride/Carbon Nanotube Composite Electrocatalyst.

    PubMed

    Lu, Xunyu; Tan, Tze Hao; Ng, Yun Hau; Amal, Rose

    2016-08-16

    A stable and selective electrocatalyst for CO2 reduction was fabricated by covalently attaching graphitic carbon nitride onto multiwall carbon nanotubes (g-C3 N4 /MWCNTs). The as-prepared composite is able to reduce CO2 exclusively to CO with a maximum Faraday efficiency of 60 %, and no decay in the catalytic activity was observed even after 50 h of reaction. The enhanced catalytic activity towards CO2 reduction is attributed to the formation of active carbon-nitrogen bonds, high specific surface area, and improved material conductivity of the g-C3 N4 /MWCNT composite. PMID:27312815

  20. Pt and Pt-Ru/Carbon Nanotube Nanocomposites Synthesized in Supercritical Fluid as Electrocatalysts for Low-Temperature Fuel Cells

    SciTech Connect

    Lin, Yuehe; Cui, Xiaoli; Wang, Jun; Yen, Clive; Wai, Chien M.

    2006-06-01

    In recent years, the use of supercritical fluids (SCFs) for the synthesis and processing of nanomaterials has proven to be a rapid, direct, and clean approach to develop nanomaterials and nanocomposites. The application of supercritical fluid technology can result in products (and processes) that are cleaner, less expensive, and of higher quality than those that are produced using conventional technologies and solvents. In this work, carbon nanotube (CNT)-supported Pt and Pt-Ru nanoparticles catalysts have been synthesized in supercritical carbon dioxide (scCO2). The experimental results demonstrate that Pt, Pt-Ru/CNT nanocomposites synthesized in supercritical carbon dioxide are effective electrocatalysts for low-temperature fuel cells.

  1. Electrodeposition of nickel-phosphorus nanoparticles film as a Janus electrocatalyst for electro-splitting of water

    NASA Astrophysics Data System (ADS)

    Liu, Qian; Gu, Shuang; Li, Chang Ming

    2015-12-01

    Nickel-phosphorus nanoparticles film on copper foam (Ni-P/CF) was prepared by electrodeposition. This electrocatalyst shows high catalytic activity and durability toward both hydrogen and oxygen evolution reactions in basic electrolytes. The results show that Ni-P/CF can deliver a current density of 10 mA cm-2 at an overpotential of 98 mV for hydrogen production and 325 mV for oxygen generating. A two-electrode water electrolyzer using Ni-P/CF as cathode and anode produces 10 mA cm-2 at a cell voltage of 1.68 V with high stability.

  2. Cobalt nanoparticles embedded in N-doped carbon as an efficient bifunctional electrocatalyst for oxygen reduction and evolution reactions

    NASA Astrophysics Data System (ADS)

    Su, Yunhe; Zhu, Yihua; Jiang, Hongliang; Shen, Jianhua; Yang, Xiaoling; Zou, Wenjian; Chen, Jianding; Li, Chunzhong

    2014-11-01

    Cobalt based catalysts are promising bifunctional electrocatalysts for both oxygen reduction and oxygen evolution reactions (ORR and OER) in unitized regenerative fuel cells (URFCs) operating with alkaline electrolytes. Here we report a hybrid composite of cobalt nanoparticles embedded in nitrogen-doped carbon (Co/N-C) via a solvothermal carbonization strategy. With the synergistic effect arising from the N-doped carbon and cobalt nanoparticles in the composite, the Co/N-C hybrid catalyst exhibits highly efficient bifunctional catalytic activity and excellent stability toward both ORR and OER. The ΔE (oxygen electrode activity parameter for judging the overall electrocatalytic activity of a bifunctional electrocatalyst) value for Co/N-C is 0.859 V, which is smaller than those of Pt/C and most of the non-precious metal catalysts in previous studies. Furthermore, the Co/N-C composite also shows better bifunctional catalytic activity than its oxidative counterparts, which could be attributed to the high specific surface area and the efficient charge transfer ability of the composite, as well as the good synergistic effect between N-doped carbon and the Co nanoparticles in the Co/N-C composite.Cobalt based catalysts are promising bifunctional electrocatalysts for both oxygen reduction and oxygen evolution reactions (ORR and OER) in unitized regenerative fuel cells (URFCs) operating with alkaline electrolytes. Here we report a hybrid composite of cobalt nanoparticles embedded in nitrogen-doped carbon (Co/N-C) via a solvothermal carbonization strategy. With the synergistic effect arising from the N-doped carbon and cobalt nanoparticles in the composite, the Co/N-C hybrid catalyst exhibits highly efficient bifunctional catalytic activity and excellent stability toward both ORR and OER. The ΔE (oxygen electrode activity parameter for judging the overall electrocatalytic activity of a bifunctional electrocatalyst) value for Co/N-C is 0.859 V, which is smaller than those

  3. MoO2-CoO coupled with a macroporous carbon hybrid electrocatalyst for highly efficient oxygen evolution

    NASA Astrophysics Data System (ADS)

    Li, B. B.; Liang, Y. Q.; Yang, X. J.; Cui, Z. D.; Qiao, S. Z.; Zhu, S. L.; Li, Z. Y.; Yin, K.

    2015-10-01

    Cost-effective electrocatalysts for oxygen evolution reactions are attractive for energy conversion and storage processes. A high-performance oxygen evolution reaction (OER) electrocatalyst composed of 3D ordered microporous carbon and a MoO2 skeleton modified by cobalt oxide nanoparticles (MoO2-CoO-Carbon) is produced through a template method. This unique 3DOM structure finely combines the larger surface area of the 3D carbon skeleton and MoO2 as well as stablizes anchoring sites for CoO nanocrystals on the skeleton. The synergistic effect between the catalytic activity between MoO2 and CoO as well as the enhanced electron transport arising from the carbon skeleton contributed to superior electrocatalytic OER properties of MoO2-CoO-Carbon. The M200-C-Carbon hybrid with an overpotential as low as 0.24 V is among the best reported Mo-based OER catalysts. Moreover, the turnover frequency at an overpotential of 0.35 V is 6 times as high as that of commercial RuO2.Cost-effective electrocatalysts for oxygen evolution reactions are attractive for energy conversion and storage processes. A high-performance oxygen evolution reaction (OER) electrocatalyst composed of 3D ordered microporous carbon and a MoO2 skeleton modified by cobalt oxide nanoparticles (MoO2-CoO-Carbon) is produced through a template method. This unique 3DOM structure finely combines the larger surface area of the 3D carbon skeleton and MoO2 as well as stablizes anchoring sites for CoO nanocrystals on the skeleton. The synergistic effect between the catalytic activity between MoO2 and CoO as well as the enhanced electron transport arising from the carbon skeleton contributed to superior electrocatalytic OER properties of MoO2-CoO-Carbon. The M200-C-Carbon hybrid with an overpotential as low as 0.24 V is among the best reported Mo-based OER catalysts. Moreover, the turnover frequency at an overpotential of 0.35 V is 6 times as high as that of commercial RuO2. Electronic supplementary information (ESI

  4. Nitrogen-doped and simultaneously reduced graphene oxide with superior dispersion as electrocatalysts for oxygen reduction reaction

    SciTech Connect

    Lee, Cheol-Ho; Yun, Jin-Mun; Lee, Sungho; Jo, Seong Mu; Yoo, Sung Jong; Cho, Eun Ae; Khil, Myung-Seob; Joh, Han-Ik

    2014-11-15

    Nitrogen doped graphene oxide (Nr-GO) with properties suitable for electrocatalysts is easily synthesized using phenylhydrazine as a reductant at relatively low temperature. The reducing agent removes various oxygen functional groups bonded to graphene oxide and simultaneously dope the nitrogen atoms bonded with phenyl group all over the basal planes and edge sites of the graphene. The Nr-GO exhibits remarkable electrocatalytic activities for oxygen reduction reaction compared to the commercial carbon black and graphene oxide due to the electronic modification of the graphene structure. In addition, Nr-GO shows excellent dispersibility in various solvent due to the dopant molecules.

  5. Covalent functionalization based heteroatom doped graphene nanosheet as a metal-free electrocatalyst for oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Park, Minju; Lee, Taemin; Kim, Byeong-Su

    2013-11-01

    Oxygen reduction reaction (ORR) is an important reaction in energy conversion systems such as fuel cells and metal-air batteries. Carbon nanomaterials doped with heteroatoms are highly attractive materials for use as electrocatalysts by virtue of their excellent electrocatalytic activity, high conductivity, and large surface area. This study reports the synthesis of highly efficient electrocatalysts based on heteroatom-doped graphene nanosheets prepared through covalent functionalization using various small organic molecules and a subsequent thermal treatment. A series of nitrogen-doped reduced graphene oxide (NRGOn) nanosheets exhibited varying degrees and configurations of nitrogen atoms within the graphitic framework depending on the type of precursors used. On the basis of the rotating disk electrode (RDE) and rotating ring-disk electrode (RRDE) experiments, NRGO3, with a high degree of pyridinic-N content, displayed the desired one-step, quasi-four-electron transfer pathway during ORR, similar to commercial Pt/C. We also demonstrated the potential of covalent functionalization of sulfur and boron-doped graphene nanosheets.Oxygen reduction reaction (ORR) is an important reaction in energy conversion systems such as fuel cells and metal-air batteries. Carbon nanomaterials doped with heteroatoms are highly attractive materials for use as electrocatalysts by virtue of their excellent electrocatalytic activity, high conductivity, and large surface area. This study reports the synthesis of highly efficient electrocatalysts based on heteroatom-doped graphene nanosheets prepared through covalent functionalization using various small organic molecules and a subsequent thermal treatment. A series of nitrogen-doped reduced graphene oxide (NRGOn) nanosheets exhibited varying degrees and configurations of nitrogen atoms within the graphitic framework depending on the type of precursors used. On the basis of the rotating disk electrode (RDE) and rotating ring-disk electrode

  6. Advances in interactive supported electrocatalysts for hydrogen and oxygen electrode reactions

    NASA Astrophysics Data System (ADS)

    Krstajic, Nedeljko V.; Vracar, Ljiljana M.; Radmilovic, Velimir R.; Neophytides, Stelios G.; Labou, Miranda; Jaksic, Jelena M.; Tunold, Reidar; Falaras, Polycarpos; Jaksic, Milan M.

    2007-05-01

    Magneli phases [A. Magneli, Acta Chem. Scand. 13 (1959) 5] have been introduced as a unique electron conductive and interactive support for electrocatalysis both in hydrogen (HELR) and oxygen (OELR) electrode reactions in water electrolysis and Low Temperature PEM Fuel Cells (LT PEM FC). The Strong Metal-Support Interaction (SMSI) that imposes the former implies: (i) the hypo-hyper-d-interbonding effect and its catalytic consequences, and (ii) the interactive primary oxide (M-OH) spillover from the hypo-d-oxide support as a dynamic electrocatalytic contribution. The stronger the bonding, the more strained appear d-orbitals, thereby the less strong the intermediate adsorptive strength in the rate determining step (RDS), and consequently, the faster the facilitated catalytic electrode reaction arises. At the same time the primary oxide spillover transferred from the hypo-d-oxide support directly interferes and reacts either individually and directly to contribute to finish the oxygen reduction, or with other interactive species, like CO to contribute to the CO tolerance. In such a respect, the conditions to provide Au to act as the reversible hydrogen electrode have been proved either by its potentiodynamic surface reconstruction in a heavy water solution, or by the nanostructured SMSI Au on anatase titania with characteristic strained d-orbitals in such a hypo-hyper-d-interactive bonding (Au/TiO 2). In the same context, some spontaneous tendency towards monoatomic network dispersion of Pt upon Magneli phases makes it possible to produce an advanced interactive supported electrocatalyst for cathodic oxygen reduction (ORR). The strained hypo-hyper-d-interelectronic and inter-d-orbital metal/hypo-d-oxide support bonding relative to the strength of the latter, has been inferred to be the basis of the synergistic electrocatalytic effect both in the HELR and ORR.

  7. Relationships between structure and activity of carbon as a multifunctional support for electrocatalysts.

    PubMed

    Stevanović, Sanja I; Panić, Vladimir V; Dekanski, Aleksandar B; Tripković, Amalija V; Jovanović, Vladislava M

    2012-07-14

    We report on new insights into the relationships between structure and activity of glassy carbon (GC), as a model material for electrocatalyst support, during its anodization in acid solution. Our investigation strongly confirms the role of CFGs in promotion of Pt activity by the "spill-over" effect related to CO(ads) for methanol electrooxidation (MEO) on a carbon-supported Pt catalyst. Combined analysis of voltammetric and impedance behaviour as well as changes in GC surface morphology induced by intensification of anodizing conditions reveal an intrinsic influence of the carbon functionalization and the structure of a graphene oxide (GO) layer on the electrical and electrocatalytic properties of activated GC. Although GO continuously grows during anodization, it structurally changes from being a graphite inter-layer within graphite ribbons toward a continuous GO surface layer that deteriorates the native structure of GC. As a consequence of the increased distance between GO-spaced graphite layers, the GC conductivity decreases until the case of profound GO exfoliation under drastic anodizing conditions. This exposes the native, yet abundantly functionalized, GC texture. While GC capacitance continuously increases with intensification of anodizing conditions, the surface nano-roughness and GO resistance reach the highest values at modest anodizing conditions, and then decrease upon drastic anodization due to the onset of GO exfoliation. We found for the first time that the activity of a GC-supported Pt catalyst in MEO, as one of the promising half-reactions in polymer electrolyte fuel cells, strictly follows the changes in GC nano-roughness and GO-induced GC resistance. The highest GC/Pt MEO activity is reached when optimal distance between graphite layers and optimal degree of GC functionalization bring the highest amount of CFGs into intimate contact with the Pt surface. This confirms the promoting role of CFGs in MEO catalysis. PMID:22648036

  8. Electrocatalysts for oxygen electrodes in fuel cells and water electrolyzers for space applications

    NASA Technical Reports Server (NTRS)

    Prakash, Jai; Tryk, Donald; Yeager, Ernest

    1989-01-01

    In most instances separate electrocatalysts are needed to promote the reduction of O2 in the fuel cell mode and to generate O2 in the energy storage-water electrolysis mode in aqueous electrochemical systems operating at low and moderate temperatures (T greater than or equal to 200 C). Interesting exceptions are the lead and bismuth ruthenate pyrochlores in alkaline electrolytes. These catalysts on high area carbon supports have high catalytic activity for both O2 reduction and generation (1,2). Rotating ring-disk electrode measurements provide evidence that the O2 reduction proceeds by a parallel four-electron pathway. The ruthenates can also be used as self-supported catalysts to avoid the problems associated with carbon oxidation, but the electrode performance so far achieved in the research at Case Western Reserve University (CWRU) is considerably less. At the potentials involved in the anodic mode the ruthenate pyrochlores have substantial equilibrium solubility in concentrated alkaline electrolyte. This results in the loss of catalyst into the bulk solution and a decline in catalytic activity. Furthermore, the hydrogen generation counter electrode may become contaminated with reduction products from the pyrochlores (lead, ruthenium). A possible approach to this problem is to immobilize the pyrochlore catalyst within an ionic-conducting solid polymer, which would replace the fluid electrolyte within the porous gas diffusion O2 electrode. For bulk alkaline electrolyte, an anion-exchange polymer is needed with a transference number close to unity for the Oh(-) ion. Preliminary short-term measurements with lead ruthenates using a commercially available partially-fluorinated anion-exchange membrane as an overlayer on the porous gas-fed electrode indicate lower anodic polarization and virtually unchanged cathodic polarization.

  9. Electrocatalysts for oxygen electrodes in fuel cells and water electrolyzers for space applications

    NASA Astrophysics Data System (ADS)

    Prakash, Jai; Tryk, Donald; Yeager, Ernest

    1989-12-01

    In most instances separate electrocatalysts are needed to promote the reduction of O2 in the fuel cell mode and to generate O2 in the energy storage-water electrolysis mode in aqueous electrochemical systems operating at low and moderate temperatures (T greater than or equal to 200 C). Interesting exceptions are the lead and bismuth ruthenate pyrochlores in alkaline electrolytes. These catalysts on high area carbon supports have high catalytic activity for both O2 reduction and generation (1,2). Rotating ring-disk electrode measurements provide evidence that the O2 reduction proceeds by a parallel four-electron pathway. The ruthenates can also be used as self-supported catalysts to avoid the problems associated with carbon oxidation, but the electrode performance so far achieved in the research at Case Western Reserve University (CWRU) is considerably less. At the potentials involved in the anodic mode the ruthenate pyrochlores have substantial equilibrium solubility in concentrated alkaline electrolyte. This results in the loss of catalyst into the bulk solution and a decline in catalytic activity. Furthermore, the hydrogen generation counter electrode may become contaminated with reduction products from the pyrochlores (lead, ruthenium). A possible approach to this problem is to immobilize the pyrochlore catalyst within an ionic-conducting solid polymer, which would replace the fluid electrolyte within the porous gas diffusion O2 electrode. For bulk alkaline electrolyte, an anion-exchange polymer is needed with a transference number close to unity for the Oh(-) ion. Preliminary short-term measurements with lead ruthenates using a commercially available partially-fluorinated anion-exchange membrane as an overlayer on the porous gas-fed electrode indicate lower anodic polarization and virtually unchanged cathodic polarization.

  10. Nano/micro-patterning the membrane-electrocatalyst layer for fuel cell applications

    NASA Astrophysics Data System (ADS)

    Omosebi, Ayokunle O.

    Polymer electrolyte membrane fuel cells (PEMFCs) are high energy density electrochemical devices capable of directly converting stored chemical potential into electricity. Their many attributes, including low emissions, quiet operation, scalability, modularity and efficiency make them attractive alternatives to conventional portable and stationary power sources. The emergence of the PEMFC as a dominant technology for electrical power generation is however currently limited by performance losses and the cost of the membrane electrode assembly (MEA). The basic architecture of the MEA, which has remained largely unchanged for over four decades, consists of ink-based platinum supported on carbon catalyst layers dispersed on either side of a Nafion membrane. In order to generate power from the electrochemical reaction, protons, electrons, and oxidant must be available at the catalyst layer-Nafion ionomer interface. As such, to improve performance, the availability of this interface should be maximized without increasing the transport resistance for reactants accessing the reaction plane. To achieve this objective, the membrane-electrode interface could be restructured to possess a larger interfacial area by creating nano/microfeatures on the Nafion membrane. This work introduces electron beam lithography coupled with dry etching and sputtering strategies for creating membrane-electrode structures with over-potential suppression characteristics in PEMFCs. Electron beam lithography provides the ability to fabricate nano/microfeatures in an electron beam sensitive material, while pattern transfer and aspect-ratio control is achieved with dry etching. Conventional and ultra-thin catalyst layers were fabricated by spraying and sputter deposition, and methanol and hydrogen were tested as fuels. Experiments involving the patterned MEA elucidate improved properties that lead to PEMFC performance enhancement. The ability to directly pattern a Nafion membrane-electrocatalyst

  11. Synthesis and Characterization of CO- and H2S- Tolerant Electrocatalysts for PEM Fuel Cell

    SciTech Connect

    Shamsuddin Ilias

    2006-12-31

    The present state-of-art Proton Exchange Membrane Fuel Cell (PEMFC) technology is based on platinum (Pt) as a catalyst for both the fuel (anode) and air (cathode) electrodes. This catalyst is highly active but susceptible to poisoning by CO, which may be present in the H{sub 2}-fuel used or may be introduced during the fuel processing. Presence of trace amount of CO in the H{sub 2}-fuel poisons the anode irreversibly and decreases the performance of the PEMFCs. In an effort to reduce the Pt-loading and improve the PEMFC performance, we have synthesized a number of Pt-based binary, ternary, and quaternary electrocatalysts using Ru, Mo, Ir, Ni, and Co as a substitute for Pt. Co-catalytic activities were found for the elements Mo, Ru, and Ir. Both the ternary (Pt/Ru/Mo/C) and quaternary (Pt/Ru/Mo/Ir/C) metal catalysts in membrane electrode assemblies (MEA) outperformed pure Pt/C catalysts at all levels in presence of CO up to 100 ppm. Preliminary results suggest that by substituting Mo, Ru, and Ir in catalyst formulation, it is possible to reduce Pt-loading and increase CO-tolerance in PEMFC application. Comparison studies showed that the newly developed ternary and quaternary catalysts with lower Pt outperformed pure Pt catalyst in presence of CO-contaminated H{sub 2} fuel. High performance at low Pt loading of less than 0.4 mg/cm{sup 2} was achieved, thus exceeding the initial targets.

  12. Kinetic Analysis of Competitive Electrocatalytic Pathways: New Insights into Hydrogen Production with Nickel Electrocatalysts.

    PubMed

    Wiedner, Eric S; Brown, Houston J S; Helm, Monte L

    2016-01-20

    The hydrogen production electrocatalyst Ni(P(Ph)2N(Ph)2)2(2+) (1) is capable of traversing multiple electrocatalytic pathways. When using dimethylformamidium, DMF(H)(+), the mechanism of H2 formation by 1 changes from an ECEC to an EECC mechanism as the potential approaches the Ni(I/0) couple. Two electrochemical methods, current-potential analysis and foot-of-the-wave analysis (FOWA), were performed on 1 to measure detailed kinetics of the competing ECEC and EECC pathways. A sensitivity analysis was performed on the methods using digital simulations to understand their strengths and limitations. Chemical rate constants were significantly underestimated when not accounting for electron-transfer kinetics, even when electron transfer was fast enough to afford a reversible noncatalytic wave. The EECC pathway of 1 was faster than the ECEC pathway under all conditions studied. Buffered DMF:DMF(H)(+) mixtures afforded an increase in the catalytic rate constant (k(obs)) of the EECC pathway, but k(obs) for the ECEC pathway did not change when using buffered acid. Further kinetic analysis of the ECEC path revealed that base increases the rate of isomerization from exo-protonated Ni(0) isomers to the catalytically active endo-isomers, but decreases the rate of protonation of Ni(I). FOWA did not provide accurate rate constants, but FOWA was used to estimate the reduction potential of the previously undetected exo-protonated Ni(I) intermediate. Comparison of catalytic Tafel plots for 1 under different conditions reveals substantial inaccuracies in the turnover frequency at zero overpotential when the kinetic and thermodynamic effects of the conjugate base are not accounted for properly. PMID:26692398

  13. Preparation and characterization of Pt-CeO2/C and Pt-TiO2/C electrocatalysts with improved electrocatalytic activity for methanol oxidation

    NASA Astrophysics Data System (ADS)

    Hameed, R. M. Abdel; Amin, R. S.; El-Khatib, K. M.; Fetohi, Amani E.

    2016-03-01

    Pt-TiO2/C and Pt-CeO2/C electrocatalysts were synthesized by solid state reaction of TiO2/C and CeO2/C powders using intermittent microwave heating, followed by chemical reduction of platinum ions using mixed reducing agents of ethylene glycol and sodium borohydride. The crystal structure, surface morphology and chemical composition of prepared electrocatalysts were investigated using X-ray diffraction (XRD), transmission electron microscopy (TEM) and energy dispersive X-ray analysis (EDX). The phase angle values of different Pt diffraction planes in Pt-TiO2/C and Pt-CeO2/C were shifted in the positive direction relative to those in Pt/C. Pt particles with diameter values of 3.06 and 2.78 nm were formed in Pt-TiO2/C and Pt-CeO2/C, respectively. The electrochemical performance of prepared electrocatalysts was examined using cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy. Pt-CeO2/C showed an enhanced oxidation current density when compared to Pt/C. Long time oxidation test at Pt-TiO2/C and Pt-CeO2/C revealed their improved stability. Lower charge transfer resistance values were estimated at Pt-metal oxide/C electrocatalysts.

  14. Co/CoO nanoparticles immobilized on Co-N-doped carbon as trifunctional electrocatalysts for oxygen reduction, oxygen evolution and hydrogen evolution reactions.

    PubMed

    Zhang, Xian; Liu, Rongrong; Zang, Yipeng; Liu, Guoqiang; Wang, Guozhong; Zhang, Yunxia; Zhang, Haimin; Zhao, Huijun

    2016-05-01

    Co/CoO nanoparticles immobilized on Co-N-doped carbon were successfully developed using shrimp-shell derived N-doped carbon nanodots as precursors by a combined approach of polymerization and pyrolysis, as electrocatalysts exhibiting trifunctional catalytic activities toward oxygen reduction, oxygen evolution and hydrogen evolution reactions and high performance in rechargeable zinc-air batteries. PMID:27056374

  15. Spontaneous incorporation of gold in palladium-based ternary nanoparticles makes durable electrocatalysts for oxygen reduction reaction

    DOE PAGESBeta

    Wang, Deli; Liu, Sufen; Wang, Jie; Lin, Ruoqian; Kawasaki, Masahiro; Rus, Eric; Silberstein, Katharine E.; Lowe, Michael A.; Lin, Feng; Nordlund, Dennis; et al

    2016-06-23

    Replacing platinum by a less precious metal such as palladium, is highly desirable for lowering the cost of fuel-cell electrocatalysts. However, the instability of palladium in the harsh environment of fuel-cell cathodes renders its commercial future bleak. Here we show that by incorporating trace amounts of gold in palladium-based ternary (Pd6CoCu) nanocatalysts, the durability of the catalysts improves markedly. Using aberration-corrected analytical transmission electron microscopy in conjunction with synchrotron X-ray absorption spectroscopy, we show that gold not only galvanically replaces cobalt and copper on the surface, but also penetrates through the Pd–Co–Cu lattice and distributes uniformly within the particles. Themore » uniform incorporation of Au provides a stability boost to the entire host particle, from the surface to the interior. The spontaneous replacement method we have developed is scalable and commercially viable. This work may provide new insight for the large-scale production of non-platinum electrocatalysts for fuel-cell applications.« less

  16. Highly Active Pt(3)Pb and Core-Shell Pt(3)Pb-Pt Electrocatalysts for Formic Acid Oxidation

    SciTech Connect

    Kang Y.; Stach E.; Qi L.; Li M.; Diaz R.E.; Su D.; Adzic R.R.; Li J.; Murray C.B.

    2012-03-27

    Formic acid is a promising chemical fuel for fuel cell applications. However, due to the dominance of the indirect reaction pathway and strong poisoning effects, the development of direct formic acid fuel cells has been impeded by the low activity of existing electrocatalysts at desirable operating voltage. We report the first synthesis of Pt{sub 3}Pb nanocrystals through solution phase synthesis and show they are highly efficient formic acid oxidation electrocatalysts. The activity can be further improved by manipulating the Pt{sub 3}Pb-Pt core-shell structure. Combined experimental and theoretical studies suggest that the high activity from Pt{sub 3}Pb and the Pt-Pb core-shell nanocrystals results from the elimination of CO poisoning and decreased barriers for the dehydrogenation steps. Therefore, the Pt{sub 3}Pb and Pt-Pb core-shell nanocrystals can improve the performance of direct formic acid fuel cells at desired operating voltage to enable their practical application.

  17. A new symmetric solid oxide fuel cell with a samaria-doped ceria framework and a silver-infiltrated electrocatalyst

    NASA Astrophysics Data System (ADS)

    Lin, Ye; Su, Chao; Huang, Cheng; Kim, Ju Sik; Kwak, Chan; Shao, Zongping

    2012-01-01

    A new symmetric SOFC with an SDC framework and a silver-infiltrated electrocatalyst is presented for the first time in this paper. A three-electrode polarization test shows that the Ag-SDC has a low area specific resistance of 1.07 Ω cm2 at 600 °C, a low activation energy of 85 kJ mol-1 and high exchange current densities of 428.2 and 129.0 mA cm-2 at 750 and 650 °C, respectively, when it is used as an oxygen reduction electrode. It also exhibits low polarization resistance in a humidified hydrogen atmosphere. A symmetric single cell is used in real fuel cell conditions to deliver peak power densities of 200 and 84 mW cm-2 at 750 and 650 °C, respectively, when humidified hydrogen is used as a fuel and ambient air is used as the cathode atmosphere. The cell still reaches a peak power density of 81 mW cm-2 at 750 °C when operating on CO. O2-TPO analysis demonstrates that the Ag-SDC electrode has even better coking resistance than the pure SDC scaffold. The results indicate that Ag-SDC|SDC|Ag-SDC symmetric cells with an infiltrated silver electrocatalyst are a promising new type of fuel cell for use with both hydrogen fuel and carbon-containing fuels.

  18. Self-organized macroporous carbon structure derived from phenolic resin via spray pyrolysis for high-performance electrocatalyst.

    PubMed

    Balgis, Ratna; Sago, Sumihito; Anilkumar, Gopinathan M; Ogi, Takashi; Okuyama, Kikuo

    2013-11-27

    The synthesis and evaluation of porous carbon derived from phenolic resin using a fast and facile spray pyrolysis method has been studied for use as a new electrocatalyst support material. By adding polystyrene latex nanoparticles as a template to the phenolic resin precursor, self-organized macroporous carbon structure was first developed. The mass ratio of phenolic resin to PSL at 0.625 gave the optimum porous morphology. Pt nanoparticles (∼20 wt %) were grown on the carbon surface using a standard industrial impregnation method. Well-dispersed Pt nanoparticles of average size 3.91 nm were observed on the surface of porous carbon particles. The high catalytic performance of porous Pt/C electrocatalyst was confirmed by the high mass activity and electrochemically active surface area, which were 450.81 mA mg(-1)-Pt and 81.78 m(2) g(-1)-Pt, respectively. The porous Pt/C catalyst obtains two times higher mass activity than that of the commercial Pt/C catalyst and performs excellent durability under acid conditions. PMID:24171401

  19. Hierarchical NiCo2 O4 Hollow Microcuboids as Bifunctional Electrocatalysts for Overall Water-Splitting.

    PubMed

    Gao, Xuehui; Zhang, Hongxiu; Li, Quanguo; Yu, Xuegong; Hong, Zhanglian; Zhang, Xingwang; Liang, Chengdu; Lin, Zhan

    2016-05-17

    Bifunctional electrocatalysts for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in alkaline electrolyte may improve the efficiency of overall water splitting. Nickel cobaltite (NiCo2 O4 ) has been considered a promising electrode material for the OER. However, NiCo2 O4 that can be used as an electrocatalyst in HER has not been studied yet. Herein, we report self-assembled hierarchical NiCo2 O4 hollow microcuboids for overall water splitting including both the HER and OER reactions. The NiCo2 O4 electrode shows excellent activity toward overall water splitting, with 10 mA cm(-2) water-splitting current reached by applying just 1.65 V and 20 mA cm(-2) by applying just 1.74 V across the two electrodes. The synthesis of NiCo2 O4 microflowers confirms the importance of structural features for high-performance overall water splitting. PMID:27061909

  20. Promoting effect of Co in Ni(m)Co(n) (m + n = 4) bimetallic electrocatalysts for methanol oxidation reaction.

    PubMed

    Cui, Xun; Guo, Wenlong; Zhou, Ming; Yang, Yang; Li, Yanhong; Xiao, Peng; Zhang, Yunhuai; Zhang, Xiaoxing

    2015-01-14

    Ni-based bimetallic alloys have superior physiochemical characteristics compared to monometallic Ni. In this study, a new type of low cost bimetallic NimCon (n + m = 4) electrocatalysts with high active surface were synthesized on Ti substrate through a hydrogen evolution assisted electrodeposition method. The as-prepared NimCon were characterized by XRD, EDS, and SEM. It was revealed that the composition, surface morphology, as well as the crystal phase structure of the bimetallic NimCon electrocatalysts were significantly changed with the increased content of cobalt. Electrochemical measurements showed that the bimetallic NimCon catalysts, compared with the monometallic Ni, have superior catalytic activity and stability toward the methanol electrooxidation reaction. Additionally, Ni2Co2 sample presented the highest oxidation current density and the best durability. The mechanism study based on electrochemical experiments and density functional theory based calculations showed that the doping of Co in NimCon can signally improve the surface coverage of the redox species, weaken the CO adsorption, as well as adjust the CH3OH adsorption. Such understanding is of important directive significance to design efficient nonprecious catalysts. PMID:25482138

  1. Iron-rich nanoparticle encapsulated, nitrogen doped porous carbon materials as efficient cathode electrocatalyst for microbial fuel cells

    NASA Astrophysics Data System (ADS)

    Lu, Guolong; Zhu, Youlong; Lu, Lu; Xu, Kongliang; Wang, Heming; Jin, Yinghua; Jason Ren, Zhiyong; Liu, Zhenning; Zhang, Wei

    2016-05-01

    Developing efficient, readily available, and sustainable electrocatalysts for oxygen reduction reaction (ORR) in neutral medium is of great importance to practical applications of microbial fuel cells (MFCs). Herein, a porous nitrogen-doped carbon material with encapsulated Fe-based nanoparticles (Fe-Nx/C) has been developed and utilized as an efficient ORR catalyst in MFCs. The material was obtained through pyrolysis of a highly porous organic polymer containing iron(II) porphyrins. The characterizations of morphology, crystalline structure and elemental composition reveal that Fe-Nx/C consists of well-dispersed Fe-based nanoparticles coated by N-doped graphitic carbon layer. ORR catalytic performance of Fe-Nx/C has been evaluated through cyclic voltammetry and rotating ring-disk electrode measurements, and its application as a cathode electrocatalyst in an air-cathode single-chamber MFC has been investigated. Fe-Nx/C exhibits comparable or better performance in MFCs than 20% Pt/C, displaying higher cell voltage (601 mV vs. 591 mV), maximum power density (1227 mW m-2 vs. 1031 mW m-2) and Coulombic efficiency (50% vs. 31%). These findings indicate that Fe-Nx/C is more tolerant and durable than Pt/C in a system with bacteria metabolism and thus holds great potential for practical MFC applications.

  2. A novel electrocatalyst for oxygen evolution reaction based on rational anchoring of cobalt carbonate hydroxide hydrate on multiwall carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Zhang, Yuxia; Xiao, Qingqing; Guo, Xin; Zhang, Xiaoxue; Xue, Yifei; Jing, Lin; Zhai, Xue; Yan, Yi-Ming; Sun, Kening

    2015-03-01

    Cobalt carbonate hydroxide hydrate (CCHH) nanosheets have been densely and strongly anchored onto mildly oxidized multiwalled carbon nanotubes with the assistance of diethylenetriamine (DETA). The resulted hybrid (CCHH/MWCNT) is used as high efficient electrocatalyst for water oxidation with an extremely low onset potential of ∼1.47 V vs. RHE and an overpotential of 285 mV to achieve a current density of 10 mA cm-2 in 1.0 mol L-1 KOH. The CCHH/MWCNT electrode affords a Tafel slope of 51 mV/decade and an exchange current density of 2.5 × 10-7 A cm-2. Moreover, the CCHH/MWCNT catalyst delivers a high faradic efficiency of 95% and possesses remarkable stability for long-term electrolysis of water. By contrast, neither MWCNT nor CCHH exhibits apparent catalytical activity towards water oxidation. Importantly, we demonstrate that DETA plays crucial role in determining the morphology, structure of the CCHH/MWCNT, therefore resulting in an enhanced performance for water oxidation. This work not only provides a novel cobalt-based electrocatalyst for oxygen evolution, but also offers a useful and viable approach to deliberately synthesize functional nanocomposites for applications in energy conversion and storage.

  3. Platinum Supported on NbRuyOz as Electrocatalyst for Ethanol Oxidation in Acid and Alkaline Fuel Cells

    SciTech Connect

    Kotaro, S.; Konopka, D.A.; Li, M.; Artyushkova, K.; Marinkovic, N.; Adzic, R.; Ward, T.L.; Atanassov, P.

    2011-02-02

    Platinum supported on a mixed metal oxide, NbRu{sub y}O{sub z} (8Nb:1Ru), was evaluated as an electrocatalyst for the ethanol oxidation reaction (EOR) in 0.1 M HClO{sub 4} and 1 M KOH. The support was synthesized from a liquid precursor solution of metal chlorides that was aerosolized and thermally decomposed into a powder via the spray pyrolysis (SP) process. Two samples were of primary interest: 30%Pt deposited onto the support by dry impregnation and 60%Pt as part of the precursor solution that underwent in situ SP Pt dispersion. TEM, SEM, and XRD were used to confirm morphology and deposition of Pt. XPS and XAS studies confirmed elemental distribution and oxidation state of Pt catalyst. In situ IRRAS studies in 0.1 M HClO{sub 4} show that these electrocatalysts are capable of facilitating the complete oxidation pathway of EOR, involving scission of the C-C bond and CO oxidation.

  4. Iron Carbide Nanoparticles Encapsulated in Mesoporous Fe-N-Doped Graphene-Like Carbon Hybrids as Efficient Bifunctional Oxygen Electrocatalysts.

    PubMed

    Jiang, Hongliang; Yao, Yifan; Zhu, Yihua; Liu, Yanyan; Su, Yunhe; Yang, Xiaoling; Li, Chunzhong

    2015-09-30

    It is highly crucial and challenging to develop bifunctional oxygen electrocatalysts for oxygen reduction reactions (ORRs) and oxygen evolution reactions (OERs) in rechargeable metal-air batteries and unitized regenerative fuel cells (URFCs). Herein, a facile and cost-effective strategy is developed to prepare mesoporous Fe-N-doped graphene-like carbon architectures with uniform Fe3C nanoparticles encapsulated in graphitic layers (Fe3C@NG) via a one-step solid-state thermal reaction. The optimized Fe3C@NG800-0.2 catalyst shows comparable ORR activity with the state-of-the-art Pt/C catalyst and OER activity with the benchmarking RuO2 catalyst. The oxygen electrode activity parameter ΔE (the criteria for judging the overall catalytic activity of bifunctional electrocatalysts) value for Fe3C@NG800-0.2 is 0.780 V, which surpasses those of Pt/C and RuO2 catalysts as well as those of most nonprecious metal catalysts. Significantly, excellent long-term catalytic durability holds great promise in fields of rechargeable metal-air batteries and URFCs. PMID:26371772

  5. Spontaneous incorporation of gold in palladium-based ternary nanoparticles makes durable electrocatalysts for oxygen reduction reaction.

    PubMed

    Wang, Deli; Liu, Sufen; Wang, Jie; Lin, Ruoqian; Kawasaki, Masahiro; Rus, Eric; Silberstein, Katharine E; Lowe, Michael A; Lin, Feng; Nordlund, Dennis; Liu, Hongfang; Muller, David A; Xin, Huolin L; Abruña, Héctor D

    2016-01-01

    Replacing platinum by a less precious metal such as palladium, is highly desirable for lowering the cost of fuel-cell electrocatalysts. However, the instability of palladium in the harsh environment of fuel-cell cathodes renders its commercial future bleak. Here we show that by incorporating trace amounts of gold in palladium-based ternary (Pd6CoCu) nanocatalysts, the durability of the catalysts improves markedly. Using aberration-corrected analytical transmission electron microscopy in conjunction with synchrotron X-ray absorption spectroscopy, we show that gold not only galvanically replaces cobalt and copper on the surface, but also penetrates through the Pd-Co-Cu lattice and distributes uniformly within the particles. The uniform incorporation of Au provides a stability boost to the entire host particle, from the surface to the interior. The spontaneous replacement method we have developed is scalable and commercially viable. This work may provide new insight for the large-scale production of non-platinum electrocatalysts for fuel-cell applications. PMID:27336795

  6. Synthesis of Hollow Platinum-Palladium Nanospheres with a Dendritic Shell as Efficient Electrocatalysts for Methanol Oxidation.

