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Sample records for cell cathode catalyst

  1. Cathode catalyst for primary phosphoric fuel cells

    NASA Technical Reports Server (NTRS)

    Walsh, F.

    1980-01-01

    Alkylation of Vulcan XC-72 provided the most stable bond type for linking CoTAA to the surface of the carbon; this result is based on data obtained by cyclic voltammetry, pulse voltammetry and by release of 14C from bonded CoTAA. Half-cell tests at 100 C in 85% phosphoric acid showed that CoTAA bonded to the surface of carbon (Vulcan XC-72) via an alkylation procedure is a more active catalyst than is platinum based on a factor of two improvement in Tafel slope; dimeric CoTAA has catalytic activity equal to platinum. Half-cell tests also showed that bonded CoTAA catalysts do not suffer a loss in potential when air is used as a fuel rather than oxygen. Commercially available PTFE was shown to be stable for four months in 200 C 85% phosphoric acid based on lack of change in surface wetting properties, IR and physical characteristics. When stressed electrochemically in 150 C 85% phosphoric acid, PTFE also showed no changes after one month.

  2. Development of gold alloy catalyst cathode for alkaline electrolyte fuel cells

    NASA Technical Reports Server (NTRS)

    Freed, M. S.; Lawrance, R. J.

    1975-01-01

    A program for the development of improved catalyst and Teflon-bonded electrode structures using this improved catalyst is described, for use in fuel cell cathodes. It was found that Au-Pt was superior to the traditional platinum black as a catalyst. The impetus to the program was provided by the discovery that a life-limiting mechanism on the old catalyst was the gradual dissolution of platinum from the cathode and subsequent redeposition in the electrolyte-containing matrix.

  3. Surface-reconstructed graphite nanofibers as a support for cathode catalysts of fuel cells.

    PubMed

    Gan, Lin; Du, Hongda; Li, Baohua; Kang, Feiyu

    2011-04-01

    Graphite nanofibers (GNFs), on which surface graphite edges were reconstructed into nano-loops, were explored as a cathode catalyst support for fuel cells. The high degree of graphitization, as well as the surface-reconstructed nano-loops that possess topological defects for uniform metal deposition, resulted in an improved performance of the GNF-supported Pt catalyst. PMID:21336405

  4. Electricity generation by microbial fuel cell using microorganisms as catalyst in cathode.

    PubMed

    Jang, Jae Kyung; Kan, Jinjun; Bretschger, Orianna; Gorby, Yuri A; Hsu, Lewis; Kim, Byung Hong; Nealson, Kenneth H

    2013-12-01

    The cathode reaction is one of the most seriously limiting factors in a microbial fuel cell (MFC). The critical dissolved oxygen (DO) concentration of a platinum-loaded graphite electrode was reported as 2.2 mg/l, about 10-fold higher than an aerobic bacterium. A series of MFCs were run with the cathode compartment inoculated with activated sludge (biotic) or not (abiotic) on platinum-loaded or bare graphite electrodes. At the beginning of the operation, the current values from MFCs with a biocathode and abiotic cathode were 2.3 ± 0.1 and 2.6 ± 0.2 mA, respectively, at the air-saturated water supply in the cathode. The current from MFCs with an abiotic cathode did not change, but that of MFCs with a biotic cathode increased to 3.0 mA after 8 weeks. The coulomb efficiency was 59.6% in the MFCs with a biotic cathode, much higher than the value of 15.6% of the abiotic cathode. When the DO supply was reduced, the current from MFCs with an abiotic cathode decreased more sharply than in those with a biotic cathode. When the respiratory inhibitor azide was added to the catholyte, the current decreased in MFCs with a biotic cathode but did not change in MFCs with an abiotic cathode. The power density was higher in MFCs with a biotic cathode (430 W/m(3) cathode compartment) than the abiotic cathode MFC (257 W/m(3) cathode compartment). Electron microscopic observation revealed nanowire structures in biofilms that developed on both the anode and on the biocathode. These results show that an electron consuming bacterial consortium can be used as a cathode catalyst to improve the cathode reaction. PMID:24225369

  5. Novel anti-flooding poly(dimethylsiloxane) (PDMS) catalyst binder for microbial fuel cell cathodes

    NASA Astrophysics Data System (ADS)

    Zhang, Fang; Chen, Guang; Hickner, Michael A.; Logan, Bruce E.

