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Sample records for reduction reaction orr

  1. Nanostructured MnxOy for oxygen reduction reaction (ORR) catalysts

    NASA Astrophysics Data System (ADS)

    Delmondo, Luisa; Salvador, Gian Paolo; Muñoz-Tabares, José Alejandro; Sacco, Adriano; Garino, Nadia; Castellino, Micaela; Gerosa, Matteo; Massaglia, Giulia; Chiodoni, Angelica; Quaglio, Marzia

    2016-12-01

    In the field of fuel cells, oxygen plays a key role as the final electron acceptor. To facilitate its reduction (Oxygen Reduction Reaction-ORR), a proper catalyst is needed and platinum is considered the best one due to its low overpotential for this reaction. By considering the high price of platinum, alternative catalysts are needed and manganese oxides (MnxOy) can be considered promising substitutes. They are inexpensive, environmental friendly and can be obtained into several forms; most of them show significant electro-catalytic performance, even if strategies are needed to increase their efficiency. In particular, by developing light and high-surface area materials and by optimizing the presence of catalytic sites, we can obtain a cathode with improved electro-catalytic performance. In this case, nanofibers and xerogels are two of the most promising nanostructures that can be used in the field of catalysis. In this work, a study of the morphological and catalytic behavior of MnxOy nanofibers and xerogels is proposed. Nanofibers were obtained by electrospinning, while xerogels were prepared by sol-gel and freeze drying techniques. Despite of the different preparation approaches, the obtained nanostructured manganese oxides exhibited similar catalytic performance for the ORR, comparable to those obtained from Pt catalysts.

  2. Oxygen reduction reaction (ORR) on mixed oxy-nitride non-noble catalyst: Ab-initio simulation, elaboration and characterization

    NASA Astrophysics Data System (ADS)

    Seifitokaldani, Ali

    In this project, titanium oxy-nitride (TiOxN y) has been studied as a new non-noble electrocatalyst for the oxygen reduction reaction (ORR). A comprehensive comparison between four different sol-gel methods was carried out to evaluate the physicochemical and electrochemical properties of the produced electro-catalysts. Among them, a new urea-based sol-gel method (simply called U method) is introduced to prepare TiOxNy at a fairly low temperature and duration, with higher electro-catalytic activity for the ORR. The prepared electro-catalysts with different N/O ratios showed different properties from a less conductive behavior in oxygen-rich (low N/O ratio) materials to more conductive electro-catalyst behavior in nitrogen-rich (high N/O ratio) oxy-nitrides, respectively. Generally, electro-catalysts prepared by the U method had more titanium nitride in their structures than the electro-catalysts prepared by the other methods. Nevertheless, heat treatment had a key role in this phase transferring from having high oxide structure to high nitride structure. According to the elemental analysis done by energy dispersive spectroscopy (EDS), nitrogen percentage in the bulk material increased from 9 to 24 percent by increasing the temperature from 700 to 1100 °C, while the oxygen percentage was decreasing inversely. In addition, based on the X-ray diffraction (XRD) data, in the case of U method, the TiN characteristic peaks were obvious, even at lower temperatures. Increasing the temperature also made the peaks much sharper indicating the growth of the crystallite size. The calculated crystallite size showed the crystallite size of samples prepared by U method (20 to 40 nm) was almost in the same range of the TiN crystallite size, but the crystallite size of the samples prepared by the other sol-gel methods (40 to 60 nm) was in the same range of the TiO2 crystallite size. Scanning electron microscopy (SEM) and B.E.T. surface area analyzer were used to evaluate the particle

  3. The role of surface oxygenated-species and adsorbed hydrogen in the oxygen reduction reaction (ORR) mechanism and product selectivity on Pd-based catalysts in acid media.

    PubMed

    Rahul, R; Singh, R K; Bera, B; Devivaraprasad, R; Neergat, M

    2015-06-21

    Oxygen reduction reaction (ORR) is investigated on bulk PdO-based catalysts (oxides of Pd and Pd3Co) in oxygen-saturated 0.1 M HClO4 to establish the role of surface oxides and adsorbed hydrogen in the activity and product selectivity (H2O/H2O2). The initial voltammetric features suggest that the oxides are inactive toward ORR. The evolution of the ORR voltammograms and potential-dependent H2O2 generation features on the PdO catalyst suggest gradual and parallel in situ reduction of the bulk PdO phase below ∼0.4 V in the hydrogen underpotential deposition (Hupd) region; the reduction of the bulk PdO catalyst is confirmed from the X-ray photoelectron spectra (XPS) and X-ray diffraction (XRD) patterns. The potential-dependent H2O2 generation features originate due to the presence of surface oxides and adsorbed hydrogen; this is further confirmed using halide ions (Cl(-) and Br(-)) and peroxide as the external impurities.

  4. Graphene Oxide Sheathed ZIF-8 Microcrystals: Engineered Precursors of Nitrogen-Doped Porous Carbon for Efficient Oxygen Reduction Reaction (ORR) Electrocatalysis.

    PubMed

    Thomas, Minju; Illathvalappil, Rajith; Kurungot, Sreekumar; Nair, Balagopal N; Mohamed, Abdul Azeez Peer; Anilkumar, Gopinathan M; Yamaguchi, Takeo; Hareesh, U S

    2016-11-02

    Nitrogen containing mesoporous carbon obtained by the pyrolysis of graphene oxide (GO) wrapped ZIF-8 (Zeolitic Imidazolate Frameworks-8) micro crystals is demonstrated to be an efficient catalyst for the oxygen reduction reaction (ORR). ZIF-8 synthesis in the presence of GO sheets helped to realize layers of graphene oxide over ZIF-8 microcrystals and the sphere-like structures thus obtained, on heat treatment, transformed to highly porous carbon with a nitrogen content of about 6.12% and surface area of 502 m(2)/g. These catalysts with a typical micromeso porous architecture exhibited an onset potential of 0.88Vvs RHE in a four electron pathway and also demonstrated superior durability in alkaline medium compared to that of the commercial Pt/C catalyst. The N-doped porous carbon derived from GO sheathed ZIF-8 core-shell structures could therefore be employed as an efficient electrocatalyst for fuel cell applications.

  5. Stability issues in Pd-based catalysts: the role of surface Pt in improving the stability and oxygen reduction reaction (ORR) activity.

    PubMed

    Singh, R K; Rahul, R; Neergat, M

    2013-08-21

    Carbon-supported Pd and Pd3Co catalysts have been electrochemically characterized in 0.1 M HClO4 solution and we found that both catalysts were unstable. On repeated potential cycling, the electrochemical surface area of the catalysts decreases and the oxygen reduction reaction (ORR) activity suffers. To stabilize surface Pd atoms of both Pd and Pd3Co catalysts, we deposited Pt using adsorbed hydrogen on the catalytically active Pd sites. The Pt : Pd ratio of Pt-coated Pd and Pt-coated Pd3Co catalysts suggests half-a-monolayer coverage of Pt (two hydrogen atoms required for reducing a Pt(2+) ion). The Pt : Pd ratio of Pt-coated Pd3Co catalyst obtained from the simple geometrical hard sphere model, energy-dispersive X-ray spectroscopy (EDS) line scan and bulk EDS agrees very well with that calculated from the hydrogen desorption (H(des)) charge of Pd3Co. At the same time, the Pt : Pd ratio of Pt-coated Pd calculated from the H(des) charge of Pd catalyst is significantly lower than the ratio obtained from the other methods. Thus, the Pt : Pd ratio of the Pt-coated Pd catalyst estimated from the H(des) region of Pd is an underestimation of the composition. This suggests that Pd forms an electrochemically inactive species from the H(upd) region itself and Co in Pd3Co seems to stabilize Pd against oxidation by delaying the formation of electrochemically inactive species to higher potentials above the H(upd) region. The voltammograms along with the peroxide formation characteristics of the catalysts support the above observations. The deposited Pt on the surface of the Pd and Pd3Co catalysts masks active Pd sites from the electrochemical environment and even partial coverage with Pt improves the stability and ORR activity of the catalysts when compared to that of the respective Pt-free counterparts.

  6. Use of H2S to Probe the Active Sites in FeNC Catalysts for the Oxygen Reduction Reaction (ORR) in Acidic Media

    SciTech Connect

    Singh, Deepika; Mamtani, Kuldeep; Bruening, Christopher R.; Miller, Jeffrey T.; Ozkan, Umit S.

    2014-10-01

    H2S has been used as a probe molecule both in an “in situ” poisoning experiment and in intermediate-temperature heat-treatment steps during and after the preparation of FeNC catalysts in an attempt to analyze its effect on their ORR activity. The heat treatments were employed either on the ball-milled precursor of FeNC or after the Ar-NH3 high temperature heat treatments. ORR activity of the H2S-treated catalysts was seen to be significantly lower than the sulfur-free catalysts, whether the sulfur exposure was during a half-cell testing, or as an intermediate-temperature exposure to H2S. The incorporation of sulfur species and interaction of Fe with sulfur were confirmed by characterization using XPS, EXAFS, TPO, and TPD. This study provides crucial evidence regarding differences in active sites in FeNC versus nitrogen-containing carbon nanostructured (CNx) catalysts.

  7. Cobaltite oxide nanosheets anchored graphene nanocomposite as an efficient oxygen reduction reaction (ORR) catalyst for the application of lithium-air batteries

    NASA Astrophysics Data System (ADS)

    Gnana kumar, G.; Christy, Maria; Jang, Hosaeng; Nahm, Kee Suk

    2015-08-01

    The graphene/cubic cobaltite oxide nanosheets (rGO/Co3O4) with a face centered cubic crystalline structure are synthesized and are exploited as effective cathode catalysts in high performance Lithium-air batteries. The morphological images enunciate that 220 nm average diameter of Co3O4 nanosheets are effectively anchored over the graphene sheets and the diameter of individual nanoparticles that construct the cubic nanosheets is 5 nm. The growth and composite formation mechanisms of prepared nanostructures are identified from Raman and FT-IR spectroscopic techniques. rGO/Co3O4 composite exhibits a lower voltage, high discharge capacity of 4150 mAh g-1 and displays superior cyclability without any capacity losses, signifying the excellent rechargeability of the fabricated electrodes. The post mortem analysis of electrodes specify the existence of lithium peroxide (Li2O2), lithium oxide (Li2O) and lithium carbonate (Li2CO3) discharge products, revealing the involved electrochemical reaction of Lithium-air batteries. The excellent electrochemical properties of rGO/Co3O4 composite is due to the combination of rapid electrokinetics of electron transport and high electrocatalytic activity toward oxygen reduction reaction given via the synergetic effects of rGO and cubic Co3O4 nanosheets. These findings provide fundamental knowledge on understanding the influence of morphological and structural properties of graphene based nanostructures toward Lithium-air battery performances.

  8. Nanoparticles of Ag with a Pt and Pd rich surface supported on carbon as a new catalyst for the oxygen electroreduction reaction (ORR) in acid electrolytes: Part 1

    NASA Astrophysics Data System (ADS)

    Pech-Pech, I. E.; Gervasio, Dominic F.; Godínez-Garcia, A.; Solorza-Feria, O.; Pérez-Robles, J. F.

    2015-02-01

    Silver (Ag) nanoparticles enriched with platinum (Pt) and palladium (Pd) on their surfaces (Ag@Pt0.1Pd0.1) are supported on Vulcan XC-72 carbon (C) to form a new catalyst (Ag@Pt0.1Pd0.1/C) for the oxygen reduction reaction (ORR) in acid electrolytes. This catalyst is prepared in one pot by reducing Ag and then Pt and Pd metal salts with sodium borohydride in the presence of trisodium citrate then adding XC-72 while applying intense ultrasound. The metallic Ag@Pt0.1Pd0.1 nanoparticles contain 2 weight percent of Pt, are spherical and have an average size less than 10 nm as determined by X-ray diffraction (XRD) and transmission electron microscopy (TEM). At the ORR potentials, Ag nanoparticles on carbon (Ag/C) rapidly lose Ag by dissolution and show no more catalytic activity for the ORR than the carbon support, whereas Ag@Pt0.1Pd0.1/C is a stable catalyst and exhibits 1.4 and 1.6 fold greater specific activity, also 3.6 and 2.8 fold greater mass activity for ORR in 0.5 M H2SO4 solution than comparable Pt/C and Pt0.5Pd0.5/C catalysts with the same Pt loading as determined for thin-films of these catalysts on a rotating-disk electrode (TF-RDE). Using silver nanoparticles increases Pt utilization and therefore decreases Pt-loading and cost of a catalyst for a proton exchange membrane fuel cell (PEMFC) electrode.

  9. Free Electrons to Molecular Bonds and Back: Closing the Energetic Oxygen Reduction (ORR)-Oxygen Evolution (OER) Cycle Using Core-Shell Nanoelectrocatalysts.

    PubMed

    Strasser, Peter

    2016-11-15

    Nanomaterial science and electrocatalytic science have entered a successful "nanoelectrochemical" symbiosis, in which novel nanomaterials offer new frontiers for studies on electrocatalytic charge transfer, while electrocatalytic processes give meaning and often practical importance to novel nanomaterial concepts. Examples of this fruitful symbiosis are dealloyed core-shell nanoparticle electrocatalysts, which often exhibit enhanced kinetic charge transfer rates at greatly improved atom-efficiency. As such, they represent ideal electrocatalyst architectures for the acidic oxygen reduction reaction to water (ORR) and the acidic oxygen evolution reaction from water (OER) that require scarce Pt- and Ir-based catalysts. Together, these two reactions constitute the "O-cycle", a key elemental process loop in the field of electrochemical energy interconversion between electricity (free electrons) and molecular bonds (H2O/O2), realized in the combination of water electrolyzers and hydrogen/oxygen fuel cells. In this Account, we describe our recent efforts to design, synthesize, understand, and test noble metal-poor dealloyed Pt and Ir core-shell nanoparticles for deployment in acidic polymer electrolyte membrane (PEM) electrolyzers and PEM fuel cells. Spherical dealloyed Pt core-shell particles, derived from PtNi3 precursor alloys, showed favorable ORR activity. More detailed size-activity correlation studies further revealed that the 6-8 nm diameter range is a most desirable initial particle size range in order to maximize the particle Ni content after ORR testing and to preserve performance stability. Similarly, dealloyed and oxidized IrOx core-shell particles derived from Ni-rich Ir-Ni precursor particles proved highly efficient oxygen evolution reaction (OER) catalysts in acidic conditions. In addition to the noble metal savings in the particle cores, the Pt core-shell particles are believed to benefit in terms of their mass-based electrochemical kinetics from surface

  10. Tuning nanoparticle catalysis for the oxygen reduction reaction.

    PubMed

    Guo, Shaojun; Zhang, Sen; Sun, Shouheng

    2013-08-12

    Advances in chemical syntheses have led to the formation of various kinds of nanoparticles (NPs) with more rational control of size, shape, composition, structure and catalysis. This review highlights recent efforts in the development of Pt and non-Pt based NPs into advanced nanocatalysts for efficient oxygen reduction reaction (ORR) under fuel-cell reaction conditions. It first outlines the shape controlled synthesis of Pt NPs and their shape-dependent ORR. Then it summarizes the studies of alloy and core-shell NPs with controlled electronic (alloying) and strain (geometric) effects for tuning ORR catalysis. It further provides a brief overview of ORR catalytic enhancement with Pt-based NPs supported on graphene and coated with an ionic liquid. The review finally introduces some non-Pt NPs as a new generation of catalysts for ORR. The reported new syntheses with NP parameter-tuning capability should pave the way for future development of highly efficient catalysts for applications in fuel cells, metal-air batteries, and even in other important chemical reactions.

  11. Beneficial compressive strain for oxygen reduction reaction on Pt (111) surface

    SciTech Connect

    Kattel, Shyam; Wang, Guofeng

    2014-09-28

    We investigated the influence of compressive surface strain on the progression of oxygen reduction reaction (ORR) on Pt(111) surface using the density functional theory (DFT) calculation method. Specifically, we calculated the binding energies of all the chemical species possibly involved in ORR and the reaction energies (heat of reaction and activation energy) of all the possible ORR elementary reactions on the Pt(111) surfaces with −2% and −3% strain. Our DFT results indicate that all the ORR species bind more weakly on the compressively strained surfaces than on an unstrained surface owing to strain-induced d-electron band broadening. Our DFT calculations further predict that both OOH dissociation and HOOH dissociation pathways could be active for ORR on the Pt(111) surface with compressive strain between −2% and −3%. Moreover, the activation energies of the ORR rate-determining steps on the compressively strained Pt(111) surfaces were found to be lower than that on the unstrained Pt(111) surface. It was thus inferred that a −2% to −3% surface strain could lead to enhanced ORR activity on the Pt(111) catalysts. Consequently, our study suggests that tuning surface strain is an effective way to improve the performance of Pt-based electrocatalysts for ORR.

  12. Covalent grafting of carbon nanotubes with a biomimetic heme model compound to enhance oxygen reduction reactions.

    PubMed

    Wei, Ping-Jie; Yu, Guo-Qiang; Naruta, Yoshinori; Liu, Jin-Gang

    2014-06-23

    The oxygen reduction reaction (ORR) is one of the most important reactions in both life processes and energy conversion systems. The replacement of noble-metal Pt-based ORR electrocatalysts by nonprecious-metal catalysts is crucial for the large-scale commercialization of automotive fuel cells. Inspired by the mechanisms of dioxygen activation by metalloenzymes, herein we report a structurally well-defined, bio-inspired ORR catalyst that consists of a biomimetic model compound-an axial imidazole-coordinated porphyrin-covalently attached to multiwalled carbon nanotubes. Without pyrolysis, this bio-inspired electrocatalyst demonstrates superior ORR activity and stability compared to those of the state-of-the-art Pt/C catalyst in both acidic and alkaline solutions, thus making it a promising alternative as an ORR electrocatalyst for application in fuel-cell technology.

  13. Amorphous carbon enriched with pyridinic nitrogen as an efficient metal-free electrocatalyst for oxygen reduction reaction.

    PubMed

    Chen, Jingyan; Wang, Xin; Cui, Xiaoqiang; Yang, Guangmin; Zheng, Weitao

    2014-01-18

    An amorphous metal-free N-doped carbon film prepared by sputtering and annealing exhibits comparable electrocatalytic activity and superior stability and methanol tolerance to the commercial Pt/C catalyst via a four-electron pathway for oxygen reduction reaction (ORR). Pyridinic nitrogen in films plays a key role in electrocatalytic activity for ORR.

  14. Theoretical investigations of the oxygen reduction reaction on Pt(111).

    PubMed

    Keith, John A; Jerkiewicz, Gregory; Jacob, Timo

    2010-09-10

    Computational modeling can provide important insights into chemical reactions in both applied and fundamental fields of research. One of the most critical processes needed in practical renewable energy sources is the oxygen reduction reaction (ORR). Besides being the key process in combustion and corrosion, the ORR has an elusive mechanism that may proceed in a number of complicated reaction steps in electrochemical fuel cells. Indeed, the mechanism of the ORR on highly studied Pt(111) electrodes has been the subject of interest and debate for decades. Herein, we first outline the theory behind these types of simulations and then show how to use these quantum mechanical approaches and approximations to create a realistic model. After reviewing the performance of these methods in studying the binding of molecular oxygen to Pt(111), we then outline our own results in elucidating the ORR and its dependence on environmental parameters, such as solvent, thermodynamic energies, and the presence of an external electrode potential. This approach can, in principle, be applied to other equally complicated investigations of other surfaces or electrochemical reactions.

  15. Novel nanowire-structured polypyrrole-cobalt composite as efficient catalyst for oxygen reduction reaction

    PubMed Central

    Yuan, Xianxia; Li, Lin; Ma, Zhong; Yu, Xuebin; Wen, Xiufang; Ma, Zi-Feng; Zhang, Lei; Wilkinson, David P.; Zhang, Jiujun

    2016-01-01

    A novel nanowire-structured polypyrrole-cobalt composite, PPy-CTAB-Co, is successfully synthesized with a surfactant of cetyltrimethylammounium bromide (CTAB). As an electro-catalyst towards oxygen reduction reaction (ORR) in alkaline media, this PPy-CTAB-Co demonstrates a superior ORR performance when compared to that of granular PPy-Co catalyst and also a much better durability than the commercial 20 wt% Pt/C catalyst. Physiochemical characterization indicates that the enhanced ORR performance of the nanowire PPy-CTAB-Co can be attributed to the high quantity of Co-pyridinic-N groups as ORR active sites and its large specific surface area which allows to expose more active sites for facilitating oxygen reduction reaction. It is expected this PPy-CTAB-Co would be a good candidate for alkaline fuel cell cathode catalyst. PMID:26860889

  16. Nanoparticles of Ag with a Pt and Pd rich surface supported on carbon as a new catalyst for the oxygen electroreduction reaction (ORR) in acid electrolytes: Part 2

    NASA Astrophysics Data System (ADS)

    Pech-Pech, I. E.; Gervasio, Dominic F.; Pérez-Robles, J. F.

    2015-02-01

    In the first part of this work, the feasibility of developing a catalyst with high activity for the oxygen electroreduction reaction (ORR) in acid media and with low Pt loading was demonstrated by over coating a silver (Ag) nanoparticle with a shell of platinum (Pt) and palladium (Pd) [7]. The results show that best activity is not directly related to a higher PtPd loading on the surface of the Ag. The best catalyst in a series of this type of catalyst is found with Ag@Pt0.3Pd0.3/C which gives a specific activity for oxygen reduction, jk (in units of mA cm-2 of real area), of 0.07 mA cm-2 at 0.85 V vs. NHE, as compared to 0.04 mA cm-2 when with a commercial Pt on carbon catalyst (Pt20/C) is used in an identical electrode except for the catalyst. The mass activity, jm (in units of mA μg-1 of Pt), for Ag@Pt0.3Pd0.3/C is 0.04 mA μg-1 of Pt at 0.85 V vs. NHE, whereas that for the Pt20/C gives 0.02 mA μg-1 of Pt, showing Ag@Pt0.3Pd0.3/C is a lower-cost catalyst, because using a Ag core and Pd with Pt in the shell gives the highest catalytic activity using less Pt.

  17. Homogenous electrocatalytic oxygen reduction rates correlate with reaction overpotential in acidic organic solutions

    DOE PAGES

    Pegis, Michael L.; McKeown, Bradley A.; Kumar, Neeraj; ...

    2016-10-28

    Improvement of electrocatalysts for the oxygen reduction reaction (ORR) is critical for the advancement of fuel cell technologies. Herein, we report a series of eleven soluble iron porphyrin ORR electrocatalysts that possess turnover frequencies (TOFs) from 3 s-1 to an unprecedented 2.2 x 106 s-1. These TOFs correlate with the ORR overpotential, which can be changed by modulating the ancillary ligand, by varying the reaction conditions or by changing the catalyst’s protonation state. This is the first such correlation for homogeneous ORR electrocatalysis, and it demonstrates that the remarkably fast TOFs are a consequence of the high overpotential. Computational studiesmore » indicate that the correlation is analogous to the volcano plot analysis developed for heterogeneous ORR materials. This unique parallel between homo- and heterogeneous ORR electrocatalysts allows a fundamental understanding of intrinsic barriers associated with the ORR, which can aid the design of new catalytic systems that operate at low overpotential. 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 (DOE), Office of Science, Office of Basic Energy Sciences. Additional data is given in the Electronic Supporting Information.« less

  18. Homogenous Electrocatalytic Oxygen Reduction Rates Correlate with Reaction Overpotential in Acidic Organic Solutions

    SciTech Connect

    Pegis, Michael L.; McKeown, Bradley A.; Kumar, Neeraj; Lang, Kai; Wasylenko, Derek J.; Zhang, X. Peter; Raugei, Simone; Mayer, James M.

    2016-10-28

    Improvement of electrocatalysts for the oxygen reduction reaction (ORR) is critical for the advancement of fuel cell technologies. Herein, we report a series of eleven soluble iron porphyrin ORR electrocatalysts that possess turnover frequencies (TOFs) from 3 s-1 to an unprecedented 2.2 x 106 s-1. These TOFs correlate with the ORR overpotential, which can be changed by modulating the ancillary ligand, by varying the reaction conditions or by changing the catalyst’s protonation state. This is the first such correlation for homogeneous ORR electrocatalysis, and it demonstrates that the remarkably fast TOFs are a consequence of the high overpotential. Computational studies indicate that the correlation is analogous to the volcano plot analysis developed for heterogeneous ORR materials. This unique parallel between homo- and heterogeneous ORR electrocatalysts allows a fundamental understanding of intrinsic barriers associated with the ORR, which can aid the design of new catalytic systems that operate at low overpotential. 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 (DOE), Office of Science, Office of Basic Energy Sciences. Additional data is given in the Electronic Supporting Information.

  19. First principles based mean field model for oxygen reduction reaction.

    PubMed

    Jinnouchi, Ryosuke; Kodama, Kensaku; Hatanaka, Tatsuya; Morimoto, Yu

    2011-12-21

    A first principles-based mean field model was developed for the oxygen reduction reaction (ORR) taking account of the coverage- and material-dependent reversible potentials of the elementary steps. This model was applied to the simulation of single crystal surfaces of Pt, Pt alloy and Pt core-shell catalysts under Ar and O(2) atmospheres. The results are consistent with those shown by past experimental and theoretical studies on surface coverages under Ar atmosphere, the shape of the current-voltage curve for the ORR on Pt(111) and the material-dependence of the ORR activity. This model suggests that the oxygen associative pathway including HO(2)(ads) formation is the main pathway on Pt(111), and that the rate determining step (RDS) is the removal step of O(ads) on Pt(111). This RDS is accelerated on several highly active Pt alloys and core-shell surfaces, and this acceleration decreases the reaction intermediate O(ads). The increase in the partial pressure of O(2)(g) increases the surface coverage with O(ads) and OH(ads), and this coverage increase reduces the apparent reaction order with respect to the partial pressure to less than unity. This model shows details on how the reaction pathway, RDS, surface coverages, Tafel slope, reaction order and material-dependent activity are interrelated.

  20. A comparative DFT study of oxygen reduction reaction on mononuclear and binuclear cobalt and iron phthalocyanines

    NASA Astrophysics Data System (ADS)

    Chen, Xin; Li, Mengke; Yu, Zongxue; Ke, Qiang

    2016-12-01

    The oxygen reduction reaction (ORR) catalyzed by mononuclear and planar binuclear cobalt (CoPc) and iron phthalocyanine (FePc) catalysts is investigated in detail by density functional theory (DFT) methods. The calculation results indicate that the ORR activity of Fe-based Pcs is much higher than that of Co-based Pcs, which is due to the fact that the former could catalyze 4e- ORRs, while the latter could catalyze only 2e- ORRs from O2 to H2O2. The original high activities of Fe-based Pcs could be attributed to their high energy level of the highest occupied molecular orbital (HOMO), which could lead to the stronger adsorption energy between catalysts and ORR species. Nevertheless, the HOMO of Co-based Pcs is the ring orbital, not the 3 d Co orbital, thereby inhibiting the electron transfer from metal to adsorbates. Furthermore, compared with mononuclear FePc, the planar binuclear FePc has more stable structure in acidic medium and more suitable adsorption energy of ORR species, making it a promising non-precious electrocatalyst for ORR.

  1. Enhanced stability and activity with Pd-O junction formation and electronic structure modification of palladium nanoparticles supported on exfoliated montmorillonite for the oxygen reduction reaction.

    PubMed

    Ding, W; Xia, M-R; Wei, Z-D; Chen, S-G; Hu, J-S; Wan, L-J; Qi, X-Q; Hu, X-H; Li, L

    2014-06-25

    Palladium has been the focus of recent research on alternative Pt catalysts for the oxygen reduction reaction (ORR). We show that the activity and stability of Pd toward the ORR can be enhanced by Pd-O-oxide covalent bonding when Pd is supported on exfoliated montmorillonite (ex-MMT) nanoplatelets.

  2. Layered SiC Sheets: A Potential Catalyst for Oxygen Reduction Reaction

    PubMed Central

    Zhang, P.; Xiao, B. B.; Hou, X. L.; Zhu, Y. F.; Jiang, Q.

    2014-01-01

    The large-scale practical application of fuel cells cannot come true if the high-priced Pt-based electrocatalysts for oxygen reduction reaction (ORR) cannot be replaced by other efficient, low-cost, and stable electrodes. Here, based on density functional theory (DFT), we exploited the potentials of layered SiC sheets as a novel catalyst for ORR. From our DFT results, it can be predicted that layered SiC sheets exhibit excellent ORR catalytic activity without CO poisoning, while the CO poisoning is the major drawback in conventional Pt-based catalysts. Furthermore, the layered SiC sheets in alkaline media has better catalytic activity than Pt(111) surface and have potential as a metal-free catalyst for ORR in fuel cells. PMID:24448069

  3. Layered SiC sheets: a potential catalyst for oxygen reduction reaction.

    PubMed

    Zhang, P; Xiao, B B; Hou, X L; Zhu, Y F; Jiang, Q

    2014-01-22

    The large-scale practical application of fuel cells cannot come true if the high-priced Pt-based electrocatalysts for oxygen reduction reaction (ORR) cannot be replaced by other efficient, low-cost, and stable electrodes. Here, based on density functional theory (DFT), we exploited the potentials of layered SiC sheets as a novel catalyst for ORR. From our DFT results, it can be predicted that layered SiC sheets exhibit excellent ORR catalytic activity without CO poisoning, while the CO poisoning is the major drawback in conventional Pt-based catalysts. Furthermore, the layered SiC sheets in alkaline media has better catalytic activity than Pt(111) surface and have potential as a metal-free catalyst for ORR in fuel cells.

  4. Heteroatom-Doped Carbon Nanotube and Graphene-Based Electrocatalysts for Oxygen Reduction Reaction.

    PubMed

    Li, Jin-Cheng; Hou, Peng-Xiang; Liu, Chang

    2017-09-29

    Oxygen reduction reaction (ORR) is a key step that determines the performance of a variety of energy storage and conversion devices, such as fuel cells and metal-air batteries. Heteroatom-doped carbon nanotubes (CNTs) and graphenes have attracted increasing interest and hold great promise as efficient ORR catalysts to replace noble-metal-based catalysts, owing to their unique structure characteristics, excellent physicochemical properties, low cost, and rich resources. In this review, recent progress on the design, fabrication, and performance of heteroatom-doped CNT- and graphene-based catalysts is summarized, aiming to provide insights into the working mechanism of these heteroatom-doped nanocarbons in ORR. The advantages, challenges that remain, and possible solutions of these nanocarbon-based electrocatalysts are discussed. Finally, future developing trends of the CNT- and graphene-based ORR catalysts are proposed. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Combinatorial density functional theory-based screening of surface alloys for the oxygen reduction reaction.

    SciTech Connect

    Greeley, J.; Norskov, J.; Center for Nanoscale Materials; Technical Univ. of Denmark

    2009-03-26

    A density functional theory (DFT) -based, combinatorial search for improved oxygen reduction reaction (ORR) catalysts is presented. A descriptor-based approach to estimate the ORR activity of binary surface alloys, wherein alloying occurs only in the surface layer, is described, and rigorous, potential-dependent computational tests of the stability of these alloys in aqueous, acidic environments are presented. These activity and stability criteria are applied to a database of DFT calculations on nearly 750 binary transition metal surface alloys; of these, many are predicted to be active for the ORR but, with few exceptions, they are found to be thermodynamically unstable in the acidic environments typical of low-temperature fuel cells. The results suggest that, absent other thermodynamic or kinetic mechanisms to stabilize the alloys, surface alloys are unlikely to serve as useful ORR catalysts over extended periods of operation.

  6. Evolution of N-Coordinated Iron–Carbon (FeNC) Catalysts and Their Oxygen Reduction (ORR) Performance in Acidic Media at Various Stages of Catalyst Synthesis: An Attempt at Benchmarking

    SciTech Connect

    Mamtani, Kuldeep; Singh, Deepika; Tian, Juan; Millet, Jean-Marc M.; Miller, Jeffrey T.; Co, Anne C.; Ozkan, Umit S.

    2016-11-08

    The objective of this study was to understand the role of iron and the heat treatment steps involved in nitrogen-coordinated iron-carbon (FeNC) catalyst synthesis. We have studied the oxygen reduction reaction (ORR) performance of these catalysts as they evolve from their most crude and inactive form to their most active form. Electrochemical half-cell and fuel cell tests suggest that the presence of Fe was crucial in these samples. The high-temperature heat treatment (once in argon and then in ammonia) at temperatures ≥950 °C were also critical in imparting these catalysts with their highest activity; however, significant loss of activity was observed with cycling and potential hold at 0.5 V for 100 h. In addition, acid-washing after the first or the second pyrolysis steps produced a marked decrease in ORR activity relative to their unwashed counterparts. We also report findings from our efforts towards benchmarking FeNC catalysts for oxygen reduction reaction electrocatalysis. Specifically, we focus on correlating the specific kinetic current (iK) at 0.75 V to electrochemically accessible surface area (EASA) and roughness factor (RF) determined from electrochemical double layer capacitance measurements. 57Fe Mössbauer spectroscopy was employed to shed light into the nature of active sites in FeNC catalysts and provide insights into their deactivation behavior caused by acid-washing. The results suggest planar FeN4 doublet (Fe2+, low spin) as an active site in these materials, which may be leached away in acid, explaining their decreased activity after acid washing. Results for characterization experiments using X-ray photoelectron spectroscopy, temperature programmed oxidation and X-ray absorption spectroscopy, superconducting quantum interference device magnetometry are also presented.

  7. From melamine sponge towards 3D sulfur-doping carbon nitride as metal-free electrocatalysts for oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Xu, Jingjing; Li, Bin; Li, Songmei; Liu, Jianhua

    2017-07-01

    Development of new and efficient metal-free electrocatalysts for replacing Pt to improve the sluggish kinetics of oxygen reduction reaction (ORR) is of great importance to emerging renewable energy technologies such as metal-air batteries and polymer electrolyte fuel cells. Herein, 3D sulfur-doping carbon nitride (S-CN) as a novel metal-free ORR electrocatalyst was synthesized by exploiting commercial melamine sponge as raw material. The sulfur atoms were doping on CN networks uniformly through numerous S-C bonds which can provide additional active sites. And it was found that the S-CN exhibited high catalytic activity for ORR in term of more positive onset potential, higher electron transfer number and higher cathodic density. This work provides a novel choice of metal-free ORR electrocatalysts and highlights the importance of sulfur-doping CN in metal-free ORR electrocatalysts.

  8. Sonochemical preparation of stable porous MnO2 and its application as an efficient electrocatalyst for oxygen reduction reaction.

    PubMed

    Zuo, Ling-Xia; Jiang, Li-Ping; Abdel-Halim, E S; Zhu, Jun-Jie

    2017-03-01

    Porous MnO2 as a non-noble metal oxygen reduction reaction (ORR) electrocatalyst was prepared by a simple sonochemical route. The as-prepared porous MnO2 exhibited higher electrocatalytic activity, superior stability and better methanol tolerance than commercial Pt/C catalyst in alkaline media. Furthermore, the ORR proceeded via a nearly four-electron pathway. Cyclic voltammetry (CV) and rotating-disk electrode (RDE) measurements verified that the ORR enhancement was attributed to the porous structure and good dispersity, which facilitated sufficient transport of ions, electrons, O2 and other reactants in the process of ORR. The results indicated that a facile and feasible sonochemical route could be used to prepare highly active porous MnO2 electrocatalyst for ORR, which might be promising for direct methanol fuel cells.

  9. 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.

  10. The mechanisms of oxygen reduction and evolution reactions in nonaqueous lithium-oxygen batteries.

    PubMed

    Cao, Ruiguo; Walter, Eric D; Xu, Wu; Nasybulin, Eduard N; Bhattacharya, Priyanka; Bowden, Mark E; Engelhard, Mark H; Zhang, Ji-Guang

    2014-09-01

    A fundamental understanding of the mechanisms of both the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) in nonaqueous lithium-oxygen (Li-O2) batteries is essential for the further development of these batteries. In this work, we systematically investigate the mechanisms of the ORR/OER reactions in nonaqueous Li-O2 batteries by using electron paramagnetic resonance (EPR) spectroscopy, using 5,5-dimethyl-pyrroline N-oxide as a spin trap. The study provides direct verification of the formation of the superoxide radical anion (O2(˙-)) as an intermediate in the ORR during the discharge process, while no O2(˙-) was detected in the OER during the charge process. These findings provide insight into, and an understanding of, the fundamental reaction mechanisms involving oxygen and guide the further development of this field. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Intrinsic relationship between enhanced oxygen reduction reaction activity and nanoscale work function of doped carbons.

    PubMed

    Cheon, Jae Yeong; Kim, Jong Hun; Kim, Jae Hyung; Goddeti, Kalyan C; Park, Jeong Young; Joo, Sang Hoon

    2014-06-25

    Nanostructured carbon materials doped with a variety of heteroatoms have shown promising electrocatalytic activity in the oxygen reduction reaction (ORR). However, understanding of the working principles that underpin the superior ORR activity observed with doped nanocarbons is still limited to predictions based on theoretical calculations. Herein, we demonstrate, for the first time, that the enhanced ORR activity in doped nanocarbons can be correlated with the variation in their nanoscale work function. A series of doped ordered mesoporous carbons (OMCs) were prepared using N, S, and O as dopants; the triple-doped, N,S,O-OMC displayed superior ORR activity and four-electron selectivity compared to the dual-doped (N,O-OMC and S,O-OMC) and the monodoped (O-OMC) OMCs. Significantly, the work functions of these heteroatom-doped OMCs, measured by Kelvin probe force microscopy, display a strong correlation with the activity and reaction kinetics for the ORR. This unprecedented experimental insight can be used to provide an explanation for the enhanced ORR activity of heteroatom-doped carbon materials.

  12. Fe3C nanoparticle decorated Fe/N doped graphene for efficient oxygen reduction reaction electrocatalysis

    NASA Astrophysics Data System (ADS)

    Niu, Yanli; Huang, Xiaoqin; Hu, Weihua

    2016-11-01

    Oxygen reduction reaction (ORR) electrocatalysts with high activity, low cost and good durability are crucial to promote the large-scale practical application of fuel cells. Particularly, iron carbide (Fe3C) supported on nitrogen-doped carbon has recently demonstrated compelling promise for ORR electrocatalysis. In this paper, we report the facile synthesis of mesoporous Fe/N-doped graphene with encapsulated Fe3C nanoparticles (Fe3C@Fe/N-graphene) and its superior ORR catalytic activity. This hybrid material was synthesized by the spontaneous oxidative polymerization of dopamine on graphene oxide (GO) sheets in the presence of iron ion, followed by thermal annealing in Argon (Ar) atmosphere. As-prepared material shows high ORR catalytic activity with overwhelming four-electron reduction pathway, long-term durability and high methanol tolerance in alkaline media. This work reports a facile method to synthesize promising ORR electrocatalysis with multiple components and hierarchical architecture, and may offer valuable insight into the underlying mechanism of Fe3C-boosted ORR activity of Fe/N doped carbon.

  13. Using ordered carbon nanomaterials for shedding light on the mechanism of the cathodic oxygen reduction reaction.

    PubMed

    Ruvinskiy, Pavel S; Bonnefont, Antoine; Pham-Huu, Cuong; Savinova, Elena R

    2011-07-19

    Insufficient understanding of the mechanism of the cathodic oxygen reduction reaction puts constraints on the improvement of the efficiency of polymer electrolyte fuel cells (PEMFCs). We apply ordered catalytic layers based on vertically aligned carbon nanofilaments and combine experimental rotating ring-disk studies with mathematical modeling for shedding light on the mechanism of the oxygen reduction reaction on Pt nanoparticles. Based on the experimental and simulation evidence we propose a dual path ORR mechanism which comprises a "direct 4e(-)" and a "series 2e(-) + 2e(-)" pathway and explains switching between the two. For the first time we show that below 0.8 V the "direct" path may be discarded and the ORR predominantly occurs via H(2)O(2) mediated pathway, while in the potential interval between ca. 0.8 V and the onset of the ORR the "direct" path is dominating.

  14. The Mechanisms of Oxygen Reduction and Evolution Reactions in Nonaqueous Lithium-Oxygen Batteries

    SciTech Connect

    Cao, Ruiguo; Walter, Eric D.; Xu, Wu; Nasybulin, Eduard N.; Bhattacharya, Priyanka; Bowden, Mark E.; Engelhard, Mark H.; Zhang, Jiguang

    2014-09-01

    The oxygen reduction/evolution reaction (ORR/OER) mechanisms in nonaqueous Li-O2 batteries have been investigated by using electron paramagnetic resonance spectroscopy in this work. We identified the superoxide radical anion (O2•-) as an intermediate in the ORR process using 5,5-dimethyl-pyrroline N-oxide as a spin trap, while no O2•- in OER was detected during the charge process. These findings provide insightful understanding on the fundamental oxygen reaction mechanisms in rechargeable nonaqueous Li-O2 batteries.

  15. Linking structure to function: The search for active sites in non-platinum group metal oxygen reduction reaction catalysts

    SciTech Connect

    Holby, Edward F.; Zelenay, Piotr

    2016-05-17

    Atomic-scale structures of oxygen reduction reaction (ORR) active sites in non-platinum group metal (non-PGM) catalysts, made from pyrolysis of carbon, nitrogen, and transition-metal (TM) precursors have been the subject of continuing discussion in the fuel cell electrocatalysis research community. We found that quantum chemical modeling is a path forward for understanding of these materials and how they catalyze the ORR. Here, we demonstrate through literature examples of how such modeling can be used to better understand non-PGM ORR active site relative stability and activity and how such efforts can also aid in the interpretation of experimental signatures produced by these materials.

  16. Linking structure to function: The search for active sites in non-platinum group metal oxygen reduction reaction catalysts

    SciTech Connect

    Holby, Edward F.; Zelenay, Piotr

    2016-05-17

    Atomic-scale structures of oxygen reduction reaction (ORR) active sites in non-platinum group metal (non-PGM) catalysts, made from pyrolysis of carbon, nitrogen, and transition-metal (TM) precursors have been the subject of continuing discussion in the fuel cell electrocatalysis research community. We found that quantum chemical modeling is a path forward for understanding of these materials and how they catalyze the ORR. Here, we demonstrate through literature examples of how such modeling can be used to better understand non-PGM ORR active site relative stability and activity and how such efforts can also aid in the interpretation of experimental signatures produced by these materials.

  17. Some reflections on the understanding of the oxygen reduction reaction at Pt(111).

    PubMed

    Gómez-Marín, Ana M; Rizo, Ruben; Feliu, Juan M

    2013-12-27

    The oxygen reduction reaction (ORR) is a pivotal process in electrochemistry. Unfortunately, after decades of intensive research, a fundamental knowledge about its reaction mechanism is still lacking. In this paper, a global and critical view on the most important experimental and theoretical results regarding the ORR on Pt(111) and its vicinal surfaces, in both acidic and alkaline media, is taken. Phenomena such as the ORR surface structure sensitivity and the lack of a reduction current at high potentials are discussed in the light of the surface oxidation and disordering processes and the possible relevance of the hydrogen peroxide reduction and oxidation reactions in the ORR mechanism. The necessity to build precise and realistic reaction models, which are deducted from reliable experimental results that need to be carefully taken under strict working conditions is shown. Therefore, progress in the understanding of this important reaction on a molecular level, and the choice of the right approach for the design of the electrocatalysts for fuel-cell cathodes is only possible through a cooperative approach between theory and experiments.

  18. Some reflections on the understanding of the oxygen reduction reaction at Pt(111)

    PubMed Central

    Gómez-Marín, Ana M; Rizo, Ruben

    2013-01-01

    Summary The oxygen reduction reaction (ORR) is a pivotal process in electrochemistry. Unfortunately, after decades of intensive research, a fundamental knowledge about its reaction mechanism is still lacking. In this paper, a global and critical view on the most important experimental and theoretical results regarding the ORR on Pt(111) and its vicinal surfaces, in both acidic and alkaline media, is taken. Phenomena such as the ORR surface structure sensitivity and the lack of a reduction current at high potentials are discussed in the light of the surface oxidation and disordering processes and the possible relevance of the hydrogen peroxide reduction and oxidation reactions in the ORR mechanism. The necessity to build precise and realistic reaction models, which are deducted from reliable experimental results that need to be carefully taken under strict working conditions is shown. Therefore, progress in the understanding of this important reaction on a molecular level, and the choice of the right approach for the design of the electrocatalysts for fuel-cell cathodes is only possible through a cooperative approach between theory and experiments. PMID:24455454

  19. Communication: Enhanced oxygen reduction reaction and its underlying mechanism in Pd-Ir-Co trimetallic alloys

    SciTech Connect

    Ham, Hyung Chul; Hwang, Gyeong S.; Manogaran, Dhivya; Lee, Kang Hee; Jin, Seon-ah; You, Dae Jong; Pak, Chanho; Kwon, Kyungjung

    2013-11-28

    Based on a combined density functional theory and experimental study, we present that the electrochemical activity of Pd{sub 3}Co alloy catalysts toward oxygen reduction reaction (ORR) can be enhanced by adding a small amount of Ir. While Ir tends to favorably exist in the subsurface layers, the underlying Ir atoms are found to cause a substantial modification in the surface electronic structure. As a consequence, we find that the activation barriers of O/OH hydrogenation reactions are noticeably lowered, which would be mainly responsible for the enhanced ORR activity. Furthermore, our study suggests that the presence of Ir in the near-surface region can suppress Co out-diffusion from the Pd{sub 3}Co substrate, thereby improving the durability of Pd-Ir-Co catalysts. We also discuss the relative roles played by Ir and Co in enhancing the ORR activity relative to monometallic Pd catalysts.

  20. “Metal-free” catalytic oxygen reduction reaction on heteroatom- doped graphene is caused by trace metal impurities.

    PubMed

    Wang, Lu; Ambrosi, Adriano; Pumera, Martin

    2013-12-16

    The oxygen reduction reaction (ORR) is of high industrial importance. There is a large body of literature showing that metal-based catalytic nanoparticles (e.g. Co, Mn, Fe or hybrid Mn/Co-based nanoparticles) supported on graphene act as efficient catalysts for the ORR. A significant research effort is also directed to the so-called “metal-free” oxygen reduction reaction on heteroatom-doped graphene surfaces. While such studies of the ORR on nonmetallic heteroatom-doped graphene are advertised as “metal-free” there is typically no sufficient effort to characterize the doped materials to verify that they are indeed free of any trace metal. Here we argue that the claimed “metal-free” electrocatalysis of the oxygen reduction reaction on heteroatom-doped graphene is caused by metallic impurities present within the graphene materials.

  1. Active sites and mechanisms for oxygen reduction reaction on nitrogen-doped carbon alloy catalysts: Stone-Wales defect and curvature effect.

    PubMed

    Chai, Guo-Liang; Hou, Zhufeng; Shu, Da-Jun; Ikeda, Takashi; Terakura, Kiyoyuki

    2014-10-01

    Carbon alloy catalysts (CACs) are promising oxygen reduction reaction (ORR) catalysts to substitute platinum. However, despite extensive studies on CACs, the reaction sites and mechanisms for ORR are still in controversy. Herein, we present rather general consideration on possible ORR mechanisms for various structures in nitrogen doped CACs based on the first-principles calculations. Our study indicates that only a particular structure of a nitrogen pair doped Stone-Wales defect provides a good active site. The ORR activity of this structure can be tuned by the curvature around the active site, which makes its limiting potential approaching the maximum limiting potential (0.80 V) in the volcano plot for the ORR activity of CACs. The calculated results can be compared with the recent experimental ones of the half-wave potential for CAC systems that range from 0.60 to 0.80 V in the reversible-hydrogen-electrode (RHE) scale.

  2. Hetero-atom doped carbon nanotubes for dye degradation and oxygen reduction reaction

    SciTech Connect

    Nandan, Ravi Nanda, Karuna Kar

    2015-06-24

    We report the synthesis of nitrogen doped vertically aligned multi-walled (MWNCNTs) carbon nanotubes by pyrolysis and its catalytic performance for degradation of methylene blue (MB) dye & oxygen reduction reaction (ORR). The degradation of MB was monitored spectrophotometrically with time. Kinetic studies show the degradation of MB follows a first order kinetic with rate constant k=0.0178 min{sup −1}. The present rate constant is better than that reported for various supported/non-supported semiconducting nanomaterials. Further ORR performance in alkaline media makes MWNCNTs a promising cost-effective, fuel crossover tolerance, metal-free, eco-friendly cathode catalyst for direct alcohol fuel cell.

  3. Enhancing oxygen reduction reaction activity of Pt-shelled catalysts via subsurface alloying.

    PubMed

    Cheng, Daojian; Qiu, Xiangguo; Yu, Haiyan

    2014-10-14

    Despite remarkable efforts have been put into the field of Pt-shelled catalysts containing an atomically thin Pt surface layer for the oxygen reduction reaction (ORR) in the last decade, further development of new Pt-shelled catalysts is still necessary. Here, a new set of Pt-shelled catalysts by subsurface alloying with early transition metals such as Mn and Fe is predicted to be a good candidate for the ORR by using density functional theory (DFT) calculations. Trends in oxygen reduction activity of Pt-alloy catalysts are determined with calculations of oxygen binding by using the slab and cluster models. It is found that the subsurface alloys by the incorporation of submonolayer M (M = Mn and Fe) into Pt(111) in the slab model result in the enhancement of ORR activity, compared with the well-known Pt(111)-skin-M, pure Pt, and Pt3M alloy catalysts. For the cluster model, the Pt12Mn and Pt12Fe clusters are also found to be the optimal catalysts for the ORR. It is expected that this work can open up new opportunities for enhancing the ORR activity of Pt-alloy catalysts by subsurface alloying.

  4. Carbonization of self-assembled nanoporous hemin with a significantly enhanced activity for the oxygen reduction reaction.

    PubMed

    Xie, Yan; Tang, Chizhou; Hao, Zhiqiang; Lv, Yang; Yang, Ruixia; Wei, Xuming; Deng, Weiqiao; Wang, Anjie; Yi, Baolian; Song, Yujiang

    2014-01-01

    The scarcity and high cost of Pt-based electrocatalysts for the oxygen reduction reaction (ORR) hinder the practical application of proton exchange membrane fuel cells (PEMFCs). It is critical to replace platinum with non-noble metal electrocatalysts (NNMEs). Carbonized metalloporphyrins represent an important class of NNMEs, but most metalloporphyrins are costly and the corresponding NNMEs do not possess a high ORR activity. Herein, we report that the self-assembly of inexpensive hemin leads to porous nanomaterials in water under ambient conditions and subsequent heat-treatment of the unprecedented nanoporous hemin results in a magnetic NNME with a much enhanced ORR activity compared with directly carbonized hemin without self-assembly. The improvement of the ORR activity likely originates from the exposure of more ORR active sites, caused by the surface area increase of the nanoporous hemin after carbonization over that of micro-scale pristine hemin crystals. Moreover, the ORR activity of heat-treated nanoporous hemin is actually comparable to that of commercial Pt/C in alkaline solution. Additionally, the carbonized nanoporous hemin is much better than commercial Pt/C in terms of durability and tolerance to methanol. This study opens up a new avenue to the production of inexpensive metalloporphyrin-based NNMEs with a high ORR performance by using a self-assembly method in combination with traditional pyrolysis.

  5. Reduction of chemical reaction models

    NASA Technical Reports Server (NTRS)

    Frenklach, Michael

    1991-01-01

    An attempt is made to reconcile the different terminologies pertaining to reduction of chemical reaction models. The approaches considered include global modeling, response modeling, detailed reduction, chemical lumping, and statistical lumping. The advantages and drawbacks of each of these methods are pointed out.

  6. Nitrogen doped carbon nanotubes with encapsulated ferric carbide as excellent electrocatalyst for oxygen reduction reaction in acid and alkaline media

    NASA Astrophysics Data System (ADS)

    Zhong, Guoyu; Wang, Hongjuan; Yu, Hao; Peng, Feng

    2015-07-01

    Nitrogen doped carbon nanotubes (NCNTs) with encapsulated Fe3C nanoparticles (Fe3C@NCNTs) are synthesized by a simple direct pyrolysis of melamine and ferric chloride. The characterization results reveal that Fe3C is mainly encapsulated in the interior of NCNTs and N species is mainly distributed on the outside surface of NCNTs. Iron and iron carbide catalyze the growth of NCNTs and are wrapped by carbon to form Fe3C@NCNTs. The as-prepared Fe3C@NCNTs catalyst exhibits superior oxygen reduction reaction (ORR) activity, excellent methanol tolerance and long-term stability in both acid and alkaline media. It is proven that the doped N is the main active site for ORR and the inner Fe3C with outside carbon form the synergetic active site to enhance ORR activity. The ORR mechanism of direct four electron transfer pathway is proved in acid and alkaline media.

  7. Surface Structure Dependent Electrocatalytic Activity of Co3O4 Anchored on Graphene Sheets toward Oxygen Reduction Reaction

    PubMed Central

    Xiao, Junwu; Kuang, Qin; Yang, Shihe; Xiao, Fei; Wang, Shuai; Guo, Lin

    2013-01-01

    Catalytic activity is primarily a surface phenomenon, however, little is known about Co3O4 nanocrystals in terms of the relationship between the oxygen reduction reaction (ORR) catalytic activity and surface structure, especially when dispersed on a highly conducting support to improve the electrical conductivity and so to enhance the catalytic activity. Herein, we report a controllable synthesis of Co3O4 nanorods (NR), nanocubes (NC) and nano-octahedrons (OC) with the different exposed nanocrystalline surfaces ({110}, {100}, and {111}), uniformly anchored on graphene sheets, which has allowed us to investigate the effects of the surface structure on the ORR activity. Results show that the catalytically active sites for ORR should be the surface Co2+ ions, whereas the surface Co3+ ions catalyze CO oxidation, and the catalytic ability is closely related to the density of the catalytically active sites. These results underscore the importance of morphological control in the design of highly efficient ORR catalysts. PMID:23892418

  8. Nitrogen-rich mesoporous carbon derived from melamine with high electrocatalytic performance for oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Wang, Rongfang; Zhou, Tiaobao; Li, Hao; Wang, Hui; Feng, Hanqing; Goh, Jonathan; Ji, Shan

    2014-09-01

    Melamine-derived N-doped mesoporous carbon (MNMC) is synthesized by the pyrolysis of lysine and melamineunder at nitrogen atmosphere using ferric chloride as a dopant and SiO2 nanoparticles as hard templates to form mesoporous architecture. The N content in the bulk of carbon materials is as high as 11.3% and ca. 40.6% of N is in the form of pyridinic-N. The surface area of MNMC is ca. 650 m2 g-1 with a pore size distribution in the range of 2.2-34.5 nm. Compared to commercial Pt/C (20 wt%), MNMC exhibits much better electrocatalytic activity, better durability, and higher methanol tolerance for oxygen reduction reaction (ORR) in alkaline medium. Particularly, the onset ORR potential and half-wave ORR potential of MNMC are 1.059 and 0.871 V vs. RHE respectively, which are higher than those of commercial Pt/C.

  9. Suppression of oxygen reduction reaction activity on Pt-based electrocatalysts from ionomer incorporation

    SciTech Connect

    Shinozaki, Kazuma; Morimoto, Yu; Pivovar, Bryan S.; Kocha, Shyam S.

    2016-09-01

    The impact of Nafion on the oxygen reduction reaction (ORR) activity is studied for Pt/C and Pt-alloy/C catalysts using thin-film rotating disk electrode (TF-RDE) methods in 0.1 M HClO4. Ultrathin uniform catalyst layers and standardized activity measurement protocols are employed to obtain accurate and reproducible ORR activity. Nafion lowers the ORR activity which plateaus with increasing loading on Pt catalysts. Pt particle size is found not to have significant influence on the extent of the SA decrease upon Nafion incorporation. Catalysts using high surface area carbon (HSC) support exhibit attenuated activity loss resulting from lower ionomer coverage on catalyst particles located within the deep pores. The impact of metallic composition on the activity loss due to Nafion incorporation is also discussed.

  10. Cobalt diselenide nanoparticles embedded within porous carbon polyhedra as advanced electrocatalyst for oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Wu, Renbing; Xue, Yanhong; Liu, Bo; Zhou, Kun; Wei, Jun; Chan, Siew Hwa

    2016-10-01

    Highly efficient and cost-effective electrocatalyst for the oxygen reduction reaction (ORR) is crucial for a variety of renewable energy applications. Herein, strongly coupled hybrid composites composed of cobalt diselenide (CoSe2) nanoparticles embedded within graphitic carbon polyhedra (GCP) as high-performance ORR catalyst have been rationally designed and synthesized. The catalyst is fabricated by a convenient method, which involves the simultaneous pyrolysis and selenization of preformed Co-based zeolitic imidazolate framework (ZIF-67). Benefiting from the unique structural features, the resulting CoSe2/GCP hybrid catalyst shows high stability and excellent electrocatalytic activity towards ORR (the onset and half-wave potentials are 0.935 and 0.806 V vs. RHE, respectively), which is superior to the state-of-the-art commercial Pt/C catalyst (0.912 and 0.781 V vs. RHE, respectively).

  11. Oxygen reduction reaction over silver particles with various morphologies and surface chemical states

    NASA Astrophysics Data System (ADS)

    Ohyama, Junya; Okata, Yui; Watabe, Noriyuki; Katagiri, Makoto; Nakamura, Ayaka; Arikawa, Hidekazu; Shimizu, Ken-ichi; Takeguchi, Tatsuya; Ueda, Wataru; Satsuma, Atsushi

    2014-01-01

    The oxygen reduction reaction (ORR) in an alkaline solution was carried out using Ag powders having various particle morphologies and surface chemical states (Size: ca. 40-110 nm in crystalline size. Shape: spherical, worm like, and angular. Surface: smooth with easily reduced AgOx, defective with AgOx, and Ag2CO3 surface layer). The various Ag powders were well characterized by X-ray diffraction, X-ray photoelectron spectroscopy, N2 adsorption, scanning electron microscopy, Raman spectroscopy, cyclic voltammetry, and stripping voltammetry of underpotential-deposited lead. Defective and oxidized surfaces enhanced the Ag active surface area during the ORR. The ORR activity was affected by the morphology and surface chemical state: Ag particles with defective and angular surfaces showed smaller electron exchange number between three and four but showed higher specific activity compared to Ag particles with smooth surfaces.

  12. Modified Graphene as Electrocatalyst towards Oxygen Reduction Reaction for Fuel Cells

    NASA Astrophysics Data System (ADS)

    Qazzazie, D.; Beckert, M.; Mülhaupt, R.; Yurchenko, O.; Urban, G.

    2014-11-01

    This paper reports modified graphene-based materials as metal-free electrocatalysts for oxygen reduction reaction (ORR) with outstanding electrocatalytic activity in alkaline conditions. Nitrogen-doped graphene samples are synthesized by a novel procedure. The defect density in the structure of the prepared materials is investigated by Raman spectroscopy. Further structural characterization by X-ray photoelectron spectroscopy reveals the successful nitrogen doping of graphene. The electrochemical characterization of graphene and nitrogen-doped graphene in 0.1 M KOH solution demonstrates the material's electrocatalytic activity towards ORR. For graphene an onset potential of - 0.175 V vs. Ag/AgCl reference electrode is determined, while for nitrogen-doped graphene the determined onset potential is - 0.160 V. Thus, the electrocatalytic activity of nitrogen-doped graphene towards ORR is enhanced which can be ascribed to the effect of nitrogen doping.

  13. Oxygen reduction reaction on Cu-doped Ag cluster for fuel-cell cathode.

    PubMed

    Ma, Wenqiang; Chen, Fuyi; Zhang, Nan; Wu, Xiaoqiang

    2014-10-01

    The development of fuel cells as clean-energy technologies is largely limited by the prohibitive cost of the noble-metal catalysts needed for catalyzing the oxygen reduction reaction (ORR) in fuel cells. A fundamental understanding of catalyst design principle that links material structures to the catalytic activity can accelerate the search for highly active and abundant bimetallic catalysts to replace platinum. Here, we present a first-principles study of ORR on Ag12Cu cluster in alkaline environment. The adsorptions of O2, OOH, and OH on Cu-doped Ag13 are stronger than on Ag13. The d-band centers of adsorption sites show the Cu-doping makes d-electrons transferred to higher energy state, and improves O2 dissociation. ORR processes on Ag12Cu and Ag13 indicate Cu-doping can strongly promote ORR, and ORR process can be better preformed on Ag12Cu than on Ag13. For four-electron transfer, the effective reversible potential is 0.401 V/RHE on Ag12Cu in alkaline medium.

  14. Carbonized nanoscale metal-organic frameworks as high performance electrocatalyst for oxygen reduction reaction.

    PubMed

    Zhao, Shenlong; Yin, Huajie; Du, Lei; He, Liangcan; Zhao, Kun; Chang, Lin; Yin, Geping; Zhao, Huijun; Liu, Shaoqin; Tang, Zhiyong

    2014-12-23

    The oxygen reduction reaction (ORR) is one of the key steps in clean and efficient energy conversion techniques such as in fuel cells and metal-air batteries; however, several disadvantages of current ORRs including the kinetically sluggish process and expensive catalysts hinder mass production of these devices. Herein, we develop carbonized nanoparticles, which are derived from monodisperse nanoscale metal organic frameworks (MIL-88B-NH3), as the high performance ORR catalysts. The onset potential and the half-wave potential for the ORR at these carbonized nanoparticles is up to 1.03 and 0.92 V (vs RHE) in 0.1 M KOH solution, respectively, which represents the best ORR activity of all the non-noble metal catalysts reported so far. Furthermore, when used as the cathode of the alkaline direct fuel cell, the power density obtained with the carbonized nanoparticles reaches 22.7 mW/cm2, 1.7 times higher than the commercial Pt/C catalysts.

  15. Palladium and gold nanotubes as oxygen reduction reaction and alcohol oxidation reaction catalysts in base.

    PubMed

    Alia, Shaun M; Duong, Kathlynne; Liu, Toby; Jensen, Kurt; Yan, Yushan

    2014-06-01

    Palladium (PdNTs) and gold nanotubes (AuNTs) were synthesized by the galvanic displacement of silver nanowires. PdNTs and AuNTs have wall thicknesses of 6 nm, outer diameters of 60 nm, and lengths of 5-10 and 5-20 μm, respectively. Rotating disk electrode experiments showed that the PdNTs and AuNTs have higher area normalized activities for the oxygen reduction reaction (ORR) than conventional nanoparticle catalysts. The PdNTs produced an ORR area activity that was 3.4, 2.2, and 3.7 times greater than that on carbon-supported palladium nanoparticles (Pd/C), bulk polycrystalline palladium, and carbon-supported platinum nanoparticles (Pt/C), respectively. The AuNTs produced an ORR area activity that was 2.3, 9.0, and 2.0 times greater than that on carbon-supported gold nanoparticles (Au/C), bulk polycrystalline gold, and Pt/C, respectively. The PdNTs also had lower onset potentials than Pd/C and Pt/C for the oxidation of methanol (0.236 V), ethanol (0.215 V), and ethylene glycol (0.251 V). In comparison to Pt/C, the PdNTs and AuNTs further demonstrated improved alcohol tolerance during the ORR. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Easy conversion of protein-rich enoki mushroom biomass to a nitrogen-doped carbon nanomaterial as a promising metal-free catalyst for oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Guo, Chaozhong; Liao, Wenli; Li, Zhongbin; Sun, Lingtao; Chen, Changguo

    2015-09-01

    The search for low-cost, highly active, and stable catalysts to replace the Pt-based catalysts for oxygen reduction reaction (ORR) has recently become a topic of interest. Herein, we report a new strategy to design a nitrogen-doped carbon nanomaterial for use as a metal-free ORR catalyst based on facile pyrolysis of protein-rich enoki mushroom (Flammulina velutipes) biomass at 900 °C with carbon nanotubes as a conductive agent and inserting matrix. We found that various forms of nitrogen (nitrile, pyrrolic and graphitic) were incorporated into the carbon molecular skeleton of the product, which exhibited more excellent ORR electrocatalytic activity and better durability in alkaline medium than those in acidic medium. Remarkably, the ORR half-wave potential measured on our material was around 0.81 V in alkaline medium, slightly lower than that on the commercial 20 wt% Pt/C catalyst (0.86 V). Meanwhile, the ORR followed the desired 4-electron transfer mechanism involving the direct reduction pathway. The ORR performance was also markedly better than or at least comparable to the leading results in the literature based on biomass-derived carbon-based catalysts. Besides, we significantly proposed that the graphitic-nitrogen species that is most responsible for the ORR activity can function as the electrocatalytically active center for ORR, and the pyrrolic-nitrogen species can act as an effective promoter for ORR only. The results suggested a promising route based on economical and sustainable fungi biomass towards the large-scale production of valuable carbon nanomaterials as highly active and stable metal-free catalysts for ORR under alkaline conditions.The search for low-cost, highly active, and stable catalysts to replace the Pt-based catalysts for oxygen reduction reaction (ORR) has recently become a topic of interest. Herein, we report a new strategy to design a nitrogen-doped carbon nanomaterial for use as a metal-free ORR catalyst based on facile pyrolysis of

  17. Oxygen reduction reaction on stepped platinum surfaces in alkaline media.

    PubMed

    Rizo, Ruben; Herrero, Enrique; Feliu, Juan M

    2013-10-07

    The oxygen reduction reaction (ORR) in 0.1 M NaOH on platinum single crystal electrodes has been studied using hanging meniscus rotating disk electrode configuration. Basal planes and stepped surfaces with (111) and (100) terraces have been employed. The results indicate that the Pt(111) electrode has the highest electrocatalytic activity among all the studied surfaces. The addition of steps on this electrode surface significantly diminishes the reactivity of the surface towards the ORR. In fact, the reactivity of the steps on the surfaces with wide terraces can be considered negligible with respect to that measured for the terrace. On the other hand, Pt(100) and Pt(110) electrodes have much lower activity than the Pt(111) electrode. These results have been compared with those obtained in acid media to understand the effect of the pH and the adsorbed OH on the mechanism. It is proposed that the surface covered by adsorbed OH is active for the reduction of the oxygen molecules.

  18. Boron- and Nitrogen-Substituted Graphene Nanoribbons as Efficient Catalysts for Oxygen Reduction Reaction

    DOE PAGES

    Gong, Yongji; Fei, Huilong; Zou, Xiaolong; ...

    2015-02-02

    Here, we show that nanoribbons of boron- and nitrogen-substituted graphene can be used as efficient electrocatalysts for the oxygen reduction reaction (ORR). Optimally doped graphene nanoribbons made into three-dimensional porous constructs exhibit the highest onset and half-wave potentials among the reported metal-free catalysts for this reaction and show superior performance compared to commercial Pt/C catalyst. Moreover, this catalyst possesses high kinetic current density and four-electron transfer pathway with low hydrogen peroxide yield during the reaction. Finally, first-principles calculations suggest that such excellent electrocatalytic properties originate from the abundant edges of boron- and nitrogen-codoped graphene nanoribbons, which significantly reduce the energymore » barriers of the rate-determining steps of the ORR reaction.« less

  19. Boron- and Nitrogen-Substituted Graphene Nanoribbons as Efficient Catalysts for Oxygen Reduction Reaction

    SciTech Connect

    Gong, Yongji; Fei, Huilong; Zou, Xiaolong; Zhou, Wu; Yang, Shubin; Ye, Gonglan; Liu, Zheng; Peng, Zhiwei; Lou, Jun; Vajtai, Robert; Yakobson, Boris I.; Tour, James M.; Ajayan, Pulickel M.

    2015-02-02

    Here, we show that nanoribbons of boron- and nitrogen-substituted graphene can be used as efficient electrocatalysts for the oxygen reduction reaction (ORR). Optimally doped graphene nanoribbons made into three-dimensional porous constructs exhibit the highest onset and half-wave potentials among the reported metal-free catalysts for this reaction and show superior performance compared to commercial Pt/C catalyst. Moreover, this catalyst possesses high kinetic current density and four-electron transfer pathway with low hydrogen peroxide yield during the reaction. Finally, first-principles calculations suggest that such excellent electrocatalytic properties originate from the abundant edges of boron- and nitrogen-codoped graphene nanoribbons, which significantly reduce the energy barriers of the rate-determining steps of the ORR reaction.

  20. Electrocatalysts Derived from Metal-Organic Frameworks for Oxygen Reduction and Evolution Reactions in Aqueous Media.

    PubMed

    Qian, Yuhong; Khan, Inayat Ali; Zhao, Dan

    2017-10-01

    Electrochemical energy conversion and storage devices such as fuel cells and metal-air batteries have been extensively studied in recent decades for their excellent conversion efficiency, high energy capacity, and low environmental impact. However, sluggish kinetics of the oxygen-related reactions at air cathodes, i.e., oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), are still worth improving. Noble metals such as platinum (Pt), iridium (Ir), ruthenium (Ru) and their oxides are considered as the benchmark ORR and OER electrocatalysts, but they are expensive and prone to be poisoned due to the fuel crossover effect, and may suffer from agglomeration and leaching after long-term usage. To mitigate these limits, it is highly desirable to design alternative ORR/OER electrocatalysts with prominent performance. Metal-organic frameworks (MOFs) are a class of porous crystalline materials consisting metal ions/clusters coordinated by organic ligands. Their crystalline structure, tunable pore size and high surface area afford them wide opportunities as catalytic materials. This Review covers MOF-derived ORR/OER catalysts in electrochemical energy conversion, with a focus on the different strategies of material design and preparation, such as composition control and nanostructure fabrication, to improve the activity and durability of MOF-derived electrocatalysts. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Mechanism of oxygen reduction reaction on Pt(111) in alkaline solution: Importance of chemisorbed water on surface

    DOE PAGES

    Liu, Shizhong; White, Michael G.; Liu, Ping

    2016-06-30

    Here, we report a detailed mechanistic study of the oxygen reduction reaction (ORR) on Pt(111) in alkaline solution, combining density functional theory and kinetic Monte Carlo simulations. A complex reaction network including four possible pathways via either 2e– or 4e– transfer is established and is able to reproduce the experimental measured polarization curve at both low- and high-potential regions. Our results show that it is essential to account for solvation by water and the dynamic coverage of *OH to describe the reaction kinetics well. In addition, a chemisorbed water (*H2O)-mediated mechanism including 4e– transfers is identified, where the reduction stepsmore » via *H2O on the surface are potential-independent and only the final removal of *OH from the surface in the form of OH–(aq) contributes to the current. For the ORR in alkaline solutions, such a mechanism is more competitive than the associative and dissociative mechanisms typically used to describe the ORR in acid solution. Finally, *OH and **O2 intermediates are found to be critically important for tuning the ORR activity of Pt in alkaline solution. To enhance the activity, the binding of Pt should be tuned in such a way that *OH binding is weak enough to release more surface sites under working conditions, while **O2 binding is strong enough to enable the ORR via the 4e– transfer mechanism.« less

  2. Surface profile control of FeNiPt/Pt core/shell nanowires for oxygen reduction reaction

    DOE PAGES

    Zhu, Huiyuan; Zhang, Sen; Su, Dong; ...

    2015-03-18

    The ever-increasing energy demand requires renewable energy schemes with low environmental impacts. Electrochemical energy conversion devices, such as fuel cells, combine fuel oxidization and oxygen reduction reactions and have been studied extensively for renewable energy applications. However, their energy conversion efficiency is often limited by kinetically sluggish chemical conversion reactions, especially oxygen reduction reaction (ORR). [1-5] To date, extensive efforts have been put into developing efficient ORR catalysts with controls on catalyst sizes, compositions, shapes and structures. [6-12] Recently, Pt-based catalysts with core/shell and one-dimensional nanowire (NW) morphologies were found to be promising to further enhance ORR catalysis. With themore » core/shell structure, the ORR catalysis of a nanoparticle (NP) catalyst can be tuned by both electronic and geometric effects at the core/shell interface. [10,13,14] With the NW structure, the catalyst interaction with the conductive support can be enhanced to facilitate electron transfer between the support and the NW catalyst and to promote ORR. [11,15,16]« less

  3. Surface profile control of FeNiPt/Pt core/shell nanowires for oxygen reduction reaction

    SciTech Connect

    Zhu, Huiyuan; Zhang, Sen; Su, Dong; Jiang, Guangming; Sun, Shouheng

    2015-03-18

    The ever-increasing energy demand requires renewable energy schemes with low environmental impacts. Electrochemical energy conversion devices, such as fuel cells, combine fuel oxidization and oxygen reduction reactions and have been studied extensively for renewable energy applications. However, their energy conversion efficiency is often limited by kinetically sluggish chemical conversion reactions, especially oxygen reduction reaction (ORR). [1-5] To date, extensive efforts have been put into developing efficient ORR catalysts with controls on catalyst sizes, compositions, shapes and structures. [6-12] Recently, Pt-based catalysts with core/shell and one-dimensional nanowire (NW) morphologies were found to be promising to further enhance ORR catalysis. With the core/shell structure, the ORR catalysis of a nanoparticle (NP) catalyst can be tuned by both electronic and geometric effects at the core/shell interface. [10,13,14] With the NW structure, the catalyst interaction with the conductive support can be enhanced to facilitate electron transfer between the support and the NW catalyst and to promote ORR. [11,15,16]

  4. Pt nanoparticle and Fe,N-codoped 3D graphene as synergistic electrocatalyst for oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Qin, Yong; Chao, Lei; He, Jing Jing; Liu, Yang; Chu, Fuqiang; Cao, Jianyu; Kong, Yong; Tao, Yongxin

    2016-12-01

    Ultrafine Pt nanoparticles (PtNPs) with the diameter of ∼2.5 nm were successfully confined within Fe,N-codoped robust 3D graphene (Fe-N/R3DG) via facile polyol-assisted reduction strategy. Owing to the synergistic effect between the active catalyst (PtNPs) and the support (Fe-N/R3DG), the as-obtained composite exhibited better cyclic stability and long-term durability as well as less methanol toxicity, moreover, 8 times higher specific activity than the commercial Pt/C for oxygen reduction reaction (ORR) in alkaline medium. The results bring new insight into the design of excellent ORR catalyst.