    PubMed

    Lu, Qingqing; Wang, Hongjing; Eid, Kamel; Alothman, Zeid Abdullah; Malgras, Victor; Yamauchi, Yusuke; Wang, Liang

    2016-07-01

    Engineering the size, composition, and morphology of platinum-based nanomaterials can provide a great opportunity to improve the utilization efficiency of electrocatalysts and reinforce their electrochemical performances. Herein, three-dimensional platinum-palladium hollow nanospheres with a dendritic shell (PtPd-HNSs) are successfully fabricated through a facile and economic route, during which SiO2 microspheres act as the hard template for the globular cavity, whereas the triblock copolymer F127 contributes to the formation of the dendritic shell. In contrast with platinum hollow nanospheres (Pt-HNSs) and commercial platinum on carbon (Pt/C) catalyst, the novel architecture shows a remarkable activity and durability toward the methanol oxidation reaction (MOR) owing to the coupled merits of bimetallic nanodendrites and a hollow interior. As a proof of concept, this strategy is also extended to trimetallic gold-palladium-platinum hollow nanospheres (AuPdPt-HNSs), which paves the way towards the controlled synthesis of other bi- or multimetallic platinum-based hollow electrocatalysts. PMID:27283867

  7. N-doped graphene coupled with Co nanoparticles as an efficient electrocatalyst for oxygen reduction in alkaline media

    NASA Astrophysics Data System (ADS)

    Zhang, Geng; Lu, Wangting; Cao, Feifei; Xiao, Zhidong; Zheng, Xinsheng

    2016-01-01

    Development of low-cost and highly efficient electrocatalysts for oxygen reduction reaction (ORR) is still a great challenge for the large-scale application of fuel cells and metal-air batteries. Herein, a noble metal-free ORR electrocatalyst in the form of N-doped graphene coupled with part of Co nanoparticles encased in N-doped graphitic shells (named as SUCo-0.03-800) is prepared by facile one-step pyrolysis of the mixture of sucrose, urea and cobalt nitrate. The novel structure is confirmed by High Resolution-TEM, XRD, XPS and Raman spectroscopy. SUCo-0.03-800 presents comparable ORR catalytic activity to commercial Pt/C catalyst with a dominating four-electron pathway under alkaline conditions, and both of its mass activity and volume activity also outperform Co-free N-doped graphene and other Co/N-C hybrids with higher Co content, which may probably be ascribed to the high specific surface area, novel structure and synergistic effect between encased Co nanoparticles and N-doped graphitic shell. Additionally, SUCo-0.03-800 also shows outstanding stability and improved selectivity towards ORR, making it a promising alternative to Pt with potential application in fuel cells and metal-air batteries.

  8. Hollow mesoporous carbon nitride nanosphere/three-dimensional graphene composite as high efficient electrocatalyst for oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Qin, Yong; Li, Juan; Yuan, Jie; Kong, Yong; Tao, Yongxin; Lin, Furong; Li, Shan

    2014-12-01

    Hollow mesoporous carbon nitride nanosphere (HMCN) is firstly prepared via an etching route using hollow mesoporous silica as a sacrificial template. The as-obtained HMCN is a uniform spherical particle with a diameter of ∼300 nm,and possesses a high specific surface area up to 439 m2 g-1. Hollow mesoporous carbon nitride nanosphere/three-dimensional (3D) graphene composite (HMCN-G) is subsequently fabricated via a hydrothermal treatment of HMCN with graphene oxide. As an electrocatalyst for oxygen reduction reaction (ORR), the HMCN-G shows significantly enhanced electrocatalytic activity compared to bulk graphitic carbon nitride (g-C3N4) and HMCN in terms of the electron-transfer number, current density and onset potential. Increased density of catalytically active sites and improved accessibility to electrolyte enabled by the hollow and mesoporous architecture of HMCN, and high conductivity induced from graphene are considered to contribute to the remarkable electrocatalytic performance of the HMCN-G. Furthermore, HMCN-G exhibits superior methanol tolerance to Pt/C catalyst, suggesting that it is a promising metal-free electrocatalyst for polymer electrolyte membrane fuel cell (PEMFC).

  9. Spontaneous incorporation of gold in palladium-based ternary nanoparticles makes durable electrocatalysts for oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Wang, Deli; Liu, Sufen; Wang, Jie; Lin, Ruoqian; Kawasaki, Masahiro; Rus, Eric; Silberstein, Katharine E.; Lowe, Michael A.; Lin, Feng; Nordlund, Dennis; Liu, Hongfang; Muller, David A.; Xin, Huolin L.; Abruña, Héctor D.

    2016-06-01

    Replacing platinum by a less precious metal such as palladium, is highly desirable for lowering the cost of fuel-cell electrocatalysts. However, the instability of palladium in the harsh environment of fuel-cell cathodes renders its commercial future bleak. Here we show that by incorporating trace amounts of gold in palladium-based ternary (Pd6CoCu) nanocatalysts, the durability of the catalysts improves markedly. Using aberration-corrected analytical transmission electron microscopy in conjunction with synchrotron X-ray absorption spectroscopy, we show that gold not only galvanically replaces cobalt and copper on the surface, but also penetrates through the Pd-Co-Cu lattice and distributes uniformly within the particles. The uniform incorporation of Au provides a stability boost to the entire host particle, from the surface to the interior. The spontaneous replacement method we have developed is scalable and commercially viable. This work may provide new insight for the large-scale production of non-platinum electrocatalysts for fuel-cell applications.

  10. Active Sites Implanted Carbon Cages in Core-Shell Architecture: Highly Active and Durable Electrocatalyst for Hydrogen Evolution Reaction.

    PubMed

    Zhang, Huabin; Ma, Zuju; Duan, Jingjing; Liu, Huimin; Liu, Guigao; Wang, Tao; Chang, Kun; Li, Mu; Shi, Li; Meng, Xianguang; Wu, Kechen; Ye, Jinhua

    2016-01-26

    Low efficiency and poor stability are two major challenges we encounter in the exploration of non-noble metal electrocatalysts for the hydrogen evolution reaction (HER) in both acidic and alkaline environment. Herein, the hybrid of cobalt encapsulated by N, B codoped ultrathin carbon cages (Co@BCN) is first introduced as a highly active and durable nonprecious metal electrocatalysts for HER, which is constructed by a bottom-up approach using metal organic frameworks (MOFs) as precursor and self-sacrificing template. The optimized catalyst exhibited remarkable electrocatalytic performance for hydrogen production from both both acidic and alkaline media. Stability investigation reveals the overcoating of carbon cages can effectively avoid the corrosion and oxidation of the catalyst under extreme acidic and alkaline environment. Electrochemical active surface area (EASA) evaluation and density functional theory (DFT) calculations revealed that the synergetic effect between the encapsulated cobalt nanoparticle and the N, B codoped carbon shell played the fundamental role in the superior HER catalytic performance. PMID:26649629

  11. Hollow structured carbon-supported nickel cobaltite nanoparticles as an efficient bifunctional electrocatalyst for the oxygen reduction and evolution reaction

    DOE PAGESBeta

    Wang, Jie; Han, Lili; Lin, Ruoqian; Xin, Huolin L.; Wang, Deli; Wu, Zexing

    2016-01-05

    Here, the exploration of efficient electrocatalysts for both the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is essential for fuel cells and metal-air batteries. In this study, we developed 3D hollow-structured NiCo2O4/C nanoparticles with interconnected pores as bifunctional electrocatalysts, which are transformed from solid NiCo2 alloy nanoparticles through the Kirkendall effect. The unique hollow structure of NiCo2O4 nanoparticles increases the number of active sites and improves contact with the electrolyte to result in excellent ORR and OER performances. In addition, the hollow-structured NiCo2O4/C nanoparticles exhibit superior long-term stability for both the ORR and OER compared to commercial Pt/C.more » The template- and surfactant-free synthetic strategy could be used for the low-cost and large-scale synthesis of hollow-structured materials, which would facilitate the screening of high-efficiency catalysts for energy conversion.« less

  12. Spontaneous incorporation of gold in palladium-based ternary nanoparticles makes durable electrocatalysts for oxygen reduction reaction

    PubMed Central

    Wang, Deli; Liu, Sufen; Wang, Jie; Lin, Ruoqian; Kawasaki, Masahiro; Rus, Eric; Silberstein, Katharine E.; Lowe, Michael A.; Lin, Feng; Nordlund, Dennis; Liu, Hongfang; Muller, David A.; Xin, Huolin L.; Abruña, Héctor D.

    2016-01-01

    Replacing platinum by a less precious metal such as palladium, is highly desirable for lowering the cost of fuel-cell electrocatalysts. However, the instability of palladium in the harsh environment of fuel-cell cathodes renders its commercial future bleak. Here we show that by incorporating trace amounts of gold in palladium-based ternary (Pd6CoCu) nanocatalysts, the durability of the catalysts improves markedly. Using aberration-corrected analytical transmission electron microscopy in conjunction with synchrotron X-ray absorption spectroscopy, we show that gold not only galvanically replaces cobalt and copper on the surface, but also penetrates through the Pd–Co–Cu lattice and distributes uniformly within the particles. The uniform incorporation of Au provides a stability boost to the entire host particle, from the surface to the interior. The spontaneous replacement method we have developed is scalable and commercially viable. This work may provide new insight for the large-scale production of non-platinum electrocatalysts for fuel-cell applications. PMID:27336795

  13. Role of Cu-Ion Doping in Cu-α-MnO2 Nanowire Electrocatalysts for the Oxygen Reduction Reaction

    DOE PAGESBeta

    Davis, Danae J.; Lambert, Timothy N.; Vigil, Julian A.; Rodriguez, Mark A.; Brumbach, Michael T.; Coker, Eric N.; Limmer, Steven J.

    2014-07-09

    The role of Cu-ion doping in α-MnO2 electrocatalysts for the oxygen reduction reaction in alkaline electrolyte was investigated. Copper doped α-MnO2 nanowires (Cu-α-MnO2) were prepared with varying amounts of Cu2+ using a solvothermal method. The electrocatalytic dataindicates that Cu-α-MnO2 nanowires have higher terminal current densities, enhanced kinetic rate constants, and improved charge transfer resistances that trend with Cu-content, exceeding values attained by α-MnO2 alone. The observed improvement in catalytic behavior correlates with an increase in Mn3+ content for the Cu-α-MnO2 nanowires. The Mn3+/Mn4+ couple is themediator for the rate-limiting redox driven O2-/OH- exchange. It is proposed that O2 adsorbs viaanmore » axial site (the eg orbital on the Mn3+ d4 ion) at the surface, or at edge defects, of the nanowireand that the increase in covalent nature of the nanowire with Cu-ion doping leads to stabilization of O2 adsorbates and faster rates of reduction. This work is applicable to other manganese oxide electrocatalysts and shows for the first time there is a correlation for manganese oxides between electrocatalytic activity for the ORR in alkaline electrolyte and an increase in Mn3+ character of the oxide.« less

  14. Heteroatoms ternary-doped porous carbons derived from MOFs as metal-free electrocatalysts for oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Li, Ji-Sen; Li, Shun-Li; Tang, Yu-Jia; Li, Kui; Zhou, Lei; Kong, Ning; Lan, Ya-Qian; Bao, Jian-Chun; Dai, Zhi-Hui

    2014-05-01

    The nitrogen (N), phosphorus (P) and sulphur (S) ternary-doped metal-free porous carbon materials have been successfully synthesized using MOFs as templates (denoted as NPS-C-MOF-5) for oxygen reduction reaction (ORR) for the first time. The influences of porous carbons from carbonizing different MOFs and carbonization temperature on ORR have been systematically investigated. Due to the synergistic effect of N, P and S ternary-doping, the NPS-C-MOF-5 catalyst shows a higher onset potential as a metal-free electrocatalyst for ORR among the currently reported metal-free electrocatalysts, very close to the commercial Pt-C catalyst. In particular, the kinetic limiting current density of NPS-C-MOF-5 catalyst at -0.6 V is up to approximate -11.6 mA cm-2, which is 1.2 times higher than that of the commercial Pt-C catalyst. Furthermore, the outstanding methanol tolerance and excellent long-term stability of NPS-C-MOF-5 are superior to those of the commercial Pt-C catalyst for ORR in alkaline media.

  15. Development of efficient electrocatalysts via molecular hybridization of NiMn layered double hydroxide nanosheets and graphene.

    PubMed

    Ma, Wei; Ma, Renzhi; Wu, Jinghua; Sun, Pengzhan; Liu, Xiaohe; Zhou, Kechao; Sasaki, Takayoshi

    2016-05-21

    Ni(2+)Mn(3+) layered double hydroxide (LDH) nanoplatelets have been hydrothermally synthesized in a homogeneous precipitation of mixed Ni(2+)/Mn(2+) salts at a molar ratio of 2 : 1 via the hydrolysis of hexamethylenetetramine (HMT) and in situ oxidation with H2O2. After anion-exchange, NiMn LDH was exfoliated into unilamellar nanosheets. Subsequent flocculation of NiMn LDH nanosheets with (reduced) graphene oxide (GO/rGO) into superlattice composites was achieved and further tested as electrocatalysts for oxygen evolution reaction (OER). The face-to-face heteroassembly of NiMn LDH nanosheets with conductive rGO at an alternating sequence resulted in a small overpotential of 0.26 V and a Tafel slope of 46 mV per decade, which is much superior to as-exfoliated nanosheets. The analyses of electrochemical activity surface area (ECSA) and impedance spectra clearly indicated that the superlattice structure was ideal in facilitating the migration/transfer of the charge and reactants, revealing the electrochemical energetics and mechanism behind the synergistic effect arising from molecular hybridization. The proof of concept toward total water splitting using the newly developed hybrid electrocatalyst was demonstrated by an electrolysis cell powered by a single AA battery. PMID:27142232

  16. Characterization of Au and Bimetallic PtAu Nanoparticles on PDDA-Graphene Sheets as Electrocatalysts for Formic Acid Oxidation

    NASA Astrophysics Data System (ADS)

    Yung, Tung-Yuan; Liu, Ting-Yu; Huang, Li-Ying; Wang, Kuan-Syun; Tzou, Huei-Ming; Chen, Po-Tuan; Chao, Chi-Yang; Liu, Ling-Kang

    2015-09-01

    Nanocomposite materials of the Au nanoparticles (Au/PDDA-G) and the bimetallic PtAu nanoparticles on poly-(diallyldimethylammonium chloride) (PDDA)-modified graphene sheets (PtAu/PDDA-G) were prepared with hydrothermal method at 90 °C for 24 h. The composite materials Au/PDDA-G and PtAu/PDDA-G were evaluated by transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA) for exploring the structural characterization for the electrochemical catalysis. According to TEM results, the diameter of Au and bimetallic PtAu nanoparticles is about 20-50 and 5-10 nm, respectively. X-ray diffraction (XRD) results indicate that both of PtAu and Au nanoparticles exhibit the crystalline plane of (111), (200), (210), and (311). Furthermore, XRD data also show the 2°-3° difference between pristine graphene sheets and the PDDA-modified graphene sheets. For the catalytic activity tests of Au/PDDA-G and PtAu/PDDA-G, the mixture of 0.5 M aqueous H2SO4 and 0.5 M aqueous formic acid was used as model to evaluate the electrochemical characterizations. The catalytic activities of the novel bimetallic PtAu/graphene electrocatalyst would be anticipated to be superior to the previous electrocatalyst of the cubic Pt/graphene.

  17. Enhanced activity of Au-Fe/C anodic electrocatalyst for direct borohydride-hydrogen peroxide fuel cell

    NASA Astrophysics Data System (ADS)

    Yi, Lanhua; Wei, Wei; Zhao, Caixian; Tian, Li; Liu, Jing; Wang, Xianyou

    2015-07-01

    Carbon supported Au-Fe bimetallic nanocatalysts (Au-Fe/C) are facilely prepared via a modified NaBH4 reduction method in aqueous solution at room temperature, and used as the anode electrocatalyst of direct borohydride-hydrogen peroxide fuel cell (DBHFC). The physical and electrochemical properties of the Au-Fe/C electrocatalysts are characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), cyclic voltammetry (CV), rotating disc electrode (RDE) voltammetry, chronoamperometry (CA), chronopotentiometry (CP), and fuel cell test. The results show that Au-Fe/C catalysts display higher catalytic activity for the direct electrooxidation of BH4- than carbon supported pure Au nanocatalyst (Au/C), especially Au50Fe50/C catalyst presents the highest catalytic activity among all as-prepared catalysts. Besides, the single DBHFC with Au50Fe50/C anode and Au/C cathode obtains the maximum power density as high as 34.9 mW cm-2 at 25 °C.

  18. Improved Durability of Electrocatalyst Based on Coating of Carbon Black with Polybenzimidazole and their Application in Polymer Electrolyte Fuel Cells.

    PubMed

    Fujigaya, Tsuyohiko; Hirata, Shinsuke; Berber, Mohamed R; Nakashima, Naotoshi

    2016-06-15

    Improvement of durability of the electrocatalyst has been the key issue to be solved for the practical application of polymer electrolyte membrane fuel cells. One of the promising strategies to improve the durability is to enhance the oxidation stability of the carbon-supporting materials. In this report, we describe in detail the mechanism of the stability improvement of carbon blacks (CBs; Vulcan and Ketjen) by coating with polybenzimidazole (PBI). Nitrogen adsorption experiments reveal that the PBI coating of CBs results in the capping of the gates of the CB-micropores by the PBI. Since the surface of the micropores inside the CBs are inherently highly oxidized, the capping of such pores effectively prevents the penetration of the electrolyte into the pore and works to avoid the further oxidation of interior of the micropore, which is proved by cyclic voltammogram measurements. Above mechanism agrees very well with the dramatic enhancement of the durability of the membrane electrode assembly fabricated using Pt on the PBI-coated CBs as an electrocatalyst compared to the conventional Pt/CB (PBI-non coated) catalyst. PMID:27227977

  19. MoO2 nanoparticles on reduced graphene oxide/polyimide-carbon nanotube film as efficient hydrogen evolution electrocatalyst

    NASA Astrophysics Data System (ADS)

    Li, Xin; Jiang, Yimin; Jia, Lingpu; Wang, Chunming

    2016-02-01

    Hydrogen evolution reaction (HER) through low-cost and earth-abundant electrocatalysts at low overpotentials is a crucial project to clean energy. Molybdenum dioxide/reduced graphene oxide/polyimide-carbon nanotube (MoO2/RGO/PI-CNT) film was synthesized by a simple electrodeposition method as an efficient catalyst for HER. MoO2 nanoparticles with a small size of 10-20 nm uniformly disperse on the RGO surface. The large quantity and small size of MoO2 nanoparticles afford large surface area for HER, greatly enhancing the electrocatalytic performance of MoO2/RGO/PI-CNT film. The HER electrocatalytic property of MoO2/RGO/PI-CNT film in acidic solution is evaluated by linear sweep voltammetry (LSV). MoO2/RGO/PI-CNT film exhibit a high electrocatalytic activity for HER at a small onset overpotential (-110 mV vs RHE) with a high current density (10.0 mA cm-2) and a good stability. The low Tafel slope (68 mV dec-1) reveals the Volmer-Heyrovsky mechanism for HER. The comparison between MoO2/RGO/PI-CNT film and other catalysts indicate that the MoO2/RGO/PI-CNT film had a great performance for HER. This work presents a new thought for the synthesis of MoO2/RGO/PI-CNT film as an efficient HER electrocatalyst.

  20. Heteroatoms ternary-doped porous carbons derived from MOFs as metal-free electrocatalysts for oxygen reduction reaction

    PubMed Central

    Li, Ji-Sen; Li, Shun-Li; Tang, Yu-Jia; Li, Kui; Zhou, Lei; Kong, Ning; Lan, Ya-Qian; Bao, Jian-Chun; Dai, Zhi-Hui

    2014-01-01

    The nitrogen (N), phosphorus (P) and sulphur (S) ternary-doped metal-free porous carbon materials have been successfully synthesized using MOFs as templates (denoted as NPS-C-MOF-5) for oxygen reduction reaction (ORR) for the first time. The influences of porous carbons from carbonizing different MOFs and carbonization temperature on ORR have been systematically investigated. Due to the synergistic effect of N, P and S ternary-doping, the NPS-C-MOF-5 catalyst shows a higher onset potential as a metal-free electrocatalyst for ORR among the currently reported metal-free electrocatalysts, very close to the commercial Pt-C catalyst. In particular, the kinetic limiting current density of NPS-C-MOF-5 catalyst at −0.6 V is up to approximate −11.6 mA cm−2, which is 1.2 times higher than that of the commercial Pt-C catalyst. Furthermore, the outstanding methanol tolerance and excellent long-term stability of NPS-C-MOF-5 are superior to those of the commercial Pt-C catalyst for ORR in alkaline media. PMID:24875253

  1. SrCo(0.9)Ti(0.1)O(3-δ) As a New Electrocatalyst for the Oxygen Evolution Reaction in Alkaline Electrolyte with Stable Performance.

    PubMed

    Su, Chao; Wang, Wei; Chen, Yubo; Yang, Guangming; Xu, Xiaomin; Tadé, Moses O; Shao, Zongping

    2015-08-19

    The development of efficient, inexpensive, and stable electrocatalysts for the oxygen evolution reaction (OER) is critical for many electrochemical energy conversion technologies. The prohibitive price and insufficient stability of the state-of-the-art IrO2 electrocatalyst for the OER inhibits its use in practical devices. Here, SrM0.9Ti0.1O3-δ (M = Co, Fe) perovskites with different B-site transition metal elements were investigated as potentially cheaper OER electrocatalysts. They were prepared through a typical sol-gel route, and their catalytic activities for the OER in alkaline medium were comparatively studied using rotating disk electrodes. Both materials show high initial intrinsic activities in alkaline electrolyte for the OER, comparable to the benchmark perovskite-type electrocatalyst Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF), but SrCo0.9Ti0.1O3-δ (SCT) possessed more operational stability than SrFe0.9Ti0.1O3-δ (SFT), even better than BSCF and IrO2 catalysts. Based on the X-ray photoelectron spectra analysis of the oxidation states of the surface Co/Fe in both SFT and SCT before and after the OER tests, an explanation for their different operational stabilities was proposed by adopting a reported activity descriptor correlated to the eg occupancy of the 3d electron of the surface transition metal cations in the perovskite oxides. The above results indicate that SCT is a promising alternative electrocatalyst for the OER and can be used in electrochemical devices for water oxidation. PMID:26222739

  2. Cobalt Complexes Containing Pendant Amines in the Second Coordination Sphere as Electrocatalysts for H2 Production

    SciTech Connect

    Fang, Ming; Wiedner, Eric S.; Dougherty, William G.; Kassel, W. S.; Liu, Tianbiao L.; DuBois, Daniel L.; Bullock, R. Morris

    2014-10-27

    A series of heteroleptic 17e- cobalt complexes, [CpCoII(PtBu2NPh2)](BF4), [CpC6F5CoII(PtBu2NPh2)](BF4), [CpC5F4NCoII(PtBu2NPh2)](BF4), [where P2tBuN2Ph = 1,5-diphenyl-3,7-di(tert-butyl)-1,5-diaza-3,7-diphosphacyclooctane, CpC6F5 = C5H4(C6F5), and CpC5F4N = C5H4(C5F4N)] were synthesized, and structures of all three were determined by X-ray crystallography. Electrochemical studies showed that the CoIII/II couple of [CpC5F4NCoII(PtBu2NPh2)]+ appears 250 mV positive of the CoIII/II couple of [CpCoII(PtBu2NPh2)] as a result of the strongly electron-withdrawing perfluorpyridyl substituent on the Cp ring. Reduction of these paramagnetic CoII complexes by KC8 led to the diamagnetic 18e- complexes CpICo(PtBu2NPh2), CpC6F5CoI(PtBu2NPh2), CpC5F4NCoI(PtBu2NPh2), which were also characterized by crystallography. Protonation of these neutral CoI complexes led to the cobalt hydrides [CpCoIII(PtBu2NPh2)H](BF4), [CpC6F5CoIII(PtBu2NPh2)H](BF4), and [CpC5F4NCoIII(PtBu2NPh2)H](BF4). The cobalt hydride with the most electron-withdrawing Cp ligand, [CpC5F4NCoIII(PtBu2NPh2)H]+ is an electrocatalyst for production of H2 using 4-MeOC6H4NH3BF4 (pKaMeCN = 11.86) with a turnover frequency of 350 s-1 and an overpotential of 0.75 V. Experimental measurement of thermochemical data provided further insights into the thermodynamics of H2 elimination. This research was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences. Pacific Northwest National Laboratory is operated by Battelle for the U.S. Department of Energy.

  3. Elucidation of adsorption processes at the surface of Pt(331) model electrocatalysts in acidic aqueous media.

    PubMed

    Pohl, Marcus D; Colic, Viktor; Scieszka, Daniel; Bandarenka, Aliaksandr S

    2016-04-20

    The Pt(331) surface has long been known to be the most active pure metal electrocatalyst for the oxygen reduction reaction (ORR) in acidic media. Its activity is often higher than those known for the Pt-based alloys towards ORR, being comparable with the most active Pt3Ni(111), Pt3Y or Pt5Gd, and being more active than e.g. polycrystalline Pt3Ni. Multiple active sites at this surface offer adsorption energies which are close to the optimal binding energy with respect to the main ORR intermediates; nevertheless, the exact location of these sites is still not clear. Taking into account the unique surface geometry of Pt(331), some adsorbates (including some oxygenated ORR-intermediates) should also contribute to the electronic structure of the neighbouring catalytic centres. However, the experimental elucidation of the specific adsorption of oxygenated species at this surface appears to be a non-trivial task. Such information holds the keys to the understanding of the high activity of this material and would enable the rational design of nanostructured ORR catalysts even without alloying. In this work, the electrified Pt(331)/electrolyte interface has been characterised using cyclic voltammetry (CV) combined with potentiodynamic electrochemical impedance spectroscopy (PDEIS) in 0.1 M HClO4 solutions. The systems were studied in the potential region between 0.05 V and 1.0 V vs. RHE, where the adsorption of *H, *OH and *O species is possible in both O2-free and O2-saturated electrolytes. Our CV and PDEIS results support the hypothesis that in contrast to Pt(111), many Pt(331) surface sites are likely blocked by *O species at the polymer electrolyte membrane fuel cell benchmark potential of 0.9 V (RHE). We propose a model illustrated by simplified adsorbate structures at different electrode potentials, which is, however, able to explain the voltammetric and impedance data, and which is in good agreement with previously reported electrocatalytic measurements. PMID

  4. Oxygen electrode bifunctional electrocatalyst NiCo2O4 spinel

    NASA Technical Reports Server (NTRS)

    Fielder, William L.; Singer, Joseph

    1988-01-01

    A significant increase in energy density may be possible if a two-unit alkaline regenerative H2-O2 fuel cell is replaced with a single-unit system that uses passive means for H2O transfer and thermal control. For this single-unit system, new electrocatalysts for the O2 electrode will be required which are not only bifunctionally active but also chemically and electrochemically stable between the voltage range of about 0.7 and 1.5 V. NiCo2O4 spinel is reported to have certain characteristics that make it useful for a study of electrode fabrication techniques. High surface area NiCo2O4 powder was fabricated into unsupported, bifunctional, PTFE-bonded, porous gas fuel cell electrodes by commercial sources using varying PTFE contents and sintering temperatures. The object of this study is to measure the bifunctional activities of these electrodes and to observe what performance differences might result from different commercial electrode fabricators. O2 evolution and O2 reduction data were obtained at 80 C (31 percent KOH). An irreversible reaction (i.e., aging) occurred during O2 evolution at potentials greater than about 1.5 V. Anodic Tafel slopes of 0.06 and 0.12 V/decade were obtained for the aged electrodes. Within the range of 15 to 25 percent, the PTFE content was not a critical parameter for optimizing the electrode for O2 evolution activity. Sintering temperatures between 300 and 340 C may be adequate but heating at 275 C may not be sufficient to properly sinter the PTFE-NiCo2O4 mixture. Electrode disintegration was observed during O2 reduction. Transport of O2 to the NiCo2O4 surface became prohibitive at greater than about -0.02 A/sq cm. Cathodic Tafel slopes of -0.6 and -0.12 V/decade were assumed for the O2 reduction process. A PTFE content of 25 percent (or greater) appears to be preferable for sintering the PTFE-NiCo2O4 mixture.

  5. Hydrothermal transformation of dried grass into graphitic carbon-based high performance electrocatalyst for oxygen reduction reaction.

    PubMed

    Zhang, Haimin; Wang, Yun; Wang, Dan; Li, Yibing; Liu, Xiaolu; Liu, Porun; Yang, Huagui; An, Taicheng; Tang, Zhiyong; Zhao, Huijun

    2014-08-27

    In this work, we present a low cost and environmentally benign hydrothermal method using dried grass as the sole starting material without any synthetic chemicals to directly produce high quality nitrogen-doped carbon nanodot/nanosheet aggregates (N-CNAs), achieving a high yield of 25.2%. The fabricated N-CNAs possess an N/C atomic ratio of 3.41%, consist of three typed of doped N at a ratio of 2.6 (pyridinic):1.7 (pyrrolic):1 (graphitic). The experimental results reveal that for oxygen reduction reaction (ORR), the performance of N-CNAs, in terms of electrocatalytic activity, stability and resistance to crossover effects, is better or comparable to the commercial Pt/C electrocatalyst. The theoretical studies further indicate that the doped pyridinic-N plays a key role for N-CNAs' excellent four-electron ORR electrocatalytic activity. PMID:24729520

  6. Substrate Selection for Fundamental Studies of Electrocatalysts and Photoelectrodes: Inert Potential Windows in Acidic, Neutral, and Basic Electrolyte

    PubMed Central

    Gorlin, Yelena; Jaramillo, Thomas F.

    2014-01-01

    The selection of an appropriate substrate is an important initial step for many studies of electrochemically active materials. In order to help researchers with the substrate selection process, we employ a consistent experimental methodology to evaluate the electrochemical reactivity and stability of seven potential substrate materials for electrocatalyst and photoelectrode evaluation. Using cyclic voltammetry with a progressively increased scan range, we characterize three transparent conducting oxides (indium tin oxide, fluorine-doped tin oxide, and aluminum-doped zinc oxide) and four opaque conductors (gold, stainless steel 304, glassy carbon, and highly oriented pyrolytic graphite) in three different electrolytes (sulfuric acid, sodium acetate, and sodium hydroxide). We determine the inert potential window for each substrate/electrolyte combination and make recommendations about which materials may be most suitable for application under different experimental conditions. Furthermore, the testing methodology provides a framework for other researchers to evaluate and report the baseline activity of other substrates of interest to the broader community. PMID:25357131

  7. Structural Origin of the Activity in Mn3O4-Graphene Oxide Hybrid Electrocatalysts for the Oxygen Reduction Reaction.

    PubMed

    Wu, Kuang-Hsu; Zeng, Qingcong; Zhang, Bingsen; Leng, Xue; Su, Dang-Sheng; Gentle, Ian R; Wang, Da-Wei

    2015-10-12

    Non-precious metal oxide/carbon hybrid electrocatalysts are of increasing importance for the oxygen reduction reaction (ORR). A synergistic effect is commonly used to explain the superior ORR activity exerted by metal oxide/nanocarbon hybrids, and this effect is attributed to covalently coupled interfaces between the two materials. However, the origin of the high activity, the structure, and the electrocatalytic nature of the interface remain unclear. By combining X-ray photoelectron spectroscopy with synchrotron far-infrared spectroscopy, we resolved the interface structure between spinel manganese oxide nanocrystals and graphene oxide nanoribbons, and the role of this interface in the promoted ORR. Moreover, we demonstrated the excellent ORR activity by a functional synergism of the hybrid constituents through a series of comparative electrochemical experiments. PMID:26448527

  8. A hybrid-assembly approach towards nitrogen-doped graphene aerogel supported cobalt nanoparticles as high performance oxygen reduction electrocatalysts.

    PubMed

    Liu, Ruili; Jin, Yeqing; Xu, Peimin; Xing, Xia; Yang, Yuxing; Wu, Dongqing

    2016-02-15

    As a novel electrocatalyst for oxygen reduction reaction (ORR), nitrogen-doped graphene aerogel supported cobalt nanoparticles (Co-NGA) is archived by a hybrid-assembly of graphene oxide (GO), o-phthalonitrile and cobalt acetate and the following thermal treatment. The hybrid-assembly process successfully combines the ionic assembly of GO sheets and Co ions with the coordination between o-phthalonitrile and Co ions, which can be converted to nitrogen doped carbon and Co nanoparticles in the pyrolysis process under nitrogen flow. Remarkable features of Co-NGA including the macroporous graphene scaffolds, high surface area, and N/Co-doping effect can lead to a high catalytic efficiency for ORR. As the results, the composites pyrolyzed at 600°C (Co-NGA600) shows excellent electrocatalytic activities and kinetics for ORR in basic media, which are comparable with those of Pt/C catalyst, together with superior durability. PMID:26609926

  9. Cobalt oxide and nitride particles supported on mesoporous carbons as composite electrocatalysts for dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Chen, Ming; Shao, Leng-Leng; Gao, Ze-Min; Ren, Tie-Zhen; Yuan, Zhong-Yong

    2015-07-01

    The composite electrocatalysts of cobalt oxide/mesoporous carbon and cobalt nitride/mesoporous carbon are synthesized via a convenient oxidation and subsequent ammonia nitridation of cobalt particles-incorporated mesoporous carbon, respectively. The cobalt oxide and nitride particles are uniformly imbedded in mesoporous carbon matrix, forming the unique composites with high surface area and mesopore architecture, and the resultant composites are evaluated as counter electrode materials, exhibiting good catalytic activity for the reduction of triiodide. The composites of cobalt nitride and mesoporous carbon are superior to the counterparts of cobalt oxide and mesoporous carbon in catalyzing the triiodide reduction, and the dye-sensitized solar cell with the composites achieves an optimum power conversion efficiency of 5.26%, which is comparable to the one based on the conventional Pt counter electrode (4.88%).

  10. Stability and spinodal decomposition of the solid-solution phase in the ruthenium-cerium-oxide electro-catalyst.

    PubMed

    Li, Yanmei; Wang, Xin; Shao, Yanqun; Tang, Dian; Wu, Bo; Tang, Zhongzhi; Lin, Wei

    2015-01-14

    The phase diagram of Ru-Ce-O was calculated by a combination of ab initio density functional theory and thermodynamic calculations. The phase diagram indicates that the solubility between ruthenium oxide and cerium oxide is very low at temperatures below 1100 K. Solid solution phases, if existing under normal experimental conditions, are metastable and subject to a quasi-spinodal decomposition to form a mixture of a Ru-rich rutile oxide phase and a Ce-rich fluorite oxide phase. To study the spinodal decomposition of Ru-Ce-O, Ru0.6Ce0.4O2 samples were prepared at 280 °C and 450 °C. XRD and in situ TEM characterization provide proof of the quasi-spinodal decomposition of Ru0.6Ce0.4O2. The present study provides a fundamental reference for the phase design of the Ru-Ce-O electro-catalyst. PMID:25418197

  11. Enzyme Design From the Bottom Up: An Active Nickel Electrocatalyst with a Structured Peptide Outer Coordination Sphere

    SciTech Connect

    Reback, Matthew L.; Buchko, Garry W.; Kier, Brandon L.; Ginovska-Pangovska, Bojana; Xiong, Yijia; Lense, Sheri; Hou, Jianbo; Roberts, John A.; Sorensen, Christina M.; Raugei, Simone; Squier, Thomas C.; Shaw, Wendy J.

    2014-02-03

    Functional, peptide-containing metal complexes with a well-defined peptide structure have the potential to enhance molecular catalysts via an enzyme-like outer coordination sphere. Here, we report the synthesis and characterization of an active, peptide-based metal complex built upon the well characterized hydrogen production catalyst, Ni(PPh2NPh)2. The incorporated peptide maintains its B-hairpin structure when appended to the metal core, and the electrocatalytic activity of the peptide-based metal complex (~100,000 s-1) is fully retained. The combination of an active molecular catalyst with a structured peptide outer coordination sphere provides a scaffold that permits the incorporation of features of an enzyme-like outer-coordination sphere necessary to create molecular electrocatalysts with en-hanced functionality.

  12. Pt nanoparticle-dispersed graphene-wrapped MWNT composites as oxygen reduction reaction electrocatalyst in proton exchange membrane fuel cell.

    PubMed

    Aravind, S S Jyothirmayee; Ramaprabhu, Sundara

    2012-08-01

    Chemical and electrical synergies between graphite oxide and multiwalled carbon nanotube (MWNT) for processing graphene wrapped-MWNT hybrids has been realized by chemical vapor deposition without any chemical functionalization. Potential of the hybrid composites have been demonstrated by employing them as electrocatalyst supports in proton exchange membrane fuel cells. The defects present in the polyelectrolyte, which have been wrapped over highly dispersed MWNT, act as anchoring sites for the homogeneous deposition of platinum nanoparticles. Single-cell proton exchange membrane fuel cells show that the power density of the hybrid composite-based fuel cells is higher compared to the pure catalyst-support-based fuel cells, because of enhanced electrochemical reactivity and good surface area of the nanocomposites. PMID:22850438

  13. Pulse electrodeposited nickel-indium tin oxide nanocomposite as an electrocatalyst for non-enzymatic glucose sensing.

    PubMed

    Sivasakthi, P; Ramesh Bapu, G N K; Chandrasekaran, Maruthai

    2016-01-01

    Nickel and nickel-ITO nanocomposite on mild steel substrate were prepared by pulse electrodeposition method from nickel sulphamate electrolyte and were examined as electrocatalysts for non-enzymatic glucose sensing. The surface morphology, chemical composition, preferred orientation and oxidation states of the nickel metal ion in the deposits were characterized by SEM, EDAX, XRD and XPS. Electrochemical sensing of glucose was studied by cyclic voltammetry and amperometry. The modified Ni-ITO nanocomposite electrode showed higher electrocatalytic activity for the oxidation of glucose in alkaline medium and exhibited a linear range from 0.02 to 3.00 mM with a limit of detection 3.74 μM at a signal-to-noise ratio of 3. The higher selectivity, longer stability and better reproducibility of this electrode compared to nickel in the sensing of glucose are pointers for exploitation in practical clinical applications. PMID:26478372

  14. Solid-state chemistry-enabled scalable production of octahedral Pt-Ni alloy electrocatalyst for oxygen reduction reaction.

    PubMed

    Zhang, Changlin; Hwang, Sang Youp; Trout, Alexis; Peng, Zhenmeng

    2014-06-01

    Although octahedral Pt-Ni alloy nanoparticles possess an excelling property in oxygen reduction reaction (ORR) and are of great potential as an electrocatalyst for polymer electrolyte membrane fuel cells (PEMFCs), mass production of the materials at low cost remains a big challenge. By combining the advantages of both solid-state chemistry and wet synthetic chemistry, we developed one scalable, surfactant-free, and cost-effective method for producing octahedral Pt-Ni alloy nanoparticles on carbon support. The octahedral Pt-Ni samples were prepared with different compositions and studied for the ORR property. They exhibit a much improved reaction activity compared to the commercial catalyst. The experiments demonstrate an innovative strategy for preparing shaped metal nanoparticles and make significant progress in the ORR catalyst research. PMID:24827592

  15. FeOOH/Co/FeOOH Hybrid Nanotube Arrays as High-Performance Electrocatalysts for the Oxygen Evolution Reaction.

    PubMed

    Feng, Jin-Xian; Xu, Han; Dong, Yu-Tao; Ye, Sheng-Hua; Tong, Ye-Xiang; Li, Gao-Ren

    2016-03-01

    Herein, we developed FeOOH/Co/FeOOH hybrid nanotube arrays (HNTAs) supported on Ni foams for oxygen evolution reaction (OER). The inner Co metal cores serve as highly conductive layers to provide reliable electronic transmission, and can overcome the poor electrical conductivity of FeOOH efficiently. DFT calculations demonstrate the strong electronic interactions between Co and FeOOH in the FeOOH/Co/FeOOH HNTAs, and the hybrid structure can lower the energy barriers of intermediates and thus promote the catalytic reactions. The FeOOH/Co/FeOOH HNTAs exhibit high electrocatalytic performance for OER, such as low onset potential, small Tafel slope, and excellent long-term durability, and they are promising electrocatalysts for OER in alkaline solution. PMID:26879125

  16. Nanoparticle-Stacked Porous Nickel-Iron Nitride Nanosheet: A Highly Efficient Bifunctional Electrocatalyst for Overall Water Splitting.

    PubMed

    Wang, Yanyong; Xie, Chao; Liu, Dongdong; Huang, Xiaobing; Huo, Jia; Wang, Shuangyin

    2016-07-27

    Nanoparticle-stacked porous Ni3FeN nanosheets were synthesized through a simple nitridation reaction of the corresponding LDHs. The nanosheet is composed of stacked nanoparticles with more active sites exposed for electrocatalytic reactions. Thus, it exhibited excellent oxygen evolution reaction performance having an extremely low overpotential of 223 mV at 10 mA/cm(2) and hydrogen evolution reaction property with a very low overpotential of 45 mV at 10 mA/cm(2). This electrocatalyst as bifunctional electrodes is used to overall water splitting in alkaline media, showing a high performance with 10 mA/cm(2) at a cell voltage of 1.495 V. PMID:27348348

  17. Platinum-modified covalent triazine frameworks hybridized with carbon nanoparticles as methanol-tolerant oxygen reduction electrocatalysts.