    2012-11-01

    Poly(dimethylsiloxane) (PDMS) was investigated as an alternative to Nafion as an air cathode catalyst binder in microbial fuel cells (MFCs). Cathodes were constructed around either stainless steel (SS) mesh or copper mesh using PDMS as both catalyst binder and diffusion layer, and compared to cathodes of the same structure having a Nafion binder. With PDMS binder, copper mesh cathodes produced a maximum power of 1710 ± 1 mW m-2, while SS mesh had a slightly lower power of 1680 ± 12 mW m-2, with both values comparable to those obtained with Nafion binder. Cathodes with PDMS binder had stable power production of 1510 ± 22 mW m-2 (copper) and 1480 ± 56 mW m-2 (SS) over 15 days at cycle 15, compared to a 40% decrease in power with the Nafion binder. Cathodes with the PDMS binder had lower total cathode impedance than those with Nafion. This is due to a large decrease in diffusion resistance, because hydrophobic PDMS effectively prevented catalyst sites from filling up with water, improving oxygen mass transfer. The cost of PDMS is only 0.23% of that of Nafion. These results showed that PDMS is a very effective and low-cost alternative to Nafion binder that will be useful for large scale construction of these cathodes for MFC applications.

  6. Microbial fuel cell cathode with dendrimer encapsulated Pt nanoparticles as catalyst

    NASA Astrophysics Data System (ADS)

    Yang, Xiaoling; Lu, Jindan; Zhu, Yihua; Shen, Jianhua; Zhang, Zhen; Zhang, Jianmei; Chen, Cheng; Li, Chunzhong

    In this paper, we investigated the use of polyamidoamine (PAMAM) dendrimer-encapsulated platinum nanoparticles (Pt-DENs) as a promising type of cathode catalyst for air-cathode single chamber microbial fuel cells (SCMFCs). The Pt-DENs, prepared via template synthesis method, have uniform diameter distribution with size range of 3-5 nm. The Pt-DENs then loaded on to a carbon substrate. For comparison, we also electrodeposited Pt on carbon substrate. The calculation shows that the loading amount of Pt-DENs on carbon substrate is about 0.1 mg cm -2, which is three times lower than that of the electrodeposited Pt (0.3 mg cm -2). By measuring batch experiments, the results show that Pt-DENs in air-cathode SCMFCs have a power density of 630 ± 5 mW m -2 and a current density of 5200 ± 10 mA m -2 (based on the projected anodic surface area), which is significantly better than electrodeposited Pt cathodes (power density: 275 ± 5 mW m -2 and current density: 2050 ± 10 mA m -2). Additionally, Pt-DENs-based cathodes resulted in a higher power production with 129.1% as compared to cathode with electrodeposited Pt. This finding suggests that Pt-DENs in MFC cathodes is a better catalyst and has a lower loading amount than electrodeposited Pt, and may serve as a novel and alternative catalyst to previously used noble metals in MFC applications.

  7. Cathode catalysts for primary phosphoric acid fuel cells

    NASA Technical Reports Server (NTRS)

    1981-01-01

    Alkylation or carbon Vulcan XC-72, the support carbon, was shown to provide the most stable bond type for linking cobalt dehydrodibenzo tetraazannulene (CoTAA) to the surface of the carbon; this result is based on data obtained by cyclic voltammetry, pulse voltammetry and by release of 14C from bonded CoTAA. Half-cell tests at 100 C in 85% phosphoric acid showed that CoTAA bonded to the surface of carbon (Vulcan XC-72) via an alkylation procedure is a more active catalyst than is platinum based on a factor of two improvement in Tafel slope; dimeric CoTAA had catalytic activity equal to platinum. Half-cell tests also showed that bonded CoTAA catalysts do not suffer a loss in potential when air is used as a fuel rather than oxygen. Commercially available polytetrafluroethylene (PTFE) was shown to be unstable in the fuel cell environment with degradation occurring in 2000 hours or less. The PTFE was stressed at 200 C in concentrated phosphoric acid as well as electrochemically stressed in 150 C concentrated phosphoric acid; the surface chemistry of PTFE was observed to change significantly. Radiolabeled PTFE was prepared and used to verify that such chemical changes also occur in the primary fuel cell environment.