  5. Metal-Free Carbon-Based Materials: Promising Electrocatalysts for Oxygen Reduction Reaction in Microbial Fuel Cells

    PubMed Central

    Sawant, Sandesh Y.; Han, Thi Hiep; Cho, Moo Hwan

    2016-01-01

    Microbial fuel cells (MFCs) are a promising green approach for wastewater treatment with the simultaneous advantage of energy production. Among the various limiting factors, the cathodic limitation, with respect to performance and cost, is one of the main obstacles to the practical applications of MFCs. Despite the high performance of platinum and other metal-based cathodes, their practical use is limited by their high cost, low stability, and environmental toxicity. Oxygen is the most favorable electron acceptor in the case of MFCs, which reduces to water through a complicated oxygen reduction reaction (ORR). Carbon-based ORR catalysts possessing high surface area and good electrical conductivity improve the ORR kinetics by lowering the cathodic overpotential. Recently, a range of carbon-based materials have attracted attention for their exceptional ORR catalytic activity and high stability. Doping the carbon texture with a heteroatom improved their ORR activity remarkably through the favorable adsorption of oxygen and weaker molecular bonding. This review provides better insight into ORR catalysis for MFCs and the properties, performance, and applicability of various metal-free carbon-based electrocatalysts in MFCs to find the most appropriate cathodic catalyst for the practical applications. The approaches for improvement, key challenges, and future opportunities in this field are also explored. PMID:28029116

  6. Metal-Free Carbon-Based Materials: Promising Electrocatalysts for Oxygen Reduction Reaction in Microbial Fuel Cells.

    PubMed

    Sawant, Sandesh Y; Han, Thi Hiep; Cho, Moo Hwan

    2016-12-24

    Microbial fuel cells (MFCs) are a promising green approach for wastewater treatment with the simultaneous advantage of energy production. Among the various limiting factors, the cathodic limitation, with respect to performance and cost, is one of the main obstacles to the practical applications of MFCs. Despite the high performance of platinum and other metal-based cathodes, their practical use is limited by their high cost, low stability, and environmental toxicity. Oxygen is the most favorable electron acceptor in the case of MFCs, which reduces to water through a complicated oxygen reduction reaction (ORR). Carbon-based ORR catalysts possessing high surface area and good electrical conductivity improve the ORR kinetics by lowering the cathodic overpotential. Recently, a range of carbon-based materials have attracted attention for their exceptional ORR catalytic activity and high stability. Doping the carbon texture with a heteroatom improved their ORR activity remarkably through the favorable adsorption of oxygen and weaker molecular bonding. This review provides better insight into ORR catalysis for MFCs and the properties, performance, and applicability of various metal-free carbon-based electrocatalysts in MFCs to find the most appropriate cathodic catalyst for the practical applications. The approaches for improvement, key challenges, and future opportunities in this field are also explored.

  7. Graphitic mesoporous carbon based on aromatic polycondensation as catalyst support for oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Liu, Peng; Kong, Jiangrong; Liu, Yaru; Liu, Qicheng; Zhu, Hongze

    2015-03-01

    Mesoporous carbon is constructed by monolithic polyaromatic mesophase deriving from the hexane insoluble of coal-tar pitch. This carbon material exhibits spherical morphology and layered crystallite, and thereby can be graphitized at 900 °C without destroying the mesoporous structure. Electrochemical measurements indicate that graphitic mesoporous carbon (GMC) support not only improves the activity of Pt electrocatalyst to oxygen reduction reaction (ORR), but also shows higher corrosion resistance than commercial XC-72 carbon black in the acid cathode environment.

  8. Nitrogen-doped carbon-embedded TiO2 nanofibers as promising oxygen reduction reaction electrocatalysts

    NASA Astrophysics Data System (ADS)

    Hassen, D.; Shenashen, M. A.; El-Safty, S. A.; Selim, M. M.; Isago, H.; Elmarakbi, A.; El-Safty, A.; Yamaguchi, H.

    2016-10-01

    The development of inexpensive and effective electrocatalysts for oxygen reduction reaction (ORR) as a substitute for commercial Pt/C catalyst is an important issue in fuel cells. In this paper, we report on novel fabrication of self-supported nitrogen-doped carbon-supported titanium nanofibers (Nsbnd TiO2@C) and carbon-supported titanium (TiO2@C) electrocatalysts via a facile electrospinning route. The nitrogen atom integrates physically and homogenously into the entire carbon-titanium structure. We demonstrate the catalytic performance of Nsbnd TiO2@C and TiO2@C for ORR under alkaline conditions in comparison with Pt/C catalyst. The Nsbnd TiO2@C catalyst shows excellent ORR reactivity and durability. Interestingly, among all the catalysts used in this ORR, Nsbnd TiO2@C-0.75 exhibits remarkable competitive oxygen reduction activity in terms of current density and onset potential, as well as superior methanol tolerance. Such tolerance attributes to maximizing the diffusion of trigger pulse electrons during catalytic reactions because of enhanced electronic features. Results indicate that our fabrication strategy can provide an opportunity to produce a simple, efficient, cost-effective, and promising ORR electrocatalyst for practical applications in energy conversion and storage technologies.

  9. O2 and H2O2 transformation steps for the oxygen reduction reaction catalyzed by graphitic nitrogen-doped carbon nanotubes in acidic electrolyte from first principles calculations.

    PubMed

    Li, Yuhang; Zhong, Guoyu; Yu, Hao; Wang, Hongjuan; Peng, Feng

    2015-09-14

    It is highly challenging but extremely desirable to develop carbon catalysts with high oxygen reduction reaction (ORR) activity and stability in acidic medium for commercial application. In this paper, based on density functional theory (DFT) calculations with long range interaction correction and solvation effects, the elementary transformations of all the probable intermediates in the ORR and the hydrogen peroxide reduction reaction (HPRR) over graphitic nitrogen-doped carbon nanotubes (NCNTs) in acidic medium were evaluated, and it was found that all the rate determining steps are related to the bonding hydroxyl group because of the strong interaction between the hydroxyl group and carbon. Thus, it is hard for the direct four-electron ORR and the two-electron HPRR to proceed. Together with hydrogen peroxide disproportionation (HPD), a mixed mechanism for the ORR in acidic electrolyte was proposed, where the two-electron and three-electron ORRs and HPD dominate the electrode reaction. The experimental result for the ORR catalyzed by NCNTs in acidic electrolyte also well illustrated the rationality of the theoretical calculations. This study not only gives new insights into the effect of graphitic nitrogen doping on the ORR catalyzed by carbon, but also provides a guide to design carbon catalysts with high ORR activity in acidic electrolyte.

  10. Homogenous Electrocatalytic Oxygen Reduction Rates Correlate with Reaction Overpotential in Acidic Organic Solutions

    PubMed Central

    2016-01-01

    Improved electrocatalysts for the oxygen reduction reaction (ORR) are critical for the advancement of fuel cell technologies. Herein, we report a series of 11 soluble iron porphyrin ORR electrocatalysts that possess turnover frequencies (TOFs) from 3 s–1 to an unprecedented value of 2.2 × 106 s–1. These TOFs correlate with the ORR overpotential, which can be modulated by changing the E1/2 of the catalyst using different ancillary ligands, by changing the solvent and solution acidity, and by changing the catalyst’s protonation state. The overpotential is well-defined for these homogeneous electrocatalysts by the E1/2 of the catalyst and the proton activity of the solution. This is the first such correlation for homogeneous ORR electrocatalysis, and it demonstrates that the remarkably fast TOFs are a consequence of high overpotential. The correlation with overpotential is surprising since the turnover limiting steps involve oxygen binding and protonation, as opposed to turnover limiting electron transfer commonly found in Tafel analysis of heterogeneous ORR materials. Computational studies show that the free energies for oxygen binding to the catalyst and for protonation of the superoxide complex are in general linearly related to the catalyst E1/2, and that this is the origin of the overpotential correlations. This analysis thus provides detailed understanding of the ORR barriers. The best catalysts involve partial decoupling of the influence of the second coordination sphere from the properties of the metal center, which is suggested as new molecular design strategy to avoid the limitations of the traditional scaling relationships for these catalysts. PMID:27924314

  11. Current status, key challenges and its solutions in the design and development of graphene based ORR catalysts for the microbial fuel cell applications.

    PubMed

    Kannan, M V; Gnana Kumar, G

    2016-03-15

    Microbial fuel cells (MFC) are considered as the futuristic energy device that generates electricity from the catalytic degradation of biodegradable organic wastes using microbes, which exist in waste water. In MFCs, oxygen serves as a cathodic electron acceptor and oxygen reduction kinetics played a significant role in the determination of overall efficiency. A wide range of strategies have been developed for the preparation and substantial modification of oxygen reduction reaction (ORR) catalysts to improve the maximum volumetric power density of MFCs, in which the efforts on graphene based ORR catalysts are highly imperative. Although numerous research endeavors have been achieved in relation with the graphene based ORR catalysts applicable for MFCs, still their collective summary has not been developed, which hinders the acquirement of adequate knowledge on tuning the specific properties of said catalysts. The intension of this review is to outline the significant role of ORR catalysts, factors influencing the ORR activity, strategies behind the modifications of ORR catalysts and update the research efforts devoted on graphene based ORR catalysts. This review can be considered as a pertinent guide to understand the design and developmental strategies of competent graphene based ORR catalysts, which are not only applicable for MFCs but also for number of electrochemical applications. Copyright © 2015 Elsevier B.V. All rights reserved.

  12. Fe/Ni-N-CNFs electrochemical catalyst for oxygen reduction reaction/oxygen evolution reaction in alkaline media

    NASA Astrophysics Data System (ADS)

    Wang, Zhuang; Li, Mian; Fan, Liquan; Han, Jianan; Xiong, Yueping

    2017-04-01

    The novel of iron, nickel and nitrogen doped carbon nanofibers (Fe/Ni-N-CNFs) as bifunctional electrocatalysts are prepared by electrospinning technique. In alkaline media, the Fe/Ni-N-CNFs catalysts (especially for Fe1Ni1-N-CNFs) exhibit remarkable electrocatalytic performances of oxygen reduction reaction (ORR)/oxygen evolution reaction (OER). For ORR catalytic activity, Fe1Ni1-N-CNFs catalyst offers a higher onset potential of 0.903 V, a similar four-electron reaction pathway, and excellent stability. For OER catalytic activity, Fe1Ni1-N-CNFs catalyst possesses a lower onset potential of 1.528 V and a smaller charge transfer resistance of 48.14 Ω. The unparalleled catalytic activity of ORR and OER for the Fe1Ni1-N-CNFs is attributed to the 3D porous cross-linked microstructures of carbon nanofibers with Fe/Ni alloy, N dopant, and abundant M-Nx and NiOOH as catalytic active sites. Thus, Fe1Ni1-N-CNFs catalyst can be acted as one of the efficient and inexpensive catalysts of metal-air batteries.

  13. Tunable ternary (N, P, B)-doped porous nanocarbons and their catalytic properties for oxygen reduction reaction.

    PubMed

    Zhao, Shunyan; Liu, Juan; Li, Chuanxi; Ji, Wenbing; Yang, Manman; Huang, Hui; Liu, Yang; Kang, Zhenhui

    2014-12-24

    Heteroatom (N, P, and B)-codoped nanocarbons (NPBC) with nanoporous morphology are fabricated via a facile one-step pyrolysis method and exhibit good electrocatalytic activity, durability, and selectivity for the oxygen reduction reaction (ORR) in alkaline media. The ORR activity of NPBC is better than single- (nitrogen-doped carbon (NC)) or dual-doped (nitrogen and phosphorus codoped carbon (NPC) or nitrogen and boron codoped carbon (NBC)) catalysts in terms of onset potential and current density. This synthetic approach is efficient and suitable for large-scale fabrication of metal-free carbon-based catalysts.

  14. Single-Molecule Imaging of Iron-Phthalocyanine-Catalyzed Oxygen Reduction Reaction by in Situ Scanning Tunneling Microscopy.

    PubMed

    Gu, Jing-Ying; Cai, Zhen-Feng; Wang, Dong; Wan, Li-Jun

    2016-09-27

    We report herein an in situ electrochemical scanning tunneling microscopy (ECSTM) investigation of iron-phthalocyanine (FePc)-catalyzed oxygen reduction reaction (ORR). A highly ordered FePc adlayer is revealed on a Au(111) electrode. The center ions in the FePc adlayer show uniform high contrast in an oxygen-saturated electrolyte, which is attributed to the formation of an FePc-O2 complex. In situ STM results reveal the sharp contrast change upon shifting the electrode potential to trigger the ORR. Theoretical simulation has supplied further evidence for the contrast difference of the adsorbed FePc species.

  15. 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.

  16. The Role of OOH Binding Site and Pt Surface Structure on ORR Activities

    PubMed Central

    Jia, Qingying; Caldwell, Keegan; Ziegelbauer, Joseph M.; Kongkanand, Anusorn; Wagner, Frederick T.; Mukerjee, Sanjeev; Ramaker, David E.

    2015-01-01

    We present experimentally observed molecular adsorbate coverages (e.g., O(H), OOH and HOOH) on real operating dealloyed bimetallic PtMx (M = Ni or Co) catalysts under oxygen reduction reaction (ORR) conditions obtained using X-ray absorption near edge spectroscopy (XANES). The results reveal a complex Sabatier catalysis behavior and indicate the active ORR mechanism changes with Pt–O bond weakening from the O2 dissociative mechanism, to the peroxyl mechanism, and finally to the hydrogen peroxide mechanism. An important rearrangement of the OOH binding site, an intermediate in the ORR, enables facile H addition to OOH and faster O–O bond breaking on 111 faces at optimal Pt–O bonding strength, such as that occurring in dealloyed PtM core-shell nanoparticles. This rearrangement is identified by previous DFT calculations and confirmed from in situ measured OOH adsorption coverages during the ORR. The importance of surface structural effects and 111 ordered faces is confirmed by the higher specific ORR rates on solid core vs porous multi-core nanoparticles. PMID:26190857

  17. Pt3Re alloy nanoparticles as electrocatalysts for the oxygen reduction reaction

    SciTech Connect

    Raciti, David; Kubal, Joseph; Ma, Cheng; Barclay, Michael; Gonzalez, Matthew; Chi, Miaofang; Greeley, Jeffrey; More, Karren L.; Wang, Chao

    2015-12-25

    Development of renewable energy technologies requires advanced catalysts for efficient electrical-chemical energy conversion reactions. Here in this paper, we report the study of Pt-Re alloy nanoparticles as an electrocatalyst for the oxygen reduction reaction (ORR). An organic solution approach is developed to synthesize monodisperse and homogeneous Pt3Re alloy nanoparticles. Electrochemical studies show that these nanoparticles exhibit an improvement factor of 4 in catalytic activity for the ORR compared to commercial Pt catalysts of similar particle sizes. Fundamental understanding of the structure-property relationship is established by combining material characterization using X-ray spectroscopy and atomically resolved electron microscopy, as well as Density Functional Theory (DFT) calculations. Lastly, our work revealed that an electronic modification of the surface properties of Pt by subsurface Re (ligand effect) accounts for the catalytic enhancement.

  18. Pt3Re alloy nanoparticles as electrocatalysts for the oxygen reduction reaction

    DOE PAGES

    Raciti, David; Kubal, Joseph; Ma, Cheng; ...

    2015-12-25

    Development of renewable energy technologies requires advanced catalysts for efficient electrical-chemical energy conversion reactions. Here in this paper, we report the study of Pt-Re alloy nanoparticles as an electrocatalyst for the oxygen reduction reaction (ORR). An organic solution approach is developed to synthesize monodisperse and homogeneous Pt3Re alloy nanoparticles. Electrochemical studies show that these nanoparticles exhibit an improvement factor of 4 in catalytic activity for the ORR compared to commercial Pt catalysts of similar particle sizes. Fundamental understanding of the structure-property relationship is established by combining material characterization using X-ray spectroscopy and atomically resolved electron microscopy, as well as Densitymore » Functional Theory (DFT) calculations. Lastly, our work revealed that an electronic modification of the surface properties of Pt by subsurface Re (ligand effect) accounts for the catalytic enhancement.« less

  19. Trend in the Catalytic Activity of Transition Metals for the Oxygen Reduction Reaction by Lithium

    SciTech Connect

    Dathar, Gopi Krishna Phani; Shelton Jr, William Allison; Xu, Ye

    2012-01-01

    Periodic density functional theory (DFT) calculations indicate that the intrinsic activity of Au, Ag, Pt, Pd, Ir, and Ru for the oxygen reduction reaction by Li (Li-ORR) forms a volcano-like trend with respect to the adsorption energy of oxygen, with Pt and Pd being the most active. The trend is based on two mechanisms: the reduction of molecular O{sub 2} on Au and Ag and of atomic O on the remaining metals. Step edges are found to be more active for catalyzing the Li-ORR than close-packed surfaces. Our findings identify important considerations in the design of catalyst-promoted air cathodes for nonaqueous Li-air batteries.

  20. Trends in the Catalytic Activity of Transition Metals for the Oxygen Reduction Reaction by Lithium.

    PubMed

    Dathar, Gopi Krishna Phani; Shelton, William A; Xu, Ye

    2012-04-05

    Periodic density functional theory (DFT) calculations indicate that the intrinsic activity of Au, Ag, Pt, Pd, Ir, and Ru for the oxygen reduction reaction by Li (Li-ORR) forms a volcano-like trend with respect to the adsorption energy of oxygen, with Pt and Pd being the most active. The trend is based on two mechanisms: the reduction of molecular O2 on Au and Ag and of atomic O on the remaining metals. Step edges are found to be more active for catalyzing the Li-ORR than close-packed surfaces. Our findings identify important considerations in the design of catalyst-promoted air cathodes for nonaqueous Li-air batteries.

  1. N-doped carbon nanomaterials are durable catalysts for oxygen reduction reaction in acidic fuel cells.

    PubMed

    Shui, Jianglan; Wang, Min; Du, Feng; Dai, Liming

    2015-02-01

    The availability of low-cost, efficient, and durable catalysts for oxygen reduction reaction (ORR) is a prerequisite for commercialization of the fuel cell technology. Along with intensive research efforts of more than half a century in developing nonprecious metal catalysts (NPMCs) to replace the expensive and scarce platinum-based catalysts, a new class of carbon-based, low-cost, metal-free ORR catalysts was demonstrated to show superior ORR performance to commercial platinum catalysts, particularly in alkaline electrolytes. However, their large-scale practical application in more popular acidic polymer electrolyte membrane (PEM) fuel cells remained elusive because they are often found to be less effective in acidic electrolytes, and no attempt has been made for a single PEM cell test. We demonstrated that rationally designed, metal-free, nitrogen-doped carbon nanotubes and their graphene composites exhibited significantly better long-term operational stabilities and comparable gravimetric power densities with respect to the best NPMC in acidic PEM cells. This work represents a major breakthrough in removing the bottlenecks to translate low-cost, metal-free, carbon-based ORR catalysts to commercial reality, and opens avenues for clean energy generation from affordable and durable fuel cells.

  2. N-doped carbon nanomaterials are durable catalysts for oxygen reduction reaction in acidic fuel cells

    PubMed Central

    Shui, Jianglan; Wang, Min; Du, Feng; Dai, Liming

    2015-01-01

    The availability of low-cost, efficient, and durable catalysts for oxygen reduction reaction (ORR) is a prerequisite for commercialization of the fuel cell technology. Along with intensive research efforts of more than half a century in developing nonprecious metal catalysts (NPMCs) to replace the expensive and scarce platinum-based catalysts, a new class of carbon-based, low-cost, metal-free ORR catalysts was demonstrated to show superior ORR performance to commercial platinum catalysts, particularly in alkaline electrolytes. However, their large-scale practical application in more popular acidic polymer electrolyte membrane (PEM) fuel cells remained elusive because they are often found to be less effective in acidic electrolytes, and no attempt has been made for a single PEM cell test. We demonstrated that rationally designed, metal-free, nitrogen-doped carbon nanotubes and their graphene composites exhibited significantly better long-term operational stabilities and comparable gravimetric power densities with respect to the best NPMC in acidic PEM cells. This work represents a major breakthrough in removing the bottlenecks to translate low-cost, metal-free, carbon-based ORR catalysts to commercial reality, and opens avenues for clean energy generation from affordable and durable fuel cells. PMID:26601132

  3. Electrocatalytic activity of various types of h-BN for the oxygen reduction reaction.

    PubMed

    Elumalai, Ganesan; Noguchi, Hidenori; Uosaki, Kohei

    2014-07-21

    The electrocatalytic activities of various types of h-BN, i.e., spin coated BN nanotubes (BNNTs) and BN nanosheets (BNNSs) and sputter deposited BN, on Au electrodes as well as those of BNNS modified glassy carbon (GC) and Pt electrodes for the oxygen reduction reaction (ORR) were examined in O2 saturated 0.5 M H2SO4 solution based on the theoretical prediction that monolayered BN on a metal substrate may act as an electrocatalyst for ORR even though bulk BN is an insulator with a wide band gap. The overpotential for ORR at Au electrodes was reduced by ca. 100, ca. 270, and ca. 150 mV by spin coating of the dispersion of BNNT and liquid exfoliated BNNS, and sputter deposition of BN, respectively, proving the theoretical prediction. On the other hand, no change in the overpotential was observed at the glassy carbon electrode with BNNS modification and the overpotential even increased at the Pt electrode, suggesting that the interaction between BN and Au plays an important role in BN becoming ORR active.

  4. Co-N-Doped Mesoporous Carbon Hollow Spheres as Highly Efficient Electrocatalysts for Oxygen Reduction Reaction.

    PubMed

    Hu, Feng; Yang, Hongchao; Wang, Changhong; Zhang, Yejun; Lu, Huan; Wang, Qiangbin

    2017-01-01

    Rational design of cost-effective, nonprecious metal-based catalysts with desirable oxygen reduction reaction (ORR) performance is extremely important for future fuel cell commercialization, etc. Herein, a new type of ORR catalyst of Co-N-doped mesoporous carbon hollow sphere (Co-N-mC) was developed by pyrolysis from elaborately fabricated polystyrene@polydopamine-Co precursors. The obtained catalysts with active Co sites distributed in highly graphitized mesoporous N-doped carbon hollow spheres exhibited outstanding ORR activity with an onset potential of 0.940 V, a half-wave potential of 0.851 V, and a small Tafel slope of 45 mV decade(-1) in 0.1 m KOH solution, which was comparable to that of the Pt/C catalyst (20%, Alfa). More importantly, they showed superior durability with little current decline (less than 4%) in the chronoamperometric evaluation over 60 000 s. These features make the Co-N-mC one of the best nonprecious-metal catalysts to date for ORR in alkaline condition. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Graphene-based transition metal oxide nanocomposites for the oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Sun, Meng; Liu, Huijuan; Liu, Yang; Qu, Jiuhui; Li, Jinghong

    2015-01-01

    The development of low cost, durable and efficient nanocatalysts to substitute expensive and rare noble metals (e.g. Pt, Au and Pd) in overcoming the sluggish kinetic process of the oxygen reduction reaction (ORR) is essential to satisfy the demand for sustainable energy conversion and storage in the future. Graphene based transition metal oxide nanocomposites have extensively been proven to be a type of promising highly efficient and economic nanocatalyst for optimizing the ORR to solve the world-wide energy crisis. Synthesized nanocomposites exhibit synergetic advantages and avoid the respective disadvantages. In this feature article, we concentrate on the recent leading works of different categories of introduced transition metal oxides on graphene: from the commonly-used classes (FeOx, MnOx, and CoOx) to some rare and heat-studied issues (TiOx, NiCoOx and Co-MnOx). Moreover, the morphologies of the supported oxides on graphene with various dimensional nanostructures, such as one dimensional nanocrystals, two dimensional nanosheets/nanoplates and some special multidimensional frameworks are further reviewed. The strategies used to synthesize and characterize these well-designed nanocomposites and their superior properties for the ORR compared to the traditional catalysts are carefully summarized. This work aims to highlight the meaning of the multiphase establishment of graphene-based transition metal oxide nanocomposites and its structural-dependent ORR performance and mechanisms.

  6. Co₃O₄ nanocrystals on graphene as a synergistic catalyst for oxygen reduction reaction.

    PubMed

    Liang, Yongye; Li, Yanguang; Wang, Hailiang; Zhou, Jigang; Wang, Jian; Regier, Tom; Dai, Hongjie

    2011-10-01

    Catalysts for oxygen reduction and evolution reactions are at the heart of key renewable-energy technologies including fuel cells and water splitting. Despite tremendous efforts, developing oxygen electrode catalysts with high activity at low cost remains a great challenge. Here, we report a hybrid material consisting of Co₃O₄ nanocrystals grown on reduced graphene oxide as a high-performance bi-functional catalyst for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Although Co₃O₄ or graphene oxide alone has little catalytic activity, their hybrid exhibits an unexpected, surprisingly high ORR activity that is further enhanced by nitrogen doping of graphene. The Co₃O₄/N-doped graphene hybrid exhibits similar catalytic activity but superior stability to Pt in alkaline solutions. The same hybrid is also highly active for OER, making it a high-performance non-precious metal-based bi-catalyst for both ORR and OER. The unusual catalytic activity arises from synergetic chemical coupling effects between Co₃O₄ and graphene.

  7. The Se effect on the oxygen reduction reaction on the Se/Ru electro-catalysts. Insight from first principles.

    NASA Astrophysics Data System (ADS)

    Stolbov, Sergey

    2011-03-01

    Rational search for new efficient low-cost electrocatalysts for oxygen reduction reaction (ORR) on the hydrogen fuel cell cathodes focuses on varying the material composition to modify the local densities of electronic states (LDOS) of the surface atoms, in order to tune the surface-adsorbate electronic state hybridization and hence binding energies of the ORR intermediates. My calculation results for the Se/Ru electrocatalysts suggest an alternative way of tuning the binding energies. The Se atoms deposited on the Ru surface are found not to change Ru LDOS noticeably, however, Se atoms are negatively charged due to ionic Se-Ru bonding. As a result, they repeal electrostatically the adsorbed negatively charged O and OH intermediates, and this way reduce their binding energies. Since for the Ru case, reduction of the O and OH binding energies makes ORR energetically favorable, Se deposition dramatically improve the ORR rate on Ru. The ORR rate can thus be enhanced by changing coverage of the deposited halchogen atoms or by tuning the charge transfer to those by modifying the substrate composition.

  8. A full understanding of oxygen reduction reaction mechanism on Au(1 1 1) surface

    NASA Astrophysics Data System (ADS)

    Yang, Yang; Dai, Changqing; Fisher, Adrian; Shen, Yanchun; Cheng, Daojian

    2017-09-01

    Oxygen reduction and hydrogen peroxide reduction are technologically important reactions in energy-conversion devices. In this work, a full understanding of oxygen reduction reaction (ORR) mechanism on Au(1 1 1) surface is investigated by density functional theory (DFT) calculations, including the reaction mechanisms of O2 dissociation, OOH dissociation, and H2O2 dissociation. Among these ORR mechanisms on Au(1 1 1), the activation energy of \\text{O}2* hydrogenation reaction is much lower than that of \\text{O}2* dissociation, indicating that \\text{O}2* hydrogenation reaction is more appropriate at the first step than \\text{O}2* dissociation. In the following, H2O2 can be formed with the lower activation energy compared with the OOH dissociation reaction, and finally H2O2 could be generated as a detectable product due to the high activation energy of H2O2 dissociation reaction. Furthermore, the potential dependent free energy study suggests that the H2O2 formation is thermodynamically favorable up to 0.4 V on Au(1 1 1), reducing the overpotential for 2e - ORR process. And the elementary step of first H2O formation becomes non-spontaneous at 0.4 V, indicating the difficulty of 4e - reduction pathway. Our DFT calculations show that H2O2 can be generated on Au(1 1 1) and the first electron transfer is the rate determining step. Our results show that gold surface could be used as a good catalyst for small-scale manufacture and on-site production of H2O2.

  9. A full understanding of oxygen reduction reaction mechanism on Au(1 1 1) surface.

    PubMed

    Yang, Yang; Dai, Changqing; Fisher, Adrian; Shen, Yanchun; Cheng, Daojian

    2017-09-13

    Oxygen reduction and hydrogen peroxide reduction are technologically important reactions in energy-conversion devices. In this work, a full understanding of oxygen reduction reaction (ORR) mechanism on Au(1 1 1) surface is investigated by density functional theory (DFT) calculations, including the reaction mechanisms of O2 dissociation, OOH dissociation, and H2O2 dissociation. Among these ORR mechanisms on Au(1 1 1), the activation energy of [Formula: see text] hydrogenation reaction is much lower than that of [Formula: see text] dissociation, indicating that [Formula: see text] hydrogenation reaction is more appropriate at the first step than [Formula: see text] dissociation. In the following, H2O2 can be formed with the lower activation energy compared with the OOH dissociation reaction, and finally H2O2 could be generated as a detectable product due to the high activation energy of H2O2 dissociation reaction. Furthermore, the potential dependent free energy study suggests that the H2O2 formation is thermodynamically favorable up to 0.4 V on Au(1 1 1), reducing the overpotential for 2e (-) ORR process. And the elementary step of first H2O formation becomes non-spontaneous at 0.4 V, indicating the difficulty of 4e (-) reduction pathway. Our DFT calculations show that H2O2 can be generated on Au(1 1 1) and the first electron transfer is the rate determining step. Our results show that gold surface could be used as a good catalyst for small-scale manufacture and on-site production of H2O2.

  10. Oxygen reduction reaction catalyzed by platinum nanonetwork prepared by template free one step synthesis for polymer electrolyte membrane fuel cells

    SciTech Connect

    Narayanamoorthy, B.; Kumar, B.V.V.S. Pavan; Eswaramoorthy, M.; Balaji, S.

    2014-07-01

    Highlights: • Supportless Pt nanonetwork (Pt NN) synthesized by novel template free one step method as per our earlier reported procedure. • Electrocatalytic activity of Pt NN studied taking oxygen reduction reaction in acid medium. • Kinetic and thermodynamic parameters were deduced under hydrodynamic conditions. • ORR mechanistic pathway was proposed based on kinetic rate constants. • ADT analysis found enhanced stability (5000 cycles) for Pt NN than Pt NN/VC and reported Pt/C. - Abstract: The reduction reaction of molecular oxygen (ORR) was investigated using supportless Pt nanonetwork (Pt NN) electrocatalyst in sulfuric acid medium. Pt NN was prepared by template free borohydride reduction. The transmission electron microscope images revealed a network like nano-architecture having an average cluster size of 30 nm. The electrochemical characterization of supportless and Vulcan carbon supported Pt NN (Pt NN/VC) was carried out using rotating disc and ring disc electrodes at various temperatures. Kinetic and thermodynamic parameters were estimated under hydrodynamic conditions and compared with Pt NN/VC and reported Pt/C catalysts. The accelerated durability test revealed that supportless Pt NN is quite stable for 5000 potential cycles with 22% reduction in electrochemical surface area (ECSA). While the initial limiting current density has in fact increased by 11.6%, whereas Pt NN/VC suffered nearly 55% loss in ECSA and 13% loss in limiting current density confirming an enhanced stability of supportless Pt NN morphology for ORR compared to conventional Pt/C ORR catalysts in acid medium.

  11. Ni- and Mn-Promoted Mesoporous Co3O4: A Stable Bifunctional Catalyst with Surface-Structure-Dependent Activity for Oxygen Reduction Reaction and Oxygen Evolution Reaction.

    PubMed

    Song, Wenqiao; Ren, Zheng; Chen, Sheng-Yu; Meng, Yongtao; Biswas, Sourav; Nandi, Partha; Elsen, Heather A; Gao, Pu-Xian; Suib, Steven L

    2016-08-17

    Efficient bifunctional catalysts for electrochemical oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are highly desirable due to their wide applications in fuel cells and rechargeable metal air batteries. However, the development of nonprecious metal catalysts with comparable activities to noble metals is still challenging. Here we report a one-step wet-chemical synthesis of Ni-/Mn-promoted mesoporous cobalt oxides through an inverse micelle process. Various characterization techniques including powder X-ray diffraction (PXRD), N2 sorption, transmission electron microscopy (TEM), and scanning electron microscopy (SEM) confirm the successful incorporation of Ni and Mn leading to the formation of Co-Ni(Mn)-O solid solutions with retained mesoporosity. Among these catalysts, cobalt oxide with 5% Ni doping demonstrates promising activities for both ORR and OER, with an overpotential of 399 mV for ORR (at -3 mA/cm(2)) and 381 mV (at 10 mA/cm(2)) for OER. Furthermore, it shows better durability than precious metals featuring little activity decay throughout 24 h continuous operation. Analyses of cyclic voltammetry (CV), X-ray photoelectron spectroscopy (XPS), Raman, and O2-temperature-programmed desorption (O2-TPD) reveal that redox activity of Co(3+) to Co(4+) is crucial for OER performance, while the population of surface oxygen vacancies and surface area determine ORR activities. The comprehensive investigation of the intrinsic active sites for ORR and OER by correlating different physicochemical properties to the electrochemical activities is believed to provide important insight toward the rational design of high-performance electrocatalysts for ORR and OER reactions.

  12. ORR Deer Hunt Monitoring Program

    SciTech Connect

    Scofield, P.A.; Teasley, N.A.

    1999-09-01

    The primary purpose for the initiation of deer hunts on the Oak Ridge Reservation (ORR) was deer population control to reduce collisions with vehicles and maintain a healthy herd and habitat. As of 1997, thirteen annual deer hunts have been conducted on the ORR. The deer hunt monitoring program (DHMP) has two components -- a field screening monitoring program and a confirmatory laboratory analysis program of both retained and randomly selected released deer samples.

  13. Cobalt-Based Active Species Molecularly Immobilized on Carbon Nanotubes for the Oxygen Reduction Reaction.

    PubMed

    Kim, Sujin; Jang, Dawoon; Lim, Joonwon; Oh, Junghoon; Kim, Sang Ouk; Park, Sungjin

    2017-09-11

    Hybrid systems in which molecule-based active species are combined with nanoscale materials may offer valuable routes to enhance catalytic performances for electrocatalytic reactions. The development of rationally designed, cost-effective, efficient catalysts for the oxygen reduction reaction (ORR) is a crucial challenge for applications in fuel cells and metal-air batteries. A new hybrid ORR catalyst has been synthesized through a well-defined reaction between Co-based organometallic molecules and N-doped multiwalled carbon nanotubes (MWCNTs) at room temperature. The hybrid ORR catalyst shows excellent catalytic performance with an onset potential of 0.95 V [vs. the reversible hydrogen electrode (RHE)], superior durability, and good methanol tolerance. Chemical and structural characterization after many reaction cycles reveals that the Co-based organometallic species maintained the original structure of cobalt(II) acetylacetonate with coordination to the heteroatoms of the MWCNTs. A thorough electrochemical investigation indicates that the major catalytically active site is Co-O4 -NCNT . © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Origin of high oxygen reduction reaction activity of Pt12 and strategy to obtain better catalyst using sub-nanosized Pt-alloy clusters

    PubMed Central

    Miyazaki, Kasumi; Mori, Hirotoshi

    2017-01-01

    In the present study, methods to enhance the oxygen reduction reaction (ORR) activity of sub-nanosized Pt clusters were investigated in a theoretical manner. Using ab initio molecular dynamics and Monte Carlo simulations based on density functional theory, we have succeeded in determining the origin of the superior ORR activity of Pt12 compared to that of Pt13. That is, it was clarified that the electronic structure of Pt12 fluctuates to a greater extent compared to that of Pt13, which leads to stronger resistance against catalyst poisoning by O/OH. Based on this conclusion, a set of sub-nanosized Pt-alloy clusters was also explored to find catalysts with better ORR activities and lower financial costs. It was suggested that Ga4Pt8, Ge4Pt8, and Sn4Pt8 would be good candidates for ORR catalysts. PMID:28349985

  15. Hollow spherical La0.8Sr0.2MnO3 perovskite oxide with enhanced catalytic activities for the oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Lu, Fanliang; Sui, Jing; Su, Jianmin; Jin, Chao; Shen, Ming; Yang, Ruizhi

    2014-12-01

    A hollow spherical La0.8Sr0.2MnO3 (HS-LSM) perovskite oxide has been prepared using a new carbonate-template route, and characterized by XRD, SEM and TEM. SEM and TEM results show that the pre-prepared oxides consist of porous microspheres composed of submicrometer-sized subunits with a secondary particle diameter of ∼20-50 nm. The catalytic activity of the oxide for the oxygen reduction reaction (ORR) in 0.1 M KOH solution has been studied using a rotating ring-disk electrode (RRDE). In the ORR tests, a maximum cathodic current density of 6.4 mA cm-2 at -0.9 V (vs. Ag/AgCl) with 2500 rpm has been obtained, and the ORR mainly favors a direct four-electron pathway. The chronoamperometric test shows that the HS-LSM exhibits excellent stability for the ORR.

  16. Origin of high oxygen reduction reaction activity of Pt12 and strategy to obtain better catalyst using sub-nanosized Pt-alloy clusters

    NASA Astrophysics Data System (ADS)

    Miyazaki, Kasumi; Mori, Hirotoshi

    2017-03-01

    In the present study, methods to enhance the oxygen reduction reaction (ORR) activity of sub-nanosized Pt clusters were investigated in a theoretical manner. Using ab initio molecular dynamics and Monte Carlo simulations based on density functional theory, we have succeeded in determining the origin of the superior ORR activity of Pt12 compared to that of Pt13. That is, it was clarified that the electronic structure of Pt12 fluctuates to a greater extent compared to that of Pt13, which leads to stronger resistance against catalyst poisoning by O/OH. Based on this conclusion, a set of sub-nanosized Pt-alloy clusters was also explored to find catalysts with better ORR activities and lower financial costs. It was suggested that Ga4Pt8, Ge4Pt8, and Sn4Pt8 would be good candidates for ORR catalysts.

  17. Linking structure to function: The search for active sites in non-platinum group metal oxygen reduction reaction catalysts

    DOE PAGES

    Holby, Edward F.; Zelenay, Piotr

    2016-05-17

    Atomic-scale structures of oxygen reduction reaction (ORR) active sites in non-platinum group metal (non-PGM) catalysts, made from pyrolysis of carbon, nitrogen, and transition-metal (TM) precursors have been the subject of continuing discussion in the fuel cell electrocatalysis research community. We found that quantum chemical modeling is a path forward for understanding of these materials and how they catalyze the ORR. Here, we demonstrate through literature examples of how such modeling can be used to better understand non-PGM ORR active site relative stability and activity and how such efforts can also aid in the interpretation of experimental signatures produced by thesemore » materials.« less

  18. The strong catalytic effect of Pb(II) on the oxygen reduction reaction on 5 nm gold nanoparticles.

    PubMed

    Wang, Ying; Laborda, Eduardo; Plowman, Blake J; Tschulik, Kristina; Ward, Kristopher R; Palgrave, Robert G; Damm, Christine; Compton, Richard G

    2014-02-21

    Citrate-capped gold nanoparticles (AuNPs) of 5 nm in diameter are synthesized via wet chemistry and deposited on a glassy carbon electrode through electrophoresis. The kinetics of the oxygen reduction reaction (ORR) on the modified electrode is determined quantitatively in oxygen-saturated 0.5 M sulphuric acid solution by modelling the cathode as an array of interactive nanoelectrodes. Quantitative analysis of the cyclic voltammetry shows that no apparent ORR electrocatalysis takes place, the kinetics on AuNPs being effectively the same as on bulk gold. Contrasting with the above, a strong ORR catalysis is found when Pb(2+) is added to the oxygen saturated solution or when the modified electrode is cycled in lead alkaline solution such that lead dioxide is repeatedly electrodeposited and stripped off on the nanoparticles. In both cases, the underpotential deposition of lead on the gold nanoparticles is found to be related to the catalysis.

  19. Cobalt monolayer islands on Ag(111) for ORR catalysis.

    PubMed

    Loglio, Francesca; Lastraioli, Elisa; Bianchini, Claudio; Fontanesi, Claudio; Innocenti, Massimo; Lavacchi, Alessandro; Vizza, Francesco; Foresti, Maria Luisa

    2011-08-22

    The design of a catalyst for one of the most important electrocatalytic reactions, the oxygen reduction reaction (ORR), was done following the most recent guidelines of theoretical studies on this topic. Aim of this work was to achieve a synergic effect of two different metals acting on different steps of the ORR. The catalytic activity of Ag, already known and characterized, was enhanced by the presence of a monolayer of cobalt subdivided into nanosized islands. To obtain such a controlled nanostructure, a novel method utilizing self-assembled monolayers (SAMs) as templates was employed. In a recent study, we were able to perform a confined electrodeposition of cobalt onto Ag(111) in a template formed by selectively desorbing a short-chain thiol (3-mercaptopropionic acid, MPA) from binary SAMs using 1-dodecanthiols (DDT). This method allows for an excellent control of the morphology of the deposit by varying the molar ratio of the two thiols. Because cobalt does not deposit on silver at an underpotential, the alternative approach of surface limited redox replacement (SLRR) was used. This method, recently developed by Adžić et al., consists of the use of a monolayer of a third metal, which can be deposited at an underpotential, as a template for the spontaneous deposition of a more noble metal. Herein, we choose zinc as template for the deposition of cobalt. Ag(111) crystals were covered by monolayer islands consisting of cobalt, with the surface atomic ratios ranging from 12 to 39% for cobalt. The catalytic activity of such samples towards ORR was evaluated and the best improvement in activity was found to be that of the sample with a cobalt percentage of approximately 30% with respect to the bare silver, which is in good agreement with theoretical hypotheses.

  20. 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.

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

    DOE PAGES

    Christ, J. M.; Neyerlin, K. C.; Wang, H.; ...

    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

  2. In-plane graphene/boron-nitride heterostructures as an efficient metal-free electrocatalyst for the oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Sun, Qiao; Sun, Caixia; Du, Aijun; Dou, Shixue; Li, Zhen

    2016-07-01

    Exploiting metal-free catalysts for the oxygen reduction reaction (ORR) and understanding their catalytic mechanisms are vital for the development of fuel cells (FCs). Our study has demonstrated that in-plane heterostructures of graphene and boron nitride (G/BN) can serve as an efficient metal-free catalyst for the ORR, in which the C-N interfaces of G/BN heterostructures act as reactive sites. The formation of water at the heterointerface is both energetically and kinetically favorable via a four-electron pathway. Moreover, the water formed can be easily released from the heterointerface, and the catalytically active sites can be regenerated for the next cycle. Since G/BN heterostructures with controlled domain sizes have been successfully synthesized in recent reports (e.g. Nat. Nanotechnol., 2013, 8, 119), our results highlight the great potential of such heterostructures as a promising metal-free catalyst for the ORR in FCs.Exploiting metal-free catalysts for the oxygen reduction reaction (ORR) and understanding their catalytic mechanisms are vital for the development of fuel cells (FCs). Our study has demonstrated that in-plane heterostructures of graphene and boron nitride (G/BN) can serve as an efficient metal-free catalyst for the ORR, in which the C-N interfaces of G/BN heterostructures act as reactive sites. The formation of water at the heterointerface is both energetically and kinetically favorable via a four-electron pathway. Moreover, the water formed can be easily released from the heterointerface, and the catalytically active sites can be regenerated for the next cycle. Since G/BN heterostructures with controlled domain sizes have been successfully synthesized in recent reports (e.g. Nat. Nanotechnol., 2013, 8, 119), our results highlight the great potential of such heterostructures as a promising metal-free catalyst for the ORR in FCs. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr03288e

  3. Three-Dimensional Phosphorus-Doped Graphitic-C3N4 Self-Assembly with NH2-Functionalized Carbon Composite Materials for Enhanced Oxygen Reduction Reaction.

    PubMed

    Qiu, Yang; Xin, Le; Jia, Fan; Xie, Jian; Li, Wenzhen

    2016-12-06

    Oxygen reduction reaction (ORR) is the major reaction that occurs at the cathodes of fuel cells and metal-air batteries. Development of inexpensive, active, and durable heteroatom doped carbon-based ORR catalysts can lead to significant cost reduction of these electrochemical energy devices, which therefore has recently attracted enormous research attentions. This work reports a three-dimensional porous composite (P-g-C3N4@NH2-CB) for the highly efficient ORR catalyst. P-g-C3N4@NH2-CB was prepared by mixing phosphorus-doped graphitic carbon nitride nanosheets (P-g-C3N4 NSs) with NH2-functionalized carbon black (NH2-CB) via a novel self-assembly approach. The NH2-CB was rationally chosen as the spacer that enables the self-assembled with the P-g-C3N4 NSs driven by the electrostatic interaction. The intercalation of NH2-CB induces the transformation of 2-D P-g-C3N4 NSs into a 3-D composites material of higher surface area, thereby exposing more ORR active sites. The P-g-C3N4@NH2-CB exhibited a remarkable ORR activity with an electron transfer number of 3.83 and Tafel slope of 89 mV dec(-1) in alkaline electrolyte, which is comparable to the ORR performance on Pt/Vulcan XC-72. It is found that the incorporated P atoms as well as employing NH2-CB spacer not only reduces the overpotential of ORR, but also enhances the ORR activity of carbon nitride-based materials, owing to the synergistic effect between P and N in tri-s-triazine rings of carbon nitrides and the optimum interaction between the oppositely charged P-g-C3N4 and NH2-CB.

  4. Functional links between Pt single crystal morphology and nanoparticles with different size and shape: the oxygen reduction reaction case

    SciTech Connect

    Li, Dongguo; Wang, Chao; Strmcnik, Dusan S.; Tripkovic, Dusan V.; Sun, Xiaolian; Kang, Yijin; Chi, Miaofang; Snyder, Joshua D.; van der Vliet, Dennis; Tsai, Yifen; Stamenkovic, Vojislav R.; Sun, Shouheng; Markovic, Nenad M.

    2014-01-01

    Design of active and stable Pt-based nanoscale electrocatalysts for the oxygen reduction reaction (ORR) will be the key to improving the efficiency of fuel cells that are needed to deliver reliable, affordable and environmentally friendly energy. Here, by exploring the ORR on Pt single crystals, cubo-octahedral (polyhedral) Pt NPs with different sizes (ranging from 2 to 7 nm), and 7–8 nm Pt NPs with different shapes (cubo-octahedral vs. cube vs. octahedral), we presented a surface science approach capable of rationalizing, and ultimately understanding, fundamental relationships between stability of Pt NPs and activity of the ORR in acidic media. By exploring the potential induced dissolution/re-deposition of Pt between 0.05 and 1.3 V, we found that concomitant variations in morphology of Pt(111) and Pt(100) lead to narrowing differences in activity between Pt single crystal surfaces. We also found that regardless of an initial size or shape, NPs are metastable and easily evolve to thermodynamically equilibrated shape and size with very similar activity for the ORR. We concluded that while initially clearly observed, the particle size and shape effects diminish as the particles age to the point that it may appear that the ORR depends neither on the particle size nor particle shape.

  5. 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

  6. Aligned carbon nanotube with electro-catalytic activity for oxygen reduction reaction

    DOEpatents

    Liu, Di-Jia; Yang, Junbing; Wang, Xiaoping

    2010-08-03

    A catalyst for an electro-chemical oxygen reduction reaction (ORR) of a bundle of longitudinally aligned carbon nanotubes having a catalytically active transition metal incorporated longitudinally in said nanotubes. A method of making an electro-chemical catalyst for an oxygen reduction reaction (ORR) having a bundle of longitudinally aligned carbon nanotubes with a catalytically active transition metal incorporated throughout the nanotubes, where a substrate is in a first reaction zone, and a combination selected from one or more of a hydrocarbon and an organometallic compound containing an catalytically active transition metal and a nitrogen containing compound and an inert gas and a reducing gas is introduced into the first reaction zone which is maintained at a first reaction temperature for a time sufficient to vaporize material therein. The vaporized material is then introduced to a second reaction zone maintained at a second reaction temperature for a time sufficient to grow longitudinally aligned carbon nanotubes over the substrate with a catalytically active transition metal incorporated throughout the nanotubes.

  7. Ammonia-treated Ordered Mesoporous Carbons as Catalytic Materials for Oxygen Reduction Reaction

    SciTech Connect

    Wang, Xiqing; Lee, Je Seung; Zhu, Qing; Liu, Jun; Wang, Yong; Dai, Sheng

    2010-04-13

    Polymer electrolyte membrane fuel cells (PEMFCs) have been considered as promising alternative power sources for many mobile and stationary applications. Compared to the fast hydrogen oxidation at the anode, the sluggish oxygen reduction reaction (ORR) at the cathode requires high-performance catalysts. Currently, platium (Pt) nanoparticles supported on high surface area carbons remain the best catalysts for ORR. However, both instability and high cost of Pt-based catalysts represent two main obstacles limiting the commercial applications of PEMFCs. The instability of supported Pt catalysts is mainly due to the corrosion of carbon support under operation conditions and the agglomation and detachment of Pt particles, leading to a decrease in catalytic surface areas. Development of corrosion resistant supports and enhancement of the interactions between Pt and supports are two strategies to improve the cathode long-term activity.

  8. 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

  9. A facile synthesis of highly stable modified carbon nanotubes as efficient oxygen reduction reaction catalysts

    NASA Astrophysics Data System (ADS)

    Stenmark, Theodore Axel

    Proton Exchange Membrane Fuel Cell (PEMFC) technology is an exciting alternative energy prospect, especially in the field of transportation. PEMFCs are three times as efficient as internal combustion (IC) engines and emit only water as a byproduct. The latter point is especially important in a day and age when climate change is upon us. However, platinum required to catalyze the sluggish oxygen reduction reaction (ORR) which takes place on the cathode of the PEMFC has rendered fuel cell automobiles economically unviable. Therefore, the pursuit of an inexpensive replacement for platinum has become an active research area. Herein, a facile synthetic process for modified carbon nanotubes for ORR catalysis is described. These nanotubes display catalytic activity via rotating disc electrode (RDE) analysis which, in some cases, equals that of a Pt/C standard.

  10. Electrocatalytic performances of N-doped graphene with anchored iridium species in oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Choi, Kwangrok; Lee, Seungjun; Shim, Yeonjun; Oh, Junghoon; Kim, Sujin; Park, Sungjin

    2015-09-01

    Development of new systems with high catalytic performances in the oxygen reduction reaction (ORR) for practical applications in fuel cells and metal-air batteries is a challenge. We develop a one-pot solution method for producing a novel hybrid material consisting of Ir species anchored on N-doped graphene. The hybrid is synthesized by reacting graphene oxide with IrCl3 · xH2O in dimethylformamide under reflux. Chemical and structural analyses confirm the attachment of Ir atoms to the N and O atoms of the N-doped graphene-based materials. The hybrid shows a good electrocatalytic performance for the ORR in alkaline media, with an onset potential of 0.88 V (versus the reversible hydrogen electrode), high long-term durability, and good tolerance for methanol poisoning.

  11. Sewage sludge biochar as an efficient catalyst for oxygen reduction reaction in an microbial fuel cell.

    PubMed

    Yuan, Yong; Yuan, Tian; Wang, Dingmei; Tang, Jiahuan; Zhou, Shungui

    2013-09-01

    Sewage sludge (SS) biochars have been prepared under an inert atmosphere at different temperatures. Morphologic and chemical analyses reveal that the surface of the biochar carbonized at 900°C (SS900) has more abundant micropores, and higher nitrogen and iron contents as compared to those carbonized at 500 (SS500) and 700°C (SS700). The electrochemical analyses display that the prepared biochars are active for catalyzing oxygen reduction reaction (ORR). However, more positive peak potential and larger peak current of ORR are found using the SS900 as compared to the SS500 and SS700. In MFCs, the maximum power density of 500±17 mW m(-2) was obtained from the SS900 cathode, which is comparable to the Pt cathode. The proposed cathode exhibited good stability and great tolerance to methanol. Given these results, it is expected that the SS-derived biochar cathode can find application in fuel cell systems.

  12. A novel nitrogen-containing electrocatalyst for oxygen reduction reaction from blood protein pyrolysis

    NASA Astrophysics Data System (ADS)

    Guo, Chao-Zhong; Chen, Chang-Guo; Luo, Zhong-Li

    2014-01-01

    We report a new strategy to design carbon-based electrocatalysts containing nitrogen through the co-pyrolysis of blood protein and carbon black support. The results show that the nitrogen in electrocatalysts is primarily in the form of pyridinic- and pyrrolic-type nitrogen species. High-temperature pyrolysis processes can transfer a significant amount of pyridinic-N to pyrrolic-N. The electrocatalyst containing a higher amount of the pyrrolic-N configuration exhibits better electrocatalytic activity towards oxygen reduction reaction in terms of onset potential, half-wave potential, and limited current density. It is suggested that the pyrrolic-N configuration may be the electrocatalytically active site and may be responsible for the enhanced ORR performance in alkaline media. The carbon black support also plays an important role in the pyrolysis process, improving the ORR catalytic activity.

  13. 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.

  14. Graphene supported non-precious metal-macrocycle catalysts for oxygen reduction reaction in fuel cells

    NASA Astrophysics Data System (ADS)

    Choi, Hyun-Jung; Ashok Kumar, Nanjundan; Baek, Jong-Beom

    2015-04-01

    Fuel cells are promising alternative energy devices owing to their high efficiency and eco-friendliness. While platinum is generally used as a catalyst for the oxygen reduction reaction (ORR) in a typical fuel cell, limited reserves and prohibitively high costs limit its future use. The development of non-precious and durable metal catalysts is being constantly conceived. Graphene has been widely used as a substrate for metal catalysts due to its unique properties, thus improving stability and ORR activities. In this feature, we present an overview on the electrochemical characteristics of graphene supported non-precious metal containing macrocycle catalysts that include metal porphyrin and phthalocyanine derivatives. Suggested research and future development directions are discussed.

  15. Synthesis and x-ray characterization of cobalt phosphide (Co₂P) nanorods for the oxygen reduction reaction

    DOE PAGES

    Doan-Nguyen, Vicky V.T.; Su, Dong; Zhang, Sen; ...

    2015-07-14

    Low temperature fuel cells are clean, effective alternative fuel conversion technology. Oxygen reduction reaction (ORR) at the fuel cell cathode has required Pt as the electrocatalyst for high activity and selectivity of the four-electron reaction pathway. Targeting a less expensive, earth abundant alternative, we have developed the synthesis of cobalt phosphide (Co₂P) nanorods for ORR. Characterization techniques that include total X-ray scattering and extended X-ray absorption fine structure revealed a deviation of the nanorods from bulk crystal structure with a contraction along the b orthorhombic lattice parameter. The carbon supported nanorods have comparable activity but are remarkably more stable thanmore » conventional Pt catalysts for the oxygen reduction reaction in alkaline environments.« less

  16. Synthesis and x-ray characterization of cobalt phosphide (Co₂P) nanorods for the oxygen reduction reaction

    SciTech Connect

    Doan-Nguyen, Vicky V.T.; Su, Dong; Zhang, Sen; Trigg, Edward B.; Agarwal, Rahul; Li, Jing; Winey, Karen I.; Murray, Christopher B.

    2015-07-14

    Low temperature fuel cells are clean, effective alternative fuel conversion technology. Oxygen reduction reaction (ORR) at the fuel cell cathode has required Pt as the electrocatalyst for high activity and selectivity of the four-electron reaction pathway. Targeting a less expensive, earth abundant alternative, we have developed the synthesis of cobalt phosphide (Co₂P) nanorods for ORR. Characterization techniques that include total X-ray scattering and extended X-ray absorption fine structure revealed a deviation of the nanorods from bulk crystal structure with a contraction along the b orthorhombic lattice parameter. The carbon supported nanorods have comparable activity but are remarkably more stable than conventional Pt catalysts for the oxygen reduction reaction in alkaline environments.

  17. Electrocatalysis on shape-controlled titanium nitride nanocrystals for the oxygen reduction reaction.

    PubMed

    Dong, Youzhen; Wu, Yongmin; Liu, Mengjia; Li, Jinghong

    2013-10-01

    The high price of platinum (Pt)-based cathode catalysts for the oxygen reduction reaction (ORR) have slowed down the practical application of fuel cells. Thanks to their low cost, and outstanding, stable catalytic properties, titanium nitrides (TiN) are among the most promising non-precious metal electrocatalysts for replacing Pt. However, the shape-activity relationships of TiN electrocatalysts have not been well-studied or understood up to now. In this work, by simply adjusting the shape of TiO2 precursor, we are able to tailor the morphology of the TiN catalysts from nanoparticles to nanotubes. We have synthetized uniform carbon-coated titanium nitride nanotubes (carbon-coated TiN NTs) through a nitridation reaction in NH3 flow using a TiO2 nanotubes/melamine mixture as precursor. The carbon-coated TiN NTs hybrids exhibit excellent electrocatalytic activity for the ORR, coupled with superior methanol tolerance and long-term stability in comparison to commercial Pt/C, through an efficient four-electron-dominant ORR process. Compared with nanoparticles, the one-dimensional and hollow structure of the nanotubes result in greater diffusion of electrolyte and superior electrical conductivity, and contribute to the greatly improved electrocatalytic performance of the carbon-coated TiN NTs nanocomposites.

  18. Manageable N-doped Graphene for High Performance Oxygen Reduction Reaction

    PubMed Central

    Zhang, Yuewei; Ge, Jun; Wang, Lu; Wang, Donghong; Ding, Feng; Tao, Xiaoming; Chen, Wei

    2013-01-01

    Catalysts for oxygen reduction reaction (ORR) are at the heart of key green-energy fuel cell technology. N-doped graphene is a potential metal-free electrode with much better electrocatalytic activity, long-term stability, and tolerance to crossover effect than expensive platinum-based electrocatalysts. Here, we report a feasible direct-synthesis method in preparing N-graphene with manageable N contents in a large scale. The resultant N-graphene used as electrocatalysts exhibits similar catalytic activity but superior stability compared to commercial Pt/C for ORR in an alkaline solution. It was found that their electrocatalytic activities were demonstrated to depend largely on N-doping content. When nitrogen content reaches a high value at about 24–25%, ORR reaction exhibits a favorable formation of water via a four-electron pathway. Furthermore, the effect of pyrolysis temperature and precursor on the activity of N-graphene is systematically analyzed, and may shed some light on the principle of choosing appropriate way for preparing N-graphene. PMID:24067782

  19. Manageable N-doped graphene for high performance oxygen reduction reaction.

    PubMed

    Zhang, Yuewei; Ge, Jun; Wang, Lu; Wang, Donghong; Ding, Feng; Tao, Xiaoming; Chen, Wei

    2013-09-26

    Catalysts for oxygen reduction reaction (ORR) are at the heart of key green-energy fuel cell technology. N-doped graphene is a potential metal-free electrode with much better electrocatalytic activity, long-term stability, and tolerance to crossover effect than expensive platinum-based electrocatalysts. Here, we report a feasible direct-synthesis method in preparing N-graphene with manageable N contents in a large scale. The resultant N-graphene used as electrocatalysts exhibits similar catalytic activity but superior stability compared to commercial Pt/C for ORR in an alkaline solution. It was found that their electrocatalytic activities were demonstrated to depend largely on N-doping content. When nitrogen content reaches a high value at about 24-25%, ORR reaction exhibits a favorable formation of water via a four-electron pathway. Furthermore, the effect of pyrolysis temperature and precursor on the activity of N-graphene is systematically analyzed, and may shed some light on the principle of choosing appropriate way for preparing N-graphene.

  20. Carboxylated, Fe-filled multiwalled carbon nanotubes as versatile catalysts for O2 reduction and H2 evolution reactions at physiological pH.

    PubMed

    Bracamonte, M Victoria; Melchionna, Michele; Stopin, Antoine; Giulani, Angela; Tavagnacco, Claudio; Garcia, Yann; Fornasiero, Paolo; Bonifazi, Davide; Prato, Maurizio

    2015-09-01

    The development of new electrocatalysts for the oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER) at physiological pH is critical for several fields, including fuel cells and biological applications. Herein, the assembly of an electrode based on carboxyl-functionalised hydrophilic multiwalled carbon nanotubes (MWCNTs) filled with Fe phases and their excellent performance as electrocatalysts for ORR and HER at physiological pH are reported. The encapsulated Fe dramatically enhances the catalytic activity, and the graphitic shells play a double role of efficiently mediating the electron transfer to O2 and H2 O reactants and providing a cocoon that prevents uncontrolled Fe oxidation or leaching.

  1. Mechanism of oxygen reduction reaction on Pt(111) in alkaline solution: Importance of chemisorbed water on surface

    SciTech Connect

    Liu, Shizhong; White, Michael G.; Liu, Ping

    2016-06-30

    Here, we report a detailed mechanistic study of the oxygen reduction reaction (ORR) on Pt(111) in alkaline solution, combining density functional theory and kinetic Monte Carlo simulations. A complex reaction network including four possible pathways via either 2e or 4e transfer is established and is able to reproduce the experimental measured polarization curve at both low- and high-potential regions. Our results show that it is essential to account for solvation by water and the dynamic coverage of *OH to describe the reaction kinetics well. In addition, a chemisorbed water (*H2O)-mediated mechanism including 4e transfers is identified, where the reduction steps via *H2O on the surface are potential-independent and only the final removal of *OH from the surface in the form of OH(aq) contributes to the current. For the ORR in alkaline solutions, such a mechanism is more competitive than the associative and dissociative mechanisms typically used to describe the ORR in acid solution. Finally, *OH and **O2 intermediates are found to be critically important for tuning the ORR activity of Pt in alkaline solution. To enhance the activity, the binding of Pt should be tuned in such a way that *OH binding is weak enough to release more surface sites under working conditions, while **O2 binding is strong enough to enable the ORR via the 4e transfer mechanism.

  2. Mechanism of oxygen reduction reaction on Pt(111) in alkaline solution: Importance of chemisorbed water on surface

    SciTech Connect

    Liu, Shizhong; White, Michael G.; Liu, Ping

    2016-06-30

    Here, we report a detailed mechanistic study of the oxygen reduction reaction (ORR) on Pt(111) in alkaline solution, combining density functional theory and kinetic Monte Carlo simulations. A complex reaction network including four possible pathways via either 2e or 4e transfer is established and is able to reproduce the experimental measured polarization curve at both low- and high-potential regions. Our results show that it is essential to account for solvation by water and the dynamic coverage of *OH to describe the reaction kinetics well. In addition, a chemisorbed water (*H2O)-mediated mechanism including 4e transfers is identified, where the reduction steps via *H2O on the surface are potential-independent and only the final removal of *OH from the surface in the form of OH(aq) contributes to the current. For the ORR in alkaline solutions, such a mechanism is more competitive than the associative and dissociative mechanisms typically used to describe the ORR in acid solution. Finally, *OH and **O2 intermediates are found to be critically important for tuning the ORR activity of Pt in alkaline solution. To enhance the activity, the binding of Pt should be tuned in such a way that *OH binding is weak enough to release more surface sites under working conditions, while **O2 binding is strong enough to enable the ORR via the 4e transfer mechanism.

  3. Intumescent flame retardant-derived P,N co-doped porous carbon as an efficient electrocatalyst for the oxygen reduction reaction.

    PubMed

    Wang, Yinling; Zhang, Xuemei; Li, Anna; Li, Maoguo

    2015-10-11

    An intumescent flame retardant (IFR), including melamine (MA), ammonium polyphosphate (APP), and polydopamine (PDA), was utilized as the precursor to prepare P,N co-doped hierarchically porous carbon which exhibited high electrocatalytic activity and durability for the oxygen reduction reaction (ORR). This finding indicates that an ingenious design of the precursor can lead to functional carbon materials using a simple process.

  4. Metal-Organic Framework Derived Hierarchically Porous Nitrogen-Doped Carbon Nanostructures as Novel Electrocatalyst for Oxygen Reduction Reaction

    SciTech Connect

    Fu, Shaofang; Zhu, Chengzhou; Zhou, Yazhou; Yang, Guohai; Jeon, Ju Won; Lemmon, John P.; Du, Dan; Nune, Satish K.; Lin, Yuehe

    2015-10-01

    The hierarchically porous nitrogen-doped carbon materials, derived from nitrogen-containing isoreticular metal-organic framework-3 (IRMOF-3) through direct carbonization, exhibited excellent electrocatalytic activity in alkaline solution for oxygen reduction reaction (ORR). This high activity is attributed to the 10 presence of high percentage of quaternary and pyridinic nitrogen, the high surface area as well as good conductivity. When IRMOF-3 was carbonized at 950 °C (CIRMOF-3-950), it showed four-electron reduction pathway for ORR and exhibited better stability (about 78.5% current density was maintained) than platinum/carbon (Pt/C) in the current durability test. In addition, CIRMOF-3-950 presented high selectivity to cathode reactions compared to commercial Pt/C.

  5. General Solvent-dependent Strategy toward Enhanced Oxygen Reduction Reaction in Graphene/Metal Oxide Nanohybrids: Effects of Nitrogen-containing Solvent

    PubMed Central

    Kao, Wei-Yao; Chen, Wei-Quan; Chiu, Yu-Hsiang; Ho, Yu-Hsuan; Chen, Chun-Hu

    2016-01-01

    A general solvent-dependent protocol directly influencing the oxygen reduction reaction (ORR) in metal oxide/graphene nanohybrids has been demonstrated. We conducted the two-step synthesis of cobalt oxide/N-doped graphene nanohybrids (CNG) with solvents of water, ethanol, and dimethylformamide (DMF), representing tree typical categories of aqueous, polar organic, and organic N-containing solvents commonly adopted for graphene nanocomposites preparation. The superior ORR performance of the DMF-hybrids can be attributed to the high nitrogen-doping, aggregation-free hybridization, and unique graphene porous structures. As DMF is the more effective N-source, the spectroscopic results support a catalytic nitrogenation potentially mediated by cobalt-DMF coordination complexes. The wide-distribution of porosity (covering micro-, meso-, to macro-pore) and micron-void assembly of graphene may further enhance the diffusion kinetics for ORR. As the results, CNG by DMF-synthesis exhibits the high ORR activities close to Pt/C (i.e. only 8 mV difference of half-wave potential with electron transfer number of 3.96) with the better durability in the alkaline condition. Additional graphene hybrids comprised of iron and manganese oxides also show the superior ORR activities by DMF-synthesis, confirming the general solvent-dependent protocol to achieve enhanced ORR activities. PMID:27853187

  6. Co3O4-CeO2/C as a Highly Active Electrocatalyst for Oxygen Reduction Reaction in Al-Air Batteries.

    PubMed

    Liu, Kun; Huang, Xiaobing; Wang, Haiyan; Li, Fuzhi; Tang, Yougen; Li, Jingsha; Shao, Minhua

    2016-12-21

    Developing high-performance and low-cost electrocatalysts for oxygen reduction reaction (ORR) is still a great challenge for Al-air batteries. Herein, CeO2, a unique ORR promoter, was incorporated into ketjenblack (KB) supported Co3O4 catalyst. We developed a facile two-step hydrothermal approach to fabricate Co3O4-CeO2/KB as a high-performance ORR catalyst for Al-air batteries. The ORR activity of Co3O4/KB was significantly increased by mixing with CeO2 nanoparticles. In addition, the Co3O4-CeO2/KB showed a better electrocatalytic performance and stability than 20 wt % Pt/C in alkaline electrolytes, making it a good candidate for highly active ORR catalysts. Co3O4-CeO2/KB favored a four-electron pathway in ORR due to the synergistic interactions between CeO2 and Co3O4. In full cell tests, the Co3O4-CeO2/KB exhibited a higher discharge voltage plateau than CeO2/KB and Co3O4/KB when used in cathode in Al-air batteries.

  7. General Solvent-dependent Strategy toward Enhanced Oxygen Reduction Reaction in Graphene/Metal Oxide Nanohybrids: Effects of Nitrogen-containing Solvent

    NASA Astrophysics Data System (ADS)

    Kao, Wei-Yao; Chen, Wei-Quan; Chiu, Yu-Hsiang; Ho, Yu-Hsuan; Chen, Chun-Hu

    2016-11-01

    A general solvent-dependent protocol directly influencing the oxygen reduction reaction (ORR) in metal oxide/graphene nanohybrids has been demonstrated. We conducted the two-step synthesis of cobalt oxide/N-doped graphene nanohybrids (CNG) with solvents of water, ethanol, and dimethylformamide (DMF), representing tree typical categories of aqueous, polar organic, and organic N-containing solvents commonly adopted for graphene nanocomposites preparation. The superior ORR performance of the DMF-hybrids can be attributed to the high nitrogen-doping, aggregation-free hybridization, and unique graphene porous structures. As DMF is the more effective N-source, the spectroscopic results support a catalytic nitrogenation potentially mediated by cobalt-DMF coordination complexes. The wide-distribution of porosity (covering micro-, meso-, to macro-pore) and micron-void assembly of graphene may further enhance the diffusion kinetics for ORR. As the results, CNG by DMF-synthesis exhibits the high ORR activities close to Pt/C (i.e. only 8 mV difference of half-wave potential with electron transfer number of 3.96) with the better durability in the alkaline condition. Additional graphene hybrids comprised of iron and manganese oxides also show the superior ORR activities by DMF-synthesis, confirming the general solvent-dependent protocol to achieve enhanced ORR activities.

  8. Nitrogen-Doped Carbon Nanoparticle-Carbon Nanofiber Composite as an Efficient Metal-Free Cathode Catalyst for Oxygen Reduction Reaction.

    PubMed

    Panomsuwan, Gasidit; Saito, Nagahiro; Ishizaki, Takahiro

    2016-03-23

    Metal-free nitrogen-doped carbon materials are currently considered at the forefront of potential alternative cathode catalysts for the oxygen reduction reaction (ORR) in fuel cell technology. Despite numerous efforts in this area over the past decade, rational design and development of a new catalyst system based on nitrogen-doped carbon materials via an innovative approach still present intriguing challenges in ORR catalysis research. Herein, a new kind of nitrogen-doped carbon nanoparticle-carbon nanofiber (NCNP-CNF) composite with highly efficient and stable ORR catalytic activity has been developed via a new approach assisted by a solution plasma process. The integration of NCNPs and CNFs by the solution plasma process can lead to a unique morphological feature and modify physicochemical properties. The NCNP-CNF composite exhibits a significantly enhanced ORR activity through a dominant four-electron pathway in an alkaline solution. The enhancement in ORR activity of NCNP-CNF composite can be attributed to the synergistic effects of good electron transport from highly graphitized CNFs as well as abundance of exposed catalytic sites and meso/macroporosity from NCNPs. More importantly, NCNP-CNF composite reveals excellent long-term durability and high tolerance to methanol crossover compared with those of a commercial 20 wt % supported on Vulcan XC-72. We expect that NCNP-CNF composite prepared by this synthetic approach can be a promising metal-free cathode catalyst candidate for ORR in fuel cells and metal-air batteries.

  9. Simultaneous synthesis of gold nanoparticle/graphene nanocomposite for enhanced oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Govindhan, Maduraiveeran; Chen, Aicheng

    2015-01-01

    We report here on a novel and facile technique for the simultaneous synthesis of a highly active and stable gold (Au) nanoparticle/reduced graphene oxide (rGO) sheet nanocomposite as an efficient electrocatalyst to facilitate the oxygen reduction reaction (ORR). X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning electron microscope (SEM), energy-dispersive X-ray (EDX) spectroscopy and electrochemical methods were employed to characterize the Au and rGO nanocomposites formed on the electrode surface. The major advantage of the simultaneous synthetic method is the integration of the superb properties of both Au nanoparticles and graphene in a single-step with a 100% usage of the precursors. The Au/rGO nanocomposites exhibited pronounced electrocatalytic performance towards ORR with approximately three times higher than that of Au nanoparticles. The nanocomposites show the ORR onset peak potentials at 0.12 and -0.03 V (vs Ag/AgCl), with reduction peaks at -0.06 and -0.16 V (vs Ag/AgCl) in 0.1 M H2SO4 and KOH media, which is ∼120-190 mV more positive than that of Au nanoparticles and a commercial Pt/C catalyst. Moreover, the nanocomposites exhibit excellent methanol tolerance and high durability in comparison with the commercial Pt/C. The new method demonstrated in this study provides an efficient route for the generation of ultrafine and highly dense Au nanoparticles that are homogeneously dispersed on rGO sheets for ORR.

  10. In situ Fe2N@N-doped porous carbon hybrids as superior catalysts for oxygen reduction reaction.

    PubMed

    Huang, Xiaoxiao; Yang, Ziyu; Dong, Bing; Wang, Yazhou; Tang, Tianyu; Hou, Yanglong

    2017-03-22

    Developing efficient and economical noble-metal free catalysts for oxygen reduction reaction (ORR) is one of the essential factors for the industrialization of fuel cells. Recent studies on transition metal ORR catalysts have become the priority to practical low-temperature fuel cells. Herein, we proposed a novel in situ design, Fe2N nanoparticles (NPs) in an N doped porous carbon matrix (Fe2N@NPC) derived from metal organic frameworks (MOFs) as high-performance ORR catalysts. The decorated Fe2N NPs increase the amount of Fe-N/C bonding as catalytic site. Meanwhile, the coated NPC facilitates the mass transport of the reaction and improves the conductivity simultaneously. The catalyst exhibits an onset potential of -0.038 V, a half-wave potential of -0.175 V in 0.1 M KOH, and superior stabilities and methanol tolerance performances to commercial Pt/C catalysts. More importantly, the proposed in situ 'two-step' annealing route provides potential possibilities for producing other non-precious metal catalysts for ORR.

  11. Thiolated graphene oxide-supported palladium cobalt alloyed nanoparticles as high performance electrocatalyst for oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Yun, Mira; Ahmed, Mohammad Shamsuddin; Jeon, Seungwon

    2015-10-01

    Thiolated graphene oxide-supported palladium cobalt alloyed catalyst has been synthesized by an electrochemical reduction method (denoted as ER/PdCo-tGO) for electrocatalytic oxygen reduction reaction (ORR). The polyethylene glycol (PEG) has been used as stabilizer for PdCo nanoparticles (NPs) stabilization. This material has been characterized by various instrumental methods. The morphological analysis shows the PdCo alloyed NPs are well set on to the thiolated graphene with better dispersion. The X-ray photoelectron spectroscopy (XPS) shows electrochemical reduction has been done successfully with the increasing C/O ratio from 0.88 to 2.14. Also, the X-ray diffraction (XRD) data reveals that the Co is presents with the oxidized form. The electrocatalytic activities have been verified using cyclic voltammetry (CV) and hydrodynamic voltammetry techniques in 0.1 M KOH electrolyte. The as prepared catalyst has shown better ORR onset potential (0.95 V vs. RHE) and superior mass activity (329 mA mgPd-1 at 0.8 V) which is 3.1 times higher than that of 20wt% Pt/C. The reaction kinetics have confirmed that the ORR at ER/PdCo-tGO catalyst follows a four electron transfer reaction process.