    PubMed

    Kamiya, Kazuhide; Kamai, Ryo; Hashimoto, Kazuhito; Nakanishi, Shuji

    2014-01-01

    Covalent triazine frameworks, which are crosslinked porous polymers with two-dimensional molecular structures, are promising materials for heterogeneous catalysts. However, the application of the frameworks as electrocatalysts has not been achieved to date because of their poor electrical conductivity. Here we report that platinum-modified covalent triazine frameworks hybridized with conductive carbon nanoparticles are successfully synthesized by introducing carbon nanoparticles during the polymerization process of covalent triazine frameworks. The resulting materials exhibit clear electrocatalytic activity for oxygen reduction reactions in acidic solutions. More interestingly, the platinum-modified covalent triazine frameworks show almost no activity for methanol oxidation, in contrast to commercial carbon-supported platinum. Thus, platinum-modified covalent triazine frameworks hybridized with carbon nanoparticles exhibit selective activity for oxygen reduction reactions even in the presence of high concentrations of methanol, which indicates potential utility as a cathode catalyst in direct methanol fuel cells. PMID:25242214

  18. Electrodeposited Co-doped NiSe2 nanoparticles film: a good electrocatalyst for efficient water splitting.

    PubMed

    Liu, Tingting; Asiri, Abdullah M; Sun, Xuping

    2016-02-21

    In this communication, we report that a Co-doped NiSe2 nanoparticles film electrodeposited on a conductive Ti plate (Co0.13Ni0.87Se2/Ti) behaves as a robust electrocatalyst for both HER and OER in strongly basic media, with good activity over a NiSe2/Ti counterpart. This Co0.13Ni0.87Se2/Ti catalytic electrode delivers 10 mA cm(-2) at an overpotential of 64 mV for HER and 100 mA cm(-2) at an overpotential of 320 mV for OER in 1.0 M KOH. A voltage of only 1.62 V is required to drive 10 mA cm(-2) for the two-electrode alkaline water electrolyzer using Co0.13Ni0.87Se2/Ti as an anode and cathode. PMID:26866797

  19. Platinum-modified covalent triazine frameworks hybridized with carbon nanoparticles as methanol-tolerant oxygen reduction electrocatalysts

    PubMed Central

    Kamiya, Kazuhide; Kamai, Ryo; Hashimoto, Kazuhito; Nakanishi, Shuji

    2014-01-01

    Covalent triazine frameworks, which are crosslinked porous polymers with two-dimensional molecular structures, are promising materials for heterogeneous catalysts. However, the application of the frameworks as electrocatalysts has not been achieved to date because of their poor electrical conductivity. Here we report that platinum-modified covalent triazine frameworks hybridized with conductive carbon nanoparticles are successfully synthesized by introducing carbon nanoparticles during the polymerization process of covalent triazine frameworks. The resulting materials exhibit clear electrocatalytic activity for oxygen reduction reactions in acidic solutions. More interestingly, the platinum-modified covalent triazine frameworks show almost no activity for methanol oxidation, in contrast to commercial carbon-supported platinum. Thus, platinum-modified covalent triazine frameworks hybridized with carbon nanoparticles exhibit selective activity for oxygen reduction reactions even in the presence of high concentrations of methanol, which indicates potential utility as a cathode catalyst in direct methanol fuel cells. PMID:25242214

  20. Development of efficient electrocatalysts via molecular hybridization of NiMn layered double hydroxide nanosheets and graphene

    NASA Astrophysics Data System (ADS)

    Ma, Wei; Ma, Renzhi; Wu, Jinghua; Sun, Pengzhan; Liu, Xiaohe; Zhou, Kechao; Sasaki, Takayoshi

    2016-05-01

    Ni2+Mn3+ layered double hydroxide (LDH) nanoplatelets have been hydrothermally synthesized in a homogeneous precipitation of mixed Ni2+/Mn2+ salts at a molar ratio of 2 : 1 via the hydrolysis of hexamethylenetetramine (HMT) and in situ oxidation with H2O2. After anion-exchange, NiMn LDH was exfoliated into unilamellar nanosheets. Subsequent flocculation of NiMn LDH nanosheets with (reduced) graphene oxide (GO/rGO) into superlattice composites was achieved and further tested as electrocatalysts for oxygen evolution reaction (OER). The face-to-face heteroassembly of NiMn LDH nanosheets with conductive rGO at an alternating sequence resulted in a small overpotential of 0.26 V and a Tafel slope of 46 mV per decade, which is much superior to as-exfoliated nanosheets. The analyses of electrochemical activity surface area (ECSA) and impedance spectra clearly indicated that the superlattice structure was ideal in facilitating the migration/transfer of the charge and reactants, revealing the electrochemical energetics and mechanism behind the synergistic effect arising from molecular hybridization. The proof of concept toward total water splitting using the newly developed hybrid electrocatalyst was demonstrated by an electrolysis cell powered by a single AA battery.Ni2+Mn3+ layered double hydroxide (LDH) nanoplatelets have been hydrothermally synthesized in a homogeneous precipitation of mixed Ni2+/Mn2+ salts at a molar ratio of 2 : 1 via the hydrolysis of hexamethylenetetramine (HMT) and in situ oxidation with H2O2. After anion-exchange, NiMn LDH was exfoliated into unilamellar nanosheets. Subsequent flocculation of NiMn LDH nanosheets with (reduced) graphene oxide (GO/rGO) into superlattice composites was achieved and further tested as electrocatalysts for oxygen evolution reaction (OER). The face-to-face heteroassembly of NiMn LDH nanosheets with conductive rGO at an alternating sequence resulted in a small overpotential of 0.26 V and a Tafel slope of 46 mV per decade

  1. Platinum-modified covalent triazine frameworks hybridized with carbon nanoparticles as methanol-tolerant oxygen reduction electrocatalysts

    NASA Astrophysics Data System (ADS)

    Kamiya, Kazuhide; Kamai, Ryo; Hashimoto, Kazuhito; Nakanishi, Shuji

    2014-09-01

    Covalent triazine frameworks, which are crosslinked porous polymers with two-dimensional molecular structures, are promising materials for heterogeneous catalysts. However, the application of the frameworks as electrocatalysts has not been achieved to date because of their poor electrical conductivity. Here we report that platinum-modified covalent triazine frameworks hybridized with conductive carbon nanoparticles are successfully synthesized by introducing carbon nanoparticles during the polymerization process of covalent triazine frameworks. The resulting materials exhibit clear electrocatalytic activity for oxygen reduction reactions in acidic solutions. More interestingly, the platinum-modified covalent triazine frameworks show almost no activity for methanol oxidation, in contrast to commercial carbon-supported platinum. Thus, platinum-modified covalent triazine frameworks hybridized with carbon nanoparticles exhibit selective activity for oxygen reduction reactions even in the presence of high concentrations of methanol, which indicates potential utility as a cathode catalyst in direct methanol fuel cells.

  2. Density functional theory study of oxygen reduction reaction on Pt/Pd3Al(111) alloy electrocatalyst.

    PubMed

    Xiao, B B; Jiang, X B; Jiang, Q

    2016-05-25

    Developing efficient catalysts for the oxygen reduction reaction (ORR) to reduce cathode Pt loading without sacrificing the performance has been under intensive research. Herein, by using density functional theory calculations, the activity and stability of a Pt monolayer supported on Pd3Al(111) as the ORR catalyst have been systematically studied. The simulations demonstrate that due to alloying, the ORR intermediates bind weakly on Pt/Pd3Al(111) with optimal adsorption energy of O and OH. By considering the elemental ORR steps, the ORR mechanism is predicted to be an OOH dissociation mechanism. The rate determining step is OOH dissociation with a reaction barrier of 0.37 eV, lower than the corresponding value on Pt/Pt3Al(111) and Pt(111), indicating the superior activity of Pt/Pd3Al(111). Even considering the unfeasible H adsorption under high potential, the ORR mechanism on Pt/Pd3Al(111) would proceed via O2 hydration, OOH hydration, H2O formation, and H2O desorption, indicating a good ORR electrocatalyst. Furthermore, stability was evaluated by calculating the alloy formation energy and the electrochemical potential shift of surface Pt dissolution. The exceptionally negative alloy formation energy of Pd3Al and the positive dissolution potential shift of the surface Pt atoms show the enhanced durability of Pt/Pd3Al(111). The improved activity, in combination with its enhanced stability, makes the novel ternary alloy electrocatalyst very promising for development of new cathode catalysts for fuel cells. PMID:27167779

  3. Manganese Electrocatalysts with Bulky Bipyridine Ligands: Utilizing Lewis Acids To Promote Carbon Dioxide Reduction at Low Overpotentials.

    PubMed

    Sampson, Matthew D; Kubiak, Clifford P

    2016-02-01

    Earth-abundant manganese bipyridine (bpy) complexes are well-established molecular electrocatalysts for proton-coupled carbon dioxide (CO2) reduction to carbon monoxide (CO). Recently, a bulky bipyridine ligand, 6,6'-dimesityl-2,2'-bipyridine (mesbpy), was utilized to significantly lower the potential necessary to access the doubly reduced states of these manganese catalysts by eliminating their ability to dimerize after one-electron reduction. Although this Mn mesbpy catalyst binds CO2 at very low potentials, reduction of a resulting Mn(I)-COOH complex at significantly more negative potentials is required to achieve fast catalytic rates. Without reduction of Mn(I)-COOH, catalysis occurs slowly via a alternate catalytic pathway-protonation of Mn(I)-COOH to form a cationic tetracarbonyl complex. We report the use of Lewis acids, specifically Mg(2+) cations, to significantly increase the rate of catalysis (by over 10-fold) at these low overpotentials (i.e., the same potential as CO2 binding). Reduction of CO2 occurs at one of the lowest overpotentials ever reported for molecular electrocatalysts (η = 0.3-0.45 V). With Mg(2+), catalysis proceeds via a reductive disproportionation reaction of 2CO2 + 2e(-) → CO and CO3(2-). Insights into the catalytic mechanism were gained by using variable concentration cyclic voltammetry, infrared spectroelectrochemistry, and bulk electrolysis studies. The catalytic Tafel behavior (log turnover frequency vs overpotential relationship) of [Mn(mesbpy)(CO)3(MeCN)](OTf) with added Mg(2+) is compared with those of other commonly studied CO2 reduction catalysts. PMID:26745814

  4. Combined Photoemission Spectroscopy and Electrochemical Study of a Mixture of (Oxy)carbides as Potential Innovative Supports and Electrocatalysts.

    PubMed

    Calvillo, Laura; Valero-Vidal, Carlos; Agnoli, Stefano; Sezen, Hikmet; Rüdiger, Celine; Kunze-Liebhäuser, Julia; Granozzi, Gaetano

    2016-08-01

    Active and stable non-noble metal materials, able to substitute Pt as catalyst or to reduce the Pt amount, are vitally important for the extended commercialization of energy conversion technologies, such as fuel cells and electrolyzers. Here, we report a fundamental study of nonstoichiometric tungsten carbide (WxC) and its interaction with titanium oxycarbide (TiOxCy) under electrochemical working conditions. In particular, the electrochemical activity and stability of the WxC/TiOxCy system toward the ethanol electrooxidation reaction (EOR) and hydrogen evolution reaction (HER) are investigated. The chemical changes caused by the applied potential are established by combining photoemission spectroscopy and electrochemistry. WxC is not active toward the ethanol electrooxidation reaction at room temperature but it is highly stable under these conditions thanks to the formation of a passive thin film on the surface, consisting mainly of WO2 and W2O5, which prevents the full oxidation of WxC. In addition, WxC is able to adsorb ethanol, forming ethoxy groups on the surface, which constitutes the first step for the ethanol oxidation. The interaction between WxC and TiOxCy plays an important role in the electrochemical stability of WxC since specific orientations of the substrate are able to stabilize WxC and prevent its corrosion. The beneficial interaction with the substrate and the specific surface chemistry makes tungsten carbide a good electrocatalyst support or cocatalyst for direct ethanol fuel cells. However, WxC is active toward the HER and chemically stable under hydrogen reduction conditions, since no changes in the chemical composition or dissolution of the film are observed. This makes tungsten carbide a good candidate as electrocatalyst support or cocatalyst for the electrochemical production of hydrogen. PMID:27399154

  5. Platinum-monolayer Electrocatalysts: Palladium Interlayer on IrCo Alloy Core Improves Activity in Oxygen-reduction Reaction

    SciTech Connect

    Gong, K.; Chen, W.-F.; Sasaki, K.; Su, D.; Vukmirovic, M.B.; Zhou, W.; Izzo, E.L.; Perez-Acosta, C.; Hirunsit, P.; Balbuena, P.B.; Adzic, R.R.

    2010-11-15

    We describe the synthesis and electrocatalytic properties of a new low-Pt electrocatalyst consisting of an IrCo core, a Pd interlayer, and a surface Pt monolayer, emphasizing the interlayer's role in improving electrocatalytic activity for the oxygen-reduction reaction on Pt in HClO{sub 4} solution. We prepared the IrCo alloys by decomposing, at 800 C, hexacyanometalate, KCoIr(CN){sub 6}, adsorbed on the carbon surfaces. The synthesis of Ir{sub 3}Co/C involved heating a mix of metal salts and carbon in hydrogen at 500 C. Thereafter, we placed a palladium and/or platinum monolayer on them via the galvanic displacement of an underpotentially deposited copper monolayer. The electrocatalysts were characterized using structural- and electrochemical-techniques. For PtML/PdML/IrCo/C, we observed a Pt mass activity of 1.18 A/mg{sub (Pt)} and the platinum-group-metals mass of 0.16 A/mg{sub (Pt, Pd, Ir)}. In comparison, without a Pd interlayer, i.e., Pt{sub ML}/IrCo/C, the activities of 0.15 A/mg{sub (Pt)} and 0.036 A/mg{sub (Pt, Pd, Ir)} were considerably lower. We consider that the palladium interlayer plays an essential role in achieving high catalytic activity by adjusting the electronic interaction of the platinum monolayer with the IrCo core, so that it accelerates the kinetics of adsorption and desorption of the intermediates of oxygen reduction. A similar trend was observed for Pt{sub ML}/Pd{sub ML} and Pt{sub ML} deposited on Ir{sub 3}Co/C alloy core. We used density functional theory to interpret the observed phenomena.

  6. Nanosized IrxRu1-xO2 electrocatalysts for oxygen evolution reaction in proton exchange membrane water electrolyzer

    NASA Astrophysics Data System (ADS)

    Hanh Pham, Hong; Nguyen, Ngoc Phong; Linh Do, Chi; Thang Le, Ba

    2015-01-01

    Normally in proton exchange membrane water electrolysis (PEMWE), the anode has the largest overpotential at typical operating current densities. By development of the electrocatalytic material used for the oxygen evolving electrode, great improvements in efficiency can be performed. In electrochemistry, rare metallic oxides RuO2 and IrO2 exhibit the best catalytic properties for the oxygen evolution reaction (OER) in acid electrolytes compared to other noble metals. RuO2 is the most active catalyst and IrO2 is the most stable catalyst. An oxide containing both elements is therefore expected to be a good catalyst for the OER. In this study IrxRu1-xO2 nanosized powder electrocatalysts for oxygen evolution reaction is synthesized by hydrolysis method. Cyclic voltammetry, anodic polarization and galvanostatic measurements were conducted in solution of 0.5 M H2SO4 to investigate electrocatalytic behavior and stability of the electrocatalyst. The mechanisms of the thermal decomposition process of RuCl3.nH2O and IrCl3.mH2O precursors to form oxide powders were studied by means of thermal gravity analysis (TGA). X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used analysis for determination of the crystallographic structure, morphology and catalysts particle size. Based on the given results, the IrxRu1-xO2 (x = 0.5 0.7) compounds were found to be more active than pure IrO2 and more stable than pure RuO2.

  7. Electrodeposited Co-doped NiSe2 nanoparticles film: a good electrocatalyst for efficient water splitting

    NASA Astrophysics Data System (ADS)

    Liu, Tingting; Asiri, Abdullah M.; Sun, Xuping

    2016-02-01

    In this communication, we report that a Co-doped NiSe2 nanoparticles film electrodeposited on a conductive Ti plate (Co0.13Ni0.87Se2/Ti) behaves as a robust electrocatalyst for both HER and OER in strongly basic media, with good activity over a NiSe2/Ti counterpart. This Co0.13Ni0.87Se2/Ti catalytic electrode delivers 10 mA cm-2 at an overpotential of 64 mV for HER and 100 mA cm-2 at an overpotential of 320 mV for OER in 1.0 M KOH. A voltage of only 1.62 V is required to drive 10 mA cm-2 for the two-electrode alkaline water electrolyzer using Co0.13Ni0.87Se2/Ti as an anode and cathode.In this communication, we report that a Co-doped NiSe2 nanoparticles film electrodeposited on a conductive Ti plate (Co0.13Ni0.87Se2/Ti) behaves as a robust electrocatalyst for both HER and OER in strongly basic media, with good activity over a NiSe2/Ti counterpart. This Co0.13Ni0.87Se2/Ti catalytic electrode delivers 10 mA cm-2 at an overpotential of 64 mV for HER and 100 mA cm-2 at an overpotential of 320 mV for OER in 1.0 M KOH. A voltage of only 1.62 V is required to drive 10 mA cm-2 for the two-electrode alkaline water electrolyzer using Co0.13Ni0.87Se2/Ti as an anode and cathode. Electronic supplementary information (ESI) available: Experimental section and supplementary figures. See DOI: 10.1039/c5nr07170d

  8. Titanium Dioxide-Grafted Copper Complexes: High-Performance Electrocatalysts for the Oxygen Reduction Reaction in Alkaline Media.

    PubMed

    Wang, Fei-Fei; Wei, Ping-Jie; Yu, Guo-Qiang; Liu, Jin-Gang

    2016-01-01

    The sluggish kinetics of the oxygen reduction reaction (ORR) at the cathodes of fuel cells significantly hampers fuel cell performance. Therefore, the development of high-performance, non-precious-metal catalysts as alternatives to noble metal Pt-based ORR electrocatalysts is highly desirable for the large-scale commercialization of fuel cells. TiO2 -grafted copper complexes deposited on multiwalled carbon nanotubes (CNTs) form stable and efficient electrocatalysts for the ORR. The optimized catalyst composite CNTs@TiO2 -ZA-[Cu(phen${{^{{\\rm NO}{_{2}}}}}$)(BTC)] shows surprisingly high selectivity for the 4 e(-) reduction of O2 to water (approximately 97 %) in alkaline solution with an onset potential of 0.988 V vs. RHE, and demonstrates superior stability and excellent tolerance for the methanol crossover effect in comparison to a commercial Pt/C catalyst. The copper complexes were grafted onto the surface of TiO2 through coordination of an imidazole-containing ligand, zoledronic acid (ZA), which binds to TiO2 through its bis-phosphoric acid anchoring group. Rational optimization of the copper catalyst's ORR performance was achieved by using an electron-deficient ligand, 5-nitro-1,10-phenanthroline (phen${{^{{\\rm NO}{_{2}}}}}$), and bridging benzene-1,3,5-tricarboxylate (BTC). This facile approach to the assembly of copper catalysts on TiO2 with rationally tuned ORR activity will have significant implications for the development of high-performance, non-precious-metal ORR catalysts. PMID:26602327

  9. Shewanella-mediated biosynthesis of manganese oxide micro-/nanocubes as efficient electrocatalysts for the oxygen reduction reaction.

    PubMed

    Jiang, Congcong; Guo, Zhaoyan; Zhu, Ying; Liu, Huan; Wan, Meixiang; Jiang, Lei

    2015-01-01

    Developing efficient electrocatalysts for the oxygen reduction reaction (ORR) is critical for promoting the widespread application of fuel cells and metal-air batteries. Here, we develop a biological low-cost, ecofriendly method for the synthesis of Mn2 O3 micro-/nanocubes by calcination of MnCO3 precursors in an oxygen atmosphere. Microcubic MnCO3 precursors with an edge length of 2.5 μm were fabricated by dissimilatory metal-reducing Shewanella loihica PV-4 in the presence of MnO4 (-) as the sole electron acceptor under anaerobic conditions. After calcining the MnCO3 precursors at 500 and 700 °C, porous Mn2 O3 -500 and Mn2 O3 -700 also showed microcubic morphology, while their edge lengths decreased to 1.8 μm due to thermal decomposition. Moreover, the surfaces of the Mn2 O3 microcubes were covered by granular nanoparticles with average diameters in the range of 18-202 nm, depending on the calcination temperatures. Electrochemical measurements demonstrated that the porous Mn2 O3 -500 micro-/nanocubes exhibit promising catalytic activity towards the ORR in an alkaline medium, which should be due to a synergistic effect of the overlapping molecular orbitals of oxygen/manganese and the hierarchically porous structures that are favorable for oxygen absorption. Moreover, these Mn2 O3 micro-/nanocubes possess better stability than commercial Pt/C catalysts and methanol-tolerance property in alkaline solution. Thus the Shewanella-mediated biosynthesis method we provided here might be a new strategy for the preparation of various transition metal oxides as high-performance ORR electrocatalysts at low cost. PMID:25425435

  10. Ultrathin graphitic carbon nitride nanosheets: a low-cost, green, and highly efficient electrocatalyst toward the reduction of hydrogen peroxide and its glucose biosensing application

    NASA Astrophysics Data System (ADS)

    Tian, Jingqi; Liu, Qian; Ge, Chenjiao; Xing, Zhicai; Asiri, Abdullah M.; Al-Youbi, Abdulrahman O.; Sun, Xuping

    2013-09-01

    In this communication, we demonstrate for the first time that ultrathin graphitic carbon nitride (g-C3N4) nanosheets can serve as a low-cost, green, and highly efficient electrocatalyst toward the reduction of hydrogen peroxide. We further demonstrate its application for electrochemical glucose biosensing in both buffer solution and human serum medium with a detection limit of 11 μM and 45 μM, respectively.In this communication, we demonstrate for the first time that ultrathin graphitic carbon nitride (g-C3N4) nanosheets can serve as a low-cost, green, and highly efficient electrocatalyst toward the reduction of hydrogen peroxide. We further demonstrate its application for electrochemical glucose biosensing in both buffer solution and human serum medium with a detection limit of 11 μM and 45 μM, respectively. Electronic supplementary information (ESI) available: Experimental section and supplementary figures. See DOI: 10.1039/c3nr02031b

  11. Method and electrochemical cell for synthesis and treatment of metal monolayer electrocatalysts metal, carbon, and oxide nanoparticles ion batch, or in continuous fashion

    DOEpatents

    Adzic, Radoslav; Zhang, Junliang; Sasaki, Kotaro

    2015-04-28

    An apparatus and method for synthesis and treatment of electrocatalyst particles in batch or continuous fashion is provided. In one embodiment, the apparatus comprises a sonication bath and a two-compartment chamber submerged in the sonication bath. The upper and lower compartments are separated by a microporous material surface. The upper compartment comprises a cover and a working electrode (WE) connected to a Pt foil contact, with the foil contact connected to the microporous material. The upper chamber further comprises reference counter electrodes. The lower compartment comprises an electrochemical cell containing a solution of metal ions. In one embodiment, the method for synthesis of electrocatalysts comprises introducing a plurality of particles into the apparatus and applying sonication and an electrical potential to the microporous material connected to the WE. After the non-noble metal ions are deposited onto the particles, the non-noble metal ions are displaced by noble-metal ions by galvanic displacement.

  12. Sulfur-doped graphene derived from cycled lithium-sulfur batteries as a metal-free electrocatalyst for the oxygen reduction reaction.

    PubMed

    Ma, Zhaoling; Dou, Shuo; Shen, Anli; Tao, Li; Dai, Liming; Wang, Shuangyin

    2015-02-01

    Heteroatom-doped carbon materials have been extensively investigated as metal-free electrocatalysts to replace commercial Pt/C catalysts in oxygen reduction reactions in fuel cells and Li-air batteries. However, the synthesis of such materials usually involves high temperature or complicated equipment. Graphene-based sulfur composites have been recently developed to prolong the cycling life of Li-S batteries, one of the most attractive energy-storage devices. Given the high cost of graphene, there is significant demand to recycle and reuse graphene from Li-S batteries. Herein, we report a green and cost-effective method to prepare sulfur-doped graphene, achieved by the continuous charge/discharge cycling of graphene-sulfur composites in Li-S batteries. This material was used as a metal-free electrocatalyst for the oxygen reduction reaction and shows better electrocatalytic activity than pristine graphene and better methanol tolerance durability than Pt/C. PMID:25483872

  13. Three-Dimensional Crystalline/Amorphous Co/Co3O4 Core/Shell Nanosheets as Efficient Electrocatalysts for the Hydrogen Evolution Reaction.

    PubMed

    Yan, Xiaodong; Tian, Lihong; He, Min; Chen, Xiaobo

    2015-09-01

    Earth-abundant, low-cost electrocatalysts with outstanding catalytic activity in the electrochemical hydrogen evolution reaction (HER) are critical in realizing the hydrogen economy to lift our future welfare and civilization. Here we report that excellent HER activity has been achieved with three-dimensional core/shell Co/Co3O4 nanosheets composed of a metallic cobalt core and an amorphous cobalt oxide shell. A benchmark HER current density of 10 mA cm(-2) has been achieved at an overpotential of ∼90 mV in 1 M KOH. The excellent activity is enabled with the unique metal/oxide core/shell structure, which allows high electrical conductivity in the core and high catalytic activity on the shell. This finding may open a door to the design and fabrication of earth-abundant, low-cost metal oxide electrocatalysts with satisfactory hydrogen evolution reaction activities. PMID:26295904

  14. The Fundamental Role of Nano-Scale Oxide Films in the Oxidation of Hydrogen and the Reduction of Oxygen on Noble Metal Electrocatalysts

    SciTech Connect

    Digby Macdonald

    2005-04-15

    The derivation of successful fuel cell technologies requires the development of more effective, cheaper, and poison-resistant electrocatalysts for both the anode (H{sub 2} oxidation in the presence of small amounts of CO from the reforming of carbonaceous fuels) and the cathode (reduction of oxygen in the presence of carried-over fuel). The proposed work is tightly focused on one specific aspect of electrocatalysis; the fundamental role(s) played by nanoscale (1-2 nm thick) oxide (''passive'') films that form on the electrocatalyst surfaces above substrate-dependent, critical potentials, on charge transfer reactions, particularly at elevated temperatures (25 C < T < 200 C). Once the role(s) of these films is (are) adequately understood, we will then use this information to specify, at the molecular level, optimal properties of the passive layer for the efficient electrocatalysis of the oxygen reduction reaction.

  15. Amorphous Co(OH)2 nanosheet electrocatalyst and the physical mechanism for its high activity and long-term cycle stability

    NASA Astrophysics Data System (ADS)

    Gao, Y. Q.; Li, H. B.; Yang, G. W.

    2016-01-01

    Good conductivity is conventionally considered as a typical reference standard in terms of selecting water electrolysis catalysts. Cobalt hydroxide (Co(OH)2) has received extensive attention for its exceptional properties as a promising electrocatalysis catalyst. However, research on Co(OH)2 so far prefers to its crystal phase instead of amorphous phase because the former generally exhibits better conductivity. Here, we have demonstrated that the amorphous Co(OH)2 electrocatalyst synthesized via a simple, facile, green, and low-cost electrochemistry technique possesses high activity and long-term cycle stability in the oxygen evolution reaction (OER). The as-synthesized Co(OH)2 electrode was found to be a promising electrocatalyst for mediating OER in alkaline media, as evidenced by the overpotential of 0.38 V at a current density of 10 mA cm-2 and a Tafel slope of 68 mV dec-1. The amorphous Co(OH)2 also presented outstanding durability and its stability was just as well as that of crystalline Co(OH)2. Generally, the integrated electrochemical performances of the amorphous Co(OH)2 in the OER process were much superior to that of the crystalline Co(OH)2 materials. We also established that the short-range order, i.e., nanophase, of amorphous Co(OH)2 creates a lot of active sites for OER which can greatly promote the electrocatalysis performance of amorphous catalysts. These findings showed that the conventional understanding of selecting electrocatalysts with conductivity as a typical reference standard seems out of date for developing new catalysts at the nanometer, which actually open a door to applications of amorphous nanomaterials as an advanced electrocatalyst in the field of water oxidation.

  16. Ultrathin graphitic carbon nitride nanosheets: a low-cost, green, and highly efficient electrocatalyst toward the reduction of hydrogen peroxide and its glucose biosensing application.

    PubMed

    Tian, Jingqi; Liu, Qian; Ge, Chenjiao; Xing, Zhicai; Asiri, Abdullah M; Al-Youbi, Abdulrahman O; Sun, Xuping

    2013-10-01

    In this communication, we demonstrate for the first time that ultrathin graphitic carbon nitride (g-C₃N₄) nanosheets can serve as a low-cost, green, and highly efficient electrocatalyst toward the reduction of hydrogen peroxide. We further demonstrate its application for electrochemical glucose biosensing in both buffer solution and human serum medium with a detection limit of 11 μM and 45 μM, respectively. PMID:23934305

  17. N-doped crumpled graphene derived from vapor phase deposition of PPy on graphene aerogel as an efficient oxygen reduction reaction electrocatalyst.

    PubMed

    Wang, Meng; Wang, Jiazhao; Hou, Yuyang; Shi, Dongqi; Wexler, David; Poynton, Simon D; Slade, Robert C T; Zhang, Weimin; Liu, Huakun; Chen, Jun

    2015-04-01

    Nitrogen-doped crumpled graphene (NCG) is successfully synthesized via vapor phase deposition of polypyrrole onto graphene aerogel followed by thermal treatment. The NCG was explored as an electrocatalyst for the oxygen reduction reaction, showing comparable electrocatalytic performance with the commercial Pt/C in alkaline membrane exchange fuel cells because of the well-regulated nitrogen doping and the robust micro-3D crumpled porous nanostructure. PMID:25804889

  18. One-pot Synthesis of Nitrogen and Phosphorus Co-doped Graphene and Its Use as High-performance Electrocatalyst for Oxygen Reduction Reaction.

    PubMed

    Dong, Liye; Hu, Chuangang; Huang, Xianke; Chen, Nan; Qu, Liangti

    2015-12-01

    In this study, N,P co-doped graphene (NPG) was prepared by a one-step pyrolysis using a mixture of graphene oxide and hexachlorocyclotriphosphazene (HCCP), in which HCCP was used as both the N and P source. Furthermore, it is shown that NPG electrodes, as efficient metal-free electrocatalysts, have a high onset potential, high current density, and long-term stability for the oxygen reduction reaction. PMID:26305045

  19. Synthesis of Porous δ-MnO2 Submicron Tubes as Highly Efficient Electrocatalyst for Rechargeable Li-O2 Batteries.

    PubMed

    Zhang, Peng; Sun, Dongfei; He, Mu; Lang, Junwei; Xu, Shan; Yan, Xingbin

    2015-06-01

    Lithium-oxygen (Li-O2 ) batteries are receiving intense interest because of their high energy density. A new tubular δ-MnO2 material prepared by a simple hydrothermal synthesis is an efficient electrocatalyst for Li-O2 batteries. The synthesized δ-MnO2 exhibits a unique tubular structure, in which the porous walls are composed of highly dispersed ultrathin δ-MnO2 nanosheets. Such a unique structure and its intrinsic catalytic activity provide the right electrocatalyst characteristics for high-performance Li-O2 batteries. As a consequence, suppressed overpotentials-especially the oxygen evolution reaction overpotential-superior rate capability, and desirable cycle life are achieved with these submicron δ-MnO2 tubes as the electrocatalyst. Remarkably, the discharge product Li2 O2 of the Li-O2 battery exhibits a uniform nanosheet-like morphology, which indicates the critical role of the δ-MnO2 in the electrochemical process, and a mechanism is proposed to analyze the catalysis of δ-MnO2 . PMID:25944388

  20. Self-assembled platinum nanoparticles on sulfonic acid-grafted graphene as effective electrocatalysts for methanol oxidation in direct methanol fuel cells

    NASA Astrophysics Data System (ADS)

    Lu, Jinlin; Li, Yanhong; Li, Shengli; Jiang, San Ping

    2016-02-01

    In this article, sulfonic acid-grafted reduced graphene oxide (S-rGO) were synthesized using a one-pot method under mild conditions, and used as Pt catalyst supports to prepare Pt/S-rGO electrocatalysts through a self-assembly route. The structure, morphologies and physicochemical properties of S-rGO were examined in detail by techniques such as atomic force microscope (AFM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The S-rGO nanosheets show excellent solubility and stability in water and the average particle size of Pt nanoparticles supported on S-rGO is ~3.8 nm with symmetrical and uniform distribution. The electrocatalytic properties of Pt/S-rGO were investigated for methanol oxidation reaction (MOR) in direct methanol fuel cells (DMFCs). In comparison to Pt supported on high surface area Vulcan XC-72 carbon (Pt/VC) and Pt/rGO, the Pt/S-rGO electrocatalyst exhibits a much higher electrocatalytic activity, faster reaction kinetics and a better stability. The results indicate that Pt/S-rGO is a promising and effective electrocatalyst for MOR of DMFCs.

  1. Using nitrogen-rich polymeric network and iron(II) acetate as precursors to synthesize highly efficient electrocatalyst for oxygen reduction reaction in alkaline media

    NASA Astrophysics Data System (ADS)

    Yang, Mei; Chen, Hongbiao; Yang, Duanguang; Gao, Yong; Li, Huaming

    2016-03-01

    Carbon-supported transition metal/nitrogen (M-N/C) materials are considered as one of the most promising electrocatalysts for the oxygen reduction reaction (ORR) owing to their high ORR electrocatalytic activity, long-term stability, and excellent methanol tolerance. So far only a few examples of such catalysts are prepared from N-containing polymers. Herein, we report a novel Fe-N/C catalyst using a nitrogen-rich polymeric network and iron(II) acetate as the precursors. The porous polymeric network is fabricated by one-step Friedel-Crafts reaction of a low-cost cross-linker, formaldehyde dimethyl acetal, with 2,4,6-tripyrrol-1,3,5-triazine. Compared to commercial Pt/C catalyst, the as-prepared Fe-N/C electrocatalyst exhibits superior ORR activity in alkaline electrolyte, and comparable ORR activity in acidic medium. The results obtained are significant for the development of new Fe-N/C electrocatalysts for fuel cells.

  2. Self-assembled platinum nanoparticles on sulfonic acid-grafted graphene as effective electrocatalysts for methanol oxidation in direct methanol fuel cells

    PubMed Central

    Lu, Jinlin; Li, Yanhong; Li, Shengli; Jiang, San Ping

    2016-01-01

    In this article, sulfonic acid-grafted reduced graphene oxide (S-rGO) were synthesized using a one-pot method under mild conditions, and used as Pt catalyst supports to prepare Pt/S-rGO electrocatalysts through a self-assembly route. The structure, morphologies and physicochemical properties of S-rGO were examined in detail by techniques such as atomic force microscope (AFM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The S-rGO nanosheets show excellent solubility and stability in water and the average particle size of Pt nanoparticles supported on S-rGO is ~3.8 nm with symmetrical and uniform distribution. The electrocatalytic properties of Pt/S-rGO were investigated for methanol oxidation reaction (MOR) in direct methanol fuel cells (DMFCs). In comparison to Pt supported on high surface area Vulcan XC-72 carbon (Pt/VC) and Pt/rGO, the Pt/S-rGO electrocatalyst exhibits a much higher electrocatalytic activity, faster reaction kinetics and a better stability. The results indicate that Pt/S-rGO is a promising and effective electrocatalyst for MOR of DMFCs. PMID:26876468

  3. Facile solvothermal synthesis of highly active and robust Pd1.87Cu0.11Sn electrocatalyst towards direct ethanol fuel cell applications

    NASA Astrophysics Data System (ADS)

    Jana, Rajkumar; Dhiman, Shikha; Peter, Sebastian C.

    2016-08-01

    Ordered intermetallic Pd1.87Cu0.11Sn ternary electrocatalyst has been synthesized by sodium borohydride reduction of precursor salts Pd(acac)2, CuCl2.2H2O and SnCl2 using one-pot solvothermal synthesis method at 220 °C with a reaction time of 24 h. To the best of our knowledge, here for the first time we report surfactant free synthesis of a novel ordered intermetallic ternary Pd1.87Cu0.11Sn nanoparticles. The ordered structure of the catalyst has been confirmed by powder x-ray diffraction, transmission electron microscopy (TEM). Composition and morphology of the nanoparticles have been confirmed through field emission scanning electron microscopy, energy-dispersive spectrometry and TEM. The electrocatalytic activity and stability of the ternary electrocatalyst towards ethanol oxidation in alkaline medium was investigated by cyclic voltammetry and chronoamperometry techniques. The catalyst is proved to be highly efficient and stable upto 500th cycle and even better than commercially available Pd/C (20 wt%) electrocatalysts. The specific and mass activity of the as synthesized ternary catalyst are found to be ∼4.76 and ∼2.9 times better than that of commercial Pd/C. The enhanced activity and stability of the ordered ternary Pd1.87Cu0.11Sn catalyst can make it as a promising candidate for the alkaline direct ethanol fuel cell application.

  4. A CoFe2O4/graphene nanohybrid as an efficient bi-functional electrocatalyst for oxygen reduction and oxygen evolution

    NASA Astrophysics Data System (ADS)

    Bian, Weiyong; Yang, Zhenrong; Strasser, Peter; Yang, Ruizhi

    2014-03-01

    Development of efficient electrocatalysts for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) remain key issues for the commercialization of fuel cells and metal-air batteries. In this study, A CoFe2O4/graphene nanohybrid is facilely synthesized via a two-step process and applied as an electrocatalyst for the ORR and the OER. The as-prepared CoFe2O4/graphene nanohybrid demonstrates excellent catalytic activity for the ORR. At the same mass loading, the Tafel slope of CoFe2O4/graphene electrocatalyst for the ORR is comparable to that of the commercial Pt/C (20 wt% Pt on Vulcan XC-72, Johnson Matthey). The ORR on CoFe2O4/graphene mainly favours a direct 4e- reaction pathway. The CoFe2O4/graphene nanohybrid also affords high catalytic activity for the OER. The chronoamperometric tests show that CoFe2O4/graphene catalyst exhibits excellent stability for both the ORR and the OER, outperforming the commercial Pt/C. The high electrocatalytic activity and durability of CoFe2O4/graphene nanohybrid are attributed to the strong coupling between CoFe2O4 nanoparticles and graphene.

  5. Cu-doped carbon nitride: Bio-inspired synthesis of H2-evolving electrocatalysts using graphitic carbon nitride (g-C3N4) as a host material

    NASA Astrophysics Data System (ADS)

    Zou, Xiaoxin; Silva, Rafael; Goswami, Anandarup; Asefa, Tewodros

    2015-12-01

    Splitting water effectively to produce hydrogen (H2) requires the development of non-noble-metal electrocatalysts that are able to make this reaction feasible and energy efficient. Herein, we present a novel "structure upgrading" synthetic approach for the design and synthesis of bio-inspired hydrogen-evolving electrocatalysts based on earth-abundant elements. Using g-C3N4 - an inexpensive inorganic polymer material - as a host material for copper ions, novel Cu-doped g-C3N4 materials with supramolecular structure, efficient electrocatalytic activity and modest overpotentials for hydrogen evolution reaction (HER) are synthesized. Compared with most single-molecule analogs of hydrogenases that work only in organic media, the supramolecular Cu-doped g-C3N4 materials can serve as heterogeneous electrocatalysts with greater stability and good catalytic activity for HER in aqueous media. The materials afford a current density as high as 10 mA cm-2 at an overpotential as low as 390 mV, and work well in acidic media for, at least, 43 h.

  6. Platinum-TM (TM = Fe, Co) alloy nanoparticles dispersed nitrogen doped (reduced graphene oxide-multiwalled carbon nanotube) hybrid structure cathode electrocatalysts for high performance PEMFC applications.