  8. Enhanced stability of multilayer graphene-supported catalysts for polymer electrolyte membrane fuel cell cathodes

    NASA Astrophysics Data System (ADS)

    Marinkas, A.; Hempelmann, R.; Heinzel, A.; Peinecke, V.; Radev, I.; Natter, H.

    2015-11-01

    One of the biggest challenges in the field of polymer electrolyte membrane fuel cells (PEMFC) is to enhance the lifetime and the long-term stability of PEMFC electrodes, especially of cathodes, furthermore, to reduce their platinum loading, which could lead to a cost reduction for efficient PEMFCs. These demands could be achieved with a new catalyst support architecture consisting of a composite of carbon structures with significant different morphologies. A highly porous cathode catalyst support layer is prepared by addition of various carbon types (carbon black particles, multi-walled carbon nanotubes (MWCNT)) to multilayer graphene (MLG). The reported optimized cathodes shows extremely high durability and similar performance to commercial standard cathodes but with 89% lower Pt loading. The accelerated aging protocol (AAP) on the membrane electrode assemblies (MEA) shows that the presence of MLG increases drastically the durability and the Pt-extended electrochemical surface area (ECSA). In fact, after the AAP slightly enhanced performance can be observed for the MLG-containing cathodes instead of a performance loss, which is typical for the commercial carbon-based cathodes. Furthermore, the presence of MLG drastically decreases the ECSA loss rate. The MLG-containing cathodes show up to 6.8 times higher mass-normalized Pt-extended ECSA compared to the commercial standard systems.

  9. Evaluation of low-cost cathode catalysts for high yield biohydrogen production in microbial electrolysis cell.

    PubMed

    Wang, L; Chen, Y; Ye, Y; Lu, B; Zhu, S; Shen, S

    2011-01-01

    As an ideal fuel due to the advantages of no pollution, high combustion heat and abundant sources, hydrogen gas can be produced from organic matter through the electrohydrogenesis process in microbial electrolysis cells. But in many MECs, platinum is often used as catalyst, which limits the practical applications of MECs. To reduce the cost of the MECs, Ni-based alloy cathodes were developed by electrodepositing. In this paper hydrogen production using Ni-W-P cathode was studied for the first time in a single-chamber membrane-free MEC. At an applied voltage of 0.9 V, MECs with Ni-W-P cathodes obtained a hydrogen production rate of 1.09 m3/m3/day with an cathodic hydrogen recovery of 74%, a Coulombic efficiency of 56% and an electrical energy efficiency relative to electrical input of 139%, which was the best result of reports in this study. The Ni-W-P cathode demonstrated a better electrocatalytic activity than the Ni-Ce-P cathode and achieved a comparable performance to the Pt cathode in terms of hydrogen production rate, Coulombic efficiency, cathodic hydrogen recovery and electrical energy efficiency at 0.9 V. PMID:21278465

  10. Solid oxide fuel cells having porous cathodes infiltrated with oxygen-reducing catalysts

    SciTech Connect

    Liu, Meilin; Liu, Ze; Liu, Mingfei; Nie, Lifang; Mebane, David Spencer; Wilson, Lane Curtis; Surdoval, Wayne

    2014-08-12

    Solid-oxide fuel cells include an electrolyte and an anode electrically coupled to a first surface of the electrolyte. A cathode is provided, which is electrically coupled to a second surface of the electrolyte. The cathode includes a porous backbone having a porosity in a range from about 20% to about 70%. The porous backbone contains a mixed ionic-electronic conductor (MIEC) of a first material infiltrated with an oxygen-reducing catalyst of a second material different from the first material.

  11. Manganese dioxide as a new cathode catalyst in microbial fuel cells

    NASA Astrophysics Data System (ADS)