  12. Co3O4 nanoparticles anchored on nitrogen-doped reduced graphene oxide as a multifunctional catalyst for H2O2 reduction, oxygen reduction and evolution reaction

    NASA Astrophysics Data System (ADS)

    Zhang, Tingting; He, Chuansheng; Sun, Fengzhan; Ding, Yongqi; Wang, Manchao; Peng, Lin; Wang, Jiahui; Lin, Yuqing

    2017-03-01

    This study describes a facile and effective route to synthesize hybrid material consisting of Co3O4 nanoparticles anchored on nitrogen-doped reduced graphene oxide (Co3O4/N-rGO) as a high-performance tri-functional catalyst for oxygen reduction reaction (ORR), oxygen evolution reaction (OER) and H2O2 sensing. Electrocatalytic activity of Co3O4/N-rGO to hydrogen peroxide reduction was tested by cyclic voltammetry (CV), linear sweep voltammetry (LSV) and chronoamperometry. Under a reduction potential at ‑0.6 V to H2O2, this constructing H2O2 sensor exhibits a linear response ranging from 0.2 to 17.5 mM with a detection limit to be 0.1 mM. Although Co3O4/rGO or nitrogen-doped reduced graphene oxide (N-rGO) alone has little catalytic activity, the Co3O4/N-rGO exhibits high ORR activity. The Co3O4/N-rGO hybrid demonstrates satisfied catalytic activity with ORR peak potential to be ‑0.26 V (vs. Ag/AgCl) and the number of electron transfer number is 3.4, but superior stability to Pt/C in alkaline solutions. The same hybrid is also highly active for OER with the onset potential, current density and Tafel slope to be better than Pt/C. The unusual catalytic activity of Co3O4/N-rGO for hydrogen peroxide reduction, ORR and OER may be ascribed to synergetic chemical coupling effects between Co3O4, nitrogen and graphene.

  13. Co3O4 nanoparticles anchored on nitrogen-doped reduced graphene oxide as a multifunctional catalyst for H2O2 reduction, oxygen reduction and evolution reaction

    PubMed Central

    Zhang, Tingting; He, Chuansheng; Sun, Fengzhan; Ding, Yongqi; Wang, Manchao; Peng, Lin; Wang, Jiahui; Lin, Yuqing

    2017-01-01

    This study describes a facile and effective route to synthesize hybrid material consisting of Co3O4 nanoparticles anchored on nitrogen-doped reduced graphene oxide (Co3O4/N-rGO) as a high-performance tri-functional catalyst for oxygen reduction reaction (ORR), oxygen evolution reaction (OER) and H2O2 sensing. Electrocatalytic activity of Co3O4/N-rGO to hydrogen peroxide reduction was tested by cyclic voltammetry (CV), linear sweep voltammetry (LSV) and chronoamperometry. Under a reduction potential at −0.6 V to H2O2, this constructing H2O2 sensor exhibits a linear response ranging from 0.2 to 17.5 mM with a detection limit to be 0.1 mM. Although Co3O4/rGO or nitrogen-doped reduced graphene oxide (N-rGO) alone has little catalytic activity, the Co3O4/N-rGO exhibits high ORR activity. The Co3O4/N-rGO hybrid demonstrates satisfied catalytic activity with ORR peak potential to be −0.26 V (vs. Ag/AgCl) and the number of electron transfer number is 3.4, but superior stability to Pt/C in alkaline solutions. The same hybrid is also highly active for OER with the onset potential, current density and Tafel slope to be better than Pt/C. The unusual catalytic activity of Co3O4/N-rGO for hydrogen peroxide reduction, ORR and OER may be ascribed to synergetic chemical coupling effects between Co3O4, nitrogen and graphene. PMID:28272415

  14. Al13@Pt42 Core-Shell Cluster for Oxygen Reduction Reaction

    PubMed Central

    Xiao, B. B.; Zhu, Y. F.; Lang, X. Y.; Wen, Z.; Jiang, Q.

    2014-01-01

    To increase Pt utilization for oxygen reduction reaction (ORR) in fuel cells, reducing particle sizes of Pt is a valid way. However, poisoning or surface oxidation limits the smallest size of Pt particles at 2.6 nm with a low utility of 20%. Here, using density functional theory calculations, we develop a core-shell Al13@Pt42 cluster as a catalyst for ORR. Benefit from alloying with Al in this cluster, the covalent Pt-Al bonding effectively activates the Pt atoms at the edge sites, enabling its high utility up to 70%. Valuably, the adsorption energy of O is located at the optimal range with 0.0–0.4 eV weaker than Pt(111), while OH-poisoning does not observed. Moreover, ORR comes from O2 dissociation mechanism where the rate-limiting step is located at OH formation from O and H with a barrier of 0.59 eV, comparable with 0.50 eV of OH formation from O and H2O on Pt(111). PMID:24902886

  15. Reactivity Descriptors for the Activity of Molecular MN4 Catalysts for the Oxygen Reduction Reaction.

    PubMed

    Zagal, José H; Koper, Marc T M

    2016-11-14

    Similarities are established between well-known reactivity descriptors of metal electrodes for their activity in the oxygen reduction reaction (ORR) and the reactivity of molecular catalysts, in particular macrocyclic MN4 metal complexes confined to electrode surfaces. We show that there is a correlation between the M(III) /M(II) redox potential of MN4 chelates and the M-O2 binding energies. Specifically, the binding energy of O2 (and other O species) follows the M(III) -OH/M(II) redox transition for MnN4 and FeN4 chelates. The ORR volcano plot for MN4 catalysts is similar to that for metal catalysts: catalysts on the weak binding side (mostly CoN4 chelates) yield mainly H2 O2 as the product, with an ORR onset potential independent of the pH value on the NHE scale (and therefore pH-dependent on the RHE scale); catalysts on the stronger binding side yield H2 O as the product with the expected pH-dependence on the NHE scale. The suggested descriptors also apply to heat-treated pyrolyzed MN4 catalysts. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Catalytic characteristics of AgCu bimetallic nanoparticles in the oxygen reduction reaction.

    PubMed

    Shin, Kihyun; Kim, Da Hye; Lee, Hyuck Mo

    2013-06-01

    Intensive research on oxygen reduction reaction (ORR) catalysts has been undertaken to find a Pt substitute or reduce the amount of Pt. Ag nanoparticles are potential Pt substitutes; however, the weak oxygen adsorption energy of Ag prompted investigation of other catalysts. Herein, we prepared AgCu bimetallic nanoparticle (NP) systems to improve the catalytic performance and compared the catalytic performance of Ag, Cu, AgCu (core-shell), and AgCu (alloy) NP systems as new catalyst by investigating the adsorption energy of oxygen and the activation energy of oxygen dissociation, which is known to be the rate-determining step of ORR. By analyzing HOMO-level isosurfaces of metal NPs and oxygen, we found that the adsorption sites and the oxygen adsorption energies varied with different configurations of NPs. We then plotted the oxygen adsorption energies against the energy barrier of oxygen dissociation to determine the catalytic performance. AgCu (alloy) and Cu NPs exhibited strong adsorption energies and low activation-energy barriers. However, the overly strong oxygen adsorption energy of Cu NPs hindered the ORR. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Phasic availability of terminal electron acceptor on oxygen reduction reaction in microbial fuel cell.

    PubMed

    Shanthi Sravan, J; Butti, Sai Kishore; Verma, Anil; Venkata Mohan, S

    2017-10-01

    Oxygen-reduction reactions (ORR) plays a pivotal role in determining microbial fuel cells (MFC) performance. In this study, an attempt to determine the influence of the phasic availability of terminal electron acceptor (TEA) on ORR was made. Two MFCs operated with dissolved oxygen (MFC-DC) and air (MFC-SC) as TEA were constructed and analyzed in continuous mode under open and closed circuit conditions. The bio-electrochemical analysis showed a marked influence of dissolved oxygen resulting in a maximum power density with MFC-DC (769mW/m(2)) compared to MFC-SC (684mW/m(2)). The availability of O2 in dissolved phase has lowered the activation losses during the MFC operation as a result of effective ORR. The cyclic voltammetry analysis revealed the TEA dependent biocatalyst activity of NADH and cytochrome complex which enabled electron transfer kinetics and improved substrate utilization. Finally, the study evidenced the critical role of TEA phasic availability to regulate the bio-electrogenic and substrate degradation potential in MFC. Copyright © 2017 Elsevier Ltd. All rights reserved.

  18. Tuning graphene for energy and environmental applications: Oxygen reduction reaction and greenhouse gas mitigation

    NASA Astrophysics Data System (ADS)

    Haque, Enamul; Sarkar, Shuranjan; Hassan, Mahbub; Hossain, Md. Shahriar; Minett, Andrew I.; Dou, Shi Xue; Gomes, Vincent G.

    2016-10-01

    Porous nitrogen-doped graphene samples were synthesized and tuned via pyrolysis of solid nitrogen precursor dimethyl-aminoterephthalate with graphene oxide as template. Our investigations show that the extent of thermal treatment, total concentration of nitrogen and the nature of nitrogen moieties play important roles in enhancing oxygen reduction reaction (ORR) and CO2 uptake. N-doped graphene synthesized at 650 °C (NG-650) with specific BET surface area of 278 m2/g, exhibits enhanced CO2 sorption capacity of 4.43 mmol/g (at 298 K, 1 bar) with exceptional selectivity (CO2:N2 = 42) and cyclic regeneration stability. In contrast, nitrogen-doped graphene synthesized at 750 °C (NG-750) demonstrated excellent catalytic activity for ORR via favourable 4e- transfer, performance stability with tests conducted up to 5000 cycles, and is unaffected by methanol cross-over effect. Thus, NG-750 shows potential to replace metal-based electrodes for fuel cell application. The comparative results for ORR with non-doped and nitrogen-doped graphene electrodes showed that graphitic nitrogen sites play vital role in enhancing catalytic activity.

  19. Activity Trends of Binary Silver Alloy Nanocatalysts for Oxygen Reduction Reaction in Alkaline Media.

    PubMed

    Wu, Xiaoqiang; Chen, Fuyi; Zhang, Nan; Lei, Yimin; Jin, Yachao; Qaseem, Adnan; Johnston, Roy L

    2017-02-02

    The electrocatalytic activity of Pt-based alloys exhibits a strong dependence on their electronic structures, but a relationship between electronic structure and oxygen reduction reaction (ORR) activity in Ag-based alloys is still not clear. Here, a vapor deposition based approach is reported for the preparation of Ag75 M25 (M = Cu, Co, Fe, and In) and Agx Cu100-x (x = 0, 25, 45, 50, 55, 75, 90, and 100) nanocatalysts and their electronic structures are determined by valence band spectra. The relationship of the d-band center and ORR activity exhibits volcano-shape behaviors, where the maximum catalytic activity is obtained for Ag75 Cu25 alloys. The ORR enhancement of Ag75 Cu25 alloys originates from the 0.12 eV upshift in d-band center relative to pure Ag, which is different from the downshift in the d-band center in Pt-based alloys. The activity trend for these Ag75 M25 alloys is in the order of Ag75 Cu25 > Ag75 Fe25 > Ag75 Co25 . These results provide an insight to understand the activity and stability enhancement of Ag75 Cu25 and Ag50 Cu50 catalysts by alloying.

  20. Synthesis of 2D Nitrogen-Doped Mesoporous Carbon Catalyst for Oxygen Reduction Reaction

    PubMed Central

    Yu, Zhipeng; Piao, Jinhua; Liang, Zhenxing

    2017-01-01

    2D nitrogen-doped mesoporous carbon (NMC) is synthesized by using a mesoporous silica film as hard template, which is then investigated as a non-precious metal catalyst for the oxygen reduction reaction (ORR). The effect of the synthesis conditions on the silica template and carbon is extensively investigated. In this work, we employ dual templates—viz. graphene oxide and triblock copolymer F127—to control the textural features of a 2D silica film. The silica is then used as a template to direct the synthesis of a 2D nitrogen-doped mesoporous carbon. The resultant nitrogen-doped mesoporous carbon is characterized by transmission electron microscopy (TEM), nitrogen ad/desorption isotherms, X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV), and rotating disk electrode measurements (RDE). The electrochemical test reveals that the obtained 2D-film carbon catalyst yields a highly electrochemically active surface area and superior electrocatalytic activity for the ORR compared to the 3D-particle. The superior activity can be firstly attributed to the difference in the specific surface area of the two catalysts. More importantly, the 2D-film morphology makes more active sites accessible to the reactive species, resulting in a much higher utilization efficiency and consequently better activity. Finally, it is noted that all the carbon catalysts exhibit a higher ORR activity than a commercial Pt catalyst, and are promising for use in fuel cells. PMID:28772558

  1. Polyaniline and Perfluorosulfonic Acid Co-Stabilized Metal Catalysts for Oxygen Reduction Reaction.

    PubMed

    Ye, Bei; Cheng, Kun; Li, Wenqiang; Liu, Jing; Zhang, Jie; Mu, Shichun

    2017-06-06

    A proton (perfluorosulfonic acid, PFSA) and electron (polyaniline, PANI) conductor polymer costabilized Pt catalyst (Pt-PFSA/C@PANI) is synthesized to improve the long-term stability of polymer electrolyte membrane fuel cells (PEMFCs). The prepared catalyst not only displays comparable oxygen reduction reaction (ORR) activity, but significantly higher electrochemical stability than commercial porous carbon nanosphere supported Pt catalysts (Pt/C). This robust electrochemical property can be due to the result of PFSA and PANI. PANI as protector inhibits carbon nanospheres from corrosion of carbon supports in harsh chemical and electrochemical conditions. Meanwhile, PFSA wrapped Pt NPs (Pt@PFSA) can also anchor Pt NPs on C@PANI to avoid aggregation and detachment of Pt NPs, due to the increased metal-support interaction caused by the strong electrostatic attraction between PANI and PFSA with corresponding positive and negative charges. Significantly, after coating PANI on carbon supports (C@PANI), almost all micropores in the surface of carbon disappear, effectively avoiding the embedding of Pt nanopaticles into micropores. Furthermore, the triple-phase boundary toward ORR catalysis can be facilitated by PFSA as proton conductor (solid electrolyte). These are of benefit to increase utilization of Pt noble metals and ORR activity of our new catalysts.

  2. Functional palladium tetrapod core of heterogeneous palladium-platinum nanodendrites for enhanced oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Nguyen, Trung-Thanh; Pan, Chun-Jern; Liu, Jyong-Yue; Chou, Hung-Lung; Rick, John; Su, Wei-Nien; Hwang, Bing-Joe

    2014-04-01

    The synthesis, characterization, and application of bimetallic Pd-Pt nanocatalysts with heterogeneous structures are reported. The Pd tetrapod core is demonstrated to enhance the catalytic activity and durability of Pd@Pt nanodendrites for the oxygen reduction reaction (ORR). Special attention is given to the effects of oxalate-ion-formaldehyde during the hydrothermal synthesis of various Pd morphologies at different temperatures. Pd tetrapod synthesis can be delicately achieved without directly using hazardous CO gas. 30 wt% Pt on tetrapodal and truncated-octahedral Pd cores and 50 wt% Pt on tetrapodal Pd cores are prepared and compared against the commercial Pt/C catalyst (E-Tek) for ORR. The Pdtetrapod@30 wt% Pt catalyst exhibits the highest ORR activity. Overall, the Pd tetrapod core is a functional morphology which offers high-index facets for the subsequent deposition of Pt(110) nanodendrites, with the bimetallic interaction between two materials allowing for good electron transfer from the Pd core onto the Pt surfaces. Both effects contribute to the increased catalytic activity of Pdtetrapod@30 wt% Pt, even under a lower loading of Pt. Furthermore, Pdtetrapod@30 wt% Pt has a rather large particle size (∼39.5 nm) which enhances durability and resistance to the agglomeration of Pt.

  3. Oleylamine-functionalized palladium nanoparticles with enhanced electrocatalytic activity for the oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Shi, Yi; Yin, Shengkang; Ma, Yanrong; Lu, Dingkun; Chen, Yu; Tang, Yawen; Lu, Tianhong

    2014-01-01

    The oleylamine (OAm)-functionalized Pd nanoparticles (Pd-OAm) have been conveniently synthesized through direct thermal decomposition method of low cost palladium acetate. The morphology, crystalline structure and composition of the Pd-OAm are investigated by transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Fourier transform infrared (FT-IR) spectroscopy, XPS and zeta potential analysis confirm the successful immobilization of OAm molecules on the Pd nanoparticles surface. The Pd-OAm displays an enhanced electrocatalytic activity and formic acid-tolerant ability for the oxygen reduction reaction (ORR), suggesting a potential application in cathodic catalyst for direct formic acid fuel cells.

  4. Tuning nondoped carbon nanotubes to an efficient metal-free electrocatalyst for oxygen reduction reaction by localizing the orbital of the nanotubes with topological defects

    NASA Astrophysics Data System (ADS)

    Jiang, Shujuan; Li, Zhe; Wang, Huayu; Wang, Yun; Meng, Lina; Song, Shaoqing

    2014-11-01

    Breaking the electron delocalization of sp2 carbon materials by heteroatom doping is a practical strategy to produce metal-free electrocatalysts of oxygen reduction reaction (ORR) for fuel cells. Whether carbon nanotubes (CNTs) can be efficiently tuned into ORR electrocatalysts only by intrinsic defects rather than heteroatom doping has not been well studied yet in experiment and theory. Here we introduce topological defects of nonhexagon carbon rings into CNTs to break the delocalization of their orbitals and make such type of CNTs to be a high-performance ORR catalyst. The electrochemical tests and theoretical studies indicate that the O2 chemisorption and the following electrocatalytic activity are promoted by the introduced topological defects and show a strong dependence on the defect amount. Such topological-defect CNTs (TCNTs) have an excellent ORR performance owing to a 3.8-electron-transferring process, ~4 times higher current density and ~120 mV more positive peak potential than normally straight CNTs. Moreover, TCNTs show a higher steady-state diffusion current density and much better stability and immunity to crossover effect as compared with commercial Pt/C catalyst. Hence, our results strongly suggest that tuning the surface structure of CNTs with nonhexagon carbon rings is a novel strategy for designing advanced ORR electrocatalysts for fuel cells.Breaking the electron delocalization of sp2 carbon materials by heteroatom doping is a practical strategy to produce metal-free electrocatalysts of oxygen reduction reaction (ORR) for fuel cells. Whether carbon nanotubes (CNTs) can be efficiently tuned into ORR electrocatalysts only by intrinsic defects rather than heteroatom doping has not been well studied yet in experiment and theory. Here we introduce topological defects of nonhexagon carbon rings into CNTs to break the delocalization of their orbitals and make such type of CNTs to be a high-performance ORR catalyst. The electrochemical tests and

  5. Electrocatalytic oxygen reduction reaction on perovskite oxides: series versus direct pathway.

    PubMed

    Poux, Tiphaine; Bonnefont, Antoine; Kéranguéven, Gwénaëlle; Tsirlina, Galina A; Savinova, Elena R

    2014-07-21

    The mechanism of the oxygen reduction reaction (ORR) on LaCoO(3) and La(0.8)Sr(0.2)MnO(3) perovskite oxides is studied in 1 M NaOH by using the rotating ring disc electrode (RRDE) method. By combining experimental studies with kinetic modeling, it was demonstrated that on perovskite, as well as on perovskite/carbon electrodes, the ORR follows a series pathway through the intermediate formation of hydrogen peroxide. The escape of this intermediate from the electrode strongly depends on: 1) The loading of perovskite; high loadings lead to an overall 4 e(-) oxygen reduction due to efficient hydrogen peroxide re-adsorption on the active sites and its further reduction. 2) The addition of carbon to the catalytic layer, which affects both the utilization of the perovskite surface and the production of hydrogen peroxide. 3) The type of oxide; La(0.8)Sr(0.2)MnO(3) displays higher (compared to LaCoO(3)) activity in the reduction of oxygen to hydrogen peroxide and in the reduction/oxidation of the latter.

  6. High resolution mapping of oxygen reduction reaction kinetics at polycrystalline platinum electrodes.

    PubMed

    Chen, Chang-Hui; Meadows, Katherine E; Cuharuc, Anatolii; Lai, Stanley C S; Unwin, Patrick R

    2014-09-14

    The scanning droplet-based technique, scanning electrochemical cell microscopy (SECCM), combined with electron backscatter diffraction (EBSD), is demonstrated as a powerful approach for visualizing surface structure effects on the rate of the oxygen reduction reaction (ORR) at polycrystalline platinum electrodes. Elucidating the effect of electrode structure on the ORR is of major interest in connection to electrocatalysis for energy-related applications. The attributes of the approach herein stem from: (i) the ease with which the polycrystalline substrate electrode can be prepared; (ii) the wide range of surface character open to study; (iii) the possibility of mapping reactivity within a particular facet (or grain), in a pseudo-single-crystal approach, and acquiring a high volume of data as a consequence; (iv) the ready ability to measure the activity at grain boundaries; and (v) an experimental arrangement (SECCM) that mimics the three-phase boundary in low temperature fuel cells. The kinetics of the ORR was analyzed and a finite element method model was developed to explore the effect of the three-phase boundary, in particular to examine pH variations in the droplet and the differential transport rates of the reactants and products. We have found a significant variation of activity across the platinum substrate, inherently linked to the crystallographic orientation, but do not detect any enhanced activity at grain boundaries. Grains with (111) and (100) contributions exhibit considerably higher activity than those with (110) and (100) contributions. These results, which can be explained by reference to previous single-crystal measurements, enhance our understanding of ORR structure-activity relationships on complex high-index platinum surfaces, and further demonstrate the power of high resolution flux imaging techniques to visualize and understand complex electrocatalyst materials.

  7. Fundamental Investigation of Oxygen Reduction Reaction on Rhodium Sulfide-Based Chalcogenides

    SciTech Connect

    Ziegelbauer, J.; Gatewood, D; Gulla, A; Guinel, M; Ernst, F; Ramaker, D; Mukerjee, S

    2009-01-01

    Synchrotron-based X-ray absorption spectroscopy (XAS), including the surface-specific {Delta}XANES technique, is used to investigate the active reaction site for water activation and the oxygen reduction reaction (ORR) on the novel, mixed-phase chalcogenide electrocatalyst RhxSy/C (De Nora). The specific adsorption of water, OH, and O as a function of overpotential is reported. This study builds on a prior communication based solely on interpreting the XAS spectra of RhxSy with respect to the metallic Rh3S4 phase. Here, a more extensive overview of the electrocatalysis is provided on RhxSy/C, the thermally grown Rh2S3/C and Rh3S4/C preferential phases and a standard 30 wt % Rh/C electrocatalyst, including results obtained by X-ray diffraction (XRD), XAS, high-resolution transmission electron imaging, microanalysis, and electrochemical investigations. Heating of the RhxSy catalysts to prepare the two preferential phases causes Rh segregation and the formation of Rh metal particles, and immersion in TFMSA causes S dissolution and the formation of a Rh skin on the RhxSy samples. It is shown that some Rh-Rh interactions are needed to carry out the ORR. This is present on the Rh6 moieties in both the Rh3S4 and RhxSy catalysts, but a partial Rh skin (present from acid dissolution) is also contributing to the ORR observed on RhxSy. This to our knowledge is the first time a reaction site in a multiphase inorganic framework structure has been investigated in terms of electrocatalytic pathway for oxygen reduction.

  8. Surface-rough Fe-N/C composite wrapped on carbon nanotubes as efficient electrocatalyst for oxygen reduction reaction.

    PubMed

    Xiao, Chunhui; Chen, Xu; Tang, Yuhai

    2017-06-02

    Fe-N/C composites are considered one of the most promising non-precious-metal electrocatalysts for oxygen reduction reaction (ORR). In this paper, we fabricate a novel and efficient carbon nanotube (CNT)-supported Fe-N/C composite catalyst, via the surface-self-polymerization of polydopamine and then the incorporation with Fe species on CNTs, followed by the pyrolysis process. The obtained catalyst demonstrates excellent electrocatalytic performance towards ORR in alkaline media. The modification of Fe-incorporated nitrogen-rich-carbons (Fe-CNx) on CNTs lowers the ORR half-wave-potential by ∼190 mV, giving this catalyst with an onset ORR potential of 0.95 V (versus reversible hydrogen electrode (RHE)), a half-wave potential of 0.82 V (versus RHE), and the limiting current density of 5.39 mA cm(-2) in 0.1 M KOH. The performance of the as-prepared catalyst is comparatively better than the commercially available Pt/C in terms of positive half-wave potential and larger limiting current, superior durability, and higher tolerance to the methanol.

  9. Surface-nitrogen-rich ordered mesoporous carbon as an efficient metal-free electrocatalyst for oxygen reduction reaction.

    PubMed

    Xiao, Chunhui; Chen, Xu; Fan, Zhaoyang; Liang, Jin; Zhang, Bo; Ding, Shujiang

    2016-11-04

    Exploring efficient metal-free electrocatalysts for oxygen reduction reactions (ORR) will have a great impact on the field of fuel cells and metal-air batteries. In this paper, we report a simple and efficient routine to coat ordered mesoporous carbon (CMK-3) with nitrogen-doped carbon via pyrolysis of the surface-self-polymerized polydopamine. The optimized CMK-3 catalyst with a coating of nitrogen-doped carbon demonstrates excellent electrocatalytic activity towards ORR in alkaline media. The coating procedure under optimized conditions lowers the ORR half-wave-potential by 80 mV, giving a genuine metal-free catalyst with an onset ORR potential of 0.96 V (vs reversible hydrogen electrode (RHE)) and half-wave potential of 0.83 V (vs RHE) in 0.1 M KOH, which is much better than other carbon material-based catalysts (such as carbon nanotubes and their composites). The performance of this surface-nitrogen-rich CMK-3 catalyst is also superior to that of N-doped ordered mesoporous carbon synthesized by means of the 'nanocasting' technique. Furthermore, the as-prepared catalyst performs comparably in terms of activity, superior durability, and higher tolerance to methanol compared with commercially available Pt/C.

  10. Proton conductive Pt-Co nanoparticles anchoring on citric acid functionalized graphene for efficient oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Zhao, Yige; Liu, Jingjun; Wu, Yijun; Wang, Feng

    2017-08-01

    Designing highly efficient electro-catalysts for the oxygen reduction reaction (ORR) has been regarded as a demanding task in the development of renewable energy sources. However, little attention has been paid on improving Pt-based catalysts by promoting proton transfer from the electrolyte solutions to the catalyst layer at the cathode. Herein, we design proton conductive Pt-Co alloy nanoparticles anchoring on citric acid functionalized graphene (Pt-Co/CA-G) catalysts for efficient ORR. The facile modification approach for graphene can introduce oxygenated functional groups on the graphene surface to promote proton transfer as well as keeping the high electron conductivity without destroying the graphene original structure. The electrochemical results show that the Pt-Co/CA-G catalyst exhibits more excellent ORR activity and stability than the commercial Pt/C catalyst, which can be attributed to its improved proton transfer ability. The fast proton transfer comes from the hydrogen-bonding networks formed by the interaction between the oxygenated functional groups and water molecules. This work provides not only a novel and simple approach to modify graphene but also an effective strategy to improve Pt-based catalysts for the ORR.

  11. The enhanced electrocatalytic activity of okara-derived N-doped mesoporous carbon for oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Wang, Rongfang; Wang, Hui; Zhou, Tianbao; Key, Julian; Ma, Yanjiao; Zhang, Zheng; Wang, Qizhao; Ji, Shan

    2015-01-01

    Nitrogen-doped carbon (N-C) catalysts can potentially offer high ORR (oxygen reduction reaction) electrocatalytic activity comparable to Pt/C catalysts. Here, we establish a correlation between N-species (pyridinic-N and graphitic-N) with high ORR activity and a key role for Fe in their preparation. N-C catalysts are prepared from okara (a cheap, nitrogen-rich, biomass precursor) using a facile synthesis method with inclusion of FeCl3 at different steps of synthesis. Mesoporous N-C catalyst is produced that had ORR activity comparable to that of commercial Pt/C catalyst. High ORR-activity N-C results from the presence of FeCl3 at a specific step during synthesis. Detailed investigation by XPS reveals that increased levels of pyridinic-N and graphitic-N arose from pyridinic-N-oxide conversion in the presence of Fe. We conclude that transforming inert N species to active N species underlies the increase in active catalytic sites on the carbon surface and offers a means to improve N-C catalyst performance.

  12. 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

  13. Carbon Supported Engineering NiCo2O4 Hybrid Nanofibers with Enhanced Electrocatalytic Activity for Oxygen Reduction Reaction

    PubMed Central

    Hassan, Diab; El-safty, Sherif; Khalil, Khalil Abdelrazek; Dewidar, Montasser; Abu El-magd, Gamal

    2016-01-01

    The design of cheap and efficient oxygen reduction reaction (ORR) electrocatalysts is of a significant importance in sustainable and renewable energy technologies. Therefore, ORR catalysts with superb electrocatalytic activity and durability are becoming a necessity but still remain challenging. Herein, we report C/NiCo2O4 nanocomposite fibers fabricated by a straightforward electrospinning technique followed by a simple sintering process as a promising ORR electrocatalyst in alkaline condition. The mixed-valence oxide can offer numerous accessible active sites. In addition, the as-obtained C/NiCo2O4 hybrid reveals significantly remarkable electrocatalytic performance with a highly positive onset potential of 0.65 V, which is only 50 mV lower than that of commercially available Pt/C catalysts. The analyses indicate that C/NiCo2O4 catalyst can catalyze O2-molecules via direct four electron pathway in a similar behavior as commercial Pt/C catalysts dose. Compared to single NiCo2O4 and carbon free NiCo2O4, the C/NiCo2O4 hybrid displays higher ORR current and more positive half-wave potential. The incorporated carbon matrices are beneficial for fast electron transfer and can significantly impose an outstanding contribution to the electrocatalytic activity. Results indicate that the synthetic strategy hold a potential as efficient route to fabricate highly active nanostructures for practical use in energy technologies. PMID:28773878

  14. Tungsten carbide encapsulated in nitrogen-doped carbon with iron/cobalt carbides electrocatalyst for oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Zhang, Jie; Chen, Jinwei; Jiang, Yiwu; Zhou, Feilong; Wang, Gang; Wang, Ruilin

    2016-12-01

    This work presents a type of hybrid catalyst prepared through an environmental and simple method, combining a pyrolysis of transition metal precursors, a nitrogen-containing material, and a tungsten source to achieve a one-pot synthesis of N-doping carbon, tungsten carbides, and iron/cobalt carbides (Fe/Co/WC@NC). The obtained Fe/Co/WC@NC consists of uniform Fe3C and Co3C nanoparticles encapsulated in graphitized carbon with surface nitrogen doping, closely wrapped around a plate-like tungsten carbide (WC) that functions as an efficient oxygen reduction reaction (ORR) catalyst. The introduction of WC is found to promote the ORR activity of Fe/Co-based carbide electrocatalysts, which is attributed to the synergistic catalysts of WC, Fe3C, and Co3C. Results suggest that the composite exhibits comparable electrocatalytic activity, higher durability, and ability for methanol tolerance compared with commercial Pt/C for ORR in alkaline electrolyte. These advantages make Fe/Co/WC@NC a promising ORR electrocatalyst and a cost-effective alternative to Pt/C for practical application as fuel cell.

  15. Surface-rough Fe-N/C composite wrapped on carbon nanotubes as efficient electrocatalyst for oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Xiao, Chunhui; Chen, Xu; Tang, Yuhai

    2017-06-01

    Fe-N/C composites are considered one of the most promising non-precious-metal electrocatalysts for oxygen reduction reaction (ORR). In this paper, we fabricate a novel and efficient carbon nanotube (CNT)-supported Fe-N/C composite catalyst, via the surface-self-polymerization of polydopamine and then the incorporation with Fe species on CNTs, followed by the pyrolysis process. The obtained catalyst demonstrates excellent electrocatalytic performance towards ORR in alkaline media. The modification of Fe-incorporated nitrogen-rich-carbons (Fe-CNx) on CNTs lowers the ORR half-wave-potential by ˜190 mV, giving this catalyst with an onset ORR potential of 0.95 V (versus reversible hydrogen electrode (RHE)), a half-wave potential of 0.82 V (versus RHE), and the limiting current density of 5.39 mA cm-2 in 0.1 M KOH. The performance of the as-prepared catalyst is comparatively better than the commercially available Pt/C in terms of positive half-wave potential and larger limiting current, superior durability, and higher tolerance to the methanol.

  16. Investigation of Supported Pd-Based Electrocatalysts for the Oxygen Reduction Reaction: Performance, Durability and Methanol Tolerance

    PubMed Central

    Lo Vecchio, Carmelo; Alegre, Cinthia; Sebastián, David; Stassi, Alessandro; Aricò, Antonino S.; Baglio, Vincenzo

    2015-01-01

    Next generation cathode catalysts for direct methanol fuel cells (DMFCs) must have high catalytic activity for the oxygen reduction reaction (ORR), a lower cost than benchmark Pt catalysts, and high stability and high tolerance to permeated methanol. In this study, palladium catalysts supported on titanium suboxides (Pd/TinO2n–1) were prepared by the sulphite complex route. The aim was to improve methanol tolerance and lower the cost associated with the noble metal while enhancing the stability through the use of titanium-based support; 30% Pd/Ketjenblack (Pd/KB) and 30% Pd/Vulcan (Pd/Vul) were also synthesized for comparison, using the same methodology. The catalysts were ex-situ characterized by physico-chemical analysis and investigated for the ORR to evaluate their activity, stability, and methanol tolerance properties. The Pd/KB catalyst showed the highest activity towards the ORR in perchloric acid solution. All Pd-based catalysts showed suitable tolerance to methanol poisoning, leading to higher ORR activity than a benchmark Pt/C catalyst in the presence of low methanol concentration. Among them, the Pd/TinO2n–1 catalyst showed a very promising stability compared to carbon-supported Pd samples in an accelerated degradation test of 1000 potential cycles. These results indicate good perspectives for the application of Pd/TinO2n–1 catalysts in DMFC cathodes. PMID:28793693

  17. Surface-nitrogen-rich ordered mesoporous carbon as an efficient metal-free electrocatalyst for oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Xiao, Chunhui; Chen, Xu; Fan, Zhaoyang; Liang, Jin; Zhang, Bo; Ding, Shujiang

    2016-11-01

    Exploring efficient metal-free electrocatalysts for oxygen reduction reactions (ORR) will have a great impact on the field of fuel cells and metal-air batteries. In this paper, we report a simple and efficient routine to coat ordered mesoporous carbon (CMK-3) with nitrogen-doped carbon via pyrolysis of the surface-self-polymerized polydopamine. The optimized CMK-3 catalyst with a coating of nitrogen-doped carbon demonstrates excellent electrocatalytic activity towards ORR in alkaline media. The coating procedure under optimized conditions lowers the ORR half-wave-potential by 80 mV, giving a genuine metal-free catalyst with an onset ORR potential of 0.96 V (vs reversible hydrogen electrode (RHE)) and half-wave potential of 0.83 V (vs RHE) in 0.1 M KOH, which is much better than other carbon material-based catalysts (such as carbon nanotubes and their composites). The performance of this surface-nitrogen-rich CMK-3 catalyst is also superior to that of N-doped ordered mesoporous carbon synthesized by means of the ‘nanocasting’ technique. Furthermore, the as-prepared catalyst performs comparably in terms of activity, superior durability, and higher tolerance to methanol compared with commercially available Pt/C.

  18. Heteroatoms ternary-doped porous carbons derived from MOFs as metal-free electrocatalysts for oxygen reduction reaction.

    PubMed

    Li, Ji-Sen; Li, Shun-Li; Tang, Yu-Jia; Li, Kui; Zhou, Lei; Kong, Ning; Lan, Ya-Qian; Bao, Jian-Chun; Dai, Zhi-Hui

    2014-05-30

    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.

  19. 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.

  20. 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.

  1. High-performance of bare and Ti-doped α-MnO2 nanoparticles in catalyzing the Oxygen Reduction Reaction

    NASA Astrophysics Data System (ADS)

    Pargoletti, E.; Cappelletti, G.; Minguzzi, A.; Rondinini, S.; Leoni, M.; Marelli, M.; Vertova, A.

    2016-09-01

    Nanostructured MnO2 has unique electrocatalytic properties towards the Oxygen Reduction Reaction (ORR, the main cathodic reaction in metal-air devices), representing an excellent alternative to the expensive platinum. Herein, we report the hydrothermal synthesis of bare and 5% Ti-doped α-MnO2 nanoparticles using two different oxidizing agents, namely ammonium persulfate for MH_N samples and potassium permanganate for MH_K ones. The physico-chemical characterizations show that oxidant cations induce different structural, morphological and surface properties of the final powders. Hence, correlations between the different α-MnO2 characteristics and their electrocatalytic performances towards the ORR are drawn, highlighting the diverse effect even on the kinetic point of view. The ORR activity in alkaline media is examined by means of Staircase - Linear Sweep Voltammetry (S-LSV), using Gas Diffusion Electrode (GDE) as the air-cathode. The presence of these nanoparticles in the GDEs leads to a significant shift of the ORR onset potential (∼100 mV) towards less cathodic values, underlining the electrocatalytic efficiency of all the nanopowders. Furthermore, high exchange current densities (j0) are determined for GDEs with Ti-doped MnO2, comparable to the well-performing Pd45Pt5Sn50, and making it a promising material for the ORR.

  2. From two-dimension to one-dimension: the curvature effect of silicon-doped graphene and carbon nanotubes for oxygen reduction reaction.

    PubMed

    Zhang, Peng; Hou, Xiuli; Mi, Jianli; He, Yanqiong; Lin, Lin; Jiang, Qing; Dong, Mingdong

    2014-09-07

    For the goal of practical industrial development of fuel cells, inexpensive, sustainable, and highly efficient electrocatalysts for oxygen reduction reactions (ORR) are highly desirable alternatives to platinum (Pt) and other rare metals. In this work, based on density functional theory, silicon (Si)-doped carbon nanotubes (CNTs) and graphene as metal-free, low cost, and high-performance electrocatalysts for ORR are studied systematically. It is found that the curvature effect plays an important role in the adsorption and reduction of oxygen. The adsorption of O2 becomes weaker as the curvature varies from positive values (outside CNTs) to negative values (inside CNTs). The free energy change of the rate-determining step of ORR on the concave inner surface of Si-doped CNTs is smaller than that on the counterpart of Si-doped graphene, while that on the convex outer surface of Si-doped CNTs is larger than that on Si-doped graphene. Uncovering this new ORR mechanism on silicon-doped carbon electrodes is significant as the same principle could be applied to the development of various other metal-free efficient ORR catalysts for fuel cell applications.

  3. PT AND PT/NI "NEEDLE" ELETROCATALYSTS ON CARBON NANOTUBES WITH HIGH ACTIVITY FOR THE ORR

    SciTech Connect

    Colon-Mercado, H.

    2011-11-10

    Platinum and platinum/nickel alloy electrocatalysts supported on graphitized (gCNT) or nitrogen doped carbon nanotubes (nCNT) are prepared and characterized. Pt deposition onto carbon nanotubes results in Pt 'needle' formations that are 3.5 nm in diameter and {approx}100 nm in length. Subsequent Ni deposition and heat treatment results in PtNi 'needles' with an increased diameter. All Pt and Pt/Ni materials were tested as electrocatalysts for the oxygen reduction reaction (ORR). The Pt and Pt/Ni catalysts showed excellent performance for the ORR, with the heat treated PtNi/gCNT (1.06 mA/cm{sup 2}) and PtNi/nCNT (0.664 mA/cm{sup 2}) showing the highest activity.

  4. Functional Independent Scaling Relation for ORR/OER Catalysts

    SciTech Connect

    Christensen, Rune; Hansen, Heine A.; Dickens, Colin F.; Nørskov, Jens K.; Vegge, Tejs

    2016-10-11

    A widely used adsorption energy scaling relation between OH* and OOH* intermediates in the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), has previously been determined using density functional theory and shown to dictate a minimum thermodynamic overpotential for both reactions. Here, we show that the oxygen–oxygen bond in the OOH* intermediate is, however, not well described with the previously used class of exchange-correlation functionals. By quantifying and correcting the systematic error, an improved description of gaseous peroxide species versus experimental data and a reduction in calculational uncertainty is obtained. For adsorbates, we find that the systematic error largely cancels the vdW interaction missing in the original determination of the scaling relation. An improved scaling relation, which is fully independent of the applied exchange–correlation functional, is obtained and found to differ by 0.1 eV from the original. Lastly, this largely confirms that, although obtained with a method suffering from systematic errors, the previously obtained scaling relation is applicable for predictions of catalytic activity.

  5. Functional Independent Scaling Relation for ORR/OER Catalysts

    DOE PAGES

    Christensen, Rune; Hansen, Heine A.; Dickens, Colin F.; ...

    2016-10-11

    A widely used adsorption energy scaling relation between OH* and OOH* intermediates in the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), has previously been determined using density functional theory and shown to dictate a minimum thermodynamic overpotential for both reactions. Here, we show that the oxygen–oxygen bond in the OOH* intermediate is, however, not well described with the previously used class of exchange-correlation functionals. By quantifying and correcting the systematic error, an improved description of gaseous peroxide species versus experimental data and a reduction in calculational uncertainty is obtained. For adsorbates, we find that the systematic error largelymore » cancels the vdW interaction missing in the original determination of the scaling relation. An improved scaling relation, which is fully independent of the applied exchange–correlation functional, is obtained and found to differ by 0.1 eV from the original. Lastly, this largely confirms that, although obtained with a method suffering from systematic errors, the previously obtained scaling relation is applicable for predictions of catalytic activity.« less

  6. Paragenesis of palladium-cobalt nanoparticle in nitrogen-rich carbon nanotubes as bifunctional electrocatalyst for hydrogen evolution reaction and oxygen reduction reaction.

    PubMed

    Huang, Binbin; Chen, Liyu; Wang, Yan; Ouyang, Liuzhang; Ye, Jianshan

    2017-03-04

    Hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR) play important role in many energy conversion and storage systems. To accelerate the reaction process, efficient catalyst is always needed. The present work develops a facile process through pyrolysis for cosynthesis of palladium-cobalt nanoparticle supported over carbon nanotubes (Pd-CoCNTs), which exhibits superior catalytic activity for HER and enhance ORR performance. The Pd nanoparticles without agglomeration in diameters of 2-4 nm are uniformly distributed around the CoCNTs surface, while the inner Co particles are essential element in forming the framework of CoCNTs. Compared to the Pd free N-rich CoCNTs, Pd-CoCNTs possesses a more defective surface with lager electrochemical active surface area (ECSA), showing enhanced ORR activity, outstanding methanol tolerance and long-term stability in alkaline solution. At a low Pd loading of 0.0292 mg cm-2, Pd-CoCNTs takes an overpotential of 0.024 V and 0.215 V to catalyze HER and drive a current density of 50 mA cm-2 in acidic solution, respectively. The palladium nanoparticles on the CoCNTs surface are considered to be the highly active sites for HER by studying the controlled experiments, and it is easy to adjust the catalytic activity of Pd-CoCNTs from changing the concentration of Pd in catalyst. The proposed method provides a pathway for fabricating efficient bifunctional catalyst with controllable low content of precious metal.

  7. Transition metal/nitrogen dual-doped mesoporous graphene-like carbon nanosheets for the oxygen reduction and evolution reactions

    NASA Astrophysics Data System (ADS)

    Liu, Xiaobo; Amiinu, Ibrahim Saana; Liu, Shaojun; Cheng, Kun; Mu, Shichun

    2016-07-01

    The oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) have been considered as a key step in energy conversion processes. Here, a novel and simple Mg(OH)2 nanocasting method is adopted to fabricate Co and N co-doped porous graphene-like carbon nanosheets (Co@N-PGCS) by using chitosan as both carbon and N sources. The as-obtained Co@N-PGCS shows a mesopore-dominated structure as well as a high specific surface area (1716 cm2 g-1). As a bifunctional electrocatalyst towards both the ORR and OER, it shows favorable ORR performance compared with the commercial Pt/C catalyst with an onset potential of -0.075 V and a half-wave potential of -0.151 V in 0.1 M KOH solutions. Furthermore, it also displays considerable OER properties compared with commercial IrO2. The effective catalytic activity could originate from the introduction of transition metal species and few-layer mesoporous carbon structures.The oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) have been considered as a key step in energy conversion processes. Here, a novel and simple Mg(OH)2 nanocasting method is adopted to fabricate Co and N co-doped porous graphene-like carbon nanosheets (Co@N-PGCS) by using chitosan as both carbon and N sources. The as-obtained Co@N-PGCS shows a mesopore-dominated structure as well as a high specific surface area (1716 cm2 g-1). As a bifunctional electrocatalyst towards both the ORR and OER, it shows favorable ORR performance compared with the commercial Pt/C catalyst with an onset potential of -0.075 V and a half-wave potential of -0.151 V in 0.1 M KOH solutions. Furthermore, it also displays considerable OER properties compared with commercial IrO2. The effective catalytic activity could originate from the introduction of transition metal species and few-layer mesoporous carbon structures. Electronic supplementary information (ESI) available: The XPS fitted results, SEM and TEM images, the K-L equation, and some of the electrochemical

  8. Energy-Related Small Molecule Activation Reactions: Oxygen Reduction and Hydrogen and Oxygen Evolution Reactions Catalyzed by Porphyrin- and Corrole-Based Systems.

    PubMed

    Zhang, Wei; Lai, Wenzhen; Cao, Rui

    2017-02-22

    Globally increasing energy demands and environmental concerns related to the use of fossil fuels have stimulated extensive research to identify new energy systems and economies that are sustainable, clean, low cost, and environmentally benign. Hydrogen generation from solar-driven water splitting is a promising strategy to store solar energy in chemical bonds. The subsequent combustion of hydrogen in fuel cells produces electric energy, and the only exhaust is water. These two reactions compose an ideal process to provide clean and sustainable energy. In such a process, a hydrogen evolution reaction (HER), an oxygen evolution reaction (OER) during water splitting, and an oxygen reduction reaction (ORR) as a fuel cell cathodic reaction are key steps that affect the efficiency of the overall energy conversion. Catalysts play key roles in this process by improving the kinetics of these reactions. Porphyrin-based and corrole-based systems are versatile and can efficiently catalyze the ORR, OER, and HER. Because of the significance of energy-related small molecule activation, this review covers recent progress in hydrogen evolution, oxygen evolution, and oxygen reduction reactions catalyzed by porphyrins and corroles.

  9. Synthesis of Pd9Ru@Pt nanoparticles for oxygen reduction reaction in acidic electrolytes

    DOE PAGES

    Sun, Yu; Hsieh, Yu -Chi; Chang, Li -Chung; ...

    2014-11-22

    Nanoparticles of PdRu, Pd₃Ru, and Pd₉Ru are synthesized and impregnated on carbon black via a wet chemical reflux process. X-ray diffraction patterns of the as-synthesized samples, PdxRu/C (x=1/3/9), suggest succesful formation of alloy without presence of individual Pd and Ru nanoparticles. Images from transmission electron microscope confirm irregularly-shaped nanoparticles with average size below 3 nm. Analysis from extended X-ray absorption fine structure on both Pd and Ru K-edge absorption profiles indicate the Ru atoms are enriched on the surface of PdxRu/C. Among these samples, the Pd₉Ru/C exhibits the strongest electrocatalytic activity for oxygen reduction reaction (ORR) in an oxygen-saturated 0.1more » M aqueous HClO₄ solution. Subsequently, the Pd₉Ru/C undegoes Cu under potential deposition, followed by a galvanic displacement reaction to deposit a Pt monolayer on the Pd₉Ru surface (Pd₉Ru@Pt). The Pd₉Ru@Pt reveals better ORR performance than that of Pt, reaching a mass activity of 0.38 mA μg⁻¹ Pt, as compared to that of commercially available Pt nanoparticles (0.107 mA μg⁻¹ Pt). Thus, the mechanisms responsible for the ORR enhancement are attributed to the combined effects of lattice strain and ligand interaction. In addition, this core-shell Pd₉Ru@Pt electrocatalyst represents a substantial reduction in the amount of Pt consumption and raw material cost.« less

  10. Oxygen reduction reaction: A framework for success

    SciTech Connect

    Allendorf, Mark D.

    2016-05-06

    Oxygen reduction at the cathode of fuel cells typically requires a platinum-based material to catalyse the reaction, but lower-cost, more stable catalysts are sought. Here, an intrinsically conductive metal–organic framework based on cheaper elements is shown to be a durable, structurally well-defined catalyst for this reaction.

  11. Oxygen reduction reaction: A framework for success

    SciTech Connect

    Allendorf, Mark D.

    2016-05-06

    Oxygen reduction at the cathode of fuel cells typically requires a platinum-based material to catalyse the reaction, but lower-cost, more stable catalysts are sought. Here, an intrinsically conductive metal–organic framework based on cheaper elements is shown to be a durable, structurally well-defined catalyst for this reaction.

  12. Tuning electrocatalytic activity of Pt monolayer shell by bimetallic Ir-M (M=Fe, Co, Ni or Cu) cores for the oxygen reduction reaction

    SciTech Connect

    Kuttiyiel, Kurian A.; Choi, YongMan; Sasaki, Kotaro; Su, Dong; Hwang, Sun -Mi; Yim, Sung -Dae; Yang, Tae -Hyun; Park, Gu -Gon; Adzic, Radoslav R.

    2016-05-18

    Here, platinum monolayer electrocatalyst are known to exhibit excellent oxygen reduction reaction (ORR) activity depending on the type of substrate used. Here we demonstrate a relationship between the ORR electrocatalytic activity and the surface electronic structure of Pt monolayer shell induced by various IrM bimetallic cores (M=Fe, Co, Ni or Cu). The relationship is rationalized by comparing density functional theory calculations and experimental results. For an efficient Pt monolayer electrocatalyst, the core should induce sufficient contraction to the Pt shell leading to a downshift of the d-band center with respect to the Fermi level. Depending on the structure of the IrM, relative to that of pure Ir, this interaction not only alters the electronic and geometric structure but also induces segregation effects. Combined these effects significantly enhance the ORR activities of the Pt monolayer shell on bimetallic Ir cores electrocatalysts.

  13. MnO2 Nanofilms on Nitrogen-Doped Hollow Graphene Spheres as a High-Performance Electrocatalyst for Oxygen Reduction Reaction.

    PubMed

    Yu, Qiangmin; Xu, Jiaoxing; Wu, Chuxin; Zhang, Jianshuo; Guan, Lunhui

    2016-12-28

    Platinum is commonly chosen as an electrocatalyst used for oxygen reduction reaction (ORR). In this study, we report an active catalyst composed of MnO2 nanofilms grown directly on nitrogen-doped hollow graphene spheres, which exhibits high activity toward ORR with positive onset potential (0.94 V vs RHE), large current density (5.2 mA cm(-2)), and perfect stability. Significantly, when it was used as catalyst for air electrode, a zinc-air battery exhibited a high power density (82 mW cm(-2)) and specific capacities (744 mA h g(-1)) comparable to that with Pt/C (20 wt %) as air cathode. The enhanced activity is ascribed to the synergistic interaction between MnO2 and the doped hollow carbon nanomaterials. This easy and cheap method paves a way of synthesizing high-performance electrocatalysts for ORR.

  14. Tuning electrocatalytic activity of Pt monolayer shell by bimetallic Ir-M (M=Fe, Co, Ni or Cu) cores for the oxygen reduction reaction

    SciTech Connect

    Kuttiyiel, Kurian A.; Choi, YongMan; Sasaki, Kotaro; Su, Dong; Hwang, Sun -Mi; Yim, Sung -Dae; Yang, Tae -Hyun; Park, Gu -Gon; Adzic, Radoslav R.

    2016-05-18

    Here, platinum monolayer electrocatalyst are known to exhibit excellent oxygen reduction reaction (ORR) activity depending on the type of substrate used. Here we demonstrate a relationship between the ORR electrocatalytic activity and the surface electronic structure of Pt monolayer shell induced by various IrM bimetallic cores (M=Fe, Co, Ni or Cu). The relationship is rationalized by comparing density functional theory calculations and experimental results. For an efficient Pt monolayer electrocatalyst, the core should induce sufficient contraction to the Pt shell leading to a downshift of the d-band center with respect to the Fermi level. Depending on the structure of the IrM, relative to that of pure Ir, this interaction not only alters the electronic and geometric structure but also induces segregation effects. Combined these effects significantly enhance the ORR activities of the Pt monolayer shell on bimetallic Ir cores electrocatalysts.

  15. Tuning electrocatalytic activity of Pt monolayer shell by bimetallic Ir-M (M=Fe, Co, Ni or Cu) cores for the oxygen reduction reaction

    DOE PAGES

    Kuttiyiel, Kurian A.; Choi, YongMan; Sasaki, Kotaro; ...

    2016-05-18

    Here, platinum monolayer electrocatalyst are known to exhibit excellent oxygen reduction reaction (ORR) activity depending on the type of substrate used. Here we demonstrate a relationship between the ORR electrocatalytic activity and the surface electronic structure of Pt monolayer shell induced by various IrM bimetallic cores (M=Fe, Co, Ni or Cu). The relationship is rationalized by comparing density functional theory calculations and experimental results. For an efficient Pt monolayer electrocatalyst, the core should induce sufficient contraction to the Pt shell leading to a downshift of the d-band center with respect to the Fermi level. Depending on the structure of themore » IrM, relative to that of pure Ir, this interaction not only alters the electronic and geometric structure but also induces segregation effects. Combined these effects significantly enhance the ORR activities of the Pt monolayer shell on bimetallic Ir cores electrocatalysts.« less

  16. Electrochemical doping of three-dimensional graphene networks used as efficient electrocatalysts for oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Wang, Zhijuan; Cao, Xiehong; Ping, Jianfeng; Wang, Yixian; Lin, Tingting; Huang, Xiao; Ma, Qinglang; Wang, Fuke; He, Chaobin; Zhang, Hua

    2015-05-01

    Three-dimensional graphene networks (3DGNs) doped with a mono-heteroatom of N or B, or dual-heteroatoms of N and B were fabricated, which exhibit excellent oxygen reduction reaction (ORR) performance. Importantly, the onset potential and current density of N and B co-doped 3DGNs are comparable to those of the commercial Pt (30%)/C catalyst.Three-dimensional graphene networks (3DGNs) doped with a mono-heteroatom of N or B, or dual-heteroatoms of N and B were fabricated, which exhibit excellent oxygen reduction reaction (ORR) performance. Importantly, the onset potential and current density of N and B co-doped 3DGNs are comparable to those of the commercial Pt (30%)/C catalyst. Electronic supplementary information (ESI) available: Details of the N-3DGN, B-3DGN and NB-3DGN fabrication process. Description of characterization. Rotating disk electrode linear sweep voltammograms of 3DGN and Pt (30%)/C in O2-saturated 0.1 M KOH with various rotation rates at a scan rate of 5 mV s-1. Koutecky-Levich plots of 3DGN, Pt (30%)/C, N-3DGN, B-3DGN and NB-3DGN at different electrode potentials. See DOI: 10.1039/c4nr06631f

  17. Carbon nanotube-templated synthesis of covalent porphyrin network for oxygen reduction reaction.

    PubMed

    Hijazi, Ismail; Bourgeteau, Tiphaine; Cornut, Renaud; Morozan, Adina; Filoramo, Arianna; Leroy, Jocelyne; Derycke, Vincent; Jousselme, Bruno; Campidelli, Stéphane

    2014-04-30

    The development of innovative techniques for the functionalization of carbon nanotubes that preserve their exceptional quality, while robustly enriching their properties, is a central issue for their integration in applications. In this work, we describe the formation of a covalent network of porphyrins around MWNT surfaces. The approach is based on the adsorption of cobalt(II) meso-tetraethynylporphyrins on the nanotube sidewalls followed by the dimerization of the triple bonds via Hay-coupling; during the reaction, the nanotube acts as a template for the formation of the polymeric layer. The material shows an increased stability resulting from the cooperative effect of the multiple π-stacking interactions between the porphyrins and the nanotube and by the covalent links between the porphyrins. The nanotube hybrids were fully characterized and tested as the supported catalyst for the oxygen reduction reaction (ORR) in a series of electrochemical measurements under acidic conditions. Compared to similar systems in which monomeric porphyrins are simply physisorbed, MWNT-CoP hybrids showed a higher ORR activity associated with a number of exchanged electrons close to four, corresponding to the complete reduction of oxygen into water.

  18. Recent advances in the design of tailored nanomaterials for efficient oxygen reduction reaction

    DOE PAGES

    Lv, Haifeng; Li, Dongguo; Strmcnik, Dusan; ...

    2016-04-11

    In the past decade, polymer electrolyte membrane fuels (PEMFCs) have been evaluated for both automotive and stationary applications. One of the main obstacles for large scale commercialization of this technology is related to the sluggish oxygen reduction reaction that takes place on the cathode side of fuel cell. Consequently, ongoing research efforts are focused on the design of cathode materials that could improve the kinetics and durability. Majority of these efforts rely on novel synthetic approaches that provide control over the structure, size, shape and composition of catalytically active materials. This article highlights the most recent advances that have beenmore » made to tailor critical parameters of the nanoscale materials in order to achieve more efficient performance of the oxygen reduction reaction (ORR).« less

  19. Oxygen reduction reaction on palladium-cobalt alloy catalysts for polymer electrolyte fuel cells

    NASA Astrophysics Data System (ADS)

    Oishi, Kentaro

    The Oxygen Reduction Reaction (ORR) activity in acid medium on Pd-Co was studied in this work. The catalysts were synthesized by two techniques; physical vapor deposition technique and ultrasonic spray reaction technique. The last technique was developed for the first time in our laboratory for the supported electro catalyst preparation and direct deposition onto the carbon paper or gas diffusion electrode the for PEMFC applications. The electrochemical properties such as the amount of hydrogen adsorption/desorption, the oxide formation/reduction of Pd-Co alloy catalyst have not been sufficiently studied before. Therefore these electrochemical properties were investigated by using the Pd-Co thin films prepared by sputtering method. A thin film catalyst cannot be directly used as an electrode of working PEMFCs, however the sputtering method is very useful since the chemical composition of alloy and surface area of the electrode can be controlled easily. Thus the fundamental electrochemical properties such as the amount of hydrogen adsorption/desorption, oxide formation/reduction and oxide reduction peak position on thin films of Pd-Co alloy, Pd and Pt catalysts were determined and their correlations to ORR catalytic activities in acid medium were studied. Enhancements of the catalytic activities for ORR by Pd-Co binary alloys were found to be in agreement with results obtained in previous studies. Ultrasonic spray reaction method was developed for the first time in our laboratory for carbon supported nano-scale catalyst for PEMFC application. Fine catalyst particles supported on high surface area carbon powder are required to apply the catalyst as the PEMFC cathode materials for the commercialization, but none of the studies done before were able to successfully obtain the Pd-Co fine particles which are comparable with the existing carbon supported platinum catalyst (ϕ2-4nm). Therefore the establishment of the catalyst synthesis method for Pd-Co fine particles are

  20. Roles of Fe-Nx and Fe-Fe3C@C Species in Fe-N/C Electrocatalysts for Oxygen Reduction Reaction.

    PubMed

    Kim, Jae Hyung; Sa, Young Jin; Jeong, Hu Young; Joo, Sang Hoon

    2017-03-22

    Iron and nitrogen codoped carbons (Fe-N/C) have emerged as promising nonprecious metal catalysts for the oxygen reduction reaction (ORR). While Fe-Nx sites have been widely considered as active species for Fe-N/C catalysts, very recently, iron and/or iron carbide encased with carbon shells (Fe-Fe3C@C) has been suggested as a new active site for the ORR. However, most of synthetic routes to Fe-N/C catalysts involve high-temperature pyrolysis, which unavoidably yield both Fe-Nx and Fe-Fe3C@C species, hampering the identification of exclusive role of each species. Herein, in order to establish the respective roles of Fe-Nx and Fe-Fe3C@C sites we rationally designed model catalysts via the phase conversion reactions of Fe3O4 nanoparticles supported on carbon nanotubes. The resulting catalysts selectively contained Fe-Nx, Fe-Fe3C@C, and N-doped carbon (C-Nx) sites. It was revealed that Fe-Nx sites dominantly catalyze ORR via 4-electron (4 e(-)) pathway, exerting a major role for high ORR activity, whereas Fe-Fe3C@C sites mainly promote 2 e(-) reduction of oxygen followed by 2 e(-) peroxide reduction, playing an auxiliary role.

  1. A novel cobalt tetranitrophthalocyanine/graphene composite assembled by an in situ solvothermal synthesis method as a highly efficient electrocatalyst for the oxygen reduction reaction in alkaline medium.

    PubMed

    Lv, Guojun; Cui, Lili; Wu, Yanying; Liu, Ying; Pu, Tao; He, Xingquan

    2013-08-21

    A novel micro/nano-composite, based on cobalt(II) tetranitrophthalocyanine (CoTNPc) grown on poly(sodium-p-styrenesulfonate) modified graphene (PGr), as a non-noble-metal catalyst for the oxygen reduction reaction (ORR), is fabricated by an in situ solvothermal synthesis method. The CoTNPc/PGr is characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), ultraviolet-visible (UV-vis) absorption spectroscopy, Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS), respectively. The electrocatalytic activity of the CoTNPc/PGr composite toward the ORR is evaluated using cyclic voltammetry and linear sweep voltammetry methods. The CoTNPc/PGr composite exhibits an unexpected, surprisingly high ORR activity compared to CoTNPc or PGr. The onset potential for ORR on CoTNPc/PGr is found to be around -0.10 V vs. SCE in 0.1 M NaOH solution, which is 30 mV and 70 mV more positive than that on PGr and CoTNPc, respectively. The peak current density on CoTNPc/PGr is about 2 times than that on PGr and CoTNPc, respectively. Rotating disk electrode (RDE) measurements reveal that the ORR mechanism is nearly via a four-electron pathway on CoTNPc/PGr. The current density for ORR on CoTNPc/PGr still remains 69.9% of its initial value after chronoamperometric measurements for 24 h. Pt/C catalyst, on the other hand, only retains 13.3% of its initial current. The peak potential shifts slightly and current barely changes when 3 M methanol is added. The fabricated composite catalyst for ORR displays high activity, good stability and excellent tolerance to the crossover effect, which may be used as a promising Pt-free catalyst in alkaline direct methanol fuel cells (DMFCs).

  2. Evidences of the presence of different types of active sites for the oxygen reduction reaction with Fe/N/C based catalysts

    NASA Astrophysics Data System (ADS)

    Pérez-Alonso, Francisco J.; Domínguez, Carlota; Al-Thabaiti, Shaeel A.; Al-Youbi, Abdulrahman O.; Abdel Salam, Mohamed; Alshehri, Abdulmohsen A.; Retuerto, María; Peña, Miguel A.; Rojas, Sergio

    2016-09-01

    Fe/N/C catalysts are very active for the oxygen reduction reaction (ORR); however, the nature of the active site(s) is not fully understood. In this work, we study the performance of different types of N/C and Fe/N/C catalysts for the ORR, and the effect of the addition of NaCN. Phthalocyanine and graphene have been studied as model metal-free catalysts for the ORR. Fe-phthalocyanine (FePhcy), Fe-phthalocyanine dispersed in graphene (FePhcy/G) and Fe/N/G, have been used as model Fe-containing catalysts. FePhcy and FePhcy/G only contain Fe atoms coordinated to 4 nitrogen atoms. On the other hand, different species such as Fe-Nx and Fe3C coexist in Fe/N/G. In addition, Csbnd C ensembles are present in the graphene present in FePhcy/G and Fe/N/G. The ORR activity is characteristic of each catalyst, being the highest for the catalysts containing FeN4 ensembles. The addition of CN- results in the selective poisoning of the Fe-containing sites but it does not suppress the ORR activity of the Graphene containing samples. In-situ infrared spectroscopy studies during the ORR reveal that CN- poisoning of the Fe sites is reversible, desorbing at potentials less positive than ca. 600 mV. As a consequence, the ORR activity of the Fe-containing sites is recovered gradually.

  3. Surface segregation effects in electrocatalysis: Kinetics ofoxygen reduction reaction on polycrystalline Pt3Ni alloy surfaces

    SciTech Connect

    Stamenkovic, V.; Schmidt, T.J.; Ross, P.N.; Markovic, N.M.

    2002-11-01

    Effects of surface segregation on the oxygen reduction reaction (ORR) have been studied on a polycrystalline Pt3Ni alloy in acid electrolyte using ultra high vacuum (UHV) surface sensitive probes and the rotating ring disk electrode (RRDE) method. Preparation, modification and characterization of alloy surfaces were done in ultra high vacuum (UHV). Depending on the preparation method, two different surface compositions of the Pt3Ni alloy are produced: a sputtered surface with 75 % Pt and an annealed surface (950 K ) with 100 % Pt. The latter surface is designated as the 'Pt-skin' structure, and is a consequence of surface segregation, i.e., replacement of Ni with Pt atoms in the first few atomic layers. Definitive surface compositions were established by low energy ion scattering spectroscopy (LEISS). The cyclic voltammetry of the 'Pt-skin' surface as well as the pseudocapacitance in the hydrogen adsorption/desorption potential region is similar to a polycrystalline Pt electrode. Activities of ORR on Pt3Ni alloy surfaces were compared to polycrystalline Pt in 0.1M HClO4 electrolyte for the observed temperature range of 293 < T < 333 K. The order of activities at 333 K was: 'Pt-skin' > Pt3Ni (75% Pt) > Pt with the maximum catalytic enhancement obtained for the 'Pt-skin' being 4 times that for pure Pt. Catalytic improvement of the ORR on Pt3Ni and 'Pt-skin' surfaces was assigned to the inhibition of Pt-OHad formation (on Pt sites) versus polycrystalline Pt. Production of H2O2 on both surfaces were similar compared to the pure Pt. Kinetic analyses of RRDE data confirmed that kinetic parameters for the ORR on the Pt3Ni and 'Pt-skin' surfaces are the same as on pure Pt: reaction order, m=1, two identical Tafel slopes, activation energy, {approx} 21-25 kJ/mol. Therefore the reaction mechanism on both Pt3Ni and 'Pt-skin' surfaces is the same as one proposed for pure Pt i.e. 4e{sup -} reduction pathway.

  4. 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.

  5. Size-Controlled Synthesis of Sub-10 nm PtNi3 Alloy Nanoparticles and their Unusual Volcano-Shaped Size Effect on ORR Electrocatalysis.

    PubMed

    Gan, Lin; Rudi, Stefan; Cui, Chunhua; Heggen, Marc; Strasser, Peter

    2016-06-01

    Dealloyed Pt bimetallic core-shell catalysts derived from low-Pt bimetallic alloy nanoparticles (e.g, PtNi3 ) have recently shown unprecedented activity and stability on the cathodic oxygen reduction reaction (ORR) under realistic fuel cell conditions and become today's catalyst of choice for commercialization of automobile fuel cells. A critical step toward this breakthrough is to control their particle size below a critical value (≈10 nm) to suppress nanoporosity formation and hence reduce significant base metal (e.g., Ni) leaching under the corrosive ORR condition. Fine size control of the sub-10 nm PtNi3 nanoparticles and understanding their size dependent ORR electrocatalysis are crucial to further improve their ORR activity and stability yet still remain unexplored. A robust synthetic approach is presented here for size-controlled PtNi3 nanoparticles between 3 and 10 nm while keeping a constant particle composition and their size-selected growth mechanism is studied comprehensively. This enables us to address their size-dependent ORR activities and stabilities for the first time. Contrary to the previously established monotonic increase of ORR specific activity and stability with increasing particle size on Pt and Pt-rich bimetallic nanoparticles, the Pt-poor PtNi3 nanoparticles exhibit an unusual "volcano-shaped" size dependence, showing the highest ORR activity and stability at the particle sizes between 6 and 8 nm due to their highest Ni retention during long-term catalyst aging. The results of this study provide important practical guidelines for the size selection of the low Pt bimetallic ORR electrocatalysts with further improved durably high activity.

  6. Porous carbon supported Fe-N-C composite as an efficient electrocatalyst for oxygen reduction reaction in alkaline and acidic media

    NASA Astrophysics Data System (ADS)

    Liu, Baichen; Huang, Binbin; Lin, Cheng; Ye, Jianshan; Ouyang, Liuzhang

    2017-07-01

    In recent years, non-precious metal electrocatalysts for oxygen reduction reaction (ORR) have attracted tremendous attention due to their high catalytic activity, long-term stability and excellent methanol tolerance. Herein, the porous carbon supported Fe-N-C catalysts for ORR were synthesized by direct pyrolysis of ferric chloride, 6-Chloropyridazin-3-amine and carbon black. Variation of pyrolysis temperature during the synthesis process leads to the difference in ORR catalytic activity. High pyrolysis temperature is beneficial to the formation of the ;N-Fe; active sites and high electrical conductivity, but the excessive temperature will cause the decomposition of nitrogen-containing active sites, which are revealed by Raman, TGA and XPS. A series of synthesis and characterization experiments with/without nitrogen or iron in carbon black indicate that the coordination of iron and nitrogen plays a crucial role in achieving excellent ORR performances. Electrochemical test results show that the catalyst pyrolyzed at 800 °C (Fe-N-C-800) exhibits excellent ORR catalytic activity, better methanol tolerance and higher stability compared with commercial Pt/C catalyst in both alkaline and acidic conditions.

  7. Bifunctional enhancement of oxygen reduction reaction activity on Ag catalysts due to water activation on LaMnO3 supports in alkaline media

    PubMed Central

    Park, Shin-Ae; Lee, Eun-Kyung; Song, Hannah; Kim, Yong-Tae

    2015-01-01

    Ag is considered to be one of the best candidates for oxygen reduction reaction electrocatalysts in alkaline media for application in various electrochemical energy devices. In this study, we demonstrate that water activation is a key factor in enhancing the ORR activity in alkaline media, unlike in acid environments. Ag supported on LaMnO3 having a high oxophilicity showed a markedly higher ORR activity than that on carbon with inert surfaces. Through various electrochemical tests, it was revealed that the origin of the enhanced ORR activity of Ag/LaMnO3 is the bifunctional effect mainly due to the water activation at the interface between Ag and LaMnO3. Furthermore, the ligand effect due to the charge transfer from Mn to Ag leads to the enhancement of both oxygen activation on Ag and water activation on Mn sites, and hence, an improvement in the ORR activity of Ag/LaMnO3. On the other hand, the strain effect based on the fine structure variation in the lattice was negligible. We therefore suggest that the employment of a co-catalyst or support with highly oxophilic nature and the maximization of the interface between catalyst and support should be considered in the design of electrocatalysts for the ORR in alkaline media. PMID:26310526

  8. Active Site Structures in Nitrogen-Doped Carbon-Supported Cobalt Catalysts for the Oxygen Reduction Reaction.

    PubMed

    Qian, Yingdan; Liu, Zheng; Zhang, Hui; Wu, Ping; Cai, Chenxin

    2016-12-07

    The catalytic mechanism and the nature of active sites are revealed for the oxygen reduction reaction (ORR) with new non-noble-metal nitrogen-doped carbon-supported transition-metal catalysts (metal-N-C catalyst). Specifically, new nitrogen-doped carbon-supported cobalt catalysts (Co-N-C catalysts) are made by pyrolyzing various ratios of the nitrogen-atom rich heterocycle compound, 1-ethyl-3-methyl imidazolium dicyanamide (EMIM-dca) and cobalt salt (Co(NO3)2). The ORR activity (JK at 0.8 V vs RHE, in 0.1 M KOH solution) of a typical catalyst in this family, Co15-N-C800, is 8.25 mA/mg, which is much higher than the ORR activity values of N-C catalysts (0.41 mA/mg). The active site in the catalyst is found to be the Co-N species, which is most likely in the form of Co2N. Metallic cobalt (Co) particles, Co3C species, and N-C species are not catalytically active sites, nor do these moieties interact with the Co-N active sites during the catalysis of the ORR. Increasing the Co salt content during the synthesis favors the formation of Co-N active sites in the final catalyst. Higher pyrolysis temperatures (e.g., a temperature higher than 800 °C) do not favor the formation of the Co-N active sites, but cause the formed Co-N active sites to decompose, which, therefore, leads to a lower catalytic activity. This reveals that the control of the parameters that affect the final structure is critical to catalyst performance and, therefore, the effective development of high-performance heteroatom-doped non-noble-metal ORR catalysts.

  9. H2O2 detection analysis of oxygen reduction reaction on cathode and anode catalysts for polymer electrolyte fuel cells

    NASA Astrophysics Data System (ADS)

    Kishi, Akira; Shironita, Sayoko; Umeda, Minoru

    2012-01-01

    The generation percentage of H2O2 during oxygen reduction reaction (ORR) at practical powder electrocatalysts was evaluated using a scanning electrochemical microscope (SECM). We employed a porous microelectrode that contains electrocatalysts, namely, Pt/C, Pt-Co/C, and Pt-Ru/C as the oxygen reduction electrode of the SECM, and the Pt microelectrode was used as the H2O2 detector. First, the H2O2 generation amount at Pt/Cs was measured by changing the Pt loading amount. A Pt/C with a higher Pt loading has a higher ORR activity and generates a larger amount of H2O2. However, the percentage of H2O2 generated with respect to the ORR is the same regardless of the Pt loading amount. Next, H2O2 generation is markedly suppressed at the Pt-Co/C and Pt-Ru/C in the potential ranges of practical fuel cell cathode and anode, respectively. This explains that the Pt-Co/C is effective when used as a cathode, and the anode Pt-Ru/C enables the reduction of the H2O2 generation even if O2 crossleak occurs in the practical polymer electrolyte fuel cell.

  10. 2D molybdenum disulphide (2D-MoS2) modified electrodes explored towards the oxygen reduction reaction.