    PubMed

    Vinayan, B P; Ramaprabhu, S

    2013-06-01

    The efforts to push proton exchange membrane fuel cells (PEMFC) for commercial applications are being undertaken globally. In PEMFC, the sluggish kinetics of oxygen reduction reactions (ORR) at the cathode can be improved by the alloying of platinum with 3d-transition metals (TM = Fe, Co, etc.) and with nitrogen doping, and in the present work we have combined both of these aspects. We describe a facile method for the synthesis of a nitrogen doped (reduced graphene oxide (rGO)-multiwalled carbon nanotubes (MWNTs)) hybrid structure (N-(G-MWNTs)) by the uniform coating of a nitrogen containing polymer over the surface of the hybrid structure (positively surface charged rGO-negatively surface charged MWNTs) followed by the pyrolysis of these (rGO-MWNTs) hybrid structure-polymer composites. The N-(G-MWNTs) hybrid structure is used as a catalyst support for the dispersion of platinum (Pt), platinum-iron (Pt3Fe) and platinum-cobalt (Pt3Co) alloy nanoparticles. The PEMFC performances of Pt-TM alloy nanoparticle dispersed N-(G-MWNTs) hybrid structure electrocatalysts are 5.0 times higher than that of commercial Pt-C electrocatalysts along with very good stability under acidic environment conditions. This work demonstrates a considerable improvement in performance compared to existing cathode electrocatalysts being used in PEMFC and can be extended to the synthesis of metal, metal oxides or metal alloy nanoparticle decorated nitrogen doped carbon nanostructures for various electrochemical energy applications. PMID:23644681

  7. Cotton Wool Derived Carbon Fiber Aerogel Supported Few-Layered MoSe2 Nanosheets As Efficient Electrocatalysts for Hydrogen Evolution.

    PubMed

    Zhang, Youfang; Zuo, Lizeng; Zhang, Longsheng; Huang, Yunpeng; Lu, Hengyi; Fan, Wei; Liu, Tianxi

    2016-03-23

    Recent studies have proven that newly emerging two-dimensional molybdenum diselenide (MoSe2) is a promising noble-metal-free electrocatalyst for hydrogen evolution reaction (HER). Increasing the exposures of the active edges of MoSe2 nanostructures is a key issue to fully realize the excellent electrochemical properties of MoSe2. In this work, a few-layered MoSe2/carbon fiber aerogel (CFA) hybrids have been facilely obtained through the combination of high-temperature carbonization and one-pot solvothermal reaction. CFA derived from cotton wool is used as a three-dimensional conductive network for construction of hierarchical MoSe2/CFA hybrids, where few-layered MoSe2 nanosheets are uniformly and perpendicularly decorated on the surfaces of CFA. In the designed and prepared hybrids, CFA effectively increases the exposures of the active edges of MoSe2 nanosheets as well as provides reduced lengths for both electron transportation and ion diffusion. Therefore, the obtained optimal MoSe2/CFA hybrid exhibits excellent electrochemical activity as HER electrocatalyst with a small onset potential of -0.104 V vs reversible hydrogen electrode and a small Tafel slope of 62 mV per decade, showing its great potential as a next-generation Pt-free electrocatalyst for HER. PMID:26927526

  8. Cobalt sulfide/N,S codoped porous carbon core-shell nanocomposites as superior bifunctional electrocatalysts for oxygen reduction and evolution reactions.

    PubMed

    Chen, Binling; Li, Rong; Ma, Guiping; Gou, Xinglong; Zhu, Yanqiu; Xia, Yongde

    2015-12-28

    Exploring highly-efficient and low-cost bifunctional electrocatalysts for both oxygen reduction reaction (ORR) and oxygen evolution reactions (OER) in the renewable energy area has gained momentum but still remains a significant challenge. Here we present a simple but efficient method that utilizes ZIF-67 as the precursor and template for the one-step generation of homogeneous dispersed cobalt sulfide/N,S-codoped porous carbon nanocomposites as high-performance electrocatalysts. Due to the favourable molecular-like structural features and uniform dispersed active sites in the precursor, the resulting nanocomposites, possessing a unique core-shell structure, high porosity, homogeneous dispersion of active components together with N and S-doping effects, not only show excellent electrocatalytic activity towards ORR with the high onset potential (around -0.04 V vs.-0.02 V for the benchmark Pt/C catalyst) and four-electron pathway and OER with a small overpotential of 0.47 V for 10 mA cm(-2) current density, but also exhibit superior stability (92%) to the commercial Pt/C catalyst (74%) in ORR and promising OER stability (80%) with good methanol tolerance. Our findings suggest that the transition metal sulfide-porous carbon nanocomposites derived from the one-step simultaneous sulfurization and carbonization of zeolitic imidazolate frameworks are excellent alternative bifunctional electrocatalysts towards ORR and OER in the next generation of energy storage and conversion technologies. PMID:26599403

  9. Microporous La0.8Sr0.2MnO3 perovskite nanorods as efficient electrocatalysts for lithium-air battery

    NASA Astrophysics Data System (ADS)

    Lu, Fanliang; Wang, Yarong; Jin, Chao; Li, Fan; Yang, Ruizhi; Chen, Fanglin

    2015-10-01

    Efficient electrocatalyst for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is the most critical factor to influence the performance of lithium-air batteries. We present La0.8Sr0.2MnO3 (LSM) perovskite nanorods as high active electrocatalyst fabricated via a soft template method for lithium-air batteries. The as-prepared LSM nanorods are microporous with numerous defects and large surface area (20.6 m2 g-1), beneficial to the ORR and OER in the discharge and charge processes, respectively. Lithium-air batteries based on the microporous LSM nanorods electrocatalysts show enhanced electrochemical performances, including high first discharge specific capacity (6890 mAh g-1(electrode) at 200 mA g-1), low overpotential, good rate capability (up to 400 mA g-1), and cycle stability (only 1.1% voltage loss after 30 circles of specific capacity limit of 1000 mAh g-1 tested at 200 mA g-1). The improved performance might be due to the synergistic effect of the unique microporous and one-dimensional structure and numerous defects of the prepared LSM catalyst.

  10. Control of the composition of Pt-Ni electrocatalysts in surfactant-free synthesis using neat N-formylpiperidine

    NASA Astrophysics Data System (ADS)

    Zhang, Na; Tsao, Kai-Chieh; Pan, Yung-Tin; Yang, Hong

    2016-01-01

    This paper describes the facile and surfactant-free synthesis of faceted Pt-Ni alloy nanoparticle electrocatalysts using neat N-formylpiperidine as a new type of solvent. Unlike the widely-used colloidal synthesis based on long-carbon chain surfactants, nanoparticles made in neat N-formylpiperidine possess a directly accessible surface for electrocatalytic reactions, making it a very attractive alternative solvent. The area-specific oxygen reduction reaction (ORR) activity is much higher than the commercial Pt/C catalyst reference and reaches a maximum of 1.12 mA cm-2 for the Pt-Ni alloy nanoparticles. We observed that the freshly formed Pt-Ni alloy could have controllable bulk and near surface compositions under the same initial reaction conditions and precursor ratio. The change in the composition could be attributed to the effect of CO on the formation of uniform nuclei at the initial stage, and a different deposition rate between Pt and Ni metals during the growth. The well-defined Pt-Ni nanoparticle catalysts show strong composition-dependent catalytic behavior in ORR, highlighting the important role of controlling the growth kinetics in the preparation of active Pt-Ni ORR catalysts.This paper describes the facile and surfactant-free synthesis of faceted Pt-Ni alloy nanoparticle electrocatalysts using neat N-formylpiperidine as a new type of solvent. Unlike the widely-used colloidal synthesis based on long-carbon chain surfactants, nanoparticles made in neat N-formylpiperidine possess a directly accessible surface for electrocatalytic reactions, making it a very attractive alternative solvent. The area-specific oxygen reduction reaction (ORR) activity is much higher than the commercial Pt/C catalyst reference and reaches a maximum of 1.12 mA cm-2 for the Pt-Ni alloy nanoparticles. We observed that the freshly formed Pt-Ni alloy could have controllable bulk and near surface compositions under the same initial reaction conditions and precursor ratio. The change

  11. Controllable synthesis of mesoporous carbon nanospheres and Fe-N/carbon nanospheres as efficient oxygen reduction electrocatalysts

    NASA Astrophysics Data System (ADS)

    Wei, Jing; Liang, Yan; Zhang, Xinyi; Simon, George P.; Zhao, Dongyuan; Zhang, Jin; Jiang, Sanping; Wang, Huanting

    2015-03-01

    The synthesis of mesoporous carbon nanospheres (MCNs), especially with diameters below 200 nm remains a great challenge due to weak interactions between the carbon precursors and soft templates, as well as the uncontrollable cross-linking rate of carbon precursors. Herein, we demonstrate a simple acid-assisted, hydrothermal synthesis approach to synthesizing such uniform MCNs with well controlled diameters ranging from 20 to 150 nm under highly acidic conditions (2 M HCl). Both the carbon precursor and the template are partly protonated under such conditions and show additional Coulombic interactions with chloride ions (acts as mediators). This kind of enhanced interaction is similar to that of the ``I+X-S+'' mechanism in the synthesis of mesoporous metal oxide, which can effectively retard the cross-linking rate of resol molecules and avoid macroscopic phase separation during the hydrothermal synthesis. Due to their uniform spherical morphology, small diameter, and high surface areas, MCNs can be modified with Fe and N species via impregnation of cheap precursors (ferric nitrate and dicyandiamide), which are further converted into nonprecious electrocatalysts for oxygen reduction reactions. The resulting Fe-N/MCNs exhibit high catalytic activities, long-term stability and improved methanol tolerance under alkaline conditions, which can be potentially used in direct methanol fuel cells and metal-air batteries.The synthesis of mesoporous carbon nanospheres (MCNs), especially with diameters below 200 nm remains a great challenge due to weak interactions between the carbon precursors and soft templates, as well as the uncontrollable cross-linking rate of carbon precursors. Herein, we demonstrate a simple acid-assisted, hydrothermal synthesis approach to synthesizing such uniform MCNs with well controlled diameters ranging from 20 to 150 nm under highly acidic conditions (2 M HCl). Both the carbon precursor and the template are partly protonated under such conditions

  12. NiCo2S4 nanowires array as an efficient bifunctional electrocatalyst for full water splitting with superior activity

    NASA Astrophysics Data System (ADS)

    Liu, Danni; Lu, Qun; Luo, Yonglan; Sun, Xuping; Asiri, Abdullah M.

    2015-09-01

    The present communication reports the topotactic conversion of NiCo2O4 nanowires array on carbon cloth (NiCo2O4 NA/CC) into NiCo2S4 NA/CC, which is used as an efficient bifunctional electrocatalyst for water splitting with good durability and superior activity in 1.0 M KOH. This NiCo2S4 NA/CC electrode produces 100 mA cm-2 at an overpotential of 305 mV for hydrogen evolution and 100 mA cm-2 at an overpotential of 340 mV for oxygen evolution. To afford a 10 mA cm-2 water-splitting current, the alkaline water electrolyzer made from NiCo2S4 NA/CC needs a cell voltage of 1.68 V, which is 300 mV less than that for NiCo2O4 NA/CC, and has good stability.The present communication reports the topotactic conversion of NiCo2O4 nanowires array on carbon cloth (NiCo2O4 NA/CC) into NiCo2S4 NA/CC, which is used as an efficient bifunctional electrocatalyst for water splitting with good durability and superior activity in 1.0 M KOH. This NiCo2S4 NA/CC electrode produces 100 mA cm-2 at an overpotential of 305 mV for hydrogen evolution and 100 mA cm-2 at an overpotential of 340 mV for oxygen evolution. To afford a 10 mA cm-2 water-splitting current, the alkaline water electrolyzer made from NiCo2S4 NA/CC needs a cell voltage of 1.68 V, which is 300 mV less than that for NiCo2O4 NA/CC, and has good stability. Electronic supplementary information (ESI) available: Experimental section and ESI Figures. See DOI: 10.1039/c5nr04064g

  13. Highly graphitized nitrogen-doped porous carbon nanopolyhedra derived from ZIF-8 nanocrystals as efficient electrocatalysts for oxygen reduction reactions

    NASA Astrophysics Data System (ADS)

    Zhang, Linjie; Su, Zixue; Jiang, Feilong; Yang, Lingling; Qian, Jinjie; Zhou, Youfu; Li, Wenmu; Hong, Maochun

    2014-05-01

    Nitrogen-doped graphitic porous carbons (NGPCs) have been synthesized by using a zeolite-type nanoscale metal-organic framework (NMOF) as a self-sacrificing template, which simultaneously acts as both the carbon and nitrogen sources in a facile carbonization process. The NGPCs not only retain the nanopolyhedral morphology of the parent NMOF, but also possess rich nitrogen, high surface area and hierarchical porosity with well-conducting networks. The promising potential of NGPCs as metal-free electrocatalysts for oxygen reduction reactions (ORR) in fuel cells is demonstrated. Compared with commercial Pt/C, the optimized NGPC-1000-10 (carbonized at 1000 °C for 10 h) catalyst exhibits comparable electrocatalytic activity via an efficient four-electron-dominant ORR process coupled with superior methanol tolerance as well as cycling stability in alkaline media. Furthermore, the controlled experiments reveal that the optimum activity of NGPC-1000-10 can be attributed to the synergetic contributions of the abundant active sites with high graphitic-N portion, high surface area and porosity, and the high degree of graphitization. Our findings suggest that solely MOF-derived heteroatom-doped carbon materials can be a promising alternative for Pt-based catalysts in fuel cells.Nitrogen-doped graphitic porous carbons (NGPCs) have been synthesized by using a zeolite-type nanoscale metal-organic framework (NMOF) as a self-sacrificing template, which simultaneously acts as both the carbon and nitrogen sources in a facile carbonization process. The NGPCs not only retain the nanopolyhedral morphology of the parent NMOF, but also possess rich nitrogen, high surface area and hierarchical porosity with well-conducting networks. The promising potential of NGPCs as metal-free electrocatalysts for oxygen reduction reactions (ORR) in fuel cells is demonstrated. Compared with commercial Pt/C, the optimized NGPC-1000-10 (carbonized at 1000 °C for 10 h) catalyst exhibits comparable

  14. Hierarchically porous Fe-N-C derived from covalent-organic materials as a highly efficient electrocatalyst for oxygen reduction

    NASA Astrophysics Data System (ADS)

    Zuo, Quan; Zhao, Pingping; Luo, Wei; Cheng, Gongzhen

    2016-07-01

    Developing high-performance non-precious catalysts to replace platinum as oxygen reduction reaction (ORR) catalysts is still a big scientific and technological challenge. Herein, we report a simple method for the synthesis of a FeNC catalyst with a 3D hierarchically micro/meso/macro porous network and high surface area through a simple carbonization method by taking the advantages of a high specific surface area and diverse pore dimensions in 3D porous covalent-organic material. The resulting FeNC-900 electrocatalyst with improved reactant/electrolyte transport and sufficient active site exposure, exhibits outstanding ORR activity with a half-wave potential of 0.878 V, ca. 40 mV more positive than Pt/C for ORR in alkaline solution, and a half-wave potential of 0.72 V, which is comparable to that of Pt/C in acidic solution. In particular, the resulting FeNC-900 exhibits a much higher stability and methanol tolerance than those of Pt/C, which makes it among the best non-precious catalysts ever reported for ORR.Developing high-performance non-precious catalysts to replace platinum as oxygen reduction reaction (ORR) catalysts is still a big scientific and technological challenge. Herein, we report a simple method for the synthesis of a FeNC catalyst with a 3D hierarchically micro/meso/macro porous network and high surface area through a simple carbonization method by taking the advantages of a high specific surface area and diverse pore dimensions in 3D porous covalent-organic material. The resulting FeNC-900 electrocatalyst with improved reactant/electrolyte transport and sufficient active site exposure, exhibits outstanding ORR activity with a half-wave potential of 0.878 V, ca. 40 mV more positive than Pt/C for ORR in alkaline solution, and a half-wave potential of 0.72 V, which is comparable to that of Pt/C in acidic solution. In particular, the resulting FeNC-900 exhibits a much higher stability and methanol tolerance than those of Pt/C, which makes it among the

  15. X-ray Fluorescence Investigation of Ordered Intermetallic Phases as Electrocatalysts towards the Oxidation of Small Organic Molecules

    SciTech Connect

    Liu, Yi; Lowe, Michael A.; Finkelstein, Ken D.; Dale, Darren S.; DiSalvo, Francis J.; Abruña, Héctor D.

    2010-10-13

    -element nanoparticles as electrocatalysts. This is, to our knowledge, the first report of nondestructive, quantitative characterization of bimetallic or multi-elemental nanoparticles electrocatalysts under active electrochemical control.

  16. Semimetallic MoP2: an active and stable hydrogen evolution electrocatalyst over the whole pH range

    NASA Astrophysics Data System (ADS)

    Pu, Zonghua; Saana Amiinu, Ibrahim; Wang, Min; Yang, Yushi; Mu, Shichun

    2016-04-01

    Developing efficient non-precious metal hydrogen evolution reaction (HER) electrocatalysts is a great challenge for sustainable hydrogen production from water. In this communication, for the first time, semimetallic MoP2 nanoparticle films on a metal Mo plate (MoP2 NPs/Mo) are fabricated through a facile two-step strategy. When used as a binder-free hydrogen evolution cathode, the as-prepared MoP2 NPs/Mo electrode exhibits superior HER catalytic activity at all pH values. At a current density of 10 mA cm-2, the catalyst displays overpotentials of 143, 211 and 194 mV in 0.5 M H2SO4, 1.0 M phosphate buffer solution and 1.0 M KOH, respectively. Furthermore, it exhibits excellent stability over a wide pH range. Thus, this in situ route opens up a new avenue for the fabrication of highly efficient, cost-effective and binder-free non-precious catalysts for water splitting and other electrochemical devices.Developing efficient non-precious metal hydrogen evolution reaction (HER) electrocatalysts is a great challenge for sustainable hydrogen production from water. In this communication, for the first time, semimetallic MoP2 nanoparticle films on a metal Mo plate (MoP2 NPs/Mo) are fabricated through a facile two-step strategy. When used as a binder-free hydrogen evolution cathode, the as-prepared MoP2 NPs/Mo electrode exhibits superior HER catalytic activity at all pH values. At a current density of 10 mA cm-2, the catalyst displays overpotentials of 143, 211 and 194 mV in 0.5 M H2SO4, 1.0 M phosphate buffer solution and 1.0 M KOH, respectively. Furthermore, it exhibits excellent stability over a wide pH range. Thus, this in situ route opens up a new avenue for the fabrication of highly efficient, cost-effective and binder-free non-precious catalysts for water splitting and other electrochemical devices. Electronic supplementary information (ESI) available: Experimental section and figures. See DOI: 10.1039/c6nr00820h

  17. Co/CoO/CoFe2O4/G nanocomposites derived from layered double hydroxides towards mass production of efficient Pt-free electrocatalysts for oxygen reduction reaction.

    PubMed

    Huo, Ruijie; Jiang, Wen-Jie; Xu, Sailong; Zhang, Fazhi; Hu, Jin-Song

    2014-01-01

    Development of a simple, reproducible and cost-effective protocol for mass production of non-precious-metal electrocatalysts for oxygen reduction reaction (ORR) is still challenging but highly desirable for their practical applications in industry. Herein, we developed a facile and scalable method to directly produce graphene (G) supported CoFe-LDHs and successfully used them as a precursor for mass production of Co/CoO/CoFe2O4/G as a low-cost and Pt-free efficient electrocatalyst, which exhibits comparable electrocatalytic activity and much better durability for ORR in comparison with commercial Pt/C catalysts. The result may provide a way for cost-effective production of ORR electrocatalysts on a large scale for practical applications. PMID:24247636

  18. Nitrogen-doped porous carbon nanosheets made from biomass as highly active electrocatalyst for oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Pan, Fuping; Cao, Zhongyue; Zhao, Qiuping; Liang, Hongyu; Zhang, Junyan

    2014-12-01

    The successful commercialization of fuel cells requires the efficient electrocatalyst to make the oxygen reduction reaction (ORR) fast because of the sluggish nature of ORR and the high cost of the platinum catalysts. In this work, we report the excellent performance of metal-free nitrogen-doped porous carbon nanosheets (NPCN) with hierarchical porous structure and a high surface area of 1436.02 m2 g-1 for catalyzing ORR. The active NPCN is synthesized via facile high-temperature carbonization of natural ginkgo leaves followed by purification and ammonia post-treatment without using additional supporting templates and activation processes. In O2-saturated 0.1 M KOH solution, the resultant NPCN exhibits a high kinetic-limiting current density of 13.57 mA cm-2 at -0.25 V (vs. Ag/AgCl) approaching that of the commercial Pt/C catalyst (14 mA cm-2) and long-term electrochemical stability. Notably, the NPCN shows a slightly negative ORR half-wave potential in comparison with Pt/C (ΔE1/2 = 19 mV). The excellent electrocatalytic properties of NPCN originate from the combined effect of optimal nitrogen doping, high surface area, and porous architecture, which induce the high-density distribution of highly active and stable catalytic sites.

  19. Comparative assessment of synthetic strategies toward active platinum-rhodium-tin electrocatalysts for efficient ethanol electro-oxidation

    NASA Astrophysics Data System (ADS)

    Erini, Nina; Krause, Paul; Gliech, Manuel; Yang, Ruizhi; Huang, Yunhui; Strasser, Peter

    2015-10-01

    The present work explores the effect of autoclave-based autogenous-pressure vs. ambient pressure conditions on the synthesis and properties of carbon-supported Pt-Rh-Sn nanoparticle electrocatalysts. The Pt-Rh-Sn nanoparticles were characterized by X-ray spectroscopy, electron microscopy and mass spectroscopy and deployed as catalysts for the electrocatalytic ethanol oxidation reaction. Pt-Rh-Sn catalysts precipitated with carbon already present showed narrow particle size distribution around 7 nm, while catalysts supported on carbon after particle formation showed broader size distribution ranging from 8 to 16 nm, similar metal loadings between 40 and 48 wt.% and similar atomic ratios of Pt:Rh:Sn of 30:10:60. The highest ethanol oxidation activity at low overpotentials associated with exceptionally early ethanol oxidation onset potential was observed for ambient-pressure catalysts with the active ternary alloy phase formed in presence of the carbon supports. In contrast, catalysts prepared under ambient pressure in a two-step approach, involving alloy particle formation followed by particle separation and subsequent deposition on the carbon support, yielded the highest overall mass activities. Based on the observed synthesis-activity correlations, a comparative assessment is provided of the synthetic techniques at high vs. low pressures, and in presence and absence of carbon support. Plausible hypotheses in terms of particle dispersion and interparticle distance accounting for these observed differences are discussed.

  20. Novel Flower-like Nickel Sulfide as an Efficient Electrocatalyst for Non-aqueous Lithium-Air Batteries

    PubMed Central

    Ma, Zhong; Yuan, Xianxia; Zhang, Zhenlin; Mei, Delong; Li, Lin; Ma, Zi-Feng; Zhang, Lei; Yang, Jun; Zhang, Jiujun

    2015-01-01

    In this paper, metal sulfide materials have been explored for the first time as a new choice of bifunctional cathode electrocatalyst materials for non-aqueous lithium-air batteries (LABs). Nickel sulfides with two different morphologies of flower-like (f-NiS) and rod-like (r-NiS) are successfully synthesized using a hydrothermal method with and without the assistance of cetyltrimethyl ammonium bromide. As LAB cathode catalysts, both f-NiS and r-NiS demonstrate excellent catalytic activities towards the formation and decomposition of Li2O2, resulting in improved specific capacity, reduced overpotentials and enhanced cycling performance when compared to those of pure Super P based electrode. Moreover, the morphology of NiS materials can greatly affect LAB performance. Particularly, the f-NiS is more favorable than r-NiS in terms of their application in LABs. When compared to both r-NiS and pure super P materials as LAB cathode materials, this f-NiS catalyst material can give the highest capacity of 6733 mA h g−1 and the lowest charge voltage of 4.24 V at the current density of 75 mA g−1 and also exhibit an quite stable cycling performance. PMID:26658833

  1. Subnanometer Molybdenum Sulfide on Carbon Nanotubes as a Highly Active and Stable Electrocatalyst for Hydrogen Evolution Reaction.

    PubMed

    Li, Ping; Yang, Zhi; Shen, Juanxia; Nie, Huagui; Cai, Qiran; Li, Luhua; Ge, Mengzhan; Gu, Cancan; Chen, Xi'an; Yang, Keqin; Zhang, Lijie; Chen, Ying; Huang, Shaoming

    2016-02-10

    Electrochemically splitting water for hydrogen evolution reaction (HER) has been viewed as a promising approach to produce renewable and clean hydrogen energy. However, searching for cheap and efficient HER electrocatalysts to replace the currently used Pt-based catalysts remains an urgent task. Herein, we develop a one-step carbon nanotube (CNT) assisted synthesis strategy with CNTs' strong adsorbability to mediate the growth of subnanometer-sized MoS(x) on CNTs. The subnanometer MoS(x)-CNT hybrids achieve a low overpotential of 106 mV at 10 mA cm(-2), a small Tafel slope of 37 mV per decade, and an unprecedentedly high turnover frequency value of 18.84 s(-1) at η = 200 mV among all reported non-Pt catalysts in acidic conditions. The superior performance of the hybrid catalysts benefits from the presence of a higher number of active sites and the abundant exposure of unsaturated S atoms rooted in the subnanometer structure, demonstrating a new class of subnanometer-scale catalysts. PMID:26765150

  2. Selective and Efficient Reduction of Carbon Dioxide to Carbon Monoxide on Oxide-Derived Nanostructured Silver Electrocatalysts.

    PubMed

    Ma, Ming; Trześniewski, Bartek J; Xie, Jie; Smith, Wilson A

    2016-08-01

    In this work, the selective electrocatalytic reduction of carbon dioxide to carbon monoxide on oxide-derived silver electrocatalysts is presented. By a simple synthesis technique, the overall high faradaic efficiency for CO production on the oxide-derived Ag was shifted by more than 400 mV towards a lower overpotential compared to that of untreated Ag. Notably, the Ag resulting from Ag oxide is capable of electrochemically reducing CO2 to CO with approximately 80 % catalytic selectivity at a moderate overpotential of 0.49 V, which is much higher than that (ca. 4 %) of untreated Ag under identical conditions. Electrokinetic studies show that the improved catalytic activity is ascribed to the enhanced stabilization of COOH(.) intermediate. Furthermore, highly nanostructured Ag is likely able to create a high local pH near the catalyst surface, which may also facilitate the catalytic activity for the reduction of CO2 with suppressed H2 evolution. PMID:27377237

  3. Determination of Reaction Mechanisms Occurring at Fuel Cell Electrocatalysts Using Electrochemical Methods, Spectroelectrochemical Measurements and Analytical Techniques

    NASA Astrophysics Data System (ADS)

    Coutanceau, C.; Baranton, S.; Lamy, C.

    There is now a great interest in developing different kinds of fuel cells for several applications (stationary electric power plants, transportation, portable electronic devices). For many applications, hydrogen is the most convenient fuel, but it is not a primary fuel, so that it has to be produced from different sources: water, fossil fuels (natural gas, hydrocarbons, etc.), biomass resources, etc. When produced from fossil fuel and biomass resources, hydrogen gas contains a non negligible amount of CO, which acts as a poisoning species for platinum electrocatalysts. Other fuels, particularly alcohols, which are liquid under ambient temperature and pressure, are more convenient due to the easiness of their handling and distribution and high theoretical energy density (6 to 8 kWh kg-1, for methanol and ethanol, respectively). Direct Methanol Fuel Cells (DMFCs) and Direct Ethanol Fuel Cells (DEFCs) are based on the Proton Exchange Membrane Fuel Cell (PEMFC) system, in which hydrogen is replaced by the alcohol. Moreover, due to the presence of carbon monoxide, the issues for PEMFCs working with reformate gas are close to those met in Direct Alcohol Fuel Cells (DAFCs), where the dissociative adsorption of alcohol leads to the formation of adsorbed CO species.

  4. Ruthenium and ruthenium oxide nanofiber supports for enhanced activity of platinum electrocatalysts in the methanol oxidation reaction.

    PubMed

    An, Geon-Hyoung; Lee, Eun-Hwan; Ahn, Hyo-Jin

    2016-06-01

    Novel supports for the dispersion of Pt electrocatalysts in fuel cells are constantly being developed in order to improve the electrochemical performance and reduce the cost. The electrocatalytic activity and stability in fuel cells largely depend on the surface morphology and structure of the support. In this study, Ru and RuO2 nanofibers prepared by electrospinning and post-calcination have been considered as Pt-catalyst supports. The composite material loaded with 20 wt% Pt catalyst exhibited a high anodic current density of 641.7 mA mgPt(-1), a high IF/IB ratio of 1.9, and excellent electrocatalytic stability compared to commercial Pt/C. The improved anodic current density of the composite is attributed to the high dispersion of the Pt catalyst over the large surface area of the nanosized support grains, while its low onset potential, high IF/IB ratio, and excellent electrocatalytic stability are ascribed to a bifunctional effect resulting from the existence of Ru atoms on the support surface. Finally, the efficient electron transfer and a rapid diffusion rate of the electrolyte are due to the unique network structure of the supports. Thus, the Ru and RuO2 nanofiber composites act as promising Pt-catalyst supports for the methanol oxidation reaction. PMID:27188230

  5. Bifunctional non-noble metal oxide nanoparticle electrocatalysts through lithium-induced conversion for overall water splitting

    PubMed Central

    Wang, Haotian; Lee, Hyun-Wook; Deng, Yong; Lu, Zhiyi; Hsu, Po-Chun; Liu, Yayuan; Lin, Dingchang; Cui, Yi

    2015-01-01

    Developing earth-abundant, active and stable electrocatalysts which operate in the same electrolyte for water splitting, including oxygen evolution reaction and hydrogen evolution reaction, is important for many renewable energy conversion processes. Here we demonstrate the improvement of catalytic activity when transition metal oxide (iron, cobalt, nickel oxides and their mixed oxides) nanoparticles (∼20 nm) are electrochemically transformed into ultra-small diameter (2–5 nm) nanoparticles through lithium-induced conversion reactions. Different from most traditional chemical syntheses, this method maintains excellent electrical interconnection among nanoparticles and results in large surface areas and many catalytically active sites. We demonstrate that lithium-induced ultra-small NiFeOx nanoparticles are active bifunctional catalysts exhibiting high activity and stability for overall water splitting in base. We achieve 10 mA cm−2 water-splitting current at only 1.51 V for over 200 h without degradation in a two-electrode configuration and 1 M KOH, better than the combination of iridium and platinum as benchmark catalysts. PMID:26099250

  6. Microwave irradiated Ni-MnOx/C as an electrocatalyst for methanol oxidation in KOH solution for fuel cell application

    NASA Astrophysics Data System (ADS)

    Hameed, R. M. Abdel

    2015-12-01

    Ni-MnOx/C electrocatalyst was synthesized by the reduction of nickel precursor salt on MnOx/C powder using NaBH4 and the deposition process was motivated with the aid of microwave irradiation. Finer nickel nanoparticles were detected in Ni-MnOx/C using transmission electron microscopy with a lower particle size of 4.5 nm compared to 6 nm in Ni/C. Cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy (EIS) were applied to study the electrocatalytic activity of Ni-MnOx/C for methanol oxidation in 0.5 M KOH solution. The presence of 7.5 wt.% MnOx in Ni-MnOx/C enhanced the oxidation current density by 1.43 times. The catalytic rate constant of methanol oxidation at Ni-MnOx/C was calculated as 3.26 × 103 cm3 mol-1 s-1. An appreciable shift in the maximum frequency at the transition from the resistive to capacitive regions to a higher value in Bode plots of Ni-MnOx/C was shown when compared to Ni/C. It was accompanied by lowered phase angle values. The lowered Warburg impedance value (W) of Ni-MnOx/C at 400 mV confirmed the faster methanol diffusion rate at its surface.

  7. Magnesiothermic synthesis of sulfur-doped graphene as an efficient metal-free electrocatalyst for oxygen reduction

    PubMed Central

    Wang, Jiacheng; Ma, Ruguang; Zhou, Zhenzhen; Liu, Guanghui; Liu, Qian

    2015-01-01

    Efficient metal-free electrocatalysts for oxygen reduction reaction (ORR) are highly expected in future low-cost energy systems. We have successfully prepared crumpled, sheet-like, sulfur-doped graphene by magnesiothermic reduction of easily available, low-cost, nontoxic CO2 (in the form of Na2CO3) and Na2SO4 as the carbon and sulfur sources, respectively. At high temperature, Mg can reduce not only carbon in the oxidation state of +4 in CO32− to form graphene, but also sulfur in SO42− from its highest (+6) to lowest valence which was hybridized into the carbon sp2 framework. Various characterization results show that sulfur-doped graphene with only few layers has an appropriate sulfur content, hierarchically robust porous structure, large surface area/pore volume, and highly graphitized textures. The S-doped graphene samples exhibit not only a high activity for ORR with a four-electron pathway, but also superior durability and tolerance to MeOH crossover to 40% Pt/C. This is mainly ascribed to the combination of sulfur-related active sites and hierarchical porous textures, facilitating fast diffusion of oxygen molecules and electrolyte to catalytic sites and release of products from the sites. PMID:25790856

  8. Controllable synthesis of mesoporous carbon nanospheres and Fe-N/carbon nanospheres as efficient oxygen reduction electrocatalysts.

    PubMed

    Wei, Jing; Liang, Yan; Zhang, Xinyi; Simon, George P; Zhao, Dongyuan; Zhang, Jin; Jiang, Sanping; Wang, Huanting

    2015-04-14

    The synthesis of mesoporous carbon nanospheres (MCNs), especially with diameters below 200 nm remains a great challenge due to weak interactions between the carbon precursors and soft templates, as well as the uncontrollable cross-linking rate of carbon precursors. Herein, we demonstrate a simple acid-assisted, hydrothermal synthesis approach to synthesizing such uniform MCNs with well controlled diameters ranging from 20 to 150 nm under highly acidic conditions (2 M HCl). Both the carbon precursor and the template are partly protonated under such conditions and show additional Coulombic interactions with chloride ions (acts as mediators). This kind of enhanced interaction is similar to that of the "I(+)X(-)S(+)" mechanism in the synthesis of mesoporous metal oxide, which can effectively retard the cross-linking rate of resol molecules and avoid macroscopic phase separation during the hydrothermal synthesis. Due to their uniform spherical morphology, small diameter, and high surface areas, MCNs can be modified with Fe and N species via impregnation of cheap precursors (ferric nitrate and dicyandiamide), which are further converted into nonprecious electrocatalysts for oxygen reduction reactions. The resulting Fe-N/MCNs exhibit high catalytic activities, long-term stability and improved methanol tolerance under alkaline conditions, which can be potentially used in direct methanol fuel cells and metal-air batteries. PMID:25779978

  9. Engineering self-assembled N-doped graphene-carbon nanotube composites towards efficient oxygen reduction electrocatalysts.

    PubMed

    Zhang, Yun; Jiang, Wen-Jie; Zhang, Xing; Guo, Lin; Hu, Jin-Song; Wei, Zidong; Wan, Li-Jun

    2014-07-21

    The importance of the oxygen reduction reaction (ORR) in fuel cells and high energy density metal-air batteries has attracted intense research interests in looking for low-cost ORR catalysts as substitutes for expensive and scarce Pt-based catalysts. N-doped graphene and carbon nanotubes prepared in a low-cost and scalable way have demonstrated their potential although the performance still needs to be improved. In view of the requirements for a high-performance ORR electrocatalyst, this work focused on developing the nanocomposites of N-doped reduced graphene oxide (N-rGO) and N-doped carbon nanotubes (N-CNT) as low-cost efficient ORR catalysts by integrating the advantages of abundant highly-active sites from N-rGO and a three-dimensional conductive network for efficient mass and electron transport from N-CNT. By optimizing the preparation method and dedicatedly tuning the composition, the much enhanced ORR activity and superior durability and tolerance to methanol were achieved for the self-assembled N-doped composite (N-rGO-CNT) at a mass ratio of 1 : 5 rGO/CNT. Further improvement of the ORR electrocatalytic activity of the composite was also demonstrated by introducing iron into the composite. PMID:24722811

  10. Kinetic study of the hydrogen oxidation reaction on sub-stoichiometric titanium oxide-supported platinum electrocatalyst in acid solution

    NASA Astrophysics Data System (ADS)

    Babić, B.; Gulicovski, J.; Gajić-Krstajić, Lj.; Elezović, N.; Radmilović, V. R.; Krstajić, N. V.; Vračar, Lj. M.

    The kinetics and mechanism of the hydrogen oxidation reaction were studied in 0.5 mol dm -3 HClO 4 solution on an electrode based on titanium oxide with Magneli phase structure-supported platinum electrocatalyst applied on rotation Au disk electrode. Pt catalyst was prepared by impregnation method from 2-propanol solution of Pt(NH 3) 2(NO 2) 2 and sub-stoichiometric titanium oxide powder. Sub-stiochiometric titanium oxide support was characterized by X-ray diffraction and BET techniques. The synthesized catalyst was analyzed by TEM technique. Based on Tafel-Heyrovsky-Volmer mechanism the corresponding kinetic equations were derived to describe the hydrogen oxidation current-potential behavior on RDE over the entire potential region. The polarization RDE curves were fitted with derived polarization equations according to proposed model. The fitting shows that the HOR on Pt proceeds most likely via the Tafel-Volmer (TV) pathway in the lower potential region, while the Heyrovsky-Volmer (HV) pathway is operative in the higher potential region. It is pointed out that Tafel equation that has been frequently used for the kinetics analysis in the HOR, can not reproduce the polarization curves measured with high mass-transport rates. Polarization measurements on RDE revealed that the Pt catalyst deposited on titanium suboxide support showed equal specific activity for the HOR compared to conventional carbon-supported Pt fuel cell catalyst.

  11. Hierarchically porous Fe-N-C derived from covalent-organic materials as a highly efficient electrocatalyst for oxygen reduction.

    PubMed

    Zuo, Quan; Zhao, Pingping; Luo, Wei; Cheng, Gongzhen

    2016-08-01

    Developing high-performance non-precious catalysts to replace platinum as oxygen reduction reaction (ORR) catalysts is still a big scientific and technological challenge. Herein, we report a simple method for the synthesis of a FeNC catalyst with a 3D hierarchically micro/meso/macro porous network and high surface area through a simple carbonization method by taking the advantages of a high specific surface area and diverse pore dimensions in 3D porous covalent-organic material. The resulting FeNC-900 electrocatalyst with improved reactant/electrolyte transport and sufficient active site exposure, exhibits outstanding ORR activity with a half-wave potential of 0.878 V, ca. 40 mV more positive than Pt/C for ORR in alkaline solution, and a half-wave potential of 0.72 V, which is comparable to that of Pt/C in acidic solution. In particular, the resulting FeNC-900 exhibits a much higher stability and methanol tolerance than those of Pt/C, which makes it among the best non-precious catalysts ever reported for ORR. PMID:27405086

  12. A Synthetic Nickel Electrocatalyst With a Turnover Frequency Above 100,000 s-1 for H2 Production

    SciTech Connect

    Helm, Monte L.; Stewart, Michael P.; Bullock, R. Morris; Rakowski DuBois, Mary; DuBois, Daniel L.

    2011-08-12

    Increased worldwide energy demand will require greater use of carbon-neutral sustainable energy sources. The intermittent nature of solar and wind power requires storage of energy, so electrocatalysts that convert electrical energy to chemical bonds in fuels are needed. Platinum is an excellent catalyst, but it is of low abundance and high cost. Hydrogenase enzymes in Nature catalyze the evolution of H2 and use earth-abundant metals such as nickel and iron. We report that a synthetic nickel catalyst, [Ni(7PPh2NPh)2](BF4)2, (7PPh2NPh = 1,3,6-triphenyl-1-aza-3,6-diphosphacycloheptane) catalyzes the production of H2 using [(DMF)H]+OTf as the proton source, with turnover frequencies of 31,000 s-1 in dry acetonitrile and 108,000 s-1 in the presence of H2O (1.2 M), at a potential of -1.13 V (vs. the ferrocenium/ferrocene couple). These turnover frequencies exceed those reported for the [FeFe] hydrogenase enzyme by more than an order of magnitude, and are the fastest reported for any molecular catalyst for H2 production. This material is based upon work supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the US Department of Energy, Office of Science, Office of Basic Energy Sciences.