    Li, Xiang; Hu, Boxun; Suib, Steven; Lei, Yu; Li, Baikun

    This study focused on manganese oxides with a cryptomelane-type octahedral molecular sieve (OMS-2) structure to replace platinum as a cathode catalyst in microbial fuel cells (MFCs). Undoped (ud-OSM-2) and three catalysts doped with cobalt (Co-OMS-2), copper (Cu-OMS-2), and cerium (Ce-OMS-2) to enhance their catalytic performances were investigated. The novel OMS-2 cathodes were examined in granular activated carbon MFC (GACMFC) with sodium acetate as the anode reagent and oxygen in air as the cathode reagent. The results showed that after 400 h of operation, the Co-OMS-2 and Cu-OMS-2 exhibited good catalytic performance in an oxygen reduction reaction (ORR). The voltage of the Co-OMS-2 GACMFC was 217 mV, and the power density was 180 mW m -2. The voltage of the Cu-OMS-2 GACMFC was 214 mV and the power density was 165 mW m -2. The internal resistance (R in) of the OMS-2 GACMFCs (18 ± 1 Ω) was similar to that of the platinum GACMFCs (17 Ω). Furthermore, the degradation rates of organic substrates in the OMS-2 GACMFCs were twice those in the platinum GACMFCs, which enhance their wastewater treatment efficiencies. This study indicated that using OMS-2 manganese oxides to replace platinum as a cathodic catalyst enhances power generation, increases contaminant removal, and substantially reduces the cost of MFCs.

  12. Iron-based cathode catalyst with enhanced power density in polymer electrolyte membrane fuel cells.

    PubMed

    Proietti, Eric; Jaouen, Frédéric; Lefèvre, Michel; Larouche, Nicholas; Tian, Juan; Herranz, Juan; Dodelet, Jean-Pol

    2011-01-01

    H(2)-air polymer-electrolyte-membrane fuel cells are electrochemical power generators with potential vehicle propulsion applications. To help reduce their cost and encourage widespread use, research has focused on replacing the expensive Pt-based electrocatalysts in polymer-electrolyte-membrane fuel cells with a lower-cost alternative. Fe-based cathode catalysts are promising contenders, but their power density has been low compared with Pt-based cathodes, largely due to poor mass-transport properties. Here we report an iron-acetate/phenanthroline/zeolitic-imidazolate-framework-derived electrocatalyst with increased volumetric activity and enhanced mass-transport properties. The zeolitic-imidazolate-framework serves as a microporous host for phenanthroline and ferrous acetate to form a catalyst precursor that is subsequently heat treated. A cathode made with the best electrocatalyst from this work, tested in H(2)-O(2,) has a power density of 0.75 W cm(-2) at 0.6 V, a meaningful voltage for polymer-electrolyte-membrane fuel cells operation, comparable with that of a commercial Pt-based cathode tested under identical conditions. PMID:21811245

  13. Nonactivated and Activated Biochar Derived from Bananas as Alternative Cathode Catalyst in Microbial Fuel Cells

    PubMed Central

    Yuan, Haoran; Deng, Lifang; Qi, Yujie; Kobayashi, Noriyuki; Tang, Jiahuan

    2014-01-01

    Nonactivated and activated biochars have been successfully prepared by bananas at different thermotreatment temperatures. The activated biochar generated at 900°C (Biochar-act900) exhibited improved oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) performances in alkaline media, in terms of the onset potential and generated current density. Rotating disk electron result shows that the average of 2.65 electrons per oxygen molecule was transferred during ORR of Biochar-act900. The highest power density of 528.2 mW/m2 and the maximum stable voltage of 0.47 V were obtained by employing Biochar-act900 as cathode catalyst, which is comparable to the Pt/C cathode. Owning to these advantages, it is expected that the banana-derived biochar cathode can find application in microbial fuel cell systems. PMID:25243229

  14. Effects of operating conditions on durability of polymer electrolyte membrane fuel cell Pt cathode catalyst layer

    NASA Astrophysics Data System (ADS)

    Ohyagi, Shinsuke; Matsuda, Toshihiko; Iseki, Yohei; Sasaki, Tatsuyoshi; Kaito, Chihiro

    In this study, we investigated the effects of humidity and oxygen reduction on the degradation of the catalyst of a polymer electrolyte membrane fuel cell (PEMFC) in a voltage cycling test. To elucidate the effect of humidity on the voltage cycling corrosion of a carbon-supported Pt catalyst with 3 nm Pt particles, voltage cycling tests based on 10,000 cycles were conducted using 100% relative humidity (RH) hydrogen as anode gas and nitrogen of varying humidities as cathode gas. The degradation rate of an electrochemical surface area (ECSA) was almost 50% under 189% RH nitrogen atmosphere and the Pt average particle diameter after 10,000 cycles under these conditions was about 2.3 times that of a particle of fresh catalyst because of the agglomeration of Pt particles. The oxygen reduction reaction (ORR) that facilitated Pt catalyst agglomeration when oxygen was employed as the cathode gas also demonstrated that Pt agglomeration was prominent in higher concentrations of oxygen. The ECSA degradation figure in 100% RH oxygen was similar to that in 189% RH nitrogen. It was concluded that liquid water, which was dropped under a supersaturated condition or generated by ORR, accelerated Pt agglomeration. In this paper, we suggest that the Pt agglomeration degradation occurs in a flooding area in a cell plane.