    PubMed

    Rowley-Neale, Samuel J; Fearn, Jamie M; Brownson, Dale A C; Smith, Graham C; Ji, Xiaobo; Banks, Craig E

    2016-08-21

    Two-dimensional molybdenum disulphide nanosheets (2D-MoS2) have proven to be an effective electrocatalyst, with particular attention being focused on their use towards increasing the efficiency of the reactions associated with hydrogen fuel cells. Whilst the majority of research has focused on the Hydrogen Evolution Reaction (HER), herein we explore the use of 2D-MoS2 as a potential electrocatalyst for the much less researched Oxygen Reduction Reaction (ORR). We stray from literature conventions and perform experiments in 0.1 M H2SO4 acidic electrolyte for the first time, evaluating the electrochemical performance of the ORR with 2D-MoS2 electrically wired/immobilised upon several carbon based electrodes (namely; Boron Doped Diamond (BDD), Edge Plane Pyrolytic Graphite (EPPG), Glassy Carbon (GC) and Screen-Printed Electrodes (SPE)) whilst exploring a range of 2D-MoS2 coverages/masses. Consequently, the findings of this study are highly applicable to real world fuel cell applications. We show that significant improvements in ORR activity can be achieved through the careful selection of the underlying/supporting carbon materials that electrically wire the 2D-MoS2 and utilisation of an optimal mass of 2D-MoS2. The ORR onset is observed to be reduced to ca. +0.10 V for EPPG, GC and SPEs at 2D-MoS2 (1524 ng cm(-2) modification), which is far closer to Pt at +0.46 V compared to bare/unmodified EPPG, GC and SPE counterparts. This report is the first to demonstrate such beneficial electrochemical responses in acidic conditions using a 2D-MoS2 based electrocatalyst material on a carbon-based substrate (SPEs in this case). Investigation of the beneficial reaction mechanism reveals the ORR to occur via a 4 electron process in specific conditions; elsewhere a 2 electron process is observed. This work offers valuable insights for those wishing to design, fabricate and/or electrochemically test 2D-nanosheet materials towards the ORR.

  11. Highly uniform distribution of Pt nanoparticles on N-doped hollow carbon spheres with enhanced durability for oxygen reduction reaction

    DOE PAGES

    Shi, Qiurong; Zhu, Chengzhou; Engelhard, Mark H.; ...

    2017-01-19

    Here, carbon-supported Pt nanostructures currently exhibited great potential in polymer electrolyte membrane fuel cells. Nitrogen-doped hollow carbon spheres (NHCSs) with extra low density and high specific surface area are promising carbon support for loading Pt NPs. The doped heteroatom of nitrogen could not only contribute to the active activity for the oxygen reduction reaction (ORR), but also shows a strong interaction with Pt NPs for entrapping them from dissolution/migration. This synergetic effect/interaction resulted in the uniform dispersion and strong combination of the Pt NPs on the carbon support and thus play a significant role in hindering the degradation of themore » catalytic activities of Pt NPs. As expected, the as-obtained Pt/NHCSs displayed improved catalytic activity and superior durability toward ORR.« less

  12. Highly uniform distribution of Pt nanoparticles on N-doped hollow carbon spheres with enhanced durability for oxygen reduction reaction

    SciTech Connect

    Shi, Qiurong; Zhu, Chengzhou; Engelhard, Mark H.; Du, Dan; Lin, Yuehe

    2017-01-01

    Carbon-supported Pt nanostructures currently exhibited great potential in polymer electrolyte membrane fuel cells. Nitrogen-doped hollow carbon spheres (NHCSs) with extra low density and high specific surface area are promising carbon support for loading Pt NPs. The doped heteroatom of nitrogen could not only contribute to the active activity for the oxygen reduction reaction (ORR), but also shows a strong interaction with Pt NPs for entrapping them from dissolution/migration. This synergetic effect/interaction resulted in the uniform dispersion and strong combination of the Pt NPs on the carbon support and thus play a significant role in hindering the degradation of the catalytic activities of Pt NPs. As expected, the as-obtained Pt/NHCSs displayed improved catalytic activity and superior durability toward ORR.

  13. Surface spectators and their role in relationships between activity and selectivity of the oxygen reduction reaction in acid environments.

    SciTech Connect

    Ciapina, Eduardo G.; Lopes, Pietro P.; Subbaraman, Ram; Ticianelli, Edson A.; Stamenkovic, Vojislav; Strmcnik, Dusan; Markovic, Nenad M.

    2015-11-01

    We use the rotating ring disk (RRDE) method to study activity-selectivity relationships for the oxygen reduction reaction (ORR) on Pt(111) modified by various surface coverages of adsorbed CNad (ΘCNad). The results demonstrate that small variations in ΘCNad have dramatic effect on the ORR activity and peroxide production, resulting in “volcano-like” dependence with an optimal surface coverage of ΘCNad = 0.3 ML. These relationships can be simply explained by balancing electronic and ensemble effects of co-adsorbed CNad and adsorbed spectator species from the supporting electrolytes, without the need for intermediate adsorption energy arguments. Although this study has focused on the Pt(111)-CNad/H2SO4 interface, the results and insight gained here are invaluable for controlling another dimension in the properties of electrochemical interfaces.

  14. Fe-N-doped carbon catalysts prepared by hybrid PECVD/sputtering system for oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Hotozuka, Kozue; Yoshie, Ryo; Murata, Hidenobu; Tateno, Akira; Ito, Gen; Kawaguchi, Norihito; Matsuo, Takahiro; Ito, Hitomi; Kinoshita, Ikuo; Tachibana, Masaru

    2017-07-01

    A hybrid plasma-enhanced chemical vapor deposition (PECVD)/sputtering system was developed to prepare iron (Fe)-nitrogen (N)-doped carbon catalysts for oxygen reduction reaction (ORR). This hybrid system combines PECVD effective for the synthesis of nanocarbons with sputtering technique for the doping of metals such as Fe where the amount of the doping can be independently controlled during synthesizing nanocarbons. By using this system, Fe-N-doped carbon catalysts are directly synthesized on carbon papers which have been widely used as a gas diffusion layer in fuel cells. The synthesized catalysts with carbon papers exhibit high ORR activity. This is attributed to Fe-N coordination bonds which are stably formed in the synthesized catalysts.

  15. 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.

  16. A metal-free bifunctional electrocatalyst for oxygen reduction and oxygen evolution reactions

    NASA Astrophysics Data System (ADS)

    Zhang, Jintao; Zhao, Zhenghang; Xia, Zhenhai; Dai, Liming

    2015-05-01

    The oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are traditionally carried out with noble metals (such as Pt) and metal oxides (such as RuO2 and MnO2) as catalysts, respectively. However, these metal-based catalysts often suffer from multiple disadvantages, including high cost, low selectivity, poor stability and detrimental environmental effects. Here, we describe a mesoporous carbon foam co-doped with nitrogen and phosphorus that has a large surface area of ˜1,663 m2 g-1 and good electrocatalytic properties for both ORR and OER. This material was fabricated using a scalable, one-step process involving the pyrolysis of a polyaniline aerogel synthesized in the presence of phytic acid. We then tested the suitability of this N,P-doped carbon foam as an air electrode for primary and rechargeable Zn-air batteries. Primary batteries demonstrated an open-circuit potential of 1.48 V, a specific capacity of 735 mAh gZn-1 (corresponding to an energy density of 835 Wh kgZn-1), a peak power density of 55 mW cm-2, and stable operation for 240 h after mechanical recharging. Two-electrode rechargeable batteries could be cycled stably for 180 cycles at 2 mA cm-2. We also examine the activity of our carbon foam for both OER and ORR independently, in a three-electrode configuration, and discuss ways in which the Zn-air battery can be further improved. Finally, our density functional theory calculations reveal that the N,P co-doping and graphene edge effects are essential for the bifunctional electrocatalytic activity of our material.

  17. Individual Reactions of Permanganate & Various Reductants

    SciTech Connect

    Gauger, Amber M.; Hallen, Richard T. )

    2000-11-01

    Tank waste on the Hanford Site contains radioactive elements that need to be removed from solution prior to disposal. One effective way to do this is to precipitate the radioactive elements with manganese solids, produced by permanganate oxidation. When added to tank waste, the permanganate, Mn(VII), reacts quickly producing manganese (IV) dioxide precipitate. Because of the speed of reaction it is difficult to tell what exactly is happening. Individual reactions using non-radioactive reductants found in the tanks were done to determine reaction kinetics, what permanganate was reduced to, and what oxidation products were formed. In this project sodium formate, sodium nitrite, glycolic acid, glycine, and sodium oxalate were studied using various concentrations of reductant in alkaline sodium hydroxide solutions. It was determined that formate reacted the quickest, followed by glycine and glycolic acid. Oxalate and nitrite did not appear to react with the permanganate solutions. The formate reactions quickly reduced permanganate, Mn(VII), to manganate, Mn(VI), and then to manganese (IV) dioxide. These reactions oxidized formate to carbonate and water. The glycolic acid was oxidized slower producing oxalate, water, and manganate, which would disproportionate to permanganate and manganese (IV) dioxide solids. The rate at which Mn(VI) disproportionates is usually slower than the rate at which Mn(VII) is reduced to Mn(VI), however in this case the rates were about equal. The glycine reactions formed some ammonia in solution, oxalate, and water. They reacted similar to the glycolic acid reactions, producing manganese dioxide precipitate before the solution turned totally green from Mn(VI). The formate reactions consumed one mole of hydroxide for every 3 moles of formate, while the glycolic acid and glycine reactions consumed 7 moles of hydroxide for every 3 moles of reductant. These reactions should help to determine the majority of products found in mixtures of solutions.

  18. Particle-size effect of nanoscale platinum catalysts in oxygen reduction reaction: an electrochemical and 195Pt EC-NMR study.

    PubMed

    Yano, Hiroshi; Inukai, Junji; Uchida, Hiroyuki; Watanabe, Masahiro; Babu, Panakkattu K; Kobayashi, Takeshi; Chung, Jong Ho; Oldfield, Eric; Wieckowski, Andrzej

    2006-11-14

    Oxygen reduction reaction (ORR) measurements and (195)Pt electrochemical nuclear magnetic resonance (EC-NMR) spectroscopy were combined to study a series of carbon-supported platinum nanoparticle electrocatalysts (Pt/CB) with average diameters in the range of roughly 1-5 nm. ORR rate constants and H(2)O(2) yields evaluated from hydrodynamic voltammograms did not show any particle size dependency. The apparent activation energy of 37 kJ mol(-1), obtained for the ORR rate constant, was identical to that obtained for bulk platinum electrodes. Pt/CB catalysts on Nafion produced only 0.7-1% of H(2)O(2), confirming that the direct four-electron reduction of O(2) to H(2)O is the predominant reaction. NMR spectral features showed characteristic size dependence, and the line shapes were reproduced by using the layer-deconvolution model. Namely, the variations in the NMR spectra with particle size can be explained as due to the combined effect of the layer-by-layer variation of the s-type and d-type local density of states. However, the surface peak position of (195)Pt NMR spectra and the spin-lattice relaxation time of surface platinum atoms showed practically no change with the particle size variation. We conclude that there is a negligible difference in the surface electronic properties of these Pt/CB catalysts due to size variations and therefore, the ORR activities are not affected by the differences in the particle size.

  19. In situ probing of the active site geometry of ultrathin nanowires for the oxygen reduction reaction

    SciTech Connect

    Liu, Haiqing; Wong, Stanislaus S.; An, Wei; Li, Yuanyuan; Frenkel, Anatoly I.; Sasaki, Kotaro; Koenigsmann, Christopher; Su, Dong; Anderson, Rachel M.; Crooks, Richard M.; Adzic, Radoslav R.; Liu, Ping

    2015-09-24

    To create truly effective electrocatalysts for the cathodic reaction governing proton exchange membrane fuel cells (PEMFC), namely the oxygen reduction reaction (ORR), necessitates an accurate and detailed structural understanding of these electrocatalysts, especially at the nanoscale, and to precisely correlate that structure with demonstrable performance enhancement. To address this key issue, we have combined and interwoven theoretical calculations with experimental, spectroscopic observations in order to acquire useful structural insights into the active site geometry with implications for designing optimized nanoscale electrocatalysts with rationally predicted properties. Specifically, we have probed ultrathin (~2 nm) core–shell Pt~Pd9Au nanowires, which have been previously shown to be excellent candidates for ORR in terms of both activity and long-term stability, from the complementary perspectives of both DFT calculations and X-ray absorption spectroscopy (XAS). The combination and correlation of data from both experimental and theoretical studies has revealed for the first time that the catalytically active structure of our ternary nanowires can actually be ascribed to a PtAu~Pd configuration, comprising a PtAu binary shell and a pure inner Pd core. Moreover, we have plausibly attributed the resulting structure to a specific synthesis step, namely the Cu underpotential deposition (UPD) followed by galvanic replacement with Pt. Thus, the fundamental insights gained into the performance of our ultrathin nanowires from our demonstrated approach will likely guide future directed efforts aimed at broadly improving upon the durability and stability of nanoscale electrocatalysts in general.

  20. In situ probing of the active site geometry of ultrathin nanowires for the oxygen reduction reaction

    DOE PAGES

    Liu, Haiqing; Wong, Stanislaus S.; An, Wei; ...

    2015-09-24

    To create truly effective electrocatalysts for the cathodic reaction governing proton exchange membrane fuel cells (PEMFC), namely the oxygen reduction reaction (ORR), necessitates an accurate and detailed structural understanding of these electrocatalysts, especially at the nanoscale, and to precisely correlate that structure with demonstrable performance enhancement. To address this key issue, we have combined and interwoven theoretical calculations with experimental, spectroscopic observations in order to acquire useful structural insights into the active site geometry with implications for designing optimized nanoscale electrocatalysts with rationally predicted properties. Specifically, we have probed ultrathin (~2 nm) core–shell Pt~Pd9Au nanowires, which have been previously shownmore » to be excellent candidates for ORR in terms of both activity and long-term stability, from the complementary perspectives of both DFT calculations and X-ray absorption spectroscopy (XAS). The combination and correlation of data from both experimental and theoretical studies has revealed for the first time that the catalytically active structure of our ternary nanowires can actually be ascribed to a PtAu~Pd configuration, comprising a PtAu binary shell and a pure inner Pd core. Moreover, we have plausibly attributed the resulting structure to a specific synthesis step, namely the Cu underpotential deposition (UPD) followed by galvanic replacement with Pt. Thus, the fundamental insights gained into the performance of our ultrathin nanowires from our demonstrated approach will likely guide future directed efforts aimed at broadly improving upon the durability and stability of nanoscale electrocatalysts in general.« less

  1. In Situ Probing of the Active Site Geometry of Ultrathin Nanowires for the Oxygen Reduction Reaction.

    PubMed

    Liu, Haiqing; An, Wei; Li, Yuanyuan; Frenkel, Anatoly I; Sasaki, Kotaro; Koenigsmann, Christopher; Su, Dong; Anderson, Rachel M; Crooks, Richard M; Adzic, Radoslav R; Liu, Ping; Wong, Stanislaus S

    2015-10-07

    To create truly effective electrocatalysts for the cathodic reaction governing proton exchange membrane fuel cells (PEMFC), namely the oxygen reduction reaction (ORR), necessitates an accurate and detailed structural understanding of these electrocatalysts, especially at the nanoscale, and to precisely correlate that structure with demonstrable performance enhancement. To address this key issue, we have combined and interwoven theoretical calculations with experimental, spectroscopic observations in order to acquire useful structural insights into the active site geometry with implications for designing optimized nanoscale electrocatalysts with rationally predicted properties. Specifically, we have probed ultrathin (∼2 nm) core-shell Pt∼Pd9Au nanowires, which have been previously shown to be excellent candidates for ORR in terms of both activity and long-term stability, from the complementary perspectives of both DFT calculations and X-ray absorption spectroscopy (XAS). The combination and correlation of data from both experimental and theoretical studies has revealed for the first time that the catalytically active structure of our ternary nanowires can actually be ascribed to a PtAu∼Pd configuration, comprising a PtAu binary shell and a pure inner Pd core. Moreover, we have plausibly attributed the resulting structure to a specific synthesis step, namely the Cu underpotential deposition (UPD) followed by galvanic replacement with Pt. Hence, the fundamental insights gained into the performance of our ultrathin nanowires from our demonstrated approach will likely guide future directed efforts aimed at broadly improving upon the durability and stability of nanoscale electrocatalysts in general.

  2. Enhancing stability of octahedral PtNi nanoparticles for oxygen reduction reaction by halide treatment

    NASA Astrophysics Data System (ADS)

    Choi, Juhyuk; Lee, Youhan; Kim, Jihan; Lee, Hyunjoo

    2016-03-01

    Because a reduction in the amount of Pt catalysts is essential for the commercialization of fuel cells, various approaches have been tested to maximize the mass activity of Pt-based catalysts. Among these, the most successful results so far were obtained using shaped PtNi alloy nanoparticles, preferably with PtNi(111) facets. However, these nanoparticles typically suffer from much lower activity after the durability tests due to the leaching out of the surface Ni during the oxygen reduction reaction (ORR), which leads to the disappearance of the activity-enhancing effect caused by electronic structure modification. Here, we showed that halide treatment of the octahedral PtNi nanoparticles could significantly enhance their durability. Halides are adsorbed on surface Ni more strongly than on surface Pt, and the surface halides are found to preserve the surface Ni that induces the ORR activity enhancement. Especially, Br can preserve the surface Ni effectively. Durability testing by repeating cyclic voltammetry 10,000 times in the 0.6-1.1 V range showed that the mass activity decreased by 52.6% for the as-prepared PtNi octahedral nanoparticles, whereas the mass activity decreased by only 15.0% for the Br-treated PtNi nanoparticles. The simple treatment significantly enhanced the long-term stability of the highly active PtNi alloy nano-octahedra.

  3. Synthesis of Fe nanoparticles on polyaniline covered carbon nanotubes for oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Hu, Tian-Hang; Yin, Zhong-Shu; Guo, Jian-Wei; Wang, Cheng

    2014-12-01

    Fe nanoparticles immobilized on polyaniline-covered carbon nanotube (CNT) surfaces (Fe NPs-PANI/CNT) are prepared by reducing FeCl3 in the mixing solution of aniline and CNT. Significantly, the structure of such composites can be effectively optimized by pretreating FeCl3 with sodium citrate (CA). In the absence of CNTs, we found these two routes have large differences in reduction behaviors and different PANI states with varied conductivities. Therefore, the self-assembly mechanism in the preparation is proposed and the controlled self-assembly manner in the pretreating route is disclosed. Under acid condition, both catalysts demonstrate high oxygen reduction reaction (ORR) activity with four-electron pathway, and high electrochemical durability, revealing a promising application in the proton exchange membrane fuel cells. However, the high Tafel slopes relating to the surface red-ox couple and porous conductivity are still the main obstacles to improve their ORR dynamic, and more efforts on these aspects are needed to drive non-noble catalyst application in future.

  4. Enhancement of oxygen reduction reaction activities by Pt nanoclusters decorated on ordered mesoporous porphyrinic carbons

    SciTech Connect

    Sun-Mi Hwang; Choi, YongMan; Kim, Min Gyu; Sohn, Young-Jun; Cheon, Jae Yeong; Joo, Sang Hoon; Yim, Sung-Dae; Kuttiyiel, Kurian A.; Sasaki, Kotaro; Adzic, Radoslav R.; Park, Gu-Gon

    2016-03-08

    The high cost of Pt-based membrane electrode assemblies (MEAs) is a critical hurdle for the commercialization of polymer electrolyte fuel cells (PEFCs). Recently, non-precious metal-based catalysts (NPMCs) have demonstrated much enhanced activity but their oxygen reduction reaction (ORR) activity is still inferior to that of Pt-based catalysts resulting in a much thicker electrode in the MEA. For the reduction of mass transport and ohmic overpotential we adopted a new concept of catalyst that combines an ultra-low amount of Pt nanoclusters with metal–nitrogen (M–Nx) doped ordered mesoporous porphyrinic carbon (FeCo–OMPC(L)). The 5 wt% Pt/FeCo–OMPC(L) showed a 2-fold enhancement in activities compared to a higher loading of Pt. Our experimental results supported by first-principles calculations indicate that a trace amount of Pt nanoclusters on FeCo–OMPC(L) significantly enhances the ORR activity due to their electronic effect as well as geometric effect from the reduced active sites. Finally, in terms of fuel cell commercialization, this class of catalysts is a promising candidate due to the limited use of Pt in the MEA.

  5. Enhancement of oxygen reduction reaction activities by Pt nanoclusters decorated on ordered mesoporous porphyrinic carbons

    DOE PAGES

    Sun-Mi Hwang; Choi, YongMan; Kim, Min Gyu; ...

    2016-03-08

    The high cost of Pt-based membrane electrode assemblies (MEAs) is a critical hurdle for the commercialization of polymer electrolyte fuel cells (PEFCs). Recently, non-precious metal-based catalysts (NPMCs) have demonstrated much enhanced activity but their oxygen reduction reaction (ORR) activity is still inferior to that of Pt-based catalysts resulting in a much thicker electrode in the MEA. For the reduction of mass transport and ohmic overpotential we adopted a new concept of catalyst that combines an ultra-low amount of Pt nanoclusters with metal–nitrogen (M–Nx) doped ordered mesoporous porphyrinic carbon (FeCo–OMPC(L)). The 5 wt% Pt/FeCo–OMPC(L) showed a 2-fold enhancement in activities comparedmore » to a higher loading of Pt. Our experimental results supported by first-principles calculations indicate that a trace amount of Pt nanoclusters on FeCo–OMPC(L) significantly enhances the ORR activity due to their electronic effect as well as geometric effect from the reduced active sites. Finally, in terms of fuel cell commercialization, this class of catalysts is a promising candidate due to the limited use of Pt in the MEA.« less

  6. In situ surface characterization and oxygen reduction reaction on shape-controlled gold nanoparticles.

    PubMed

    Hernández, J; Solla-Gullón, J; Herrero, E; Feliu, J M; Aldaz, A

    2009-04-01

    Gold nanoparticles of different shapes/surface structures were synthesized and electrochemically characterized. An in-situ surface characterization of the Au nanoparticles, which was able to obtain qualitative information about the type and relative sizes of the different facets present in the surface of the Au nanoparticles, was carried out by using Pb Under Potential Deposition (UPD) in alkaline solutions as a surface sensitive tool. The results obtained show that the final atomic arrangement on the surface can be different from that expected from the bulk structure of the well-defined shape Au nanoparticles. In this way, the development of precise in-situ methods to measure the distribution of the different sites on the nanoparticle surface, as lead UPD on gold surfaces, is highlighted. Oxygen Reduction Reaction (ORR) was performed on the different Au nanoparticles. In agreement with the particular sensitivity of the oxygen reduction to the presence of Au(100) surface domains, cubic Au nanoparticles show much better electrocatalytic activity for ORR than small spherical particles and long nanorods, in agreement with the presence of a great fraction of (100) terrace sites on the surface of cubic gold nanoparticles.

  7. Effect of component distribution and nanoporosity in CuPt nanotubes on electrocatalysis of the oxygen reduction reaction.

    PubMed

    Guo, Huizhang; Liu, Xiang; Bai, Chengdong; Chen, Yuanzhi; Wang, Laisen; Zheng, Mingsen; Dong, Quanfeng; Peng, Dong-Liang

    2015-02-01

    Pt-based bimetallic electrocatalysts hold great potential in the oxygen reduction reaction (ORR) in current fuel-cell prototypes. However, they also face challenges from drastic dealloying of less-noble metals and coalescence of small nanoparticles. Porous and structure-ordered nanotubes may hold the potential to improve the stability of bimetallic electrocatalysts. Herein, we report a method to prepare CuPt nanotubes and porous Cu3 Pt intermetallic nanorods through a controlled galvanic replacement reaction and heat treatment process. The effect of the geometric features and compositional segregation on the electrocatalysis of the ORR was clarified. The outstanding performance of the Cu3 Pt/C-700 catalyst in the ORR relative to that of CuPt/C-RT was mainly attributed to the nanoporosity of the catalyst, whereas the enhanced specific activity on CuPt/C-RT after potential cycling was attributed to the interaction between the CuPt alloyed core and the Pt shell in the tube wall. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Preparation of fibrous titania oxynitride - carbon catalyst and oxygen reduction reaction analysis in both acidic and alkaline media

    NASA Astrophysics Data System (ADS)

    Kinumoto, Taro; Sou, Yoshinori; Ono, Kohei; Matsuoka, Miki; Arai, Yasuhiko; Tsumura, Tomoki; Toyoda, Masahiro

    2015-01-01

    A fibrous catalyst of titania oxynitride and carbon is prepared and its catalytic behavior in the oxygen reduction reaction (ORR) are investigated in both HClO4 and KOH aqueous solutions. TiO2 particles are successfully deposited on activated carbon fibers by a liquid phase deposition technique using (NH4)2TiF6 and H3BO3. The catalyst obtained after subsequent ammonia nitridation at 1273 K had a fibrous structure with TiOxNy and TiN components. Interestingly, the product demonstrates catalytic activity for the ORR in not only HClO4 but also KOH aqueous solution. The onset potential in HClO4 solution is assumed to be moderate, at 0.85 V; on the other hand, that in KOH solution is relatively high at 0.95 V. Furthermore, it is considered from the Tafel plot analysis of the KOH solution result that the ORR mechanism follows a peroxide intermediate pathway and the rate-determining step would be a one-electron-transfer reaction to oxygen molecules adsorbed on the active site.

  9. Structural disordering of de-alloyed Pt bimetallic nanocatalysts: the effect on oxygen reduction reaction activity and stability.

    PubMed

    Spanos, Ioannis; Dideriksen, Knud; Kirkensgaard, Jacob J K; Jelavic, Stanislav; Arenz, Matthias

    2015-11-14

    Platinum bimetallic alloys are well-known for their ability to catalyze the oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs). Pt(x)Co(1-x) colloidal nanoparticles were synthesized with varying initial Pt : Co ratios, but constant size to investigate how the initial metal composition affects their electrocatalytic performance. The results show that upon contact with acid environment the Co leaches out of the particles leading to almost identical compositions, independent of the initial differences. Surprisingly the data show a clear trend in ORR activity, although the Pt(x)Co(1-x) nanoparticles almost completely de-alloy during acid leaching, i.e. under reaction conditions in a fuel cell. To scrutinize the resulting particle structure after de-alloying we used pair distribution function (PDF) analysis and X-ray diffraction (XRD) gaining insight into the structural disorder and its dependence on the initial metal composition. Our results suggest that not only the ORR activity, but also the corrosion resistance of the synthesized NPs, are dependent on the structural disorder resulting from the de-alloying process.

  10. Hollow structured carbon-supported nickel cobaltite nanoparticles as an efficient bifunctional electrocatalyst for the oxygen reduction and evolution reaction

    SciTech Connect

    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. 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.

  11. Hollow structured carbon-supported nickel cobaltite nanoparticles as an efficient bifunctional electrocatalyst for the oxygen reduction and evolution reaction

    DOE PAGES

    Wang, Jie; Han, Lili; Lin, Ruoqian; ...

    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. Silicon and phosphorus dual doped graphene as the promising metal-free catalysts for oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Lu, Zhansheng; Li, Shuo; Yang, Zongxian; Wu, Ruqian

    The pathways of oxygen reduction reaction (ORR) on the metal-free silicon and phosphorus dual doped graphene (Si-P-G) catalyst are systematically investigated based on the dispersion-corrected density functional theory (DFT-D) method. It is found that the Si-P-G can be stable at high temperature from the first-principles molecular dynamics simulation and the local region of dopants displays an important role in the adsorption and reduction of oxygen. Both of the four-electron O2 direct dissociation and the two-electron OOH dissociation pathways are probable for ORR on the Si-P-G, while the latter pathway is mainly followed by the pathway of the OH hydrogenation into H2O. For the OOH dissociation pathway, the hydrogenation of O2 to OOH is the rate-limiting step with a rather small barrier energy of 0.66 eV. The current results indicate that the Si-P-G is a novel metal-free catalyst for ORR, and which is comparable to that of the Pt catalyst. Work was supported by the National Science Foundation Center for Chemical Innovation on Chemistry at the Space-Time Limit (CaSTL) under Grant No. CHE-1414466, and the National Natural Science Foundation of China (Grant Nos. 51401078, and 11474086).

  13. A Simple Synthesis of an N-Doped Carbon ORR Catalyst: Hierarchical Micro/Meso/Macro Porosity and Graphitic Shells.

    PubMed

    Eisenberg, David; Stroek, Wowa; Geels, Norbert J; Sandu, Cosmin S; Heller, Adam; Yan, Ning; Rothenberg, Gadi

    2016-01-11

    Replacing platinum as an oxygen reduction catalyst is an important scientific and technological challenge. Herein we report a simple synthesis of a complex carbon with very good oxygen reduction reaction (ORR) activity at pH 13. Pyrolysis of magnesium nitrilotriacetate yields a carbon with hierarchical micro/meso/macro porosity, resulting from in situ templating by spontaneously forming MgO nanoparticles and from etching by pyrolysis gases. The mesopores are lined with highly graphitic shells. The high ORR activity is attributed to a good balance between high specific surface area and mass transport through the hierarchical porosity, and to improved electronic conductivity through the graphitic shells. This novel carbon has a high surface area (1320 m(2) g(-1) ), and high nitrogen content for a single precursor synthesis (∼6 %). Importantly, its synthesis is both cheap and easily scalable.

  14. Best Practices and Testing Protocols for Benchmarking ORR Activities of Fuel Cell Electrocatalysts Using Rotating Disk Electrode

    DOE PAGES

    Kocha, Shyam S.; Shinozaki, Kazuma; Zack, Jason W.; ...

    2017-05-02

    Thin-film-rotating disk electrodes (TF-RDEs) are the half-cell electrochemical system of choice for rapid screening of oxygen reduction reaction (ORR) activity of novel Pt supported on carbon black supports (Pt/C) electrocatalysts. It has been shown that the magnitude of the measured ORR activity and reproducibility are highly dependent on the system cleanliness, evaluation protocols, and operating conditions as well as ink formulation, composition, film drying, and the resultant film thickness and uniformity. Accurate benchmarks of baseline Pt/C catalysts evaluated using standardized protocols and best practices are necessary to expedite ultra-low-platinum group metal (PGM) catalyst development that is crucial for the imminentmore » commercialization of fuel cell vehicles. We report results of evaluation in three independent laboratories of Pt/C electrocatalysts provided by commercial fuel cell catalyst manufacturers (Johnson Matthey, Umicore, Tanaka Kikinzoku Kogyo - TKK). The studies were conducted using identical evaluation protocols/ink formulation/film fabrication albeit employing unique electrochemical cell designs specific to each laboratory. Furthermore, the ORR activities reported in this work provide a baseline and criteria for selection and scale-up of novel high activity ORR electrocatalysts for implementation in proton exchange membrane fuel cells (PEMFCs).« less

  15. Synergistic Effect between the Atomically Dispersed Active Site of Fe-N-C and C-S-C for ORR in Acidic Medium.

    PubMed

    Shen, Hangjia; Gracia-Espino, Eduardo; Ma, Jingyuan; Zang, Ketao; Luo, Jun; Wang, Le; Gao, Sanshuang; Mamat, Xamxikamar; Hu, Guangzhi; Wagberg, Thomas; Guo, Shaojun

    2017-08-31

    Various advanced catalysts of sulfur doped Fe-N-C materials have been recently designed for oxygen reduction reaction (ORR), however, the enhanced activity is still controversial and usually attributed to differences in surface area, improved conductivity, or to uncertain synergistic effects. Here, a sulfur-doped Fe-N-C catalyst (denoted as Fe/SNC) derived via a template sacrificing method is presented. The incorporated S gives a thiophene-like structure (C-S-C), reduces the electron localization around the Fe center, improves the interaction with oxygenated species, and therefore facilitates the complete 4e- ORR in acid solution. This synergistic effect makes the Fe/SNC catalyst exhibits much better ORR activity than sulfur free catalyst (Fe/NC) in 0.5 M H2SO4. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Electrochemical investigations of Co3Fe-RGO as a bifunctional catalyst for oxygen reduction and evolution reactions in alkaline media

    NASA Astrophysics Data System (ADS)

    Kumar, Surender; Kumar, Divyaratan; Kishore, Brij; Ranganatha, Sudhakar; Munichandraiah, Nookala; Venkataramanan, Natarajan S.

    2017-10-01

    Nanoparticles of Co3Fe alloy is prepared on reduced graphene oxide (RGO) sheets by modified polyol method. Synthesized alloy particles are characterized by various physicochemical techniques. TEM and SEM pictures showed homogeneously dispersed alloy nanoparticles on the RGO sheets. Electrochemistry of alloy nanoparticles is investigated in alkaline medium. The result shows that oxygen evaluation reaction (OER) activity of Co3Fe-RGO is higher than Pt-black particles. RDE studies in alkaline medium shows that oxygen reduction reaction (ORR) follow four electron pathway. It is suggest that Co3Fe-RGO is an efficient non-precious catalyst for oxygen (ORR/OER) reactions in alkaline electrolyte for PEMFC applications.

  17. 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.

  18. 2D molybdenum disulphide (2D-MoS2) modified electrodes explored towards the oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Rowley-Neale, Samuel J.; Fearn, Jamie M.; Brownson, Dale A. C.; Smith, Graham C.; Ji, Xiaobo; Banks, Craig E.

    2016-08-01

    Two-dimensional molybdenum disulphide nanosheets (2D-MoS2) have proven to be an effective electrocatalyst, with particular attention being focused on their use towards increasing the efficiency of the reactions associated with hydrogen fuel cells. Whilst the majority of research has focused on the Hydrogen Evolution Reaction (HER), herein we explore the use of 2D-MoS2 as a potential electrocatalyst for the much less researched Oxygen Reduction Reaction (ORR). We stray from literature conventions and perform experiments in 0.1 M H2SO4 acidic electrolyte for the first time, evaluating the electrochemical performance of the ORR with 2D-MoS2 electrically wired/immobilised upon several carbon based electrodes (namely; Boron Doped Diamond (BDD), Edge Plane Pyrolytic Graphite (EPPG), Glassy Carbon (GC) and Screen-Printed Electrodes (SPE)) whilst exploring a range of 2D-MoS2 coverages/masses. Consequently, the findings of this study are highly applicable to real world fuel cell applications. We show that significant improvements in ORR activity can be achieved through the careful selection of the underlying/supporting carbon materials that electrically wire the 2D-MoS2 and utilisation of an optimal mass of 2D-MoS2. The ORR onset is observed to be reduced to ca. +0.10 V for EPPG, GC and SPEs at 2D-MoS2 (1524 ng cm-2 modification), which is far closer to Pt at +0.46 V compared to bare/unmodified EPPG, GC and SPE counterparts. This report is the first to demonstrate such beneficial electrochemical responses in acidic conditions using a 2D-MoS2 based electrocatalyst material on a carbon-based substrate (SPEs in this case). Investigation of the beneficial reaction mechanism reveals the ORR to occur via a 4 electron process in specific conditions; elsewhere a 2 electron process is observed. This work offers valuable insights for those wishing to design, fabricate and/or electrochemically test 2D-nanosheet materials towards the ORR.Two-dimensional molybdenum disulphide nanosheets

  19. Metal-Organic-Framework-Derived Dual Metal- and Nitrogen-Doped Carbon as Efficient and Robust Oxygen Reduction Reaction Catalysts for Microbial Fuel Cells.

    PubMed

    Tang, Haolin; Cai, Shichang; Xie, Shilei; Wang, Zhengbang; Tong, Yexiang; Pan, Mu; Lu, Xihong

    2016-02-01

    A new class of dual metal and N doped carbon catalysts with well-defined porous structure derived from metal-organic frameworks (MOFs) has been developed as a high-performance electrocatalyst for oxygen reduction reaction (ORR). Furthermore, the microbial fuel cell (MFC) device based on the as-prepared Ni/Co and N codoped carbon as air cathode catalyst achieves a maximum power density of 4335.6 mW m(-2) and excellent durability.

  20. Nano-sized TiN on carbon black as an efficient electrocatalyst for the oxygen reduction reaction prepared using an mpg-C3N4 template.

    PubMed

    Chen, Jia; Takanabe, Kazuhiro; Ohnishi, Ryohji; Lu, Daling; Okada, Saori; Hatasawa, Haruna; Morioka, Hiroyuki; Antonietti, Markus; Kubota, Jun; Domen, Kazunari

    2010-10-28

    The direct synthesis of TiN nanoparticles on carbon black (CB) was achieved using an mpg-C(3)N(4)/CB composite as a template. The obtained TiN/CB composites ensured improved contact between TiN and CB, functioning as an efficient cathode catalyst for oxygen reduction reaction (ORR) in polymer electrolyte fuel cells (PEFCs). The preparation procedure developed in this study is applicable for the synthesis of a variety of supported nano-nitride catalysts.

  1. Mesoporous NiCo2O4 Nanoplates on Three-Dimensional Graphene Foam as an Efficient Electrocatalyst for the Oxygen Reduction Reaction.

    PubMed

    Tong, Xili; Chen, Shuai; Guo, Congxiu; Xia, Xinhui; Guo, Xiang-Yun

    2016-01-21

    Catalysts for the oxygen reduction reaction (ORR) are highly important in fuel cells and metal-air batteries. Cheap ORR catalysts with ultrahigh electrochemical activity, selectivity, and stability are extremely desirable but still remain challenging. Herein, mesoporous NiCo2O4 nanoplate (NP) arrays on three-dimensional (3D) graphene foam are shown to be a highly economical ORR catalyst. This mesoporous mixed-valence oxide can provide more electrocatalytic active sites with increased accessible surface area. In addition, graphene-foam-supported NiCo2O4 NP arrays have a 3D hierarchical porous structure, which is of great benefit to ion diffusion and electron transfer. As a result, the mesoporous NiCo2O4 NP arrays/graphene foam catalyst exhibits outstanding ORR performance with the four-electron reduction of O2 to H2O in alkaline media. Furthermore, the mesoporous catalyst shows enhanced electrocatalytic activity with a half-wave potential of 0.86 V vs RHE and better stability compared with a commercial Pt/C catalyst.

  2. Enhancing pyridinic nitrogen level in graphene to promote electrocatalytic activity for oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Sun, Jiaguang; Wang, Lan; Song, Ranran; Yanga, Shubin

    2016-02-01

    We develop an efficient approach to fabricate nitrogen-doped graphene with tunable pyridinic nitrogen levels (from 1.1 to 1.8 at.%), abundant in-plane holes and high surface areas (623 m2 g-1) via a hydrothermal treatment of graphene oxide with hydrogen peroxide and subsequent annealing under ammonia gas. It is found that the chemical etching is beneficial to the formation of pyridinic nitrogen in graphene during the nitrogen-doping process, which is crucial to enhancing the electrocatalytic properties of graphene for oxygen reduction reaction (ORR). Hence, the optimized NG exhibits good electrocatalytic activity, more positive onset potential than Pt-C (-0.08 V versus -0.09 V), good durability, and high selectivity when it is employed as a metal-free catalyst for ORR. This approach may uncover a mechanism in escalation of pyridinic N atoms doped on the graphene basal edge and provide an efficient platform for the synthesis of a series of heteroatom-doped graphene with tunable heteroatom content for broad applications.

  3. A unique platinum-graphene hybrid structure for high activity and durability in oxygen reduction reaction

    PubMed Central

    Wang, Chengming; Ma, Liang; Liao, Lingwen; Bai, Song; Long, Ran; Zuo, Ming; Xiong, Yujie

    2013-01-01

    It remains a grand challenge to achieve both high activity and durability in Pt electrocatalysts for oxygen reduction reaction (ORR) in fuel cells. Here we develop a class of Pt highly concave cubic (HCC) nanocrystals, which are enriched with high-index facets, to enable high ORR activity. The durability of HCC nanocrystals can be significantly improved via assembly with graphene. Meanwhile, the unique hybrid structure displays further enhanced specific activity, which is 7-fold greater than the state-of-the-art Pt/C catalysts. Strikingly, it exhibits impressive performance in terms of half-wave potential (E1/2). The E1/2 of 0.967 V at the Pt loading as low as 46 μg cm−2, which stands as 63 mV higher than that of the Pt/C catalysts, is slightly superior to the record observed for the most active porous Pt-Ni catalyst in literature. This work paves the way to designing high-performance electrocatalysts by modulating their surface and interface with loading substrates. PMID:23999570

  4. Porous Carbon Nanosheets Codoped with Nitrogen and Sulfur for Oxygen Reduction Reaction in Microbial Fuel Cells.

    PubMed

    Yuan, Heyang; Hou, Yang; Wen, Zhenhai; Guo, Xiaoru; Chen, Junhong; He, Zhen

    2015-08-26

    In this work, a simple synthesis strategy has been developed for the preparation of nitrogen- and sulfur-codoped porous carbon nanosheets (N/S-CNS) as a cathode catalyst for microbial fuel cells (MFCs). The as-prepared N/S-CNS showed favorable features for electrochemical energy conversion such as high surface area (1004 m(2) g(-1)), defect structure, and abundant exposure of active sites that arose primarily from porous nanosheet morphology. Benefiting from the unique nanostructure, the resulting nanosheets exhibited effective electrocatalytic activity toward oxygen reduction reaction (ORR). The onset potential of the N/S-CNS in linear-sweep voltammetry was approximately -0.05 V vs Ag/AgCl in neutral phosphate buffer saline. Electrochemical impedance spectroscopy showed that the ohmic and charge-transfer resistance of the codoped catalyst were 1.5 and 14.8 Ω, respectively, both of which were lower than that of platinum/carbon (Pt/C). Furthermore, the electron-transfer number of the N/S-CNS was calculated to be ∼3.5, suggesting that ORR on the catalyst proceeds predominantly through the favorable four-electron pathway. The MFC with N/S-CNS as a cathode catalyst generated current density (6.6 A m(-2)) comparable to that with Pt/C (7.3 A m(-2)). The high durability and low price indicate that N/S-CNS can be a competitive catalyst for applications of MFCs.

  5. Photoassisted Oxygen Reduction Reaction in H2 -O2 Fuel Cells.

    PubMed

    Zhang, Bingqing; Wang, Shengyang; Fan, Wenjun; Ma, Weiguang; Liang, Zhenxing; Shi, Jingying; Liao, Shijun; Li, Can

    2016-11-14

    The oxygen reduction reaction (ORR) is a key step in H2 -O2 fuel cells, which, however, suffers from slow kinetics even for state-of-the-art catalysts. In this work, by making use of photocatalysis, the ORR was significantly accelerated with a polymer semiconductor (polyterthiophene). The onset potential underwent a positive shift from 0.66 to 1.34 V, and the current was enhanced by a factor of 44 at 0.6 V. The improvement was further confirmed in a proof-of-concept light-driven H2 -O2 fuel cell, in which the open circuit voltage (Voc ) increased from 0.64 to 1.18 V, and the short circuit current (Jsc ) was doubled. This novel tandem structure combining a polymer solar cell and a fuel cell enables the simultaneous utilization of photo- and electrochemical energy, showing promising potential for applications in energy conversion and storage. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. One-step synthesis of nitrogen-iron coordinated carbon nanotube catalysts for oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Choi, Woongchul; Yang, Gang; Kim, Suk Lae; Liu, Peng; Sue, Hung-Jue; Yu, Choongho

    2016-05-01

    Prohibitively expensive precious metal catalysts for oxygen reduction reaction (ORR) have been one of the major hurdles in a wide use of electrochemical cells. Recent significant efforts to develop precious metal free catalysts have resulted in excellent catalytic activities. However, complicated and time-consuming synthesis processes have negated the cost benefit. Moreover, detailed analysis about catalytically active sites and the role of each element in these high-performance catalysts containing nanomaterials for large surface areas are often lacking. Here we report a facile one-step synthesis method of nitrogen-iron coordinated carbon nanotube (CNT) catalysts without precious metals. Our catalysts show excellent long-term stability and onset ORR potential comparable to those of other precious metal free catalysts, and the maximum limiting current density from our catalysts is larger than that of the Pt-based catalysts. We carry out a series of synthesis and characterization experiments with/without iron and nitrogen in CNT, and identify that the coordination of nitrogen and iron in CNT plays a key role in achieving the excellent catalytic performances. We anticipate our one-step process could be used for mass production of precious metal free electrocatalysts for a wide range of electrochemical cells including fuel cells and metal-air batteries.

  7. Role of Pyridinic-N for Nitrogen-doped graphene quantum dots in oxygen reaction reduction.

    PubMed

    Sun, Lang; Luo, Yi; Li, Ming; Hu, Guanghui; Xu, Yongjie; Tang, Tao; Wen, Jianfeng; Li, Xinyu; Wang, Liang

    2017-12-15

    Nitrogen-doped graphene quantum dots (N-GQDs) exhibit exciting properties in the oxygen reduction reaction (ORR) for ample electrocatalytic edging and N-doped active sites. However, low yield and high dispersity of N-GQDs prohibit their direct application as the electrocatalyst. In this paper, two facile hydrothermal progress were developed to synthesize the high-yield N-GQDs with the diameter of ca. 2-6nm and the hybrid of N-GQDs/Reduced Graphene Oxide (N-GQDs/r-GO). The results demonstrated that the N-GQDs/r-GO display remarkable electrocatalytic activity. Moreover, it can be found that the pyridinic-N plays a major role in ORR. Both the average electron transfer number and the onset potential depend on the content of pyridinic-N. The proposed synthesis strategy is facile and low-cost, serving as a feasible method for the development of highly efficient electrocatalysts. Copyright © 2017 Elsevier Inc. All rights reserved.

  8. Reduction Methods for Total Reaction Cross Sections

    NASA Astrophysics Data System (ADS)

    Gomes, P. R. S.; Mendes Junior, D. R.; Canto, L. F.; Lubian, J.; de Faria, P. N.

    2016-03-01

    The most frequently used methods to reduce fusion and total reaction excitation functions were investigated in a very recent paper Canto et al. (Phys Rev C 92:014626, 2015). These methods are widely used to eliminate the influence of masses and charges in comparisons of cross sections for weakly bound and tightly bound systems. This study reached two main conclusions. The first is that the fusion function method is the most successful procedure to reduce fusion cross sections. Applying this method to theoretical cross sections of single channel calculations, one obtains a system independent curve (the fusion function), that can be used as a benchmark to fusion data. The second conclusion was that none of the reduction methods available in the literature is able to provide a universal curve for total reaction cross sections. The reduced single channel cross sections keep a strong dependence of the atomic and mass numbers of the collision partners, except for systems in the same mass range. In the present work we pursue this problem further, applying the reduction methods to systems within a limited mass range. We show that, under these circumstances, the reduction of reaction data may be very useful.

  9. 2,3-diaminopyridine functionalized reduced graphene oxide-supported palladium nanoparticles with high activity for electrocatalytic oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Yasmin, Sabina; Joo, Yuri; Jeon, Seungwon

    2017-06-01

    The electrochemical deposition of Pd nanoparticles (Pd NPs) on 2,3 diamino pyridine functionalized reduced graphene oxide (2,3 DAP-rGO/Pd) has been investigated for the oxygen reduction reaction (ORR) in alkaline media. First, 2,3 diaminopyridine functionalized graphene oxide (2,3 DAP-rGO) has been synthesized via simple hydrothermal method. Then, palladium is directly incorporated into the 2,3 DAP-rGO by electrochemical deposition method to generate 2,3 DAP-rGO/Pd composites. The as-prepared material 2,3 DAP-rGO/Pd has been characterized by various instrumental methods. The morphological analysis shows the cluster-like Pd nanoparticles are dispersed onto the 2,3 diamino pyridine functionalized reduced graphene oxide (2,3 DAP-rGO). The electrocatalytic activities have been verified using cyclic voltammetry (CV) and hydrodynamic voltammetry and chronoamperometry techniques in 0.1 M KOH electrolyte. The as-synthesized 2,3 DAP-rGO/Pd shows higher catalytic activity toward ORR with more positive onset potential and cathodic current density, superior methanol/ethanol tolerance and excellent stability in alkaline medium. It is also noteworthy that the 2,3 DAP-rGO/Pd exhibits a four-electron transfer pathway for ORR with lower H2O2 yield.

  10. Tiny crystalline grain nanocrystal NiCo2O4/N-doped graphene composite for efficient oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Wan, Li-li; Zang, Guo-long; Wang, Xin; Zhou, Le-an; Li, Tian; Zhou, Qi-xing

    2017-03-01

    Oxygen reduction reaction (ORR) plays an important role in green energy conversion, although catalysts are necessary for overcoming its sluggish kinetic. Herein, a nanocrystal NiCo2O4/N-doped graphene composite material showing high ORR electrocatalytic activity is prepared. The resulting NiCo2O4/N-doped graphene composite (NiCo2O4-NG/C) combines the advantages of both component materials and shows enhanced ORR electrocatalytic activity (i.e., more positive peak potential and half-wave potential compared with NiCo2O4) while having higher diffusion-limited current density values (-5.7 mA cm-2, 1600 rpm), better tolerance to methanol, and improved stability than 20 wt% Pt/C. NiCo2O4 anchored on N-doped graphene are demonstrated to be nanocrystal with tiny crystalline grain (diameter < 5 nm) and result in large surface area, thereby allowing more active sites to be exposed. Moreover, the potential exposure of high-index planes may be also responsible for the observed high activity of these materials.

  11. Seaweed-derived heteroatom-doped highly porous carbon as an electrocatalyst for the oxygen reduction reaction.

    PubMed

    Song, Min Young; Park, Hyean Yeol; Yang, Dae-Soo; Bhattacharjya, Dhrubajyoti; Yu, Jong-Sung

    2014-06-01

    We report the template-free pyrolysis of easily available natural seaweed, Undaria pinnatifida, as a single precursor, which results in "seaweed carbon" (SCup). Interestingly, thus-obtained SCup not only contains heteroatoms such as nitrogen and sulfur in its framework, but it also possesses a well-developed porous structure with high surface area. The heteroatoms in SCup originate from the nitrogen- and sulfur-containing ingredients in seaweed, whereas the porosity is created by removal of salts inherently present in the seaweed. These essential and fundamental properties make seaweed a prime choice as a precursor for heteroatom-containing highly porous carbon as a metal-free efficient electrocatalyst. As-synthesized SCup showed excellent electrocatalytic activity in the oxygen reduction reaction (ORR) in alkaline medium, which can be addressed in terms of the presence of the nitrogen and sulfur heteroatoms, the well-developed porosity, and the electrical conductivity in the carbon framework. The pyrolysis temperature was a key controlling parameter that determined the trade-off between heteroatom doping, surface properties, and electrical conductivity. In particular, SCup prepared at 1000 °C showed the best ORR performance. Additionally, SCup exhibited enhanced durability and methanol tolerance relative to the state of the art commercial Pt catalyst, which demonstrates that SCup is a promising alternative to costly Pt-based catalysts for the ORR.

  12. Manganese oxide/poly(3,4-ethylenedioxythiophene) hybrid electrocatalysts for the oxygen reduction reaction in alkaline fuel cells

    SciTech Connect

    Lambert, Timothy N.; Vigil, Julian A.

    2016-08-22

    Manganese oxide/poly(3,4-ethylene-dioxythiophene) (MnOx/ PEDOT) nanostructured hybrid thin films were prepared using a simple anodic electrodeposition process from aqueous solution, and then tested for oxygen reduction reaction (ORR) activity in alkaline electrolyte using rotating disk electrode and rotating ring disk electrode methods. MnOx/PEDOT provided improvements over MnOx-only and PEDOT-only control films, with > 0.2 V decrease in onset and half-wave overpotentials, and > 1.5 times increase in terminal current density. The MnOx/PEDOT film exhibited only a slightly lower n value (n = 3.86-3.92) than the 20% Pt/C benchmark electrocatalyst (n = 3.98) across all potentials. MnOx/PEDOT also displayed a more positive half-wave potential and superior electrocatalytic selectivity for the ORR upon methanol exposure than 20% Pt/C. Here, the high activity and synergism of MnOx/PEDOT towards the ORR is attributed to effective intermixing/dispersion of the two materials, intimate substrate contact with improved charge transfer processes attained by co-electrodepositing MnOx with PEDOT and due to the increase in Mn3+ content at the surface of the oxide.

  13. Improving biomass-derived carbon by activation with nitrogen and cobalt for supercapacitors and oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Zhang, Man; Jin, Xin; Wang, Linan; Sun, Mengjia; Tang, Yang; Chen, Yongmei; Sun, Yanzhi; Yang, Xiaojin; Wan, Pingyu

    2017-07-01

    Biomass-derived carbon by activation with nitrogen and cobalt (denoted as NPACCo) was prepared by one-pot pyrolysis of pomelo peel with melamine, cobalt nitrate and potassium hydroxide, followed by acid leaching. NPACCo possesses high content of quaternary-N (2.5%) and pyridinic-N (1.7%), co-existences of amorphous and short-range ordered carbon, high specific surface area and pore structure with majority of micropores and small mesopores. As electrode material of supercapacitors, NPACCo exhibits high specific capacitance and good rate capability. At ultrahigh rate of 50 A g-1 (135 mA cm-2), the capacitance of NPACCo remains 246 F g-1, which is 6.3, 1.9 and 3.2 times as high as that of other three materials (PC, PAC and NPAC). The as-assembled symmetric supercapacitor of NPACCo delivers high energy density, high power density and excellent cycling stability. With respect to oxygen reduction reaction (ORR), NPACCo exhibits high onset potential (0.87 V), high half-wave potential (0.78 V), excellent methanol tolerance and low yield of H2O2. The ORR properties of NPACCo are comparable or superior to those of commercial Pt/C. This investigation of pomelo peel-based NPACCo would be valuable for development of both supercapacitor and ORR.

  14. Rationalization of Au concentration and distribution in AuNi@Pt core-shell nanoparticles for oxygen reduction reaction

    SciTech Connect

    An, Wei; Liu, Ping

    2015-09-18

    Improving the activity and stability of Pt-based core–shell nanocatalysts for proton exchange membrane fuel cells while lowering Pt loading has been one of the big challenges in electrocatalysis. Here, using density functional theory, we report the effect of adding Au as the third element to enhance the durability and activity of Ni@Pt core–shell nanoparticles (NPs) during the oxygen reduction reaction (ORR). Our results show that the durability and activity of a Ni@Pt NP can be finely tuned by controlling Au concentration and distribution. For a NiAu@Pt NP, the durability can be greatly promoted by thermodynamically favorable segregation of Au to replace the Pt atoms at vertex, edge, and (100) facets on the shell, while still keeping the ORR activity on the active Pt(111) shell as high as that of Ni@Pt nanoparticles. Such behavior strongly depends on a direct interaction with the Ni interlayer. The results not only highlight the importance of interplay between surface strain on the shell and the interlayer–shell interaction in determining the durability and activity but also provide guidance on how to maximize the usage of Au to optimize the performance of core–shell (Pt) nanoparticles. As a result, such understanding has allowed us to discover a novel NiAu@Pt nanocatalyst for the ORR.

  15. Facile synthesis of nitrogen and sulfur codoped carbon from ionic liquid as metal-free catalyst for oxygen reduction reaction.

    PubMed

    She, Yiyi; Lu, Zhouguang; Ni, Meng; Li, Li; Leung, Michael K H

    2015-04-08

    Developing metal-free catalysts for oxygen reduction reaction (ORR) is a great challenge in the development of fuel cells. Nitrogen and sulfur codoped carbon with remarkably high nitrogen content up to 13.00 at % was successfully fabricated by pyrolysis of homogeneous mixture of exfoliated graphitic flakes and ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([Bimi][Tf2N]). The exfoliated graphite flakes served as a structure-directing substance as well as additional carbon source in the fabrication. It was demonstrated that the use of graphite flakes increased the nitrogen doping level, optimized the composition of active nitrogen configurations, and enlarged the specific surface area of the catalysts. Electrochemical characterizations revealed that the N and S codoped carbon fabricated by this method exhibited superior catalytic activities toward ORR under both acidic and alkaline conditions. Particularly in alkaline solution, the current catalyst compared favorably to the conventional 20 wt % Pt/C catalyst via four-electron transfer pathway with better ORR selectivity. The excellent catalytic activity was mainly ascribed to high nitrogen doping content, appropriate constitution of active nitrogen configurations, large specific surface area, and synergistic effect of N and S codoping.

  16. Pt skin coated hollow Ag-Pt bimetallic nanoparticles with high catalytic activity for oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Fu, Tao; Huang, Jianxing; Lai, Shaobo; Zhang, Size; Fang, Jun; Zhao, Jinbao

    2017-10-01

    The catalytic activity and stability of electrocatalyst is critical for the commercialization of fuel cells, and recent reports reveal the great potential of the hollow structures with Pt skin coat for developing high-powered electrocatalysts due to their highly efficient utilization of the Pt atoms. Here, we provide a novel strategy to prepare the Pt skin coated hollow Ag-Pt structure (Ag-Pt@Pt) of ∼8 nm size at room temperature. As loaded on the graphene, the Ag-Pt@Pt exhibits a remarkable mass activity of 0.864 A/mgPt (at 0.9 V, vs. reversible hydrogen electrode (RHE)) towards oxygen reduction reaction (ORR), which is 5.30 times of the commercial Pt/C catalyst, and the Ag-Pt@Pt also shows a better stability during the ORR catalytic process. The mechanism of this significant enhancement can be attributed to the higher Pt utilization and the unique Pt on Ag-Pt surface structure, which is confirmed by the density functional theory (DFT) calculations and other characterization methods. In conclusion, this original work offers a low-cost and environment-friendly method to prepare a high active electrocatalyst with cheaper price, and this work also discloses the correlation between surface structures and ORR catalytic activity for the hollow structures with Pt skin coat, which can be instructive for designing novel advanced electrocatalysts for fuel cells.

  17. Manganese oxide/poly(3,4-ethylenedioxythiophene) hybrid electrocatalysts for the oxygen reduction reaction in alkaline fuel cells

    DOE PAGES

    Lambert, Timothy N.; Vigil, Julian A.

    2016-08-22

    Manganese oxide/poly(3,4-ethylene-dioxythiophene) (MnOx/ PEDOT) nanostructured hybrid thin films were prepared using a simple anodic electrodeposition process from aqueous solution, and then tested for oxygen reduction reaction (ORR) activity in alkaline electrolyte using rotating disk electrode and rotating ring disk electrode methods. MnOx/PEDOT provided improvements over MnOx-only and PEDOT-only control films, with > 0.2 V decrease in onset and half-wave overpotentials, and > 1.5 times increase in terminal current density. The MnOx/PEDOT film exhibited only a slightly lower n value (n = 3.86-3.92) than the 20% Pt/C benchmark electrocatalyst (n = 3.98) across all potentials. MnOx/PEDOT also displayed a more positivemore » half-wave potential and superior electrocatalytic selectivity for the ORR upon methanol exposure than 20% Pt/C. Here, the high activity and synergism of MnOx/PEDOT towards the ORR is attributed to effective intermixing/dispersion of the two materials, intimate substrate contact with improved charge transfer processes attained by co-electrodepositing MnOx with PEDOT and due to the increase in Mn3+ content at the surface of the oxide.« less

  18. Rationalization of Au concentration and distribution in AuNi@Pt core-shell nanoparticles for oxygen reduction reaction

    DOE PAGES

    An, Wei; Liu, Ping

    2015-09-18

    Improving the activity and stability of Pt-based core–shell nanocatalysts for proton exchange membrane fuel cells while lowering Pt loading has been one of the big challenges in electrocatalysis. Here, using density functional theory, we report the effect of adding Au as the third element to enhance the durability and activity of Ni@Pt core–shell nanoparticles (NPs) during the oxygen reduction reaction (ORR). Our results show that the durability and activity of a Ni@Pt NP can be finely tuned by controlling Au concentration and distribution. For a NiAu@Pt NP, the durability can be greatly promoted by thermodynamically favorable segregation of Au tomore » replace the Pt atoms at vertex, edge, and (100) facets on the shell, while still keeping the ORR activity on the active Pt(111) shell as high as that of Ni@Pt nanoparticles. Such behavior strongly depends on a direct interaction with the Ni interlayer. The results not only highlight the importance of interplay between surface strain on the shell and the interlayer–shell interaction in determining the durability and activity but also provide guidance on how to maximize the usage of Au to optimize the performance of core–shell (Pt) nanoparticles. As a result, such understanding has allowed us to discover a novel NiAu@Pt nanocatalyst for the ORR.« less

  19. Copper-Organic Framework Fabricated with CuS Nanoparticles: Synthesis, Electrical Conductivity, and Electrocatalytic Activities for Oxygen Reduction Reaction.

    PubMed

    Cho, Keumnam; Han, Sung-Hwan; Suh, Myunghyun Paik

    2016-12-05

    To apply electrically nonconductive metal-organic frameworks (MOFs) in an electrocatalytic oxygen reduction reaction (ORR), we have developed a new method for fabricating various amounts of CuS nanoparticles (nano-CuS) in/on a 3D Cu-MOF, [Cu3 (BTC)2 ⋅(H2 O)3 ] (BTC=1,3,5-benzenetricarboxylate). As the amount of nano-CuS increases in the composite, the electrical conductivity increases exponentially by up to circa 10(9) -fold, while porosity decreases, compared with that of the pristine Cu-MOF. The composites, nano-CuS(x wt %)@Cu-BTC, exhibit significantly higher electrocatalytic ORR activities than Cu-BTC or nano-CuS in an alkaline solution. The onset potential, electron transfer number, and kinetic current density increase when the electrical conductivity of the material increases but decrease when the material has a poor porosity, which shows that the two factors should be finely tuned by the amount of nano-CuS for ORR application. Of these materials, CuS(28 wt %)@Cu-BTC exhibits the best activity, showing the onset potential of 0.91 V vs. RHE, quasi-four-electron transfer pathway, and a kinetic current density of 11.3 mA cm(-2) at 0.55 V vs. RHE.

  20. Manganese oxide/poly(3,4-ethylenedioxythiophene) hybrid electrocatalysts for the oxygen reduction reaction in alkaline fuel cells

    SciTech Connect

    Lambert, Timothy N.; Vigil, Julian A.

    2016-08-22

    Manganese oxide/poly(3,4-ethylene-dioxythiophene) (MnOx/ PEDOT) nanostructured hybrid thin films were prepared using a simple anodic electrodeposition process from aqueous solution, and then tested for oxygen reduction reaction (ORR) activity in alkaline electrolyte using rotating disk electrode and rotating ring disk electrode methods. MnOx/PEDOT provided improvements over MnOx-only and PEDOT-only control films, with > 0.2 V decrease in onset and half-wave overpotentials, and > 1.5 times increase in terminal current density. The MnOx/PEDOT film exhibited only a slightly lower n value (n = 3.86-3.92) than the 20% Pt/C benchmark electrocatalyst (n = 3.98) across all potentials. MnOx/PEDOT also displayed a more positive half-wave potential and superior electrocatalytic selectivity for the ORR upon methanol exposure than 20% Pt/C. Here, the high activity and synergism of MnOx/PEDOT towards the ORR is attributed to effective intermixing/dispersion of the two materials, intimate substrate contact with improved charge transfer processes attained by co-electrodepositing MnOx with PEDOT and due to the increase in Mn3+ content at the surface of the oxide.

  1. A simple synthesis method for nanostructured Co-WC/carbon composites with enhanced oxygen reduction reaction activity

    PubMed Central

    Kang, Jun; Kim, Hye-min; Saito, Nagahiro; Lee, Myeong-Hoon

    2016-01-01

    Abstract Co nanoparticles (Co NPs) and nanoscale tungsten carbide (WC) are successfully synthesized simultaneously with mesoporous structured carbon black (C) using an innovative simple method, which is known as solution plasma processing (SPP), and NPs are also loaded onto carbon black at the same time by SPP. The introduction of Co NPs led to not only superior oxygen reduction reaction (ORR) activity in terms of onset potential and peak potential, but also to a more efficient electron transfer process compared to that of pure WC. Co-WC/C also showed durability for long-term operation better than that of commercial Pt/C. These results clearly demonstrate that the presence of Co NPs significantly enhanced the ORR and charge transfer number of neighboring WC NPs in ORR activities. In addition, it was proved that SPP is a simple method (from synthesis of NPs and carbon black to loading on carbon black) for the large-scale synthesis of NP-carbon composite. Therefore, SPP holds great potential as a candidate for next-generation synthetic methods for the production of NP-carbon composites. PMID:27877856

  2. A new method to synthesize sulfur-doped graphene as effective metal-free electrocatalyst for oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Zhai, Chunyang; Sun, Mingjuan; Zhu, Mingshan; Song, Shaoqing; Jiang, Shujuan

    2017-06-01

    The exploration of a metal-free catalyst with highly efficient yet low-cost for the oxygen-reduction reaction (ORR) is under wide spread investigation. In this paper, by using dimethyl sulfoxide (DMSO) as S source as well as solvent, we report a new, low-cost, and facile solvothermal route to synthesize S-doped reduced graphene oxide (S-RGO). The existence of S element in the framework of RGO was solidly confirmed by energy-dispersive X-ray (EDX) and X-ray photoelectron spectroscopy (XPS). The as-synthesized S-RGO can be worked as an efficient metal-free electrocatalyst for ORR. Moreover, compared to commercial Pt/C electrocatalyst, the S-RGO displays superior resistance to crossover effect and stability by evaluating the addition of methanol and CO poisoning experiment. This result not only shows S-RGO as a promising candidate instead of Pt-based catalyst for ORR, but also provides a new approach for the preparation of metal-free electrocatalyst in future.

  3. One-pot hydrothermal synthesis of Zinc ferrite/reduced graphene oxide as an efficient electrocatalyst for oxygen reduction reaction.

    PubMed

    Hong, Wei; Li, Lingzhi; Xue, Ruinan; Xu, Xiaoyang; Wang, Huan; Zhou, Jingkuo; Zhao, Huilin; Song, Yahui; Liu, Yu; Gao, Jianping

    2017-01-01

    Fabrication of low-cost and efficient electrocatalyst for oxygen reduction reaction (ORR) is highly desirable. Herein, Zinc ferrite/reduced graphene oxide (ZnFe2O4/rGO) is prepared by a quite simple and environmentally benign approach and applied as a high performance ORR electrocatalyst for the first time. The surface morphology and chemical composition of ZnFe2O4/rGO are characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, thermogravimetric analysis and Fourier transform infrared spectroscopy. Cyclic voltammetry, linear sweep voltammetry and chronoamperometry are used to evaluate the electrochemical activities and stabilities of ZnFe2O4/rGO catalysts in alkaline media. Among ZnFe2O4/rGO with different mass ratios, the catalyst with 69.8wt% ZnFe2O4 (called ZnFe2O4/rGO (3)) has the best catalytic activities and it shows much superior methanol tolerance and better durability than the commercial Pt/C catalyst. Due to the synergistic effect, the ZnFe2O4/rGO (3) nanohybrid exhibits high ORR catalytic performance and durability, which follows a desirable four electron transfer mechanism in alkaline media. Therefore, it may be a highly competitive catalyst for fuel cells and metal-air batteries.

  4. Cerium carbide embedded in nitrogen-doped carbon as a highly active electrocatalyst for oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Wang, Wei; Xue, Shouyuan; Li, Jinmei; Wang, Fengxia; Kang, Yumao; Lei, Ziqiang

    2017-08-01

    In this study, cerium carbide embedded in nitrogen-doped carbon (CeCx-NC) has been prepared by a facile pyrolysis of melamine formaldehyde resin containing rare-earth element. The as-prepared CeCx-NC catalyst shows high electrocatalytic activity towards oxygen reduction reaction (ORR) in alkaline electrolyte, with the half wave potential being almost equal to commercial Pt/C, nearly four electron transfer number, good toxicity tolerance durability and cycle stability. This rare-earth metal carbide opens a novel avenue for advanced electrocatalyst.

  5. Phosphorus-doped carbon nanotubes supported low Pt loading catalyst for the oxygen reduction reaction in acidic fuel cells

    NASA Astrophysics Data System (ADS)

    Liu, Ziwu; Shi, Qianqian; Zhang, Rufan; Wang, Quande; Kang, Guojun; Peng, Feng

    2014-12-01

    To develop low-cost and efficient cathode electrocatalysts for fuel cells in acidic media, phosphorus-doped carbon nanotubes (P-CNTs) supported low Pt loading catalyst (0.85% Pt) is designed. The as-prepared Pt/P-CNTs exhibit significantly enhanced electrocatalytic oxygen reduction reaction (ORR) activity and long-term stability due to the stronger interaction between Pt and P-CNTs, which is proven by X-ray photoelectron spectroscopic analysis and density functional theory calculations. Moreover, the as-prepared Pt/P-CNTs also display much better tolerance to methanol crossover effects, showing a good potential application for future proton exchange membrane fuel cell devices.

  6. CuCo2O4 ORR/OER Bi-functional catalyst: Influence of synthetic approach on performance

    DOE PAGES

    Serov, Alexey; Andersen, Nalin I.; Roy, Aaron J.; ...

    2015-02-07

    A series of CuCo2O4 catalysts were synthesized by pore forming, sol-gel, spray pyrolysis and sacrificial support methods. Catalysts were characterized by XRD, SEM, XPS and BET techniques. The electrochemical activity for the oxygen reduction and oxygen evolution reactions (ORR and OER) was evaluated in alkaline media by RRDE. Density Functional Theory was used to identify two different types of active sites responsible for ORR/OER activity of CuCo2O4 and it was found that CuCo2O4 can activate the O-O bond by binding molecular oxygen in bridging positions between Co or Co and Cu atoms. It was found that the sacrificial support methodmore » (SSM) catalyst has the highest performance in both ORR and OER and has the highest content of phase-pure CuCo2O4. It was shown that the presence of CuO significantly decreases the activity in oxygen reduction and oxygen evolution reactions. As a result, the half-wave potential (E1/2) of CuCo2O4-SSM was found as 0.8 V, making this material a state-of-the-art, unsupported oxide catalyst.« less

  7. Understanding the effects of cationic dopants on α-MnO2 oxygen reduction reaction electrocatalysis

    DOE PAGES

    Lambert, Timothy N.; Vigil, Julian A.; White, Suzanne E.; ...

    2017-01-09

    Nickel-doped α-MnO2 nanowires (Ni–α-MnO2) were prepared with 3.4% or 4.9% Ni using a hydrothermal method. A comparison of the electrocatalytic data for the oxygen reduction reaction (ORR) in alkaline electrolyte versus that obtained with α-MnO2 or Cu–α-MnO2 is provided. In general, Ni-α-MnO2 (e.g., Ni-4.9%) had higher n values (n = 3.6), faster kinetics (k = 0.015 cm s–1), and lower charge transfer resistance (RCT = 2264 Ω at half-wave) values than MnO2 (n = 3.0, k = 0.006 cm s–1, RCT = 6104 Ω at half-wave) or Cu–α-MnO2 (Cu-2.9%, n = 3.5, k = 0.015 cm s–1, RCT = 3412more » Ω at half-wave), and the overall activity for Ni–α-MnO2 trended with increasing Ni content, i.e., Ni-4.9% > Ni-3.4%. As observed for Cu–α-MnO2, the increase in ORR activity correlates with the amount of Mn3+ at the surface of the Ni–α-MnO2 nanowire. Examining the activity for both Ni–α-MnO2 and Cu–α-MnO2 materials indicates that the Mn3+ at the surface of the electrocatalysts dictates the activity trends within the overall series. Single nanowire resistance measurements conducted on 47 nanowire devices (15 of α-MnO2, 16 of Cu–α-MnO2-2.9%, and 16 of Ni–α-MnO2-4.9%) demonstrated that Cu-doping leads to a slightly lower resistance value than Ni-doping, although both were considerably improved relative to the undoped α-MnO2. As a result, the data also suggest that the ORR charge transfer resistance value, as determined by electrochemical impedance spectroscopy, is a better indicator of the cation-doping effect on ORR catalysis than the electrical resistance of the nanowire.« less

  8. Oxygen reduction reaction catalyzed by cobalt(III) complexes of macrocyclic ligands supported on multiwalled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Nasini, Udaya B.; Gartia, Yashraj; Ramidi, Punnamchandar; Kazi, Abul; Shaikh, Ali U.; Ghosh, Anindya

    2013-04-01

    A class of amido-macrocyclic cobalt(III) complexes along with multiwalled carbon nanotubes have been studied for electro-catalytic activity to reduce oxygen. These complexes are efficient for oxygen reduction reaction (ORR) in wide range of pH conditions by following ideal fuel cell reduction mechanism. Depending on the stability of complexes in different pH, electrochemical studies were performed to predict the reduction mechanism. Rotating disk electrode and rotating ring-disk electrode studies show that these complexes reduce oxygen via four electron reduction process in mild acidic pH and two step two electron reduction processes in basic conditions, with negligible amount of hydrogen peroxide generation.

  9. Porous Dendritic Platinum Nanotubes with Extremely High Activity and Stability for Oxygen Reduction Reaction

    PubMed Central

    Zhang, Gaixia; Sun, Shuhui; Cai, Mei; Zhang, Yong; Li, Ruying; Sun, Xueliang

    2013-01-01

    Controlling the morphology of Pt nanostructures can provide opportunities to greatly increase their activity and stability. Porous dendritic Pt nanotubes were successfully synthesized by a facile, cost-effective aqueous solution method at room temperature in large scale. These unique structures are porous, hollow, hierarchical, and single crystalline, which not only gives them a large surface area with high catalyst utilization, but also improves mass transport and gas diffusion. These novel Pt structures exhibited significantly improved catalytic activity (4.4 fold) for oxygen reduction reaction (ORR) and greatly enhanced durability (6.1 fold) over that of the state-of-the-art commercial Pt/C catalyst. This work provides a promising approach to the design of highly efficient next-generation electrocatalysts. PMID:23524665

  10. PGM-free Fe-N-C catalysts for oxygen reduction reaction: Catalyst layer design

    NASA Astrophysics Data System (ADS)

    Stariha, Sarah; Artyushkova, Kateryna; Workman, Michael J.; Serov, Alexey; Mckinney, Sam; Halevi, Barr; Atanassov, Plamen

    2016-09-01

    This work studies the morphology of platinum group metal-free (PGM-free) iron-nitrogen-carbon (Fe-N-C) catalyst layers for the oxygen reduction reaction (ORR) and compares catalytic performance via polarization curves. Three different nitrogen-rich organic precursors are used to prepare the catalysts. Using scanning electron microscopy (SEM) and focused ion beam (FIB) tomography, the porosity, Euler number (pore connectivity), overall roughness, solid phase size and pore size are calculated for catalyst surfaces and volumes. Catalytic activity is determined using membrane electrode assembly (MEA) testing. It is found that the dominant factor in MEA performance is transport limitations. Through the 2D and 3D metrics it is concluded that pore connectivity has the biggest effect on transport performance.