  13. Low Pt-Loaded Mesoporous Sodium Germanate as a High-Performance Electrocatalyst for the Oxygen Reduction Reaction.

    PubMed

    Zhou, Xiaoxia; Chen, Lisong; Wan, Gang; Chen, Yu; Kong, Qinglu; Chen, Hangrong; Shi, Jianlin

    2016-09-01

    Although Pt/C catalysts show relatively high activities for the oxygen reduction reaction (ORR) and great potential for use in polymer electrolyte membrane fuel cells, the large amount of Pt required and the poor stability of Pt/C-based catalysts remain big challenges. Herein, mesoporous Na4 Ge9 O20 micro-crystals have been successfully synthesized to serve as a new kind of electrocatalyst support owing to its special structural characteristics and high structural stability. After loading a low amount of Pt (5 wt %) nanoparticles of 2-5 nm in diameter, the obtained mesoporous Pt/Na4 Ge9 O20 composite shows not only high electrocatalytic activity for ORR in both acidic and alkaline electrolyte media, which are comparable to those of conventional 20 wt % Pt/C, but also remarkably enhanced Pt mass-specified ORR current density and durability. Synergetic catalytic effects between loaded Pt and the support for the ORR activity has been proposed. PMID:27539826

  14. Synthesis of halogen-doped reduced graphene oxide nanosheets as highly efficient metal-free electrocatalyst for oxygen reduction reaction.

    PubMed

    Kakaei, Karim; Balavandi, Amin

    2016-02-01

    We demonstrate F-, Cl-, Br- and I-doped reduced graphene oxide (XRGO) as metal-free graphene electro-catalysts for oxygen reduction reaction (ORR) in alkaline media. Reduced graphene oxide (GO) is prepared from graphite electrode using electrochemical exfoliation. In situ doping of halide in a graphene film has many problems. In this technique, different halides individually or all of them were mixed with the RGO and ionic liquids precursor at H2SO4 solution. Then we have evaluated the effectiveness of doping and performed electrochemical measurements of the ORR activity on XRGO. Fourier-transform infrared spectroscopy spectra show a variety of the halogen-containing functional groups. Energy-dispersive X-ray spectroscopy analysis confirmed the presence of doped halogens in RGO. Raman spectroscopy shows a high density of defects in the RGO layer. The electrochemical properties of the XRGO catalysts on carbon paper as a gas diffusion electrode (GDE) are investigated by several electrochemical methods in oxygen saturated alkaline solutions. The catalytic activity of the XRGO and Pt-C electrodes for ORR is 50 and 30mAcm(-2) at -1V in GDEs. This enhanced efficiency is the result of the influence of the nature and percentage of the halogen, especially fluorine presence in the graphene layer. PMID:26513736

  15. Simultaneous H2 Generation and Biomass Upgrading in Water by an Efficient Noble-Metal-Free Bifunctional Electrocatalyst.

    PubMed

    You, Bo; Jiang, Nan; Liu, Xuan; Sun, Yujie

    2016-08-16

    As an environmentally friendly approach to generate H2 , electrocatalytic water splitting has attracted worldwide interest. However, its broad employment has been inhibited by costly catalysts and low energy conversion efficiency, mainly due to the sluggish anodic half reaction, the O2 evolution reaction (OER), whose product O2 is not of significant value. Herein, we report an efficient strategy to replace OER with a thermodynamically more favorable reaction, the oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA), catalyzed by 3D Ni2 P nanoparticle arrays on nickel foam (Ni2 P NPA/NF). HMF is one of the primary dehydration intermediates of raw biomass and FDCA is of many industrial applications. As a bifunctional electrocatalyst, Ni2 P NPA/NF is not only active for HMF oxidation but also competent for H2 evolution. In fact, a two-electrode electrolyzer employing Ni2 P NPA/NF for simultaneous H2 and FDCA production required a voltage at least 200 mV smaller compared with pure water splitting to achieve the same current density, as well as exhibiting robust stability and nearly unity Faradaic efficiencies. PMID:27417546

  16. Magnesiothermic synthesis of sulfur-doped graphene as an efficient metal-free electrocatalyst for oxygen reduction

    NASA Astrophysics Data System (ADS)

    Wang, Jiacheng; Ma, Ruguang; Zhou, Zhenzhen; Liu, Guanghui; Liu, Qian

    2015-03-01

    Efficient metal-free electrocatalysts for oxygen reduction reaction (ORR) are highly expected in future low-cost energy systems. We have successfully prepared crumpled, sheet-like, sulfur-doped graphene by magnesiothermic reduction of easily available, low-cost, nontoxic CO2 (in the form of Na2CO3) and Na2SO4 as the carbon and sulfur sources, respectively. At high temperature, Mg can reduce not only carbon in the oxidation state of +4 in CO32- to form graphene, but also sulfur in SO42- from its highest (+6) to lowest valence which was hybridized into the carbon sp2 framework. Various characterization results show that sulfur-doped graphene with only few layers has an appropriate sulfur content, hierarchically robust porous structure, large surface area/pore volume, and highly graphitized textures. The S-doped graphene samples exhibit not only a high activity for ORR with a four-electron pathway, but also superior durability and tolerance to MeOH crossover to 40% Pt/C. This is mainly ascribed to the combination of sulfur-related active sites and hierarchical porous textures, facilitating fast diffusion of oxygen molecules and electrolyte to catalytic sites and release of products from the sites.

  17. Effects of cobalt precursor on pyrolyzed carbon-supported cobalt-polypyrrole as electrocatalyst toward oxygen reduction reaction

    PubMed Central

    2013-01-01

    A series of non-precious metal electrocatalysts, namely pyrolyzed carbon-supported cobalt-polypyrrole, Co-PPy-TsOH/C, are synthesized with various cobalt precursors, including cobalt acetate, cobalt nitrate, cobalt oxalate, and cobalt chloride. The catalytic performance towards oxygen reduction reaction (ORR) is comparatively investigated with electrochemical techniques of cyclic voltammogram, rotating disk electrode and rotating ring-disk electrode. The results are analyzed and discussed employing physiochemical techniques of X-ray diffraction, transmission electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, inductively coupled plasma, elemental analysis, and extended X-ray absorption fine structure. It shows that the cobalt precursor plays an essential role on the synthesis process as well as microstructure and performance of the Co-PPy-TsOH/C catalysts towards ORR. Among the studied Co-PPy-TsOH/C catalysts, that prepared with cobalt acetate exhibits the best ORR performance. The crystallite/particle size of cobalt and its distribution as well as the graphitization degree of carbon in the catalyst greatly affects the catalytic performance of Co-PPy-TsOH/C towards ORR. Metallic cobalt is the main component in the active site in Co-PPy-TsOH/C for catalyzing ORR, but some other elements such as nitrogen are probably involved, too. PMID:24229351

  18. Self-Supported Cu-Based Nanowire Arrays as Noble-Metal-Free Electrocatalysts for Oxygen Evolution.

    PubMed

    Hou, Chun-Chao; Fu, Wen-Fu; Chen, Yong

    2016-08-23

    Crystalline Cu-based nanowire arrays (NWAs) including Cu(OH)2 , CuO, Cu2 O, and CuOx are facilely grown on Cu foil and are found to act as highly efficient, low-cost, and robust electrocatalysts for the oxygen evolution reaction (OER). Impressively, this noble-metal-free 3 D Cu(OH)2 -NWAs/Cu foil electrode shows the highest catalytic activity with a Tafel slope of 86 mV dec(-1) , an overpotential (η) of about 530 mV at ∼10 mA cm(-2) (controlled-potential electrolysis method without iR correction) and almost 100 % Faradic efficiency, paralleling the performance of the state-of-the-art RuO2 OER catalyst in 0.1 m NaOH solution (pH 12.8). To the best of our knowledge, this work represents one of the best results ever reported on Cu-based OER systems. PMID:27440473

  19. Effects of cobalt precursor on pyrolyzed carbon-supported cobalt-polypyrrole as electrocatalyst toward oxygen reduction reaction.

    PubMed

    Yuan, Xianxia; Hu, Xin-Xin; Ding, Xin-Long; Kong, Hai-Chuan; Sha, Hao-Dong; Lin, He; Wen, Wen; Shen, Guangxia; Guo, Zhi; Ma, Zi-Feng; Yang, Yong

    2013-01-01

    A series of non-precious metal electrocatalysts, namely pyrolyzed carbon-supported cobalt-polypyrrole, Co-PPy-TsOH/C, are synthesized with various cobalt precursors, including cobalt acetate, cobalt nitrate, cobalt oxalate, and cobalt chloride. The catalytic performance towards oxygen reduction reaction (ORR) is comparatively investigated with electrochemical techniques of cyclic voltammogram, rotating disk electrode and rotating ring-disk electrode. The results are analyzed and discussed employing physiochemical techniques of X-ray diffraction, transmission electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, inductively coupled plasma, elemental analysis, and extended X-ray absorption fine structure. It shows that the cobalt precursor plays an essential role on the synthesis process as well as microstructure and performance of the Co-PPy-TsOH/C catalysts towards ORR. Among the studied Co-PPy-TsOH/C catalysts, that prepared with cobalt acetate exhibits the best ORR performance. The crystallite/particle size of cobalt and its distribution as well as the graphitization degree of carbon in the catalyst greatly affects the catalytic performance of Co-PPy-TsOH/C towards ORR. Metallic cobalt is the main component in the active site in Co-PPy-TsOH/C for catalyzing ORR, but some other elements such as nitrogen are probably involved, too. PMID:24229351

  20. Palladium-platinum core-shell electrocatalysts for oxygen reduction reaction prepared with the assistance of citric acid

    DOE PAGESBeta

    Zhang, Lulu; Su, Dong; Zhu, Shangqian; Chang, Qiaowan; Yue, Jeffrey; Du, Zheng; Shao, Minhua

    2016-04-26

    Core–shell structure is a promising alternative to solid platinum (Pt) nanoparticles as electrocatalyst for oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs). A simple method of preparing palladium (Pd)–platinum (Pt) core–shell catalysts (Pd@Pt/C) in a gram-batch was developed with the assistance of citric acid. The Pt shell deposition involves three different pathways: galvanic displacement reaction between Pd atoms and Pt cations, chemical reduction by citric acid, and reduction by negative charges on Pd surfaces. The uniform ultrathin (~0.4 nm) Pt shell was characterized by in situ X-ray diffraction (XRD) and high-angle annular dark-field scanning transmission electron microscopymore » (HAADF-STEM) images combined with electron energy loss spectroscopy (EELS). Compared with state-of-the-art Pt/C, the Pd@Pt/C core–shell catalyst showed 4 times higher Pt mass activity and much better durability upon potential cycling. As a result, both the mass activity and durability were comparable to that of Pd@Pt/C synthesized by a Cu-mediated-Pt-displacement method, which is more complicated and difficult for mass production.« less

  1. High-index faceted Ni3S2 nanosheet arrays as highly active and ultrastable electrocatalysts for water splitting.

    PubMed

    Feng, Liang-Liang; Yu, Guangtao; Wu, Yuanyuan; Li, Guo-Dong; Li, Hui; Sun, Yuanhui; Asefa, Tewodros; Chen, Wei; Zou, Xiaoxin

    2015-11-11

    Elaborate design of highly active and stable catalysts from Earth-abundant elements has great potential to produce materials that can replace the noble-metal-based catalysts commonly used in a range of useful (electro)chemical processes. Here we report, for the first time, a synthetic method that leads to in situ growth of {2̅10} high-index faceted Ni3S2 nanosheet arrays on nickel foam (NF). We show that the resulting material, denoted Ni3S2/NF, can serve as a highly active, binder-free, bifunctional electrocatalyst for both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). Ni3S2/NF is found to give ∼100% Faradaic yield toward both HER and OER and to show remarkable catalytic stability (for >200 h). Experimental results and theoretical calculations indicate that Ni3S2/NF's excellent catalytic activity is mainly due to the synergistic catalytic effects produced in it by its nanosheet arrays and exposed {2̅10} high-index facets. PMID:26352297

  2. Facile fabrication of palladium-ionic liquids-nitrogen-doped graphene nanocomposites as enhanced electro-catalyst for ethanol oxidation

    NASA Astrophysics Data System (ADS)

    Li, Shuwen; Yang, Honglei; Ren, Ren; Ma, Jianxin; Jin, Jun; Ma, Jiantai

    2015-10-01

    The palladium-ionic liquids-nitrogen-doped graphene nanocomposites are facile fabricated as enhanced electro-catalyst for ethanol oxidation. First, the ionic liquids functionalized nitrogen-doping graphene nanosheets (PDIL-NGS) with few layers is synthesized through a facile and effective one-pot hydrothermal method with graphene oxide as raw material, urea as reducing-doping agents and ionic liquids (ILs) derived from 3,4,9,10-perylene tetracarboxylic acid as functional molecules. The results of systematic characterization reveal that the PDIL molecules not only can functionalize NGS by π-π stacking with no affecting the nitrogen doping but also prevent the agglomeration of NGS. More importantly, the processing performance and the property of electron transfer are remarkably enhanced duo to introducing a large number of ILs groups. Then, the enhanced electrocatalytic Pd nanoparticles are successfully anchored on PDIL-NGS by a facile and surfactant-free synthetic technique. As an anode catalyst, the novel catalyst exhibits better kinetics, more superior electrocatalytic performance, higher tolerance and electrochemical stability than the other catalysts toward ethanol electrooxidation, owing to the role of PDIL molecules. Therefore, the new catalyst is believed to have the potential use for direct alcohol fuel cells in the future and the functionalized NGS is promising useful materials applied in other fields.

  3. CO2 Reduction to CO in Water: Carbon Nanotube-Gold Nanohybrid as a Selective and Efficient Electrocatalyst.

    PubMed

    Huan, Tran Ngoc; Prakash, Praveen; Simon, Philippe; Rousse, Gwenaëlle; Xu, X; Artero, Vincent; Gravel, Edmond; Doris, Eric; Fontecave, Marc

    2016-09-01

    A gold-based nanostructure has been demonstrated as promising materials for the selective electroreduction of CO2 to CO in aqueous conditions. In this work, we present a carbon nanotube-gold nanohybrid as a selective and efficient electrocatalyst for the reduction of CO2 in 0.5 m NaHCO3 . The hybrid material exhibits remarkable activity with a current density of 10 mA cm(-2) at -0.55 V versus standard hydrogen electrode with a stable CO production rate (0.52 μmol s(-1) ) after 4 h electrolysis. Monodispersed gold nanoparticles anchored on carbon nanotubes through a layer-by-layer method allows very little Au loading and thus minimization of the cost of electrode fabrication with a mass activity up to 100 A g(-1) at -0.55 V versus reversible hydrogen electrode. It is 33 times higher than a previous report for monodisperse Au nanoparticles (3 A g(-1) ) while ensuring selectivity (70 % faradaic yield of CO) at comparable reduction potential. PMID:27492905

  4. Enhancement of Platinum Mass Activity on the Surface of Polymer-wrapped Carbon Nanotube-Based Fuel Cell Electrocatalysts

    PubMed Central

    Hafez, Inas H.; Berber, Mohamed R.; Fujigaya, Tsuyohiko; Nakashima, Naotoshi

    2014-01-01

    Cost reduction and improved durability are the two major targets for accelerating the commercialization of polymer electrolyte membrane fuel cells (PEFCs). To achieve these goals, the development of a novel method to fabricate platinum (Pt)-based electrocatalysts with a high mass activity, deposited on durable conductive support materials, is necessary. In this study, we describe a facile approach to grow homogeneously dispersed Pt nanoparticles (Pt) with a narrow diameter distribution in a highly controllable fashion on polymer-wrapped carbon nanotubes (CNTs). A PEFC cell employing a composite with the smallest Pt nanoparticle size (2.3 nm diameter) exhibited a ~8 times higher mass activity compared to a cell containing Pt with a 3.7 nm diameter. This is the first example of the diamter control of Pt on polymer-wrapped carbon supporting materials, and the study opens the door for the development of a future-generation of PEFCs using a minimal amount of Pt. PMID:25221915

  5. Highly active and stable hydrogen evolution electrocatalysts based on molybdenum compounds on carbon nanotube-graphene hybrid support.

    PubMed

    Youn, Duck Hyun; Han, Suenghoon; Kim, Jae Young; Kim, Jae Yul; Park, Hunmin; Choi, Sun Hee; Lee, Jae Sung

    2014-05-27

    Highly active and stable electrocatalysts for hydrogen evolution have been developed on the basis of molybdenum compounds (Mo2C, Mo2N, and MoS2) on carbon nanotube (CNT)-graphene hybrid support via a modified urea-glass route. By a simple modification of synthetic variables, the final phases are easily controlled from carbide, nitride to sulfide with homogeneous dispersion of nanocrystals on the CNT-graphene support. Among the prepared catalysts, Mo2C/CNT-graphene shows the highest activity for hydrogen evolution reaction with a small onset overpotential of 62 mV and Tafel slope of 58 mV/dec as well as an excellent stability in acid media. Such enhanced catalytic activity may originate from its low hydrogen binding energy and high conductivity. Moreover, the CNT-graphene hybrid support plays crucial roles to enhance the activity of molybdenum compounds by alleviating aggregation of the nanocrystals, providing a large area to contact with electrolyte, and facilitating the electron transfer. PMID:24787540

  6. Novel Flower-like Nickel Sulfide as an Efficient Electrocatalyst for Non-aqueous Lithium-Air Batteries.

    PubMed

    Ma, Zhong; Yuan, Xianxia; Zhang, Zhenlin; Mei, Delong; Li, Lin; Ma, Zi-Feng; Zhang, Lei; Yang, Jun; Zhang, Jiujun

    2015-01-01

    In this paper, metal sulfide materials have been explored for the first time as a new choice of bifunctional cathode electrocatalyst materials for non-aqueous lithium-air batteries (LABs). Nickel sulfides with two different morphologies of flower-like (f-NiS) and rod-like (r-NiS) are successfully synthesized using a hydrothermal method with and without the assistance of cetyltrimethyl ammonium bromide. As LAB cathode catalysts, both f-NiS and r-NiS demonstrate excellent catalytic activities towards the formation and decomposition of Li2O2, resulting in improved specific capacity, reduced overpotentials and enhanced cycling performance when compared to those of pure Super P based electrode. Moreover, the morphology of NiS materials can greatly affect LAB performance. Particularly, the f-NiS is more favorable than r-NiS in terms of their application in LABs. When compared to both r-NiS and pure super P materials as LAB cathode materials, this f-NiS catalyst material can give the highest capacity of 6733 mA h g(-1) and the lowest charge voltage of 4.24 V at the current density of 75 mA g(-1) and also exhibit an quite stable cycling performance. PMID:26658833

  7. Novel Flower-like Nickel Sulfide as an Efficient Electrocatalyst for Non-aqueous Lithium-Air Batteries

    NASA Astrophysics Data System (ADS)

    Ma, Zhong; Yuan, Xianxia; Zhang, Zhenlin; Mei, Delong; Li, Lin; Ma, Zi-Feng; Zhang, Lei; Yang, Jun; Zhang, Jiujun

    2015-12-01

    In this paper, metal sulfide materials have been explored for the first time as a new choice of bifunctional cathode electrocatalyst materials for non-aqueous lithium-air batteries (LABs). Nickel sulfides with two different morphologies of flower-like (f-NiS) and rod-like (r-NiS) are successfully synthesized using a hydrothermal method with and without the assistance of cetyltrimethyl ammonium bromide. As LAB cathode catalysts, both f-NiS and r-NiS demonstrate excellent catalytic activities towards the formation and decomposition of Li2O2, resulting in improved specific capacity, reduced overpotentials and enhanced cycling performance when compared to those of pure Super P based electrode. Moreover, the morphology of NiS materials can greatly affect LAB performance. Particularly, the f-NiS is more favorable than r-NiS in terms of their application in LABs. When compared to both r-NiS and pure super P materials as LAB cathode materials, this f-NiS catalyst material can give the highest capacity of 6733 mA h g-1 and the lowest charge voltage of 4.24 V at the current density of 75 mA g-1 and also exhibit an quite stable cycling performance.

  8. Elucidating Oxygen Reduction Active Sites in Pyrolyzed Metal–Nitrogen Coordinated Non-Precious-Metal Electrocatalyst Systems

    PubMed Central

    2015-01-01

    Detailed understanding of the nature of the active centers in non-precious-metal-based electrocatalyst, and their role in oxygen reduction reaction (ORR) mechanistic pathways will have a profound effect on successful commercialization of emission-free energy devices such as fuel cells. Recently, using pyrolyzed model structures of iron porphyrins, we have demonstrated that a covalent integration of the Fe–Nx sites into π-conjugated carbon basal plane modifies electron donating/withdrawing capability of the carbonaceous ligand, consequently improving ORR activity. Here, we employ a combination of in situ X-ray spectroscopy and electrochemical methods to identify the various structural and functional forms of the active centers in non-heme Fe/N/C catalysts. Both methods corroboratively confirm the single site 2e– × 2e– mechanism in alkaline media on the primary Fe2+–N4 centers and the dual-site 2e– × 2e– mechanism in acid media with the significant role of the surface bound coexisting Fe/FexOy nanoparticles (NPs) as the secondary active sites. PMID:24817921

  9. Fabrication of iron-doped cobalt oxide nanocomposite films by electrodeposition and application as electrocatalyst for oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Zhang, Jingxuan; Wang, Xuemei; Qin, Dongdong; Xue, Zhonghua; Lu, Xiaoquan

    2014-11-01

    In this work, Fe-doped Co3O4 nanofilms were fabricated by electrodeposition on FTO glass substrates for the first time. The structures of the as-prepared nanofilms were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Characterization results demonstrate that Fe was doped homogeneously in the nanofilms. As the different concentration ratios of Fe2+/Co2+ were explored, nanofilm with the ratio of 1:5 exhibits the optimal performance in electrochemical properties assessments. It is considered that the difference in the catalytic activities for the ORR of the samples may be due to the fact that the joining of iron changed the catalyst surface's electric state and enhanced the acidity of cobalt centers, on the other hand, the doping process probably modified the absorption property of the nanofilms. The experimental results suggest that the Fe-doped Co3O4 nanofilms in this work exhibit favorable electrocatalytic activity toward ORR and appear to be promising cathodic electrocatalyst in alkaline fuel cells.

  10. Cobalt sulfide/N,S codoped porous carbon core-shell nanocomposites as superior bifunctional electrocatalysts for oxygen reduction and evolution reactions

    NASA Astrophysics Data System (ADS)

    Chen, Binling; Li, Rong; Ma, Guiping; Gou, Xinglong; Zhu, Yanqiu; Xia, Yongde

    2015-12-01

    Exploring highly-efficient and low-cost bifunctional electrocatalysts for both oxygen reduction reaction (ORR) and oxygen evolution reactions (OER) in the renewable energy area has gained momentum but still remains a significant challenge. Here we present a simple but efficient method that utilizes ZIF-67 as the precursor and template for the one-step generation of homogeneous dispersed cobalt sulfide/N,S-codoped porous carbon nanocomposites as high-performance electrocatalysts. Due to the favourable molecular-like structural features and uniform dispersed active sites in the precursor, the resulting nanocomposites, possessing a unique core-shell structure, high porosity, homogeneous dispersion of active components together with N and S-doping effects, not only show excellent electrocatalytic activity towards ORR with the high onset potential (around -0.04 V vs. -0.02 V for the benchmark Pt/C catalyst) and four-electron pathway and OER with a small overpotential of 0.47 V for 10 mA cm-2 current density, but also exhibit superior stability (92%) to the commercial Pt/C catalyst (74%) in ORR and promising OER stability (80%) with good methanol tolerance. Our findings suggest that the transition metal sulfide-porous carbon nanocomposites derived from the one-step simultaneous sulfurization and carbonization of zeolitic imidazolate frameworks are excellent alternative bifunctional electrocatalysts towards ORR and OER in the next generation of energy storage and conversion technologies.Exploring highly-efficient and low-cost bifunctional electrocatalysts for both oxygen reduction reaction (ORR) and oxygen evolution reactions (OER) in the renewable energy area has gained momentum but still remains a significant challenge. Here we present a simple but efficient method that utilizes ZIF-67 as the precursor and template for the one-step generation of homogeneous dispersed cobalt sulfide/N,S-codoped porous carbon nanocomposites as high-performance electrocatalysts. Due to the

  11. Exploring the first steps in core-shell electrocatalyst preparation: in situ characterization of the underpotential deposition of Cu on supported Au nanoparticles.

    PubMed

    Price, Stephen W T; Speed, Jonathon D; Kannan, Prabalini; Russell, Andrea E

    2011-12-01

    The underpotential deposition (upd) of a Cu shell on a non-Pt nanoparticle core followed by galvanic displacement of the Cu template shell to form core-shell electrocatalyst materials is one means by which the Pt-based mass activity targets required for commercialization of PEM fuel cells may be reached. In situ EXAFS measurements were conducted at both the Au L(3) and the Cu K absorption edges during deposition of Cu onto a carbon-supported Au electrocatalyst to study the initial stages of formation of such a core-shell electrocatalyst. The Au L(3) EXAFS data obtained in 0.5 mol dm(-3) H(2)SO(4) show that the shape of the Au core is potential dependent, from a flattened to a round spherical shape as the Cu upd potential is approached. Following the addition of 2 mmol dm(-3) Cu, the structure was also measured as a function of the applied potential. At +0.2 V vs Hg/Hg(2)SO(4), the Cu(2+) species was found to be a hydrated octahedron. As the potential was made more negative, single-crystal studies predict an ordered bilayer of sulfate anions and partially discharged Cu ions, followed by a complete/uniform layer of Cu atoms. In contrast, the model obtained by fitting the Au L(3) and Cu K EXAFS data corresponds first to partially discharged Cu ions deposited at the defect sites in the outer shell of the Au nanoparticles at -0.42 V, followed by the growth of clusters of Cu atoms at -0.51 V. The absence of a uniform/complete Cu shell, even at the most negative potentials investigated, has implications for the structure, and the activity and/or stability, of the core-shell catalyst that would be subsequently formed following galvanic displacement of the Cu shell. PMID:22032178

  12. Understanding the High Activity of Fe-N-C Electrocatalysts in Oxygen Reduction: Fe/Fe3C Nanoparticles Boost the Activity of Fe-N(x).

    PubMed

    Jiang, Wen-Jie; Gu, Lin; Li, Li; Zhang, Yun; Zhang, Xing; Zhang, Lin-Juan; Wang, Jian-Qiang; Hu, Jin-Song; Wei, Zidong; Wan, Li-Jun

    2016-03-16

    Understanding the origin of high activity of Fe-N-C electrocatalysts in oxygen reduction reaction (ORR) is critical but still challenging for developing efficient sustainable nonprecious metal catalysts in fuel cells and metal-air batteries. Herein, we developed a new highly active Fe-N-C ORR catalyst containing Fe-N(x) coordination sites and Fe/Fe3C nanocrystals (Fe@C-FeNC), and revealed the origin of its activity by intensively investigating the composition and the structure of the catalyst and their correlations with the electrochemical performance. The detailed analyses unambiguously confirmed the coexistence of Fe/Fe3C nanocrystals and Fe-N(x) in the best catalyst. A series of designed experiments disclosed that (1) N-doped carbon substrate, Fe/Fe3C nanocrystals or Fe-N(x) themselves did not deliver the high activity; (2) the catalysts with both Fe/Fe3C nanocrystals and Fe-N(x) exhibited the high activity; (3) the higher content of Fe-N(x) gave the higher activity; (4) the removal of Fe/Fe3C nanocrystals severely degraded the activity; (5) the blocking of Fe-N(x) downgraded the activity and the recovery of the blocked Fe-N(x) recovered the activity. These facts supported that the high ORR activity of the Fe@C-FeNC electrocatalysts should be ascribed to that Fe/Fe3C nanocrystals boost the activity of Fe-N(x). The coexistence of high content of Fe-N(x) and sufficient metallic iron nanoparticles is essential for the high ORR activity. DFT calculation corroborated this conclusion by indicating that the interaction between metallic iron and Fe-N4 coordination structure favored the adsorption of oxygen molecule. These new findings open an avenue for the rational design and bottom-up synthesis of low-cost highly active ORR electrocatalysts. PMID:26906342

  13. Homogeneous deposition-assisted synthesis of iron-nitrogen composites on graphene as highly efficient non-precious metal electrocatalysts for microbial fuel cell power generation

    NASA Astrophysics Data System (ADS)

    Liu, Yuan; Jin, Xiao-Jun; Dionysiou, Dionysios D.; Liu, Hong; Huang, Yu-Ming

    2015-03-01

    This work proposed a novel strategy for synthesizing highly efficient non-precious metal oxygen reduction reaction (ORR) electrocatalysts. Fe complexes were homogeneously deposited (HD) on graphene oxide through in situ hydrolysis of urea, followed by two-step pyrolysis under Ar and NH3 atmospheres, resulting in formation of Fe- and N-functionalized graphene (HD-FeN/G). The morphology, crystalline structure and elemental composition of HD-FeN/G were characterized. ORR activity was evaluated by using a rotary disk electrode (RDE) electrochemical system. HD improved the loading and distribution of the Fe-Nx composites on graphene. The ORR activity of the as-prepared HD-FeN/G in neutral medium was comparable to that of the state-of-the-art commercial Pt/C and significantly superior to a FeN/G counterpart produced via traditional approach. The ORR electron transfer number of HD-FeN/G was as high as 3.83 ± 0.08, which suggested that ORR catalysis proceeds through a four-electron pathway. HD-FeN/G was used as a cathodic electrocatalyst in microbial fuel cells (MFCs), and the resultant HD-FeN/G-MFC showed comparable voltage output and maximum power density to those of Pt/C-MFC. The HD-FeN/G-MFC achieved a maximum power density of 885 mW m-2, which was much higher than that of FeN/G-MFC (708 mW m-2). These findings demonstrate that HD-FeN/G produced through the novel synthesis strategy proposed in this work would be a good candidate as cathodic electrocatalyst in MFCs.

  14. Core-Shell Co/CoO Integrated on 3D Nitrogen Doped Reduced Graphene Oxide Aerogel as an Enhanced Electrocatalyst for the Oxygen Reduction Reaction.

    PubMed

    Wang, Meng; Hou, Yuyang; Slade, Robert C T; Wang, Jiazhao; Shi, Dongqi; Wexler, David; Liu, Huakun; Chen, Jun

    2016-01-01

    Here, we demonstrate that Cobalt/cobalt oxide core-shell nanoparticles integrated on nitrogen-doped (N-doped) three-dimensional reduced graphene oxide aerogel-based architecture (Co/CoO-NGA) were synthesized through a facile hydrothermal method followed by annealing treatment. The unique endurable porous structure could provide sufficient mass transfer channels and ample active sites on Co/CoO-NGA to facilitate the catalytic reaction. The synthesized Co/CoO-NGA was explored as an electrocatalyst for the oxygen reduction reaction, showing comparable oxygen reduction performance with excellent methanol resistance and better durability compared with Pt/C. PMID:27597939

  15. Nitrogen and fluorine dual-doped mesoporous graphene: a high-performance metal-free ORR electrocatalyst with a super-low HO2(-) yield.

    PubMed

    Jiang, Shu; Sun, Yujing; Dai, Haichao; Hu, Jingting; Ni, Pengjuan; Wang, Yilin; Li, Zhen; Li, Zhuang

    2015-06-28

    In this study, we successfully, for the first time, prepared nitrogen and fluorine dual-doped mesoporous graphene (NF-MG) via the thermal treatment of graphene oxide/polyaniline composites (GO/PANI) and NH4F. Benefiting from the synergistic effect of N and F co-doping into the G framework, the oxygen reduction reaction performance of the optimal catalyst (NF-MG3) is comparable with the-state-of-the-art Pt/C catalyst in an alkaline medium, which makes it an ideal candidate as an efficient metal-free ORR electrocatalyst in fuel cells. PMID:26032909

  16. Core-Shell Co/CoO Integrated on 3D Nitrogen Doped Reduced Graphene Oxide Aerogel as an Enhanced Electrocatalyst for the Oxygen Reduction Reaction

    PubMed Central

    Wang, Meng; Hou, Yuyang; Slade, Robert C. T.; Wang, Jiazhao; Shi, Dongqi; Wexler, David; Liu, Huakun; Chen, Jun

    2016-01-01

    Here, we demonstrate that Cobalt/cobalt oxide core-shell nanoparticles integrated on nitrogen-doped (N-doped) three-dimensional reduced graphene oxide aerogel-based architecture (Co/CoO-NGA) were synthesized through a facile hydrothermal method followed by annealing treatment. The unique endurable porous structure could provide sufficient mass transfer channels and ample active sites on Co/CoO-NGA to facilitate the catalytic reaction. The synthesized Co/CoO-NGA was explored as an electrocatalyst for the oxygen reduction reaction, showing comparable oxygen reduction performance with excellent methanol resistance and better durability compared with Pt/C. PMID:27597939

  17. Shrimp-shell derived carbon nanodots as carbon and nitrogen sources to fabricate three-dimensional N-doped porous carbon electrocatalysts for the oxygen reduction reaction.

    PubMed

    Liu, Rongrong; Zhang, Haimin; Liu, Shengwen; Zhang, Xian; Wu, Tianxing; Ge, Xiao; Zang, Yipeng; Zhao, Huijun; Wang, Guozhong

    2016-02-01

    Development of cheap, abundant and metal-free N-doped carbon materials as high efficiency oxygen reduction electrocatalysts is crucial for their practical applications in future fuel cell devices. Here, three-dimensional (3D) N-doped porous carbon (NPC) materials have been successfully developed by a simple template-assisted (e.g., SiO2 spheres) high temperature pyrolysis approach using shrimp-shell derived N-doped carbon nanodots (N-CNs) as carbon and nitrogen sources obtained through a facile hydrothermal method. The shrimp-shell derived N-CNs with a product yield of ∼ 5% possess rich surface O- and N-containing functional groups and small nanodot sizes of 1.5-5.0 nm, which are mixed with surface acidification treated SiO2 spheres with an average diameter of ∼ 200 nm in aqueous solution to form a N-CNs@SiO2 composite subjected to a thermal evaporation treatment. The resultant N-CNs@SiO2 composite is further thermally treated in a N2 atmosphere at different pyrolysis temperatures, followed by acid etching, to obtain 3D N-doped porous carbon (NPC) materials. As electrocatalysts for oxygen reduction reaction (ORR) in alkaline media, the experimental results demonstrate that 3D NPC obtained at 800 °C (NPC-800) with a surface area of 360.2 m(2) g(-1) exhibits the best ORR catalytic activity with an onset potential of -0.06 V, a half wave potential of -0.21 V and a large limiting current density of 5.3 mA cm(-2) (at -0.4 V, vs. Ag/AgCl) among all NPC materials investigated, comparable to that of the commercial Pt/C catalyst with an onset potential of -0.03 V, a half wave potential of -0.17 V and a limiting current density of 5.5 mA cm(-2) at -0.4 V. Such a 3D porous carbon ORR electrocatalyst also displays superior durability and high methanol tolerance in alkaline media, apparently better than the commercial Pt/C catalyst. The findings of this work would be valuable for the development of low-cost and abundant N-doped carbon materials from biomass as high

  18. Molecular electrocatalysts for oxidation of hydrogen using earth-abundant metals: shoving protons around with proton relays.

    PubMed

    Bullock, R Morris; Helm, Monte L

    2015-07-21

    Sustainable, carbon-neutral energy is needed to supplant the worldwide reliance on fossil fuels in order to address the persistent problem of increasing emissions of CO2. Solar and wind energy are intermittent, highlighting the need to develop energy storage on a huge scale. Electrocatalysts provide a way to convert between electrical energy generated by renewable energy sources and chemical energy in the form of chemical bonds. Oxidation of hydrogen to give two electrons and two protons is carried out in fuel cells, but the typical catalyst is platinum, a precious metal of low earth abundance and high cost. In nature, hydrogenases based on iron or iron/nickel reversibly oxidize hydrogen with remarkable efficiencies and rates. Functional models of these enzymes have been synthesized with the goal of achieving electrocatalytic H2 oxidation using inexpensive, earth-abundant metals along with a key feature identified in the [FeFe]-hydrogenase: an amine base positioned near the metal. The diphosphine ligands P(R)2N(R')2 (1,5-diaza-3,7-diphosphacyclooctane with alkyl or aryl groups on the P and N atoms) are used as ligands in Ni, Fe, and Mn complexes. The pendant amines facilitate binding and heterolytic cleavage of H2, placing the hydride on the metal and the proton on the amine. The pendant amines also serve as proton relays, accelerating intramolecular and intermolecular proton transfers. Electrochemical oxidations and deprotonations by an exogeneous amine base lead to catalytic cycles for oxidation of H2 (1 atm) at room temperature for catalysts derived from [Ni(P(Cy)2N(R')2)2](2+), Cp(C6F5)Fe(P(tBu)2N(Bn)2)H, and MnH(P(Ph)2N(Bn)2)(bppm)(CO) [bppm = (PAr(F)2)2CH2]. In the oxidation of H2 catalyzed by [Ni(P(Cy)2N(R')2)2](2+), the initial product observed experimentally is a Ni(0) complex in which two of the pendant amines are protonated. Two different pathways can occur from this intermediate; deprotonation followed by oxidation occurs with a lower overpotential than

  19. A Modular, Energy-Based Approach to the Development of Nickel Containing Molecular Electrocatalysts for Hydrogen Production and Oxidation

    SciTech Connect

    Shaw, Wendy J.; Helm, Monte L.; DuBois, Daniel L.

    2013-08-01

    This review discusses the development of molecular electrocatalysts for H2 production and oxidation based on nickel. A modular approach is used in which the structure of the catalyst is divided into first second and outer coordination spheres. The first coordination sphere consists of the ligands bound directly to the metal center, and this coordination sphere can be used to control such factors as the presence or absence of vacant coordination sites, redox potentials, hydride acceptor abilities and other important thermodynamic parameters. The second coordination sphere is defined as functional groups such as pendant acids or bases that can interact with bound substrates such as H2 molecules and hydride ligands, but that do not form strong bonds with the metal center. These functional groups can play diverse roles such as assisting the heterolytic cleavage of H2, controlling intra- and intermolecular proton transfer reactions, and provide a physical pathway for coupling proton and electron transfer reactions. By controlling both the hydride donor/acceptor ability of the catalysts using the first coordination sphere and the proton acceptor/donor abilities of the functional groups in the second coordination sphere, catalysts can be designed that are biased toward H2 production, H2 oxidation, or that are bidirectional (catalyzing both H2 oxidation and production). The outer coordination sphere is defined as that portion of the catalytic system that are not in the first and second coordination spheres. This coordination sphere can assist in the delivery of protons and electrons to and from the catalytically active site, thereby adding another important avenue for controlling catalytic activity. Many features of these simple catalytic systems are good models for enzymes and they provide the opportunity to probe certain aspects of catalysis that may be difficult in enzymes themselves, but that can provide insights into enzyme function and reactivity.

  20. Computing Free Energy Landscapes: Application to Ni-based Electrocatalysts with Pendant Amines for H2 Production and Oxidation

    SciTech Connect

    Chen, Shentan; Ho, Ming-Hsun; Bullock, R. Morris; DuBois, Daniel L.; Dupuis, Michel; Rousseau, Roger J.; Raugei, Simone

    2014-01-03

    A general strategy is reported for computational exploration of catalytic pathways of molecular catalysts. Our results are based on a set of linear free energy relationships derived from extensive electronic structure calculations that permit predicting the thermodynamics of intermediates, with accuracy comparable to experimental data. The approach is exemplified with the catalytic oxidation and production of H2 by [Ni(diphosphine)2]2+ electrocatalysts with pendant amines incorporated in the second coordination sphere of the metal center. The analysis focuses upon prediction of thermodynamic properties including reduction potentials, hydride donor abilities, and pKa values of both the protonated Ni center and pendant amine. It is shown that all of these chemical properties can be estimated from the knowledge of only the two redox potentials for the Ni(II)/Ni(I) and Ni(I)/Ni(0) couples of the non-protonated complex, and the pKa of the parent primary aminium ion. These three quantities are easily accessible either experimentally or theoretically. The proposed correlations reveal intimate details about the nature of the catalytic mechanism and its dependence on chemical structure and thermodynamic conditions such as applied external voltage and species concentration. This computational methodology is applied to exploration of possible catalytic pathways, identifying low and high-energy intermediates and, consequently, possibly avoiding bottlenecks associated with undesirable intermediates in the catalytic reactions. We discuss how to optimize some of the critical reaction steps in order to favor catalytically more efficient intermediates. The results of this study highlight the substantial interplay between the various parameters characterizing the catalytic activity, and form the basis needed to optimize the performance of this class of catalysts.

  1. Ultrastable Polymolybdate-Based Metal-Organic Frameworks as Highly Active Electrocatalysts for Hydrogen Generation from Water.