  15. Membrane fuel cell cathode catalysts based on titanium oxide supported platinum nanoparticles.

    PubMed

    Gebauer, Christian; Jusys, Zenonas; Wassner, Maximilian; Hüsing, Nicola; Behm, R Jürgen

    2014-07-21

    The potential of platinum catalysts supported on pure, nitrogen-, or carbon-doped titania for application in the oxygen reduction reaction (ORR), as a cathode catalyst in polymer electrolyte membrane fuel cells, is investigated. The oxide supports are synthesized by using a sol-gel route. Modification with nitrogen and carbon doping is achieved by thermal decomposition of urea and the structure-directing agent P123. Platinum nanoparticles are prepared by reduction of a Pt(IV) salt in ethylene glycol and subsequently immobilized on different support materials. Structural and electronic properties of the support materials and the resulting catalysts are characterized by various methods, including X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy. These results and electrochemical characterization of the support materials and platinum nanoparticle catalysts indicate distinct support effects in the catalysts. The electrocatalytic performance of these catalysts in the ORR, as determined in rotating ring disc electrode measurements, is promising. Also here, distinct support effects can be identified. Correlations with the structural/electronic and the electrochemical properties are discussed, as well as the role of metal-support interactions. PMID:24850442

  16. High Temperature Membrane & Advanced Cathode Catalyst Development

    SciTech Connect

    Protsailo, Lesia

    2006-04-20

    Current project consisted of three main phases and eighteen milestones. Short description of each phase is given below. Table 1 lists program milestones. Phase 1--High Temperature Membrane and Advanced Catalyst Development. New polymers and advanced cathode catalysts were synthesized. The membranes and the catalysts were characterized and compared against specifications that are based on DOE program requirements. The best-in-class membranes and catalysts were downselected for phase 2. Phase 2--Catalyst Coated Membrane (CCM) Fabrication and Testing. Laboratory scale catalyst coated membranes (CCMs) were fabricated and tested using the down-selected membranes and catalysts. The catalysts and high temperature membrane CCMs were tested and optimized. Phase 3--Multi-cell stack fabrication. Full-size CCMs with the down-selected and optimized high temperature membrane and catalyst were fabricated. The catalyst membrane assemblies were tested in full size cells and multi-cell stack.

  17. Using bacterial catalyst in the cathode of microbial desalination cell to improve wastewater treatment and desalination.

    PubMed

    Wen, Qinxue; Zhang, Huichao; Chen, Zhiqiang; Li, Yufei; Nan, Jun; Feng, Yujie

    2012-12-01

    A microbial desalination cell (MDC) is able to desalinate salt water without energy consumption whilst generating bioenergy. Previously MDCs used abiotic cathodes, which are restricted in application by high operating costs and low levels of sustainability whereas, in the present study, an aerobic biocathode consisting of carbon felt and bacterial catalysts was tested. The biocathode MDC produced a maximum voltage of 609 mV, the value of which was 136 mV higher than that of an air cathode MDC operated under the same conditions. The salinity of 39 mL of salt water (35 g L(-1) NaCl) was reduced by 92% using 0.441 L of anode solution (11.3:1), with a coulombic efficiency of 96.2 ± 3.8% and a total desalination rate of 2.83 mg h(-1). The biocathode MDC proved to be a promising approach for efficient desalination of salt water. PMID:23026321

  18. Use of pyrolyzed iron ethylenediaminetetraacetic acid modified activated carbon as air-cathode catalyst in microbial fuel cells.