  11. Functional MoS2 by the Co/Ni doping as the catalyst for oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Xiao, B. B.; Zhang, P.; Han, L. P.; Wen, Z.

    2015-11-01

    Since the discovery of the oxygen reduction reaction (ORR) activity of the metal phthalocyanine, the great enthusiasm is ignited for searching the catalysts with low price replacing Pt-based catalysts. Here, the catalytic activities for the ORR on the Co or Ni doped MoS2 are studied by using density-functional theory (DFT). It is found that Co/MoS2 resembles FeN4 active site while Ni/MoS2 is similar with CoN4 active site. In details, for Co/MoS2, under the acid medium, the rate-determining step (RDS) is located at the second H2O formation with a barrier of 1.49 eV. While under the alkaline medium, RDS is the final OH- formation with the barrier of 0.94 eV. For Ni/MoS2, under the acid medium, the RDS is the same as that of Co/MoS2 with a barrier of 0.87 eV. However, RDS is the O formation with the barrier of 0.92 eV under the alkaline medium. Furthermore, due to the intact HOOH adsorption, it is expected that the 2e- ORR is present on Ni/MoS2, which means inferior activity compared with Co/MoS2. Our calculation demonstrates the ability to functionalize inert materials for the ORR and provides new materials to design effective Pt-free catalysts for fuel-cell technology.

  12. Metal-Support Interactions of Platinum Nanoparticles Decorated N-Doped Carbon Nanofibers for the Oxygen Reduction Reaction.

    PubMed

    Melke, Julia; Peter, Benedikt; Habereder, Anja; Ziegler, Juergen; Fasel, Claudia; Nefedov, Alexei; Sezen, Hikmet; Wöll, Christof; Ehrenberg, Helmut; Roth, Christina

    2016-01-13

    N-doped carbon materials are discussed as catalyst supports for the electrochemical oxygen reduction reaction (ORR) in fuel cells. This work deals with the preparation of Pt nanoparticles (NPs) supported on N-doped carbon nanofibers (N-CNF) from a polyaniline nanofiber (PANI NF) precursor, and investigates the ORR activity of the produced materials. Initially, Pt NPs are deposited on PANI NFs. The PANI NF precursors are characterized by near-edge X-ray absorption fine structure (NEXAFS) and transmission electron microscopy (TEM) measurements. It is shown, that in the PANI NF precursor materials electrons from the Pt are being transferred toward the π-conjugated systems of the aromatic ring. This strong interaction of Pt atoms with PANI explains the high dispersion of Pt NPs on the PANI NF. Subsequently, the PANI NF precursors are carbonized at different heat-treatment conditions resulting in structurally different N-CNFs which are characterized by NEXAFS, X-ray photoelectron spectroscopy (XPS) ,and TEM measurements. It is shown that an interaction between N-groups and Pt NPs exists in all investigated N-CNFs. However, the N-CNFs differ in the composition of the N-species and the dispersion of the Pt NPs. A small mean Pt NP size with a narrow size distribution is attributed to the presence of pyrdinic N-groups in the N-CNFs, whereas, for the N-CNFs with mainly graphitic and pyrrolic N-groups, an increase in the average Pt NP size with a broad size distribution is found. The ORR activity in alkaline media investigated by Koutecky-Levich analysis of rotating disk electrode measurements showed a largely enhanced ORR activity in comparison to a conventional Pt/C catalyst.

  13. The secondary coordination sphere and axial ligand effects on oxygen reduction reaction by iron porphyrins: a DFT computational study.

    PubMed

    Ohta, Takehiro; Nagaraju, Perumandla; Liu, Jin-Gang; Ogura, Takashi; Naruta, Yoshinori

    2016-09-01

    Oxygen reduction reaction (ORR) catalyzed by a bio-inspired iron porphyrin bearing a hanging carboxylic acid group over the porphyrin ring, and a tethered axial imidazole ligand was studied by DFT calculations. BP86 free energy calculations of the redox potentials and pK a's of reaction components involved in the proton coupled electron transfer (PCET) reactions of the ferric-hydroxo and -superoxo complexes were performed based on Born-Haber thermodynamic cycle in conjunction with a continuum solvation model. The comparison was made with iron porphyrins that lack either in the hanging acid group or axial ligand, suggesting that H-bond interaction between the carboxylic acid and iron-bound hydroxo, aquo, superoxo, and peroxo ligands (de)stabilizes the Fe-O bonding, resulting in the increase in the reduction potential of the ferric complexes. The axial ligand interaction with the imidazole raises the affinity of the iron-bound superoxo and peroxo ligands for proton. In addition, a low-spin end-on ferric-hydroperoxo intermediate, a key precursor for O-O cleavage, can be stabilized in the presence of axial ligation. Thus, selective and efficient ORR of iron porphyrin can be achieved with the aid of the secondary coordination sphere and axial ligand interactions.

  14. Surface-Limited Synthesis of Pt Nanocluster Decorated Pd Hierarchical Structures with Enhanced Electrocatalytic Activity toward Oxygen Reduction Reaction.

    PubMed

    Yang, Tao; Cao, Guojian; Huang, Qingli; Ma, Yanxia; Wan, Sheng; Zhao, Hong; Li, Na; Sun, Xia; Yin, Fujun

    2015-08-12

    Exploring superior catalysts with high catalytic activity and durability is of significant for the development of an electrochemical device involving the oxygen reduction reaction. This work describes the synthesis of Pt-on-Pd bimetallic heterogeneous nanostructures, and their high electrocatalytic activity toward the oxygen reduction reaction (ORR). Pt nanoclusters with a size of 1-2 nm were generated on Pd nanorods (NRs) through a modified Cu underpotential deposition (UPD) process free of potential control and a subsequent surface-limited redox reaction. The Pt nanocluster decorated Pd nanostructure with a ultralow Pt content of 1.5 wt % exhibited a mass activity of 105.3 mA mg(-1) (Pt-Pd) toward ORR, comparable to that of the commercial Pt/C catalyst but 4 times higher than that of carbon supported Pd NRs. More importantly, the carbon supported Pt-on-Pd catalyst displays relatively small losses of 16% in electrochemical surface area (ECSA) and 32% in mass activity after 10 000 potential sweeps, in contrast to respective losses of 46 and 64% for the commercial Pt/C catalyst counterpart. The results demonstrated that Pt decoration might be an efficient way to improve the electrocatalytic activity of Pd and in turn allow Pd to be a promising substitution for commercial Pt catalyst.

  15. Pt-Decorated PdCo@Pd/C Core-Shell Nanoparticles with Enhanced Stability and Electrocatalytic Activity for the Oxygen Reduction Reaction

    SciTech Connect

    Wang, Deli; Xin, Huolin L.; Yu, Yingchao; Wang, Hongsen; Rus, Eric; Muller, David A.; Abruña, Héctor D.

    2010-11-24

    A simple method for the preparation of PdCo@Pd core-shell nanoparticles supported on carbon based on an adsorbate-induced surface segregation effect has been developed. The stability of these PdCo@Pd nanoparticles and their electrocatalytic activity for the oxygen reduction reaction (ORR) were enhanced by decoration with a small amount of Pt deposited via a spontaneous displacement reaction. The facile method described herein is suitable for large-scale, lower-cost production and significantly lowers the Pt loading and thus the cost. The as-prepared PdCo@Pd and Pd-decorated PdCo@Pd nanocatalysts have a higher methanol tolerance than Pt/C in the ORR and are promising cathode catalysts for fuel cell applications.

  16. A new Pt-Rh carbon nitride electrocatalyst for the oxygen reduction reaction in polymer electrolyte membrane fuel cells: Synthesis, characterization and single-cell performance

    NASA Astrophysics Data System (ADS)

    Di Noto, Vito; Negro, Enrico

    In this paper the preparation of a new bimetal electrocatalyst for the oxygen reduction reaction (ORR), which is one of the most important bottlenecks in the operation of polymer electrolyte membrane fuel cells (PEMFCs), is described. This material was synthesized through a pyrolysis process of a zeolitic inorganic-organic polymer electrolyte (Z-IOPE-like) precursor, followed by suitable washing and activation procedures of the product. The electrocatalyst, whose active sites consist of platinum and rhodium, was: (a) extensively characterized from the chemical, structural, morphological and electrochemical points of view and (b) used to prepare a membrane-electrode assembly (MEA) which was tested under operative conditions in a single-cell configuration. It was observed that, with respect to a reference material based on supported platinum, rhodium did not compromise the performance of the electrocatalyst in the ORR. This behaviour was interpreted in the framework of a general model concerning the enhancement of ORR performance in bimetal systems supported on carbon nitrides. Finally, the material shows a slightly better tolerance toward a few common contaminants for the ORR such as methanol and chloride anions, typical of direct methanol fuel cells (DMFCs) and vehicular applications, respectively.

  17. Hemoglobin-carbon nanotube derived noble-metal-free Fe5C2-based catalyst for highly efficient oxygen reduction reaction

    PubMed Central

    Vij, Varun; Tiwari, Jitendra N.; Lee, Wang-Geun; Yoon, Taeseung; Kim, Kwang S.

    2016-01-01

    High performance non-precious cathodic catalysts for oxygen reduction reaction (ORR) are vital for the development of energy materials and devices. Here, we report an noble metal free, Fe5C2 nanoparticles-studded sp2 carbon supported mesoporous material (CNTHb-700) as cathodic catalyst for ORR, which was prepared by pyrolizing the hybrid adduct of single walled carbon nanotubes (CNT) and lyophilized hemoglobin (Hb) at 700 °C. The catalyst shows onset potentials of 0.92 V in 0.1 M HClO4 and in 0.1 M KOH which are as good as commercial Pt/C catalyst, giving very high current density of 6.34 and 6.69 mA cm−2 at 0.55 V vs. reversible hydrogen electrode (RHE), respectively. This catalyst has been confirmed to follow 4-electron mechanism for ORR and shows high electrochemical stability in both acidic and basic media. Catalyst CNTHb-700 possesses much higher tolerance towards methanol than the commercial Pt/C catalyst. Highly efficient catalytic properties of CNTHb-700 could lead to fundamental understanding of utilization of biomolecules in ORR and materialization of proton exchange membrane fuel cells for clean energy production. PMID:26839148

  18. Synthesis of an excellent electrocatalyst for oxygen reduction reaction with supercritical fluid: Graphene cellular monolith with ultrafine and highly dispersive multimetallic nanoparticles

    NASA Astrophysics Data System (ADS)

    Zhou, Yazhou; Cheng, Xiaonong; Yen, Clive H.; Wai, Chien M.; Wang, Chongmin; Yang, Juan; Lin, Yuehe

    2017-04-01

    Graphene cellular monolith (GCM) can be used as an excellent support for nanoparticles in widespread applications. However, it's still a great challenge to deposit the desirable nanoparticles in GCM that have small size, controllable structure, composition, and high dispersion using the current methods. Here we demonstrate a green, efficient and large-scale method to address this challenge using supercritical fluid (SCF). By this superior method, graphene hydrogel can be transferred into GCM while being deposited with ultrafine and highly dispersive nanoparticles. Specifically, the bimetallic PtFe/GCM and the trimetallic PtFeCo/GCM catalysts are successfully synthesized, and their electrocatalytic performances toward oxygen reduction reaction (ORR) are also studied. The resultant PtFe/GCM shows the significant enhancement in ORR activity, including a factor of 8.47 enhancement in mass activity (0.72 A mgPt-1), and a factor of 7.67 enhancement in specific activity (0.92 mA cm-2), comparing with those of the commercial Pt/C catalyst (0.085 A mgPt-1, 0.12 mA cm-2). Importantly, by introducing the Co, the trimetallic PtFeCo/GCM exhibits the further improved ORR activities (1.28 A mgPt-1, 1.80 mA cm-2). The high ORR activity is probably attributed to the alloying structure, ultrafine size, highly dispersive, well-defined, and a better interface with 3D porous graphene support.

  19. 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.

  20. Hemoglobin-carbon nanotube derived noble-metal-free Fe5C2-based catalyst for highly efficient oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Vij, Varun; Tiwari, Jitendra N.; Lee, Wang-Geun; Yoon, Taeseung; Kim, Kwang S.

    2016-02-01

    High performance non-precious cathodic catalysts for oxygen reduction reaction (ORR) are vital for the development of energy materials and devices. Here, we report an noble metal free, Fe5C2 nanoparticles-studded sp2 carbon supported mesoporous material (CNTHb-700) as cathodic catalyst for ORR, which was prepared by pyrolizing the hybrid adduct of single walled carbon nanotubes (CNT) and lyophilized hemoglobin (Hb) at 700 °C. The catalyst shows onset potentials of 0.92 V in 0.1 M HClO4 and in 0.1 M KOH which are as good as commercial Pt/C catalyst, giving very high current density of 6.34 and 6.69 mA cm‑2 at 0.55 V vs. reversible hydrogen electrode (RHE), respectively. This catalyst has been confirmed to follow 4-electron mechanism for ORR and shows high electrochemical stability in both acidic and basic media. Catalyst CNTHb-700 possesses much higher tolerance towards methanol than the commercial Pt/C catalyst. Highly efficient catalytic properties of CNTHb-700 could lead to fundamental understanding of utilization of biomolecules in ORR and materialization of proton exchange membrane fuel cells for clean energy production.

  1. Low-Pt loaded on a vanadium nitride/graphitic carbon composite as an efficient electrocatalyst for the oxygen reduction reaction.

    PubMed

    Yin, Jie; Wang, Lei; Tian, Chungui; Tan, Taixing; Mu, Guang; Zhao, Lu; Fu, Honggang

    2013-10-04

    The high cost of platinum electrocatalysts for the oxygen reduction reaction (ORR) has hindered the commercialization of fuel cells. An effective support can reduce the usage of Pt and improve the reactivity of Pt through synergistic effects. Herein, the vanadium nitride/graphitic carbon (VN/GC) nanocomposites, which act as an enhanced carrier of Pt nanoparticles (NPs) towards ORR, have been synthesized for the first time. In the synthesis, the VN/GC composite could be obtained by introducing VO3 (-) and [Fe(CN)6 ](4-) ions into the polyacrylic weak-acid anion-exchanged resin (PWAR) through an in-situ anion-exchanged route, followed by carbonization and a subsequent nitridation process. After loading only 10 % Pt NPs, the resulting Pt-VN/GC catalyst demonstrates a more positive onset potential (1.01 V), higher mass activity (137.2 mA mg(-1) ), and better cyclic stability (99 % electrochemical active surface area (ECSA) retention after 2000 cycles) towards ORR than the commercial 20 % Pt/C. Importantly, the Pt-VN/GC catalyst mainly exhibits a 4 e(-) -transfer mechanism and a low yield of peroxide species, suggesting its potential application as a low-cost and highly efficient ORR catalyst in fuel cells.

  2. Direct Transformation from Graphitic C3N4 to Nitrogen-Doped Graphene: An Efficient Metal-Free Electrocatalyst for Oxygen Reduction Reaction.

    PubMed

    Li, Jiajie; Zhang, Yumin; Zhang, Xinghong; Han, Jiecai; Wang, Yi; Gu, Lin; Zhang, Zhihua; Wang, Xianjie; Jian, Jikang; Xu, Ping; Song, Bo

    2015-09-09

    Carbon-based nanomaterials provide an attractive perspective to replace precious Pt-based electrocatalysts for oxygen reduction reaction (ORR) to enhance the practical applications of fuel cells. Herein, we demonstrate a one-pot direct transformation from graphitic-phase C3N4 (g-C3N4) to nitrogen-doped graphene. g-C3N4, containing only C and N elements, acts as a self-sacrificing template to construct the framework of nitrogen-doped graphene. The relative contents of graphitic and pyridinic-N can be well-tuned by the controlled annealing process. The resulting nitrogen-doped graphene materials show excellent electrocatalytic activity toward ORR, and much enhanced durability and tolerance to methanol in contrast to the conventional Pt/C electrocatalyst in alkaline medium. It is determined that a higher content of N does not necessarily lead to enhanced electrocatalytic activity; rather, at a relatively low N content and a high ratio of graphitic-N/pyridinic-N, the nitrogen-doped graphene obtained by annealing at 900 °C (NGA900) provides the most promising activity for ORR. This study may provide further useful insights on the nature of ORR catalysis of carbon-based materials.

  3. Hemoglobin-carbon nanotube derived noble-metal-free Fe5C2-based catalyst for highly efficient oxygen reduction reaction.

    PubMed

    Vij, Varun; Tiwari, Jitendra N; Lee, Wang-Geun; Yoon, Taeseung; Kim, Kwang S

    2016-02-03

    High performance non-precious cathodic catalysts for oxygen reduction reaction (ORR) are vital for the development of energy materials and devices. Here, we report an noble metal free, Fe5C2 nanoparticles-studded sp(2) carbon supported mesoporous material (CNTHb-700) as cathodic catalyst for ORR, which was prepared by pyrolizing the hybrid adduct of single walled carbon nanotubes (CNT) and lyophilized hemoglobin (Hb) at 700 °C. The catalyst shows onset potentials of 0.92 V in 0.1 M HClO4 and in 0.1 M KOH which are as good as commercial Pt/C catalyst, giving very high current density of 6.34 and 6.69 mA cm(-2) at 0.55 V vs. reversible hydrogen electrode (RHE), respectively. This catalyst has been confirmed to follow 4-electron mechanism for ORR and shows high electrochemical stability in both acidic and basic media. Catalyst CNTHb-700 possesses much higher tolerance towards methanol than the commercial Pt/C catalyst. Highly efficient catalytic properties of CNTHb-700 could lead to fundamental understanding of utilization of biomolecules in ORR and materialization of proton exchange membrane fuel cells for clean energy production.

  4. NiFe layered double hydroxide/reduced graphene oxide nanohybrid as an efficient bifunctional electrocatalyst for oxygen evolution and reduction reactions

    NASA Astrophysics Data System (ADS)

    Zhan, Tianrong; Zhang, Yumei; Liu, Xiaolin; Lu, SiSi; Hou, Wanguo

    2016-11-01

    Highly active and low-cost bifunctional electrocatalysts for oxygen evolution and reduction reactions (OER and ORR) hold a heart position for the renewable energy technologies such as metal-air batteries and fuel cells. Here, we reported the synthesis of NiFe layered double hydroxide/reduced graphene oxide (NiFe-LDH/rGO) nanohybrid via the facile solvothermal method followed by chemical reduction. The template role of surfactant and the hybridization of rGO supplied the NiFe-LDH/rGO catalyst with a porous nanostructure and an enhanced conductivity, favoring both mass transport and charge communication of electrocatalytic reactions. The NiFe-LDH/rGO composite not only displayed highly efficient OER activity in alkaline solution with a low onset overpotential of 240 mV, but also only needed an overpotential of 250 mV to reach the 10 mA cm-2 current density. The NiFe-LDH/rGO nanohybrid also offered excellent ORR catalytic activity with onset potential at 0.796 V in alkaline media. The rotating-disk and rotating-ring-disk electrodes both revealed that the ORR on NiFe-LDH/rGO mainly involved a direct four-electron reaction pathways accompanying part of the two-electron process. The excellent bifunctional activity of the NiFe-LDH/rGO nanohybrid could be attributed to the synergistic effects of rGO and NiFe-LDH components due to the strongly coupled interactions.

  5. First principles design of the Pd/Co/Pd sandwich-like structure as a promising electrocatalyst for the oxygen reduction reaction on hydrogen fuel cell cathode

    NASA Astrophysics Data System (ADS)

    Zuluaga, Sebastian; Stolbov, Sergey

    2012-02-01

    In the search of Pt free catalytic materials, experiments have shown an enhancement in the catalytic activity of Pd-Co alloys over Pd surfaces, comparable to the one obtained with Pt, as well as a Pd enrichment of the topmost layers. In this work we present the rational design of a new catalyst material towards the oxygen reduction reaction (ORR) consisting on Pd(111) surface sandwiched with Co as the second layer (Pd/Co/Pd). The calculated reaction free energy diagrams confirm that the proposed sandwich-like structure is highly active towards ORR. The higher catalytic activity of the Pd/Co/Pd system is traced to the change in the electronic local density of states of the Pd surface atoms. Namely the hybridization of the Pd d-states with the Co majority-spin band causes a low-energy shift of the Pd d-band. This results in a reduction of surface reactivity which is favorable for ORR. We have also studied form first principles the stability of the system and evaluated the dissolution potential of Pd in Pd/Co/Pd. The results suggest that the system will be stable in the reaction environment.

  6. ORR viability of alumina-supported platinum nanocluster: exploring oxidation behaviour by DFT.

    PubMed

    Nigam, Sandeep; Majumder, Chiranjib

    2017-07-26

    While alumina-supported platinum particles are versatile for several oxidation reactions, their viability as ORR catalysts has not been explored to date. Therefore, to assess the prospects of alumina-supported platinum nanoclusters in ORRs, a systematic DFT study has been carried out to explore the oxidation behavior of a Ptn@Al2O3 (n = 1-7, 10) cluster. The results are compared with the oxidation behavior of the corresponding gas phase platinum cluster and that of an extended Pt(111) slab. Both supported and unsupported clusters activate adsorbed oxygen molecules and energetically favor dissociative chemisorption of oxygen, leading to stable oxide formation with Pt-O-Pt linkages. However, the influence of the alumina substrate downshifts the d-band centre of the platinum cluster, which not only reduces the reaction enthalpy of oxidation by 8-10%, but also elongates the Pt-O bond of the oxide product by 3-8%. These observations indicate that removal of oxide will be relatively easier for supported clusters than for unsupported clusters. Cluster binding is found to sustain during oxidation, as oxidation of the platinum host cluster results in reduction of the distance between the cluster and support surface. While the gas phase Pt10 cluster does not show any similarity to the oxidation behavior shown by THE Pt(111) slab, the Pt10@Al2O3 cluster reveals close resemblance. Both the Pt(111) slab and Pt10@Al2O3 cluster form similar oxide products, having tri-coordinated oxygen with comparable Pt-O bond distances. The observed resemblance has been attributed to the similarity in the electronic structure and d-band centre position of the platinum surface and alumina-supported Pt10 cluster. Whilst this similar oxidation behaviour of the Pt10@Al2O3 cluster endorses its viability as an ORR catalyst, further modulation of this catalyst is desirable to improve its potential.

  7. Oxygen reduction reaction on anisotropic silver nanoparticles in alkaline media

    NASA Astrophysics Data System (ADS)

    Gupta, Rajeev Kumar; Verma, A. D.; Sinha, I.; Malviya, Manisha

    2017-07-01

    The effect of anisotropy of Ag nanoparticles on their electrocatalytic activity was investigated. By using increasing amounts of Cu salt etchant, we could obtain two AgNPs samples (S1 and S2) with different percentages of anisotropic nanoparticles. The third AgNPs sample was synthesized in the absence of any etchant and therefore resulted in the formation of only spherical nanoparticles. Investigation of ORR activity in an alkaline solution of these AgNPs samples showed that the S1/GC electrode gives rise to better reduction peak current, more positive reduction peak potential and stable electrocatalytic performance. Better results for the S1/GC electrode as compared to S2/GC electrode & S3/GC electrode can be owed to a higher percentage of anisotropic nanoparticles in S1 sample.

  8. 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

  9. Cobalt-manganese-based spinels as multifunctional materials that unify catalytic water oxidation and oxygen reduction reactions.

    PubMed

    Menezes, Prashanth W; Indra, Arindam; Sahraie, Nastaran Ranjbar; Bergmann, Arno; Strasser, Peter; Driess, Matthias

    2015-01-01

    Recently, there has been much interest in the design and development of affordable and highly efficient oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) catalysts that can resolve the pivotal issues that concern solar fuels, fuel cells, and rechargeable metal-air batteries. Here we present the synthesis and application of porous CoMn2 O4 and MnCo2 O4 spinel microspheres as highly efficient multifunctional catalysts that unify the electrochemical OER with oxidant-driven and photocatalytic water oxidation as well as the ORR. The porous materials were prepared by the thermal degradation of the respective carbonate precursors at 400 °C. The as-prepared spinels display excellent performances in electrochemical OER for the cubic MnCo2 O4 phase in comparison to the tetragonal CoMn2 O4 material in an alkaline medium. Moreover, the oxidant-driven and photocatalytic water oxidations were performed and they exhibited a similar trend in activity to that of the electrochemical OER. Remarkably, the situation is reversed in ORR catalysis, that is, the oxygen reduction activity and stability of the tetragonal CoMn2 O4 catalyst outperformed that of cubic MnCo2 O4 and rivals that of benchmark Pt catalysts. The superior catalytic performance and the remarkable stability of the unifying materials are attributed to their unique porous and robust microspherical morphology and the intrinsic structural features of the spinels. Moreover, the facile access to these high-performance materials enables a reliable and cost-effective production on a large scale for industrial applications.

  10. Synthesis of Pd9Ru@Pt nanoparticles for oxygen reduction reaction in acidic electrolytes

    SciTech Connect

    Sun, Yu; Hsieh, Yu -Chi; Chang, Li -Chung; Wu, Pu -Wei; Lee, Jyh -Fu

    2014-11-22

    Nanoparticles of PdRu, Pd₃Ru, and Pd₉Ru are synthesized and impregnated on carbon black via a wet chemical reflux process. X-ray diffraction patterns of the as-synthesized samples, PdxRu/C (x=1/3/9), suggest succesful formation of alloy without presence of individual Pd and Ru nanoparticles. Images from transmission electron microscope confirm irregularly-shaped nanoparticles with average size below 3 nm. Analysis from extended X-ray absorption fine structure on both Pd and Ru K-edge absorption profiles indicate the Ru atoms are enriched on the surface of PdxRu/C. Among these samples, the Pd₉Ru/C exhibits the strongest electrocatalytic activity for oxygen reduction reaction (ORR) in an oxygen-saturated 0.1 M aqueous HClO₄ solution. Subsequently, the Pd₉Ru/C undegoes Cu under potential deposition, followed by a galvanic displacement reaction to deposit a Pt monolayer on the Pd₉Ru surface (Pd₉Ru@Pt). The Pd₉Ru@Pt reveals better ORR performance than that of Pt, reaching a mass activity of 0.38 mA μg⁻¹ Pt, as compared to that of commercially available Pt nanoparticles (0.107 mA μg⁻¹ Pt). Thus, the mechanisms responsible for the ORR enhancement are attributed to the combined effects of lattice strain and ligand interaction. In addition, this core-shell Pd₉Ru@Pt electrocatalyst represents a substantial reduction in the amount of Pt consumption and raw material cost.

  11. 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

    2014-01-07

    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.

  12. Synergistic Effect of Nitrogen in Cobalt Nitride and Nitrogen-Doped Hollow Carbon Spheres for Oxygen Reduction Reaction

    SciTech Connect

    Zhong, Xing; Liu, Lin; Jiang, Yu; Wang, Xinde; Wang, Lei; Zhuang, Guilin; Li, Xiaonian; Mei, Donghai; Wang, Jian-guo; Su, Dang S.

    2015-06-15

    The need for inexpensive and high-activity oxygen reduction reaction (ORR) electrocatalysts has attracted considerable research interest over the past years. Here we report a novel hybrid that contains cobalt nitride/nitrogen-rich hollow carbon spheres (CoxN/NHCS) as a high-performance catalyst for ORR. The CoxN nanoparticles were uniformly dispersed and confined in the hollow NHCS shell. The performance of the resulting CoxN/NHCS hybrid was comparable with that of a commercial Pt/C at the same catalyst loading toward ORR, but the mass activity of the former was 5.7 times better than that of the latter. The nitrogen in both CoxN and NHCS, especially CoxN, could weaken the adsorption of reaction intermediates (O and OOH), which follows the favourable reaction pathway on CoxN/NHCS according to the DFT-calculated Gibbs free energy diagrams. Our results demonstrated a new strategy for designing and developing inexpensive, non-precious metal electrocatalysts for next-generation fuels. The authors acknowledge the financial support from the National Basic Research Program (973 program, No. 2013CB733501) and the National Natural Science Foundation of China (No. 21306169, 21101137, 21136001, 21176221 and 91334013). Dr. D. Mei is supported by the US Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences & Biosciences. Pacific Northwest National Laboratory (PNNL) is a multiprogram national laboratory operated for DOE by Battelle. Computing time was granted by the grand challenge of computational catalysis of the William R. Wiley Environmental Molecular Sciences Laboratory (EMSL). EMSL is a national scientific user facility located at Pacific Northwest National Laboratory (PNNL) and sponsored by DOE’s Office of Biological and Environmental Research.

  13. Graphite Carbon-Supported Mo2C Nanocomposites by a Single-Step Solid State Reaction for Electrochemical Oxygen Reduction

    PubMed Central

    Huang, K.; Bi, K.; Liang, C.; Lin, S.; Wang, W. J.; Yang, T. Z.; Liu, J.; Zhang, R.; Fan, D. Y.; Wang, Y. G.; Lei, M.

    2015-01-01

    Novel graphite-molybdenum carbide nanocomposites (G-Mo2C) are synthesized by a typical solid state reaction with melamine and MoO3 as precursors under inert atmosphere. The characterization results indicate that G-Mo2C composites are composed of high crystallization and purity of Mo2C and few layers of graphite carbon. Mo2C nanoparticles with sizes ranging from 5 to 50 nm are uniformly supported by surrounding graphite layers. It is believed that Mo atom resulting from the reduction of MoO3 is beneficial to the immobilization of graphite carbon. Moreover, the electrocatalytic performances of G-Mo2C for ORR in alkaline medium are investigated by cyclic voltammetry (CV), rotating disk electrode (RDE) and chronoamperometry test with 3M methanol. The results show that G-Mo2C has a considerable catalytic activity and superior methanol tolerance performance for the oxygen reduction reaction (ORR) benefiting from the chemical interaction between the carbide nanoparticles and graphite carbon. PMID:26381266

  14. Graphite Carbon-Supported Mo2C Nanocomposites by a Single-Step Solid State Reaction for Electrochemical Oxygen Reduction.

    PubMed

    Huang, K; Bi, K; Liang, C; Lin, S; Wang, W J; Yang, T Z; Liu, J; Zhang, R; Fan, D Y; Wang, Y G; Lei, M

    2015-01-01

    Novel graphite-molybdenum carbide nanocomposites (G-Mo2C) are synthesized by a typical solid state reaction with melamine and MoO3 as precursors under inert atmosphere. The characterization results indicate that G-Mo2C composites are composed of high crystallization and purity of Mo2C and few layers of graphite carbon. Mo2C nanoparticles with sizes ranging from 5 to 50 nm are uniformly supported by surrounding graphite layers. It is believed that Mo atom resulting from the reduction of MoO3 is beneficial to the immobilization of graphite carbon. Moreover, the electrocatalytic performances of G-Mo2C for ORR in alkaline medium are investigated by cyclic voltammetry (CV), rotating disk electrode (RDE) and chronoamperometry test with 3M methanol. The results show that G-Mo2C has a considerable catalytic activity and superior methanol tolerance performance for the oxygen reduction reaction (ORR) benefiting from the chemical interaction between the carbide nanoparticles and graphite carbon.

  15. Molybdenum nitrides as oxygen reduction reaction catalysts: Structural and electrochemical studies

    DOE PAGES

    Cao, Bingfei; Neuefeind, Joerg C.; Adzic, Radoslav R.; ...

    2015-02-09

    Monometallic (δ-MoN, Mo5N6, and Mo2N) and bimetallic molybdenum nitrides (Co0.6Mo1.4N2) were investigated as electrocatalysts for the oxygen reduction reaction (ORR), which is a key half-reaction in hydrogen fuel cells. Monometallic hexagonal molybdenum nitrides are found to exhibit improved activities over rock salt type molybdenum nitride (γ-Mo2N), suggesting that improvements are due to either the higher molybdenum valence or a more favorable coordination environment in the hexagonal structures. Further enhancements in activity were found for hexagonal bimetallic cobalt molybdenum nitride (Co0.6Mo1.4N2), resulting in a modest onset potential of 0.713 V versus reversible hydrogen electrode (RHE). Co0.6Mo1.4N2 exhibits good stability in acidicmore » environments, and in the potential range lower than 0.5 V versus RHE, the ORR appears to proceed via a four-electron mechanism based on the analysis of rotating disc electrode results. A redetermination of the structures of the binary molybdenum nitrides was carried out using neutron diffraction data, which is far more sensitive to nitrogen site positions than X-ray diffraction data. In conclusion, the revised monometallic hexagonal nitride structures all share many common features with the Co0.6Mo1.4N2 structure, which has alternating layers of cations in octahedral and trigonal prismatic coordination, and are thus not limited to only trigonal prismatic Mo environments (as was originally postulated for δ-MoN).« less

  16. Molybdenum nitrides as oxygen reduction reaction catalysts: Structural and electrochemical studies

    SciTech Connect

    Cao, Bingfei; Neuefeind, Joerg C.; Adzic, Radoslav R.; Khalifah, Peter G.

    2015-02-09

    Monometallic (δ-MoN, Mo5N6, and Mo2N) and bimetallic molybdenum nitrides (Co0.6Mo1.4N2) were investigated as electrocatalysts for the oxygen reduction reaction (ORR), which is a key half-reaction in hydrogen fuel cells. Monometallic hexagonal molybdenum nitrides are found to exhibit improved activities over rock salt type molybdenum nitride (γ-Mo2N), suggesting that improvements are due to either the higher molybdenum valence or a more favorable coordination environment in the hexagonal structures. Further enhancements in activity were found for hexagonal bimetallic cobalt molybdenum nitride (Co0.6Mo1.4N2), resulting in a modest onset potential of 0.713 V versus reversible hydrogen electrode (RHE). Co0.6Mo1.4N2 exhibits good stability in acidic environments, and in the potential range lower than 0.5 V versus RHE, the ORR appears to proceed via a four-electron mechanism based on the analysis of rotating disc electrode results. A redetermination of the structures of the binary molybdenum nitrides was carried out using neutron diffraction data, which is far more sensitive to nitrogen site positions than X-ray diffraction data. In conclusion, the revised monometallic hexagonal nitride structures all share many common features with the Co0.6Mo1.4N2 structure, which has alternating layers of cations in octahedral and trigonal prismatic coordination, and are thus not limited to only trigonal prismatic Mo environments (as was originally postulated for δ-MoN).

  17. Rational syntheses of core-shell Fex@Pt nanoparticles for the study of electrocatalytic oxygen reduction reaction

    PubMed Central

    Jang, Ji-Hoon; Lee, Eunjik; Park, Jinwoo; Kim, Gunn; Hong, Suklyun; Kwon, Young-Uk

    2013-01-01

    We report on the syntheses of core-shell Fex@Pt (x = 0.4–1.2) nanoparticles (NPs) with Pt-shell thickness systematically controlled while the overall particle size is constant. The syntheses were achieved via one-pot ultrasound-assisted polyol synthesis (UPS) reactions. Fe1.2@Pt showed a record-breaking high core-element content (55 at%) of core-shell NPs. Based on observations from a series of control experiments, we propose a mechanism of the NPs' formation that enables control of shell thickness in UPS reactions. Fex@Pt NPs showed drastic enhancements in mass and specific activity for oxygen reduction reaction (ORR) and significantly enhanced durability compared to commercial Pt NPs. Fex@Pt with a 1 (monolayer) ML Pt shell showed the highest activity. The ab initio density functional theory calculations on the binding energies of oxygen species on the surfaces of Fex@Pt NPs showed that the 1 ML case is most favourable for the ORR, and in good agreement with the experimental results. PMID:24096587

  18. Carbon Nanotube/Boron Nitride Nanocomposite as a Significant Bifunctional Electrocatalyst for Oxygen Reduction and Oxygen Evolution Reactions.

    PubMed

    Patil, Indrajit M; Lokanathan, Moorthi; Ganesan, Balakrishnan; Swami, Anita; Kakade, Bhalchandra

    2017-01-12

    It is an immense challenge to develop bifunctional electrocatalysts for oxygen reduction reactions (ORR) and oxygen evolution reactions (OER) in low temperature fuel cells and rechargeable metal-air batteries. Herein, a simple and cost-effective approach is developed to prepare novel materials based on carbon nanotubes (CNTs) and a hexagonal boron nitride (h-BN) nanocomposite (CNT/BN) through a one-step hydrothermal method. The structural analysis and morphology study confirms the formation of a homogeneous composite and merging of few exfoliated graphene layers of CNTs on the graphitic planes of h-BN, respectively. Moreover, the electrochemical study implies that CNT/BN nanocomposite shows a significantly higher ORR activity with a single step 4-electron transfer pathway and an improved onset potential of +0.86 V versus RHE and a current density of 5.78 mA cm(-2) in alkaline conditions. Interestingly, it exhibits appreciably better catalytic activity towards OER at low overpotential (η=0.38 V) under similar conditions. Moreover, this bifunctional catalyst shows substantially higher stability than a commercial Pt/C catalyst even after 5000 cycles. Additionally, this composite catalyst does not show any methanol oxidation reactions that nullify the issues due to fuel cross-over effects in direct methanol fuel cell applications.

  19. 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

  20. Nitrogen-doped carbon with a high degree of graphitization derived from biomass as high-performance electrocatalyst for oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

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

    2017-02-01

    It is of great interest to develop metal-free electrocatalysts derived from cheap and environmental friendly biomass for oxygen reduction reaction (ORR). Here we report a facile method to prepare graphene-like N-doped carbons with a high degree of graphitization and large surface area using chitosan as precursor and FeCl3 as soft template. The graphitization degree, surface area and the N species can be simply adjusted by controlling the annealing temperature. The soft template induced sample annealed at 800 °C (STS800) exhibits more positive onset potential than the samples annealed at 600 °C and 1000 °C (-0.08 V compared to -0.12 V and -0.15 V), which demonstrates that all of the high degree of graphitization, large surface area and the high percentages of pyridinic-N and graphitic-N play curial roles in the good ORR activity. The value of onset potential for STS800 is just 25 mV negative than that for Pt/C (-0.08 V to -0.055 V) and the ORR current density at merely -0.3 V for STS800 (-2.16 mA cm-2) is larger than that for Pt/C (-2.12 mA cm-2), which indicates its superior ORR activity even compared to Pt/C. Besides, the current for STS800 retains 95% at -0.2 V in 30000 s while that for Pt/C just retains 88%, which reveals its longer durability. With the addition of 3 M methanol, the CV curve of STS800 shows no noticeable current attenuation, indicating its good methanol tolerance. The excellent ORR activity, good methanol tolerance, and long durability demonstrate that STS800 could be a promising alternative for costly Pt-based electrocatalysts.

  1. Design of Low Pt Concentration Electrocatalyst Surfaces with High Oxygen Reduction Reaction Activity Promoted by Formation of a Heterogeneous Interface between Pt and CeO(x) Nanowire.

    PubMed

    Chauhan, Shipra; Mori, Toshiyuki; Masuda, Takuya; Ueda, Shigenori; Richards, Gary J; Hill, Jonathan P; Ariga, Katsuhiko; Isaka, Noriko; Auchterlonie, Graeme; Drennan, John

    2016-04-13

    Pt-CeO(x) nanowire (NW)/C electrocatalysts for the improvement of oxygen reduction reaction (ORR) activity on Pt were prepared by a combined process involving precipitation and coimpregnation. A low, 5 wt % Pt-loaded CeO(x) NW/C electrocatalyst, pretreated by an optimized electrochemical conditioning process, exhibited high ORR activity over a commercially available 20 wt % Pt/C electrocatalyst although the ORR activity observed for a 5 wt % Pt-loaded CeO(x) nanoparticle (NP)/C was similar to that of 20 wt % Pt/C. To investigate the role of a CeO(x) NW promotor on the enhancement of ORR activity on Pt, the Pt-CeO(x) NW interface was characterized by using hard X-ray photoelectron spectroscopy (HXPS), transmission electron microscopy (TEM), and electron energy loss spectroscopy (EELS). Microanalytical data obtained by these methods were discussed in relation to atomistic simulation performed on the interface structures. The combined techniques of HXPS, TEM-EELS, and atomistic simulation indicate that the Pt-CeO(x) NW interface in the electrocatalyst contains two different defect clusters: Frenkel defect clusters (i.e., 2Pt(i)(••) - 4O(i)″ - 4V(o)(••) - V(Ce)″″) formed in the surface around the Pt-CeO(x) NW interface and Schottky defect clusters (i.e., (Pt(Ce)″ - 2V(O)(••) - 2Ce(Ce)') and (Pt(Ce)″ - V(O)(••))) which appear in the bulk of the Pt-CeO(x) NW interface similarly to Pt-CeO(x) NP/C. It is concluded that the formation of both Frenkel defect clusters and Schottky defect clusters at the Pt-CeO(x) NW heterointerface contributes to the promotion of ORR activity and permits the use of lower Pt-loadings in these electrocatalysts.

  2. In-situ formation of cobalt-phosphate oxygen-evolving complex-anchored reduced graphene oxide nanosheets for oxygen reduction reaction.

    PubMed

    Zhao, Zhi-Gang; Zhang, Jing; Yuan, Yinyin; Lv, Hong; Tian, Yuyu; Wu, Dan; Li, Qing-Wen

    2013-01-01

    Oxygen conversion process between O₂ and H₂O by means of electrochemistry or photochemistry has lately received a great deal of attention. Cobalt-phosphate (Co-Pi) catalyst is a new type of cost-effective artificial oxygen-evolving complex (OEC) with amorphous features during photosynthesis. However, can such Co-Pi OEC also act as oxygen reduction reaction (ORR) catalyst in electrochemical processes? The question remains unanswered. Here for the first time we demonstrate that Co-Pi OEC does be rather active for the ORR. Particularly, Co-Pi OEC anchoring on reduced graphite oxide (rGO) nanosheet is shown to possess dramatically improved electrocatalytic activities. Differing from the generally accepted role of rGO as an "electron reservoir", we suggest that rGO serves as "peroxide cleaner" in enhancing the electrocatalytic behaviors. The present study may bridge the gap between photochemistry and electrochemistry towards oxygen conversion.

  3. Porous nitrogen-doped carbon nanosheet on graphene as metal-free catalyst for oxygen reduction reaction in air-cathode microbial fuel cells.

    PubMed

    Wen, Qing; Wang, Shaoyun; Yan, Jun; Cong, Lijie; Chen, Ye; Xi, Hongyuan

    2014-02-01

    Porous nitrogen-doped carbon nanosheet on graphene (PNCN) was used as an alternative cathode catalyst for oxygen reduction reaction (ORR) in air-cathode microbial fuel cells (MFCs). Here we report a novel, low-cost, scalable, synthetic method for preparation of PNCN via the carbonization of graphite oxide-polyaniline hybrid (GO-PANI), subsequently followed by KOH activation treatment. Due to its high concentration of nitrogen and high specific surface area, PNCN exhibited an excellent catalytic activity for ORR. As a result, the maximum power density of 1159.34mWm(-2) obtained with PNCN catalyst was higher than that of Pt/C catalyst (858.49mWm(-2)) in a MFC. Therefore, porous nitrogen-doped carbon nanosheet could be a good alternative to Pt catalyst in MFCs.

  4. Anion adsorption, CO oxidation, and oxygen reduction reaction on a Au(100) surface: The pH effect

    SciTech Connect

    Blizanac, Berislav B.; Lucas, Chris A.; Gallagher, Mark E.; Arenz, Matthias; Ross, Philip N.; Markovic, Nenad M.

    2004-07-29

    The effects of pH on the surface reconstruction of Au(100), on CO oxidation, and on the oxygen reduction reaction (ORR) have been studied by a combination of surface X-ray scattering (SXS), Fourier transform infrared (FTIR) spectroscopy, and rotating ring-disk electrode (RRDE) measurements. In harmony with previous SXS and scanning tunneling microscopy (STM) results, the potential-induced hexagonal (''hex'') to (1 x 1) transition occurs faster in an alkaline electrolyte than in acidic media. In alkaline solution, CO adsorption facilitates the formation of a ''hex'' phase; in acid solution, however, CO has negligible effect on the potential range of thermodynamic stability of the ''hex'' <--> (1 x 1) transition. We propose that in KOH the continuous removal of OHad in the Langmuir-Hinshelwood reaction (CO + OH) CO2 + H+ + e- may stabilize the ''hex'' phase over a much wider potential range than in CO-free solution. In acid solution, where specifically adsorbing anions cannot be displaced by CO from the Au(100) surface, CO has negligible effect on the equilibrium potential for the ''hex'' <--> (1 x 1) transition. Such a mechanism is in agreement with the pH-dependent oxidation of CO. The ORR is also affected by the pH of solution. It is proposed that the pH-dependent kinetics of the ORR on Au(100) can be unraveled by finding the relationship between kinetic rates and two terms: (i) the energetic term of the Au(100)-O2- interaction determines the potential regions where the rate-determining step O2 + e = O2- occurs, and (ii) the preexponential term determines the availability of active sites for the adsorption of O2-.

  5. Iridium-decorated palladium-platinum core-shell catalysts for oxygen reduction reaction in proton exchange membrane fuel cell.

    PubMed

    Wang, Chen-Hao; Hsu, Hsin-Cheng; Wang, Kai-Ching

    2014-08-01

    Carbon-supported Pt, Pd, Pd-Pt core-shell (Pt(shell)-Pd(core)/C) and Ir-decorated Pd-Pt core-shell (Ir-decorated Pt(shell)-Pd(core)/C) catalysts were synthesized, and their physical properties, electrochemical behaviors, oxygen reduction reaction (ORR) characteristics and proton exchange membrane fuel cell (PEMFC) performances were investigated herein. From the XRD patterns and TEM images, Ir-decorated Pt(shell)-Pd(core)/C has been confirmed that Pt was deposited on the Pd nanoparticle which had the core-shell structure. Ir-decorated Pt(shell)-Pd(core)/C has more positive OH reduction peak than Pt/C, which is beneficial to weaken the binding energy of Pt-OH during the ORR. Thus, Ir-decorated Pt(shell)-Pd(core)/C has higher ORR activity than Pt/C. The maximum power density of H2-O2 PEMFC using Ir-decorated Pt(shell)-Pd(core)/C is 792.2 mW cm(-2) at 70°C, which is 24% higher than that using Pt/C. The single-cell accelerated degradation test of PEMFC using Ir-decorated Pt(shell)-Pd(core)/C shows good durability by the potential cycling of 40,000 cycles. This study concludes that Ir-decorated Pt(shell)-Pd(core)/C has the low Pt content, but it can facilitate the low-cost and high-efficient PEMFC. Copyright © 2013 Elsevier Inc. All rights reserved.

  6. 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

  7. Enhanced methanol oxidation and oxygen reduction reactions on palladium-decorated FeCo@Fe/C core-shell nanocatalysts in alkaline medium.

    PubMed

    Fashedemi, Omobosede O; Ozoemena, Kenneth I

    2013-12-28

    Palladium based nano-alloys are well known for their unique electrocatalytic properties. In this work, a palladium-decorated FeCo@Fe/C core-shell nanocatalyst has been prepared by a new method called microwave-induced top-down nanostructuring and decoration (MITNAD). This simple, yet efficient technique, resulted in the generation of sub-10 nm sized FeCo@Fe@Pd nanocatalysts (mainly 3-5 nm) from a micron-sized (0.21-1.5 μm) FeCo@Fe/C. The electrocatalytic activities of the core-shell nanocatalysts were explored for methanol oxidation reaction (MOR) and oxygen reduction reaction (ORR) in alkaline medium. A negative shift of 300 mV in the onset potential for MOR was observed, with a current thrice that of the Pd/C catalysts. A very low resistance to electron transfer (Rct) was observed while the ratio of forward-to-backward oxidation current (If/Ib) was doubled. The overpotential of ORR was significantly reduced with a positive shift of about 250 mV and twice the reduction current density was observed in comparison with Pd/C nanocatalysts with the same mass loading. The kinetic parameters (in terms of the Tafel slope (b) = -59.7 mV dec(-1) (Temkin isotherm) and high exchange current density (jo) = 1.26 × 10(-2) mA cm(-2)) provide insights into the favorable electrocatalytic performance of the catalysts in ORR in alkaline media. Importantly, the core-shell nanocatalyst exhibited excellent resistance to possible methanol cross-over during ORR, which shows excellent promise for application in direct alkaline alcohol fuel cells (DAAFCs).

  8. Oxygen Reduction Reaction on Platinum-Terminated “Onion-structured” Alloy Catalysts

    SciTech Connect

    Herron, Jeffrey A.; Jiao, Jiao; Hahn, Konstanze; Peng, Guowen; Adzic, Radoslav R.; Mavrikakis, Manos

    2012-12-17

    Using periodic, self-consistent density functional theory (GGA-PW91) calculations, a series of onion-structured metal alloys have been investigated for their catalytic performance towards the oxygen reduction reaction (ORR). The onion-structures consist of a varying number of atomic layers of one or two metals each, pseudomorphically deposited on top of one another to form the overall structure. All catalysts studied feature a Pt overlayer, and often consist of at least one Pd layer below the surface. Three distinct ORR mechanisms were analyzed on the close-packed facets of all the structures considered. These mechanisms include a direct route of O2 dissociation and two hydrogen-assisted routes of O–O bond-breaking in peroxyl (OOH) and in hydrogen peroxide (HOOH) intermediates. A thermochemical analysis of the elementary steps provides information on the operating potential, and thereby energy efficiency of each electrocatalyst. A Sabatier analysis of catalytic activity based on thermochemistry of proton/electron transfer steps and activation energy barrier for O–O bond-breaking steps leads to a “volcano” relation between the surfaces’ activity and the binding energy of O. Several of the onion-structured alloys studied here show promise for achieving energy efficiency higher than that of Pt, by being active at potentials higher than the operating potential of Pt. Furthermore, some have at least as good activity as pure Pt at that operating potential. Thus, a number of the onion-structured alloys studied here are promising as cathode electrocatalysts in proton exchange membrane fuel cells.

  9. Titanium cobalt nitride supported platinum catalyst with high activity and stability for oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Xiao, Yonghao; Zhan, Guohe; Fu, Zhenggao; Pan, Zhanchang; Xiao, Chumin; Wu, Shoukun; Chen, Chun; Hu, Guanghui; Wei, Zhigang

    2015-06-01

    We describe a facile route to the development of novel robust non-carbon titanium cobalt nitride (Ti0.9Co0.1N) used as a support for Pt, and the catalyst exhibits high activity and stability for the oxygen reduction reaction (ORR). XRD and TEM results show that the synthesized Ti0.9Co0.1N is formed as a single-phase solid solution with high purity. The XPS measurements verified the strong metal/support interaction between Pt nanoparticles (NPs) and the Ti0.9Co0.1N support. Most importantly, Ti0.9Co0.1N supported Pt catalyst (Pt/Ti0.9Co0.1N) exhibits a much higher mass activity and durability than that of the commercial JM Pt/C electrocatalyst for ORR. The accelerated durability test (ADT) reveals that the novel Ti0.9Co0.1N support can dramatically enhance the durability of the catalyst and maintain the electrochemical surface area (ECSA) of Pt. Pt/Ti0.9Co0.1N shows great improvement in ECSA preservation, with only 35% of the initial ECSA drop even after 10 000 ADT cycles. The experimental data indicate that the electronic structure of Pt can be modified by Co doping, and there exists a strong interaction between Pt and the Ti0.9Co0.1N support, both of them are playing an important role in improving the activity and durability of the Pt/Ti0.9Co0.1N catalyst.

  10. High-throughput characterization of Pt supported on thin film oxide material libraries applied in the oxygen reduction reaction.

    PubMed

    Schäfer, Dominik; Mardare, Cezarina; Savan, Alan; Sanchez, Miguel D; Mei, Bastian; Xia, Wei; Muhler, Martin; Ludwig, Alfred; Schuhmann, Wolfgang

    2011-03-15

    Thin film metal oxide material libraries were prepared by sputter deposition of nanoscale Ti/Nb precursor multilayers followed by ex situ oxidation. The metal composition was varied from 6 at.% Nb to 27 at.% Nb. Additionally, thin wedge-type layers of Pt with a nominal thickness gradient from 0 to 5 nm were sputter-deposited on top of the oxides. The materials libraries were characterized with respect to metallic film composition, oxide thickness, phases, electrical conductivity, Pt thickness, and electrochemical activity for the oxygen reduction reaction (ORR). Electrochemical investigations were carried out by cyclic voltammetry using an automated scanning droplet cell. For a nominal Pt thickness >1 nm, no significant dependence of the ORR activity on the Pt thickness or the substrate composition was observed. However, below that critical thickness, a strong decrease of the surface-normalized activity in terms of reduction currents and potentials was observed. For such thin Pt layers, the conductivity of the substrate seems to have a substantial impact on the catalytic activity. Results from X-ray photoelectron spectroscopy (XPS) measurements suggest that the critical Pt thickness coincides with the transition from a continuous Pt film into isolated particles at decreasing nominal Pt thickness. In the case of isolated Pt particles, the activity of Pt decisively depends on its ability to exchange electrons with the oxide layer, and hence, a dependence on the substrate conductivity is rationalized.

  11. Tuning oxygen reduction reaction activity via controllable dealloying: a model study of ordered Cu3Pt/C intermetallic nanocatalysts.

    PubMed

    Wang, Deli; Yu, Yingchao; Xin, Huolin L; Hovden, Robert; Ercius, Peter; Mundy, Julia A; Chen, Hao; Richard, Jonah H; Muller, David A; DiSalvo, Francis J; Abruña, Héctor D

    2012-10-10

    A promising electrocatalyst prototype of low Pt mole fraction, intermetallic nanoparticles of Cu(3)Pt, has been prepared using a simple impregnation-reduction method, followed by a post heat-treatment. Two dealloying methods (electrochemical and chemical) were implemented to control the atomic-level morphology and improve performance for the oxygen reduction reaction (ORR). The morphology and elemental composition of the dealloyed nanoparticles were characterized at angstrom resolution using an aberration-corrected scanning transmission electron microscope equipped with an electron energy loss spectrometer. We found that the electrochemical dealloying method led to the formation of a thin Pt skin of ca. 1 nm in thickness with an ordered Cu(3)Pt core structure, while chemical leaching gave rise to a "spongy" structure with no ordered structure being preserved. A three-dimensional tomographic reconstruction indicated that numerous voids were formed in the chemically dealloyed nanoparticles. Both dealloying methods yielded enhanced specific and mass activities toward the ORR and higher stability relative to Pt/C. The spongy nanoparticles exhibited better mass activity with a slightly lower specific activity than the electrochemically dealloyed nanoparticles after 50 potential cycles. In both cases, the mass activity was still enhanced after 5000 potential cycles.

  12. Nitrogen-doped MoS2/carbon as highly oxygen-permeable and stable catalysts for oxygen reduction reaction in microbial fuel cells

    NASA Astrophysics Data System (ADS)

    Hao, Liang; Yu, Jia; Xu, Xin; Yang, Liu; Xing, Zipeng; Dai, Ying; Sun, Ye; Zou, Jinlong

    2017-01-01

    Developing non-noble metal catalysts with high oxygen-permeability and activity for oxygen reduction reaction (ORR) is crucial for microbial fuel cells (MFCs). In this study, nitrogen-doped molybdenum disulfide/carbon (N-MoS2/C) is prepared using melamine as nitrogen and carbon sources. Ammonium molybdate, thiourea and Pluronic F127 are used as Mo source, S source and surfactant, respectively. Mo-S-melamine complex precursor is obtained through the evaporation-induced self-assembly route, which is then carbonized at 800, 900 and 1000 °C to fabricate N-MoS2/C. Defect-rich N-MoS2/C has a large number of exposed active sites and a high oxygen permeability. N-MoS2/C (900 °C) with regular honeycomb structure shows the maximum power density of 0.815 W m-2, which is far higher than that of Pt/C (0.520 W m-2) and only has a decline of 1.23% after 1800 h operation in MFCs. Four-electron (4e-) reduction of O2 is the main ORR pathway for N-MoS2/C (900 °C), attributing to the efficient permeation, adsorption, activation and reduction of O2 on the active sites. The synergy among abundant defects, N-species (pyridinic N, graphitic N and Mo-Nx) and high conductivity contributes to the promising ORR activity. This simple synthetic route of N-doped metal sulfides/carbon composites displays a new prospect for preparation of ORR catalyst.

  13. N,N‧-Bis(salicylidene)ethylenediamine as a nitrogen-rich precursor to synthesize electrocatalysts with high methanol-tolerance for polymer electrolyte membrane fuel cell oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Zhou, Xuejun; Xu, Pan; Xu, Li; Bai, Zhengyu; Chen, Zhongwei; Qiao, Jinli; Zhang, Jiujun

    2014-08-01

    A cost-effective chemical, N,N‧-bis(salicylidene)ethylenediamine (salen), is used as a ligand to form a carbon-supported Co-salen complex (Co-salen/C) by a simple solid-sate reaction. The Co-salen/C is then pyrolyzed at 600, 700, 800, 900, and 1000 °C to form carbon-supported Co-N-S/C catalysts for the oxygen reduction reaction (ORR). XRD, EDX, TEM, and XPS are used to characterize the catalysts' composition, crystalline nature, morphology, and possible surface groups induced by heat-treatment. Investigation of the catalytic activity and the ORR mechanisms using rotating disk electrode and rotating ring-disk electrode techniques demonstrates that all of these Co-N-S/C catalysts are highly active for the ORR in an O2-saturated 0.1 M KOH solution, but the catalyst heat treated at 700 °C gives the best ORR activity. The overall electron transfer number for the catalyzed ORR was determined to be 3.6-3.9, with 3.7-19.9% H2O2 production over the potential range of -0.05 to -0.60 V, suggesting that the ORR catalyzed by Co-N-S/C catalysts is dominated by a 4-electron transfer pathway from O2 to H2O. In addition, these catalysts exhibit superior methanol tolerance to commercial 40% Pt/C catalyst, thus the Co-N-S/C catalysts are promising for use as electrocatalysts in alkaline polymer electrolyte membrane fuel cells.

  14. "Wiring" Fe-Nx -Embedded Porous Carbon Framework onto 1D Nanotubes for Efficient Oxygen Reduction Reaction in Alkaline and Acidic Media.

    PubMed

    Ahn, Sung Hoon; Yu, Xingwen; Manthiram, Arumugam

    2017-07-01

    This study presents a novel metal-organic-framework-engaged synthesis route based on porous tellurium nanotubes as a sacrificial template for hierarchically porous 1D carbon nanotubes. Furthermore, an ultrathin Fe-ion-containing polydopamine layer has been introduced to generate highly effective FeNx C active sites into the carbon framework and to induce a high degree of graphitization. The synergistic effects between the hierarchically porous 1D carbon structure and the embedded FeNx C active sites in the carbon framework manifest in superior catalytic activity toward oxygen reduction reaction (ORR) compared to Pt/C catalyst in both alkaline and acidic media. A rechargeable zinc-air battery assembled in a decoupled configuration with the nonprecious pCNT@Fe@GL/CNF ORR electrode and Ni-Fe LDH/NiF oxygen evolution reaction (OER) electrode exhibits charge-discharge overpotentials similar to the counterparts of Pt/C ORR electrode and IrO2 OER electrode. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Interaction Induced High Catalytic Activities of CoO Nanoparticles Grown on Nitrogen-Doped Hollow Graphene Microspheres for Oxygen Reduction and Evolution Reactions

    PubMed Central

    Jiang, Zhong-Jie; Jiang, Zhongqing

    2016-01-01

    Nitrogen doped graphene hollow microspheres (NGHSs) have been used as the supports for the growth of the CoO nanoparticles. The nitrogen doped structure favors the nucleation and growth of the CoO nanoparticles and the CoO nanoparticles are mostly anchored on the quaternary nitrogen doped sites of the NGHSs with good monodispersity since the higher electron density of the quaternary nitrogen favors the nucleation and growth of the CoO nanoparticles through its coordination and electrostatic interactions with the Co2+ ions. The resulting NGHSs supported CoO nanoparticles (CoO/NGHSs) are highly active for the oxygen reduction reaction (ORR) with activity and stability higher than the Pt/C and for the oxygen evolution reaction (OER) with activity and stability comparable to the most efficient catalysts reported to date. This indicates that the CoO/NGHSs could be used as efficient bi-functional catalysts for ORR and OER. Systematic analysis shows that the superior catalytic activities of the CoO/NGHSs for ORR and OER mainly originate from the nitrogen doped structure of the NGHSs, the small size of the CoO nanoparticles, the higher specific and electroactive surface area of the CoO/NGHSs, the good electric conductivity of the CoO/NGHSs, the strong interaction between the CoO nanoparticles and the NGHSs, etc. PMID:27255562

  16. Oxygen reduction and evolution in an ionic liquid ([BMP][TFSA]) based electrolyte: A model study of the cathode reactions in Mg-air batteries

    NASA Astrophysics Data System (ADS)

    Law, Y. T.; Schnaidt, J.; Brimaud, S.; Behm, R. J.

    2016-11-01

    Aiming at a molecular scale understanding of the cathode processes in an Mg-air battery, we have investigated the oxygen reduction (ORR) and oxygen evolution (OER) reactions under well-defined conditions, using an ionic liquid (butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)amide, [BMP][TFSA]) based electrolyte and polycrystalline Au and glassy carbon, respectively, as model electrodes. Electrochemical measurements performed under enforced electrolyte flow provide information on the electrochemical and electrocatalytic properties of these electrodes, in particular on the reversibility of the ORR/OER both in the absence and in the presence of Mg2+ in the electrolyte, and on the build-up of a reaction inhibiting passivation layer (solid-electrolyte interphase). Further information on the nature of the deposits and their dependence both on the electrode material and on the potential cycling conditions is derived from scanning electron microscopy/energy dispersive X-ray spectroscopy and from X-ray photoelectron spectroscopy measurements performed ex situ after the electrochemical measurements. Consequences of these results on the understanding of the ORR/OER under these conditions and in particular of the nature and role of the solid-electrolyte interphase layer formed during potential cycling and their relevance for the operation of Mg-air batteries are discussed.

  17. Mesoporous TiN as a noncarbon support of Ag-rich PtAg nanoalloy catalysts for oxygen reduction reaction in alkaline media.

    PubMed

    Cui, Zhiming; Yang, Minghui; Chen, Hao; Zhao, Mengtian; DiSalvo, Francis J

    2014-12-01

    There has been growing interest in noncarbon supports for fuel cell reactions, especially for the oxygen reduction reaction (ORR) in alkaline media. Herein, we report a robust mesoporous titanium nitride (TiN) which is not only kinetically stable in alkaline media, but also electrochemically stable in the potential range of fuel cell operation. This binary nitride exhibits an order of magnitude higher electronic conductivity than carbon black. Bimetallic Ag-rich PtAg nanoalloy is selected as the catalyst for the ORR in alkaline media due to their superior activity and relatively low cost. TiN-supported Pt1 Ag9 nanoalloy catalysts are synthesized by a new and efficient approach with KEt3 BH as reducing agent and THF as solvent. Pt1 Ag9 /TiN exhibits much higher mass activity and durability for the ORR in alkaline media than Pt1 Ag9 /C, Pt/C and Ag/C catalysts, suggesting that mesoporous TiN is a very promising support in alkaline media. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  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.

  19. Nitrogen- and boron-co-doped core-shell carbon nanoparticles as efficient metal-free catalysts for oxygen reduction reactions in microbial fuel cells

    NASA Astrophysics Data System (ADS)

    Zhong, Shengkui; Zhou, Lihua; Wu, Ling; Tang, Lianfeng; He, Qiyi; Ahmed, Jalal

    2014-12-01

    The most severe bottleneck hindering the widespread application of fuel cell technologies is the difficulty in obtaining an inexpensive and abundant oxygen reduction reaction (ORR) catalyst. The concept of a heteroatom-doped carbon-based metal-free catalyst has recently attracted interest. In this study, a metal-free carbon nanoparticles-based catalyst hybridized with dual nitrogen and boron components was synthesized to catalyze the ORR in microbial fuel cells (MFCs). Multiple physical and chemical characterizations confirmed that the synthetic method enabled the incorporation of both nitrogen and boron dopants. The electrochemical measurements indicated that the co-existence of nitrogen and boron could enhance the ORR kinetics by reducing the overpotential and increasing the current density. The results from the kinetic studies indicated that the nitrogen and boron induced an oxygen adsorption mechanism and a four-electron-dominated reaction pathway for the as-prepared catalyst that was very similar to those induced by Pt/C. The MFC results showed that a maximum power density of ∼642 mW m-2 was obtained using the as-prepared catalyst, which is comparable to that obtained using expensive Pt catalyst. The prepared nitrogen- and boron-co-doped carbon nanoparticles might be an alternative cathode catalyst for MFC applications if large-scale applications and price are considered.

  20. Graphene supported Co-g-C3N4 as a novel metal-macrocyclic electrocatalyst for the oxygen reduction reaction in fuel cells.

    PubMed

    Liu, Qiao; Zhang, Junyan

    2013-03-19

    Graphitic carbon nitride (g-C3N4) polymer was doped with cobalt species and supported on a similar sp(2) structure graphene, to form a novel nitrogen-metal macrocyclic catalyst for the oxygen reduction reaction (ORR) in alkaline fuel cells. The structural characterizations confirmed the formation of Co-N bonds and the close electron coupling between Co-g-C3N4 and graphene sheets. The electrocatalytic measurements demonstrated Co-g-C3N4-catalyzed reduction of oxygen mainly in a four electron pathway. The improvement of ORR activity is closely related to the abundant accessible Co-Nx active sites and fast charge transfer at the interfaces of Co-g-C3N4/graphene. Also, Co-g-C3N4@graphene exhibited comparable ORR activity, better durability, and methanol tolerance ability in comparison to Pt/C, and bodes well for a promising non-noble cathode catalyst for the application of direct methanol fuel cells. The chemical doping strategy in this work would be helpful to improve other present catalysts for fuel cell applications.

  1. Anodically-grown TiO2 nanotubes: Effect of the crystallization on the catalytic activity toward the oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Sacco, Adriano; Garino, Nadia; Lamberti, Andrea; Pirri, Candido Fabrizio; Quaglio, Marzia

    2017-08-01

    In this work we investigated the behavior of TiO2 nanotube (NT) arrays, grown by anodic oxidation of Ti foil, as catalysts for the oxygen reduction reaction (ORR) in alkaline water solution. In particular, as-grown amorphous NTs were compared to crystalline anatase nanostructures, obtained following two different procedures, namely thermal and vapor-induced crystallizations. The catalytic activity of these materials toward the ORR was evaluated by cyclic voltammetry measurements. ORR polarization curves, combined with the rotating disk technique, indicated a predominant four-electrons reduction path, especially for crystalline samples. The effect of the structural characteristics of the investigated materials on the catalytic activity was analyzed in details by electrochemical impedance spectroscopy. The catalytic performance of the crystalline NTs is only slightly lower with respect to the reference material for fuel cell applications, namely platinum, but is in line with other cost-effective catalysts recently proposed in the literature. However, if compared to the larger part of these low-cost catalysts, anodically-grown TiO2 NTs are characterized by a synthesis route which is highly reproducible and easily up-scalable.

  2. Cobalt Nanoparticle-Embedded Porous Carbon Nanofibers with Inherent N- and F-Doping as Binder-Free Bifunctional Catalysts for Oxygen Reduction and Evolution Reactions.

    PubMed

    Singhal, Richa; Kalra, Vibha

    2017-01-18

    Efficient, low-cost, non-precious metal-based, and stable bifunctional electrocatalysts are key to various energy storage and conversion devices such as regenerative fuel cells and metal-air batteries. In this work, we report cobalt nanoparticle-embedded porous carbon nanofibers with inherent N- and F-doping as binder-free bifunctional electrocatalysts with excellent activity for both the oxygen reduction and oxygen evolution reaction (ORR/OER) in an alkaline medium. Single-step electrospinning of a solution of the polymer mixture (carbon precursor) and the cobalt precursor followed by controlled pyrolysis with an intermediate reduction step in H2 (to reduce cobalt oxides to cobalt) was utilized to synthesize an integrated freestanding catalyst. The fabricated catalyst with effective structural and electronic interaction between the cobalt metal nanoparticles and the N- and F-doped carbon defect sites showed enhanced catalytic properties compared to the benchmark catalysts for ORR and OER (Pt, Ir, and Ru). The ORR potential at the current density of -3 mA cm(-2) was 0.81 VRHE and the OER potential at a current density of 10 mA cm(-2) was 1.595 VRHE , resulting in a ΔE of only 0.785 V.

  3. Bimetallic PtAu superlattice arrays: Highly electroactive and durable catalyst for oxygen reduction and methanol oxidation reactions

    NASA Astrophysics Data System (ADS)

    Feng, Jiu-Ju; He, Li-Li; Fang, Rui; Wang, Qiao-Li; Yuan, Junhua; Wang, Ai-Jun

    2016-10-01

    Superlattice arrays, an important type of nanomaterials, have wide applications in catalysis, optic/electronics and energy storage for the synergetic effects determined by both individual metals and collective interactions. Herein, a simple one-pot solvothermal coreduction approach is developed for facile preparation of bimetallic PtAu alloyed superlattice arrays (PtAu SLAs) in oleylamine, with the assistance of urea via hydrogen bonding induced self-assembly. Urea is essential in morphology-controlled process and prevents PtAu nanoparticles from the disordered aggregation. The characterization and formation mechanism of PtAu SLAs are investigated in details. The as-synthesized hybrid nanocrystals exhibit enhanced electrocatalytic performances for oxygen reduction reaction (ORR) and methanol oxidation reaction (MOR) in alkaline electrolyte in comparison with commercial Pt-C (50%, wt.%) and Pt black catalysts.

  4. Mechanisms of Enhanced Electrocatalytic Activity for Oxygen Reduction Reaction on High-Index Platinum n(111)-(111) Surfaces.

    PubMed

    Yue, Jeffrey; Du, Zheng; Shao, Minhua

    2015-09-03

    Oxygen reduction reactions (ORRs) on high-index planes of Pt n(111)-(111) were studied by density functional theory (DFT). The stepped surfaces, where n = 2, 3, and 4, showed that O2, O, and OH exhibited higher binding energies along the step compared to the terrace plane. The Pt atoms along the step can become distorted through the binding of the O and OH, where the shift in position of the Pt atoms is the largest along the stepped sites, hence forming stronger bonds with O atoms. One of the two O atoms produced from the bond dissociation of O2 will push the other one down a step with lower binding energies, consequently reducing the energy required for the protonation reaction (O + H(+) → OH, and OH + H(+) → H2O). The quicker recovery back to the clean Pt surface would therefore improve the catalytic properties of Pt nanoparticles, especially those with exposure to high-indexed facets.

  5. Reaction Mechanism of the Multiple-Electron Oxygen Reduction Reaction on the Surfaces of Gold and Platinum Nanoparticles Loaded on Titanium(IV) Oxide.

    PubMed

    Kobayashi, Hisayoshi; Teranishi, Miwako; Negishi, Ryo; Naya, Shin-Ichi; Tada, Hiroaki

    2016-12-15

    Au and Pt nanoparticles with varying mean particle size and comparable loading amounts were loaded on the surface of TiO2 (Au/TiO2 and Pt/TiO2, respectively). The photocatalytic activities of Au/TiO2 and Pt/TiO2 for the oxygen reduction reaction (ORR) in an aerated aqueous solution containing 4% ethanol were compared under ultraviolet-light irradiation at 298 K. The initial rate of H2O2 generation (or H2O2 formation rate) in the Au/TiO2 system is much greater than that in the Pt/TiO2 system regardless of the metal particle size. To clarify the origin for the striking difference in the activity, the photocatalytic ORR on the model slabs (M28/(TiO2)32 and M50/(TiO2)96, M = Au and Pt) was simulated by density functional theory (DFT) calculations taking the solvation effect into consideration. The DFT calculations clearly show that regardless of the cluster size, H2O2 formation more easily occurs structurally and energetically for the Au/TiO2 system, whereas H2O is generated with the O-O bond cleavage in the Pt/TiO2 system.

  6. Detailed reduction of reaction mechanisms for flame modeling

    NASA Technical Reports Server (NTRS)

    Wang, Hai; Frenklach, Michael

    1991-01-01

    A method for reduction of detailed chemical reaction mechanisms, introduced earlier for ignition system, was extended to laminar premixed flames. The reduction is based on testing the reaction and reaction-enthalpy rates of the 'full' reaction mechanism using a zero-dimensional model with the flame temperature profile as a constraint. The technique is demonstrated with numerical tests performed on the mechanism of methane combustion.

  7. Micro-Membrane Electrode Assembly Design to Precisely Measure the in Situ Activity of Oxygen Reduction Reaction Electrocatalysts for PEMFC.

    PubMed

    Long, Zhi; Li, Yankai; Deng, Guangrong; Liu, Changpeng; Ge, Junjie; Ma, Shuhua; Xing, Wei

    2017-06-20

    An in situ micro-MEA technique, which could precisely measure the performance of ORR electrocatalyst using Nafion as electrolyte, was designed and compared with regular thin-film rotating-disk electrode (TFRDE) (0.1 M HClO4) and normal in situ membrane electrode assembly (MEA) tests. Compared to the traditional TFRDE method, the micro-MEA technique makes the acquisition of catalysts' behavior at low potential values easily achieved without being limited by the solubility of O2 in water. At the same time, it successfully mimics the structure of regular MEAs and obtains similar results to a regular MEA, thus providing a new technique to simply measure the electrode activity without being bothered by complicated fabrication of regular MEA. In order to further understand the importance of in situ measurement, Fe-N-C as a typical oxygen reduction reaction (ORR) free-Pt catalyst was evaluated by TFRDE and micro-MEA. The results show that the half wave potential of Fe-N-C only shifted negatively by -135 mV in comparison with state-of-the-art Pt/C catalysts from TFRDE tests. However, the active site density, mass transfer of O2, and the proton transfer conductivity are found to strongly influence the catalyst activity in the micro-MEA, thereby resulting in a much lower limiting current density than Pt/C (8.7 times lower). Hence, it is suggested that the micro-MEA is better in evaluating the in situ ORR performance, where the catalysts are characterized more thoroughly in terms of intrinsic activity, active site density, proton transfer, and mass transfer properties.