    PubMed

    Qin, Jun-Sheng; Du, Dong-Ying; Guan, Wei; Bo, Xiang-Jie; Li, Ya-Fei; Guo, Li-Ping; Su, Zhong-Min; Wang, Yuan-Yuan; Lan, Ya-Qian; Zhou, Hong-Cai

    2015-06-10

    Two novel polyoxometalate (POM)-based metal-organic frameworks (MOFs), [TBA]3[ε-PMo(V)8Mo(VI)4O36(OH)4Zn4][BTB]4/3·xGuest (NENU-500, BTB = benzene tribenzoate, TBA(+) = tetrabutylammonium ion) and [TBA]3[ε-PMo(V)8Mo(VI)4O37(OH)3Zn4][BPT] (NENU-501, BPT = [1,1'-biphenyl]-3,4',5-tricarboxylate), were isolated. In these compounds, the POM fragments serving as nodes were directly connected with organic ligands giving rise to three-dimensional (3D) open frameworks. The two anionic frameworks were balanced by TBA(+) ions residing inside the open channels. They exhibit not only good stability in air but also tolerance to acidic and basic media. Furthermore, they were employed as electrocatalysts for the hydrogen evolution reaction (HER) owing to the combination of the redox activity of a POM unit and the porosity of a MOF. Meanwhile, the HER activities of ε(trim)(4/3), NENU-5, and HKUST-1 were also studied for comparison. Remarkably, as a 3D hydrogen-evolving cathode operating in acidic electrolytes, NENU-500 exhibits the highest activity among all MOF materials. It shows an onset overpotential of 180 mV and a Tafel slope of 96 mV·dec(-1), and the catalytic current density can approach 10 mA·cm(-2) at an overpotential of 237 mV. Moreover, NENU-500 and NENU-501 maintain their electrocatalytic activities after 2000 cycles. PMID:25933041

  2. Experimental and Computational Mechanistic Studies Guiding the Rational Design of Molecular Electrocatalysts for Production and Oxidation of Hydrogen.

    PubMed

    Raugei, Simone; Helm, Monte L; Hammes-Schiffer, Sharon; Appel, Aaron M; O'Hagan, Molly; Wiedner, Eric S; Bullock, R Morris

    2016-01-19

    Understanding how to control the movement of protons and electrons is crucial to the design of fast, efficient electrocatalysts for H2 production and oxidation based on earth-abundant metals. Our work seeks to address fundamental questions about proton movement. We have demonstrated that incorporating a pendant amine functioning as a proton relay in the second coordination sphere of a metal complex helps proton mobility, resulting in faster and more energy-efficient catalysts. Proton-transfer reactions can be rate-limiting and are influenced by several factors, such as pKa values, steric effects, hydrogen bonding, and solvation/desolvation of the exogenous base and acid employed. The presence of multiple protonation sites introduces branching points along the catalytic cycle, making less productive pathways accessible or leading to the formation of stable off-cycle species. Using ligands with only one pendant amine mitigates this problem and results in catalysts with high rates for production of H2, although generally at higher overpotentials. For H2 oxidation catalysts, iron complexes with a high H2 binding affinity were developed. However, these iron complexes had a pKa mismatch between the protonated metal center and the protonated pendant amine, and consequently intramolecular proton movement was slow. Taken altogether, our results demonstrate the necessity of optimizing the entire catalytic cycle because optimization of a specific catalytic step can negatively influence another step and not necessarily lead to a better catalytic performance. We discuss a general procedure, based on thermodynamic arguments, which allows the simultaneous minimization of the free-energy change of each catalytic step, yielding a nearly flat free-energy surface, with no large barriers due to energy mismatches from either high- or low-energy intermediates. PMID:26653114

  3. Catalytic amplification based on hole-transporting materials as efficient metal-free electrocatalysts for non-enzymatic glucose sensing.

    PubMed

    Gu, Yue; Yuan, Rongrong; Yan, Xiaoyi; Li, Cong; Liu, Weilu; Chen, Ruixue; Tang, Liu; Zheng, Bo; Li, Yaru; Zhang, Zhiquan; Yang, Ming

    2015-08-19

    Hole-transporting materials with tunable structures and properties are mainly applied in organic light-emitting diodes as transport layer. But their catalytic properties as signal amplifiers in biological assays are seldom reported. In this paper, a starburst molecule, 4,4,4″-tri(N-carbazolyl)-triphenylamine (TCT), containing a triphenylamine as the central core and three carbazoles as the peripheral functional groups was designed and synthesized. Subsequently, the hole-transporting material based on the TCT polymer, poly(TCT) (PTCT), was achieved via a low-cost electrochemical method and exploited as an efficient metal-free electrocatalyst for non-enzymatic glucose detection. Here, this hole-transporting material served three purposes: electrochemical recognition (owing to hydrogen bonding interaction and the biomimetic microenvironment created by the polymer), electrocatalysis (owing to the hole-transporting capability of triphenylamine and the catalytic property of carbazole), and signal amplification (owing to energy migration along the conductive polymer backbone). The electrocatalytic and sensing performances of the sensor based on PTCT were evaluated in detail. Results revealed that the PTCT film could efficiently catalyze the oxidation of glucose at a less-positive potential (+0.20 V) in the absence of any enzymes. The response to glucose was linear in the concentration range of 1.0-6000 μM, and the detection limit was 0.20 μM. With good stability and selectivity, the proposed sensor could be feasibly applied to detect glucose in practical samples. The encouraging sensing performances suggest that the hole-transporting material is one of the promising biomimetic catalysts for electrocatalysis and relevant fields. PMID:26343433

  4. CoP Nanoparticles in Situ Grown in Three-Dimensional Hierarchical Nanoporous Carbons as Superior Electrocatalysts for Hydrogen Evolution.

    PubMed

    Yuan, Weiyong; Wang, Xiaoyan; Zhong, Xiaoling; Li, Chang Ming

    2016-08-17

    The development of efficient and low-cost hydrogen evolution reaction (HER) catalysts is critical for storing energy in hydrogen via water splitting but still presents great challenges. Herein, we report synthesis of three-dimensional (3-D) hierarchical nanoporous carbon (HNC) supported transition metal phosphides (TMPs) for the first time by in situ growth of CoP nanoparticles (NPs) in CaCO3 NP-templated Cinnamomum platyphyllum leaf extract-derived carbon. They were subsequently employed as a HER catalyst, showing an onset potential of 7 mV and an overpotential of 95.8 mV to achieve 10 mA cm(-2), a Tafel plot of 33 mV dec(-1), and an exchange current density of 0.1182 mA cm(-2), of which the onset overpotential and the Tafel plot are the lowest reported for non-noble-metal HER catalysts, and the overpotential to achieve 10 mA cm(-2) and the exchange current density also compare favorably to most reported HER catalysts. In addition, this catalyst exhibits excellent durability with negligible loss in current density after 2000 CV cycles ranging from +0.01 to -0.17 V vs RHE at a scan rate of 100 mV s(-1) or 22 h of chronoamperometric measurement at an overpotential of 96 mV and a high Faraday efficiency of close to 100%. This work not only creates a novel high-performance non-noble-metal HER electrocatalyst and demonstrates the great advantages of the in situ grown 3-D HNC supported TMP NPs for the electrocatalysis of HER but also offers scientific insight into the mechanism for the in situ growth of TMP and their precursor NPs, in which an ultralow reactant concentration and rich functional groups on the 3-D HNC support play critical roles. PMID:27467887

  5. Mixed close packed cobalt molybdenum nitrides as non-noble metal electrocatalysts for the hydrogen evolution reaction

    SciTech Connect

    Cao, Bingfei; Veith, Gabriel M; Neuefeind, Joerg C; Adzic, Radoslav R.; Khalifah, P.

    2013-01-01

    A two-step solid-state reaction for preparing cobalt molybdenum nitride with a nanoscale morphology has been used to produce a highly active and stable electrocatalyst for the hydrogen evolution reaction (HER) under acidic conditions that achieves an iRcorrected current density of 10 mA cm 2 at 0.20 V vs RHE at low catalyst loadings of 0.24 mg/cm2 in rotating disk experiments under a H2 atmosphere. Neutron powder diffraction and pair distribution function (PDF) studies have been used to overcome the insensitivity of X-ray diffraction data to different transition-metal nitride structural polytypes and show that this cobalt molybdenum nitride crystallizes in space group P63/mmc with lattice parameters of a = 2.85176(2) and c = 10.9862(3) and a formula of Co0.6Mo1.4N2. This space group results from the four-layered stacking sequence of a mixed close-packed structure with alternating layers of transition metals in octahedral and trigonal prismatic coordination and is a structure type for which HER activity has not previously been reported. Based on the accurate bond distances obtained from time-of-flight neutron diffraction data, it is determined that the octahedral sites contain a mixture of divalent Co and trivalent Mo, while the trigonal prismatic sites contain Mo in a higher oxidation state. X-ray photoelectron spectroscopy (XPS) studies confirm that at the sample surface nitrogen is present and N H moieties are abundant.

  6. Mixed close-packed cobalt molybdenum nitrides as non-noble metal electrocatalysts for the hydrogen evolution reaction.

    PubMed

    Cao, Bingfei; Veith, Gabriel M; Neuefeind, Joerg C; Adzic, Radoslav R; Khalifah, Peter G

    2013-12-26

    A two-step solid-state reaction for preparing cobalt molybdenum nitride with a nanoscale morphology has been used to produce a highly active and stable electrocatalyst for the hydrogen evolution reaction (HER) under acidic conditions that achieves an iR-corrected current density of 10 mA cm(-2) at -0.20 V vs RHE at low catalyst loadings of 0.24 mg/cm(2) in rotating disk experiments under a H2 atmosphere. Neutron powder diffraction and pair distribution function (PDF) studies have been used to overcome the insensitivity of X-ray diffraction data to different transition-metal nitride structural polytypes and show that this cobalt molybdenum nitride crystallizes in space group P63/mmc with lattice parameters of a = 2.85176(2) Å and c = 10.9862(3) Å and a formula of Co0.6Mo1.4N2. This space group results from the four-layered stacking sequence of a mixed close-packed structure with alternating layers of transition metals in octahedral and trigonal prismatic coordination and is a structure type for which HER activity has not previously been reported. Based on the accurate bond distances obtained from time-of-flight neutron diffraction data, it is determined that the octahedral sites contain a mixture of divalent Co and trivalent Mo, while the trigonal prismatic sites contain Mo in a higher oxidation state. X-ray photoelectron spectroscopy (XPS) studies confirm that at the sample surface nitrogen is present and N-H moieties are abundant. PMID:24175858

  7. Evaluation of the Role of Water in the H2 Bond Formation by Ni(II)-based Electrocatalysts

    SciTech Connect

    Ho, Ming-Hsun; Raugei, Simone; Rousseau, Roger J.; Dupuis, Michel; Bullock, R. Morris

    2013-07-17

    We investigate the role of water in the H-H bond formation by a family of nickel molecular catalysts that exhibit high rates for H2 production in acetonitrile solvent. A key feature leading to the high reactivity is the Lewis acidity of the Ni(II) center and pendant amines in the diphosphine ligand that function as Lewis bases, facilitating H-H bond formation or cleavage. Significant increases in the rate of H2 production have been reported in the presence of added water. Our calculations show that molecular water can displace an acetonitrile solvent molecule in the first solvation shell of the metal. One or two water molecules can also participate in shuttling a proton that can combine with a metal hydride to form the H-H bond. However the participation of the water molecules does not lower the barrier to H-H bond formation. Thus these calculations suggest that the rate increase due to water in these electrocatalysts is not associated with the elementary step of H-H bond formation or cleavage, but rather with the proton delivery steps. We attribute the higher barrier in the H-H bond formation in the presence of water to a decrease in direct interaction between the protic and hydridic hydrogen atoms forced by the water molecules. This research was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the US Department of Energy, Office of Science, Office of Basic Energy Sciences. Computational resources were provided at W. R. Wiley Environmental Molecular Science Laboratory - Pacific Northwest National Laboratory, the National Energy Research Scientific Computing Center (NERSC) at Lawrence Berkeley National Laboratory, and the Jaguar supercomputer at Oak Ridge National Laboratory.

  8. Nitrogen and phosphorus dual-doped hierarchical porous carbon foams as efficient metal-free electrocatalysts for oxygen reduction reactions.

    PubMed

    Jiang, Hongliang; Zhu, Yihua; Feng, Qian; Su, Yunhe; Yang, Xiaoling; Li, Chunzhong

    2014-03-10

    Despite tremendous progress in developing doped carbocatalysts for the oxygen reduction reaction (ORR), the ORR activity of current metal-free carbocatalysts is still inferior to that of conventional Pt/C catalysts, especially in acidic media and neutral solution. Moreover, it also remains a challenge to develop an effective and scalable method for the synthesis of metal-free carbocatalysts. Herein, we have developed nitrogen and phosphorus dual-doped hierarchical porous carbon foams (HP-NPCs) as efficient metal-free electrocatalysts for ORR. The HP-NPCs were prepared for the first time by copyrolyzing nitrogen- and phosphorus-containing precursors and poly(vinyl alcohol)/polystyrene (PVA/PS) hydrogel composites as in situ templates. Remarkably, the resulting HP-NPCs possess controllable nitrogen and phosphorus content, high surface area, and a hierarchical interconnected macro-/mesoporous structure. In studying the effects of the HP-NPCs on the ORR, we found that the as-prepared HP-NPC materials exhibited not only excellent catalytic activity for ORR in basic, neutral, and acidic media, but also much better tolerance for methanol oxidation and much higher stability than the commercial, state-of-the-art Pt/C catalysts. Because of all these outstanding features, it is expected that the HP-NPC material will be a very suitable catalyst for next-generation fuel cells and lithium-air batteries. In addition, the novel synthetic method described here might be extended to the preparation of many other kinds of hierarchical porous carbon materials or porous carbon that contains metal oxide for wide applications including energy storage, catalysis, and electrocatalysis. PMID:24520023

  9. Pt-Pd alloy nanoparticle-decorated carbon nanotubes: a durable and methanol tolerant oxygen reduction electrocatalyst

    NASA Astrophysics Data System (ADS)

    Ghosh, Sourov; Sahu, Ranjan K.; Retna Raj, C.

    2012-09-01

    We describe the decoration of multiwalled carbon nanotubes (MCNTs) with Pt-Pd alloy nanoelectrocatalysts of three different compositions and their electrocatalytic performance toward the oxygen reduction reaction (ORR). The decoration of the MCNTs involves polymer-assisted impregnation of metal precursors {{PtCl}}_{6}^{2-} and {{PdCl}}_{4}^{2-} and the subsequent reduction of the impregnated precursors by a modified polyol route. The composition of the catalyst was controlled by tuning the molar ratio of the precursors during their impregnation. Electron probe microscopic analysis shows that the catalysts have compositions of Pt46Pd54, Pt64Pd36 and Pt28Pd72. The Pt46Pd54 and Pt64Pd36 catalysts have truncated octahedral and icosahedral shapes with a size ranging from 8 to 10 nm. On the other hand, the catalyst of Pt28Pd72 composition has a spherical/quasispherical shape with a size distribution of 1-2 nm. The XPS measurement confirms the signature of metallic Pt and Pd. The Pt46Pd54 catalyst has a pronounced electrocatalytic activity toward the ORR with a specific and mass activity of 378 ~\\mu {A}~{{cm}}_{{Pt}-{Pd}}^{-2} and 6 4~\\mu {A}~\\mu {{g}}_{{Pt}-{Pd}}^{-1}, respectively at 0.8 V. Moreover, the Pt46Pd54 nanoelectrocatalyst is highly durable and it retains its initial catalytic activity even after 1000 extensive cycles. Interestingly, this catalyst has a very high tolerance toward methanol and it does not favor the oxidation of methanol in the potential window of 0.1-1.4 V. The electrocatalytic activity of the alloy electrocatalyst is compared with commercially available Pt black and MCNT-supported spherical Pt nanoparticles. The catalytic activity of the Pt46Pd54 nanoelectrocatalyst is higher than the other catalysts. The Pt46Pd54 catalyst outperforms the electrocatalytic activity of all other catalysts.

  10. Palladium Nanoparticles Supported on Nitrogen and Sulfur Dual-Doped Graphene as Highly Active Electrocatalysts for Formic Acid and Methanol Oxidation.

    PubMed

    Zhang, Xin; Zhu, Jixin; Tiwary, Chandra Sekhar; Ma, Zhongyuan; Huang, Huajie; Zhang, Jianfeng; Lu, Zhiyong; Huang, Wei; Wu, Yuping

    2016-05-01

    Optimized designing of highly active electrocatalysts has been regarded as a critical point to the development of portable fuel cell systems with high power density. Here we report a facile and cost-effective strategy to synthesis of ultrafine Pd nanoparticles (NPs) supported on N and S dual-doped graphene (NS-G) nanosheets as multifunctional electrocatalysts for both direct formic acid fuel cell and direct methanol fuel cell. The incorporation of N and S atoms into graphene frameworks is achieved by a thermal treatment process, followed by the controlled growth of Pd NPs via a solvothermal approach. Owning to the unique structural features as well as the strong synergistic effects, the resulting Pd/NS-G hybrid exhibits outstanding electrocatalytic performance toward both formic acid and methanol electro-oxidation, such as higher anodic peak current densities and more exceptional catalytic stability than those of Pd/Vulcan XC-72R and Pd/undoped graphene catalysts. These findings open up new possibility in the construction of advanced Pd-based catalysts, which is conducive to solving the current bottlenecks of fuel cell technologies. PMID:27082661

  11. Iron-embedded boron nitride nanosheet as a promising electrocatalyst for the oxygen reduction reaction (ORR): A density functional theory (DFT) study

    NASA Astrophysics Data System (ADS)

    Feng, Li-yan; Liu, Yue-jie; Zhao, Jing-xiang

    2015-08-01

    We performed comprehensive density functional theory (DFT) calculations to explore the possibility of the Fe-embedded hexagonal boron nitride (h-BN) sheet as a novel electrocatalyst for ORR. Our results show that Fe atom can strongly bind with defective BN sheet and thus ensure its high stability. Moreover, O2 molecule is found to be strongly chemisorbed on Fe-embedded BN sheet with the adsorption energy of -1.76 eV, which can server as precursors for ORR, followed by its hydrogenation into OOH species rather than direct breakage of the O-O bond. Further, the HOOH species in the process of OOH reduction is shown to be unstable and dissociates into two OH group, suggesting that ORR catalyzed by Fe-embedded BN sheet is a direct four-electron pathway. Finally, on the basis of the calculations on the free energy change and activate energy of each step in ORR, we expect that Fe-embedded BN sheet exhibits good catalytic activity for ORR. Our results provide an useful guidance for the design and fabrication of novel and nonprecious BN sheet-based electrocatalyst for ORR as the alternative of expensive Pt catalysts.

  12. Porous Core-Shell Fe3C Embedded N-doped Carbon Nanofibers as an Effective Electrocatalysts for Oxygen Reduction Reaction.

    PubMed

    Ren, Guangyuan; Lu, Xianyong; Li, Yunan; Zhu, Ying; Dai, Liming; Jiang, Lei

    2016-02-17

    The development of nonprecious-metal-based electrocatalysts with high oxygen reduction reaction (ORR) activity, low cost, and good durability in both alkaline and acidic media is very important for application of full cells. Herein, we developed a facile and economical strategy to obtain porous core-shell Fe3C embedded nitrogen-doped carbon nanofibers (Fe3C@NCNF-X, where X denotes pyrolysis temperature) by electrospinning of polyvinylidene fluoride (PVDF) and FeCl3 mixture, chemical vapor phase polymerization of pyrrole, and followed by pyrolysis of composite nanofibers at high temperatures. Note that the FeCl3 and polypyrrole acts as precursor for Fe3C core and N-doped carbon shell, respectively. Moreover, PVDF not only plays a role as carbon resources, but also provides porous structures due to hydrogen fluoride exposure originated from thermal decomposition of PVDF. The resultant Fe3C@NCNF-X catalysts, particularly Fe3C@NCNF-900, showed efficient electrocatalytic performance for ORR in both alkaline and acidic solutions, which are attributed to the synergistic effect between Fe3C and N-doped carbon as catalytic active sites, and carbon shell protects Fe3C from leaching out. In addition, the Fe3C@NCNF-X catalyst displayed a better long-term stability, free from methanol crossover and CO-poisoning effects than those of Pt/C, which is of great significance for the design and development of advanced electrocatalysts based on nonprecious metals. PMID:26808226

  13. Activity of dealloyed PtCo 3 and PtCu 3 nanoparticle electrocatalyst for oxygen reduction reaction in polymer electrolyte membrane fuel cell

    NASA Astrophysics Data System (ADS)

    Oezaslan, Mehtap; Strasser, Peter

    We report a comparative study of the alloy formation and electrochemical activity of dealloyed PtCo 3 and PtCu 3 nanoparticle electrocatalysts for the oxygen reduction reaction (ORR). For the Pt-Co system the maximum annealing temperatures were 650 °C, 800 °C and 900 °C for 7 h to drive the Pt-Co alloy formation and the particle growth. EDS and XRD were employed for the characterization of catalyst powders. The RDE and RRDE experiments were conducted in 0.1 M HClO 4 at room temperature. We demonstrate that the mass and surface area specific ORR activities of Pt-Co and Pt-Cu alloys after voltammetric activation exhibit a considerable improvement compared to those of pure Pt/C. The dealloyed PtCo 3 (800 °C/7 h) electrocatalyst performs 3 times higher in terms of Pt-based mass activity and 4-5 times higher in terms of ECSA-based specific activity than a 28.2 wt.% Pt/C. Dealloyed Pt-Co catalysts (800 °C/7 h) show the most favorable balance between mass and specific ORR activity with a particle size of 2.2 ± 0.1 nm. We hypothesize that geometric strain effects of the dealloyed Pt-Co nanoparticles, similar to those found in dealloyed PtCu 3 nanoparticles, are responsible for the improvement in ORR activity [1].

  14. Carbon-Coated Core-Shell Fe-Cu Nanoparticles as Highly Active and Durable Electrocatalysts for a Zn-Air Battery.

    PubMed

    Nam, Gyutae; Park, Joohyuk; Choi, Min; Oh, Pilgun; Park, Suhyeon; Kim, Min Gyu; Park, Noejung; Cho, Jaephil; Lee, Jang-Soo

    2015-06-23

    Understanding the interaction between a catalyst and oxygen has been a key step in designing better electrocatalysts for the oxygen reduction reaction (ORR) as well as applying them in metal-air batteries and fuel cells. Alloying has been studied to finely tune the catalysts' electronic structures to afford proper binding affinities for oxygen. Herein, we synthesized a noble-metal-free and nanosized transition metal CuFe alloy encapsulated with a graphitic carbon shell as a highly efficient and durable electrocatalyst for the ORR in alkaline solution. Theoretical models and experimental results demonstrated that the CuFe alloy has a more moderate binding strength for oxygen molecules as well as the final product, OH(-), thus facilitating the oxygen reduction process. Furthermore, the nitrogen-doped graphitic carbon-coated layer, formed catalytically under the influence of iron, affords enhanced charge transfer during the oxygen reduction process and superior durability. These benefits were successfully confirmed by realizing the catalyst application in a mechanically rechargeable Zn-air battery. PMID:25967866

  15. CoS(2x)Se(2(1-x)) nanowire array: an efficient ternary electrocatalyst for the hydrogen evolution reaction.

    PubMed

    Liu, Kaili; Wang, Fengmei; Xu, Kai; Shifa, Tofik Ahmed; Cheng, Zhongzhou; Zhan, Xueying; He, Jun

    2016-02-28

    Binary transition metal dichalcogenides (TMDs) have emerged as efficient catalysts for the hydrogen evolution reaction (HER). Co-based TMDs, such as CoS2 and CoSe2, demonstrate promising HER performance due to their intrinsic metallic nature. Recently, the ternary electrocatalysts were widely acknowledged for their prominent efficiency as compared to their binary counterparts due to increased active sites caused by the incorporation of different atoms. Herein, we successfully grew the ternary CoS2xSe2(1-x) (x = 0.67) nanowires (NWs) on a flexible carbon fiber. As a superior electrocatalyst, ternary CoS2xSe2(1-x) NWs arrays demonstrated excellent catalytic activity for electrochemical hydrogen evolution in acidic media, achieving current densities of 10 mA cm(-2) and 100 mA cm(-2) at overpotentials of 129.5 mV and 174 mV, respectively. Notably, the high stability of CoS2xSe2(1-x) NWs suggested that the ternary CoS2xSe2(1-x) NWs are a scalable catalyst for electrochemical hydrogen evolution. PMID:26853684

  16. Co@Co3 O4 @PPD Core@bishell Nanoparticle-Based Composite as an Efficient Electrocatalyst for Oxygen Reduction Reaction.

    PubMed

    Wang, Zhijuan; Li, Bing; Ge, Xiaoming; Goh, F W Thomas; Zhang, Xiao; Du, Guojun; Wuu, Delvin; Liu, Zhaolin; Andy Hor, T S; Zhang, Hua; Zong, Yun

    2016-05-01

    Durable electrocatalysts with high catalytic activity toward oxygen reduction reaction (ORR) are crucial to high-performance primary zinc-air batteries (ZnABs) and direct methanol fuel cells (DMFCs). An efficient composite electrocatalyst, Co@Co3 O4 core@shell nanoparticles (NPs) embedded in pyrolyzed polydopamine (PPD) is reported, i.e., in Co@Co3 O4 @PPD core@bishell structure, obtained via a three-step sequential process involving hydrothermal synthesis, high temperature calcination under nitrogen atmosphere, and gentle heating in air. With Co@Co3 O4 NPs encapsulated by ultrathin highly graphitized N-doped carbon, the catalyst exhibits excellent stability in aqueous alkaline solution over extended period and good tolerance to methanol crossover effect. The integration of N-doped graphitic carbon outer shell and ultrathin nanocrystalline Co3 O4 inner shell enable high ORR activity of the core@bishell NPs, as evidenced by ZnABs using catalyst of Co@Co3 O4 @PPD in air-cathode which delivers a stable voltage profile over 40 h at a discharge current density of as high as 20 mA cm(-2) . PMID:27031907

  17. How Light-Harvesting Semiconductors Can Alter the Bias of Reversible Electrocatalysts in Favor of H2 Production and CO2 Reduction

    PubMed Central

    2013-01-01

    The most efficient catalysts for solar fuel production should operate close to reversible potentials, yet possess a bias for the fuel-forming direction. Protein film electrochemical studies of Ni-containing carbon monoxide dehydrogenase and [NiFeSe]-hydrogenase, each a reversible electrocatalyst, show that the electronic state of the electrode strongly biases the direction of electrocatalysis of CO2/CO and H+/H2 interconversions. Attached to graphite electrodes, these enzymes show high activities for both oxidation and reduction, but there is a marked shift in bias, in favor of CO2 or H+ reduction, when the respective enzymes are attached instead to n-type semiconductor electrodes constructed from CdS and TiO2 nanoparticles. This catalytic rectification effect can arise for a reversible electrocatalyst attached to a semiconductor electrode if the electrode transforms between semiconductor- and metallic-like behavior across the same narrow potential range (<0.25 V) that the electrocatalytic current switches between oxidation and reduction. PMID:24070184

  18. Preparation of onion-like Pt-terminated Pt-Cu bimetallic nano-sized electrocatalysts for oxygen reduction reaction in fuel cells

    NASA Astrophysics Data System (ADS)

    Lim, Taeho; Kim, Ok-Hee; Sung, Yung-Eun; Kim, Hyun-Jong; Lee, Ho-Nyun; Cho, Yong-Hun; Kwon, Oh Joong

    2016-06-01

    Onion-like Pt-terminated Pt-Cu bimetallic nano-sized electrocatalysts (Pt/Cu/Pt/C) were synthesized by using an electroless deposition method. The synthesized Pt/Cu/Pt/C consisted of a Pt-enriched shell, a sandwiched Pt-Cu alloy layer, and a Pt core. The Pt/Cu/Pt/C showed higher electrocatalytic activity toward oxygen reduction reaction in half-cell test than that of commercial Pt/C due to an electronic structure change in the Pt-enriched shell, resulting from the sandwiched Pt-Cu alloy layer underneath. The stability of the Pt/Cu/Pt/C was examined by using both half-cell and single-cell degradation tests. In both tests, the Pt/Cu/Pt/C exhibited stronger resistance to catalyst degradation than that of the commercial Pt/C. It is notable that cell performance with the Pt/Cu/Pt/C was fully recovered by N2 purging after single-cell degradation testing, indicating there was no permanent damage to the electrocatalyst during the test. It is suggested that thermodynamically-stable structure of the Pt/Cu/Pt/C contributed to the improved stability.

  19. Synthesis and characterization of NiFe2O4 electrocatalyst for the hydrogen evolution reaction in alkaline water electrolysis using different polymer binders

    NASA Astrophysics Data System (ADS)

    Chanda, Debabrata; Hnát, Jaromír; Paidar, Martin; Schauer, Jan; Bouzek, Karel

    2015-07-01

    NiFe2O4 electrocatalyst for the hydrogen evolution reaction (HER) has been synthesized using the co-precipitation method of the respective metal ions from water solution. After calcination of the precipitate, the resulting electrocatalyst was characterized by a broad range of techniques to obtain information on its crystallographic structure, specific surface area, morphology and chemical composition. The electrocatalytic activity towards HER in alkaline water electrolysis was investigated by means of linear sweep voltammetry. The catalyst showed promising electrocatalytic properties. Subsequently three types of binders were used to prepare a cathode catalytic layer based on a catalyst synthesized on top of a nickel foam support, namely an anion-selective quaternized poly(phenylene oxide) (qPPO) ionomer, an electroneutral polymer polytetrafluoroethylene and cation-selective Nafion®. The resulting membrane-electrode assemblies (MEAs), based on an anion-selective membrane, were tested in an alkaline water electrolyzer. In a single-cell test the MEA with a qPPO ionomer exhibited higher HER activity compared to the remaining binders tested. The current density obtained using a MEA containing qPPO binder attained a value of 125 mA cm-2 at a cell voltage of 1.85 V. The stability of the MEA containing qPPO binder was examined by continuous operation for 143 h, followed by 55 h intermittent electrolysis.

  20. Blending Cr2O3 into a NiO-Ni electrocatalyst for sustained water splitting

    SciTech Connect

    Gong, Ming; Zhou, Wu; Kenney, Michael James; Kapusta, Rich; Cowley, Sam; Wu, Yingpeng; Lu, Bingan; Lin, Meng -Chang; Wang, Di -Yan; Yang, Jiang; Hwang, Bing -Joe; Dai, Hongjie

    2015-08-24

    The rising H2 economy demands active and durable electrocatalysts based on low-cost, earth-abundant materials for water electrolysis/photolysis. Here we report nanoscale Ni metal cores over-coated by a Cr2O3-blended NiO layer synthesized on metallic foam substrates. The Ni@NiO/Cr2O3 triphase material exhibits superior activity and stability similar to Pt for the hydrogen-evolution reaction in basic solutions. The chemically stable Cr2O3 is crucial for preventing oxidation of the Ni core, maintaining abundant NiO/Ni interfaces as catalytically active sites in the heterostructure and thus imparting high stability to the hydrogen-evolution catalyst. The highly active and stable electrocatalyst enables an alkaline electrolyzer operating at 20 mA cm–2 at a voltage lower than 1.5 V, lasting longer than 3 weeks without decay. Thus, the non-precious metal catalysts afford a high efficiency of about 15 % for light-driven water splitting using GaAs solar cells.

  1. Nitrogen and fluorine dual-doped mesoporous graphene: a high-performance metal-free ORR electrocatalyst with a super-low HO2- yield

    NASA Astrophysics Data System (ADS)

    Jiang, Shu; Sun, Yujing; Dai, Haichao; Hu, Jingting; Ni, Pengjuan; Wang, Yilin; Li, Zhen; Li, Zhuang

    2015-06-01

    In this study, we successfully, for the first time, prepared nitrogen and fluorine dual-doped mesoporous graphene (NF-MG) via the thermal treatment of graphene oxide/polyaniline composites (GO/PANI) and NH4F. Benefiting from the synergistic effect of N and F co-doping into the G framework, the oxygen reduction reaction performance of the optimal catalyst (NF-MG3) is comparable with the-state-of-the-art Pt/C catalyst in an alkaline medium, which makes it an ideal candidate as an efficient metal-free ORR electrocatalyst in fuel cells.In this study, we successfully, for the first time, prepared nitrogen and fluorine dual-doped mesoporous graphene (NF-MG) via the thermal treatment of graphene oxide/polyaniline composites (GO/PANI) and NH4F. Benefiting from the synergistic effect of N and F co-doping into the G framework, the oxygen reduction reaction performance of the optimal catalyst (NF-MG3) is comparable with the-state-of-the-art Pt/C catalyst in an alkaline medium, which makes it an ideal candidate as an efficient metal-free ORR electrocatalyst in fuel cells. Electronic supplementary information (ESI) available: Experimental details (Scheme S1), optimization and morphology of NF-MGs catalysts (Fig. S1-S2), Fig. S3-S9, and Tables S1-S2. See DOI: 10.1039/c5nr01793a

  2. Use of urchin-like NixCo3-xO4 hierarchical nanostructures based on non-precious metals as bifunctional electrocatalysts for anion-exchange membrane alkaline alcohol fuel cells

    NASA Astrophysics Data System (ADS)

    Manivasakan, Palanisamy; Ramasamy, Parthiban; Kim, Jinkwon

    2014-07-01

    Bifunctional electrocatalysts based on non-precious metals were developed for the dioxygen reduction and methanol oxidation reactions. These electrocatalysts can be considered as candidate cathode and anode materials for anion-exchange membrane (AEM) alkaline alcohol fuel cells. A series of Ni-doped cobalt oxide (NixCo3-xO4) hierarchical nanostructures composed of one-dimensional nanorods was prepared by an inexpensive hydrothermal method. X-ray diffraction patterns showed that the NixCo3-xO4 crystallized in a cubic spinel phase. The electrochemical performance of the catalysts was investigated using a conventional cyclic voltammetry technique. The electrocatalytic behaviour of the NixCo3-xO4 hierarchical nanostructures was compared with the behaviour of Co3O4 and Co0.33Ni0.67O. The synergistic behaviour of the Ni in the NixCo3-xO4 nanostructures was established with respect to the Ni content. NixCo3-xO4 hierarchical nanostructures show a better catalytic behaviour than Co3O4 and Co0.33Ni0.67O. Although the NixCo3-xO4 compositions all showed good catalytic behaviour, Ni1Co2O4 was identified as a superior bifunctional electrocatalyst for the oxygen reduction and methanol oxidation reactions in alkaline media. The effect of the Ni content on the electrocatalytic properties of the NixCo3-xO4 hierarchical nanostructures was clearly shown. The use of these electrocatalysts based on non-precious metals could have a commercial impact on the development of non-platinum electrocatalysts for application in AEM alkaline alcohol fuel cells.Bifunctional electrocatalysts based on non-precious metals were developed for the dioxygen reduction and methanol oxidation reactions. These electrocatalysts can be considered as candidate cathode and anode materials for anion-exchange membrane (AEM) alkaline alcohol fuel cells. A series of Ni-doped cobalt oxide (NixCo3-xO4) hierarchical nanostructures composed of one-dimensional nanorods was prepared by an inexpensive hydrothermal method. X

  3. Use of urchin-like Ni(x)Co(3-x)O4 hierarchical nanostructures based on non-precious metals as bifunctional electrocatalysts for anion-exchange membrane alkaline alcohol fuel cells.

    PubMed

    Manivasakan, Palanisamy; Ramasamy, Parthiban; Kim, Jinkwon

    2014-08-21

    Bifunctional electrocatalysts based on non-precious metals were developed for the dioxygen reduction and methanol oxidation reactions. These electrocatalysts can be considered as candidate cathode and anode materials for anion-exchange membrane (AEM) alkaline alcohol fuel cells. A series of Ni-doped cobalt oxide (NixCo3-xO4) hierarchical nanostructures composed of one-dimensional nanorods was prepared by an inexpensive hydrothermal method. X-ray diffraction patterns showed that the NixCo3-xO4 crystallized in a cubic spinel phase. The electrochemical performance of the catalysts was investigated using a conventional cyclic voltammetry technique. The electrocatalytic behaviour of the NixCo3-xO4 hierarchical nanostructures was compared with the behaviour of Co3O4 and Co0.33Ni0.67O. The synergistic behaviour of the Ni in the NixCo3-xO4 nanostructures was established with respect to the Ni content. NixCo3-xO4 hierarchical nanostructures show a better catalytic behaviour than Co3O4 and Co0.33Ni0.67O. Although the NixCo3-xO4 compositions all showed good catalytic behaviour, Ni1Co2O4 was identified as a superior bifunctional electrocatalyst for the oxygen reduction and methanol oxidation reactions in alkaline media. The effect of the Ni content on the electrocatalytic properties of the NixCo3-xO4 hierarchical nanostructures was clearly shown. The use of these electrocatalysts based on non-precious metals could have a commercial impact on the development of non-platinum electrocatalysts for application in AEM alkaline alcohol fuel cells. PMID:24990285

  4. pH-Dependent Reduction Potentials and Proton-Coupled Electron Transfer Mechanisms in Hydrogen-Producing Nickel Molecular Electrocatalysts

    SciTech Connect

    Horvath, Samantha; Fernandez, Laura; Appel, Aaron M.; Hammes-Schiffer, Sharon

    2013-04-01

    The nickel-based Ph Bz 2 2 P N electrocatalysts, which are comprised of a nickel atom and two 1,5-dibenzyl-3,7-diphenyl-1,5-diaza-3,7-diphosphacyclooctane ligands, have been shown to effectively catalyze H2 production in acetonitrile. Recent electrochemical experiments revealed a linear dependence of the NiII/I reduction potential on pH, suggesting a proton-coupled electron transfer (PCET) reaction. In the proposed mechanism, the catalytic cycle begins with a PCET process involving electrochemical electron transfer to the nickel center and intermolecular proton transfer from an acid to the pendant amine ligand. This paper presents quantum mechanical calculations of this PCET process to examine the thermodynamics of the sequential mechanisms, in which either the electron or the proton transfers first (ET–PT and PT–ET, respectively), and the concerted mechanism (EPT). The favored mechanism depends on a balance among many factors, including the acid strength, association free energy for the acid–catalyst complex, PT free energy barrier, and ET reduction potential. The ET reduction potential is less negative after PT, favoring the PT–ET mechanism, and the association free energy is less positive after reduction, favoring the ET–PT mechanism. The calculations, along with analysis of the experimental data, indicate that the sequential ET–PT mechanism is favored for weak acids because of the substantial decrease in the association free energy after reduction. For strong acids, however, the PT–ET mechanism may be favored because the association free energy is somewhat smaller and PT is more thermodynamically favorable. The concerted mechanism could also occur, particularly for intermediate acid strengths. In the context of the entire catalytic cycle for H2 production, the initial PCET process involving intermolecular PT has a more negative reduction potential than the subsequent PCET process involving intramolecular PT. As a result, the second PCET should

  5. Highly Active Iridium/Iridium Tin/Tin Oxide Heterogeneous Nanoparticles as Alternative Electrocatalysts for the Ethanol Oxidation Reaction

    SciTech Connect

    Du W.; Su D.; Wang Q.; Saxner D.; Deskins N.A.; Krzanowski J.E.; Frenkel A.I.; Teng X.