    PubMed

    Xia, Xue; Zhang, Fang; Zhang, Xiaoyuan; Liang, Peng; Huang, Xia; Logan, Bruce E

    2013-08-28

    Activated carbon (AC) is a cost-effective catalyst for the oxygen reduction reaction (ORR) in air-cathode microbial fuel cells (MFCs). To enhance the catalytic activity of AC cathodes, AC powders were pyrolyzed with iron ethylenediaminetetraacetic acid (FeEDTA) at a weight ratio of FeEDTA:AC = 0.2:1. MFCs with FeEDTA modified AC cathodes and a stainless steel mesh current collector produced a maximum power density of 1580 ± 80 mW/m(2), which was 10% higher than that of plain AC cathodes (1440 ± 60 mW/m(2)) and comparable to Pt cathodes (1550 ± 10 mW/m(2)). Further increases in the ratio of FeEDTA:AC resulted in a decrease in performance. The durability of AC-based cathodes was much better than Pt-catalyzed cathodes. After 4.5 months of operation, the maximum power density of Pt cathode MFCs was 50% lower than MFCs with the AC cathodes. Pyridinic nitrogen, quaternary nitrogen and iron species likely contributed to the increased activity of FeEDTA modified AC. These results show that pyrolyzing AC with FeEDTA is a cost-effective and durable way to increase the catalytic activity of AC. PMID:23902951

  19. Binary and ternary nano-catalysts as cathode materials in proton exchange membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Trimm, Bryan Dunning

    The need for alternative energy, in order to reduce dependence on petroleum based fuels, has increased in recent years. Public demand is at an all-time high for low emitting or none polluting energy sources, driving the research for cleaner technology. Lithium batteries and fuel cells have the ability to produce this alternative energy with much cleaner standards, while allowing for portability and high energy densities. This work focuses on the performance of nanocatalysts in Proton Exchange Membrane Fuel Cell or PEMFC. A key technical challenge is the sluggish rate for oxygen reduction reaction at the cathode of PEMFC, which requires highly-active and stable catalysts. Our investigation is directed at increasing stability and durability as well as reducing high loading of noble metals in these catalyst materials. Binary and ternary structured nanomaterials, e.g., Pt51V1Co48/C and Pd xCu1-x/C, have been synthesized and tested in a PEMFC, in order to gain a better understanding of their durability and efficiency. In addition to electrochemical characterization, synchrotron x-ray techniques at the Advance Photon Source in Argonne National Lab have also been used for the structural characterization.

  20. Power generation using spinel manganese-cobalt oxide as a cathode catalyst for microbial fuel cell applications.

    PubMed

    Mahmoud, Mohamed; Gad-Allah, Tarek A; El-Khatib, K M; El-Gohary, Fatma

    2011-11-01

    This study focused on the use of spinel manganese-cobalt (Mn-Co) oxide, prepared by a solid state reaction, as a cathode catalyst to replace platinum in microbial fuel cells (MFCs) applications. Spinel Mn-Co oxides, with an Mn/Co atomic ratios of 0.5, 1, and 2, were prepared and examined in an air cathode MFCs which was fed with a molasses-laden synthetic wastewater and operated in batch mode. Among the three Mn-Co oxide cathodes and after 300 h of operation, the Mn-Co oxide catalyst with Mn/Co atomic ratio of 2 (MnCo-2) exhibited the highest power generation 113 mW/m2 at cell potential of 279 mV, which were lower than those for the Pt catalyst (148 mW/m2 and 325 mV, respectively). This study indicated that using spinel Mn-Co oxide to replace platinum as a cathodic catalyst enhances power generation, increases contaminant removal, and substantially reduces the cost of MFCs. PMID:21944282

  1. Double-chamber microbial fuel cell with a non-platinum-group metal Fe-N-C cathode catalyst.

    PubMed

    Santoro, Carlo; Serov, Alexey; Narvaez Villarrubia, Claudia W; Stariha, Sarah; Babanova, Sofia; Schuler, Andrew J; Artyushkova, Kateryna; Atanassov, Plamen

    2015-03-01

    Non-Pt-group metal (non-PGM) materials based on transition metal-nitrogen-carbon (M-N-C) and derived from iron salt and aminoantipyrine (Fe-AAPyr) of mebendazole (Fe-MBZ) were studied for the first time as cathode catalysts in double-chamber microbial fuel cells (DCMFCs). The pH value of the cathode chamber was varied from 6 to 11 to elucidate the activity of those catalysts in acidic to basic conditions. The Fe-AAPyr- and Fe-MBZ-based cathodes were compared to a Pt-based cathode used as a baseline. Pt cathodes performed better at pH 6-7.5 and had similar performances at pH 9 and a substantially lower performance at pH 11 at which Fe-AAPyr and Fe-MBZ demonstrated their best electrocatalytic activity. The power density achieved with Pt constantly decreased from 94-99 μW cm(-2) at pH 6 to 55-57 μW cm(-2) at pH 11. In contrast, the power densities of DCMFs using Fe-AAPyr and Fe-MBZ were 61-68 μW cm(-2) at pH 6, decreased to 51-58 μW cm(-2) at pH 7.5, increased to 65-75 μW cm(-2) at pH 9, and the highest power density was achieved at pH 11 (68-80 μW cm(-2) ). Non-PGM cathode catalysts can be manufactured at the fraction of the cost of the Pt-based ones. The higher performance and lower cost indicates that non-PGM catalysts may be a viable materials choice in large-scale microbial fuel cells. PMID:25606716