  8. NiCo2O4/N-doped graphene as an advanced electrocatalyst for oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Zhang, Hui; Li, Huiyong; Wang, Haiyan; He, Kejian; Wang, Shuangyin; Tang, Yougen; Chen, Jiajie

    2015-04-01

    Developing low-cost catalyst for high-performance oxygen reduction reaction (ORR) is highly desirable. Herein, NiCo2O4/N-doped reduced graphene oxide (NiCo2O4/N-rGO) hybrid is proposed as a high-performance catalyst for ORR for the first time. The well-formed NiCo2O4/N-rGO hybrid is studied by cyclic voltammetry (CV) curves and linear-sweep voltammetry (LSV) performed on the rotating-ring-disk-electrode (RDE) in comparison with N-rGO-free NiCo2O4 and the bare N-rGO. Due to the synergistic effect, the NiCo2O4/N-rGO hybrid exhibits significant improvement of catalytic performance with an onset potential of -0.12 V, which mainly favors a direct four electron pathway in ORR process, close to the behavior of commercial carbon-supported Pt. Also, the benefits of N-incorporation are investigated by comparing NiCo2O4/N-rGO with NiCo2O4/rGO, where higher cathodic currents, much more positive half-wave potential and more electron transfer numbers are observed for the N-doping one, which should be ascribed to the new highly efficient active sites created by N incorporation into graphene. The NiCo2O4/N-rGO hybrid could be used as a promising catalyst for high power metal/air battery.

  9. 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.

  10. New mechanistic insight into the oxygen reduction reaction on Ruddlesden-Popper cathodes for intermediate-temperature solid oxide fuel cells.

    PubMed

    Li, Wenyuan; Guan, Bo; Zhang, Xinxin; Yan, Jianhua; Zhou, Yue; Liu, Xingbo

    2016-03-28

    Ruddlesden-Popper (R-P) phase materials have been investigated widely as cathode candidates for IT-SOFCs. However, widespread application of R-P phase cathodes demands further improvement in electrode activity whose progress is hindered by the limited information in the oxygen reduction reaction (ORR). The ORR mechanism for the R-P phase is therefore investigated in this paper using (LaSr)2NiO(4±δ) as an example. Accurate characterization of the surface oxygen exchange process is realized by developing thin and dense polycrystalline LSNO layers via a versatile spray-modified pressing method we invented before to avoid perceptible bulk diffusion contribution, surface enrichment and geometry complication. The governing factors of the ORR are identified as oxygen adsorption and incorporation based on the findings in reaction orders from electrochemical impedance spectroscopy (EIS), stoichiometry-related chemical capacitance and intrinsic anisotropic properties. The incorporation rate is proven to drastically depend on the amount of interstitial oxygen (O(i)"). Since the unfilled interstitial sites(V(i)(×)) in the R-P phase serve to accommodate the adsorbed oxygen during incorporation, like vacancies in the perovskite structure (V(O)(••)), more O(i)" would seem to suppress the kinetics of this process. In regards to this, for the first time, a physical model is proposed to reconcile the discrepancy between the experimental results and intuitive reasoning. Based on supporting evidence, this model illustrates a possibility of how O(i)" works to regulate the exchange rate, and how the contradiction between V(O)(••) and O(i)" is harmonized so that the latter in the R-P structure also positively promotes the incorporation rate in the ORR.

  11. 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.

  12. Preparation and electrochemical properties of urchin-like La0.8Sr0.2MnO3 perovskite oxide as a bifunctional catalyst for oxygen reduction and oxygen evolution reaction

    NASA Astrophysics Data System (ADS)

    Jin, Chao; Cao, Xuecheng; Zhang, Liya; Zhang, Cong; Yang, Ruizhi

    2013-11-01

    An urchin-like La0.8Sr0.2MnO3 (LSM) perovskite oxide has been synthesized through a co-precipitation method with urea as a precipitator, and characterized by thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM) and BET analysis. SEM results show that a micro/nanocomposite with an urchin-like morphology has been obtained. The as-synthesized LSM perovskite oxide has a high specific surface area of 48 m2 g-1. The catalytic activity of the oxide for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) in 0.1 M KOH solution has been studied by using a rotating-ring-disk electrode (RRDE). In the ORR test, a maximum cathodic current density of 5.2 mA cm-2 at -1.0 V (vs. Ag/AgCl) with 2500 rpm was obtained, and the ORR mainly favors a direct four-electron pathway. The results of anodic linear scanning voltammograms indicate that the urchin-like LSM perovskite oxide exhibits an encouraging catalytic activity for the OER. All electrochemical measurements suggest that the urchin-like LSM perovskite oxide could be used as a bifunctional catalyst for the ORR and the OER.

  13. CuCo2O4 ORR/OER Bi-functional catalyst: Influence of synthetic approach on performance

    SciTech Connect

    Serov, Alexey; Andersen, Nalin I.; Roy, Aaron J.; Matanovic, Ivana; Artyushkova, Kateryna; Atanassov, Plamen

    2015-02-07

    A series of CuCo2O4 catalysts were synthesized by pore forming, sol-gel, spray pyrolysis and sacrificial support methods. Catalysts were characterized by XRD, SEM, XPS and BET techniques. The electrochemical activity for the oxygen reduction and oxygen evolution reactions (ORR and OER) was evaluated in alkaline media by RRDE. Density Functional Theory was used to identify two different types of active sites responsible for ORR/OER activity of CuCo2O4 and it was found that CuCo2O4 can activate the O-O bond by binding molecular oxygen in bridging positions between Co or Co and Cu atoms. It was found that the sacrificial support method (SSM) catalyst has the highest performance in both ORR and OER and has the highest content of phase-pure CuCo2O4. It was shown that the presence of CuO significantly decreases the activity in oxygen reduction and oxygen evolution reactions. As a result, the half-wave potential (E1/2) of CuCo2O4-SSM was found as 0.8 V, making this material a state-of-the-art, unsupported oxide catalyst.

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

    PubMed

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

    2014-12-21

    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.

  15. Electrospun interconnected Fe-N/C nanofiber networks as efficient electrocatalysts for oxygen reduction reaction in acidic media

    PubMed Central

    Wu, Nan; Wang, Yingde; Lei, Yongpeng; Wang, Bing; Han, Cheng; Gou, Yanzi; Shi, Qi; Fang, Dong

    2015-01-01

    One-dimensional electrospun nanofibers have emerged as a potential candidate for high-performance oxygen reduction reaction (ORR) catalysts. However, contact resistance among the neighbouring nanofibers hinders the electron transport. Here, we report the preparation of interconnected Fe-N/C nanofiber networks (Fe-N/C NNs) with low electrical resistance via electrospinning followed by maturing and pyrolysis. The Fe-N/C NNs show excellent ORR activity with onset and half-wave potential of 55 and 108 mV less than those of Pt/C catalyst in 0.5 M H2SO4. Intriguingly, the resulting Fe-N/C NNs exhibit 34% higher peak current density and superior durability than generic Fe-N/C ones with similar microstructure and chemical compositions. Additionally, it also displays much better durability and methanol tolerance than Pt/C catalyst. The higher electroactivity is mainly due to the more effective electron transport between the interconnected nanofibers. Thus, our findings provide a novel insight into the design of functional electrospun nanofibers for the application in energy storage and conversion fields. PMID:26615799

  16. Investigation of the electrocatalysis for oxygen reduction reaction by Pt and binary Pt alloys: an XRD, XAS and electrochemical study

    SciTech Connect

    Mukerjee, S.; McBreen, J.; Srinivasan, S.

    1995-12-31

    Electrocatalysis for the oxygen reduction reaction (ORR) on five binary Pt alloy electrocatalysts (PtCr/C, PtMn/C, PtFe/C, PtCo/C and PtNi/C) supported on carbon have been investigated. The electrochemical characteristics for ORR in a proton conducting fuel cell environment has been correlated with the electronic and structural parameters determined under in situ conditions using XANES and EXAFS technique respectively. Results indicate that all the alloys possess higher Pt 5d band vacancies as compared to Pt/C. There is also evidence of lattice contraction in the alloys (supported by XRD results). Further, the Pt/C shows increase in Pt 5 d band vacancies during potential transitions from 0.54 to 0.84 V vs. RHE, which has been ration@ on the basis of OH type adsorption. In contrast to this, the alloys do not exhibit such an enhancement. Detailed EXAFS analysis supports the presence of OH species on Pt/C and its relative absence in the alloys. Correlation of the electrochemical results with bond distances and d-band vacancies show a volcano type behavior with the PtCr/C on top of the curve.

  17. Potential of porous Co3O4 nanorods as cathode catalyst for oxygen reduction reaction in microbial fuel cells.

    PubMed

    Kumar, Ravinder; Singh, Lakhveer; Zularisam, A W; Hai, Faisal I

    2016-11-01

    This study aims to investigate the potential of porous Co3O4 nanorods as the cathode catalyst for oxygen reduction reaction (ORR) in aqueous air cathode microbial fuel cells (MFCs). The porous Co3O4 nanorods were synthesized by a facile and cost-effective hydrothermal method. Three different concentrations (0.5mg/cm(2), 1mg/cm(2), and 2mg/cm(2)) of Co3O4 nanorods coated on graphite electrodes were used to test its performance in MFCs. The results showed that the addition of porous Co3O4 nanorods enhanced the electrocatalytic activity and ORR kinetics significantly and the overall resistance of the system was greatly reduced. Moreover, the MFC with a higher concentration of the catalyst achieved a maximum power density of 503±16mW/m(2), which was approximately five times higher than the bare graphite electrode. The improved catalytic activity of the cathodes could be due to the porous properties of Co3O4 nanorods that provided the higher number of active sites for oxygen. Copyright © 2016 Elsevier Ltd. All rights reserved.

  18. Synergistic effect of Nitrogen-doped hierarchical porous carbon/graphene with enhanced catalytic performance for oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Kong, Dewang; Yuan, Wenjing; Li, Cun; Song, Jiming; Xie, Anjian; Shen, Yuhua

    2017-01-01

    Developing efficient and economical catalysts for the oxygen reduction reaction (ORR) is important to promote the commercialization of fuel cells. Here, we report a simple and environmentally friendly method to prepare nitrogen (N) -doped hierarchical porous carbon (HPC)/reduced graphene oxide (RGO) composites by reusing waste biomass (pomelo peel) coupled with graphene oxide (GO). This method is green, low-cost and without using any acid or alkali activator. The typical sample (N-HPC/RGO-1) contains 5.96 at.% nitrogen and larger BET surface area (1194 m2/g). Electrochemical measurements show that N-HPC/RGO-1 exhibits not only a relatively positive onset potential and high current density, but also considerable methanol tolerance and long-term durability in alkaline media as well as in acidic media. The electron transfer number is close to 4, which means that it is mostly via a four-electron pathway toward ORR. The excellent catalytic performance of N-HPC/RGO-1 is due to the synergistic effect of the inherent interwoven network structure of HPC, the good electrical conductivity of RGO, and the heteroatom doping for the composite. More importantly, this work demonstrates a good example for turning discarded rubbish into valuable functional products and addresses the disposal issue of waste biomass simultaneously for environment clean.

  19. Synergistic enhancement of nitrogen and sulfur co-doped graphene with carbon nanospheres insertion for electrocatalytic oxygen reduction reaction

    SciTech Connect

    Wu, Min; Xin, Huolin L.; Wang, Jie; Wu, Zexing; Wang, Deli

    2015-03-13

    A nitrogen and sulfur co-doped graphene/carbon black (NSGCB) nanocomposite for the oxygen reduction reaction (ORR) was synthesized through a one-pot annealing of a precursor mixture containing graphene oxide, thiourea, and acidized carbon black (CB). The NSGCB showed excellent performance for the ORR with the onset and half-way potentials at 0.96 V and 0.81 V (vs. RHE), respectively. It is significantly improved over that of the catalysts derived from only graphene (0.90 V and 0.76 V) or carbon nanosphere (0.82 V and 0.74 V). The enhanced catalytic activity on the NSGCB electrode could be attributed to the synergistic effect of N/S co-doping and the enlarged interlayer space resulted from the insertion of carbon nanosphere into the graphene sheets. The four-electron selectivity and the limiting current density of the NSGCB nanocomposite are comparable to that of the commercially Pt/C catalyst. Furthermore, the NSGCB nanocomposite was superior to Pt/C in terms of long-term durability and tolerance to methanol poisoning.

  20. Achieving Remarkable Activity and Durability toward Oxygen Reduction Reaction Based on Ultrathin Rh-Doped Pt Nanowires.

    PubMed

    Huang, Hongwen; Li, Kan; Chen, Zhao; Luo, Laihao; Gu, Yuqian; Zhang, Dongyan; Ma, Chao; Si, Rui; Yang, Jinlong; Peng, Zhenmeng; Zeng, Jie

    2017-06-21

    The research of active and sustainable electrocatalysts toward oxygen reduction reaction (ORR) is of great importance for industrial application of fuel cells. Here, we report a remarkable ORR catalyst with both excellent mass activity and durability based on sub 2 nm thick Rh-doped Pt nanowires, which combine the merits of high utilization efficiency of Pt atoms, anisotropic one-dimensional nanostructure, and doping of Rh atoms. Compared with commercial Pt/C catalyst, the Rh-doped Pt nanowires/C catalyst shows a 7.8 and 5.4-fold enhancement in mass activity and specific activity, respectively. The combination of extended X-ray absorption fine structure analysis and density functional theory calculations reveals that the compressive strain and ligand effect in Rh-doped Pt nanowires optimize the adsorption energy of hydroxyl and in turn enhance the specific activity. Moreover, even after 10000 cycles of accelerated durability test in O2 condition, the Rh-doped Pt nanowires/C catalyst exhibits a drop of 9.2% in mass activity, against a big decrease of 72.3% for commercial Pt/C. The improved durability can be rationalized by the increased vacancy formation energy of Pt atoms for Rh-doped Pt nanowires.

  1. Functional Species Encapsulated in Nitrogen-Doped Porous Carbon as a Highly Efficient Catalyst for the Oxygen Reduction Reaction.

    PubMed

    Song, Li; Wang, Tao; Ma, Yiou; Xue, Hairong; Guo, Hu; Fan, Xiaoli; Xia, Wei; Gong, Hao; He, Jianping

    2017-03-08

    The scarcity, high cost, and poor stability of precious metal-based electrocatalysts have stimulated the development of novel non-precious metal catalysts for the oxygen reduction reaction (ORR) for use in fuel cells and metal-air batteries. Here, we fabricated in situ a hybrid material (Co-W-C/N) with functional species (tungsten carbide and cobalt nanoparticles) encapsulated in an N-doped porous carbon framework, through a facile multi-constituent co-assembly method combined with subsequent annealing treatment. The unique structure favors the anchoring active nanoparticles and facilitates mass transfer steps. The homogenously distributed carbide nanoparticles and adjacent Co-N-C sites lead to the electrocatalytic synergism for the ORR. The existence of Co and W can promote the graphitization of the carbon matrix. Benefiting from its structural and material superiority, the Co-W-C/N electrocatalyst exhibits excellent electrocatalytic activity (with a half-wave potential of 0.774 V vs. reversible hydrogen electrode (RHE)), high stability (96.3 % of the initial current remaining after 9000 s of continuous operation), and good immunity against methanol in alkaline media.

  2. Exploring the catalytic activity of pristine T6[100] surface for oxygen reduction reaction: A first-principles study

    NASA Astrophysics Data System (ADS)

    Banerjee, Paramita; Chakrabarty, Soubhik; Thapa, Ranjit; Das, G. P.

    2017-10-01

    The electrocatalytic activity of T6[100] surface containing both sp3 (C1) and sp2 (C2) hybridized carbon atoms is explored using first-principles density functional theory based approach. The top layered C1 atom of the surface is found to be more active towards the oxygen reduction reaction (ORR), as compared to that of C2 atom. This is attributed to the presence of dangling σ bond in the corresponding C1 atom, leading to the high electron density near the Ferrmi level. Whereas, the π electron in the top layered C2 atom forms a weak out of plane network. As estimated from free energy profile, the overpotential is much lower when C1 is considered as the active site and the final step i.e desorption of final OH- ion is found to be the potential determining step. We have also reported the effect of Si dopant on the catalytic activity of T6[100] surface and explained the origin of high overpotential value in this case. Thus in this report, we propose a new metal-free catalyst i.e T6[100] surface, having both sp2 (maintains the high metallicity needed to reduce ohmic loss) and sp3 (helps in capturing the upcoming molecules) hybridized carbon atoms, as a potential candidate for ORR.

  3. Synergistic enhancement of nitrogen and sulfur co-doped graphene with carbon nanospheres insertion for electrocatalytic oxygen reduction reaction

    DOE PAGES

    Wu, Min; Xin, Huolin L.; Wang, Jie; ...

    2015-03-13

    A nitrogen and sulfur co-doped graphene/carbon black (NSGCB) nanocomposite for the oxygen reduction reaction (ORR) was synthesized through a one-pot annealing of a precursor mixture containing graphene oxide, thiourea, and acidized carbon black (CB). The NSGCB showed excellent performance for the ORR with the onset and half-way potentials at 0.96 V and 0.81 V (vs. RHE), respectively. It is significantly improved over that of the catalysts derived from only graphene (0.90 V and 0.76 V) or carbon nanosphere (0.82 V and 0.74 V). The enhanced catalytic activity on the NSGCB electrode could be attributed to the synergistic effect of N/Smore » co-doping and the enlarged interlayer space resulted from the insertion of carbon nanosphere into the graphene sheets. The four-electron selectivity and the limiting current density of the NSGCB nanocomposite are comparable to that of the commercially Pt/C catalyst. Furthermore, the NSGCB nanocomposite was superior to Pt/C in terms of long-term durability and tolerance to methanol poisoning.« less

  4. Effects of transition metal doping in Pt/M-TiO2 (M = V, Cr, and Nb) on oxygen reduction reaction activity

    SciTech Connect

    Kim, Jun-Hyuk; Kwon, Gihan; Lim, Hankwon; Zhu, Chenhui; You, Hoydoo; Kim, Yong-Tae

    2016-07-01

    High cost and low durability are unresolved issues that impede the commercialization of proton exchange membrane fuel cells (PEMFCs). To overcome these limitations, Pt/TiO2 is reported as an alternative electrocatalyst for enhancing the oxygen reduction reaction (ORR) activity and/or durability of the system. However, the low electrical conductivity of TiO2 is a drawback that may be addressed by doping. To date, most reports related to Pt/doped-TiO2 focus on changes in the catalyst activity caused by the Pt-TiO2 interaction (metal -support interaction), instead of the effect of doping itself; doping is merely considered to enhance the electrical conductivity of TiO2. In this study, we discuss the variation in the electronic fine structure of Pt caused by the dopant, and its correlation with the ORR activity. More extensive contraction of the Pt lattice in Pt/M-TiO2 (M = V, Cr, and Nb) relative to Pt/TiO2 and Pt/C leads to outstanding ORR specific activity of Pt/M-TiO2. Notably, a fourfold increase of the specific activity is achieved with Pt/V-TiO2 relative to Pt/C. Furthermore, an accelerated durability test (ADT) of Pt/V-TiO2 demonstrates that this system is three times more durable than conventional Pt/C due to the metal support interaction.

  5. Effects of transition metal doping in Pt/M-TiO2 (M = V, Cr, and Nb) on oxygen reduction reaction activity

    NASA Astrophysics Data System (ADS)

    Kim, Jun-Hyuk; Kwon, Gihan; Lim, Hankwon; Zhu, Chenhui; You, Hoydoo; Kim, Yong-Tae

    2016-07-01

    High cost and low durability are unresolved issues that impede the commercialization of proton exchange membrane fuel cells (PEMFCs). To overcome these limitations, Pt/TiO2 is reported as an alternative electrocatalyst for enhancing the oxygen reduction reaction (ORR) activity and/or durability of the system. However, the low electrical conductivity of TiO2 is a drawback that may be addressed by doping. To date, most reports related to Pt/doped-TiO2 focus on changes in the catalyst activity caused by the Pt-TiO2 interaction (metal-support interaction), instead of the effect of doping itself; doping is merely considered to enhance the electrical conductivity of TiO2. In this study, we discuss the variation in the electronic fine structure of Pt caused by the dopant, and its correlation with the ORR activity. More extensive contraction of the Pt lattice in Pt/M-TiO2 (M = V, Cr, and Nb) relative to Pt/TiO2 and Pt/C leads to outstanding ORR specific activity of Pt/M-TiO2. Notably, a fourfold increase of the specific activity is achieved with Pt/V-TiO2 relative to Pt/C. Furthermore, an accelerated durability test (ADT) of Pt/V-TiO2 demonstrates that this system is three times more durable than conventional Pt/C due to the metal-support interaction.

  6. Ultralow content of Pt on Pd–Co–Cu/C ternary nanoparticles with excellent electrocatalytic activity and durability for the oxygen reduction reaction

    DOE PAGES

    Liu, Sufen; Xiao, Weiping; Wang, Jie; ...

    2016-08-01

    Optimizing the utilization of Pt to catalyze the sluggish kinetics of the oxygen reduction reaction (ORR) is of vital importance in proton exchange membrane fuel cells. One of the strategies is to spread Pt atoms over the surface of a substrate to increase the surface area. We report a facile method to synthesize Pd6CoCu@Pt/C core-shell nanoparticles with an ultralow amount of Pt. It was found that Pt-coated layer on Pd6CoCu cores plays a vital role in enhancing the ORR activity and the cycling stability. The half-wave potential of Pd6CoCu@Pt/C positively shifts about 50 mV and 17 mV relative to Pd6CoCu/Cmore » and Pt/C, respectively. The Pt mass activity on Pd6CoCu@Pt/C was calculated to be about 27 times higher than that on Pt/C catalysts at 0.9 V. Furthermore, the Pd6CoCu@Pt/C nanoparticles exhibit superior stability with almost no decay for the ORR polarization curves during 10,000 potential cycles and the core-shell structure remains with only a slight increase in the thickness of the Pt overlayer. Our findings provide a methodology for synthesizing highly efficient catalytic materials for the cathodic application in fuel cells.« less

  7. Reduced graphene oxide supported MnS nanotubes hybrid as a novel non-precious metal electrocatalyst for oxygen reduction reaction with high performance

    NASA Astrophysics Data System (ADS)

    Tang, Yongfu; Chen, Teng; Guo, Wenfeng; Chen, Shunji; Li, Yanshuai; Song, Jianzheng; Chang, Limin; Mu, Shichun; Zhao, Yufeng; Gao, Faming

    2017-09-01

    Electronic structure of Mn cations, electric conductivity of active materials and three dimensional structure for mass transport play vital roles in the electrocatalytic activity of Mn-based electrocatalysts for oxygen reduction reaction (ORR). To construct efficient and robust Mn-based electrocatalysts, MnS nanotubes anchored on reduced graphene oxide (MnS-NT@rGO) hybrid was synthesized and used as a novel non-precious metal electrocatalyst for ORR. The formation of nano-tubular structure, which offers more active sites and suitable channels for mass transport to enhance the electrocatalytic activity towards ORR, are carefully illustrated based on the core-dissolution/shell-recrystallization type Ostwald ripening effect. Tuned electronic structure of Mn cations, enhanced electric conductivity and suitable nano-tubular structure endow MnS-NT@rGO electrocatalyst comparative catalytic activity to commercial 20 wt % Pt/C in alkaline electrolyte. The MnS-NT@rGO electrocatalyst exhibits higher catalytic activity than rGO supported MnS nanoparticles (MnS-NP@rGO) and MnS nanotubes without rGO substrate (MnS-NT), as well as rGO supported Mn(OH)2 (Mn(OH)2@rGO) and rGO supported MnO (MnO@rGO). Moreover, the MnS-NT@rGO electrocatalyst shows superior durability and methanol tolerance to commercial Pt/C.

  8. N, S co-doped carbon spheres with highly dispersed CoO as non-precious metal catalyst for oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Chen, Linlin; Guo, Xingpeng; Zhang, Guoan

    2017-08-01

    It is still a great challenge in preparing non-precious metal catalysts with high activity and long-term stability to substitute for precious metal catalysts for oxygen reduction reaction (ORR) in fuel cells. Herein, we report a novel and facile catalyst-N, S co-doped carbon spheres with highly dispersed CoO (CoO@NS-CSs), where biomass glucose spheres act as carbon precursor and H2S, NH3 derived from the decomposition of thiourea not only provide N, S sources but also can etch carbon spheres to produce nanoporous structure. CoO@NS-CSs catalyst exhibits excellent ORR activity with a high onset potential of 0.946 V vs. RHE (reversible hydrogen electrode) and a half-wave potential of 0.821 V vs. RHE through a four-electron pathway in alkaline solution, which is comparable to commercial Pt/C catalyst (onset potential: 0.926 V vs. RHE, half-wave potential: 0.827 V vs. RHE). Furthermore, both the long-term stability and methanol-tolerance of CoO@NS-CSs catalyst are superior to those of commercial Pt/C catalyst. The excellent ORR performance of CoO@NS-CSs catalyst can be attributed to its micro-mesopore structure, high specific surface area (667 m2 g-1), and highly dispersed CoO. This work manifests that the obtained CoO@NS-CSs catalyst is promising to be applied to fuel cells.

  9. Porous VOxNy nanoribbons supported on CNTs as efficient and stable non-noble electrocatalysts for the oxygen reduction reaction

    PubMed Central

    Huang, K.; Bi, K.; Lu, Y. K.; Zhang, R.; Liu, J.; Wang, W. J.; Tang, H. L.; Wang, Y. G.; Lei, M.

    2015-01-01

    Novel nanocomposites of carbon nanotubes supported porous VOxNy nonoribbons (VOxNy-CNTs) have been synthesized by the annealing of the sol-gel mixture of CNTs and V2O5 under NH3 atmosphere as well as the ageing process in air. Besides the morphological and structural characterizations revealed by TEM, SEAD, EDS, XRD and XPS measurements, typical electrochemical tests including cyclic voltammetry (CV), rotating disk electrode (RDE) and chronoamperometry have been employed to determine the oxygen reduction reaction (ORR) performance of VOxNy-CNTs. Inspiringly, the results indicate that VOxNy-CNTs catalyst exhibits a 0.4 mA/cm2 larger diffusion-limited current density, a 0.10  V smaller onset potential value, a 10.73% less of ORR current decay and an excellent methanol-tolerance compared with commercial Pt/C catalyst. Therefore, we have reasonable grounds to believe that this new VOxNy-CNTs nanocomposites can be regarded as a promising non-precious methanol-tolerant ORR catalyst candidate for alkaline fuel cells. PMID:26616719

  10. Pd-M/C (M = Pd, Cu, Pt) Electrocatalysts for Oxygen Reduction Reaction in Alkaline Medium: Correlating the Electronic Structure with Activity.

    PubMed

    Castegnaro, Marcus V; Paschoalino, Waldemir J; Fernandes, Mauro R; Balke, Benjamin; M Alves, Maria C; Ticianelli, Edson A; Morais, Jonder

    2017-03-21

    The increasing global needs for clean and renewable energy have fostered the design of new and highly efficient materials for fuel cells applications. In this work, Pd-M (M = Pd, Cu, Pt) and Pt nanoparticles were prepared by a green synthesis method. The carbon-supported nanoparticles were evaluated as electrocatalysts for the oxygen reduction reaction (ORR) in alkaline medium. A comprehensive electronic and structural characterization of these materials was achieved using X-ray diffraction, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, and X-ray absorption spectroscopy. Their electrochemical properties were investigated by cyclic voltammetry, while their activities for the ORR were characterized using steady-state polarization experiments. The results revealed that the bimetallic nanoparticles consist of highly crystalline nanoalloys with size around 5 nm, in which the charge transfer involving Pd and M atoms affects the activity of the electrocatalysts. Additionally, the samples with higher ORR activity are those whose d-band center is closer to the Fermi level.

  11. Ultralow content of Pt on Pd–Co–Cu/C ternary nanoparticles with excellent electrocatalytic activity and durability for the oxygen reduction reaction

    SciTech Connect

    Liu, Sufen; Xiao, Weiping; Wang, Jie; Zhu, Jing; Wu, Zexing; Xin, Huolin; Wang, Deli

    2016-08-01

    Optimizing the utilization of Pt to catalyze the sluggish kinetics of the oxygen reduction reaction (ORR) is of vital importance in proton exchange membrane fuel cells. One of the strategies is to spread Pt atoms over the surface of a substrate to increase the surface area. We report a facile method to synthesize Pd6CoCu@Pt/C core-shell nanoparticles with an ultralow amount of Pt. It was found that Pt-coated layer on Pd6CoCu cores plays a vital role in enhancing the ORR activity and the cycling stability. The half-wave potential of Pd6CoCu@Pt/C positively shifts about 50 mV and 17 mV relative to Pd6CoCu/C and Pt/C, respectively. The Pt mass activity on Pd6CoCu@Pt/C was calculated to be about 27 times higher than that on Pt/C catalysts at 0.9 V. Furthermore, the Pd6CoCu@Pt/C nanoparticles exhibit superior stability with almost no decay for the ORR polarization curves during 10,000 potential cycles and the core-shell structure remains with only a slight increase in the thickness of the Pt overlayer. Our findings provide a methodology for synthesizing highly efficient catalytic materials for the cathodic application in fuel cells.

  12. Ultralow content of Pt on Pd–Co–Cu/C ternary nanoparticles with excellent electrocatalytic activity and durability for the oxygen reduction reaction

    SciTech Connect

    Liu, Sufen; Xiao, Weiping; Wang, Jie; Zhu, Jing; Wu, Zexing; Xin, Huolin; Wang, Deli

    2016-08-01

    Optimizing the utilization of Pt to catalyze the sluggish kinetics of the oxygen reduction reaction (ORR) is of vital importance in proton exchange membrane fuel cells. One of the strategies is to spread Pt atoms over the surface of a substrate to increase the surface area. We report a facile method to synthesize Pd6CoCu@Pt/C core-shell nanoparticles with an ultralow amount of Pt. It was found that Pt-coated layer on Pd6CoCu cores plays a vital role in enhancing the ORR activity and the cycling stability. The half-wave potential of Pd6CoCu@Pt/C positively shifts about 50 mV and 17 mV relative to Pd6CoCu/C and Pt/C, respectively. The Pt mass activity on Pd6CoCu@Pt/C was calculated to be about 27 times higher than that on Pt/C catalysts at 0.9 V. Furthermore, the Pd6CoCu@Pt/C nanoparticles exhibit superior stability with almost no decay for the ORR polarization curves during 10,000 potential cycles and the core-shell structure remains with only a slight increase in the thickness of the Pt overlayer. Our findings provide a methodology for synthesizing highly efficient catalytic materials for the cathodic application in fuel cells.

  13. Hierarchical hybrid of Ni3N/N-doped reduced graphene oxide nanocomposite as a noble metal free catalyst for oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Zhao, Qi; Li, Yingjun; Li, Yetong; Huang, Keke; Wang, Qin; Zhang, Jun

    2017-04-01

    Novel nickel nitride (Ni3N) nanoparticles supported on nitrogen-doped reduced graphene oxide nanosheets (N-RGOs) are synthesized via a facile strategy including hydrothermal and subsequent calcination methods, in which the reduced graphene oxide nanosheets (RGOs) are simultaneously doped with nitrogen species. By varying the content of the RGOs, a series of Ni3N/N-RGO nanocomposites are obtained. The Ni3N/N-RGO-30% hybrid nanocomposite exhibits superior catalytic activity towards oxygen reduction reaction (ORR) under alkaline condition (0.1 M KOH). Furthermore, this hybrid catalyst also demonstrates high tolerance to methanol poisoning. The RGO containing rich N confers the nanocomposite with large specific surface area and high electronic conduction ability, which can enhance the catalytic efficiency of Ni3N nanoparticles. The enhanced catalytic activity can be attributed to the synergistic effect between Ni3N and nitrogen doped reduced graphene oxide. In addition, the sufficient contact between Ni3N nanoparticles and the N-RGO nanosheets simultaneously promotes good nanoparticle dispersion and provides a consecutive activity sites to accelerate electron transport continuously, which further enhance the ORR performance. The Ni3N/N-RGO may be further an ideal candidate as efficient and inexpensive noble metal-free ORR electrocatalyst in fuel cells.

  14. Intrinsic kinetic equation for oxygen reduction reaction in acidic media: the double Tafel slope and fuel cell applications.

    PubMed

    Wang, Jia X; Uribe, Francisco A; Springer, Thomas E; Zhang, Junliang; Adzic, Radoslav R

    2008-01-01

    According to Sergio Trasatti, "A true theory of electrocatalysis will not be available until activity can be calculated a priori from some known properties of the materials." Toward this goal, we developed intrinsic kinetic equations for the hydrogen oxidation reaction (HOR) and the oxygen reduction reaction (ORR) using as the kinetic parameters the free energies of adsorption and activation for elementary reactions. Rigorous derivation retained the intrinsic connection between the intermediates' adsorption isotherms and the kinetic equations, affording us an integrated approach for establishing the reaction mechanisms based upon various experimental and theoretical results. Using experimentally deduced free energy diagrams and activity-and-barriers plot for the ORR on Pt(111), we explained why the Tafel slope in the large overpotential region is double that in the small overpotential region. For carbon-supported Pt nanoparticles (Pt/C), the polarization curves measured with thin-film rotating disk electrodes also exhibit the double Tafel slope, albeit Pt(111) is several times more active than the Pt nanoparticles when the current is normalized by real surface area. An analytic method was presented for the polarization curves measured with H2 in proton exchange membrane fuel cells (PEMFCs). The fit to a typical iR-free polarization curve at 80 degrees C revealed that the change of the Tafel slope occurs at about 0.77 V that is the reversible potential for the transition between adsorbed O and OH on Pt/C. This is significant because it predicts that the Butler-Volmer equation can only fit the data above this potential, regardless the current density. We also predicted a decrease of the Tafel slope from 70 to 65 mV dec(-1) at 80 degrees C with increasing oxygen partial pressure, which is consistent with the observation reported in literature.

  15. Pt skin on Pd-Co-Zn/C ternary nanoparticles with enhanced Pt efficiency toward ORR

    NASA Astrophysics Data System (ADS)

    Xiao, Weiping; Zhu, Jing; Han, Lili; Liu, Sufen; Wang, Jie; Wu, Zexing; Lei, Wen; Xuan, Cuijuan; Xin, Huolin L.; Wang, Deli

    2016-08-01

    Exploring highly active, stable and relatively low-cost nanomaterials for the oxygen reduction reaction (ORR) is of vital importance for the commercialization of proton exchange membrane fuel cells (PEMFCs). Herein, a highly active, durable, carbon supported, and monolayer Pt coated Pd-Co-Zn nanoparticle is synthesized via a simple impregnation-reduction method, followed by spontaneous displacement of Pt. By tuning the atomic ratios, we obtain the composition-activity volcano curve for the Pd-Co-Zn nanoparticles and determined that Pd : Co : Zn = 8 : 1 : 1 is the optimal composition. Compared with pure Pd/C, the Pd8CoZn/C nanoparticles show a substantial enhancement in both the catalytic activity and the durability toward the ORR. Moreover, the durability and activity are further enhanced by forming a Pt skin on Pd8CoZn/C nanocatalysts. Interestingly, after 10 000 potential cycles in N2-saturated 0.1 M HClO4 solution, Pd8CoZn@Pt/C shows improved mass activity (2.62 A mg-1Pt) and specific activity (4.76 A m-2total), which are about 1.4 and 4.4 times higher than the initial values, and 37.4 and 5.5 times higher than those of Pt/C catalysts, respectively. After accelerated stability testing in O2-saturated 0.1 M HClO4 solution for 30 000 potential cycles, the half-wave potential negatively shifts about 6 mV. The results show that the Pt skin plays an important role in enhancing the activity as well as preventing degradation.Exploring highly active, stable and relatively low-cost nanomaterials for the oxygen reduction reaction (ORR) is of vital importance for the commercialization of proton exchange membrane fuel cells (PEMFCs). Herein, a highly active, durable, carbon supported, and monolayer Pt coated Pd-Co-Zn nanoparticle is synthesized via a simple impregnation-reduction method, followed by spontaneous displacement of Pt. By tuning the atomic ratios, we obtain the composition-activity volcano curve for the Pd-Co-Zn nanoparticles and determined that Pd : Co : Zn = 8

  16. Synthesis propanol by esterification and reduction reaction

    NASA Astrophysics Data System (ADS)

    Salmahaminati; Jumina

    2017-01-01

    Synthesis of propanol from propanoic acid had been done. Propanol was synthesized via two steps. They are; esterification of propanoic acid and methanol in the presence of the sulfuric acid catalyst with the mole ratio of 4:3 to produce methyl propanoate, and reduction of methyl propanoate with sodium using ethylene glycol as the solvent to yield propanol. Structural characterizations of methyl propanoate and propanol were done using IR, 1H-NMR, and GC spectrometers. The results show that esterification of propanoic acid with methanol produced methyl propanoate in 75% yield. Reduction of methyl propanoate using ethylene glycol as a solvent produced propanol in yield of 77%.

  17. Pt skin on Pd–Co–Zn/C ternary nanoparticles with enhanced Pt efficiency toward ORR

    DOE PAGES

    Xiao, Weiping; Zhu, Jing; Han, Lili; ...

    2016-07-15

    Exploring highly active, stable and relatively low-cost nanomaterials for the oxygen reduction reaction (ORR) is of vital importance for the commercialization of proton exchange membrane fuel cells (PEMFCs). A highly active, durable, carbon supported, and monolayer Pt coated Pd–Co–Zn nanoparticle is synthesized via a simple impregnation–reduction method, followed by spontaneous displacement of Pt. By tuning the atomic ratios, we obtain the composition–activity volcano curve for the Pd–Co–Zn nanoparticles and determined that Pd : Co : Zn = 8 : 1 : 1 is the optimal composition. Compared with pure Pd/C, the Pd8CoZn/C nanoparticles show a substantial enhancement in both themore » catalytic activity and the durability toward the ORR. Moreover, the durability and activity are further enhanced by forming a Pt skin on Pd8CoZn/C nanocatalysts. Interestingly, after 10 000 potential cycles in N2-saturated 0.1 M HClO4 solution, Pd8CoZn@Pt/C shows improved mass activity (2.62 A mg-1Pt) and specific activity (4.76 A m-2total), which are about 1.4 and 4.4 times higher than the initial values, and 37.4 and 5.5 times higher than those of Pt/C catalysts, respectively. After accelerated stability testing in O2-saturated 0.1 M HClO4 solution for 30 000 potential cycles, the half-wave potential negatively shifts about 6 mV. Our results show that the Pt skin plays an important role in enhancing the activity as well as preventing degradation.« less

  18. Pt skin on Pd-Co-Zn/C ternary nanoparticles with enhanced Pt efficiency toward ORR.

    PubMed

    Xiao, Weiping; Zhu, Jing; Han, Lili; Liu, Sufen; Wang, Jie; Wu, Zexing; Lei, Wen; Xuan, Cuijuan; Xin, Huolin L; Wang, Deli

    2016-08-21

    Exploring highly active, stable and relatively low-cost nanomaterials for the oxygen reduction reaction (ORR) is of vital importance for the commercialization of proton exchange membrane fuel cells (PEMFCs). Herein, a highly active, durable, carbon supported, and monolayer Pt coated Pd-Co-Zn nanoparticle is synthesized via a simple impregnation-reduction method, followed by spontaneous displacement of Pt. By tuning the atomic ratios, we obtain the composition-activity volcano curve for the Pd-Co-Zn nanoparticles and determined that Pd : Co : Zn = 8 : 1 : 1 is the optimal composition. Compared with pure Pd/C, the Pd8CoZn/C nanoparticles show a substantial enhancement in both the catalytic activity and the durability toward the ORR. Moreover, the durability and activity are further enhanced by forming a Pt skin on Pd8CoZn/C nanocatalysts. Interestingly, after 10 000 potential cycles in N2-saturated 0.1 M HClO4 solution, Pd8CoZn@Pt/C shows improved mass activity (2.62 A mg(-1)Pt) and specific activity (4.76 A m(-2)total), which are about 1.4 and 4.4 times higher than the initial values, and 37.4 and 5.5 times higher than those of Pt/C catalysts, respectively. After accelerated stability testing in O2-saturated 0.1 M HClO4 solution for 30 000 potential cycles, the half-wave potential negatively shifts about 6 mV. The results show that the Pt skin plays an important role in enhancing the activity as well as preventing degradation.

  19. Pt skin on Pd–Co–Zn/C ternary nanoparticles with enhanced Pt efficiency toward ORR

    SciTech Connect

    Xiao, Weiping; Zhu, Jing; Han, Lili; Liu, Sufen; Wang, Jie; Wu, Zexing; Lei, Wen; Xuan, Cuijuan; Xin, Huolin L.; Wang, Deli

    2016-07-15

    Exploring highly active, stable and relatively low-cost nanomaterials for the oxygen reduction reaction (ORR) is of vital importance for the commercialization of proton exchange membrane fuel cells (PEMFCs). A highly active, durable, carbon supported, and monolayer Pt coated Pd–Co–Zn nanoparticle is synthesized via a simple impregnation–reduction method, followed by spontaneous displacement of Pt. By tuning the atomic ratios, we obtain the composition–activity volcano curve for the Pd–Co–Zn nanoparticles and determined that Pd : Co : Zn = 8 : 1 : 1 is the optimal composition. Compared with pure Pd/C, the Pd8CoZn/C nanoparticles show a substantial enhancement in both the catalytic activity and the durability toward the ORR. Moreover, the durability and activity are further enhanced by forming a Pt skin on Pd8CoZn/C nanocatalysts. Interestingly, after 10 000 potential cycles in N2-saturated 0.1 M HClO4 solution, Pd8CoZn@Pt/C shows improved mass activity (2.62 A mg-1Pt) and specific activity (4.76 A m-2total), which are about 1.4 and 4.4 times higher than the initial values, and 37.4 and 5.5 times higher than those of Pt/C catalysts, respectively. After accelerated stability testing in O2-saturated 0.1 M HClO4 solution for 30 000 potential cycles, the half-wave potential negatively shifts about 6 mV. Our results show that the Pt skin plays an important role in enhancing the activity as well as preventing degradation.

  20. Pt skin on Pd–Co–Zn/C ternary nanoparticles with enhanced Pt efficiency toward ORR

    SciTech Connect

    Xiao, Weiping; Zhu, Jing; Han, Lili; Liu, Sufen; Wang, Jie; Wu, Zexing; Lei, Wen; Xuan, Cuijuan; Xin, Huolin L.; Wang, Deli

    2016-07-15

    Exploring highly active, stable and relatively low-cost nanomaterials for the oxygen reduction reaction (ORR) is of vital importance for the commercialization of proton exchange membrane fuel cells (PEMFCs). A highly active, durable, carbon supported, and monolayer Pt coated Pd–Co–Zn nanoparticle is synthesized via a simple impregnation–reduction method, followed by spontaneous displacement of Pt. By tuning the atomic ratios, we obtain the composition–activity volcano curve for the Pd–Co–Zn nanoparticles and determined that Pd : Co : Zn = 8 : 1 : 1 is the optimal composition. Compared with pure Pd/C, the Pd8CoZn/C nanoparticles show a substantial enhancement in both the catalytic activity and the durability toward the ORR. Moreover, the durability and activity are further enhanced by forming a Pt skin on Pd8CoZn/C nanocatalysts. Interestingly, after 10 000 potential cycles in N2-saturated 0.1 M HClO4 solution, Pd8CoZn@Pt/C shows improved mass activity (2.62 A mg-1Pt) and specific activity (4.76 A m-2total), which are about 1.4 and 4.4 times higher than the initial values, and 37.4 and 5.5 times higher than those of Pt/C catalysts, respectively. After accelerated stability testing in O2-saturated 0.1 M HClO4 solution for 30 000 potential cycles, the half-wave potential negatively shifts about 6 mV. Our results show that the Pt skin plays an important role in enhancing the activity as well as preventing degradation.

  1. Engineering hybrid between nickel oxide and nickel cobaltate to achieve exceptionally high activity for oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Cui, Zhentao; Wang, Shuguang; Zhang, Yihe; Cao, Minhua

    2014-12-01

    The porous NiO/NiCo2O4 nanotubes are prepared via a coaxial electrospinning technique followed by an annealing treatment. The resultant NiO/NiCo2O4 hybrid is developed as a highly efficient electrocatalyst, which exhibits significantly enhanced electrocatalytic activity, long-term operation stability, and tolerance to crossover effect compared to NiO nanofibers, NiCo2O4 nanofibers and commercial Pt(20%)/C for oxygen reduction reactions (ORR) in alkaline environment. The excellent electrocatalytic performance may be attributed to the unique microstructures of the porous NiO/NiCo2O4 nanotubes, such as heterogeneous hybrid structure, open porous tubular structure, and the well dispersity of the two components. Moreover, the promising and straightforward coaxial electrospinning proves itself to be an efficient pathway for the preparation of nanomaterials with tubular architectures and it can be used for large-scale production of catalysts in fuel cells.

  2. Oxidation and Reduction Reactions in Organic Chemistry

    ERIC Educational Resources Information Center

    Shibley, Ivan A., Jr.; Amaral, Katie E.; Aurentz, David J.; McCaully, Ronald J.

    2010-01-01

    A variety of approaches to the concept of oxidation and reduction appear in organic textbooks. The method proposed here is different than most published approaches. The oxidation state is calculated by totaling the number of heterogeneous atoms, [pi]-bonds, and rings. A comparison of the oxidation states of reactant and product determine what type…

  3. Oxidation and Reduction Reactions in Organic Chemistry

    ERIC Educational Resources Information Center

    Shibley, Ivan A., Jr.; Amaral, Katie E.; Aurentz, David J.; McCaully, Ronald J.

    2010-01-01

    A variety of approaches to the concept of oxidation and reduction appear in organic textbooks. The method proposed here is different than most published approaches. The oxidation state is calculated by totaling the number of heterogeneous atoms, [pi]-bonds, and rings. A comparison of the oxidation states of reactant and product determine what type…

  4. Noble-metal-free Fe-N/C catalyst for highly efficient oxygen reduction reaction under both alkaline and acidic conditions.

    PubMed

    Lin, Ling; Zhu, Qing; Xu, An-Wu

    2014-08-06

    In this work, we report the synthesis and assessment of a new non-precious-metal oxygen reduction reaction (ORR) catalyst from pyrolysis of an iron-coordinated complex which manifests superior activity in both alkaline and acidic media. 11,11'-bis(dipyrido[3,2-a:2',3'-c]phenazinyl) (bidppz) was selected as a ligand for the formation of a nitrogen-rich iron-coordinated coordination polymer (Fe-bidppz) which forms a self-supporting catalyst containing high densities of nitrogen and iron doping by pyrolysis. The catalyst pyrolyzed at 800 °C (Fe-N/C-800) shows the highest ORR activity with onset and half-wave potentials of 923 and 809 mV in 0.1 M KOH, respectively, which are comparable to those of Pt/C (half-wave potential 818 mV vs RHE) at the same catalyst loading. Besides, the Fe-N/C-800 catalyst has an excellent ORR activity with onset and half-wave potentials only 38 and 59 mV less than those of the Pt/C catalyst in 0.1 M HClO4. The optimal Fe-N/C-800 catalyst displays much greater durability and tolerance of methanol than Pt/C. We propose that the Fe-N/C-800 catalyst has a considerably high density of surface active sites because Fe-N/C-800 possesses excellent ORR activity while its specific surface area is not so high. Electrochemical measurements show that the Fe-N/C-800 catalyst in KOH and HClO4 follows the effective four-electron-transfer pathway.

  5. Self-assembled dopamine nanolayers wrapped carbon nanotubes as carbon-carbon bi-functional nanocatalyst for highly efficient oxygen reduction reaction and antiviral drug monitoring

    NASA Astrophysics Data System (ADS)

    Khalafallah, Diab; Akhtar, Naeem; Alothman, Othman Y.; Fouad, H.; Abdelrazek khalil, Khalil

    2017-09-01

    Oxygen reduction reaction (ORR) catalysts are the heart of eco-friendly energy resources particularly low temperature fuel cells. Although valuable efforts have been devoted to synthesize high performance catalysts for ORR, considerable challenges are extremely desirable in the development of energy technologies. Herein, we report a simple self-polymerization method to build a thin film of dopamine along the tubular nanostructures of multi-walled carbon nanotubes (CNT) in a weak alkaline solution. The dopamine@CNT hybrid (denoted as DA@CNT) reveals an enhanced electrocatalytic activity towards ORR with highly positive onset potential and cathodic current as a result of their outstanding features of longitudinal mesoporous structure, high surface area, and ornamentation of DA layers with nitrogen moieties, which enable fast electron transport and fully exposed electroactive sites. Impressively, the as-obtained hybrid afford remarkable electrochemical durability for prolonged test time of 60,000 s compared to benchmark Pt/C (20 wt%) catalyst. Furthermore, the developed DA@CNT electrode was successfully applied to access the quality of antiviral drug named Valacyclovir (VCR). The DA@CNT electrode shows enhanced sensing performance in terms of large linear range (3-75 nM), low limit of detection (2.55 nM) than CNT based electrode, indicating the effectiveness of the DA coating. Interestingly, the synergetic effect of nanostructured DA and CNT can significantly boost the electronic configuration and exposure level of active species for ORR and biomolecule recognition. Therefore, the existing carbon-based porous electrocatalyst may find numerous translational applications as attractive alternative to noble metals in polymer electrolyte membrane fuel cells and quality control assessment of pharmaceutical and therapeutic drugs.

  6. Well-Combined Magnetically Separable Hybrid Cobalt Ferrite/Nitrogen-Doped Graphene as Efficient Catalyst with Superior Performance for Oxygen Reduction Reaction.

    PubMed

    Lu, Lei; Hao, Qingli; Lei, Wu; Xia, Xifeng; Liu, Peng; Sun, Dongping; Wang, Xin; Yang, Xujie

    2015-11-18

    Catalysts with low-cost, high activity and stability toward oxygen reduction reaction (ORR) are extremely desirable, but its development still remains a great challenge. Here, a novel magnetically separable hybrid of multimetal oxide, cobalt ferrite (CoFe2O4), anchored on nitrogen-doped reduced graphene oxide (CoFe2O4/NG) is prepared via a facile solvothermal method followed by calcination at 500 °C. The structure of CoFe2O4/NG and the interaction of both components are analyzed by several techniques. The possible formation of Co/Fe-N interaction in the CoFe2O4/NG catalyst is found. As a result, the well-combination of CoFe2O4 nanoparticles with NG and its improved crystallinity lead to a synergistic and efficient catalyst with high performance to ORR through a four-electron-transfer process in alkaline medium. The CoFe2O4/NG exhibits particularly comparable catalytic activity as commercial Pt/C catalyst, and superior stability against methanol oxidation and CO poisoning. Meanwhile, it has been proved that both nitrogen doping and the spinel structure of CoFe2O4 can have a significant contribution to the catalytic activity by contrast experiments. Multimetal oxide hybrid demonstrates better catalysis to ORR than a single metal oxide hybrid. All results make the low-cost and magnetically separable CoFe2O4/NG a promising alternative for costly platinum-based ORR catalyst in fuel cells and metal-air batteries. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Asymmetric Volcano Trend in Oxygen Reduction Activity of Pt and Non-Pt Catalysts: In Situ Identification of the Site-Blocking Effect.

    PubMed

    Li, Jingkun; Alsudairi, Amell; Ma, Zi-Feng; Mukerjee, Sanjeev; Jia, Qingying

    2017-02-01

    Proper understanding of the major limitations of current catalysts for oxygen reduction reaction (ORR) is essential for further advancement. Herein by studying representative Pt and non-Pt ORR catalysts with a wide range of redox potential (Eredox) via combined electrochemical, theoretical, and in situ spectroscopic methods, we demonstrate that the role of the site-blocking effect in limiting the ORR varies drastically depending on the Eredox of active sites; and the intrinsic activity of active sites with low Eredox have been markedly underestimated owing to the overlook of this effect. Accordingly, we establish a general asymmetric volcano trend in the ORR activity: the ORR of the catalysts on the overly high Eredox side of the volcano is limited by the intrinsic activity; whereas the ORR of the catalysts on the low Eredox side is limited by either the site-blocking effect and/or intrinsic activity depending on the Eredox.

  8. Meso-structured platinum thin films: active and stable electrocatalysts for the oxygen reduction reaction.

    PubMed

    Kibsgaard, Jakob; Gorlin, Yelena; Chen, Zhebo; Jaramillo, Thomas F

    2012-05-09

    Improving both the activity and the stability of the cathode catalyst in platinum-based polymer electrolyte fuel cells is a key technical challenge. Here, we synthesize a high surface area meso-structured Pt thin film that exhibits higher specific activity for the oxygen reduction reaction (ORR) than commercial carbon-supported Pt nanoparticles (Pt/C). An accelerated stability test demonstrates that the meso-structured Pt thin film also displays significantly enhanced stability as compared to the commercial Pt/C catalyst. Our study reveals the origin of the high turnover frequency (TOF), and excellent durability is attributed to the meso-structure, which yields a morphology with fewer undercoordinated Pt sites than Pt/C nanoparticles, a key difference with substantial impact to the surface chemistry. The improved catalyst activity and stability could enable the development of a high-performance gas diffusion electrode that is resistant to corrosion even under the harsh conditions of start-up, shut-down, and/or hydrogen starvation.

  9. Pyrolyzed binuclear-cobalt-phthalocyanine as electrocatalyst for oxygen reduction reaction in microbial fuel cells.

    PubMed

    Li, Baitao; Wang, Mian; Zhou, Xiuxiu; Wang, Xiujun; Liu, Bingchuan; Li, Baikun

    2015-10-01

    A novel platinum (Pt)-free cathodic materials binuclear-cobalt-phthalocyanine (Bi-CoPc) pyrolyzed at different temperatures (300-1000 °C) were examined as the oxygen reduction reaction (ORR) catalysts, and compared with unpyrolyzed Bi-CoPc/C and Pt cathode in single chamber microbial fuel cells (SCMFCs). The results showed that the pyrolysis process increased the nitrogen abundance on Bi-CoPc and changed the nitrogen types. The Bi-CoPc pyrolyzed at 800 °C contained a significant amount of pyrrolic-N, and exhibited a high electrochemical catalytic activity. The power density and current density increased with temperature: Bi-CoPc/C-800 > Bi-CoPc/C-1000 > Bi-CoPc/C-600 > Bi-CoPc/C-300 > Bi-CoPc/C. The SCMFC with Bi-CoPc/C-800 cathode had a maximum power density of 604 mW m(-2). The low cost Bi-CoPc compounds developed in this study showed a potential in air-breathing MFC systems, with the proper pyrolysis temperature being chosen. Copyright © 2015 Elsevier Ltd. All rights reserved.

  10. Tailoring of Pd-Pt bimetallic clusters with high stability for oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Cheng, Daojian; Wang, Wenchuan

    2012-03-01

    The composition-dependent equilibrium structure and thermal stability of Pd-Pt clusters with the size of 55 atoms, and CO, O, OH, and O2 adsorption on these clusters have been studied using molecular simulation based on the Gupta empirical potential and density functional theory (DFT) calculations. It is found that Pd43Pt12 with a three-shell onionlike structure (TS-cluster) exhibits the highest relative stability in both DFT and Gupta levels and also the highest melting point at the Gupta level among these Pd-Pt clusters. In addition, the Pd43Pt12 TS-cluster possesses the weakest CO, O, OH, and O2 adsorption strength, compared to the Pt55, Pd55, and Pd13Pt42 clusters, indicating good catalytic activities toward the oxygen reduction reaction (ORR) among these Pd-Pt clusters considered. We expect that this kind of DFT-guided strategy by controlling the composition could provide a simple way for possibly searching new electrocatalysts.

  11. Graphene-Based Non-Noble-Metal Catalysts for Oxygen Reduction Reaction in Acid

    SciTech Connect

    H Byon; J Suntivich; Y Shao-Horn

    2011-12-31

    Non-noble-metal catalysts based on Fe-N-C moieties have shown promising oxygen reduction reaction (ORR) activity in proton exchange membrane fuel cells (PEMFCs). In this study, we report a facile method to prepare a Fe-N-C catalyst based on modified graphene (Fe-N-rGO) from heat treatment of a mixture of Fe salt, graphitic carbon nitride (g-C{sub 3}N{sub 4}), and chemically reduced graphene (rGO). The Fe-N-rGO catalyst was found to have pyridinic N-dominant heterocyclic N (40% atomic concentration among all N components) on the surface and have an average Fe coordination of {approx}3 N (Fe-N{sub 3,average}) in bulk. Rotating disk electrode measurements revealed that Fe-N-rGO had high mass activity in acid and exhibited high stability at 0.5 V at 80 C in acid over 70 h, which was correlated to low H{sub 2}O{sub 2} production shown from rotating ring disk electrode measurements.

  12. Tailoring of Pd-Pt bimetallic clusters with high stability for oxygen reduction reaction.

    PubMed

    Cheng, Daojian; Wang, Wenchuan

    2012-04-07

    The composition-dependent equilibrium structure and thermal stability of Pd-Pt clusters with the size of 55 atoms, and CO, O, OH, and O(2) adsorption on these clusters have been studied using molecular simulation based on the Gupta empirical potential and density functional theory (DFT) calculations. It is found that Pd(43)Pt(12) with a three-shell onionlike structure (TS-cluster) exhibits the highest relative stability in both DFT and Gupta levels and also the highest melting point at the Gupta level among these Pd-Pt clusters. In addition, the Pd(43)Pt(12) TS-cluster possesses the weakest CO, O, OH, and O(2) adsorption strength, compared to the Pt(55), Pd(55), and Pd(13)Pt(42) clusters, indicating good catalytic activities toward the oxygen reduction reaction (ORR) among these Pd-Pt clusters considered. We expect that this kind of DFT-guided strategy by controlling the composition could provide a simple way for possibly searching new electrocatalysts. This journal is © The Royal Society of Chemistry 2012

  13. Nitrogen-doped carbon dots originating from unripe peach for fluorescent bioimaging and electrocatalytic oxygen reduction reaction.

    PubMed

    Atchudan, Raji; Edison, Thomas Nesakumar Jebakumar Immanuel; Lee, Yong Rok

    2016-11-15

    This paper reports the robust hydrothermal synthesis of nitrogen doped carbon dots (N-CDs) using the unripe fruit of Prunus persica (peach) as the carbon precursor and aqueous ammonia as the nitrogen source. The optical properties of synthesized N-CDs were characterized by ultraviolet visible (UV-Vis) and fluorescence spectroscopy techniques. The synthesized N-CDs were emitted blue light when excitated with a portable UV lamp. The materials with the optical properties were characterized further by high resolution transmission electron microscope (HRTEM), X-ray diffraction (XRD), Raman, Fourier transform infrared (FT-IR) and X-ray photoelectron spectroscopy (XPS). The mean size of the N-CDs was approximately 8nm, as calculated from the HRTEM image. The d-spacing of N-CDs, calculated using Bragg law, was approximately 0.21nm, which was consistent with the interlayer distance calculated from the HRTEM image. FT-IR spectroscopy and XPS revealed the presence of the phytoconstituents functionalities of peach fruit over the N-CDs surface and a high level of nitrogen doping on carbon dots (CDs) was confirmed by XPS studies. These results suggest that the unripe fruit extract of peach is an ideal candidate for the preparation of N-CDs. The resulting N-CDs showed excellent optical properties in water. The synthesized N-CDs exhibited a high fluorescence quantum yield and low cytotoxicity, and can be used as fluorescence imaging probes. In addition, the N-CDs were catalytically activite towards the oxygen reduction reaction (ORR). The N-CDs exhibited good catalytic activity in an alkaline medium (0.1M KOH) with a remarkable ORR of approximately 0.72V vs reversible hydrogen electrode (RHE), and O2 reduction follows mainly a 2 electron pathway by being reduced to hydrogen peroxide. The 2-electron reduction pathway is used in industry for H2O2 production.

  14. Synthesis, characterization and electrochemical studies of nanostructured CaWO{sub 4} as platinum support for oxygen reduction reaction

    SciTech Connect

    Farsi, Hossein; Barzgari, Zahra

    2014-11-15

    Highlights: • Nanostructured CaWO{sub 4} was fabricated by co-precipitation method. • Platinum was electrodeposited onto the surface prepared nanostructured CaWO{sub 4}. • Pt/CaWO{sub 4}-graphite demonstrate good oxygen reduction reaction activity. - Abstract: In the present work, we employed nanostructured calcium tungstate as a supporting material for platinum, a well-known electrocatalyst for oxygen reduction. The co-precipitation method has been utilized to synthesize nanostructured calcium tungstate from aqueous solution. The structure and morphology of the obtained CaWO{sub 4} were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Preparation of the Pt/CaWO{sub 4}-graphite catalyst was carried out by electrodeposition of Pt onto the surface of CaWO{sub 4}/graphite electrode. The physical properties of the catalyst were determined by scanning electron microscopy analysis and energy dispersive X-ray (SEM/EDX). The electrochemical activity of the Pt/CaWO{sub 4}-graphite for the oxygen reduction reaction (ORR) was investigated in acid solution by cyclic voltammetry measurements, linear sweep voltammetry, and electrochemical impedance spectroscopy. The results revealed that the Pt/CaWO{sub 4}-graphite has higher electrocatalytic activity for oxygen reduction in comparison with Pt/graphite catalyst.

  15. Atomic Ordering Enhanced Electrocatalytic Activity of Nanoalloys for Oxygen Reduction Reaction

    SciTech Connect

    Loukrakpam, Rameshwori; Shan, Shiyao; Petkov, Valeri; Yang, Lefu; Luo, Jin; Zhong, Chuan-Jian

    2013-10-01

    For oxygen reduction reaction (ORR) over alloy electrocatalysts, the understanding of how the atomic arrangement of the metal species in the nanocatalysts is responsible for the catalytic enhancement is challenging for achieving better design and tailoring of nanoalloy catalysts. This paper reports results of an investigation of the atomic structures and the electrocatalytic activities of ternary and binary nanoalloys, aiming at revealing a fundamental insight into the unique atomic-scale structure-electrocatalytic activity relationship. PtIrCo catalyst and its binary counterparts (PtCo and PtIr) are chosen as a model system for this study. The effect of thermochemical treatment temperature on the atomic-scale structure of the catalysts was examined as a useful probe to the structure-activity correlation. The structural characterization of the binary and ternary nanoalloy catalysts was performed by combining surface sensitive techniques such as XPS and 3D atomic ordering sensitive techniques such as high-energy X-ray diffraction (HE-XRD) coupled to atomic pair distribution function (PDF) analysis (HE-XRD/PDFs) and computer simulations. The results show that the thermal treatment temperature tunes the nanoalloy’s atomic and chemical ordering in a different way depending on the chemical composition, leading to differences in the nanoalloy’s mass and specific activities. A unique structural tunability of the atomic ordering in a platinum-iridium-cobalt nanoalloy has been revealed for enhancing greatly the electrocatalytic activity toward oxygen reduction reaction, which has significant implication for rational design and nanoengineering of advanced catalysts for electrochemical energy conversion and storage.

  16. The effect of varying solvents for MoS2 treatment on its catalytic efficiencies for HER and ORR.

    PubMed

    Chua, Xing Juan; Pumera, Martin

    2017-03-01

    MoS2 has been investigated intensively in the field of catalysis for the hydrogen evolution reaction (HER) in particular. Much effort has been made by various research teams worldwide to look into the specific catalyst design such as nano-structuring, defect engineering or hybrid structures. But what evades us is the fundamental preparation method for the dispersion of powdered MoS2. Individual research teams with their best practices might be subjective and not validated by extensive experimental results. In this report, we find that the overpotential for the catalysis of HER varies from 0.57 to 0.72 V (freshly prepared) when different dispersion media are used, such as acetonitrile, N,N-dimethylformamide, ethanol, methanol and water. In terms of oxygen reduction reaction (ORR) catalysis, less significant differences were found. With both HER and ORR pertinent to the fuel cell industry, this report would serve as an insight to readers when comparing the results of MoS2 catalysis across the literature from different research groups when different solvents were used as the dispersion medium.

  17. Whole cell biotransformation for reductive amination reactions

    PubMed Central

    Klatte, Stephanie; Lorenz, Elisabeth; Wendisch, Volker F

    2014-01-01

    Whole cell biotransformation systems with enzyme cascading increasingly find application in biocatalysis to complement or replace established chemical synthetic routes for production of, e.g., fine chemicals. Recently, we established an Escherichia coli whole cell biotransformation system for reductive amination by coupling a transaminase and an amino acid dehydrogenase with glucose catabolism for cofactor recycling. Transformation of 2-keto-3-methylvalerate to l-isoleucine by E. coli cells was improved by genetic engineering of glucose metabolism for improved cofactor regeneration. Here, we compare this system with different strategies for cofactor regeneration such as cascading with alcohol dehydrogenases, with alternative production hosts such as Pseudomonas species or Corynebacterium glutamicum, and with improving whole cell biotransformation systems by metabolic engineering of NADPH regeneration. PMID:24406456

  18. Whole cell biotransformation for reductive amination reactions.

    PubMed

    Klatte, Stephanie; Lorenz, Elisabeth; Wendisch, Volker F

    2014-01-01

    Whole cell biotransformation systems with enzyme cascading increasingly find application in biocatalysis to complement or replace established chemical synthetic routes for production of, e.g., fine chemicals. Recently, we established an Escherichia coli whole cell biotransformation system for reductive amination by coupling a transaminase and an amino acid dehydrogenase with glucose catabolism for cofactor recycling. Transformation of 2-keto-3-methylvalerate to l-isoleucine by E. coli cells was improved by genetic engineering of glucose metabolism for improved cofactor regeneration. Here, we compare this system with different strategies for cofactor regeneration such as cascading with alcohol dehydrogenases, with alternative production hosts such as Pseudomonas species or Corynebacterium glutamicum, and with improving whole cell biotransformation systems by metabolic engineering of NADPH regeneration.

  19. 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

  20. Cumulative effect of transition metals on nitrogen and fluorine co-doped graphite nanofibers: an efficient and highly durable non-precious metal catalyst for the oxygen reduction reaction.

    PubMed

    Peera, S Gouse; Arunchander, A; Sahu, A K

    2016-08-14

    Nitrogen and fluorine co-doped graphite nanofibers (N/F-GNF) and their cumulative effect with Fe and Co have been developed as an alternative non-precious metal catalyst for efficient oxygen reduction reaction (ORR) in acidic media. The synergistic effect between the doped hetero atoms and the co-ordinated Fe and Co towards ORR activity and durability of the catalyst is deeply investigated. A high ORR onset potential comparable with commercial Pt/C catalyst is observed with the Fe-Co/NF-GNF catalyst, which indicates that this catalyst is a potential alternative to Pt/C. A fivefold increase in mass activity is achieved by the Fe-Co/NF-GNF catalyst compared to the simple N/F-GNF catalyst, which endorses the significant role of transition metal atoms in enhancing ORR activity. The advanced Fe-Co/NF-GNF catalyst also exhibits complete tolerance to CH3OH and CO. The Fe-Co/NF-GNF catalyst also exhibits excellent durability towards the ORR with only a 10 mV negative shift in its half wave potential after a 10 000 repeated potential cycling test, whereas in the case of a commercial Pt/C catalyst there was an ∼110 mV negative shift under similar environmental conditions. More stringent corrosive test cycles were also performed by maintaining the cell as high as 1.4 V with a later decrease to 0.6 V vs. RHE for 300 cycles, which showed the excellent durability of the Fe-Co/NF-GNF catalyst in comparison with the Pt/C catalyst. XPS analysis of the Fe-Co/NF-GNF catalyst presents the ORR active chemical states of N (pyridinic-N and graphitic-N) and F (semi-ionic-F) and the co-ordinated sites of Fe and Co species with the dopants. The excellent performance and durability of the Fe-Co/NF-GNF catalyst is due to the synergistic effect between the hetero atoms dopants (N and F) and strong co-ordinating bonds of M-N-C, which protect the graphene layers around the metallic species and greatly mitigates the leaching of Co and Fe during the long term cycling test. The high activity

  1. Investigation of oxygen reduction and methanol oxidation reaction activity of PtAu nano-alloy on surface modified porous hybrid nanocarbon supports

    NASA Astrophysics Data System (ADS)

    Parambath Vinayan, Bhaghavathi; Nagar, Rupali; Ramaprabhu, Sundara

    2016-09-01

    We investigate the electrocatalytic activity of PtAu alloy nanoparticles supported on various chemically modified carbon morphologies towards oxygen reduction reaction (ORR) and methanol oxidation reaction (MOR). The surface-modification of graphene nanosheets (f-G), multi-walled carbon nanotubes (f-MWNTs) and (graphene nanosheets-carbon nanotubes) hybrid support (f-G-MWNTs) were carried out by soft functionalization method using a cationic polyelectrolyte poly-(diallyldimethyl ammonium chloride). The Pt and PtAu alloy nanoparticles were dispersed over chemically modified carbon supports by sodium-borohydride assisted modified polyol reduction method. The electrochemical performance of all electrocatalysts were studied by half- and full-cell proton exchange membrane fuel cell (PEMFC) measurements and PtAu/f-G-MWNTs catalyst comparatively yielded the best catalytic performance. PEMFC full cell measurements of PtAu/f-G-MWNTs cathode electrocatalyst yield a maximum power density of 319 mW cm-2 at 60 °C without any back pressure,which is 2.1 times higher than that of cathode electrocatalyst Pt on graphene support. The high ORR and MOR activity of PtAu/f-G-MWNTs electrocatalyst is due to the alloying effect and inherent beneficial properties of porous hybrid nanocarbon support.

  2. Kinetics and mechanism of oxygen reduction in a protic ionic liquid.

    PubMed

    Walsh, Darren A; Ejigu, Andinet; Smith, Joshua; Licence, Peter

    2013-05-28

    The oxygen reduction reaction (ORR) has been studied at Pt surfaces in the protic ionic liquid diethylmethylammonium trifluoromethanesulfonate. Water content measurements suggested that the ORR proceeded in the ionic liquid predominantly via a 4-electron reduction to water. A mechanistic analysis using rotating ring-disk electrode (RRDE) voltammetry confirmed that negligible amounts of hydrogen peroxide were formed during the ORR. A kinetic analysis of the ORR was performed using rotating disk electrode (RDE) voltammetry and the importance of correcting for ohmic (iR) drop prior to performing kinetic measurements in the ionic liquid is demonstrated. A Tafel analysis of the RDE voltammetry data revealed a change in the ORR Tafel slope from 70 mV per decade at low ORR overpotentials to 117 mV per decade at high overpotentials, and the reason for this change is discussed. The change in the Tafel slope for the ORR with increasing overpotential meant that the exchange current density for the ORR varied from 0.007 nA cm(-2) to 10 nA cm(-2), depending on the applied potential. Finally, the implications of these results for the development of protic ionic liquid fuel cells are discussed.

  3. Palladium-platinum core-shell electrocatalysts for oxygen reduction reaction prepared with the assistance of citric acid

    SciTech Connect

    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 microscopy (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.

  4. Palladium-platinum core-shell electrocatalysts for oxygen reduction reaction prepared with the assistance of citric acid

    SciTech Connect

    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 microscopy (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.

  5. Palladium-platinum core-shell electrocatalysts for oxygen reduction reaction prepared with the assistance of citric acid

    DOE PAGES

    Zhang, Lulu; Su, Dong; Zhu, Shangqian; ...

    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

  6. A simple synthesis method of sulfur-free Fe-N-C catalyst witih high ORR activity

    SciTech Connect

    Ding, Zhongfen; Johnston, Christina M; Zelenay, Piotr

    2010-01-01

    To try to deconvolute which factors affect the activity and durability of metal-nitrogen-carbon (M-N-C) type non-precious catalysts for oxygen reduction reaction (ORR), M-N-C catalysts based on ion chloride, polyaniline (PANI) and Ketjen Black carbon support were synthesized using different synthetic conditions. The catalysts were characterized electrochemically and tested as cathodes for Hydrogen fuel cells. PANI is usually chemically oxidative polymerized using ammonium persulfate (APS) as oxidant. To eliminate sulfur in the synthesized catalysts, a simple synthesis method using ion chloride as oxidant for aniline polymerization was developed. Two different aniline polymerization conditions led to very different product morphologies. Synthesized at low initial proton concentration, the final product was composed of dense micrometer sized particles. A decomposable salt was found to be able to prohibit PANI cross linking during the drying and annealing process and thus led to porous product. The porous catalyst has much higher ORR activity than the dense product due to more accessible active sites. Synthesized at high proton concentration, the catalyst appeared to be porous. The decomposable salt treatment did not make too much improvement in the porous structure and electrochemical activity. However, fuel cell testing using air as cathode feeder indicates that the salt treatment improves mass transfer in the cathode layer. Catalyst synthesized using this simple method has performance comparable to our state-of-the art catalyst synthesized in a much more complicated procedure. The factor that sulfur sources are completely eliminated in the synthesis suggests that sulfur is not necessary for the ORR catalysis activity.