    2011-08-03

    Ethanol is a promising fuel for low-temperature direct fuel cell reactions due to its low toxicity, ease of storage and transportation, high-energy density, and availability from biomass. However, the implementation of ethanol fuel cell technology has been hindered by the lack of low-cost, highly active anode catalysts. In this paper, we have studied Iridium (Ir)-based binary catalysts as low-cost alternative electrocatalysts replacing platinum (Pt)-based catalysts for the direct ethanol fuel cell (DEFC) reaction. We report the synthesis of carbon supported Ir{sub 71}Sn{sub 29} catalysts with an average diameter of 2.7 {+-} 0.6 nm through a 'surfactant-free' wet chemistry approach. The complementary characterization techniques, including aberration-corrected scanning transmission electron microscopy equipped with electron energy loss spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and X-ray absorption spectroscopy, are used to identify the 'real' heterogeneous structure of Ir{sub 71}Sn{sub 29}/C particles as Ir/Ir-Sn/SnO{sub 2}, which consists of an Ir-rich core and an Ir-Sn alloy shell with SnO{sub 2} present on the surface. The Ir{sub 71}Sn{sub 29}/C heterogeneous catalyst exhibited high electrochemical activity toward the ethanol oxidation reaction compared to the commercial Pt/C (ETEK), PtRu/C (Johnson Matthey) as well as PtSn/C catalysts. Electrochemical measurements and density functional theory calculations demonstrate that the superior electro-activity is directly related to the high degree of Ir-Sn alloy formation as well as the existence of nonalloyed SnO{sub 2} on surface. Our cross-disciplinary work, from novel 'surfactant-free' synthesis of Ir-Sn catalysts, theoretical simulations, and catalytic measurements to the characterizations of 'real' heterogeneous nanostructures, will not only highlight the intriguing structure-property correlations in nanosized catalysts but also have a transformative impact on the commercialization of DEFC

  6. Iron Complexes Bearing Diphosphine Ligands with Positioned Pendant Amines as Electrocatalysts for the Oxidation of H2

    SciTech Connect

    Liu, Tianbiao L.; Liao, Qian; O'Hagan, Molly J.; Hulley, Elliott; DuBois, Daniel L.; Bullock, R. Morris

    2015-06-22

    The synthesis and spectroscopic characterization of CpC5F4NFe(PtBu2NBn2)Cl, [3-Cl] (where C5F4N is the tetrafluorpyridyl substituent and PtBu2NBn2 = 1,5-di(tert-butyl)-3,7-di(benzyl)-1,5-diaza-3,7-diphosphacyclooctane) are reported. Complex 3-Cl and previously reported [CpC5F4NFe(PtBu2NtBu2)Cl], 4-Cl, are precursors to intermediates in the catalytic oxidation of H2, including CpC5F4NFe(PtBu2NBn2)H (3-H), CpC5F4NFe(PtBu2NtBu2)H (4-H), [CpC5F4NFe(PtBu2NBn2)]BArF4 ([3](BArF4), [CpC5F4NFe(PtBu2NtBu2)]BArF4 ([4](BArF4), [CpC5F4NFe(PtBu2NBn2)(H2)]BArF4 ([3-H2]BArF4), and [CpC5F4NFe(PtBu2NtBu2H)H]BArF4 ([4-FeH(NH)]BArF4). All of these complexes were characterized by spectroscopic and electrochemical studies; 3-Cl, 3-H and 4-Cl were also characterized by single crystal diffraction studies. 3-H and 4-H are electrocatalysts for H2 (1.0 atm) oxidation in the presence of a excess of the amine base N-methylpyrrolidine, with turnover frequencies at 22 °C of 2.5 s-1 and 0.5 s-1, and overpotentials at Ecat/2 of 235 mV and 95 mV, respectively. Studies of individual chemical and/or electrochemical reactions of the various intermediates provide important insights into the factors governing the overall catalytic activity for H2 oxidation, and provide important insights into the role of the pendant base of the [FeFe] hydrogenase active site. This work was supported by the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences. Pacific Northwest National Laboratory is operated by Battelle for the U.S. Department of Energy.

  7. Nitrogen-doped graphene interpenetrated 3D Ni-nanocages: efficient and stable water-to-dioxygen electrocatalysts

    NASA Astrophysics Data System (ADS)

    Dhavale, Vishal M.; Gaikwad, Sachin S.; George, Leena; Devi, R. Nandini; Kurungot, Sreekumar

    2014-10-01

    Herein, we report the synthesis of a nitrogen-doped graphene (NGr) interpenetrated 3D Ni-nanocage (Ni-NGr) electrocatalyst by a simple water-in-oil (w/o) emulsion technique for oxidation of water to dioxygen. Correlation of adsorption of NGr and subsequent interpenetration through the specific surface plane of nickel particles as well as the concomitant interaction of N and C with Ni in the nano-regime has been investigated. Apart from the benefits of the synergistic interactions between Ni, N, and C, the overall integrity of the structure and its intra-molecular connectivity within the framework help in achieving better oxygen evolution characteristics at a significantly reduced overpotential. The engineered Ni-NGr nanocage displays a substantially low overpotential of ~290 mV at a practical current density of 20 mA cm-2 in 0.1 M KOH. In comparison, NGr and Ni-particles as separate entities give overpotentials of ~570 and ~370 mV under similar conditions. Moreover, the long term stability of Ni-NGr was investigated by anodic potential cycling for 500 cycles and an 8.5% increment in the overpotential at 20 mA cm-2 was observed. Additionally, a chronoamperometric test was performed for 15 h at 20 mA cm-2, which highlights the better sustainability of Ni-NGr under the actual operating conditions. Finally, the quantitative estimation of evolved oxygen was monitored by gas chromatography and was found to be 70 mmol h-1 g-1 of oxygen, which is constant in the second cycle as well.Herein, we report the synthesis of a nitrogen-doped graphene (NGr) interpenetrated 3D Ni-nanocage (Ni-NGr) electrocatalyst by a simple water-in-oil (w/o) emulsion technique for oxidation of water to dioxygen. Correlation of adsorption of NGr and subsequent interpenetration through the specific surface plane of nickel particles as well as the concomitant interaction of N and C with Ni in the nano-regime has been investigated. Apart from the benefits of the synergistic interactions between Ni, N

  8. Porous Fe-Nx/C hybrid derived from bi-metal organic frameworks as high efficient electrocatalyst for oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Wu, Yijin; Zhao, Shenlong; Zhao, Kun; Tu, Tengxiu; Zheng, Jianzhong; Chen, Jie; Zhou, Haifeng; Chen, Dejian; Li, Shunxing

    2016-04-01

    A simple, low-cost and large-scale synthesis method for the carbonized porous cubes (CPCs) containing Fe and N co-doped porous carbon hybrid (Fe-Nx/C) with controlled-morphology, uniform elemental distribution and well-defined pore size is developed by pyrolyzing bimetallic FeIII-modified IRMOF-3 cubes in Argon atmosphere at 800 °C. Furtherly, the CPCs are used as the electrocatalyst for oxygen reduction reaction in alkaline solution. Impressively, the CPCs hybrid exhibits a superior electrocatalytic activity with high onset potential (0.93 V) and half-wave potential (0.78 V), and excellent stability, which is attributed to the synergistic effect of its high the surface to volume ratio, well-defined pore size, multi-active composition and high exposed catalytic active sites. We believe the materials based on earth-abundant elements have a huge potential to apply in catalysis, energy, and environment.

  9. Pt loaded two-dimensional TaC-nanosheet/graphene hybrid as an efficient and durable electrocatalyst for direct methanol fuel cells

    NASA Astrophysics Data System (ADS)

    He, Chunyong; Tao, Juzhou

    2016-08-01

    Poor electrocatalytic activity, insufficient operation durability and low carbon monoxide (CO) tolerance of the Pt-based catalysts are key challenges facing the direct methanol fuel cells (DMFCs) as promising electrochemical energy conversion device. We here present a new effort to catalyst designed by depositing Pt nanoparticles on two-dimensional (2D) TaC-nanosheet/graphene hybird (Pt/TaC-G) to obtain notable improvement in electrocatalytic performance over the commercial Pt/C. Experiment results from both X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) support that a strong synergetic chemical coupling interaction between the Pt nanoparticles and the 2D TaC-G significantly enhanced electrocatalytic activity for methanol oxidation reaction (MOR). This process can improve the CO tolerance as well as durability of MOR catalysts simultaneously, making it a promising general approach to design and optimize the next generation electrocatalysts in DMFCs.

  10. One-Pot and Facile Fabrication of Hierarchical Branched Pt-Cu Nanoparticles as Excellent Electrocatalysts for Direct Methanol Fuel Cells.

    PubMed

    Cao, Yanqin; Yang, Yong; Shan, Yufeng; Huang, Zhengren

    2016-03-01

    Hierarchical branched nanoparticles are one promising nanostructure with three-dimensional open porous structure composed of integrated branches for superior catalysis. We have successfully synthesized Pt-Cu hierarchical branched nanoparticles (HBNDs) with small size of about 30 nm and composed of integrated ultrathin branches by using a modified polyol process with introduction of poly(vinylpyrrolidone) and HCl. This strategy is expected to be a general strategy to prepare various metallic nanostructures for catalysis. Because of the special open porous structure, the as-prepared Pt-Cu HBNDs exhibit greatly enhanced specific activity toward the methanol oxidation reaction as much as 2.5 and 1.7 times compared with that of the commercial Pt-Ru and Pt-Ru/C catalysts, respectively. Therefore, they are potentially applicable as electrocatalysts for direct methanol fuel cells. PMID:26885678

  11. Cost-effective counter electrode electrocatalysts from iron@palladium and iron@platinum alloy nanospheres for dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Tang, Qunwei; Liu, Juan; Zhang, Huihui; He, Benlin; Yu, Liangmin

    2015-11-01

    Pursuit of cost-effective counter electrode (CE) electrocatalysts with no sacrifice of photovoltaic performances has been a persistent objective for dye-sensitized solar cells (DSSCs). Here we demonstrate the galvanic replacement realization of cost-effective CEs from Fe@M (M = Pd, Pt) nanospheres for DSSCs. Due to the enhanced catalytic activity originated from compressive strain and extended surface in tuning the electronic structure of Pd (or Pt) shell along with competitive dissolution reaction of Fe with electrolyte, the cells with high durability display efficiencies of 8.74% and 7.22%. The impressive results along with simple synthesis highlight the potential application of Fe@M nanospheres in robust DSSCs.

  12. Facilely Tuning Porous NiCo2 O4 Nanosheets with Metal Valence-State Alteration and Abundant Oxygen Vacancies as Robust Electrocatalysts Towards Water Splitting.

    PubMed

    Zhu, Chengzhou; Fu, Shaofang; Du, Dan; Lin, Yuehe

    2016-03-14

    Great efforts in developing clean electrochemical water splitting technology leads to the rational design and synthesis of highly efficient oxygen evolution reaction (OER) catalysts with low overpotential and fast reaction kinetics. Herein, we focus on the role that morphology and composition play in the OER performance to rationally design freestanding 3D porous NiCo2O4 nanosheets with metal valence states alteration and abundant oxygen vacancies as robust electrocatalysts towards water splitting. Besides metal valence-state alteration, surface modification regarding the evolution of oxygen vacancies is facilely realized upon the sodium borohydride treatment, which is beneficial for the enhanced OER performance. Taking advantage of the porous nanostructures and abundant surface activity sites with high reactivity, the resultant nanostructures exhibit excellent OER activity and stability in alkaline electrolytes that outperform that of pristine NiCo2O4 and commercial RuO2, thus holding great potential for the water splitting. PMID:26845062

  13. An amorphous CoSe film behaves as an active and stable full water-splitting electrocatalyst under strongly alkaline conditions.

    PubMed

    Liu, Tingting; Liu, Qian; Asiri, Abdullah M; Luo, Yonglan; Sun, Xuping

    2015-12-01

    It is attractive but still remains a big challenge to develop non-noble metal bifunctional electrocatalysts efficient for both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) under alkaline conditions. Herein, an amorphous CoSe film electrodeposited on a Ti mesh (a-CoSe/Ti) is demonstrated to exhibit high electrocatalytic activity and stability for both reactions in 1.0 M KOH. It needs overpotentials of 292 and 121 mV to drive 10 mA cm(-2) for OER and HER, respectively. The two-electrode alkaline water electrolyzer affords a water-splitting current of 10 mA cm(-2) at a cell voltage of 1.65 V. This work offers an attractive cost-effective catalytic material toward full water splitting applications. PMID:26431349

  14. Monodisperse Pt{sub 3}Co nanoparticles as electrocatalyst : the effects of particle size and pretretment on electrocatalytic reduction of oxygen.

    SciTech Connect

    Wang, C.; Wang, G.; van der Vliet, D.; Chang, K.-C.; Markovic, N. M.; Stamenkovic, V. R.; Materials Science Division; Indiana Univ.-Purdue Univ.

    2010-07-14

    Monodisperse Pt{sub 3}Co nanoparticles have been synthesized with size control via an organic solvothermal approach. The obtained nanoparticles were incorporated into a carbon matrix and applied as electrocatalysts for the oxygen reduction reaction to investigate the effects of particle size and pretreatment on their catalytic performance. It has been found that the optimal conditions for maximum mass activity were with particles of {approx}4.5 nm and a mild annealing temperature of about 500 C. While the particle size effect can be correlated to the average surface coordination number, Monte Carlo simulations have been introduced to depict the nanoparticle structure and segregation profile, which revealed that the annealing temperature has a direct influence on the particle surface relaxation, segregation and adsorption/catalytic properties. The obtained fundamental understanding of activity enhancement in Pt-bimetallic alloy catalysts could be utilized to guide the development of advanced nanomaterials for catalytic applications.

  15. A straightforward implementation of in situ solution electrochemical ¹³C NMR spectroscopy for studying reactions on commercial electrocatalysts: ethanol oxidation.

    PubMed

    Huang, L; Sorte, E G; Sun, S-G; Tong, Y Y J

    2015-05-11

    Identifying and quantifying electrocatalytic-reaction-generated solution species, be they reaction intermediates or products, are highly desirable in terms of understanding the associated reaction mechanisms. We report herein a straightforward implementation of in situ solution electrochemical (13)C NMR spectroscopy for the first time that enables in situ studies of reactions on commercial fuel-cell electrocatalysts (Pt and PtRu blacks). Using ethanol oxidation reaction (EOR) as a working example, we discovered that (1) the complete oxidation of ethanol to CO2 only took place dominantly at the very beginning of a potentiostatic chronoamperometric (CA) measurement and (2) the PtRu had a much higher activity in catalysing oxygen insertion reaction that leads to acetic acid. PMID:25868425

  16. SECM characterization of Pt-Ru-WC and Pt-Ru-Co ternary thin film combinatorial libraries as anode electrocatalysts for PEMFC

    NASA Astrophysics Data System (ADS)

    Lu, Guojin; Cooper, James S.; McGinn, Paul J.

    Rapid screening of electrocatalytic activity of ternary Pt-Ru-WC and Pt-Ru-Co thin film gradient material libraries towards hydrogen oxidation in the presence or absence of CO adsorption was performed by scanning electrochemical microscopy. It was observed that the addition of WC or Co to Pt or Pt-Ru catalysts can improve their hydrogen oxidation reaction activity and CO tolerance, making them suitable as potential electrocatalysts for polymer electrolyte membrane fuel cells. The stability of WC and Co in the acidic electrolyte were enhanced by alloying with Pt. SECM offers the capability for both qualitative and quantitative characterization of electrocatalytic activity of thin films of potential fuel cell electrode material candidates. However, promising electrode compositions identified by this technique need to be verified by traditional electrode preparation and characterization techniques.

  17. Novel As-doped, As and N-codoped carbon nanotubes as highly active and durable electrocatalysts for O2 reduction in alkaline medium

    NASA Astrophysics Data System (ADS)

    Liu, Ziwu; Li, Meng; Wang, Fang; Wang, Quan-De

    2016-02-01

    To develop more efficient metal-free cathode electrocatalysts for fuel cells, novel arsenic (As)-doped, As and N-codoped carbon nanotubes are synthesized by chemical vapor deposition in this work. The as-prepared As-containing carbon nanotubes exhibit significantly enhanced activity and long-term durability for the oxygen reduction reaction (ORR) in alkaline medium, indicating that the doping of As or codoping As with other heteroatoms into carbon matrix could improve the ORR activity of carbon materials due to the changes in electronic and physical properties of carbon nanotubes evidenced by density functional theory calculations. Moreover, As-containing carbon nanotubes also display much better methanol tolerance, showing a good potential application for future fuel cells.

  18. Research on oxidation by air and tempering of Raney nickel electrocatalysts for the H2 anodes of alkali combustion materials cells. Thesis - Braunschweig Technische Univ., 1982

    NASA Technical Reports Server (NTRS)

    Selbach, H. J.

    1984-01-01

    The controlled oxidation in air of Raney nickel electrocatalysts was studied, with special attention paid to the quantitative analysis of nickel hydroxide. The content of the latter was determined through X-ray studies, thermogravimetric measurements, and spectral photometric examinations. The dependence of the content on the drying of activated catalyst is determined. The influence of nickel hydroxide on the electrochemical parameters of the catalyst, such as diffusion polarization, is studied, including a measurement of the exchange current density using the potential drop method. Conservation by oxidation in air with ancillary stabilization of the oxide in an H2 flow at 300 C is explored, including reduction by H2, the influence of tempering time, and structural studies on conserved and stabilized catalyst, long term research on the catalyst, including the influence of aging on the reduced catalyst, and the results of impedance measurements are presented.

  19. Urchin-like CoP Nanocrystals as Hydrogen Evolution Reaction and Oxygen Reduction Reaction Dual-Electrocatalyst with Superior Stability.

    PubMed

    Yang, Hongchao; Zhang, Yejun; Hu, Feng; Wang, Qiangbin

    2015-11-11

    High-performance electrocatalysts with superior stability are critically important for their practical applications in hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR). Herein, we report a facile method to fabricate urchin-like CoP nanocrystals (NCs) as catalyst for both HER and ORR with desirable electrocatalytic activities and long-term stability. The urchin-like CoP NCs with a diameter of 5 μm were successfully prepared by a hydrothermal reaction following a phosphidation treatment in N2 atmosphere and present excellent HER catalytic performance with a low onset overpotential of 50 mV, a small Tafel slope of 46 mV/decade, and an exceptional low overpotential of ~180 mV at a current density of 100 mA cm(-2) with a mass loading density of 0.28 mg/cm(2). Meanwhile, a remarkable ORR catalytic activity was observed with a half-potential of 0.7 V and an onset potential of 0.8 V at 1600 rpm and a scan rate of 5 mV s(-1). More importantly, the urchin-like CoP NCs present superior stability and keep their catalytic activity for at least 10 000 CV cycles for HER in 0.5 M H2SO4 and over 30 000 s for ORR in 0.1 M KOH, which is ascribed to their robust three-dimensional structure. This urchin-like CoP NCs might be a promising replacement to the Pt-based electrocatalysts in water splitting and fuel cells. PMID:26474359

  20. Oxygen Evolution Reaction Dynamics, Faradaic Charge Efficiency, and the Active Metal Redox States of Ni-Fe Oxide Water Splitting Electrocatalysts.

    PubMed

    Görlin, Mikaela; Chernev, Petko; Ferreira de Araújo, Jorge; Reier, Tobias; Dresp, Sören; Paul, Benjamin; Krähnert, Ralph; Dau, Holger; Strasser, Peter

    2016-05-01

    Mixed Ni-Fe oxides are attractive anode catalysts for efficient water splitting in solar fuels reactors. Because of conflicting past reports, the catalytically active metal redox state of the catalyst has remained under debate. Here, we report an in operando quantitative deconvolution of the charge injected into the nanostructured Ni-Fe oxyhydroxide OER catalysts or into reaction product molecules. To achieve this, we explore the oxygen evolution reaction dynamics and the individual faradaic charge efficiencies using operando differential electrochemical mass spectrometry (DEMS). We further use X-ray absorption spectroscopy (XAS) under OER conditions at the Ni and Fe K-edges of the electrocatalysts to evaluate oxidation states and local atomic structure motifs. DEMS and XAS data consistently reveal that up to 75% of the Ni centers increase their oxidation state from +2 to +3, while up to 25% arrive in the +4 state for the NiOOH catalyst under OER catalysis. The Fe centers consistently remain in the +3 state, regardless of potential and composition. For mixed Ni100-xFex catalysts, where x exceeds 9 atomic %, the faradaic efficiency of O2 sharply increases from ∼30% to 90%, suggesting that Ni atoms largely remain in the oxidation state +2 under catalytic conditions. To reconcile the apparent low level of oxidized Ni in mixed Ni-Fe catalysts, we hypothesize that a kinetic competition between the (i) metal oxidation process and the (ii) metal reduction step during O2 release may account for an insignificant accumulation of detectable high-valent metal states if the reaction rate of process (ii) outweighs that of (i). We conclude that a discussion of the superior catalytic OER activity of Ni-FeOOH electrocatalysts in terms of surface catalysis and redox-inactive metal sites likely represents an oversimplification that fails to capture essential aspects of the synergisms at highly active Ni-Fe sites. PMID:27031737

  1. Identification of catalytic sites for oxygen reduction and oxygen evolution in N-doped graphene materials: Development of highly efficient metal-free bifunctional electrocatalyst

    PubMed Central

    Yang, Hong Bin; Miao, Jianwei; Hung, Sung-Fu; Chen, Jiazang; Tao, Hua Bing; Wang, Xizu; Zhang, Liping; Chen, Rong; Gao, Jiajian; Chen, Hao Ming; Dai, Liming; Liu, Bin

    2016-01-01

    Oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are critical to renewable energy conversion and storage technologies. Heteroatom-doped carbon nanomaterials have been reported to be efficient metal-free electrocatalysts for ORR in fuel cells for energy conversion, as well as ORR and OER in metal-air batteries for energy storage. We reported that metal-free three-dimensional (3D) graphene nanoribbon networks (N-GRW) doped with nitrogen exhibited superb bifunctional electrocatalytic activities for both ORR and OER, with an excellent stability in alkaline electrolytes (for example, KOH). For the first time, it was experimentally demonstrated that the electron-donating quaternary N sites were responsible for ORR, whereas the electron-withdrawing pyridinic N moieties in N-GRW served as active sites for OER. The unique 3D nanoarchitecture provided a high density of the ORR and OER active sites and facilitated the electrolyte and electron transports. As a result, the as-prepared N-GRW holds great potential as a low-cost, highly efficient air cathode in rechargeable metal-air batteries. Rechargeable zinc-air batteries with the N-GRW air electrode in a two-electrode configuration exhibited an open-circuit voltage of 1.46 V, a specific capacity of 873 mAh g−1, and a peak power density of 65 mW cm−2, which could be continuously charged and discharged with an excellent cycling stability. Our work should open up new avenues for the development of various carbon-based metal-free bifunctional electrocatalysts of practical significance. PMID:27152333

  2. Gaseous trichloroethylene removal using an electrochemically generated homogeneous low-valent ligand-free Co(I) electrocatalyst by electro-scrubbing.

    PubMed

    Muthuraman, G; Ramu, A G; Moon, I S

    2016-07-01

    The interest in heterogeneous Co(OH)2 electrocatalysts for energy applications has increased steadily. This study focused on a ligand-free homogeneous electrocatalyst for the degradation of gaseous trichloroethylene (TCE) in NaOH in a divided electrolytic cell. The initial electrolysis results revealed a change in the oxidation reduction potential (ORP) of [Co(II)(OH)4](2-) (Co(II)) from -267 mV to -800 mV on anodized Ti during electrolytic reduction identifies low-valent homogeneous [Co(I)(OH)4](3-)(Co(I)) formation in 10 M NaOH. Cyclic voltammetry analysis of Co(II) at different anodized electrodes, Ag, carbon and Ti, in a 10 M NaOH solution, showed no stripping like peak in the reverse scan only the Ti electrode, supporting the formation of low-valent Co(I). UV-vis spectral analysis of the electrolyzed solution showed an enhanced peak corresponding to metal-to-ligand transition, demonstrates Co(I) formation. Co(II) reduction reached a maximum yield of 18% at 30 mA cm(-2) on an anodized Ti cathode. For gaseous TCE removal, continuous mode electro-scrubbing was adopted and degradation was monitored using an online FTIR gas analyzer that showed 99.75% degradation of TCE in the presence of homogeneous Co(I). Three consecutive regenerations of Co(I) and degradation steps of TCE confirmed the possibility of industrial applications in a sustainable manner. PMID:26985874

  3. Role of Cu-Ion Doping in Cu-α-MnO2 Nanowire Electrocatalysts for the Oxygen Reduction Reaction

    SciTech Connect

    Davis, Danae J.; Lambert, Timothy N.; Vigil, Julian A.; Rodriguez, Mark A.; Brumbach, Michael T.; Coker, Eric N.; Limmer, Steven J.

    2014-07-09

    The role of Cu-ion doping in α-MnO2 electrocatalysts for the oxygen reduction reaction in alkaline electrolyte was investigated. Copper doped α-MnO2 nanowires (Cu-α-MnO2) were prepared with varying amounts of Cu2+ using a solvothermal method. The electrocatalytic dataindicates that Cu-α-MnO2 nanowires have higher terminal current densities, enhanced kinetic rate constants, and improved charge transfer resistances that trend with Cu-content, exceeding values attained by α-MnO2 alone. The observed improvement in catalytic behavior correlates with an increase in Mn3+ content for the Cu-α-MnO2 nanowires. The Mn3+/Mn4+ couple is themediator for the rate-limiting redox driven O2-/OH- exchange. It is proposed that O2 adsorbs viaan axial site (the eg orbital on the Mn3+ d4 ion) at the surface, or at edge defects, of the nanowireand that the increase in covalent nature of the nanowire with Cu-ion doping leads to stabilization of O2 adsorbates and faster rates of reduction. This work is applicable to other manganese oxide electrocatalysts and shows for the first time there is a correlation for manganese oxides between electrocatalytic activity for the ORR in alkaline electrolyte and an increase in Mn3+ character of the oxide.

  4. Identification of catalytic sites for oxygen reduction and oxygen evolution in N-doped graphene materials: Development of highly efficient metal-free bifunctional electrocatalyst.

    PubMed

    Yang, Hong Bin; Miao, Jianwei; Hung, Sung-Fu; Chen, Jiazang; Tao, Hua Bing; Wang, Xizu; Zhang, Liping; Chen, Rong; Gao, Jiajian; Chen, Hao Ming; Dai, Liming; Liu, Bin

    2016-04-01

    Oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are critical to renewable energy conversion and storage technologies. Heteroatom-doped carbon nanomaterials have been reported to be efficient metal-free electrocatalysts for ORR in fuel cells for energy conversion, as well as ORR and OER in metal-air batteries for energy storage. We reported that metal-free three-dimensional (3D) graphene nanoribbon networks (N-GRW) doped with nitrogen exhibited superb bifunctional electrocatalytic activities for both ORR and OER, with an excellent stability in alkaline electrolytes (for example, KOH). For the first time, it was experimentally demonstrated that the electron-donating quaternary N sites were responsible for ORR, whereas the electron-withdrawing pyridinic N moieties in N-GRW served as active sites for OER. The unique 3D nanoarchitecture provided a high density of the ORR and OER active sites and facilitated the electrolyte and electron transports. As a result, the as-prepared N-GRW holds great potential as a low-cost, highly efficient air cathode in rechargeable metal-air batteries. Rechargeable zinc-air batteries with the N-GRW air electrode in a two-electrode configuration exhibited an open-circuit voltage of 1.46 V, a specific capacity of 873 mAh g(-1), and a peak power density of 65 mW cm(-2), which could be continuously charged and discharged with an excellent cycling stability. Our work should open up new avenues for the development of various carbon-based metal-free bifunctional electrocatalysts of practical significance. PMID:27152333

  5. Universal Strategy to Fabricate a Two-Dimensional Layered Mesoporous Mo2C Electrocatalyst Hybridized on Graphene Sheets with High Activity and Durability for Hydrogen Generation.

    PubMed

    Huo, Lili; Liu, Baocang; Zhang, Geng; Zhang, Jun

    2016-07-20

    A universal strategy was developed for fabrication of a highly active and durable precious-metal-free mesoporous Mo2C/graphene (m-Mo2C/G) electrocatalyst with a two-dimensional layered structural feature via a nanocasting method using glucose as a carbon source and an in-stiu assembled mesoporous KIT-6/graphene (KIT-6/G) as a template. The m-Mo2C/G catalyst exhibits high catalytic activity and excellent durability for hydrogen evolution reaction (HER) over a wide pH range, which displays a small onset potential of 8 mV, owerpotential (η10) for driving a cathodic current density of 10 mA·cm(-2) of 135 mV, a Tafel slope of 58 mV·dec(-1), and an exchange current density of 6.31 × 10(-2) mA·cm(-2) in acidic media and an onset potential of of 41 mV, η10 of 128 mV, Tafel slope of 56 mV·dec(-1), and an exchange current density of 4.09 × 10(-2) mA·cm(-2) in alkaline media, respectively. Furthermore, such an m-Mo2C/G electrocatalyst also gives about 100% Faradaic yield and shows excellent durability during 3000 cycles of a long-term test, and the catalytic current remains stable over 20 h at fixed overpotentials, making it a great potential application prospect for energy issues. PMID:27334022

  6. Beyond the active site: the impact of the outer coordination sphere on electrocatalysts for hydrogen production and oxidation.

    PubMed

    Ginovska-Pangovska, Bojana; Dutta, Arnab; Reback, Matthew L; Linehan, John C; Shaw, Wendy J

    2014-08-19

    Redox active metalloenzymes play a major role in energy transformation reactions in biological systems. Examples include formate dehydrogenases, nitrogenases, CO dehydrogenase, and hydrogenases. Many of these reactions are also of interest to humans as potential energy storage or utilization reactions for photoelectrochemical, electrolytic, and fuel cell applications. These metalloenzymes consist of redox active metal centers where substrates are activated and undergo transformation to products accompanied by electron and proton transfer to or from the substrate. These active sites are typically buried deep within a protein matrix of the enzyme with channels for proton transport, electron transport, and substrate/product transport between the active site and the surface of the protein. In addition, there are amino acid residues that lie in close proximity to the active site that are thought to play important roles in regulating and enhancing enzyme activity. Directly studying the outer coordination sphere of enzymes can be challenging due to their complexity, and the use of modified molecular catalysts may allow us to provide some insight. There are two fundamentally different approaches to understand these important interactions. The "bottom-up" approach involves building an amino acid or peptide containing outer coordination sphere around a functional molecular catalyst, and the "top-down" approach involves attaching molecular catalyst to a structured protein. Both of these approaches have been undertaken for hydrogenase mimics and are the emphasis of this Account. Our focus has been to utilize amino acid or peptide based scaffolds on an active functional enzyme mimic for H2 oxidation and production, [Ni(P(R)2N(R('))2)2](2+). This "bottom-up" approach has allowed us to evaluate individual functional group and structural contributions to electrocatalysts for H2 oxidation and production. For instance, using amine, ether, and carboxylic acid functionalities in the

  7. Electrocatalyst for oxygen reduction

    NASA Technical Reports Server (NTRS)

    Swette, L. L. (Inventor)

    1971-01-01

    The performance and costs of an electrochemical catalyst as compared to a pure platinum catalyst is evaluated. The catalysts are used to reduce oxygen in low temperature alkaline fuel cells. The electrochemical catalyst is composed of silver and platinum and is dispersed in a resinous inert binder to provide a cell electrode. The results indicate the electrochemical catalyst is superior structurally to the platinum one for high current density operation, and is at least as active as the platinum catalyst in other operations.

  8. Surface-Tuned Co3O4 Nanoparticles Dispersed on Nitrogen-Doped Graphene as an Efficient Cathode Electrocatalyst for Mechanical Rechargeable Zinc-Air Battery Application.

    PubMed

    Singh, Santosh K; Dhavale, Vishal M; Kurungot, Sreekumar

    2015-09-30

    The most vital component of the fuel cells and metal-air batteries is the electrocatalyst, which can facilitate the oxygen reduction reaction (ORR) at a significantly reduced overpotential. The present work deals with the development of surface-tuned cobalt oxide (Co3O4) nanoparticles dispersed on nitrogen-doped graphene as a potential ORR electrocatalyst possessing some unique advantages. The thermally reduced nitrogen-doped graphene (NGr) was decorated with three different morphologies of Co3O4 nanoparticles, viz., cubic, blunt edged cubic, and spherical, by using a simple hydrothermal method. We found that the spherical Co3O4 nanoparticle supported NGr catalyst (Co3O4-SP/NGr-24h) has acquired a significant activity makeover to display the ORR activity closely matching with the state-of-the-art Pt supported carbon (PtC) catalyst in alkaline medium. Subsequently, the Co3O4-SP/NGr-24h catalyst has been utilized as the air electrode in a Zn-air battery, which was found to show comparable performance to the system derived from PtC. Co3O4-SP/NGr-24h catalyst has shown several hours of flat discharge profile at the discharge rates of 10, 20, and 50 mA/cm(2) with a specific capacity and energy density of ~590 mAh/g-Zn and ~840 Wh/kg-Zn, respectively, in the primary Zn-air battery system. In conjunction, Co3O4-SP/NGr-24h has outperformed as an air electrode in mechanical rechargeable Zn-air battery as well, which has shown consistent flat discharge profile with minimal voltage loss at a discharge rate of 50 mA/cm(2). The present results, thus demonstrate that the proper combination of the tuned morphology of Co3O4 with NGr will be a promising and inexpensive material for efficient and ecofriendly cathodes for Zn-air batteries. PMID:26376490

  9. Bottom-up synthesis of high-performance nitrogen-enriched transition metal/graphene oxygen reduction electrocatalysts both in alkaline and acidic solution

    NASA Astrophysics Data System (ADS)

    Lai, Qingxue; Gao, Qingwen; Su, Qi; Liang, Yanyu; Wang, Yuxi; Yang, Zhi

    2015-08-01

    Oxygen reduction electrocatalysts with low cost and excellent performance are urgently required for large-scale application in fuel cells and metal-air batteries. Though nitrogen-enriched transition metal/graphene hybrids (N-TM/G, TM = Fe, Co, and Ni and related compounds) have been developed as novel substitutes for precious metal catalysts (PMCs) towards oxygen reduction reaction (ORR), a significant challenge still remains for simple and efficient synthesis of N-TM/G catalysts with satisfactory electrocatalytic behavior. Herein, we demonstrate a universal bottom-up strategy for efficient fabrication of strongly-coupled N-TM/G catalysts. This strategy is implemented via direct polymerization of transition metal phthalocyanine (TMPc) in the two-dimensional confined space of in situ generated g-C3N4 and a subsequent pyrolysis. Such a space-confined bottom-up synthesis route successfully constructs a strongly-coupled triple junction of transition metal-graphitic carbon-nitrogen-doped graphene (TM-GC-NG) with extensive controllability over the specific surface area, nitrogen content/types as well as the states of metal. As a result, the optimized N-Fe/G materials have promising potential as high-performance NPMCs towards ORR both in alkaline and acidic solution.Oxygen reduction electrocatalysts with low cost and excellent performance are urgently required for large-scale application in fuel cells and metal-air batteries. Though nitrogen-enriched transition metal/graphene hybrids (N-TM/G, TM = Fe, Co, and Ni and related compounds) have been developed as novel substitutes for precious metal catalysts (PMCs) towards oxygen reduction reaction (ORR), a significant challenge still remains for simple and efficient synthesis of N-TM/G catalysts with satisfactory electrocatalytic behavior. Herein, we demonstrate a universal bottom-up strategy for efficient fabrication of strongly-coupled N-TM/G catalysts. This strategy is implemented via direct polymerization of transition

  10. Sulfur-doped porous reduced graphene oxide hollow nanosphere frameworks as metal-free electrocatalysts for oxygen reduction reaction and as supercapacitor electrode materials

    NASA Astrophysics Data System (ADS)

    Chen, Xi'an; Chen, Xiaohua; Xu, Xin; Yang, Zhi; Liu, Zheng; Zhang, Lijie; Xu, Xiangju; Chen, Ying; Huang, Shaoming

    2014-10-01

    Chemical doping with foreign atoms is an effective approach to significantly enhance the electrochemical performance of the carbon materials. Herein, sulfur-doped three-dimensional (3D) porous reduced graphene oxide (RGO) hollow nanosphere frameworks (S-PGHS) are fabricated by directly annealing graphene oxide (GO)-encapsulated amino-modified SiO2 nanoparticles with dibenzyl disulfide (DBDS), followed by hydrofluoric acid etching. The XPS and Raman spectra confirmed that sulfur atoms were successfully introduced into the PGHS framework via covalent bonds. The as-prepared S-PGHS has been demonstrated to be an efficient metal-free electrocatalyst for oxygen reduction reaction (ORR) with the activity comparable to that of commercial Pt/C (40%) and much better methanol tolerance and durability, and to be a supercapacitor electrode material with a high specific capacitance of 343 F g-1, good rate capability and excellent cycling stability in aqueous electrolytes. The impressive performance for ORR and supercapacitors is believed to be due to the synergistic effect caused by sulfur-doping enhancing the electrochemical activity and 3D porous hollow nanosphere framework structures facilitating ion diffusion and electronic transfer.Chemical doping with foreign atoms is an effective approach to significantly enhance the electrochemical performance of the carbon materials. Herein, sulfur-doped three-dimensional (3D) porous reduced graphene oxide (RGO) hollow nanosphere frameworks (S-PGHS) are fabricated by directly annealing graphene oxide (GO)-encapsulated amino-modified SiO2 nanoparticles with dibenzyl disulfide (DBDS), followed by hydrofluoric acid etching. The XPS and Raman spectra confirmed that sulfur atoms were successfully introduced into the PGHS framework via covalent bonds. The as-prepared S-PGHS has been demonstrated to be an efficient metal-free electrocatalyst for oxygen reduction reaction (ORR) with the activity comparable to that of commercial Pt/C (40%) and

  11. Cobalt-polypyrrole-carbon black (Co-PPY-CB) Electrocatalysts for the Oxygen Reduction Reaction (ORR) in Fuel Cells: Composition and Kinetic Activity

    SciTech Connect

    D Nguyen-Thanh; A Frenkel; J Wang; S OBrien; D Akins

    2011-12-31

    Electrocatalysts consisting of polypyrrole (PPY) and Co deposited on carbon black (CB) at several compositions were prepared and tested for the oxygen reduction reaction (ORR) in a HClO4 buffer (pH = 1) using a rotating ring-disk electrode (RRDE). It was determined that the most favorable catalyst composition (prior to calcination) had a CB:PPY weight ratio of 2 and a pyrrole:Co (i.e., PY:Co) molar ratio of 4. This catalyst had an onset potential of 0.785 V (vs. RHE) and a mass activity of ca. 1 A/g{sub cata} at the fuel cell relevant voltage of 0.65 V. Furthermore, it was found that the number of electrons exchanged during the ORR with the catalyst was ca. 3.5 and resulted in 28% yield of H{sub 2}O{sub 2} at 0.65 V, which hints to an indirect 4e{sup -} reduction of O{sub 2} to H{sub 2}O, with H{sub 2}O{sub 2} as an intermdiate. From energy dispersive spectroscopy (EDS) and extended X-ray absorption fine structure (EXAFS) analysis, it is proposed that a PY:Co ratio of 4 favors the formation, prior to calcination, in the catalyst precursor of Co-N complexes in which Co is coordinated to 3 or 4 N atoms, resulting in strong Co-N interactions that limit the formation upon calcination of low ORR activity Co nanoparticles. These Co-N complexes give rise upon calcination to CoN{sub x-2} sites in which the coordination of Co could favor the adsorption on them of O{sub 2}, which would make those sites particularly active and selective. At the same mass acitivity of 1 A/g{sub cata}, the voltage yielded by the catalyst was 200 mV lower than that for a state-of-the-art Pt (10 wt.%) catalyst, whoch H{sub 2}O{sub 2} output at 0.85 V was 39% and involves the exchange of 3.2 e{sup -}, overall making our material an attractive substitute to noble metal ORR electrocatalysts.

  12. Oxygen Reduction Reaction Measurements on Platinum Electrocatalysts Utilizing Rotating Disk Electrode Technique: I. Impact of Impurities, Measurement Protocols and Applied Corrections

    SciTech Connect

    Shinozaki, Kazuma; Zack, Jason W.; Richards, Ryan M.; Pivovar, Bryan S.; Kocha, Shyam S.

    2015-07-22

    The rotating disk electrode (RDE) technique is being extensively used as a screening tool to estimate the activity of novel PEMFC electrocatalysts synthesized in lab-scale (mg) quantities. Discrepancies in measured activity attributable to glassware and electrolyte impurity levels, as well as conditioning, protocols and corrections are prevalent in the literature. Moreover, the electrochemical response to a broad spectrum of commercially sourced perchloric acid and the effect of acid molarity on impurity levels and solution resistance were also assessed. Our findings reveal that an area specific activity (SA) exceeding 2.0 mA/cm2 (20 mV/s, 25°C, 100 kPa, 0.1 M HClO4) for polished poly-Pt is an indicator of impurity levels that do not impede the accurate measurement of the ORR activity of Pt based catalysts. After exploring various conditioning protocols to approach maximum utilization of the electrochemical area (ECA) and peak ORR activity without introducing catalyst degradation, an investigation of measurement protocols for ECA and ORR activity was conducted. Down-selected protocols were based on the criteria of reproducibility, duration of experiments, impurity effects and magnitude of pseudo-capacitive background correction. In sum, statistical reproducibility of ORR activity for poly-Pt and Pt supported on high surface area carbon was demonstrated.