  2. MWCNT-supported phthalocyanine cobalt as air-breathing cathodic catalyst in glucose/O2 fuel cells

    NASA Astrophysics Data System (ADS)

    Elouarzaki, Kamal; Haddad, Raoudha; Holzinger, Michael; Le Goff, Alan; Thery, Jessica; Cosnier, Serge

    2014-06-01

    Simple and highly efficient glucose fuel cells using abiotic catalysts and different ion exchange membranes were designed. The glucose fuel cells are based on a multi-walled carbon nanotube (MWCNT)-supported cobalt phthalocyanine (CoPc) cathode and a carbon black/platinum (C/Pt) anode. The electrocatalytic activity of the MWCNT/CoPc electrode for oxygen reduction was investigated by cyclic and linear sweep voltammetry. The electrochemical experiments show that CoPc exhibits promising catalytic properties for oxygen reduction due to its high overpotential and efficiency at reduced metal load. The MWCNT/CoPc electrodes were applied to the oxygen reduction reaction as air-breathing cathode in a single-chambered glucose fuel cell. This cathode was associated with a C/Pt anode in fuel cell configurations using either an anion (Nafion®) or a cation (Tokuyama) exchange membrane. The best fuel cell configuration delivered a maximum power density of 2.3 mW cm-2 and a cell voltage of 0.8 V in 0.5 M KOH solution containing 0.5 M glucose using the Tokuyama membrane at ambient conditions. Beside the highest power density per cathodic catalyst mass (383 W g-1), these glucose fuel cells exhibit a high operational stability, delivering 0.3 mW cm-2 after 50 days.

  3. Inhibition of microbial growth on air cathodes of single chamber microbial fuel cells by incorporating enrofloxacin into the catalyst layer.

    PubMed

    Liu, Weifeng; Cheng, Shaoan; Sun, Dan; Huang, Haobin; Chen, Jie; Cen, Kefa

    2015-10-15

    The inevitable growth of aerobic bacteria on the surface of air cathodes is an important factor reducing the performance stability of air cathode single-chamber membrane-free microbial fuel cells (MFCs). Thus searching for effective methods to inhibit the cathodic microbial growth is critical for the practical application of MFCs. In this study, enrofloxacin (ENR), a broad spectrum fluoroquinolone antibiotic, was incorporated into the catalyst layer of activated carbon air cathodes (ACACs) to inhibit the cathodic microbial growth. The biomass content on ACACs was substantially reduced by 60.2% with ENR treatment after 91 days of MFCs operation. As a result of the inhibited microbial growth, the oxygen reduction catalytic performance of the ENR treated ACACs was much stable compared to the fast performance decline of the untreated control. Consequently, a quite stable electricity production was obtained for the MFCs with the ENR treated ACACs, in contrast with a 22.5% decrease in maximum power density of the MFCs with the untreated cathode. ENR treatment of ACACs showed minimal effects on the anode performance. These results indicate that incorporating antibiotics into ACACs should be a simple and effective strategy to inhibit the microbial growth and improve the long-term stability of the performance of air cathode and the electricity production of MFCs. PMID:25957076

  4. Generalized flooded agglomerate model for the cathode catalyst layer of a polymer electrolyte membrane fuel cell

    NASA Astrophysics Data System (ADS)