  7. Boron doped graphene wrapped silver nanowires as an efficient electrocatalyst for molecular oxygen reduction

    PubMed Central

    Nair, Anju K.; Thazhe veettil, Vineesh; Kalarikkal, Nandakumar; Thomas, Sabu; Kala, M. S.; Sahajwalla, Veena; Joshi, Rakesh K.; Alwarappan, Subbiah

    2016-01-01

    Metal nanowires exhibit unusually high catalytic activity towards oxygen reduction reaction (ORR) due to their inherent electronic structures. However, controllable synthesis of stable nanowires still remains as a daunting challenge. Herein, we report the in situ synthesis of silver nanowires (AgNWs) over boron doped graphene sheets (BG) and demonstrated its efficient electrocatalytic activity towards ORR for the first time. The electrocatalytic ORR efficacy of BG-AgNW is studied using various voltammetric techniques. The BG wrapped AgNWs shows excellent ORR activity, with very high onset potential and current density and it followed four electron transfer mechanism with high methanol tolerance and stability towards ORR. The results are comparable to the commercially available 20% Pt/C in terms of performance. PMID:27941954

  8. Boron doped graphene wrapped silver nanowires as an efficient electrocatalyst for molecular oxygen reduction

    NASA Astrophysics Data System (ADS)

    Nair, Anju K.; Thazhe Veettil, Vineesh; Kalarikkal, Nandakumar; Thomas, Sabu; Kala, M. S.; Sahajwalla, Veena; Joshi, Rakesh K.; Alwarappan, Subbiah

    2016-12-01

    Metal nanowires exhibit unusually high catalytic activity towards oxygen reduction reaction (ORR) due to their inherent electronic structures. However, controllable synthesis of stable nanowires still remains as a daunting challenge. Herein, we report the in situ synthesis of silver nanowires (AgNWs) over boron doped graphene sheets (BG) and demonstrated its efficient electrocatalytic activity towards ORR for the first time. The electrocatalytic ORR efficacy of BG-AgNW is studied using various voltammetric techniques. The BG wrapped AgNWs shows excellent ORR activity, with very high onset potential and current density and it followed four electron transfer mechanism with high methanol tolerance and stability towards ORR. The results are comparable to the commercially available 20% Pt/C in terms of performance.

  9. Molecular catalysis of the oxygen reduction reaction by iron porphyrin catalysts tethered into Nafion layers: An electrochemical study in solution and a membrane-electrode-assembly study in fuel cells

    NASA Astrophysics Data System (ADS)

    He, Qinggang; Mugadza, Tawanda; Kang, Xiongwu; Zhu, Xiaobing; Chen, Shaowei; Kerr, John; Nyokong, Tebello

    2012-10-01

    This study was motivated by the need for improved understanding of the kinetics and transport phenomena in a homogeneous catalyst system for the oxygen reduction reaction (ORR). Direct interaction between the sulfonic groups of Nafion and an Fe(III) meso-tetra(N-methyl-4-pyridyl) porphine chloride (Fe(III)TMPyP) compound was observed using FTIR and in situ UV-Vis spectroelectrochemical characterizations. A positive shift of the half wave potential value (E1/2) for ORR on the iron porphyrin catalyst (Fe(III)TMPyP) was observed upon addition of a specific quantity of Nafion ionomer on a glassy carbon working electrode, indicating not only a faster charge transfer rate but also the role of protonation in the oxygen reduction reaction (ORR) process. A membrane electrode assembly (MEA) was made as a sandwich of a Pt-coated anode, a Nafion® 212 membrane, and a Fe(III)TMPyP + Nafion ionomer-coated cathode. This three-dimensional catalysis system has been demonstrated to be working in a H2/O2 proton exchange membrane (PEM) fuel cell test.

  10. 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.

  11. [Characteristics of sulfate reduction-ammonia oxidation reaction].

    PubMed

    Yuan, Yi; Huang, Yong; Li, Xiang; Zhang, Chun-Lei; Zhang, Li; Pan, Yang; Liu, Fu-Xin

    2013-11-01

    The sulfate reduction-ammonia oxidation reaction with ANAMMOX sludge at autotrophic condition was implemented. It was found that the pH level decreased during the reaction. Elemental sulfur and nitrogen gas were the final products, while NO3(-) -N was the intermediate product during the sulfate reduction-ammonia oxidation reaction. The conversion ratio of NH4(+) -N/SO4(2-) -S decreased with the decrease in n(N)/n(S) (molar ratio) of raw water. n(N)/n(S) of raw water had little effect on the ammonia conversion ratio. Lower n(N)/n(S) could improve the SO4(2-)-S conversion ratio, but with more NH4(+) -N oxidized into NO3(-) -N, resulting in decreased n(TN)/n(TS) removal ratio. This indicates that the sulfate reduction-ammonia oxidation reaction is not an elementary reaction. Ammonia can be oxidized into NO2(-) -N or NO3(-) -N by sulfate. Shortening the reaction time would be conducive to nitrogen losses, because the reaction of NO3(-) -N production is the rate-limiting step.

  12. NiCo2O4 spinel/ordered mesoporous carbons as noble-metal free electrocatalysts for oxygen reduction reaction and the influence of structure of catalyst support on the electrochemical activity of NiCo2O4

    NASA Astrophysics Data System (ADS)

    Bo, Xiangjie; Zhang, Yufan; Li, Mian; Nsabimana, Anaclet; Guo, Liping

    2015-08-01

    Three ordered mesoporous carbons (OMCs) with different structures are used as catalyst supports for growth of NiCo2O4 spinel. The high surface area of OMCs provides more active sites to adsorb metal precursors. The porous structure confines the growth of NiCo2O4 and supplies more efficient transport passage for reactant molecules to access the active sites. Due to the structural characteristics of OMCs and catalytic properties of NiCo2O4, NiCo2O4/OMCs composites are highly active, cheap, and selective noble metal-free electrocatalysts for the oxygen reduction reaction (ORR) in alkaline solution. The electrochemical activity of NiCo2O4 supported on three OMCs with different structures, surface areas, pore sizes, pore volumes, and defective sites is studied. NiCo2O4/OMCs composites may be further used as efficient and inexpensive noble metal-free ORR catalysts in alkaline solution.

  13. Decorating unoxidized-carbon nanotubes with homogeneous Ni-Co spinel nanocrystals show superior performance for oxygen evolution/reduction reactions.

    PubMed

    Yang, Jun; Fujigaya, Tsuyohiko; Nakashima, Naotoshi

    2017-03-30

    We present a new concept for homogeneous spinel nanocrystal-coating on high crystalline pristine-carbon nanotubes (CNTs) for efficient and durable oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). Oxidized CNTs have widely been used to functionalize with metal or metal oxides since the defect sites act as anchoring for metal oxide binding. However, such defects on the tubes cause the decrease in electrical conductivity and stability, leading to lower catalyst performance. In the present study, at first, pristine multi-walled carbon nanotubes (MWNTs) were wrapped by pyridine-based polybenzimidazole (PyPBI) to which uniform NixCo3-xO4 nanocrystals were homogeneously deposited by the solvothermal method without damaging the MWNTs, in which PyPBI acted as efficient anchoring sites for the deposition of spinel oxide nanocrystals with ~5 nm size. The obtained catalyst (MWNT-PyPBI-NixCo3-xO4) outperformed most state-of-the-art non-precious metal-based bifunctional catalysts; namely, for OER, the potential at 10 mA cm(-2) and Tafel slope in 1 M KOH solution were 1.54 V vs. RHE and 42 mV dec(-1), respectively. For ORR, the onset and half-wave potentials are 0.918 V and 0.811 V vs. RHE, respectively. Moreover, the MWNT-PyPBI-NixCo3-xO4 demonstrates an excellent durability for both ORR and OER.

  14. Decorating unoxidized-carbon nanotubes with homogeneous Ni-Co spinel nanocrystals show superior performance for oxygen evolution/reduction reactions

    PubMed Central

    Yang, Jun; Fujigaya, Tsuyohiko; Nakashima, Naotoshi

    2017-01-01

    We present a new concept for homogeneous spinel nanocrystal-coating on high crystalline pristine-carbon nanotubes (CNTs) for efficient and durable oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). Oxidized CNTs have widely been used to functionalize with metal or metal oxides since the defect sites act as anchoring for metal oxide binding. However, such defects on the tubes cause the decrease in electrical conductivity and stability, leading to lower catalyst performance. In the present study, at first, pristine multi-walled carbon nanotubes (MWNTs) were wrapped by pyridine-based polybenzimidazole (PyPBI) to which uniform NixCo3−xO4 nanocrystals were homogeneously deposited by the solvothermal method without damaging the MWNTs, in which PyPBI acted as efficient anchoring sites for the deposition of spinel oxide nanocrystals with ~5 nm size. The obtained catalyst (MWNT-PyPBI-NixCo3−xO4) outperformed most state-of-the-art non-precious metal-based bifunctional catalysts; namely, for OER, the potential at 10 mA cm−2 and Tafel slope in 1 M KOH solution were 1.54 V vs. RHE and 42 mV dec−1, respectively. For ORR, the onset and half-wave potentials are 0.918 V and 0.811 V vs. RHE, respectively. Moreover, the MWNT-PyPBI-NixCo3−xO4 demonstrates an excellent durability for both ORR and OER. PMID:28358114

  15. Decorating unoxidized-carbon nanotubes with homogeneous Ni-Co spinel nanocrystals show superior performance for oxygen evolution/reduction reactions

    NASA Astrophysics Data System (ADS)

    Yang, Jun; Fujigaya, Tsuyohiko; Nakashima, Naotoshi

    2017-03-01

    We present a new concept for homogeneous spinel nanocrystal-coating on high crystalline pristine-carbon nanotubes (CNTs) for efficient and durable oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). Oxidized CNTs have widely been used to functionalize with metal or metal oxides since the defect sites act as anchoring for metal oxide binding. However, such defects on the tubes cause the decrease in electrical conductivity and stability, leading to lower catalyst performance. In the present study, at first, pristine multi-walled carbon nanotubes (MWNTs) were wrapped by pyridine-based polybenzimidazole (PyPBI) to which uniform NixCo3-xO4 nanocrystals were homogeneously deposited by the solvothermal method without damaging the MWNTs, in which PyPBI acted as efficient anchoring sites for the deposition of spinel oxide nanocrystals with ~5 nm size. The obtained catalyst (MWNT-PyPBI-NixCo3-xO4) outperformed most state-of-the-art non-precious metal-based bifunctional catalysts; namely, for OER, the potential at 10 mA cm-2 and Tafel slope in 1 M KOH solution were 1.54 V vs. RHE and 42 mV dec-1, respectively. For ORR, the onset and half-wave potentials are 0.918 V and 0.811 V vs. RHE, respectively. Moreover, the MWNT-PyPBI-NixCo3-xO4 demonstrates an excellent durability for both ORR and OER.

  16. Nano PtCu binary and PtCuAg ternary alloy catalysts for oxygen reduction reaction in proton exchange membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Zhou, Yanmei; Zhang, Dongming

    2015-03-01

    In order to decrease the cost and enhance the performance of the cathode catalyst for PEMFC, carbon supported PtCu and PtCuAg alloys with differential Ag content are synthesized by a borohydride chemical reduction. The oxygen reduction reaction (ORR) activity are tested by cyclic voltammetry (CV)and linear sweep voltammograms (LSV) in 0.5 M H2SO4. By comparison with the ORR activities of PtCu/C and a series of PtCuAg/C catalysts with differential metal atomic ratios of Pt:Cu:Ag, the PtCuAg/C catalyst with the atomic ratio on 3:10:1 (marked as PtCuAg/C(3:10:1)) shows the best catalytic activity. For the 200th cycles, the limited current reaches to 3.85 mA cm-2 for PtCuAg/C(3:10:1) with Pt-loading of 9.29 μgPt cm-2. The CV curves of the PtCuAg/C catalysts show one more pair of redox peaks of Ag compared with PtCu/C catalyst, which is much different from Pt-M alloy catalysts reported in other literature. The TEM and XRD as well as XPS results indicate that the enhanced ORR activity is the result of the smaller particle size, the crystal distortion and the more exposure of Pt atoms with the introduction of Ag for PtCuAg/C(3:10:1) catalyst.

  17. Nano Ce2O2S with Highly Enriched Oxygen-Deficient Ce(3+) Sites Supported by N and S Dual-Doped Carbon as an Active Oxygen-Supply Catalyst for the Oxygen Reduction Reaction.

    PubMed

    Yang, Liu; Cai, Zhuang; Hao, Liang; Xing, Zipeng; Dai, Ying; Xu, Xin; Pan, Siyu; Duan, Yaqiang; Zou, Jinlong

    2017-07-12

    The design of rare-earth-metal oxide/oxysulfide catalysts with high activity and durability for the oxygen reduction reaction (ORR) is still a grand challenge at present. In this study, Ce-species (Ce2O2S/CeO2)/N, S dual-doped carbon (Ce-species/NSC) catalysts with promising oxygen storage/release capacities are prepared at different temperatures (800-1000 °C) to enhance the ORR efficiency. Mechanisms for the effects of temperature on crystalline phase transition between CeO2 and Ce2O2S and structure evolution of Ce-species/NSCs are inferred to better understand their catalytic activity. Porous Ce2O2S/NSC (950 °C) catalyst as the air-breathing cathode exhibits a maximum power density of 1087.2 mW m(-2), which is higher than those of other Ce-species/NSCs and commercial Pt/C (989.13 mW m(-2)) in microbial fuel cells. The decline of the power density of Ce2O2S/NSC (950 °C) cathode is 8.7% after 80 days of operation, which is far lower than that of Pt/C (36.7%). Ce2O2S/NSC (950 °C) has a four-electron selectivity toward the ORR and a low charge-transfer resistance (5.49 Ω), contributing to high ORR activity and durability. The promising ORR catalytic activity of Ce2O2S/NSC (950 °C) is attributed to its high specific surface area (338.9 m(2) g(-1)), varied active sites, high electrical conductivity, and sufficient oxygen vacancies in the Ce2O2S skeleton. The high content of Ce(3+) in Ce2O2S/NSC (950 °C) facilitates the formation of more oxygen-deficient Ce(3+) sites that generate more oxygen vacancies to release/store more oxygen to stabilize the available oxygen for the ORR. Thus, this study provides a new perspective for preparation and application of this new type of the ORR catalyst.

  18. Facile synthesis of Rh-Pd alloy nanodendrites as highly active and durable electrocatalysts for oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Qi, Yue; Wu, Jianbo; Zhang, Hui; Jiang, Yingying; Jin, Chuanhong; Fu, Maoshen; Yang, Hong; Yang, Deren

    2014-05-01

    In addition to activity, durability of Pd-based catalysts in a highly corrosive medium has become one of the most important barriers to limit their industrial applications such as low-temperature fuel cell technologies. Here, Rh with a unique capability to resist against oxidation etching was incorporated into Pd-based catalysts to enhance both their activity and durability for oxygen reduction reaction (ORR). This idea was achieved through the synthesis of the Rh-Pd alloy nanodendrites by co-reducing Rh and Pd salt precursors in oleylamine (OAm) containing cetyltrimethylammonium bromide (CTAB). In this synthesis, Rh-Pd alloy nanostructures with Rh-Pd atomic ratios from 19 : 1 to 1 : 4 were generated by varying the molar ratios of Rh and Pd salt precursors. Interestingly, this variation of the molar ratios of the precursors from Rh rich to Pd rich would lead to the shape evolution of Rh-Pd alloy from dendritic nanostructures to spherical aggregations. We found that Br- ions derived from CTAB were also indispensible to the production of Rh-Pd alloy nanodendrites. Owing to the addition of highly stable Rh as well as the radical structure with a large number of low-coordinated sites on the arms, Rh-Pd alloy nanodendrites with a Rh-Pd atomic ratio of 4 : 1 (Rh80Pd20) exhibited a substantially enhanced electrocatalytic performance towards ORR with a 5% loss of mass activity during the accelerated stability test for 10 000 cycles compared to ~50% loss of the commercial Pt/C (E-TEK).In addition to activity, durability of Pd-based catalysts in a highly corrosive medium has become one of the most important barriers to limit their industrial applications such as low-temperature fuel cell technologies. Here, Rh with a unique capability to resist against oxidation etching was incorporated into Pd-based catalysts to enhance both their activity and durability for oxygen reduction reaction (ORR). This idea was achieved through the synthesis of the Rh-Pd alloy nanodendrites by co

  19. Ring-expansion reaction of oximes with aluminum reductants.

    PubMed

    Cho, Hidetsura; Iwama, Yusuke; Mitsuhashi, Nakako; Sugimoto, Kenji; Okano, Kentaro; Tokuyama, Hidetoshi

    2012-06-14

    The ring-expansion reactions of heterocyclic ketoximes and carbocyclic ketoximes with several reductants such as AlHCl2, AlH3 (alane), LiAlH4, LiAlH(OtBu)3, and (MeOCH2CH2O)2AlH2Na (Red-Al) were examined. Among reductants, AlHCl2 (LiAlH4:AlCl3 = 1:3) in cyclopentyl methyl ether (CPME) has been found to be a suitable reagent for the reaction, and the rearranged cyclic secondary amines were obtained in good to excellent yields.

  20. A nitrogen-doped mesoporous carbon containing an embedded network of carbon nanotubes as a highly efficient catalyst for the oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Li, Jin-Cheng; Zhao, Shi-Yong; Hou, Peng-Xiang; Fang, Ruo-Pian; Liu, Chang; Liang, Ji; Luan, Jian; Shan, Xu-Yi; Cheng, Hui-Ming

    2015-11-01

    A nitrogen-doped mesoporous carbon containing a network of carbon nanotubes (CNTs) was produced for use as a catalyst for the oxygen reduction reaction (ORR). SiO2 nanoparticles were decorated with clusters of Fe atoms to act as catalyst seeds for CNT growth, after which the material was impregnated with aniline. After polymerization of the aniline, the material was pyrolysed and the SiO2 was removed by acid treatment. The resulting carbon-based hybrid also contained some Fe from the CNT growth catalyst and was doped with N from the aniline. The Fe-N species act as active catalytic sites and the CNT network enables efficient electron transport in the material. Mesopores left by the removal of the SiO2 template provide short transport pathways and easy access to ions. As a result, the catalyst showed not only excellent ORR activity, with 59 mV more positive onset potential and 30 mV more positive half-wave potential than a Pt/C catalyst, but also much longer durability and stronger tolerance to methanol crossover than a Pt/C catalyst.A nitrogen-doped mesoporous carbon containing a network of carbon nanotubes (CNTs) was produced for use as a catalyst for the oxygen reduction reaction (ORR). SiO2 nanoparticles were decorated with clusters of Fe atoms to act as catalyst seeds for CNT growth, after which the material was impregnated with aniline. After polymerization of the aniline, the material was pyrolysed and the SiO2 was removed by acid treatment. The resulting carbon-based hybrid also contained some Fe from the CNT growth catalyst and was doped with N from the aniline. The Fe-N species act as active catalytic sites and the CNT network enables efficient electron transport in the material. Mesopores left by the removal of the SiO2 template provide short transport pathways and easy access to ions. As a result, the catalyst showed not only excellent ORR activity, with 59 mV more positive onset potential and 30 mV more positive half-wave potential than a Pt/C catalyst

  1. A highly efficient electrocatalyst for oxygen reduction reaction: phosphorus and nitrogen co-doped hierarchically ordered porous carbon derived from an iron-functionalized polymer

    NASA Astrophysics Data System (ADS)

    Deng, Chengwei; Zhong, Hexiang; Li, Xianfeng; Yao, Lan; Zhang, Huamin

    2016-01-01

    Heteroatom-doped carbon materials have shown respectable activity for the oxygen reduction reaction (ORR) in alkaline media. However, the performances of these materials are not satisfactory for energy conversion devices, such as fuel cells. Here, we demonstrate a new type of phosphorus and nitrogen co-doped hierarchically ordered porous carbon (PNHOPC) derived from an iron-functionalized mesoporous polymer through an evaporation-induced self-assembly process that simultaneously combines the carbonization and nitrogen doping processes. The soft template and the nitrogen doping process facilitate the formation of the hierarchically ordered structure for the PNHOPC. The catalyst possesses a large surface area (1118 cm2 g-1) and a pore volume of 1.14 cm3 g-1. Notably, it exhibits excellent ORR catalytic performance, superior stability and methanol tolerance in acidic electrolytes, thus making the catalyst promising for fuel cells. The correlations between the unique pore structure and the nitrogen and phosphorus configuration of the catalysts with high catalytic activity are thoroughly investigated.Heteroatom-doped carbon materials have shown respectable activity for the oxygen reduction reaction (ORR) in alkaline media. However, the performances of these materials are not satisfactory for energy conversion devices, such as fuel cells. Here, we demonstrate a new type of phosphorus and nitrogen co-doped hierarchically ordered porous carbon (PNHOPC) derived from an iron-functionalized mesoporous polymer through an evaporation-induced self-assembly process that simultaneously combines the carbonization and nitrogen doping processes. The soft template and the nitrogen doping process facilitate the formation of the hierarchically ordered structure for the PNHOPC. The catalyst possesses a large surface area (1118 cm2 g-1) and a pore volume of 1.14 cm3 g-1. Notably, it exhibits excellent ORR catalytic performance, superior stability and methanol tolerance in acidic

  2. Facile synthesis of Rh-Pd alloy nanodendrites as highly active and durable electrocatalysts for oxygen reduction reaction.

    PubMed

    Qi, Yue; Wu, Jianbo; Zhang, Hui; Jiang, Yingying; Jin, Chuanhong; Fu, Maoshen; Yang, Hong; Yang, Deren

    2014-06-21

    In addition to activity, durability of Pd-based catalysts in a highly corrosive medium has become one of the most important barriers to limit their industrial applications such as low-temperature fuel cell technologies. Here, Rh with a unique capability to resist against oxidation etching was incorporated into Pd-based catalysts to enhance both their activity and durability for oxygen reduction reaction (ORR). This idea was achieved through the synthesis of the Rh-Pd alloy nanodendrites by co-reducing Rh and Pd salt precursors in oleylamine (OAm) containing cetyltrimethylammonium bromide (CTAB). In this synthesis, Rh-Pd alloy nanostructures with Rh-Pd atomic ratios from 19 : 1 to 1 : 4 were generated by varying the molar ratios of Rh and Pd salt precursors. Interestingly, this variation of the molar ratios of the precursors from Rh rich to Pd rich would lead to the shape evolution of Rh-Pd alloy from dendritic nanostructures to spherical aggregations. We found that Br(-) ions derived from CTAB were also indispensible to the production of Rh-Pd alloy nanodendrites. Owing to the addition of highly stable Rh as well as the radical structure with a large number of low-coordinated sites on the arms, Rh-Pd alloy nanodendrites with a Rh-Pd atomic ratio of 4 : 1 (Rh80Pd20) exhibited a substantially enhanced electrocatalytic performance towards ORR with a 5% loss of mass activity during the accelerated stability test for 10 000 cycles compared to ∼ 50% loss of the commercial Pt/C (E-TEK).

  3. B, N co-doped carbon from cross-linking induced self-organization of boronate polymer for supercapacitor and oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Chang, Ying; Yuan, Conghui; Liu, Cheng; Mao, Jie; Li, Yuntong; Wu, Haiyang; Wu, Yuzhe; Xu, Yiting; Zeng, Birong; Dai, Lizong

    2017-10-01

    A novel strategy has been developed to generate B, N co-doped carbon materials (CNBs) through the pyrolysis of boronate polymer nanoparticles (BPNs) derived from the condensation reaction between catechol and boronic monomers. The morphology, surface area and heteroatom (viz. B and N) content of the CNBs can be easily adjusted by altering the molar ratio between catechol and boronic monomers. The supercapacitor and oxygen reduction reaction (ORR) performance of the CNBs are optimized. CNBs derived from equal molar ratio of catechol and boronic monomers exhibit favorable performance for supercapacitor, featuring a specific capacitance of up to 299.4 F/g at 0.2 A/g, an improved rate capability and excellent cycle stability. Notably, CNBs prepared using 1/2 molar ratio of catechol to boronic monomers show excellent ORR performance, as they demonstrate good electrocatalytic activity, high tolerance for methanol and long durability. Our findings may be of interest in the design of carbon materials with optimized electrochemical properties through the control over surface area and the content of heteroatom.

  4. Cobalt nanoparticles/nitrogen-doped graphene with high nitrogen doping efficiency as noble metal-free electrocatalysts for oxygen reduction reaction.

    PubMed

    Liang, Jingwen; Hassan, Mehboob; Zhu, Dongsheng; Guo, Liping; Bo, Xiangjie

    2017-03-15

    Nitrogen-doped graphene (N/GR) has been considered as active metal-free electrocatalysts for oxygen reduction reaction (ORR). However, the nitrogen (N) doping efficiency is very low and only few N atoms are doped into the framework of GR. To boost the N doping efficiency, in this work, a confined pyrolysis method with high N doping efficiency is used for the preparation of cobalt nanoparticles/nitrogen-doped GR (Co/N/GR). Under the protection of SiO2, the inorganic ligand NH3 in cobalt amine complex ([Co(NH3)6](3+)) is trapped in the confined space and then can be effectively doped into the framework of GR without the introduction of any carbon residues. Meanwhile, due to the redox reaction between the cobalt ions and carbon atoms of GR, Co nanoparticles are supported into the framework of N/GR. Due to prevention of GR layer aggregation with SiO2, the Co/N/GR with high dispersion provides sufficient surface area and maximum opportunity for the exposure of Co nanoparticles and active sites of N dopant. By combination of enhanced N doping efficiency, Co nanoparticles and high dispersion of GR sheets, the Co/N/GR is remarkably active, cheap and selective noble-metal free catalysts for ORR.

  5. Core/shell face-centered tetragonal FePd/Pd nanoparticles as an efficient non-Pt catalyst for the oxygen reduction reaction

    SciTech Connect

    Zhu, Huiyuan; Jiang, Guangming; Zhang, Xu; Shen, Bo; Wu, Liheng; Zhang, Sen; Lu, Gang; Wu, Zhongbiao; Sun, Shouheng

    2015-10-04

    We report the synthesis of core/shell face-centered tetragonal (fct)-FePd/Pd nanoparticles (NPs) via reductive annealing of core/shell Pd/Fe3O4 NPs followed by temperature-controlled Fe etching in acetic acid. Among three different kinds of core/shell FePd/Pd NPs studied (FePd core at similar to 8 nm and Pd shell at 0.27, 0.65, or 0.81 nm), the fct-FePd/Pd-0.65 NPs are the most efficient catalyst for the oxygen reduction reaction (ORR) in 0.1 M HClO4 with Pt-like activity and durability. This enhanced ORR catalysis arises from the desired Pd lattice compression in the 0.65 nm Pd shell induced by the fct-FePd core. Lastly, our study offers a general approach to enhance Pd catalysis in acid for ORB.

  6. Core/shell face-centered tetragonal FePd/Pd nanoparticles as an efficient non-Pt catalyst for the oxygen reduction reaction

    DOE PAGES

    Zhu, Huiyuan; Jiang, Guangming; Zhang, Xu; ...

    2015-10-04

    We report the synthesis of core/shell face-centered tetragonal (fct)-FePd/Pd nanoparticles (NPs) via reductive annealing of core/shell Pd/Fe3O4 NPs followed by temperature-controlled Fe etching in acetic acid. Among three different kinds of core/shell FePd/Pd NPs studied (FePd core at similar to 8 nm and Pd shell at 0.27, 0.65, or 0.81 nm), the fct-FePd/Pd-0.65 NPs are the most efficient catalyst for the oxygen reduction reaction (ORR) in 0.1 M HClO4 with Pt-like activity and durability. This enhanced ORR catalysis arises from the desired Pd lattice compression in the 0.65 nm Pd shell induced by the fct-FePd core. Lastly, our study offersmore » a general approach to enhance Pd catalysis in acid for ORB.« less

  7. Effect of cationic molecules on the oxygen reduction reaction on fuel cell grade Pt/C (20 wt%) catalyst in potassium hydroxide (aq, 1 mol dm(-3)).

    PubMed

    Ong, Ai Lien; Inglis, Kenneth K; Whelligan, Daniel K; Murphy, Sam; Varcoe, John R

    2015-05-14

    This study investigates the effect of 1 mmol dm(-3) concentrations of a selection of small cationic molecules on the performance of a fuel cell grade oxygen reduction reaction (ORR) catalyst (Johnson Matthey HiSPEC 3000, 20 mass% Pt/C) in aqueous KOH (1 mol dm(-3)). The cationic molecules studied include quaternary ammonium (including those based on bicyclic systems) and imidazolium types as well as a phosphonium example: these serve as fully solubilised models for the commonly encountered head-groups in alkaline anion-exchange membranes (AAEM) and anion-exchange ionomers (AEI) that are being developed for application in alkaline polymer electrolyte fuel cells (APEFCs), batteries and electrolysers. Both cyclic and hydrodynamic linear sweep rotating disk electrode voltammetry techniques were used. The resulting voltammograms and subsequently derived data (e.g. apparent electrochemical active surface areas, Tafel plots, and number of [reduction] electrons transferred per O2) were compared. The results show that the imidazolium examples produced the highest level of interference towards the ORR on the Pt/C catalyst under the experimental conditions used.

  8. Reduction of chemical reaction networks through delay distributions

    NASA Astrophysics Data System (ADS)

    Barrio, Manuel; Leier, André; Marquez-Lago, Tatiana T.

    2013-03-01

    Accurate modelling and simulation of dynamic cellular events require two main ingredients: an adequate description of key chemical reactions and simulation of such chemical events in reasonable time spans. Quite logically, posing the right model is a crucial step for any endeavour in Computational Biology. However, more often than not, it is the associated computational costs which actually limit our capabilities of representing complex cellular behaviour. In this paper, we propose a methodology aimed at representing chains of chemical reactions by much simpler, reduced models. The abridgement is achieved by generation of model-specific delay distribution functions, consecutively fed to a delay stochastic simulation algorithm. We show how such delay distributions can be analytically described whenever the system is solely composed of consecutive first-order reactions, with or without additional "backward" bypass reactions, yielding an exact reduction. For models including other types of monomolecular reactions (constitutive synthesis, degradation, or "forward" bypass reactions), we discuss why one must adopt a numerical approach for its accurate stochastic representation, and propose two alternatives for this. In these cases, the accuracy depends on the respective numerical sample size. Our model reduction methodology yields significantly lower computational costs while retaining accuracy. Quite naturally, computational costs increase alongside network size and separation of time scales. Thus, we expect our model reduction methodologies to significantly decrease computational costs in these instances. We anticipate the use of delays in model reduction will greatly alleviate some of the current restrictions in simulating large sets of chemical reactions, largely applicable in pharmaceutical and biological research.

  9. One Dimensional Graphitic Carbon Nitrides as Effective Metal-Free Oxygen Reduction Catalysts

    PubMed Central

    Tahir, Muhammad; Mahmood, Nasir; Zhu, Jinghan; Mahmood, Asif; Butt, Faheem K.; Rizwan, Syed; Aslam, Imran; Tanveer, M.; Idrees, Faryal; Shakir, Imran; Cao, Chuanbao; Hou, Yanglong

    2015-01-01

    To explore the effect of morphology on catalytic properties of graphitic carbon nitride (GCN), we have studied oxygen reduction reaction (ORR) performance of two different morphologies of GCN in alkaline media. Among both, tubular GCN react with dissolved oxygen in the ORR with an onset potential close to commercial Pt/C. Furthermore, the higher stability and excellent methanol tolerance of tubular GCN compared to Pt/C emphasizes its suitability for fuel cells. PMID:26201998

  10. Activity and Stability of Ruddlesden-Popper-Type La(n+1) Ni(n) O(3n+1) (n=1, 2, 3, and ∞) Electrocatalysts for Oxygen Reduction and Evolution Reactions in Alkaline Media.

    PubMed

    Yu, Jie; Sunarso, Jaka; Zhu, Yinlong; Xu, Xiaomin; Ran, Ran; Zhou, Wei; Shao, Zongping

    2016-02-18

    Increasing energy demands have stimulated intense research activity on cleaner energy conversion such as regenerative fuel cells and reversible metal-air batteries. It is highly challenging but desirable to develop low-cost bifunctional catalysts for both the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER), the lack of which is currently one of the major limiting components towards commercialization of these technologies. Here, we have conducted a systematic study on the OER and ORR performances of the Ruddlesden-Popper family of La(n+1)Ni(n) O(3n+1) (n=1, 2, 3, and ∞) in an alkaline medium for the first time. It is apparent that the Ni-O bond lengths and the hyperstoichiometric oxides in the rock-salt layers correlate with the ORR activities, whereas the OER activities appear to be influenced by the OH(-) content on the surface of the compounds. In our case, the electronic configuration fails to predict the electrocatalytic activity of these compounds. This work provides guidelines to develop new electrocatalysts with improved performances.

  11. The reductive decyanation reaction: an overview and recent developments

    PubMed Central

    2017-01-01

    This review presents an overview of the reductive decyanation reaction with a special interest for recent developments. This transformation allows synthetic chemists to take advantages of the nitrile functional group before its removal. Mechanistic details and applications to organic synthesis are provided. PMID:28326136

  12. Promotional Effect of Molten Carbonates on Proton Conductivity and Oxygen Reduction Reaction - an Experimental and Computational Study

    NASA Astrophysics Data System (ADS)

    Xiong, Xiaolei

    Recent research of Solid oxide fuel cells (SOFCs) is aimed to lower the operating temperature to an intermediate temperature (IT) range of 500 to 700°C, while maintaining a proper performance. This Ph.D. research project investigates the promotional effects of alkaline carbonate eutectics on the proton conductivity of proton conducting electrolytes and cathodic ORR reactivity in SOFCs by both experimental and computational methods. The ionic conductivity of the MC-BZY composite above 500°C increases with the higher loading of MC. The sample exhibited nearly a factor of two higher conductivity in H2-containing atmosphere than in air. First-principles DFT modeling further investigated proton transfer at the interface of BaZrO 3 and molten carbonate. With the presence of carbonate ion, the energy barrier for proton migration becomes as low as 0.332 eV. The modeling indicates the reduction of energy barrier is resulted from the change of rate-determining step from proton transfer between oxygen atoms to proton rotation around oxygen atom. Infiltration of MC into porous cathode can reduce the polarization of resistance (Rp), i.e., enhance the oxygen reduction reaction (ORR) activity. The EIS analysis shows that MC has a beneficial effect on reducing Rp for different cathodes including Au, La0.8Sr 0.2MnO3-delta(LSM), La0.6Sr0.4Co 0.2Fe0.8O3-delta(LSCF) and La2NiO 4+delta (LNO). Specifically, the study on MC loading effect was carried out on LSCF cathode. It shows that a higher loading makes a greater reduction on Rp and the degree of reduction is the same from 500 to 600°C. As the loading increases to 1.4 wt%, the degree of Rp reduction tends to reach a limit. First-principles DFT modeling was further used to investigate the incorporation of oxygen into MC. The formation of CO 52- in molten carbonate was considered as a chemisorption of gas oxygen on the surface of MC infiltrated cathodes. After the formation of CO52-, it reacts with another CO3 2- to form two CO42

  13. l-Glutamic acid assisted eco-friendly one-pot synthesis of sheet-assembled platinum-palladium alloy networks for methanol oxidation and oxygen reduction reactions.

    PubMed

    Shi, Ya-Cheng; Mei, Li-Ping; Wang, Ai-Jun; Yuan, Tao; Chen, Sai-Sai; Feng, Jiu-Ju

    2017-10-15

    In this work, bimetallic platinum-palladium sheet-assembled alloy networks (PtPd SAANs) were facilely synthesized by an eco-friendly one-pot aqueous approach under the guidance of l-glutamic acid at room temperature, without any additive, seed, toxic or organic solvent involved. l-Glutamic acid was served as the green shape-director and weak-stabilizing agent. A series of characterization techniques were employed to examine the morphology, structure and formation mechanism of the product. The architectures exhibited improved electrocatalytic activity and durable ability toward methanol oxidation reaction (MOR) and oxygen reduction reaction (ORR) in contrast with commercial Pt black and Pd black catalysts. This is ascribed to the unique structures of the obtained PtPd SAANs and the synergistic effects of the bimetals. These results demonstrate the potential application of the prepared catalyst in fuel cells. Copyright © 2017 Elsevier Inc. All rights reserved.

  14. Influence of cationic structures on oxygen reduction reaction at Pt electrode in fluorohydrogenate ionic liquids

    NASA Astrophysics Data System (ADS)

    Kiatkittikul, Pisit; Yamaguchi, Jumpei; Taniki, Ryosuke; Matsumoto, Kazuhiko; Nohira, Toshiyuki; Hagiwara, Rika

    2014-11-01

    Various parameters related to the oxygen reduction reaction (ORR) on a Pt electrode such as kinetically limited current density (jk), yield of H2O2 (XH2O2), and solubility (C) and diffusion coefficient (D) of oxygen were evaluated at 298 K in fluorohydrogenate ionic liquids (FHILs) using the rotating ring-disk electrode (RRDE) method. The FHILs investigated in this study were 1-ethyl-3-methylimidazolium fluorohydrogenates (EMIm(FH)1.3F and EMIm(FH)2.3F), N-ethyl-N-methyl pyrrolidinium fluorohydrogenates (EMPyr(FH)1.7F and EMPyr(FH)2.3F), trimethylsulfonium fluorohydrogenate (S111(FH)1.9F), triethyl-n-pentylphosphonium fluorohydrogenate (P2225(FH)2.1F), and 5-azoniaspiro[4.4]nonane fluorohydrogenate (AS[4.4](FH)2.0F). Among them, EMPyr(FH)1.7F showed the largest jk value (-1.5 mA cm-2) at 0.7 V vs. RHE. EMPyr(FH)1.7F, EMPyr(FH)2.3F, and P2225(FH)2.1F showed small XH2O2 values around 1.5% at a disk electrode potential of 0.2 V vs. RHE. The C and D values obtained for the FHILs were in the ranges of 0.23-1.3 mmol dm-3 and (1.1-3.2) × 10-5 cm2 s-1, respectively. The crossover currents of oxygen in the FHILs were estimated using the obtained C and D values, which were of the same order of magnitude as that for a 0.5 M H2SO4 aqueous solution.

  15. Nitrogen and sulfur co-doping of 3D hollow-structured carbon spheres as an efficient and stable metal free catalyst for the oxygen reduction reaction.

    PubMed

    Wu, Zexing; Liu, Rong; Wang, Jie; Zhu, Jing; Xiao, Weiping; Xuan, Cuijuan; Lei, Wen; Wang, Deli

    2016-12-07

    Three-dimensional, hollow-structured carbon sphere nanocomposites (N,S-hcs) doped with nitrogen and sulfur were prepared using a soft template approach followed by a high-temperature treatment. The synthesized N,S-hcs nanomaterials exhibited favourable catalytic activity for the oxygen reduction reaction (ORR) compared to carbon spheres doped solely with nitrogen (N-hcs), polypyrrole (PPY) solid nanoparticles and irregular fragments of polyaniline (PAN). These results demonstrated the co-doping of N/S and the relatively large surface area of the mesoporous carbon structure that enhanced the catalytic activity of the resulting material. Notably, the prepared N,S-hcs electrocatalysts provided four electron oxygen reduction selectivity, long-term durability and high resistance to methanol poisoning, all of which represented improvements over the conventional Pt/C electrocatalyst. The progress represented by this reported work is of great importance in the development of outstanding non-metal based electrocatalysts for the fuel cell industry.

  16. Cumulative effect of transition metals on nitrogen and fluorine co-doped graphite nanofibers: an efficient and highly durable non-precious metal catalyst for the oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Peera, S. Gouse; Arunchander, A.; Sahu, A. K.

    2016-07-01

    Nitrogen and fluorine co-doped graphite nanofibers (N/F-GNF) and their cumulative effect with Fe and Co have been developed as an alternative non-precious metal catalyst for efficient oxygen reduction reaction (ORR) in acidic media. The synergistic effect between the doped hetero atoms and the co-ordinated Fe and Co towards ORR activity and durability of the catalyst is deeply investigated. A high ORR onset potential comparable with commercial Pt/C catalyst is observed with the Fe-Co/NF-GNF catalyst, which indicates that this catalyst is a potential alternative to Pt/C. A fivefold increase in mass activity is achieved by the Fe-Co/NF-GNF catalyst compared to the simple N/F-GNF catalyst, which endorses the significant role of transition metal atoms in enhancing ORR activity. The advanced Fe-Co/NF-GNF catalyst also exhibits complete tolerance to CH3OH and CO. The Fe-Co/NF-GNF catalyst also exhibits excellent durability towards the ORR with only a 10 mV negative shift in its half wave potential after a 10 000 repeated potential cycling test, whereas in the case of a commercial Pt/C catalyst there was an ~110 mV negative shift under similar environmental conditions. More stringent corrosive test cycles were also performed by maintaining the cell as high as 1.4 V with a later decrease to 0.6 V vs. RHE for 300 cycles, which showed the excellent durability of the Fe-Co/NF-GNF catalyst in comparison with the Pt/C catalyst. XPS analysis of the Fe-Co/NF-GNF catalyst presents the ORR active chemical states of N (pyridinic-N and graphitic-N) and F (semi-ionic-F) and the co-ordinated sites of Fe and Co species with the dopants. The excellent performance and durability of the Fe-Co/NF-GNF catalyst is due to the synergistic effect between the hetero atoms dopants (N and F) and strong co-ordinating bonds of M-N-C, which protect the graphene layers around the metallic species and greatly mitigates the leaching of Co and Fe during the long term cycling test. The high activity and

  17. 2D Nanoporous Fe-N/C Nanosheets as Highly Efficient Non-Platinum Electrocatalysts for Oxygen Reduction Reaction in Zn-Air Battery.

    PubMed

    Yang, Zheng Kun; Lin, Ling; Xu, An-Wu

    2016-11-01

    It is an ongoing challenge to fabricate nonprecious oxygen reduction reaction (ORR) catalysts that can be comparable to or exceed the efficiency of platinum. A highly active non-platinum self-supporting Fe-N/C catalyst has been developed through the pyrolysis of a new type of precursor of iron coordination complex, in which 1,4-bis(1H-1,3,7,8-tetraazacyclopenta(1)phenanthren-2-yl)benzene (btcpb) functions as a ligand complexing Fe(II) ions. The optimal catalyst pyrolyzed at 700 °C (Fe-N/C-700) shows the best ORR activity with a half-wave potential (E1/2 ) of 840 mV versus reversible hydrogen electrode (RHE) in 0.1 m KOH, which is more positive than that of commercial Pt/C (E1/2 : 835 mV vs RHE). Additionally, the Fe-N/C-700 catalyst also exhibits high ORR activity in 0.1 m HClO4 with the onset potential and E1/2 comparable to those of the Pt/C catalyst. Notably, the Fe-N/C-700 catalyst displays superior durability (9.8 mV loss in 0.1 m KOH and 23.6 mV loss in 0.1 m HClO4 for E1/2 after 8000 cycles) and better tolerance to methanol than Pt/C. Furthermore, the Fe-N/C-700 catalyst can be used for fabricating the air electrode in Zn-air battery with a specific capacity of 727 mA hg(-1) at 5 mA cm(-2) and a negligible voltage loss after continuous operation for 110 h.

  18. Heterogeneous Electrocatalyst of Palladium-Cobalt-Phosphorus on Carbon Support for Oxygen Reduction Reaction in High Temperature Proton Exchange Membrane Fuel Cells.

    PubMed

    You, Dae Jong; Pak, Chanho; Jin, Seon-Ah; Lee, Kang Hee; Kwon, Kyungjung; Choi, Kyoung Hwan; Heo, Pil Won; Jang, Hongchul; Kim, Jun Young; Kim, Ji Man

    2016-05-01

    Palladium-cobalt-phosphorus (PdCoP) catalysts supported on carbon (Ketjen Black) were investigated as a cathode catalyst for oxygen reduction reaction (ORR) in high temperature proton exchange membrane fuel cells (HT-PEMFCs). The PdCoP catalyst was synthesized via a modified polyol process in teflon-sealed reactor by microwave-heating. From X-ray diffraction and transmission electron microscopic analysis, the PdCoP catalyst exhibits a face-centered cubic structure, similar to palladium (Pd), which is attributed to form a good solid solution of Co atoms and P atoms in the Pd lattice. The PdCoP nanoparticles with average diameter of 2.3 nm were uniformly distributed on the carbon support. The electrochemical surface area (ECSA) and ORR activity of PdP, PdCo and PdCoP catalysts were measured using a rotating disk electrode technique with cyclic voltammetry and the linear sweep method. The PdCoP catalysts showed the highest performances for ECSA and ORR, which might be attributed both to formation of small nanoparticle by phosphorus atom and to change in lattice constant of Pd by cobalt atom. Furthermore, The HT-PEMFCs single cell performance employing PdCoP catalyst exhibited an enhanced cell performance compared to a single cell using the PdP and PdCo catalysts. This result indicates the importance of electric and geometric control of Pd alloy nanoparticles that can improve the catalytic activity. This synergistic combination of Co and P with Pd could provide the direction of development of non-Pt catalyst for fuel cell system.

  19. Surface Proton Transfer Promotes Four-Electron Oxygen Reduction on Gold Nanocrystal Surfaces in Alkaline Solution

    DOE PAGES

    Lu, Fang; Zhang, Yu; Liu, Shizhong; ...

    2017-05-11

    Four-electron oxygen reduction reaction (4e-ORR), as a key pathway in energy conversion, is preferred over the two-electron reduction pathway that falls short in dissociating dioxygen molecules. Gold (Au) surfaces exhibit high sensitivity of the ORR pathway to its atomic structures. The long-standing puzzle remains unsolved why the Au surfaces with {100} sub-facets were exceptionally capable to catalyze the 4e-ORR in alkaline solution, though limited within a narrow potential window. Herein we report the discovery of a dominant 4e-ORR over the whole potential range on {310} surface of Au nanocrystal shaped as truncated ditetragonal prism (TDP). In contrast, ORR pathways onmore » single-crystalline facets of shaped nanoparticles, including {111} on nano-octahedra and {100} on nano-cubes, are similar to their single-crystal counterparts. Combining our experimental results with density functional theory calculations, we elucidate the key role of surface proton transfers from co-adsorbed H2O molecules in activating the facet- and potential-dependent 4e ORR on Au in alkaline solutions. These results elucidate how surface atomic structures determine the reaction pathways via bond scission and formation among weakly adsorbed water and reaction intermediates. The new insight helps in developing facet-specific nanocatalysts for various reactions.« less

  20. Surface Proton Transfer Promotes Four-Electron Oxygen Reduction on Gold Nanocrystal Surfaces in Alkaline Solution.

    PubMed

    Lu, Fang; Zhang, Yu; Liu, Shizhong; Lu, Deyu; Su, Dong; Liu, Mingzhao; Zhang, Yugang; Liu, Ping; Wang, Jia X; Adzic, Radoslav R; Gang, Oleg

    2017-05-31

    Four-electron oxygen reduction reaction (4e-ORR), a key pathway in energy conversion, is preferred over the two-electron reduction pathway that falls short in dissociating dioxygen molecules. Gold surfaces exhibit high sensitivity of the ORR pathway to its atomic structures. A long-standing puzzle remains unsolved: why the Au surfaces with {100} sub-facets were exceptionally capable to catalyze the 4e-ORR in alkaline solution, though limited within a narrow potential window. Herein we report the discovery of a dominant 4e-ORR over the whole potential range on {310} surface of Au nanocrystal shaped as truncated ditetragonal prism (TDP). In contrast, ORR pathways on single-crystalline facets of shaped nanoparticles, including {111} on nano-octahedra and {100} on nanocubes, are similar to their single-crystal counterparts. Combining our experimental results with density functional theory calculations, we elucidate the key role of surface proton transfers from co-adsorbed H2O molecules in activating the facet- and potential-dependent 4e-ORR on Au in alkaline solutions. These results elucidate how surface atomic structures determine the reaction pathways via bond scission and formation among weakly adsorbed water and reaction intermediates. The new insight helps in developing facet-specific nanocatalysts for various reactions.

  1. Computerized reduction of elementary reaction sets for combustion modeling

    NASA Technical Reports Server (NTRS)

    Wikstrom, Carl V.

    1991-01-01

    If the entire set of elementary reactions is to be solved in the modeling of chemistry in computational fluid dynamics, a set of stiff ordinary differential equations must be integrated. Some of the reactions take place at very high rates, requiring short time steps, while others take place more slowly and make little progress in the short time step integration. The goal is to develop a procedure to automatically obtain sets of finite rate equations, consistent with a partial equilibrium assumptions, from an elementary set appropriate to local conditions. The possibility of computerized reaction reduction was demonstrated. However, the ability to use the reduced reaction set depends on the ability of the CFD approach in incorporate partial equilibrium calculations into the computer code. Therefore, the results should be tested on a code with partial equilibrium capability.

  2. Reaction Wheel Disturbance Reduction Method Using Disturbance Measurement Table

    NASA Astrophysics Data System (ADS)

    Cheon, Dong-Ik; Jang, Eun-Jeong; Oh, Hwa-Suk

    2011-12-01

    Momentum changing actuators like reaction wheels and control moment gyros are generally used for spacecraft attitude control. This type of actuators produces force and torque disturbances. These disturbances must be reduced since they degrade the quality of spacecraft attitude control. Major disturbances are mainly due to static and dynamic imbalances. This paper gives attention to the reduction of the static and dynamic imbalance. Force/torque measurement system is used to measure the disturbance of the test reaction wheel. An identification method for the location and magnitude of the imbalance is suggested, and the corrections of the imbalance are performed using balancing method. Through balancing, the static and dynamic imbalance is remarkably reduced

  3. 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

  4. From Chlorella to Nestlike Framework Constructed with Doped Carbon Nanotubes: A Biomass-Derived, High-Performance, Bifunctional Oxygen Reduction/Evolution Catalyst.

    PubMed

    Wang, Guanghua; Deng, Yijie; Yu, Jinnan; Zheng, Long; Du, Li; Song, Huiyu; Liao, Shijun

    2017-09-20

    The development of effective bifunctional catalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is significant for energy conversion systems, such as Li-air batteries, fuel cells, and water splitting technologies. Herein, a Chlorella-derived catalyst with a nestlike framework, composed of bamboolike nanotubes that encapsulate cobalt nanoparticles, has been prepared through a facile pyrolysis process. It achieves perfect bifunctional catalysis both in ORR and OER on a single catalyst. For our optimal catalyst Co/M-Chlorella-900, its ORR half-wave potential is positively shifted by 40 mV compared to that of a commercial Pt/C catalyst, and the overpotential at 10 mA cm(-2) for the OER is 23 mV lower than that of a commercial IrO2/C catalyst in an alkaline medium. This superior bifunctional catalytic performance is benefited from the simultaneous increase of pyridinic N sites for ORR and graphitic N sites for OER. In addition, N-doped carbon-encapsulated Co nanoparticles improve both ORR and OER performance by forming new active centers. The unique nestlike carbon nanotube framework not only afforded highly dense ORR and OER active sites but also promoted the electron and mass transfer. Our catalyst also displays notable durability during the ORR and OER, making it promising for use in ORR/OER-related energy conversion systems.

  5. Role of Cu-Ion Doping in Cu-α-MnO2 Nanowire Electrocatalysts for the Oxygen Reduction Reaction

    DOE PAGES

    Davis, Danae J.; Lambert, Timothy N.; Vigil, Julian A.; ...

    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

  6. Novel RuCoSe as non-platinum catalysts for oxygen reduction reaction in microbial fuel cells

    NASA Astrophysics Data System (ADS)

    Rozenfeld, Shmuel; Schechter, Michal; Teller, Hanan; Cahan, Rivka; Schechter, Alex

    2017-09-01

    Microbial electrochemical cells (MECs) are explored for the conversion of acetate directly to electrical energy. This device utilizes a Geobacter sulfurreducens anode and a novel RuCoSe air cathode. RuCoSe synthesized in selected compositions by a borohydride reduction method produces amorphous structures of powdered agglomerates. Oxygen reduction reaction (ORR) was measured in a phosphate buffer solution pH 7 using a rotating disc electrode (RDE), from which the kinetic current (ik) was measured as a function of potential and composition. The results show that ik of RuxCoySe catalysts increases in the range of XRu = 0.25 > x > 0.7 and y < 0.15 for all tested potentials. A poisoning study of RuCoSe and Pt catalysts in a high concentration acetate solution shows improved tolerance of RuCoSe to this fuel at acetate concentration ≥500 mM. MEC discharge plots under physiological conditions show that ∼ RuCo2Se (sample S3) has a peak power density of 750 mW cm-2 which is comparable with Pt 900 mW cm-2.

  7. Deep-Eutectic Solvents Derived Nitrogen-Doped Graphitic Carbon as a Superior Electrocatalyst for Oxygen Reduction.

    PubMed

    Luo, Rui; Liu, Chao; Li, Jiansheng; Wang, Chaohai; Sun, Xiuyun; Shen, Jinyou; Han, Weiqing; Wang, Lianjun

    2017-09-18

    The activity and stability of electrocatalyst for oxygen reduction reaction (ORR) essentially depends on its structural and compositional properties. Herein, we report the facile preparation of nitrogen-doped graphitic carbon (NGC) via the pyrolysis of deep-eutectic solvents (DESs) as a superior electrocatalyst for ORR. The resulting NGCs possess high surface areas, rich nitrogen content, and favorable graphitization degree, all of which are highly desired for the ORR catalysts. The effects of the pyrolysis temperature on the ORR performance of the final products are explored. The results implied that the material fabricated at 900 °C (NGC900) is identified as the best ORR catalyst in the series of samples. Specifically, NGC900 shows efficient performance toward ORR with an onset potential of 0.97 V and a half potential of 0.84 V, which bears comparison with the commercial Pt/C catalyst with enhanced stability in the alkaline media. The superior ORR performance of NGC900 may be ascribed to the balance between the surface area, pyridinic nitrogen, and defect of NGCs. The rational design of NGCs with an efficient ORR activity and stability based on the low-cost DESs implies adequate support for the development of energy devices in practical application.

  8. Nitrogen and sulfur co-doped carbon with three-dimensional ordered macroporosity: An efficient metal-free oxygen reduction catalyst derived from ionic liquid

    NASA Astrophysics Data System (ADS)

    Wu, Hui; Shi, Liang; Lei, Jiaheng; Liu, Dan; Qu, Deyu; Xie, Zhizhong; Du, Xiaodi; Yang, Peng; Hu, Xiaosong; Li, Junsheng; Tang, Haolin

    2016-08-01

    The development of efficient and durable catalyst for oxygen reduction reaction (ORR) is critical for the practical application of proton exchange membrane fuel cell (PEMFC). A novel imidazole based ionic liquid is synthesized in this study and used subsequently for the preparation of a N and S co-doped metal-free catalyst with three dimensional ordered microstructure. The catalyst prepared at 1100 °C showed improved ORR catalytic performance and stability compared to commercial Pt/C catalyst. We demonstrate that the high graphitic N content and high degree of graphitization of the synthesized catalyst is responsible for its superb ORR activity. Our results suggest that the N and S co-doped metal-free catalyst reported here is a promising alternative to traditional ORR catalyst based on noble metal. Furthermore, the current study also demonstrate that importance of morphology engineering in the development of high performance ORR catalyst.

  9. Fabrication of PdCo Bimetallic Nanoparticles Anchored on Three-Dimensional Ordered N-Doped Porous Carbon as an Efficient Catalyst for Oxygen Reduction Reaction.

    PubMed

    Xue, Hairong; Tang, Jing; Gong, Hao; Guo, Hu; Fan, Xiaoli; Wang, Tao; He, Jianping; Yamauchi, Yusuke

    2016-08-17

    PdCo bimetallic nanoparticles (NPs) anchored on three-dimensional (3D) ordered N-doped porous carbon (PdCo/NPC) were fabricated by an in situ synthesis. Within this composite, N-doped porous carbon (NPC) with an ordered mesoporous structure possesses a high surface area (659.6 m(2) g(-1)), which can facilitate electrolyte infiltration. NPC also acts as a perfect 3D conductive network, guaranteeing fast electron transport. In addition, homogeneously distributed PdCo alloy NPs (∼15 nm) combined with the doping of the N element can significantly improve the electrocatalytic activity for the oxygen reduction reaction (ORR). Due to the structural and material superiority, although the weight percentage of PdCo NPs (∼8 wt%) is much smaller than that of commercial Pt/C (20 wt%), the PdCo/NPC catalyst exhibits similar excellent electrocatalytic activity; however, its superior durability and methanol-tolerance ability of the ORR are as great as those of commercial Pt/C in alkaline media.

  10. Tetrahedral Palladium Nanocrystals: A New Support for Platinum Monolayer Electrocatalysts with High Activity and Stability in the Oxygen Reduction Reaction

    SciTech Connect

    Gong, Kuanping; Choi, YongMan; Vukmirovic, Miomir B.; Liu, Ping; Ma, Chao; Su, Dong; Adzic, Radoslav R.

    2012-10-01

    The recent availability of tetrahedral palladium (PdTH) nanocrystals with cleaned surfaces allowed us to evaluate their facet-specific electrochemical properties as a new support of platinum monolayer (PtML) catalysts. The Pd–PtML core-shell electrocatalyst was examined by combining structural analyses and Density Functional Theory (DFT) with electrochemical techniques. The surfaces of the PdTH core are composed of (111) facets wherein the Pd atoms are highly coordinated and have low surface energy. Our results revealed that in comparison with sphere Pd (PdSP)-supported PtML or pure Pt, the PdTH-supported PtML features more surface contraction and a downshift of d-band relative to the Fermi level. These geometric- and electronic-effects determine the higher activity of PtML/PdTH/C for the oxygen reduction reaction (ORR) compared to that of PtML/PdSP/C. This shape-property interdependence illuminated new approaches to basic- and applied- research on Pt-based ORR electrocatalysts of significant importance to the widespread use of fuel cells.

  11. High Performance and Cost-Effective Direct Methanol Fuel Cells: Fe-N-C Methanol-Tolerant Oxygen Reduction Reaction Catalysts.

    PubMed

    Sebastián, David; Serov, Alexey; Artyushkova, Kateryna; Gordon, Jonathan; Atanassov, Plamen; Aricò, Antonino S; Baglio, Vincenzo

    2016-08-09

    Direct methanol fuel cells (DMFCs) offer great advantages for the supply of power with high efficiency and large energy density. The search for a cost-effective, active, stable and methanol-tolerant catalyst for the oxygen reduction reaction (ORR) is still a great challenge. In this work, platinum group metal-free (PGM-free) catalysts based on Fe-N-C are investigated in acidic medium. Post-treatment of the catalyst improves the ORR activity compared with previously published PGM-free formulations and shows an excellent tolerance to the presence of methanol. The feasibility for application in DMFC under a wide range of operating conditions is demonstrated, with a maximum power density of approximately 50 mW cm(-2) and a negligible methanol crossover effect on the performance. A review of the most recent PGM-free cathode formulations for DMFC indicates that this formulation leads to the highest performance at a low membrane-electrode assembly (MEA) cost. Moreover, a 100 h durability test in DMFC shows suitable applicability, with a similar performance-time behavior compared to common MEAs based on Pt cathodes. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. (La1-xSrx)0.98MnO3 perovskite with A-site deficiencies toward oxygen reduction reaction in aluminum-air batteries

    NASA Astrophysics Data System (ADS)

    Xue, Yejian; Miao, He; Sun, Shanshan; Wang, Qin; Li, Shihua; Liu, Zhaoping

    2017-02-01

    The strontium doped Mn-based perovskites have been proposed as one of the best oxygen reduction reaction catalysts (ORRCs) to substitute the noble metal. However, few studies have investigated the catalytic activities of LSM with the A-site deficiencies. Here, the (La1-xSrx)0.98MnO3 (LSM) perovskites with A-site deficiencies are prepared by a modified solid-liquid method. The structure, morphology, valence state and oxygen adsorption behaviors of these LSM samples are characterized, and their catalytic activities toward ORR are studied by the rotating ring-disk electrode (RRDE) and aluminum-air battery technologies. The results show that the appropriate doping with Sr and introducing A-site stoichiometry can effectively tailor the Mn valence and increase the oxygen adsorption capacity of LSM. Among all the LSM samples in this work, the (La0.7Sr0.3)0.98MnO3 perovskite composited with 50% carbon (50%LSM30) exhibits the best ORR catalytic activity due to the excellent oxygen adsorption capacity. Also, this catalyst has much higher durability than that of commercial 20%Pt/C. Moreover, the maximum power density of the aluminum-air battery using 50%LSM30 as the ORRC can reach 191.3 mW cm-2. Our work indicates that the LSM/C composite catalysts with A-site deficiencies can be used as a promising ORRC in the metal-air batteries.

  13. 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.

  14. Influence of sp(3)-sp(2) Carbon Nanodomains on Metal/Support Interaction, Catalyst Durability, and Catalytic Activity for the Oxygen Reduction Reaction.

    PubMed

    Campos-Roldán, Carlos A; Ramos-Sánchez, Guadalupe; Gonzalez-Huerta, Rosa G; Vargas García, Jorge R; Balbuena, Perla B; Alonso-Vante, Nicolas

    2016-09-07

    In this work, platinum nanoparticles were impregnated by two different techniques, namely the carbonyl chemical route and photodeposition, onto systematically surface-modified multiwalled carbon nanotubes. The different interactions between platinum nanoparticles with sp(2)-sp(3) carbon nanodomains were investigated. The oxidation of an adsorbed monolayer of carbon monoxide, used to probe electronic catalytic modification, suggests a selective nucleation of platinum nanoparticles onto sp(2) carbon nanodomains when photodeposition synthesis is carried out. XPS attests the catalytic center electronic modification obtained by photodeposition. DFT calculations were used to determine the interaction energy of a Pt cluster with sp(2) and sp(3) carbon surfaces as well as with oxidized ones. The interaction energy and electronic structure of the platinum cluster presents dramatic changes as a function of the support surface chemistry, which also modifies its catalytic properties evaluated by the interaction with CO. The interaction energy was calculated to be 8-fold higher on sp(3) and oxidized surfaces in comparison to sp(2) domains. Accelerated Stability Test (AST) was applied only on the electronic-modified materials to evaluate the active phase degradation and their activity toward oxygen reduction reaction (ORR). The stability of photodeposited materials is correlated with the surface chemical nature of supports indicating that platinum nanoparticles supported onto multiwalled carbon nanotubes with the highest sp(2) character show the higher stability and activity toward ORR.

  15. A review of the stability and durability of non-precious metal catalysts for the oxygen reduction reaction in proton exchange membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Banham, Dustin; Ye, Siyu; Pei, Katie; Ozaki, Jun-ichi; Kishimoto, Takeaki; Imashiro, Yasuo

    2015-07-01

    A major hurdle to the widespread commercialization of proton exchange membrane fuel cells (PEMFCs) is the high loading of noble metal (Pt/Pt-alloy) catalyst at the cathode, which is necessary to facilitate the inherently sluggish oxygen reduction reaction (ORR). To eliminate the use of Pt/Pt-alloy catalysts at the cathode of PEMFCs and thus significantly reduce the cost, extensive research on non-precious metal catalysts (NPMCs) has been carried out over the past decade. Major advances in improving the ORR activity of NPMCs, particularly Fe- and Co-based NPMCs, have elevated these materials to a level at which they can start to be considered as potential alternatives to Pt/Pt-alloy catalysts. Unfortunately, the stability (performance loss following galvanostatic experiments) of these materials is currently unacceptably low and the durability (performance loss following voltage cycling) remains uncertain. The three primary mechanisms of instability are: (a) Leaching of the metal site, (b) Oxidative attack by H2O2, and (c) Protonation followed by possible anion adsorption of the active site. While (a) has largely been solved, further work is required to understand and prevent losses from (b) and/or (c). Thus, this review is focused on historical progress in (and possible future strategies for) improving the stability/durability of NPMCs.

  16. 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.

  17. 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) .

  18. High performance platinum single atom electrocatalyst for oxygen reduction reaction

    PubMed Central

    Liu, Jing; Jiao, Menggai; Lu, Lanlu; Barkholtz, Heather M.; Li, Yuping; Wang, Ying; Jiang, Luhua; Wu, Zhijian; Liu, Di-jia; Zhuang, Lin; Ma, Chao; Zeng, Jie; Zhang, Bingsen; Su, Dangsheng; Song, Ping; Xing, Wei; Xu, Weilin; Wang, Ying; Jiang, Zheng; Sun, Gongquan

    2017-01-01

    For the large-scale sustainable implementation of polymer electrolyte membrane fuel cells in vehicles, high-performance electrocatalysts with low platinum consumption are desirable for use as cathode material during the oxygen reduction reaction in fuel cells. Here we report a carbon black-supported cost-effective, efficient and durable platinum single-atom electrocatalyst with carbon monoxide/methanol tolerance for the cathodic oxygen reduction reaction. The acidic single-cell with such a catalyst as cathode delivers high performance, with power density up to 680 mW cm−2 at 80 °C with a low platinum loading of 0.09 mgPt cm−2, corresponding to a platinum utilization of 0.13 gPt kW−1 in the fuel cell. Good fuel cell durability is also observed. Theoretical calculations reveal that the main effective sites on such platinum single-atom electrocatalysts are single-pyridinic-nitrogen-atom-anchored single-platinum-atom centres, which are tolerant to carbon monoxide/methanol, but highly active for the oxygen reduction reaction. PMID:28737170

  19. High performance platinum single atom electrocatalyst for oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Liu, Jing; Jiao, Menggai; Lu, Lanlu; Barkholtz, Heather M.; Li, Yuping; Wang, Ying; Jiang, Luhua; Wu, Zhijian; Liu, Di-Jia; Zhuang, Lin; Ma, Chao; Zeng, Jie; Zhang, Bingsen; Su, Dangsheng; Song, Ping; Xing, Wei; Xu, Weilin; Wang, Ying; Jiang, Zheng; Sun, Gongquan

    2017-07-01

    For the large-scale sustainable implementation of polymer electrolyte membrane fuel cells in vehicles, high-performance electrocatalysts with low platinum consumption are desirable for use as cathode material during the oxygen reduction reaction in fuel cells. Here we report a carbon black-supported cost-effective, efficient and durable platinum single-atom electrocatalyst with carbon monoxide/methanol tolerance for the cathodic oxygen reduction reaction. The acidic single-cell with such a catalyst as cathode delivers high performance, with power density up to 680 mW cm-2 at 80 °C with a low platinum loading of 0.09 mgPt cm-2, corresponding to a platinum utilization of 0.13 gPt kW-1 in the fuel cell. Good fuel cell durability is also observed. Theoretical calculations reveal that the main effective sites on such platinum single-atom electrocatalysts are single-pyridinic-nitrogen-atom-anchored single-platinum-atom centres, which are tolerant to carbon monoxide/methanol, but highly active for the oxygen reduction reaction.

  20. High performance platinum single atom electrocatalyst for oxygen reduction reaction.

    PubMed

    Liu, Jing; Jiao, Menggai; Lu, Lanlu; Barkholtz, Heather M; Li, Yuping; Wang, Ying; Jiang, Luhua; Wu, Zhijian; Liu, Di-Jia; Zhuang, Lin; Ma, Chao; Zeng, Jie; Zhang, Bingsen; Su, Dangsheng; Song, Ping; Xing, Wei; Xu, Weilin; Wang, Ying; Jiang, Zheng; Sun, Gongquan

    2017-07-24

    For the large-scale sustainable implementation of polymer electrolyte membrane fuel cells in vehicles, high-performance electrocatalysts with low platinum consumption are desirable for use as cathode material during the oxygen reduction reaction in fuel cells. Here we report a carbon black-supported cost-effective, efficient and durable platinum single-atom electrocatalyst with carbon monoxide/methanol tolerance for the cathodic oxygen reduction reaction. The acidic single-cell with such a catalyst as cathode delivers high performance, with power density up to 680 mW cm(-2) at 80 °C with a low platinum loading of 0.09 mgPt cm(-2), corresponding to a platinum utilization of 0.13 gPt kW(-1) in the fuel cell. Good fuel cell durability is also observed. Theoretical calculations reveal that the main effective sites on such platinum single-atom electrocatalysts are single-pyridinic-nitrogen-atom-anchored single-platinum-atom centres, which are tolerant to carbon monoxide/methanol, but highly active for the oxygen reduction reaction.

  1. Low NO Concentration Dependence of Reductive Nitrosylation Reaction of Hemoglobin*

    PubMed Central

    Tejero, Jesús; Basu, Swati; Helms, Christine; Hogg, Neil; King, S. Bruce; Kim-Shapiro, Daniel B.; Gladwin, Mark T.

    2012-01-01

    The reductive nitrosylation of ferric (met)hemoglobin is of considerable interest and remains incompletely explained. We have previously observed that at low NO concentrations the reaction with tetrameric hemoglobin occurs with an observed rate constant that is at least 5 times faster than that observed at higher concentrations. This was ascribed to a faster reaction of NO with a methemoglobin-nitrite complex. We now report detailed studies of this reaction of low NO with methemoglobin. Nitric oxide paradoxically reacts with ferric hemoglobin with faster observed rate constants at the lower NO concentration in a manner that is not affected by changes in nitrite concentration, suggesting that it is not a competition between NO and nitrite, as we previously hypothesized. By evaluation of the fast reaction in the presence of allosteric effectors and isolated β- and α-chains of hemoglobin, it appears that NO reacts with a subpopulation of β-subunit ferric hemes whose population is influenced by quaternary state, redox potential, and hemoglobin dimerization. To further characterize the role of nitrite, we developed a system that oxidizes nitrite to nitrate to eliminate nitrite contamination. Removal of nitrite does not alter reaction kinetics, but modulates reaction products, with a decrease in the formation of S-nitrosothiols. These results are consistent with the formation of NO2/N2O3 in the presence of nitrite. The observed fast reductive nitrosylation observed at low NO concentrations may function to preserve NO bioactivity via primary oxidation of NO to form nitrite or in the presence of nitrite to form N2O3 and S-nitrosothiols. PMID:22493289

  2. Nitrogen-doped nanoporous carbon derived from waste pomelo peel as a metal-free electrocatalyst for the oxygen reduction reaction.

    PubMed

    Yuan, Wenjing; Feng, Yi; Xie, Anjian; Zhang, Xiuzhen; Huang, Fangzhi; Li, Shikuo; Zhang, Xing; Shen, Yuhua

    2016-04-28

    The development of a new catalyst for the low-cost, environmentally friendly and highly efficient oxygen reduction reaction (ORR) is important for the commercialization of fuel cells. Herein, a smart strategy was proposed for the preparation of a novel nitrogen-doped nanoporous carbon (N-PC) using resource-rich pomelo peel, a type of waste, as starting material. The typical product (N-PC-1000) possesses a high BET surface area (up to 1444.9 m2 g(-1)), porous structure and high graphitic N content. In alkaline and acidic media, the N-PC-1000 shows not only decent catalytic activities in terms of onset potential and current density, but also has excellent tolerance to methanol poisoning effects and durability. This study provides worthy inspiration for using other environmental wastes to prepare related functional carbon materials with a variety of promising practical applications such as supercapacitors and lithium-ion batteries.

  3. Investigations of oxygen reduction reactions in non-aqueous electrolytes and the lithium-air battery

    NASA Astrophysics Data System (ADS)

    O'Laoire, Cormac Micheal

    Unlocking the true energy capabilities of the lithium metal negative electrode in a lithium battery has until now been limited by the low capacity intercalation and conversion reactions at the positive electrodes. This is overcome by removing these electrodes and allowing lithium to react directly with oxygen in the atmosphere forming the Li-air battery. Chapter 2 discusses the intimate role of electrolyte, in particular the role of ion conducting salts on the mechanism and kinetics of oxygen reduction in non-aqueous electrolytes designed for such applications and in determining the reversibility of the electrode reactions. Such fundamental understanding of this high energy density battery is crucial to harnessing its full energy potential. The kinetics and mechanisms of O2 reduction in solutions of hexafluorophosphate salts of the general formula X+ PF6-, where, X = tetra butyl ammonium (TBA), K, Na and Li, in acetonitrile have been studied on glassy carbon electrodes using cyclic voltammetry (CV) and rotating disk electrode (RDE) techniques. Our results show that cation choice strongly influences the reduction mechanism of O2. Electrochemical data supports the view that alkali metal oxides formed via electrochemical and chemical reactions passivate the electrode surface inhibiting the kinetics and reversibility of the processes. The O2 reduction mechanisms in the presence of the different cations have been supplemented by kinetic parameters determined from detailed analyses of the CV and RDE data. The organic solvent present in the Li+-conducting electrolyte has a major role on the reversibility of each of the O2 reduction products as found from the work discussed in the next chapter. A fundamental study of the influence of solvents on the oxygen reduction reaction (ORR) in a variety of non-aqueous electrolytes was conducted in chapter 4. In this work special attention was paid to elucidate the mechanism of the oxygen electrode processes in the rechargeable Li

  4. Single Platinum Atoms Electrocatalysts: Oxygen Reduction and Hydrogen Oxidation Reactions

    DOE PAGES

    Vukmirovic, Miomir B.; Teeluck, Krishani M.; Liu, Ping; ...