  13. Highly Platinum-Loaded Magnéli Phase Titanium Oxides as a High Voltage Tolerant Electrocatalyst for Polymer Electrolyte Fuel Cells.

    PubMed

    Dogan, Didem C; Hwang, Sun-Mi; Jang, Eun-Hwa; Yim, Sung-Dae; Sohn, Young-Jun; Kim, Sung-Hyun; Yang, Tae-Hyun; Park, Gu-Gon

    2015-09-01

    Magnéli phase titanium oxides (MPTOs), possess high electrical conductivity and chemical stability, are promising support materials for the development of novel electrocatalyst in polymer electrolyte fuel cells (PEFCs). Despite MPTO's extremely low specific surface area (1 m2/g or less), high Pt loading (40 wt%) and excellent Pt particle-size distribution were obtained by the modified borohydride method. The reasons were discussed and compared with polyol method. Membrane electrode assembly (MEA) performance of those Pt/MPTO catalysts were found to be 169.7 and 366.2 mA/cm2 at 0.7 V for H2/air and H2/O2, respectively. The accelerated stress tests (ASTs) showed superior durability of the Pt/MPTO catalyst as a cathode electrode. After 10,000 cycles of high-voltage cycling test from 0.9 V and 1.3 V RHE, no significant performance degradation of the Pt/MPTO electrode was observed comparing with Pt/C. Thus, MPTOs can be considered as a good substitute of carbon supports in fuel cells. PMID:26716272

  14. Efficient NiSe-Ni3Se2/Graphene Electrocatalyst in Dye-Sensitized Solar Cells: The Role of Hollow Hybrid Nanostructure.

    PubMed

    Zhang, Xiao; Zhen, Mengmeng; Bai, Jinwu; Jin, Shaowei; Liu, Lu

    2016-07-13

    Hollow and hybrid nanomaterials are excellent electrocatalysts on account of their novel electrocatalytic properties compared with homogeneous solid nanostructures. In this report, NiSe-Ni3Se2 hybrid nanostructure with morphology of hollow hexagonal nanodisk was synthesized in situ on graphene. A series of NiSe-Ni3Se2/RGO with different phase constitutions and nanostructures were obtained by controlling the durations of solvothermal treatment. Because of their unique hollow and hybrid structure, NiSe-Ni3Se2/RGO hollow nanodisks exhibited higher electrocatalytic performance than NiSe/RGO and solid NiSe-Ni3Se2/RGO nanostructure for reducing I3(-) as counter cell (CE) of dye-sensitized solar cells (DSSCs). Additionally, NiSe-Ni3Se2/RGO hollow nanodisks achieved much lower charge transfer resistance (Rct = 0.68 Ω) and higher power conversion efficiency (PCE) (7.87%) than those of Pt (Rct = 1.41 Ω, PCE = 7.28%). PMID:27314283

  15. Three dimensional nickel oxides/nickel structure by in situ electro-oxidation of nickel foam as robust electrocatalyst for oxygen evolution reaction

    NASA Astrophysics Data System (ADS)

    Han, Guan-Qun; Liu, Yan-Ru; Hu, Wen-Hui; Dong, Bin; Li, Xiao; Shang, Xiao; Chai, Yong-Ming; Liu, Yun-Qi; Liu, Chen-Guang

    2015-12-01

    Three dimensional (3D) nickel oxide/nickel (NiOx/Ni) structure has been synthesized through a facile in situ electro-oxidation method. The formation of NiOx through the electro-oxidation process has been proved by SEM and EDX, with some dense black dots appearing on the surface of Ni foam and the molar ratio of O/Ni increasing, which is nearly 7 times larger than the pure Ni foam. The increase in O content indicates the formatted black particles on the surface of Ni foam are composed of NiOx. The electrocatalytic property of the obtained 3D NiOx/Ni structure has been measured and it can be used as a highly active electrocatalyst for oxygen evolution reaction (OER). The overpotential to reach j = 10 mA cm-2 is 0.39 V. And after the long-term I-t measurement, extremely high electrochemical and physical stability are exhibited in the 3D structure, keeping electrochemical activity and morphology the same. The excellent OER properties may be attributed to the 3D structure and the interface effect of NiOx/Ni.

  16. A Nanopore-Structured Nitrogen-Doped Biocarbon Electrocatalyst for Oxygen Reduction from Two-Step Carbonization of Lemna minor Biomass.

    PubMed

    Guo, Chaozhong; Li, Zhongbin; Niu, Lidan; Liao, Wenli; Sun, Lingtao; Wen, Bixia; Nie, Yunqing; Cheng, Jing; Chen, Changguo

    2016-12-01

    So far, the development of highly active and stable carbon-based electrocatalysts for oxygen reduction reaction (ORR) to replace commercial Pt/C catalyst is a hot topic. In this study, a new nanoporous nitrogen-doped carbon material was facilely designed by two-step pyrolysis of the renewable Lemna minor enriched in crude protein under a nitrogen atmosphere. Electrochemical measurements show that the onset potential for ORR on this carbon material is around 0.93 V (versus reversible hydrogen electrode), slightly lower than that on the Pt/C catalyst, but its cycling stability is higher compared to the Pt/C catalyst in an alkaline medium. Besides, the ORR at this catalyst approaches to a four-electron transfer pathway. The obtained ORR performance can be basically attributed to the formation of high contents of pyridinic and graphitic nitrogen atoms inside this catalyst. Thus, this work opens up the path in the ORR catalysis for the design of nitrogen-doped carbon materials utilizing aquatic plants as starting precursors. PMID:27225424

  17. RuO2 nanoparticles decorated MnOOH/C as effective bifunctional electrocatalysts for lithium-air battery cathodes with long-cycling stability

    NASA Astrophysics Data System (ADS)

    Kim, Gil-Pyo; Lim, Dongwook; Park, Inyeong; Park, Hyelee; Shim, Sang Eun; Baeck, Sung-Hyeon

    2016-08-01

    Manganite (MnOOH) is one of the most effective electrocatalysts for oxygen reduction reaction (ORR), and RuO2 nanoparticles exhibit high activity for oxygen evolution reaction (OER). We herein report a facile means of producing well dispersed RuO2/MnOOH on Ketjen black (RuO2/MnOOH/C) as a bifunctional catalyst for lithium-air (Li-air) batteries. RuO2/MnOOH/C was simply synthesized using a hydrothermal/precipitation based method, and was used as a cathode for a Li-air battery using a Swagelok-type cell. The importance of dispersing active catalysts on a carbon support was clearly demonstrated by textural, charge-discharge voltammetric, and electrochemical impedance spectroscopic (EIS) analyses, comparing results with a catalyst produced by physically mixing RuO2/MnOOH with carbon (RuO2/MnOOH + C). RuO2/MnOOH/C showed low overpotential and stable cycleability up to 170th cycles with 1000 mAh g-1 of charge-discharge capacity, which was attributed to its enhanced active surface area and low charge-transfer resistance. The results obtained suggest that this strategy can be widely applied to bifunctional electrocatalysis, such as secondary batteries and regenerative fuel cell (RFC).

  18. Facile synthesis of N-rich carbon quantum dots by spontaneous polymerization and incision of solvents as efficient bioimaging probes and advanced electrocatalysts for oxygen reduction reaction.

    PubMed

    Lei, Zhouyue; Xu, Shengjie; Wan, Jiaxun; Wu, Peiyi

    2016-01-28

    In this study, uniform nitrogen-doped carbon quantum dots (N-CDs) were synthesized through a one-step solvothermal process of cyclic and nitrogen-rich solvents, such as N-methyl-2-pyrrolidone (NMP) and dimethyl-imidazolidinone (DMEU), under mild conditions. The products exhibited strong light blue fluorescence, good cell permeability and low cytotoxicity. Moreover, after a facile post-thermal treatment, it developed a lotus seedpod surface-like structure of seed-like N-CDs decorating on the surface of carbon layers with a high proportion of quaternary nitrogen moieties that exhibited excellent electrocatalytic activity and long-term durability towards the oxygen reduction reaction (ORR). The peak potential was -160 mV, which was comparable to or even lower than commercial Pt/C catalysts. Therefore, this study provides an alternative facile approach to the synthesis of versatile carbon quantum dots (CDs) with widespread commercial application prospects, not only as bioimaging probes but also as promising electrocatalysts for the metal-free ORR. PMID:26739885

  19. 3,4,9,10-perylenetetracarboxylic acid/hemin nanocomposites act as redox probes and electrocatalysts for constructing a pseudobienzyme-channeling amplified electrochemical aptasensor.

    PubMed

    Yuan, Yali; Yuan, Ruo; Chai, Yaqin; Zhuo, Ying; Gan, Xianxue; Bai, Lijuan

    2012-10-29

    A simple wet-chemical strategy for the synthesis of 3,4,9,10-perylenetetracarboxylic acid (PTCA)/hemin nanocomposites through π-π interactions is demonstrated. Significantly, the hemin successfully conciliates PTCA redox activity with a pair of well-defined redox peaks and intrinsic peroxidase-like activity, which provides potential application of the PTCA self-derived redox activity as redox probes. Additionally, PTCA/hemin nanocomposites exhibit a good membrane-forming property, which not only avoids the conventional fussy process for redox probe immobilization, but also reduces the participation of the membrane materials that act as a barrier of electron transfer. On the basis of these unique properties, a pseudobienzyme-channeling amplified electrochemical aptasensor is developed that is coupled with glucose oxidase (GOx) for thrombin detection by using PTCA/hemin nanocomposites as redox probes and electrocatalysts. With the addition of glucose to the electrolytic cell, the GOx on the aptasensor surface bioelectrocatalyzed the reduction of glucose to produce H(2)O(2), which in turn was electrocatalyzed by the PTCA/hemin nanocomposites. Cascade schemes, in which an enzyme is catalytically linked to another enzyme, can produce signal amplification and therefore increase the biosensor sensitivity. As a result, a linear relationship for thrombin from 0.005 to 20 nM and a detection limit of 0.001 nM were obtained. PMID:23001991

  20. Evidence from in Situ X-ray Absorption Spectroscopy for the Involvement of Terminal Disulfide in the Reduction of Protons by an Amorphous Molybdenum Sulfide Electrocatalyst

    PubMed Central

    2015-01-01

    The reduction of protons into dihydrogen is important because of its potential use in a wide range of energy applications. The preparation of efficient and cheap catalysts for this reaction is one of the issues that need to be tackled to allow the widespread use of hydrogen as an energy carrier. In this paper, we report the study of an amorphous molybdenum sulfide (MoSx) proton reducing electrocatalyst under functional conditions, using in situ X-ray absorption spectroscopy. We probed the local and electronic structures of both the molybdenum and sulfur elements for the as prepared material as well as the precatalytic and catalytic states. The as prepared material is very similar to MoS3 and remains unmodified under functional conditions (pH = 2 aqueous HNO3) in the precatalytic state (+0.3 V vs RHE). In its catalytic state (−0.3 V vs RHE), the film is reduced to an amorphous form of MoS2 and shows spectroscopic features that indicate the presence of terminal disulfide units. These units are formed concomitantly with the release of hydrogen, and we suggest that the rate-limiting step of the HER is the reduction and protonation of these disulfide units. These results show the implication of terminal disulfide chemical motifs into HER driven by transition-metal sulfides and provide insight into their reaction mechanism. PMID:25427231

  1. Effect of pretreatment atmosphere on the particle size and oxygen reduction activity of low-loading platinum impregnated titanium carbide powder electrocatalysts

    NASA Astrophysics Data System (ADS)

    Yang, Leerang; Kimmel, Yannick C.; Lu, Qi; Chen, Jingguang G.

    2015-08-01

    Low-loading Pt supported on TiC powder catalysts were synthesized by an impregnation method. After the Pt(NH3)4(NO3)2 precursor was impregnated onto the TiC support, different pretreatment atmospheres were used to study the influence on Pt dispersion, surface composition, and catalytic activity towards oxygen reduction reaction (ORR). Direct reduction of the Pt precursor in hydrogen led to small Pt particles with an average size of ∼2.2 nm and superior ORR activity at low overpotential compared to commercial Pt/C. However, calcination of the Pt precursor in air resulted in larger Pt particles with an average size of ∼6.7 nm and lower ORR specific activity. The decrease in ORR activity was primarily attributed to the surface oxidation of the TiC support during calcination. X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) confirmed that the TiC powder was oxidized when the catalyst was calcined in air. The finding reported here demonstrates the importance of pretreatment atmosphere for synthesizing Pt-modified transition metal carbides as highly active electrocatalysts.

  2. Carbon nanotubes/heteroatom-doped carbon core-sheath nanostructures as highly active, metal-free oxygen reduction electrocatalysts for alkaline fuel cells.

    PubMed

    Sa, Young Jin; Park, Chiyoung; Jeong, Hu Young; Park, Seok-Hee; Lee, Zonghoon; Kim, Kyoung Taek; Park, Gu-Gon; Joo, Sang Hoon

    2014-04-14

    A facile, scalable route to new nanocomposites that are based on carbon nanotubes/heteroatom-doped carbon (CNT/HDC) core-sheath nanostructures is reported. These nanostructures were prepared by the adsorption of heteroatom-containing ionic liquids on the walls of CNTs, followed by carbonization. The design of the CNT/HDC composite allows for combining the electrical conductivity of the CNTs with the catalytic activity of the heteroatom-containing HDC sheath layers. The CNT/HDC nanostructures are highly active electrocatalysts for the oxygen reduction reaction and displayed one of the best performances among heteroatom-doped nanocarbon catalysts in terms of half-wave potential and kinetic current density. The four-electron selectivity and the exchange current density of the CNT/HDC nanostructures are comparable with those of a Pt/C catalyst, and the CNT/HDC composites were superior to Pt/C in terms of long-term durability and poison tolerance. Furthermore, an alkaline fuel cell that employs a CNT/HDC nanostructure as the cathode catalyst shows very high current and power densities, which sheds light on the practical applicability of these new nanocomposites. PMID:24554521

  3. Screening of electrocatalysts for direct ammonia fuel cell: Ammonia oxidation on PtMe (Me: Ir, Rh, Pd, Ru) and preferentially oriented Pt(1 0 0) nanoparticles

    NASA Astrophysics Data System (ADS)

    Vidal-Iglesias, F. J.; Solla-Gullón, J.; Montiel, V.; Feliu, J. M.; Aldaz, A.

    Ammonia has attracted attention as a possible fuel for direct fuel cells since it is easy to handle and to transport as liquid or as concentrated aqueous solution. However, on noble metal electrodes ammonia oxidation is a sluggish reaction and the electrocatalyst needs to be improved for developing efficient ammonia fuel cells. In this work, ammonia electrooxidation reaction on 3-4-nm bimetallic PtMe (Ir, Rh, Pd, Ru) and on preferentially oriented Pt(1 0 0) nanoparticles is reported. PtMe nanoparticles have been prepared by using water-in-oil microemulsions to obtain a narrow size distribution whereas preferentially oriented Pt nanoparticles have been prepared through colloidal routes. Among all the bimetallic samples tested, only Pt 75Ir 25 and Pt 75Rh 25 nanoparticles show, at the low potential range, an enhancement of the oxidation density current with respect to the behaviour found for pure platinum nanoparticles prepared by the same method. In addition, two Pt(1 0 0) preferentially oriented nanoparticles of different particle size (4 and 9 nm) have been also studied. These oriented nanoparticles show higher current densities than polycrystalline Pt nanoparticles due to the sensitivity of ammonia oxidation toward the presence of surface sites with square symmetry. The reactivity of the different 4-nm nanoparticles parallels well with that expected from bulk PtMe alloys and Pt single crystal electrodes.

  4. Bottom-up synthesis of high-performance nitrogen-enriched transition metal/graphene oxygen reduction electrocatalysts both in alkaline and acidic solution.

    PubMed

    Lai, Qingxue; Gao, Qingwen; Su, Qi; Liang, Yanyu; Wang, Yuxi; Yang, Zhi

    2015-09-21

    Oxygen reduction electrocatalysts with low cost and excellent performance are urgently required for large-scale application in fuel cells and metal-air batteries. Though nitrogen-enriched transition metal/graphene hybrids (N-TM/G, TM = Fe, Co, and Ni and related compounds) have been developed as novel substitutes for precious metal catalysts (PMCs) towards oxygen reduction reaction (ORR), a significant challenge still remains for simple and efficient synthesis of N-TM/G catalysts with satisfactory electrocatalytic behavior. Herein, we demonstrate a universal bottom-up strategy for efficient fabrication of strongly-coupled N-TM/G catalysts. This strategy is implemented via direct polymerization of transition metal phthalocyanine (TMPc) in the two-dimensional confined space of in situ generated g-C3N4 and a subsequent pyrolysis. Such a space-confined bottom-up synthesis route successfully constructs a strongly-coupled triple junction of transition metal-graphitic carbon-nitrogen-doped graphene (TM-GC-NG) with extensive controllability over the specific surface area, nitrogen content/types as well as the states of metal. As a result, the optimized N-Fe/G materials have promising potential as high-performance NPMCs towards ORR both in alkaline and acidic solution. PMID:26282404

  5. In situ growth of NixSy controlled by surface treatment of nickel foam as efficient electrocatalyst for oxygen evolution reaction

    NASA Astrophysics Data System (ADS)

    Shang, Xiao; Li, Xiao; Hu, Wen-Hui; Dong, Bin; Liu, Yan-Ru; Han, Guan-Qun; Chai, Yong-Ming; Liu, Yun-Qi; Liu, Chen-Guang

    2016-08-01

    In situ growth of NixSy with different crystal phases supported on different surface-treated (acidification or oxidation) nickel foam (NF) has been successfully achieved by a facile solvothermal process. XRD and SEM results show that crystal phase and morphology of NixSy have been greatly affected by the surface treatment of NF. XRD results show that the mixture crystal phases of NixSy have been obtained on both acid-treated NF (NF(a)) and oxidant treated NF (NF(o)). NixSy/NF(a) contains Ni3S2 and NiS, whereas NixSy/NF(o) has Ni3S2 and NiS2, implying different crystal phases derived from different surface treatment of NF. SEM images also reveal the different morphology of two samples based on pre-treatment support. NixSy/NF(a) displays unique conical agglomeration surrounded by porous structure. NixSy/NF(o) has the disorder stacking structure of nanosheets. Electrochemical measurements for oxygen evolution reaction (OER) show the enhanced performances of NixSy/NF(a) than NixSy/NF(o) and pure Ni3S2/NF as contrast samples, implying that NiS outperforms other types of NixSy. The mechanisms of sulfurization path of different surface-treated NF have been discussed. The facile surface treatment of NF may provide a new strategy to prepare excellent electrocatalysts for OER.

  6. N- and S-doped high surface area carbon derived from soya chunks as scalable and efficient electrocatalysts for oxygen reduction

    NASA Astrophysics Data System (ADS)

    Rana, Moumita; Arora, Gunjan; Gautam, Ujjal K.

    2015-02-01

    Highly stable, cost-effective electrocatalysts facilitating oxygen reduction are crucial for the commercialization of membrane-based fuel cell and battery technologies. Herein, we demonstrate that protein-rich soya chunks with a high content of N, S and P atoms are an excellent precursor for heteroatom-doped highly graphitized carbon materials. The materials are nanoporous, with a surface area exceeding 1000 m2 g-1, and they are tunable in doping quantities. These materials exhibit highly efficient catalytic performance toward oxygen reduction reaction (ORR) with an onset potential of -0.045 V and a half-wave potential of -0.211 V (versus a saturated calomel electrode) in a basic medium, which is comparable to commercial Pt catalysts and is better than other recently developed metal-free carbon-based catalysts. These exhibit complete methanol tolerance and a performance degradation of merely ˜5% as compared to ˜14% for a commercial Pt/C catalyst after continuous use for 3000 s at the highest reduction current. We found that the fraction of graphitic N increases at a higher graphitization temperature, leading to the near complete reduction of oxygen. It is believed that due to the easy availability of the precursor and the possibility of genetic engineering to homogeneously control the heteroatom distribution, the synthetic strategy is easily scalable, with further improvement in performance.

  7. A Nanopore-Structured Nitrogen-Doped Biocarbon Electrocatalyst for Oxygen Reduction from Two-Step Carbonization of Lemna minor Biomass

    NASA Astrophysics Data System (ADS)

    Guo, Chaozhong; Li, Zhongbin; Niu, Lidan; Liao, Wenli; Sun, Lingtao; Wen, Bixia; Nie, Yunqing; Cheng, Jing; Chen, Changguo

    2016-05-01

    So far, the development of highly active and stable carbon-based electrocatalysts for oxygen reduction reaction (ORR) to replace commercial Pt/C catalyst is a hot topic. In this study, a new nanoporous nitrogen-doped carbon material was facilely designed by two-step pyrolysis of the renewable Lemna minor enriched in crude protein under a nitrogen atmosphere. Electrochemical measurements show that the onset potential for ORR on this carbon material is around 0.93 V (versus reversible hydrogen electrode), slightly lower than that on the Pt/C catalyst, but its cycling stability is higher compared to the Pt/C catalyst in an alkaline medium. Besides, the ORR at this catalyst approaches to a four-electron transfer pathway. The obtained ORR performance can be basically attributed to the formation of high contents of pyridinic and graphitic nitrogen atoms inside this catalyst. Thus, this work opens up the path in the ORR catalysis for the design of nitrogen-doped carbon materials utilizing aquatic plants as starting precursors.

  8. In situ photo-assisted deposition of MoS₂ electrocatalyst onto zinc cadmium sulphide nanoparticle surfaces to construct an efficient photocatalyst for hydrogen generation.

    PubMed

    Nguyen, Mai; Tran, Phong D; Pramana, Stevin S; Lee, Rui Lin; Batabyal, Sudip K; Mathews, Nripan; Wong, Lydia H; Graetzel, Michael

    2013-02-21

    We reported herein a facile and scalable preparation process for MoS(2)-decorated Zn(x)Cd(1-x)S hybrid photocatalysts for hydrogen generation. Zn(x)Cd(1-x)S nanopowder was first prepared from commercially available precursors employing a solution based process. MoS(2) hydrogen evolution reaction catalyst was then loaded onto the Zn(x)Cd(1-x)S nanopowder via a photo-assisted deposition process which employed mild conditions (room temperature, atmospheric pressure and visible light illumination). Thus, this process represents an important advantage in the large scale production of semiconductor/MoS(2) hybrid photocatalysts in comparison to the conventional method relying on thermal decomposition of (NH(4))(2)[MoS(4)] precursor at high temperature and under H(2)S pressure. The best Zn(0.2)Cd(0.8)S/MoS(2) 3% showed two hundred-and-ten times (210 times) faster hydrogen generation rate on visible light illumination compared with that obtained for un-treated Zn(0.2)Cd(0.8)S. That was the most impressive catalytic enhancement ever recorded for a semiconductor photocatalyst decorated with a noble metal free electrocatalyst. PMID:23334494

  9. Free MoS2 Nanoflowers Grown on Graphene by Microwave-Assisted Synthesis as Highly Efficient Non-Noble-Metal Electrocatalysts for the Hydrogen Evolution Reaction.

    PubMed

    Cao, Jiamu; Zhang, Xuelin; Zhang, Yufeng; Zhou, Jing; Chen, Yinuo; Liu, Xiaowei

    2016-01-01

    Advanced approaches to preparing non-noble-metal electrocatalysts for the hydrogen evolution reaction (HER) are considered to be a significant breakthrough in promoting the exploration of renewable resources. In this work, a hybrid material of MoS2 nanoflowers (NFs) on reduced graphene oxide (rGO) was synthesized as a HER catalyst via an environmentally friendly, efficient approach that is also suitable for mass production. Small-sized MoS2 NFs with a diameter of ca. 190 nm and an abundance of exposed edges were prepared by a hydrothermal method and were subsequently supported on rGO by microwave-assisted synthesis. The results show that MoS2 NFs were distributed uniformly on the remarkably reduced GO and preserved the outstanding original structural features perfectly. Electrochemical tests show that the as-prepared hybrid material exhibited excellent HER activity, with a small Tafel slope of 80 mV/decade and a low overpotential of 170 mV. PMID:27556402

  10. Nanoporous PdZr surface alloy as highly active non-platinum electrocatalyst toward oxygen reduction reaction with unique structure stability and methanol-tolerance

    NASA Astrophysics Data System (ADS)

    Duan, Huimei; Xu, Caixia

    2016-06-01

    Nanoporous (NP) PdZr alloy with controllable bimetallic ratio is successfully fabricated by a simple dealloying method. By leaching out the more reactive Al from PdZrAl precursor alloy, NP-PdZr alloy with smaller ligament size was generated, characterized by the nanoscaled interconnected network skeleton and hollow channels extending in all three dimensions. Upon voltammetric scan in acid solution, the dissolution of surface Zr atoms generates the highly active Pd-Zr surface alloy with a nearly pure Pd surface and Pd-Zr alloy core. The NP-Pd80Zr20 surface alloy exhibits markedly enhanced specific and mass activities as well as higher catalytic stability toward oxygen reduction reaction (ORR) compared with NP-Pd and the state-of-the-art Pt/C catalysts. In addition, the NP-Pd80Zr20 surface alloy shows a better selectivity for ORR than methanol in the 0.1 M HClO4 and 0.1 M methanol mixed solution. X-ray photoelectron spectroscopy and density functional theory calculations both demonstrate that the weakened Pd-O bond and improved ORR performances in turn depend on the downshifted d-band center of Pd due to the alloying Pd with Zr (20 at.%). The as-made NP-PdZr alloy holds prospective applications as a cathode electrocatalyst in fuel-cell-related technologies with the advantages of superior overall ORR performances, unique structure stability, and easy preparation.

  11. Free MoS2 Nanoflowers Grown on Graphene by Microwave-Assisted Synthesis as Highly Efficient Non-Noble-Metal Electrocatalysts for the Hydrogen Evolution Reaction

    PubMed Central

    Cao, Jiamu; Zhang, Xuelin; Zhang, Yufeng; Zhou, Jing; Chen, Yinuo; Liu, Xiaowei

    2016-01-01

    Advanced approaches to preparing non-noble-metal electrocatalysts for the hydrogen evolution reaction (HER) are considered to be a significant breakthrough in promoting the exploration of renewable resources. In this work, a hybrid material of MoS2 nanoflowers (NFs) on reduced graphene oxide (rGO) was synthesized as a HER catalyst via an environmentally friendly, efficient approach that is also suitable for mass production. Small-sized MoS2 NFs with a diameter of ca. 190 nm and an abundance of exposed edges were prepared by a hydrothermal method and were subsequently supported on rGO by microwave-assisted synthesis. The results show that MoS2 NFs were distributed uniformly on the remarkably reduced GO and preserved the outstanding original structural features perfectly. Electrochemical tests show that the as-prepared hybrid material exhibited excellent HER activity, with a small Tafel slope of 80 mV/decade and a low overpotential of 170 mV. PMID:27556402

  12. High performance fluorine doped (Sn,Ru)O2 oxygen evolution reaction electro-catalysts for proton exchange membrane based water electrolysis

    NASA Astrophysics Data System (ADS)

    Kadakia, Karan; Datta, Moni Kanchan; Velikokhatnyi, Oleg I.; Jampani, Prashanth; Park, Sung Kyoo; Chung, Sung Jae; Kumta, Prashant N.

    2014-01-01

    Identification of electro-catalysts containing non-noble metal or significantly reduced amounts of expensive noble metals (e.g. RuO2) is highly desirable. Development of such a catalyst with comparable electrochemical performance to the standard noble metal oxide for proton exchange membrane (PEM) based water electrolysis would constitute a pioneering breakthrough in hydrogen generation by water electrolysis. In line with these goals, by exploiting a two-pronged theoretical first principles and experimental approach herein we demonstrate that a nano-structured solid solution of SnO2:10 wt% F containing only 20 at.% RuO2 [e.g. (Sn0.80Ru0.20)O2:10F] displays a remarkably similar electrochemical activity and moreover, comparable or even much improved electrochemical stability and durability compared to pure the noble metal counterpart, RuO2. Density functional theory calculations have demonstrated direct dependence of the catalytic activity on the electronic structure peculiarities of the F-doped (Ru,Sn)O2 which corresponds well with the experimental results.

  13. Co-Doped MoS₂ Nanosheets with the Dominant CoMoS Phase Coated on Carbon as an Excellent Electrocatalyst for Hydrogen Evolution.

    PubMed

    Dai, Xiaoping; Du, Kangli; Li, Zhanzhao; Liu, Mengzhao; Ma, Yangde; Sun, Hui; Zhang, Xin; Yang, Ying

    2015-12-16

    Highly active and low-cost catalysts for hydrogen evolution reaction (HER) are crucial for the development of efficient water splitting. Molybdenum disulfide (MoS2) nanosheets possess unique physical and chemical properties, which make them promising candidates for HER. Herein, we reported a facile, effective, and scalable strategy by a deposition-precipitation method to fabricate metal-doped (Fe, Co, Ni) molybdenum sulfide with a few layers on carbon black as noble metal-free electrocatalysts for HER. The CoMoS phase after thermal annealing in Co-doped MoS2 plays a crucial role for the enhanced HER. The optimized Co-doped MoS2 catalyst shows superior HER performance with a high exchange current density of 0.03 mA·cm(-2), low onset potential of 90 mV, and small Tafel slope of 50 mV·dec(-1), which also exhibits excellent stability of 10000 cycles with negligible loss of the cathodic current. The superior HER activity originates from the synergistically structural and electronic modulations between MoS2 and Co ions, abundant defects in the active edge sites, as well as the good balance between active sites and electronic conductivity. Thanks to their ease of synthesis, low cost, and high activity, the Co-doped MoS2 catalysts appear to be promising HER catalysts for electrochemical water splitting. PMID:26599427

  14. TiO2 nanotube array photoelectrocatalyst and Ni-Sb-SnO2 electrocatalyst bifacial electrodes: a new type of bifunctional hybrid platform for water treatment.

    PubMed

    Yang, So Young; Choi, Wonyong; Park, Hyunwoong

    2015-01-28

    Bifunctional hybrid electrodes capable of generating various reactive oxygen species (ROS) over a wide range of potentials were developed by coupling electrocatalysts and photoelectrocatalysts. To achieve this, Ni-doped Sb-SnO2 (NSS) was deposited on one side of a titanium (Ti) foil while the other side was anodized to grow a TiO2 nanotube array (TNA) for electrochemical ozone generation and photoelectrochemical hydroxyl radical generation, respectively. Surface characterization indicated that NSS and TNA were formed and spatially separated yet electrically connected through the Ti substrate. While each catalyst possessed unique electrochemical properties, the coupling of both catalysts resulted in mixed electrochemical properties that drove electrocatalysis at high potentials and photoelectrocatalysis at low potentials. The performance of the NSS/TNA electrode for phenol decomposition was ∼3 times greater than that of single-layer catalysts and ∼1.5 times greater than the combined catalytic performances of the individual NSS and TNA catalysts. This synergistic effect was attributed partly to the simultaneous generation of hydroxyl radicals and ozone, followed by the production of other ROS. A mechanism for the generation of ROS was discussed. PMID:25561436

  15. Oxygen Reduction Reaction Measurements on Platinum Electrocatalysts Utilizing Rotating Disk Electrode Technique: I. Impact of Impurities, Measurement Protocols and Applied Corrections

    DOE PAGESBeta

    Shinozaki, Kazuma; Zack, Jason W.; Richards, Ryan M.; Pivovar, Bryan S.; Kocha, Shyam S.

    2015-07-22

    The rotating disk electrode (RDE) technique is being extensively used as a screening tool to estimate the activity of novel PEMFC electrocatalysts synthesized in lab-scale (mg) quantities. Discrepancies in measured activity attributable to glassware and electrolyte impurity levels, as well as conditioning, protocols and corrections are prevalent in the literature. Moreover, the electrochemical response to a broad spectrum of commercially sourced perchloric acid and the effect of acid molarity on impurity levels and solution resistance were also assessed. Our findings reveal that an area specific activity (SA) exceeding 2.0 mA/cm2 (20 mV/s, 25°C, 100 kPa, 0.1 M HClO4) for polishedmore » poly-Pt is an indicator of impurity levels that do not impede the accurate measurement of the ORR activity of Pt based catalysts. After exploring various conditioning protocols to approach maximum utilization of the electrochemical area (ECA) and peak ORR activity without introducing catalyst degradation, an investigation of measurement protocols for ECA and ORR activity was conducted. Down-selected protocols were based on the criteria of reproducibility, duration of experiments, impurity effects and magnitude of pseudo-capacitive background correction. In sum, statistical reproducibility of ORR activity for poly-Pt and Pt supported on high surface area carbon was demonstrated.« less

  16. An efficient electrocatalyst as cathode material for solid oxide fuel cells: BaFe0·95Sn0·05O3-δ

    NASA Astrophysics Data System (ADS)

    Dong, Feifei; Ni, Meng; He, Wei; Chen, Yubo; Yang, Guangming; Chen, Dengjie; Shao, Zongping

    2016-09-01

    The B-site substitution with the minor amount of tin in BaFeO3-δ parent oxide is expected to stabilize a single perovskite lattice structure. In this study, a composition of BaFe0·95Sn0·05O3-δ (BFS) as a new cathode material for intermediate-temperature solid oxide fuel cells (IT-SOFCs) is synthesized and characterized. Special attention is paid to the exploration of some basic properties including phase structure, oxygen non-stoichiometry, electrical conductivity, oxygen bulk diffusion coefficient, and surface exchange coefficient, which are of significant importance to the electrochemical activity of cathode materials. BFS holds a single cubic perovskite structure over temperature range of cell operation, determined by in-situ X-ray diffraction and scanning transmission electron microscope. A high oxygen vacancy concentration at cell operating temperatures is observed by combining thermo-gravimetric data and iodometric titration result. Furthermore, electrical conductivity relaxation measurement illustrates the fast oxygen bulk diffusion and surface exchange kinetics. Accordingly, testing cells based on BFS cathode material demonstrate the low polarization resistance of 0.033 Ω cm2 and high peak power density of 1033 mW cm-2 at 700 °C, as well as a relatively stable long-term operation for ∼300 h. The results obtained suggest that BFS perovskite oxide holds a great promise as an oxygen reduction electrocatalyst for IT-SOFCs.

  17. Pd-Pt alloys nanowires as support-less electrocatalyst with high synergistic enhancement in efficiency for methanol oxidation in acidic medium.

    PubMed

    Rana, Moumita; Patil, Pramod K; Chhetri, Manjeet; Dileep, K; Datta, Ranjan; Gautam, Ujjal K

    2016-02-01

    In a facile approach, Pd73Pt27 alloy nanowires (NWs) with large aspect ratios were synthesized in high yield by using sacrificial templates. Unlike majority of processes, our synthesis was carried out in aqueous solution with no intermittent separating stages for the products, while maintaining the NW morphology up to ∼30% of Pt. Upon evaporation of their dispersion, the NWs transform into a stable porous membrane due to self-entanglement and can be directly lifted and employed for electrocatalytic applications without external catalyst supports. We show that the NW membranes exhibit efficient electrocatalytic performance for methanol oxidation reaction (MOR) with 10 times higher mass activity and 4.4 times higher specific activity in acidic media as compared to commercial Pt catalysts. The membrane electrocatalysts is robust and exhibited very good stability with retention of ∼70% mass-activity after 4000 potential cycles. Since Pd was found to be inert towards MOR in acidic medium, our investigation provides a direct estimate of synergistic enhancement of efficiency. Over 10 times increment of mass activity appears to be significantly higher than previous investigations in various other reaction media. PMID:26520816

  18. Covalent entrapment of cobalt-iron sulfides in N-doped mesoporous carbon: extraordinary bifunctional electrocatalysts for oxygen reduction and evolution reactions.

    PubMed

    Shen, Mengxia; Ruan, Changping; Chen, Yan; Jiang, Chunhuan; Ai, Kelong; Lu, Lehui

    2015-01-21

    To alleviate the kinetic barriers associated with ORR (oxygen reduction reaction) and OER (oxygen evolution reaction) in electrochemical systems, efficient nonprecious electrocatalysts are urgently required. Here we report a facile soft-template mediated approach for fabrication of nanostructured cobalt-iron double sulfides that are covalently entrapped in nitrogen-doped mesoporous graphitic carbon (Co0.5Fe0.5S@N-MC). Notably, with a positive half-wave potential (0.808 V) and a high diffusion-limiting current density, the composite material delivers unprecedentedly striking ORR electrocatalytic activity among recently reported nonprecious late transition metal chalcogenide materials in alkaline medium. Various characterization techniques, including X-ray absorption spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction, are conducted to elucidate the correlation between structural features and catalytic activities of the composite. Moderate substitution and well-dispersion of iron in bimetallic sulfide composites are believed to have positive effect on the adsorption and activation of oxygen-containing species, thus leading to conspicuous ORR and OER catalytic enhancement compared to their monometallic counterparts. Besides, the covalent bridge between active sulfide particles and mesoporous carbon shells provides facile pathways for electron and mass transport. Beneficially, the intimate coupling interaction renders prolonged electrocatalytic performances to the composite. Our results may possibly lend a new impetus to the rational design of bi- or multimetallic sulfides encapsulated in porous carbon with improved performance for electrocatalysis and energy storage applications. PMID:25531776

  19. N-doped carbon@Ni-Al2O3 nanosheet array@graphene oxide composite as an electrocatalyst for hydrogen evolution reaction in alkaline medium

    NASA Astrophysics Data System (ADS)

    Wang, Juan; Qiu, Tian; Chen, Xu; Lu, Yanluo; Yang, Wensheng

    2015-10-01

    An NiAl-layered double-hydroxide (NiAl-LDH) nanosheet array is grown on a graphene oxide (GO) substrate (NiAl-LDH@GO) by the hydrothermal method. The NiAl-LDH@GO is used as the precursor to synthetize an N-doped carbon@Ni-Al2O3 nanosheet array@GO composite (N-C@Ni-Al2O3@GO) by coating with dopamine followed by calcination. The N-C@Ni-Al2O3@GO is used as a non-noble metal electrocatalyst for hydrogen evolution reaction in alkaline medium, and exhibits high electrocatalytic activity with low onset overpotential (-75 mV). The improved electrocatalytic performance of N-C@Ni-Al2O3@GO arises from its intrinsic features. First, it has a high specific surface area with the Ni nanoparticles in the composite dispersed well and the sizes of Ni nanoparticles are small, which lead to the exposure of more active sites for electrocatalysis. Second, there is a synergistic effect between the Ni nanoparticles and the N-C coating layer, which is beneficial to reduce the activation energy of the Volmer step and improve the electrocatalytic activity. Third, the N-C coating layer and the XC-72 additive can form an electrically conductive network, which serves as a bridge for the transfer of electrons from the electrode to the Ni nanoparticles.

  20. Fe/N/C hollow nanospheres by Fe(iii)-dopamine complexation-assisted one-pot doping as nonprecious-metal electrocatalysts for oxygen reduction.

    PubMed

    Zhou, Dan; Yang, Liping; Yu, Linghui; Kong, Junhua; Yao, Xiayin; Liu, Wanshuang; Xu, Zhichuan; Lu, Xuehong

    2015-01-28

    In this work, a series of hollow carbon nanospheres simultaneously doped with N and Fe-containing species are prepared by Fe(3+)-mediated polymerization of dopamine on SiO2 nanospheres, carbonization and subsequent KOH etching of the SiO2 template. The electrochemical properties of the hollow nanospheres as nonprecious-metal electrocatalysts for oxygen reduction reaction (ORR) are characterized. The results show that the hollow nanospheres with mesoporous N-doped carbon shells of ∼10 nm thickness and well-dispersed Fe3O4 nanoparticles prepared by annealing at 750 °C (Fe/N/C HNSs-750) exhibit remarkable ORR catalytic activity comparable to that of a commercial 20 wt% Pt/C catalyst, and high selectivity towards 4-electron reduction of O2 to H2O. Moreover, it displays better electrochemical durability and tolerance to methanol crossover effect in an alkaline medium than the Pt/C. The excellent catalytic performance of Fe/N/C HNSs-750 towards ORR can be ascribed to their high specific surface area, mesoporous morphology, homogeneous distribution of abundant active sites, high pyridinic nitrogen content, graphitic nitrogen and graphitic carbon, as well as the synergistic effect of nitrogen and iron species for catalyzing ORR. PMID:25500995