    2017-08-08

    We prepared atomically dispersed catalyst consisting of Pt atoms arranged in a c(2 × 2) array on RuO2(110) substrate. A large interatomic distance of Pt atoms in a c(2 × 2) phase precludes the reactants to interact with more than one Pt atoms. A strong bond of Pt atoms with RuO2 prevents agglomeration of Pt atoms to form 2D-islands or 3D-clusters. The activities of single Pt atom catalyst for the oxygen reduction and hydrogen oxidation reactions were determined and compared with those of bulk Pt. It has lower catalytic activity for the oxygen reduction reaction and similar activity for hydrogenmore » oxidation reaction compared to Pt(111). This was explained by a large calculated up-shift of the dband center of Pt atoms and larger Pt-Pt interatomic distance than that of Pt(111). Our information is of considerable interest for further development of electrocatalysis.« less

  5. Nitrogen-doped nanoporous carbon derived from waste pomelo peel as a metal-free electrocatalyst for the oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Yuan, Wenjing; Feng, Yi; Xie, Anjian; Zhang, Xiuzhen; Huang, Fangzhi; Li, Shikuo; Zhang, Xing; Shen, Yuhua

    2016-04-01

    The development of a new catalyst for the low-cost, environmentally friendly and highly efficient oxygen reduction reaction (ORR) is important for the commercialization of fuel cells. Herein, a smart strategy was proposed for the preparation of a novel nitrogen-doped nanoporous carbon (N-PC) using resource-rich pomelo peel, a type of waste, as starting material. The typical product (N-PC-1000) possesses a high BET surface area (up to 1444.9 m2 g-1), porous structure and high graphitic N content. In alkaline and acidic media, the N-PC-1000 shows not only decent catalytic activities in terms of onset potential and current density, but also has excellent tolerance to methanol poisoning effects and durability. This study provides worthy inspiration for using other environmental wastes to prepare related functional carbon materials with a variety of promising practical applications such as supercapacitors and lithium-ion batteries.The development of a new catalyst for the low-cost, environmentally friendly and highly efficient oxygen reduction reaction (ORR) is important for the commercialization of fuel cells. Herein, a smart strategy was proposed for the preparation of a novel nitrogen-doped nanoporous carbon (N-PC) using resource-rich pomelo peel, a type of waste, as starting material. The typical product (N-PC-1000) possesses a high BET surface area (up to 1444.9 m2 g-1), porous structure and high graphitic N content. In alkaline and acidic media, the N-PC-1000 shows not only decent catalytic activities in terms of onset potential and current density, but also has excellent tolerance to methanol poisoning effects and durability. This study provides worthy inspiration for using other environmental wastes to prepare related functional carbon materials with a variety of promising practical applications such as supercapacitors and lithium-ion batteries. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr00764c

  6. Bio-inspired nanocatalysts for the oxygen reduction reaction.

    PubMed

    Grumelli, Doris; Wurster, Benjamin; Stepanow, Sebastian; Kern, Klaus

    2013-01-01

    Electrochemical conversions at fuel cell electrodes are complex processes. In particular, the oxygen reduction reaction has substantial overpotential limiting the electrical power output efficiency. Effective and inexpensive catalytic interfaces are therefore essential for increased performance. Taking inspiration from enzymes, earth-abundant metal centres embedded in organic environments present remarkable catalytic active sites. Here we show that these enzyme-inspired centres can be effectively mimicked in two-dimensional metal-organic coordination networks self-assembled on electrode surfaces. Networks consisting of trimesic acid and bis-pyridyl-bispyrimidine coordinating to single iron and manganese atoms on Au(111) effectively catalyse the oxygen reduction and reveal distinctive catalytic activity in alkaline media. These results demonstrate the potential of surface-engineered metal-organic networks for electrocatalytic conversions. Specifically designed coordination complexes at surfaces inspired by enzyme cofactors represent a new class of nanocatalysts with promising applications in electrocatalysis.

  7. Bio-inspired nanocatalysts for the oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Grumelli, Doris; Wurster, Benjamin; Stepanow, Sebastian; Kern, Klaus

    2013-12-01

    Electrochemical conversions at fuel cell electrodes are complex processes. In particular, the oxygen reduction reaction has substantial overpotential limiting the electrical power output efficiency. Effective and inexpensive catalytic interfaces are therefore essential for increased performance. Taking inspiration from enzymes, earth-abundant metal centres embedded in organic environments present remarkable catalytic active sites. Here we show that these enzyme-inspired centres can be effectively mimicked in two-dimensional metal-organic coordination networks self-assembled on electrode surfaces. Networks consisting of trimesic acid and bis-pyridyl-bispyrimidine coordinating to single iron and manganese atoms on Au(111) effectively catalyse the oxygen reduction and reveal distinctive catalytic activity in alkaline media. These results demonstrate the potential of surface-engineered metal-organic networks for electrocatalytic conversions. Specifically designed coordination complexes at surfaces inspired by enzyme cofactors represent a new class of nanocatalysts with promising applications in electrocatalysis.

  8. Catalytic activity for oxygen reduction reaction on platinum-based core-shell nanoparticles: all-electron density functional theory.

    PubMed

    Shin, Jungho; Choi, Jung-Hae; Cha, Pil-Ryung; Kim, Seong Keun; Kim, Inho; Lee, Seung-Cheol; Jeong, Doo Seok

    2015-10-14

    Pt nanoparticles (NPs) in a proton exchange membrane fuel cell as a catalyst for an oxygen reduction reaction (ORR) fairly overbind oxygen and/or hydroxyl to their surfaces, causing a large overpotential and thus low catalytic activity. Realizing Pt-based core-shell NPs (CSNPs) is perhaps a workaround for the weak binding of oxygen and/or hydroxyl without a shortage of sufficient oxygen molecule dissociation on the surface. Towards the end, we theoretically examined the catalytic activity of NPs using density functional theory; each NP consists of one of 12 different 3d-5d transition metal cores (groups 8-11) and a Pt shell. The calculation results evidently suggest the enhancement of catalytic activity of CSNPs in particular when 3d transition metal cores are in use. The revealed trends in activity change upon the core metal were discussed with respect to the thermodynamic and electronic structural aspects of the NPs in comparison with the general d-band model. The disparity between the CSNP and the corresponding bilayer catalyst, which is the so-called size effect, was remarkable; therefore, it perhaps opens up the possibility of size-determined catalytic activity. Finally, the overpotential for all CSNPs was evaluated in an attempt to choose promising combinations of CSNP materials.

  9. Graphene oxide nanoplatforms to enhance catalytic performance of iron phthalocyanine for oxygen reduction reaction in bioelectrochemical systems

    NASA Astrophysics Data System (ADS)

    Costa de Oliveira, Maida Aysla; Mecheri, Barbara; D'Epifanio, Alessandra; Placidi, Ernesto; Arciprete, Fabrizio; Valentini, Federica; Perandini, Alessando; Valentini, Veronica; Licoccia, Silvia

    2017-07-01

    We report the development of electrocatalysts based on iron phthalocyanine (FePc) supported on graphene oxide (GO), obtained by electrochemical oxidation of graphite in aqueous solution of LiCl, LiClO4, and NaClO4. Structure, surface chemistry, morphology, and thermal stability of the prepared materials were investigated by Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, atomic force microscopy (AFM), thermogravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS). The catalytic activity toward oxygen reduction reaction (ORR) at neutral pH was evaluated by cyclic voltammetry. The experimental results demonstrate that the oxidation degree of GO supports affects the overall catalytic activity of FePc/GO, due to a modulation effect of the interaction between FePc and the basal plane of GO. On the basis of electrochemical, spectroscopic, and morphological investigations, FePc/GO_LiCl was selected to be assembled at the cathode side of a microbial fuel cell prototype, demonstrating a good electrochemical performance in terms of voltage and power generation.

  10. Synthesis and characterizations of Ni-NiO nanoparticles on PDDA-modified graphene for oxygen reduction reaction

    PubMed Central

    2014-01-01

    We are presenting our recent research results about the Ni-NiO nanoparticles on poly-(diallyldimethylammonium chloride)-modified graphene sheet (Ni-NiO/PDDA-G) nanocomposites prepared by the hydrothermal method at 90°C for 24 h. The Ni-NiO nanoparticles on PDDA-modified graphene sheets are measured by transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), and selected area electron diffraction (SAED) pattern for exploring the structural evidence to apply in the electrochemical catalysts. The size of Ni-NiO nanoparticles is around 5 nm based on TEM observations. The X-ray diffraction (XRD) results show the Ni in the (012), (110), (110), (200), and (220) crystalline orientations, respectively. Moreover, the crystalline peaks of NiO are found in (111) and (220). The thermal gravimetric analysis (TGA) result represents the loading content of the Ni metal which is about 34.82 wt%. The electron spectroscopy for chemical analysis/X-ray photoelectron spectroscopy (ESCA/XPS) reveals the Ni0 to NiII ratio in metal phase. The electrochemical studies with Ni-NiO/PDDA-G in 0.5 M aqueous H2SO4 were studied for oxygen reduction reaction (ORR). PMID:25246863

  11. Facile, scalable synthesis of edge-halogenated graphene nanoplatelets as efficient metal-free eletrocatalysts for oxygen reduction reaction

    PubMed Central

    Jeon, In-Yup; Choi, Hyun-Jung; Choi, Min; Seo, Jeong-Min; Jung, Sun-Min; Kim, Min-Jung; Zhang, Sheng; Zhang, Lipeng; Xia, Zhenhai; Dai, Liming; Park, Noejung; Baek, Jong-Beom

    2013-01-01

    A series of edge-selectively halogenated (X = Cl, Br, I) graphene nanoplatelets (XGnPs = ClGnP, BrGnP, IGnP) were prepared simply by ball-milling graphite in the presence of Cl2, Br2 and I2, respectively. High BET surface areas of 471, 579 and 662 m2/g were observed for ClGnP, BrGnP and IGnP, respectively, indicating a significant extent of delamination during the ball-milling and subsequent workup processes. The newly-developed XGnPs can be well dispersed in various solvents, and hence are solution processable. Furthermore, XGnPs showed remarkable electrocatalytic activities toward oxygen reduction reaction (ORR) with a high selectivity, good tolerance to methanol crossover/CO poisoning effects, and excellent long-term cycle stability. First-principle density-functional calculations revealed that halogenated graphene edges could provide decent adsorption sites for oxygen molecules, in a good agreement with the experimental observations. PMID:23736800

  12. Phase pure α-Mn2O3 prisms and their bifunctional electrocatalytic activity in oxygen evolution and reduction reactions.

    PubMed

    Jahan, Maryam; Tominaka, Satoshi; Henzie, Joel

    2016-11-22

    Synthesizing manganese oxide materials with exact control of the nanoparticle shape and phase is difficult, making it challenging to understand the influence of the surface structure on electrocatalysis. Here we describe an inexpensive, low-temperature method to synthesize single-crystal orthorhombic phase α-Mn2O3 prisms bound by the {100} facets. The synthesis is the first method to use the cation bridging effect to assist in the creation of α-Mn2O3 prisms. According to structural analysis using X-ray diffraction, X-ray pair-distribution function (PDF) measurements and high resolution transmission electron microscopy, the material is composed exclusively of α-Mn2O3 prisms, and no additional amorphous or nanocrystalline phases are present. Heating the prisms transformed the material to a more symmetrical, cubic phase α-Mn2O3 that exhibited strong bifunctional electrocatalytic activity for the oxygen evolution (OER) and oxygen reduction (ORR) reactions. We compared the oxygen electrode activities (OEA) and found that the α-Mn2O3 prisms performed 79% better than commercially-produced α-Mn2O3 powders, indicating that these α-Mn2O3 prisms perform well as inexpensive, earth-abundant materials for reversible electrodes.

  13. Platinum–nickel nanowire catalysts with composition-tunable alloying and faceting for the oxygen reduction reaction

    SciTech Connect

    Chang, Fangfang; Yu, Gang; Shan, Shiyao; Skeete, Zakiya; Wu, Jinfang; Luo, Jin; Ren, Yang; Petkov, Valeri; Zhong, Chuan-Jian

    2017-01-01

    The ability to tune the alloying properties and faceting characteristics of bimetallic nanocatalysts is essential for designing catalysts with enhanced activity and stability through optimizing strain and ligand effects, which is an important frontier for designing advanced materials as catalysts for fuel cell applications. This report describes composition-controlled alloying and faceting of platinum–nickel nanowires (PtNi NWs) for the electrocatalytic oxygen reduction reaction. The PtNi NWs are synthesized by a surfactant-free method and are shown to display bundled morphologies of nano-tetrahedra or nanowires, featuring an ultrathin and irregular helix morphology with composition-tunable facets. Using high-energy synchrotron X-ray diffraction coupled with atomic pair distribution function analysis, lattice expansion and shrinking are revealed, with the Pt : Ni ratio of ~3 : 2 exhibiting a clear expansion, which coincides with the maximum electrocatalytic activity for the ORR. In comparison with PtNi nanoparticles (NPs), the PtNi NWs display remarkably higher electrocatalytic activity and stability as a result of the composition dependent atomic-scale alloying and faceting, demonstrating a new pathway to the design of alloy nanocatalysts with enhanced activity and durability for fuel cells.

  14. Nitrogen-doped carbon nanotubes based on melamine-formaldehyde resin as highly efficient catalyst for oxygen reduction reaction.

    PubMed

    Zhang, Xin; Huang, Ying; Chen, Xuefang; Gao, Qiao; Zhang, Weichao

    2017-09-01

    The preparation of highly efficient and cheap electrocatalysts toward oxygen reduction reaction is significant for many electrochemical cells. Here we facilely synthesized nitrogen doped carbon nanotube by pyrolyzing melamine formaldehyde resin and Fe loading on MgO. There were mainly three morphologies observed, slender bamboo-like CNT, thick bamboo-like CNT, surface smooth, hollow CNT. The content of Fe loading on MgO had little influence on morphologies of CNT, however, when no MgO as support, only carbon ribbon obtained. The MgO as support was also significant for the formation of CNT. The samples with CNT formed represented better catalytic activity than control samples with no-CNT obtained, the morphology of CNT was beneficial for catalytic process. The sample C1-CNT with lowest content of Fe on support represented best catalytic activity which was competitive with 20% Pt/C in half-wave potential. The C1-CNT also showed outstanding stability and improved selectivity towards ORR, making it a promising alternative to Pt in application of fuel cells and metal-air batteries. Copyright © 2017 Elsevier Inc. All rights reserved.

  15. 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).

  16. Facile, scalable synthesis of edge-halogenated graphene nanoplatelets as efficient metal-free eletrocatalysts for oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Jeon, In-Yup; Choi, Hyun-Jung; Choi, Min; Seo, Jeong-Min; Jung, Sun-Min; Kim, Min-Jung; Zhang, Sheng; Zhang, Lipeng; Xia, Zhenhai; Dai, Liming; Park, Noejung; Baek, Jong-Beom

    2013-06-01

    A series of edge-selectively halogenated (X = Cl, Br, I) graphene nanoplatelets (XGnPs = ClGnP, BrGnP, IGnP) were prepared simply by ball-milling graphite in the presence of Cl2, Br2 and I2, respectively. High BET surface areas of 471, 579 and 662 m2/g were observed for ClGnP, BrGnP and IGnP, respectively, indicating a significant extent of delamination during the ball-milling and subsequent workup processes. The newly-developed XGnPs can be well dispersed in various solvents, and hence are solution processable. Furthermore, XGnPs showed remarkable electrocatalytic activities toward oxygen reduction reaction (ORR) with a high selectivity, good tolerance to methanol crossover/CO poisoning effects, and excellent long-term cycle stability. First-principle density-functional calculations revealed that halogenated graphene edges could provide decent adsorption sites for oxygen molecules, in a good agreement with the experimental observations.

  17. Activity of Co-N multi walled carbon nanotubes electrocatalysts for oxygen reduction reaction in acid conditions

    NASA Astrophysics Data System (ADS)

    Osmieri, Luigi; Monteverde Videla, Alessandro H. A.; Specchia, Stefania

    2015-03-01

    Two catalysts are synthesized by wet impregnation of multi walled carbon nanotubes (MWCNT) with a complex formed between Co(II) ions and the nitrogen-containing molecule 2,4,6-tris(2-pyridyl)-1,3,5-triazine (TPTZ), followed by one or two identical heat treatments in N2 atmosphere at 800 °C for 3 h. Catalysts are fully characterized by FESEM, EDX, BET, XRD, FTIR, TGA, XPS analyses, and electrochemical techniques. The electrocatalytic activity towards oxygen reduction reaction (ORR) of the catalysts in acid conditions is assessed by means of a rotating disk electrode (RDE) apparatus and a specific type of cell equipped with a gas diffusion working electrode (GDE). In both testing approaches, the catalyst heat-treated twice (Co-N/MWCNT-2) exhibits higher electroactivity than the catalyst heat-treated once (Co-N/MWCNT-1). Chronoamperometries both in RDE and GDE cell are also performed, showing less electroactivity decay and better current performance for the catalyst heat-treated twice.

  18. Nitrogen-doped hierarchically porous carbon spheres as efficient metal-free electrocatalysts for an oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Liu, You-Lin; Shi, Cheng-Xiang; Xu, Xue-Yan; Sun, Ping-Chuan; Chen, Tie-Hong

    2015-06-01

    Using hierarchically mesoporous silica spheres as a hard template and methyl violet as carbon and nitrogen source, nitrogen-doped hierarchically porous carbon spheres (N-HCS) are successfully prepared via a nanocasting method. The nitrogen-doped carbon spheres obtained after carbonization at 1000 °C (N-HCS-1000) exhibit a hierarchically micro-meso-macroporous structure with a relatively high surface area (BET) of 1413 m2 g-1 and a notably large pore volume of 2.96 cm3 g-1. In an oxygen reduction reaction (ORR) in alkaline media, the N-HCS-1000 material exhibits excellent activity with high current density, and its onset potential is notably close to that of the commercial Pt/C catalyst. The efficient catalytic activity of this catalyst could be attributed to the high electrical conductivity of the nitrogen-doped carbon matrix as well as the hierarchically porous framework. This catalyst also exhibits better methanol crossover resistance and higher stability than the commercial Pt/C catalyst.

  19. In situ synchrotron x-ray spectroscopy of ruthenium nanoparticles modified with selenium for an oxygen reduction reaction.

    SciTech Connect

    Inukai, J.; Cao, D.; Wieckowski, A.; Chang, K.-C.; Menzel, A.; Komanicky, V.; You, H.; Univ. Illinois; Univ. Yamanashi

    2007-11-15

    We used in situ Se K-edge X-ray spectroscopy to characterize Ru nanoparticles chemically modified with submonolayers of selenium (Se/Ru) [Cao et al. J. Electrochem. Soc. 2006, 153, A869]. X-ray powder diffraction verified that the Se/Ru catalyst had metallic Ru cores. The in situ X-ray absorption near edge structure taken at the open circuit potential showed that there were both elemental and oxidized selenium on the as-prepared Se/Ru samples. All selenium oxide was reduced to the elemental form of selenium by applying negative potentials. By applying positive potentials, selenium was subsequently reoxidized. The analysis of the extended X-ray absorption fine structure shows the appearance of selenium hydration (Se-OH{sub 2}) in a deaerated solution, which was not observed during the oxygen reduction reaction. We present evidence that Se-free Ru atoms play an important role in the ORR activity of the Se/Ru catalyst studied in this paper.

  20. In-situ synchrotron x-ray spectroscopy of ruthenium nanoparticles modified with selenium for oxygen reduction reaction.

    SciTech Connect

    Inukai, J.; Cao, D.; Wieckowski, A.; Chang, K.-C.; Menzel, A.; Komanicky, V.; You, H.; Materials Science Division; Univ. of Illinois; Univ. of Yamanashi

    2007-11-15

    We used in situ Se K-edge X-ray spectroscopy to characterize Ru nanoparticles chemically modified with submonolayers of selenium (Se/Ru) [Cao et al. J. Electrochem. Soc. 2006, 153, A869]. X-ray powder diffraction verified that the Se/Ru catalyst had metallic Ru cores. The in situ X-ray absorption near edge structure taken at the open circuit potential showed that there were both elemental and oxidized selenium on the as-prepared Se/Ru samples. All selenium oxide was reduced to the elemental form of selenium by applying negative potentials. By applying positive potentials, selenium was subsequently reoxidized. The analysis of the extended X-ray absorption fine structure shows the appearance of selenium hydration (Se-OH{sub 2}) in a deaerated solution, which was not observed during the oxygen reduction reaction. We present evidence that Se-free Ru atoms play an important role in the ORR activity of the Se/Ru catalyst studied in this paper.

  1. Diversity of Contaminant Reduction Reactions by Zero-Valent Iron: Role of the Reductate

    SciTech Connect

    Miehr, R; Tratnyek, Paul G.; Bandstra, J; Scherer, Michelle; Alowitz, M; Bylaska, Eric J.

    2004-01-01

    The reactions of 8 model contaminants with 9 types of granular Fe(0) were studied in batch experiments using consistent experimental conditions. The model contaminants (herein referred to as reductates because they were reduced by the iron metal) included cations (Cu2+), anions (CrO42-; NO3-; and 5,5,7,7-indigotetrasulfonate), and neutral species (2-chloroacetophenone; 2,4,6-trinitrotoluene; carbon tetrachloride; and trichloroethene). The diversity of this range of reductates offers a uniquely broad perspective on the reactivity of Fe(0). Rate constants for disappearance of the reductates vary over as much as 4 orders of magnitude for particular reductates (due to differences in the 9 types of iron) but differences among the reductates were even larger, ranging over almost 7 orders of magnitude. Various ways of summarizing the data all suggest that relative reactivities with Fe(0) varies in the order: Cu2, I4S > 2CAP, TNT > CT, Cr6 > TCE > NO3. Although the reductate h as the largest effect on disappearance kinetics, more subtle differences in reactivity due to the type of Fe(0) suggests that removal of Cr6 and NO3 (the inorganic anions) involves adsorption to oxides on the Fe(0), whereas the disappearance kinetics of all other types of reductants is favored by reduction on comparatively oxide-free metal. Correlation analysis of the disappearance rate constants using descriptors of the reductates calculated by molecular modeling (energies of the lowest unoccupied molecular orbitals, LUMO, highest occupied molecular orbitals, HOMO, and HOMO-LUMO gaps) showed that reactivities generally increase with decreasing ELUMO and increasing EGAP (and, therefore, increasing chemical hardness h).

  2. Earth-Abundant Nanomaterials for Oxygen Reduction.

    PubMed

    Xia, Wei; Mahmood, Asif; Liang, Zibin; Zou, Ruqiang; Guo, Shaojun

    2016-02-18

    Replacing the rare and precious platinum (Pt) electrocatalysts with earth-abundant materials for promoting the oxygen reduction reaction (ORR) at the cathode of fuel cells is of great interest in developing high-performance sustainable energy devices. However, the challenging issues associated with non-Pt materials are still their low intrinsic catalytic activity, limited active sites, and the poor mass transport properties. Recent advances in material sciences and nanotechnology enable rational design of new earth-abundant materials with optimized composition and fine nanostructure, providing new opportunities for enhancing ORR performance at the molecular level. This Review highlights recent breakthroughs in engineering nanocatalysts based on the earth-abundant materials for boosting ORR. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Nitrogen-doped graphene anchored with mixed growth patterns of CuPt alloy nanoparticles as a highly efficient and durable electrocatalyst for the oxygen reduction reaction in an alkaline medium.

    PubMed

    Illathvalappil, Rajith; Dhavale, Vishal M; Bhange, Siddheshwar N; Kurungot, Sreekumar

    2017-07-06

    A highly active and durable CuPt alloy catalyst with trigonal bipyramidal and truncated cube-type mixed morphologies, anchored on the nitrogen-doped graphene (NGr) surface (CuPt-TBTC/NGr), was prepared by a simple and fast method. The obtained CuPt alloy showed improved oxygen reduction reaction (ORR) activity, with a 30 mV positive shift in the half-wave potential value, as compared to the state-of-the-art Pt/C catalyst in a 0.1 M KOH solution. The CuPt alloy with the trigonal bipyramidal morphology possesses porous type inter-connected sides, which help to achieve improved mass transport of oxygen during the ORR. The exposure of the (111) plane of the CuPt alloy further improved the catalytic activity towards the dioxygen reduction in alkaline media. The ORR activity of the NGr-supported CuPt alloy was found to be dependent on the reaction time, and improved activity was obtained on the material derived at a reaction time of 90 min (CuPt-TBTC/NGr-90). The material synthesized at a lower or higher reaction time than 90 min resulted in a partially formed trigonal bipyramidal morphology with more truncated cubes or agglomerated trigonal bipyramidal and truncated cubes with closed type structures, respectively. Along with the high intrinsic ORR activity, CuPt-TBTC/NGr-90 displayed excellent electrochemical stability. Even after repeated 1000 potential cycling in a window ranging from 0.10 to 1.0 V (vs. RHE), the system clearly outperformed the state-of-the-art Pt/C catalyst with 15 and 60 mV positive shifts in the onset and half-wave potentials, respectively. CuPt-TBTC/NGr-90 also exhibited 2.1 times higher mass activity and 2.2 times higher specific activity, compared to Pt/C at 0.90 V (vs. RHE). Finally, a zinc-air battery fabricated with the alloy catalyst as the air electrode displayed a peak power density of 300 mW cm(-2), which is much higher than the peak power density of 253 mW cm(-2) obtained for the state-of-the-art Pt/C catalyst as the air electrode.

  4. Reduction of dynamical biochemical reactions networks in computational biology

    PubMed Central

    Radulescu, O.; Gorban, A. N.; Zinovyev, A.; Noel, V.

    2012-01-01

    Biochemical networks are used in computational biology, to model mechanistic details of systems involved in cell signaling, metabolism, and regulation of gene expression. Parametric and structural uncertainty, as well as combinatorial explosion are strong obstacles against analyzing the dynamics of large models of this type. Multiscaleness, an important property of these networks, can be used to get past some of these obstacles. Networks with many well separated time scales, can be reduced to simpler models, in a way that depends only on the orders of magnitude and not on the exact values of the kinetic parameters. The main idea used for such robust simplifications of networks is the concept of dominance among model elements, allowing hierarchical organization of these elements according to their effects on the network dynamics. This concept finds a natural formulation in tropical geometry. We revisit, in the light of these new ideas, the main approaches to model reduction of reaction networks, such as quasi-steady state (QSS) and quasi-equilibrium approximations (QE), and provide practical recipes for model reduction of linear and non-linear networks. We also discuss the application of model reduction to the problem of parameter identification, via backward pruning machine learning techniques. PMID:22833754

  5. Double layer effects in electrocatalysis: The oxygen reduction reaction and ethanol oxidation reaction on Au(111), Pt(111) and Ir(111) in alkaline media containing Na and Li cations

    DOE PAGES

    Lopes, Pietro P.; Strmcnik, Dusan; Jirkovsky, Jakub S.; ...

    2015-09-28

    Oxygen reduction and ethanol oxidation reactions were studied on Au(111), Pt(111) and Ir(111) in alkaline solutions containing sodium and/or lithium cations. By keeping the same (111) surface orientation and exploring oxophilicity trends and non-covalent interactions between OHad and alkali metal cations (AMCn+), we were able to gain deep insights into the multiple roles that OHad plays in these important electrocatalytic reactions. Cyclic voltammetry experiments revealed that OHad formation initiates at distinct electrode potentials, governed by the oxophilicity of the specific metal surface, with further OHad adlayer stabilization by non-covalent alkali-cation interactions and affecting the formation of a “true oxide” layermore » at higher electrode potentials. Although OHad is a simple spectator for the ORR, it promotes the ethanol oxidation reaction (EOR) at lower potentials and act as spectator at high OHad coverages. By changing the alkali metal cation at the interface (Li+) on more oxophilic surfaces, it was possible to promote the EOR even more, relative to Na+, without changing the product distribution for the reaction. This cation effect suggests that OHad—Li+(H2O)x clusters can stabilize the ethoxide adlayer, thus improving the EOR activity. Finally, our results indicate the importance of the entire electrochemical interface in determining the electrocatalytic activity during reaction.« less

  6. Double layer effects in electrocatalysis: the oxygen reduction reaction and ethanol oxidation reaction on Au(111), Pt(111) and Ir(111) in alkaline media containing Na and Li cations.

    SciTech Connect

    Lopes, Pietro P.; Strmcnik, Dusan; Jirkovsky, Jakub S.; Connell, Justin G.; Stamenkovic, Vojislav; Markovic, Nenad

    2016-03-15

    Oxygen reduction and ethanol oxidation reactions were studied on Au(111), Pt(111) and Ir(111) in alkaline solutions containing sodium and/or lithium cations. By keeping the same (111) surface orientation and exploring oxophilicity trends and non-covalent interactions between OHad and alkali metal cations (AMCn+), we were able to gain deep insights into the multiple roles that OHad plays in these important electrocatalytic reactions. Cyclic voltammetry experiments revealed that OHad formation initiates at distinct electrode potentials, governed by the oxophilicity of the specific metal surface, with further OHad adlayer stabilization by non-covalent alkali-cation interactions and affecting the formation of a “true oxide” layer at higher electrode potentials. Although OHad is a simple spectator for the ORR, it promotes the ethanol oxidation reaction (EOR) at lower potentials and act as spectator at high OHad coverages. By changing the alkali metal cation at the interface (Li+) on more oxophilic surfaces, it was possible to promote the EOR even more, relative to Na+, without changing the product distribution for the reaction. This cation effect suggests that OHad---Li+(H2O)x clusters can stabilize the ethoxide adlayer, thus improving the EOR activity. Our results indicate the importance of the entire electrochemical interface in determining the electrocatalytic activity during reaction.

  7. Co3O4@Co/NCNT Nanostructure Derived from a Dicyanamide Based Metal-Organic Framework as Efficient Bi-functional Electrocatalyst for Oxygen Reduction and Evolution Reactions.

    PubMed

    Sikdar, Nivedita; Konkena, Bharathi; Masa, Justus; Schuhmann, Wolfgang; Maji, Tapas Kumar

    2017-09-15

    There has been growing interest in the synthesis of efficient reversible oxygen electrodes for both the oxygen reduction reaction (ORR) and the oxygen evolution reactions (OER) for their potential use in a variety of renewable energy technologies such as regenerative fuel cells and metal-air batteries. Here, we report a bi-functional electrocatalyst derived from a novel dicyanamide based nitrogen rich MOF {[Co(bpe)2(N(CN)2)](N(CN)2)(5H2O)}n [Co-MOF-1, bpe = 1,2-bis(4-pyridyl)ethane, N(CN)2- = dicyanamide] under different pyrolysis conditions. Pyrolysis of the Co-MOF-1 under Ar atmosphere (at 800 C) yielded a Co nanoparticles embedded N-doped carbon nanotube matrix (Co/NCNT-Ar) while pyrolysis under a reductive H2/Ar atmosphere (at 800 C) and further mild calcination yielded Co3O4@Co core-shell nanoparticles encapsulated N-doped carbon nanotubes (Co3O4@Co/NCNT). Both catalysts show bi-functional activity towards ORR and OER, however, the core-shell Co3O4@Co/NCNT nanostructure exhibited superior electrocatalytic activity for both the ORR with a potential of 0.88 V at a current density of -1 mA cm-2 and the OER with a potential of 1.61 V at 10 mA cm-2, which is competitive with the most active bi-functional catalysts reported previously. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Enhanced electrocatalytic activity and stability of Pd3V/C nanoparticles with a trace amount of Pt decoration for the oxygen reduction reaction

    DOE PAGES

    Liu, Sufen; Han, Lili; Zhu, Jing; ...

    2015-09-14

    In this study, carbon supported Pd3V bimetallic alloy nanoparticles (Pd3V/C) have been successfully synthesized via a simple impregnation–reduction method, followed by high temperature treatment under a H2 atmosphere. Electrochemical tests reveal that the half-wave potential of Pd3V/C-500 shifts positively 40 mV compared with Pd/C. However, the catalytic activity of Pd3V/C-500 suffers from serious degradation after 1k cycles. By a spontaneous displacement reaction or co-reduction method, a trace amount of Pt was decorated on the surface or inside of the Pd3V/C nanoparticles. The catalytic activity and stability of the Pd3V@Pt/C and Pt-Pd3V/C catalysts for the oxygen reduction reaction (ORR) are enhancedmore » significantly, and are comparable to commercial Pt/C. In addition, the Pt mass activity of Pd3V@Pt/C and Pt-Pd3V/C improves by factors of 10.9 and 6.5 at 0.80 V relative to Pt/C. Moreover, Pt-decorated Pd3V/C nanoparticles show almost no obvious morphology change after durability tests, because the Pt-rich shell plays an important role in preventing degradation.« less

  9. Comparative study of oxygen reduction reaction on Ru xM ySe z (M = Cr, Mo, W) electrocatalysts for polymer exchange membrane fuel cell

    NASA Astrophysics Data System (ADS)

    Suárez-Alcántara, K.; Solorza-Feria, O.

    Electrochemical evaluation of the Ru xM ySe z (M = Cr, Mo, W) type electrocatalysts towards the oxygen reduction reaction (ORR) is presented. The electrocatalysts were synthesized by reacting the corresponding transition metal carbonyl compounds and elemental selenium in 1,6-hexanediol under refluxing conditions for 3 h. The powder electrocatalysts were characterized by scanning electron microscopy (SEM), and X-ray diffraction (XRD). Results indicate the formation of agglomerates of crystalline particles with nanometric size embedded in an amorphous phase. The particle size decreased according to the following trend: Ru xCr ySe z > Ru xW ySe z > Ru xMo ySe z. Electrochemical studies were performed by rotating disk electrode (RDE) and rotating ring-disk electrode (RRDE) techniques. Kinetic parameters exhibited Tafel slopes of 120 mV dec -1; exchange current density of around 1 × 10 -5 mA cm -2 and apparent activation energies between 40 and 55 kJ mol -1. A four-electron reduction was found in all three cases. The catalytic activity towards the ORR decreases according to the following trend: Ru xMo ySe z > Ru xW ySe z > Ru xCr ySe z. However this trend was not maintained when the materials were tested as cathode electrodes in a single polymer exchange membrane fuel cell, PEMFC. The Ru xW ySe z electrocatalyst showed poor activity compared to Ru xMo ySe z and Ru xCr ySe z which were considered suitable candidates to be used as cathode in PEMFCs.

  10. Planning and conduct of operational readiness reviews (ORR)

    SciTech Connect

    Not Available

    1993-11-01

    The purpose of this Standard is to establish a uniform process for when an ORR (1) of a new nuclear facility is to be started, (2) a previously operated facility is to be restarted, or (3) any new operating phase that results in a significant increase in existing hazards, or could introduce significant hazards not previously encountered is planned. This Standard describes a method to verify that the facility is physically ready to startup, that the managers and operators are prepared to manage and operate the facility in the proposed phase, and that the necessary infrastructure are in place. It also provides a methodology for determining the breadth and depth of the ORR so as to be consistent with the hazards and complexity of the proposed facility transition. This Standard provides procedures for the conduct of an ORR when required by the circumstances of the startup as specified in DOE 5480.31. The Standard also discusses principles and criteria for Readiness Assessments incident to the facility startup process when an ORR in not required.

  11. Ion-exchanged route synthesis of Fe2N-N-doped graphitic nanocarbons composite as advanced oxygen reduction electrocatalyst.

    PubMed

    Wang, Lei; Yin, Jie; Zhao, Lu; Tian, Chungui; Yu, Peng; Wang, Jianqiang; Fu, Honggang

    2013-04-14

    Fe2N nanoparticles and nitrogen-doped graphitic nanosheet composites (Fe2N-NGC) have been synthesized by an ion-exchanged route, which can serve as an efficient non-precious metal electrocatalyst with a 4e(-) reaction pathway for oxygen reduction reactions (ORR).

  12. Activation of oxygen evolving perovskites for oxygen reduction by functionalization with Fe-N(x)/C groups.

    PubMed

    Rincón, Rosalba A; Masa, Justus; Mehrpour, Sara; Tietz, Frank; Schuhmann, Wolfgang

    2014-12-07

    The incorporation of Fe-Nx/C moieties into perovskites remarkably activates them for the oxygen reduction reaction (ORR) and also leads to notable improvement of their activity towards the oxygen evolution reaction (OER) thus presenting a new route for realizing high performance, low cost bifunctional catalysts for reversible oxygen electrodes.

  13. S-Doping of an Fe/N/C ORR Catalyst for Polymer Electrolyte Membrane Fuel Cells with High Power Density.

    PubMed

    Wang, Yu-Cheng; Lai, Yu-Jiao; Song, Lin; Zhou, Zhi-You; Liu, Jian-Guo; Wang, Qiang; Yang, Xiao-Dong; Chen, Chi; Shi, Wei; Zheng, Yan-Ping; Rauf, Muhammad; Sun, Shi-Gang

    2015-08-17

    Fe/N/C is a promising non-Pt electrocatalyst for the oxygen reduction reaction (ORR), but its catalytic activity is considerably inferior to that of Pt in acidic medium, the environment of polymer electrolyte membrane fuel cells (PEMFCs). An improved Fe/N/C catalyst (denoted as Fe/N/C-SCN) derived from Fe(SCN)3, poly-m-phenylenediamine, and carbon black is presented. The advantage of using Fe(SCN)3 as iron source is that the obtained catalyst has a high level of S doping and high surface area, and thus exhibits excellent ORR activity (23 A g(-1) at 0.80 V) in 0.1 M H2SO4 solution. When the Fe/N/C-SCN was applied in a PEMFC as cathode catalyst, the maximal power density could exceed 1 W cm(-2). © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Evaluation of oxygen reduction activity by the thin-film rotating disk electrode methodology: The effects of potentiodynamic parameters

    DOE PAGES

    Chen, Guangyu; Li, Meng; Kuttiyiel, Kurian A.; ...

    2016-04-11

    Here, an accurate and efficient assessment of activity is critical for the research and development of electrocatalysts for oxygen reduction reaction (ORR). Currently, the methodology combining the thin-film rotating disk electrode (TF-RDE) and potentiodynamic polarization is the most commonly used to pre-evaluate ORR activity, acquire kinetic data (i.e., kinetic current, Tafel slope, etc.), and gain understanding of the ORR mechanism. However, it is often neglected that appropriate potentiodynamic parameters have to be chosen to obtain reliable results. We first evaluate the potentiodynamic and potentiostatic polarization measurements with TF-RDE to examine the ORR activity of Pt nanoelectrocatalyst. Furthermore, our results demonstratemore » that besides depending on the nature of electrocatalyst, the apparent ORR kinetics also strongly depends on the associated potentiodynamic parameters, such as scan rate and scan region, which have a great effect on the coverage of adsorbed OHad/Oad on Pt surface, thereby affecting the ORR activities of both nanosized and bulk Pt. However, the apparent Tafel slopes remained nearly the same, indicating that the ORR mechanism in all the measurements was not affected by different potentiodynamic parameters.« less

  15. Evaluation of oxygen reduction activity by the thin-film rotating disk electrode methodology: The effects of potentiodynamic parameters

    SciTech Connect

    Chen, Guangyu; Li, Meng; Kuttiyiel, Kurian A.; Sasaki, Kotaro; Kong, Fanpeng; Du, Chunyu; Gao, Yunzhi; Yin, Geping; Adzic, Radoslav R.

    2016-04-11

    Here, an accurate and efficient assessment of activity is critical for the research and development of electrocatalysts for oxygen reduction reaction (ORR). Currently, the methodology combining the thin-film rotating disk electrode (TF-RDE) and potentiodynamic polarization is the most commonly used to pre-evaluate ORR activity, acquire kinetic data (i.e., kinetic current, Tafel slope, etc.), and gain understanding of the ORR mechanism. However, it is often neglected that appropriate potentiodynamic parameters have to be chosen to obtain reliable results. We first evaluate the potentiodynamic and potentiostatic polarization measurements with TF-RDE to examine the ORR activity of Pt nanoelectrocatalyst. Furthermore, our results demonstrate that besides depending on the nature of electrocatalyst, the apparent ORR kinetics also strongly depends on the associated potentiodynamic parameters, such as scan rate and scan region, which have a great effect on the coverage of adsorbed OHad/Oad on Pt surface, thereby affecting the ORR activities of both nanosized and bulk Pt. However, the apparent Tafel slopes remained nearly the same, indicating that the ORR mechanism in all the measurements was not affected by different potentiodynamic parameters.

  16. Evaluation of oxygen reduction activity by the thin-film rotating disk electrode methodology: The effects of potentiodynamic parameters

    SciTech Connect

    Chen, Guangyu; Li, Meng; Kuttiyiel, Kurian A.; Sasaki, Kotaro; Kong, Fanpeng; Du, Chunyu; Gao, Yunzhi; Yin, Geping; Adzic, Radoslav R.

    2016-04-11

    Here, an accurate and efficient assessment of activity is critical for the research and development of electrocatalysts for oxygen reduction reaction (ORR). Currently, the methodology combining the thin-film rotating disk electrode (TF-RDE) and potentiodynamic polarization is the most commonly used to pre-evaluate ORR activity, acquire kinetic data (i.e., kinetic current, Tafel slope, etc.), and gain understanding of the ORR mechanism. However, it is often neglected that appropriate potentiodynamic parameters have to be chosen to obtain reliable results. We first evaluate the potentiodynamic and potentiostatic polarization measurements with TF-RDE to examine the ORR activity of Pt nanoelectrocatalyst. Furthermore, our results demonstrate that besides depending on the nature of electrocatalyst, the apparent ORR kinetics also strongly depends on the associated potentiodynamic parameters, such as scan rate and scan region, which have a great effect on the coverage of adsorbed OHad/Oad on Pt surface, thereby affecting the ORR activities of both nanosized and bulk Pt. However, the apparent Tafel slopes remained nearly the same, indicating that the ORR mechanism in all the measurements was not affected by different potentiodynamic parameters.

  17. Green, Seed-Mediated Synthesis of Au Nanowires and Their Efficient Electrocatalytic Activity in Oxygen Reduction Reaction.

    PubMed

    Balasubramanian, Sathiya; Sheelam, Anjaiah; Ramanujam, Kothandaraman; Dhamodharan, Raghavachari

    2017-08-30

    A new, simple, green method for the synthesis of Au nanowires (average diameter 8 nm and several micrometers in length) using Au seeds prepared from bael gum (BG) is reported. The nanowires are characterized using UV-visible absorption spectroscopy, powder X-ray diffraction, transmission electron microscopy (TEM), and high-resolution-TEM. It is observed that the rate of the reduction process might be the decisive factor for the shape selectivity, as evident from the formation of nanowires at a particular concentration of seeds and NaOH. The polysaccharide present in BG is the active ingredient for the synthesis of Au nanowires, while the small molecules present in BG, when used alone, did not result in nanowire formation. The TEM images of the precursor to the Au nanowires suggested that new, nucleated particles align in a linear manner and fuse with one another, resulting in the nanowire. The linear fusion of the newly nucleated particles could be due to the lack of adequate protecting agent and the presence of Au complex adsorbed to the surface. The electrochemical activity of the nanowires for oxygen reduction reaction (ORR) is assessed and compared with that of nanotriangles and spherical nanoparticles of Au. The performance of Au nanowire is better than Au-nanomaterials (heat-treated as well as non-heat-treated), Au seeds, and clusters. The better efficiency of the nanowires when compared to that of the other reported catalysts is attributed to the presence of active (100) facets with numerous corners, edges, and surface defects.

  18. Pt@Pd(x)Cu(y)/C core-shell electrocatalysts for oxygen reduction reaction in fuel cells.

    PubMed

    Cochell, T; Manthiram, A

    2012-01-17

    A series of carbon-supported core-shell nanoparticles with Pd(x)Cu(y)-rich cores and Pt-rich shells (Pt@Pd(x)Cu(y)/C) has been synthesized by a polyol reduction of the precursors followed by heat treatment to obtain the Pd(x)Cu(y)/C (1 ≤ x ≤ 3 and 0 ≤ y ≤ 5) cores and the galvanic displacement of Pd(x)Cu(y) with [PtCl(4)](2-) to form the Pt shell. The nanoparticles have also been investigated with respect to the oxygen reduction reaction (ORR) in proton-exchange-membrane fuel cells (PEMFCs). X-ray diffraction (XRD) analysis suggests that the cores are highly alloyed and that the galvanic displacement results in a certain amount of alloying between Pt and the underlying Pd(x)Cu(y) alloy core. Transmission electron microscopy (TEM) images show that the Pt@Pd(x)Cu(y)/C catalysts (where y > 0) have mean particle sizes of <8 nm. Compositional analysis by energy-dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) clearly shows Pt enrichment in the near-surface region of the nanoparticles. Cyclic voltammograms show a positive shift of as much as 40 mV for the onset of Pt-OH formation in the Pt@Pd(x)Cu(y)/C electrocatalysts compared to that in Pt/C. Rotating disk electrode (RDE) measurements of Pt@PdCu(5)/C show an increase in the Pt mass activity by 3.5-fold and noble metal activity by 2.5-fold compared to that of Pt/C. The activity enhancements in RDE and PEMFC measurements are believed to be a result of the delay in the onset of Pt-OH formation. © 2011 American Chemical Society

  19. One-pot electrodeposition of cobalt flower-decorated silver nanotrees for oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Cho, Yun-Bin; Moon, Sinyoung; Lee, Chongmok; Lee, Youngmi

    2017-02-01

    In this paper, we demonstrate a simple fabrication of bimetallic silver (Ag) and cobalt (Co) nanostructures (AgCo) with various Ag to Co relative contents via electrochemical co-deposition. A series of AgCo catalysts was electrodeposited on glassy carbon (GC) electrodes at -0.57 V vs. SCE in the deposition solutions, containing Ag precursor, Co precursor, Triton X-100, and 0.3 M KNO3 aqueous solution, with various Ag to Co precursor concentration ratios (1:x, x was varied from 3 to 11). The films, deposited with the total deposition charge of 0.042C, were denoted as Ag1Cox. SEM and TEM analyses showed that Ag1Cox formed a structure consisted of flower-like Co grown on tree-like Ag backbones while it had more Co flowers with a greater x. The ORR activities were examined in 0.1 M NaOH solution with rotating disk electrode (RDE) voltammetry and Ag1Co7 showed the best catalytic activity. The co-deposition mechanism was further investigated by varying the deposition time of Ag1Co7. At the early stage of deposition, Ag-tree branches were formed predominantly, followed by the growth of flower-like Co nanostructures on the Ag nanotrees: More Co flowers were produced on Ag backbones with longer deposition time, being attributed to both a less negative reduction potential of Ag+ to Ag than Co2+ to Co and promoted Co2+ reduction on the initially formed Ag surface. Ag1Co7 electrodeposited for 200 s, consisted of ∼14% Co, showed the greatest ORR catalytic activity which was better or comparable to noble metal Pt.

  20. Controlled synthesis of La{sub 1−x}Sr{sub x}CrO{sub 3} nanoparticles by hydrothermal method with nonionic surfactant and their ORR activity in alkaline medium

    SciTech Connect

    Choi, Bo Hyun; Park, Shin-Ae; Park, Bong Kyu; Chun, Ho Hwan; Kim, Yong-Tae

    2013-10-15

    Graphical abstract: We demonstrate that Sr-doped LaCrO{sub 3} nanoparticles were successfully prepared by the hydrothermal synthesis method using the nonionic surfactant Triton X-100 and the applicability of La{sub 1−x}Sr{sub x}CrO{sub 3} to oxygen reduction reaction (ORR) electrocatalysis in an alkaline medium. Compared with the nanoparticles synthesized by the coprecipitation method, they showed enhanced ORR activity. - Highlights: • Sr-doped LaCrO{sub 3} nanoparticles were successfully prepared by the hydrothermal method using the nonionic surfactant. • Homogeneously shaped and sized Sr-doped LaCrO{sub 3} nanoparticles were readily obtained. • Compared with the nanoparticles synthesized by the coprecipitation method, they showed an enhanced ORR activity. • The main origin was revealed to be the decreased particle size due to the nonionic surfactant. - Abstract: Sr-doped LaCrO{sub 3} nanoparticles were prepared by the hydrothermal method with the nonionic surfactant Triton X-100 followed by heat treatment at 1000 °C for 10 h. The obtained perovskite nanoparticles had smaller particle size (about 100 nm) and more uniform size distribution than those synthesized by the conventional coprecipitation method. On the other hand, it was identified with the material simulation that the electronic structure change by Sr doping was negligible, because the initially unfilled e{sub g}-band was not affected by the p-type doping. Finally, the perovskite nanoparticles synthesized by hydrothermal method showed much higher ORR activity by over 200% at 0.8 V vs. RHE than those by coprecipitation method.

  1. Phosphorus/sulfur Co-doped porous carbon with enhanced specific capacitance for supercapacitor and improved catalytic activity for oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Zhou, Yao; Ma, Ruguang; Candelaria, Stephanie L.; Wang, Jiacheng; Liu, Qian; Uchaker, Evan; Li, Pengxi; Chen, Yongfang; Cao, Guozhong

    2016-05-01

    Phosphorus (P)/sulfur (S) co-doped porous carbon derived from resorcinol and furaldehyde are synthesized through one-step sol-gel processing with the addition of phosphorus pentasulfide as P and S source followed with freeze-drying and pyrolysis in nitrogen. The P/S co-doping strategy facilitates the pore size widening both in micropore and mesopore regions, together with the positive effect on the degree of graphitization of porous carbon through elimination of amorphous carbon through the formation and evaporation of carbon disulfide. As an electrode for supercapacitor application, P/S co-doped porous carbon demonstrates 43.5% improvement on specific capacitance of the single electrode compared to pristine porous carbon in organic electrolyte at a current of 0.5 mA due to the P-induced pseudocapacitive reactions. As for electrocatalytic use, promoted electrocatalytic activity and high resistance to crossover effects of oxygen reduction reaction (ORR) in alkaline media are observed after the introduction of P and S into porous carbon. After air activation, the specific capacitance of the single electrode of sample PS-pC reaches up to 103.5 F g-1 and an improved oxygen reduction current density.

  2. Synergy of Cobalt and Silver Microparticles Electrodeposited on Glassy Carbon for the Electrocatalysis of the Oxygen Reduction Reaction: An Electrochemical Investigation.

    PubMed

    Zafferoni, Claudio; Cioncoloni, Giacomo; Foresti, Maria Luisa; Dei, Luigi; Carretti, Emiliano; Vizza, Francesco; Lavacchi, Alessandro; Innocenti, Massimo

    2015-08-07

    The combination of two different metals, each of them acting on different steps of the oxygen reduction reaction (ORR), yields synergic catalytic effects. In this respect, the electrocatalytic effect of silver is enhanced by the addition of cobalt, which is able to break the O-O bond of molecular oxygen, thus accelerating the first step of the reduction mechanism. At the same time, research is to further reduce the catalyst's cost, reducing the amount of Ag, which, even though being much less expensive than Pt, is still a noble metal. From this point of view, using a small amount of Ag together with an inexpensive material, such as graphite, represents a good compromise. The aim of this work was to verify if the synergic effects are still operating when very small amounts of cobalt (2-10 μg·cm(-2)) are added to the microparticles of silver electrodeposited on glassy carbon, described in a preceding paper from us. To better stress the different behaviour observed when cobalt and silver are contemporarily present in the deposit, the catalytic properties of cobalt alone were investigated. The analysis was completed by the Levich plots to evaluate the number of electrons involved and by Tafel plots to show the effects on the reaction mechanism.

  3. Facile Synthesis of Quasi-One-Dimensional Au/PtAu Heterojunction Nanotubes and Their Application as Catalysts in an Oxygen-Reduction Reaction.

    PubMed

    Cai, Kai; Liu, Jiawei; Zhang, Huan; Huang, Zhao; Lu, Zhicheng; Foda, Mohamed F; Li, Tingting; Han, Heyou

    2015-05-11

    An intermediate-template-directed method has been developed for the synthesis of quasi-one-dimensional Au/PtAu heterojunction nanotubes by the heterogeneous nucleation and growth of Au on Te/Pt core-shell nanostructures in aqueous solution. The synthesized porous Au/PtAu bimetallic nanotubes (PABNTs) consist of porous tubular framework and attached Au nanoparticles (AuNPs). The reaction intermediates played an important role in the preparation, which fabricated the framework and provided a localized reducing agent for the reduction of the Au and Pt precursors. The Pt7 Au PABNTs showed higher electrocatalytic activity and durability in the oxygen-reduction reaction (ORR) in 0.1 M HClO4 than porous Pt nanotubes (PtNTs) and commercially available Pt/C. The mass activity of PABNTs was 218 % that of commercial Pt/C after an accelerated durability test. This study demonstrates the potential of PABNTs as highly efficient electrocatalysts. In addition, this method provides a facile strategy for the synthesis of desirable hetero-nanostructures with controlled size and shape by utilizing an intermediate template.

  4. Pd@Pt core-shell concave decahedra: A class of catalysts for the oxygen reduction reaction with enhanced activity and durability

    DOE PAGES

    Wang, Xue; Vera, Madeline; Chi, Miaofang; ...

    2015-11-13

    Here, we report a facile synthesis of multiply twinned Pd@Pt core shell concave decahedra by controlling the deposition of Pt on preformed Pd decahedral seeds. The Pt atoms are initially deposited on the vertices of a decahedral seed, followed by surface diffusion to other regions along the edges/ridges and then across the faces. Different from the coating of a Pd icosahedral seed, the Pt atoms prefer to stay at the vertices and edges/ridges of a decahedral seed even when the deposition is conducted at 200 degrees C, naturally generating a core shell structure covered by concave facets. The nonuniformity inmore » the Pt coating can be attributed to the presence of twin boundaries at the vertices, as well as the {100} facets and twin defects along the edges/ridges of a decahedron, effectively trapping the Pt adatoms at these high-energy sites. As compared to a commercial Pt/C catalyst, the Pd@Pt concave decahedra show substantial enhancement in both catalytic activity and durability toward the oxygen reduction reaction (ORR). For the concave decahedra with 29.6% Pt by weight, their specific (1.66 mA/cm2pt) and mass (1.60 A/mg/2pt) ORR activities are enhanced by 4.4 and 6.6 times relative to those of the Pt/C catalyst (0.36 mA/cm2pt and 0.32 A/mgpt, respectively). After 10 000 cycles of accelerated durability test, the concave decahedra still exhibit a mass activity of 0.69 A/mgpt, more than twice that of the pristine Pt/C catalyst.« less

  5. Pd@Pt core-shell concave decahedra: A class of catalysts for the oxygen reduction reaction with enhanced activity and durability

    SciTech Connect

    Wang, Xue; Vera, Madeline; Chi, Miaofang; Xia, Younan; Luo, Ming; Huang, Hongwen; Ruditskiy, Aleksey; Park, Jinho; Bao, Shixiong; Liu, Jingyue; Howe, Jane; Xie, Zhaoxiong

    2015-11-13

    Here, we report a facile synthesis of multiply twinned Pd@Pt core shell concave decahedra by controlling the deposition of Pt on preformed Pd decahedral seeds. The Pt atoms are initially deposited on the vertices of a decahedral seed, followed by surface diffusion to other regions along the edges/ridges and then across the faces. Different from the coating of a Pd icosahedral seed, the Pt atoms prefer to stay at the vertices and edges/ridges of a decahedral seed even when the deposition is conducted at 200 degrees C, naturally generating a core shell structure covered by concave facets. The nonuniformity in the Pt coating can be attributed to the presence of twin boundaries at the vertices, as well as the {100} facets and twin defects along the edges/ridges of a decahedron, effectively trapping the Pt adatoms at these high-energy sites. As compared to a commercial Pt/C catalyst, the Pd@Pt concave decahedra show substantial enhancement in both catalytic activity and durability toward the oxygen reduction reaction (ORR). For the concave decahedra with 29.6% Pt by weight, their specific (1.66 mA/cm2pt) and mass (1.60 A/mg/2pt) ORR activities are enhanced by 4.4 and 6.6 times relative to those of the Pt/C catalyst (0.36 mA/cm2pt and 0.32 A/mgpt, respectively). After 10 000 cycles of accelerated durability test, the concave decahedra still exhibit a mass activity of 0.69 A/mgpt, more than twice that of the pristine Pt/C catalyst.

  6. Nanostructured Ti(0.7)Mo(0.3)O2 support enhances electron transfer to Pt: high-performance catalyst for oxygen reduction reaction.

    PubMed

    Ho, Van Thi Thanh; Pan, Chun-Jern; Rick, John; Su, Wei-Nien; Hwang, Bing-Joe

    2011-08-03

    The slow rate of the oxygen reduction reaction (ORR) and the instability of Pt-based catalysts are two of the most important issues that must be solved in order to make proton exchange membrane fuel cells (PEMFCs) a reality. Additionally, the serious carbon corrosion on the cathode side is a critical problem with respect to the durability of catalyst that limits its wide application. Here, we present a new approach by exploring robust noncarbon Ti(0.7)Mo(0.3)O(2) used as a novel functionalized cocatalytic support for Pt. This approach is based on the novel nanostructure Ti(0.7)Mo(0.3)O(2) support with "electronic transfer mechanism" from Ti(0.7)Mo(0.3)O(2) to Pt that can modify the surface electronic structure of Pt, owing to a shift in the d-band center of the surface Pt atoms. Furthermore, another benefit of Ti(0.7)Mo(0.3)O(2) is the extremely high stability of Pt/Ti(0.7)Mo(0.3)O(2) during potential cycling, which is attributable to the strong metal/support interaction (SMSI) between Pt and Ti(0.7)Mo(0.3)O(2). This also enhances the inherent structural and chemical stability and the corrosion resistance of the TiO(2)-based oxide in acidic and oxidative environments. We also demonstrate that the ORR current densities generated using cocatalytic Pt/Ti(0.7)Mo(0.3)O(2) are respectively ~7- and 2.6-fold higher than those of commercial Pt/C and PtCo/C catalysts with the same Pt loading. This new approach opens a reliable path to the discovery advanced concept in designing new catalysts that can replace the traditional catalytic structure and motivate further research in the field.

  7. Pd@Pt Core-Shell Concave Decahedra: A Class of Catalysts for the Oxygen Reduction Reaction with Enhanced Activity and Durability.

    PubMed

    Wang, Xue; Vara, Madeline; Luo, Ming; Huang, Hongwen; Ruditskiy, Aleksey; Park, Jinho; Bao, Shixiong; Liu, Jingyue; Howe, Jane; Chi, Miaofang; Xie, Zhaoxiong; Xia, Younan

    2015-12-02

    We report a facile synthesis of multiply twinned Pd@Pt core-shell concave decahedra by controlling the deposition of Pt on preformed Pd decahedral seeds. The Pt atoms are initially deposited on the vertices of a decahedral seed, followed by surface diffusion to other regions along the edges/ridges and then across the faces. Different from the coating of a Pd icosahedral seed, the Pt atoms prefer to stay at the vertices and edges/ridges of a decahedral seed even when the deposition is conducted at 200 °C, naturally generating a core-shell structure covered by concave facets. The nonuniformity in the Pt coating can be attributed to the presence of twin boundaries at the vertices, as well as the {100} facets and twin defects along the edges/ridges of a decahedron, effectively trapping the Pt adatoms at these high-energy sites. As compared to a commercial Pt/C catalyst, the Pd@Pt concave decahedra show substantial enhancement in both catalytic activity and durability toward the oxygen reduction reaction (ORR). For the concave decahedra with 29.6% Pt by weight, their specific (1.66 mA/cm(2)Pt) and mass (1.60 A/mgPt) ORR activities are enhanced by 4.4 and 6.6 times relative to those of the Pt/C catalyst (0.36 mA/cm(2)Pt and 0.32 A/mgPt, respectively). After 10,000 cycles of accelerated durability test, the concave decahedra still exhibit a mass activity of 0.69 A/mgPt, more than twice that of the pristine Pt/C catalyst.

  8. Fabricating Pt/Sn-In2O3 Nanoflower with Advanced Oxygen Reduction Reaction Performance for High-Sensitivity MicroRNA Electrochemical Detection.

    PubMed

    Zhang, Kai; Dong, Haifeng; Dai, Wenhao; Meng, Xiangdan; Lu, Huiting; Wu, Tingting; Zhang, Xueji

    2017-01-03

    Herein, an efficient electrochemical tracer with advanced oxygen reduction reaction (ORR) performance was designed by controllably decorating platinum (Pt) (diameter, 1 nm) on the surface of compositionally tunable tin-doped indium oxide nanoparticle (Sn-In2O3) (diameter, 25 nm), and using the Pt/Sn-In2O3 as electrochemical tracer and interfacial term hairpin capture probe, a facile and ultrasensitive microRNA (miRNA) detection strategy was developed. The morphology and composition of the generated Pt/Sn-In2O3 NPs were comprehensively characterized by spectroscopic and microscopic measurements, indicating numerous Pt uniformly anchored on the surface of Sn-In2O3. The interaction between Pt and surface Sn as well as high Pt(111) exposure resulted in the excellent electrochemical catalytic ability and stability of the Pt/Sn-In2O3 ORR. As proof-of-principle, using streptavidin (SA) functionalized Pt/Sn-In2O3 (SA/Pt/Sn-In2O3) as electrochemical tracer to amplify the detectable signal and a interfacial term hairpin probe for target capture probe, a miRNA biosensor with a linear range from 5 pM to 0.5 fM and limit of detection (LOD) down to 1.92 fM was developed. Meanwhile, the inherent selectivity of the term hairpin capture probe endowed the biosensor with good base discrimination ability. The good feasibility for real sample detection was also demonstrated. The work paves a new avenue to fabricate and design high-effective electrocatalytic tracer, which have great promise in new bioanalytical applications.

  9. Rh nanoparticles supported on ultrathin carbon nanosheets for high-performance oxygen reduction reaction and catalytic hydrogenation.

    PubMed

    Lin, Chong; Wu, Guanghao; Li, Huiqin; Geng, Yanmin; Xie, Gang; Yang, Jianhui; Liu, Bin; Jin, Jian

    2017-02-02

    We reported a facile and scalable salt-templated approach to produce monodisperse Rh nanoparticles (NPs) on ultrathin carbon nanosheets with the assistance of calcination under inert gas. More importantly, in spite of the essentially poor ORR activity of Rh/C, the acquired Rh/C hybrid nanosheets display a comparable ORR activity to the optimal commercial Pt/C catalyst, which may be due to the extra-small size of Rh NPs and the 2D defect-rich amorphous carbon nanosheets that can facilitate the charge transfer and reactive surface exposure. Moreover, Rh/C nanosheets present the optimal current density and best durability with the minimum decline during the entire test, so that ∼93% activity after 20 000 s is achieved, indicating a good lifetime for ORR. In contrast, commercial Pt/C and commercial Rh/C exhibited worse durability, so that ∼74% and ∼85% activities after 20 000 s are maintained. What's more, in the model system of reduction of 4-nitrophenol (4-NP), the kinetic constant k for Rh/C nanosheets is 3.1 × 10(-3), which is 4.5 times than that of the commercial Rh/C catalyst, revealing that our Rh/C hybrid nanosheets can be potentially applied in industrial catalytic hydrogenation. This work opens a novel and facile way for the rest of the precious metal NPs to be supported on ultrathin carbon nanosheets for heterogeneous catalysis.

  10. Planning and conduct of Operational Readiness Reviews (ORR)

    SciTech Connect

    1995-11-01

    The purpose of this standard is to describe acceptable methods and approaches to meet the readiness review requirements of DOE 425.1. Specifically, this standard describes methods and approaches to: (1) Determine the type of readiness review which is appropriate to the specific facility startup; (2) Develop the breadth and depth (scope) of the ORR or RA so as to be consistent with the history, hazards, and complexity of the facility being started up; (3) Develop the procedures and conduct an ORR or RA for startup of a specific activity; (4) Verify that the facility is physically ready to startup; (5) Verify that the managers and operators are prepared to manage and operate the facility in the phase in which it is about to startup; (6) Verify that the necessary infrastructure (procedures, staffing, compliance with DOE Orders, rules, and other requirements, etc.) is in place; and (7) Prepare requests for exemptions from the requirements of DOE 425.1

  11. V-doped TiO2 supported Pt as a promising oxygen reduction reaction catalyst: Synthesis, characterization and in-situ evaluation in proton exchange membrane fuel cell

    NASA Astrophysics Data System (ADS)

    Bharti, Abha; Cheruvally, Gouri

    2017-09-01

    This study deals with the synthesis and characterization of V-doped, TiO2 supported Pt catalyst (Pt/V-TiO2) for oxygen reduction reaction (ORR) and its in-situ performance investigation in proton exchange membrane (PEM) fuel cell. Pt/V-TiO2 nanocomposite catalyst is prepared via a facile sol-gel and microwave assisted, modified chemical reduction route and its performance is compared with the undoped TiO2 supported catalyst, Pt/TiO2 prepared in an identical way. The prepared Pt/V-TiO2 and Pt/TiO2 catalysts are employed as cathode catalyst in PEM fuel cell and compared with standard Pt/C catalyst. Their comparative studies are conducted with physical and electrochemical techniques. In-situ electrochemical characterization studies show improved ORR catalytic activity of Pt/V-TiO2 compared to Pt/TiO2. Furthermore, both Pt/TiO2 and Pt/V-TiO2 are more stable than Pt/C when subjected to 6000 voltammetric cycles in the range of 0.2-1.2 V vs. standard hydrogen electrode in operating fuel cell conditions, losing only <20% of its electrochemical surface area as compared to 50% loss exhibited by Pt/C. This study thus demonstrates Pt/V-TiO2 nanocomposite material as a potential cathode catalyst for PEM fuel cell with immense scope for further investigation.

  12. 33. 20HORSE POWER VERTICAL BOILER WAS MANUFACTURED BY ORR & ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    33. 20-HORSE POWER VERTICAL BOILER WAS MANUFACTURED BY ORR & SEMBOWER, FROM READING, PA. IT WAS INSTALLED IN 1929 TO REPLACE THE ORIGINAL BOILER. THE BOILER PROVIDED STEAM TO THE STEAM ENGINE. TO LUBRICATING THE DIE OF THE BRICK AUGER, AND TO THE STEAM PIPES OF THE DRYING ROOM ON THE FLOOR ABOVE. - Moravian Pottery & Tile Works, Southwest side of State Route 313 (Swamp Road), Northwest of East Court Street, Doylestown, Bucks County, PA

  13. Bifunctional Oxygen Reaction Catalysis of Quadruple Manganese Perovskites.

    PubMed

    Yamada, Ikuya; Fujii, Hiroshi; Takamatsu, Akihiko; Ikeno, Hidekazu; Wada, Kouhei; Tsukasaki, Hirofumi; Kawaguchi, Shogo; Mori, Shigeo; Yagi, Shunsuke

    2017-01-01

    Bifunctional electrocatalysts for oxygen evolution/reduction reaction (OER/ORR) are desirable for the development of energy conversion technologies. It is discovered that the manganese quadruple perovskites CaMn7 O12 and LaMn7 O12 show bifunctional catalysis in the OER/ORR. A possible origin of the high OER activity is the unique surface structure through corner-shared planar MnO4 and octahedral MnO6 units to promote direct OO bond formations. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Fundamentals of several reactions for the carbothermic reduction of alumina

    NASA Astrophysics Data System (ADS)

    Walker, Matthew S.

    The current process used for primary aluminum production, the Hall-Heroult process, is reliable, but it also is expensive, consumes large amounts of energy, and generates significant quantities of greenhouse gas emissions. One possible alternative process is the carbothermic reduction of alumina, wherein aluminum is formed by reducing alumina with carbon at high temperatures. This process, if successful, has the potential for substantial reductions in energy consumption, capital costs, and greenhouse gas emissions. One critical component to making this process successful involves obtaining a better understanding of the thermodynamics. Specifically, the key thermodynamic data are the free energies of the reactions and the thermodynamic activities of the metal (Al-C) and slag systems (Al2O3-Al4C3). These are critical for evaluating and controlling the carbothermic process, but experimental data is extremely limited and much of it was measured many years ago when the experimental techniques available may not have been adequate. The overall objective for this research was to assess the validity of the thermodynamic data for this process, as well as its suitability for predicting the behavior of the process. This was done through experimental investigations into both the slag (carbide) making reaction and the binary Al2O 3-Al4C3 phase diagram. The comparison of these results, to those expected based on the current understanding for the process thermodynamics (using FactSage along with the ALCO database), assesses the validity of the thermodynamic data. In this document, the experimental results for investigating the reactions of Al2O3 with carbon are presented. This work involved measuring the operating line for the first step of the carbothermic aluminum process, slag making. This was done using two experimental methods. One involved measuring the evolution of CO from the reactions using a mass spectrometer. The other involved using a vacuum thermobalance (TGA) to

  15. Facile synthesis of platinum-gold alloyed string-bead nanochain networks with the assistance of allantoin and their enhanced electrocatalytic performance for oxygen reduction and methanol oxidation reactions

    NASA Astrophysics Data System (ADS)

    He, Li-Li; Zheng, Jie-Ning; Song, Pei; Zhong, Shu-Xian; Wang, Ai-Jun; Chen, Zhaojiang; Feng, Jiu-Ju

    2015-02-01

    In this work, a facile one-pot wet-chemical method is developed for preparation of bimetallic platinum-gold (Pt-Au) alloyed string-bead nanochain networks, using allantoin as a structure-directing agent, without any template, surfactant, or seed. The characterization experiments are mainly performed by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD) spectroscopy. The as-prepared Pt-Au nanocrystals show enhanced electrocatalytic performance toward oxygen reduction reaction (ORR) mainly predominated by a four-electron pathway, and display improved catalytic activity and high stability for methanol oxidation reaction (MOR) over commercial Pt black and Pt-Ru black.

  16. Surface Pourbaix diagrams and oxygen reduction activity of Pt, Ag and Ni(111) surfaces studied by DFT.

    PubMed

    Hansen, Heine A; Rossmeisl, Jan; Nørskov, Jens K

    2008-07-07

    Based on density functional theory calculations we investigate the electrochemically most stable surface structures as a function of pH and electrostatic potential for Pt(111), Ag(111) and Ni(111), and we construct surface Pourbaix diagrams. We study the oxygen reduction reaction (ORR) on the different surface structures and calculate the free energy of the intermediates. We estimate their catalytic activity for ORR by determining the highest potential at which all ORR reaction steps reduce the free energy. We obtain self-consistency in the sense that the surface is stable under the potential at which that particular surface can perform ORR. Using the self consistent surfaces, the activity of the very reactive Ni surface changes dramatically, whereas the activity of the more noble catalysts Pt and Ag remains unchanged. The reason for this difference is the oxidation of the reactive surface. Oxygen absorbed on the surface shifts the reactivity towards the weak binding region, which in turn increases the activity. The oxidation state of the surface and the ORR potential are constant versus the reversible hydrogen electrode (RHE). The dissolution potential in acidic solution, on the other hand, is constant vs. the standard hydrogen electrode (SHE). For Ag, this means that where the potential for dissolution and ORR are about the same at pH = 0, Ag becomes more stable relative to RHE as pH is increased. Hence the pH dependent stability offers an explanation for the possible use of Ag in alkaline fuel cell cathodes.

  17. Theory and experiments for voltammetric and SECM investigations and application to ORR electrocatalysis at nanoelectrode ensembles of ultramicroelectrode dimensions.

    PubMed

    Fernández, José L; Wijesinghe, Manjula; Zoski, Cynthia G

    2015-01-20

    Theoretical and experimental approaches to characterizing nanoelectrode (NE) ensembles of ultramicroelectrode dimensions (UME-NEEs) as a function of fraction of active area and random NE distribution are described. UME-NEEs were fabricated by addressing microregions of a gold-filled polycarbonate membrane through the UMEs of an underlying microfabricated addressable array. Results of Comsol Multiphysics 3D simulations based on randomly spaced NEs of 15 nm radius on a UME disk geometry of radii up to 5 μm are shown for steady-state voltammetry (SSV) and scanning electrochemical microscopy (SECM) experiments. Analytical equations were developed to describe the diffusion-limited steady-state current and steady-state voltammogram at an UME-NEE. These equations are shown to be in good agreement with the simulations and enabled evaluation of experimental SSVs. Comparison of experimental and simulated SECM approach curves, images, and tip voltammograms enabled the fraction of active area and distribution of NEs to be visualized and determined for individual UME-NEEs. Gold UME-NEEs are shown to be unique platforms for electrodeposition in forming nanoparticle electrodes (UME-NPEs). Electrocatalysis results for the oxygen reduction reaction (ORR) on Pt UME-NPEs in 0.1 M H2SO4 are also shown.

  18. Direct atomic-level insight into the active sites of a high-performance PGM-free ORR catalyst

    DOE PAGES

    Chung, Hoon T.; Cullen, David A.; Higgins, Drew; ...

    2017-08-04

    Platinum group metal–free (PGM-free) metal-nitrogen-carbon catalysts have emerged as a promising alternative to their costly platinum (Pt)–based counterparts in polymer electrolyte fuel cells (PEFCs) but still face some major challenges, including (i) the identification of the most relevant catalytic site for the oxygen reduction reaction (ORR) and (ii) demonstration of competitive PEFC performance under automotive-application conditions in the hydrogen (H2)–air fuel cell. We demonstrate H2-air performance gains achieved with an iron-nitrogen-carbon catalyst synthesized with two nitrogen precursors that developed hierarchical porosity. In current densities recorded in the kinetic region of cathode operation, at fuel cell voltages greater than ~0.75 V,more » were the same as those obtained with a Pt cathode at a loading of 0.1 milligram of Pt per centimeter squared. The catalytic active site we proposed, carbon-embedded nitrogen-coordinated iron (FeN4), was directly visualized with aberration-corrected scanning transmission electron microscopy, and the contributions of these active sites associated with specific lattice-level carbon structures were explored computationally.« less

  19. Direct atomic-level insight into the active sites of a high-performance PGM-free ORR catalyst

    NASA Astrophysics Data System (ADS)

    Chung, Hoon T.; Cullen, David A.; Higgins, Drew; Sneed, Brian T.; Holby, Edward F.; More, Karren L.; Zelenay, Piotr

    2017-08-01

    Platinum group metal-free (PGM-free) metal-nitrogen-carbon catalysts have emerged as a promising alternative to their costly platinum (Pt)-based counterparts in polymer electrolyte fuel cells (PEFCs) but still face some major challenges, including (i) the identification of the most relevant catalytic site for the oxygen reduction reaction (ORR) and (ii) demonstration of competitive PEFC performance under automotive-application conditions in the hydrogen (H2)-air fuel cell. Herein, we demonstrate H2-air performance gains achieved with an iron-nitrogen-carbon catalyst synthesized with two nitrogen precursors that developed hierarchical porosity. Current densities recorded in the kinetic region of cathode operation, at fuel cell voltages greater than ~0.75 V, were the same as those obtained with a Pt cathode at a loading of 0.1 milligram of Pt per centimeter squared. The proposed catalytic active site, carbon-embedded nitrogen-coordinated iron (FeN4), was directly visualized with aberration-corrected scanning transmission electron microscopy, and the contributions of these active sites associated with specific lattice-level carbon structures were explored computationally.

  20. Team leader`s preparation guide for Operational Readiness Reviews (ORR)

    SciTech Connect

    Not Available

    1994-09-01

    This document provides instructions, explanations, and examples for the performance of all phases of an Operational Readiness Review (ORR). Details pertinent to the team leader, team members, and review coordinator are outlined. Sample forms and correspondence are included in appendices. Although this document is for use by DOE ORR team leaders, it can be used by contractor ORR team leaders also.

  1. Effects of ionomer morphology on oxygen reduction on Pt

    SciTech Connect

    Chlistunoff, Jerzy; Pivovar, Bryan

    2015-05-21

    In this paper, the oxygen reduction reaction (ORR) at the interface between platinum and Nafion 1100 equivalent weight was studied as a function of temperature (20–80 °C), humidity (10–100%), scan rate, the manner in which Nafion film was deposited, and the state of the Pt surface using ultramicroelectrodes employing cyclic voltammetry and chronoamperometry. ORR on smooth electrodes was st