    Kamarajugadda, Sai; Mazumder, Sandip

    2012-06-01

    The flooded agglomerate model has found prolific usage in modeling the oxygen reduction reaction within the cathode catalyst layer of a polymer electrolyte membrane fuel cell (PEMFC). The assumption made in this model is that the ionomer-coated carbon-platinum agglomerate is spherical in shape and that the spheres are non-overlapping. This assumption is convenient because the governing equations lend themselves to closed-form analytical solution when a spherical shape is assumed. In reality, micrographs of the catalyst layer show that the agglomerates are best represented by sets of overlapping spheres of unequal radii. In this article, the flooded agglomerate is generalized by considering overlapping spheres of unequal radii. As a first cut, only two overlapping spheres are considered. The governing reaction-diffusion equations are solved numerically using the unstructured finite-volume method. The volumetric current density is extracted for various parametric variations, and tabulated. This sub-grid-scale generalized flooded agglomerate model is first validated and finally coupled to a computational fluid dynamics (CFD) code for predicting the performance of the PEMFC. Results show that when the agglomerates are small (<200 nm equivalent radius), the effect of agglomerate shape on the overall PEMFC performance is insignificant. For large agglomerates, on the other hand, the effect of agglomerate shape was found to be critical, especially for high current densities for which the mass transport resistance within the agglomerate is strongly dependent on the shape of the agglomerate, and was found to correlate well with the surface-to-volume ratio of the agglomerate.

  5. Chalcogen catalysts for polymer electrolyte fuel cell

    DOEpatents

    Zelenay, Piotr; Choi, Jong-Ho; Alonso-Vante, Nicolas; Wieckowski, Andrzej; Cao, Dianxue

    2010-08-24

    A methanol-tolerant cathode catalyst and a membrane electrode assembly for fuel cells that includes such a cathode catalyst. The cathode catalyst includes a support having at least one transition metal in elemental form and a chalcogen disposed on the support. Methods of making the cathode catalyst and membrane electrode assembly are also described.

  6. Highly active nanoporous Pt-based alloy as anode and cathode catalyst for direct methanol fuel cells

    NASA Astrophysics Data System (ADS)

    Chen, Xiaoting; Jiang, Yingying; Sun, Junzhe; Jin, Chuanhong; Zhang, Zhonghua

    2014-12-01

    In this paper, we explore nanoporous PtPdAlCu (np-PtPdAlCu) quaternary alloy through ball-milling with the subsequent two-step dealloying strategy. The microstructure and catalytic performance of the np-PtPdAlCu catalyst have been characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (SEM), transmission electron microscopy (TEM), and electrochemical measurements. The np-PtPdAlCu catalyst exhibits an open bi-continuous interpenetrating ligament/channel structure with a length scale of 2.3 ± 0.5 nm. The np-PtPdAlCu catalyst shows 2 and 3.5 times enhancement in the mass activity and area specific activity towards methanol oxidation at anode respectively, compared to the Johnson Matthey (JM) Pt/C (40 wt.%) catalyst. Moreover, the CO stripping peak of np-PtPdAlCu is 0.49 V (vs. SCE), indicating a 180 mV negative shift in comparison with the Pt/C catalyst (0.67 V vs. SCE). In addition, the np-PtPdAlCu catalyst also shows an enhanced oxygen reduction reaction (ORR) activity at cathode compared to Pt/C. The present study provides a facile and effective route to design high-performance catalysts for direct methanol fuel cells (DMFCs).

  7. Immobilization of a Metal-Nitrogen-Carbon Catalyst on Activated Carbon with Enhanced Cathode Performance in Microbial Fuel Cells.

    PubMed

    Yang, Wulin; Logan, Bruce E

    2016-08-23

    Applications of microbial fuel cells (MFCs) are limited in part by low power densities mainly due to cathode performance. Successful immobilization of an Fe-N-C co-catalyst on activated carbon (Fe-N-C/AC) improved the oxygen reduction reaction to nearly a four-electron transfer, compared to a twoelectron transfer achieved using AC. With acetate as the fuel, the maximum power density was 4.7±0.2 W m(-2) , which is higher than any previous report for an air-cathode MFC. With domestic wastewater as a fuel, MFCs with the Fe-N-C/AC cathode produced up to 0.8±0.03 W m(-2) , which was twice that obtained with a Pt-catalyzed cathode. The use of this Fe-N-C/AC catalyst can therefore substantially increase power production, and enable broader applications of MFCs for renewable electricity generation using waste materials. PMID:27416965

  8. Using ammonium bicarbonate as pore former in activated carbon catalyst layer to enhance performance of air cathode microbial fuel cell

    NASA Astrophysics Data System (ADS)

    Li, Da; Qu, Youpeng; Liu, Jia; He, Weihua; Wang, Haiman; Feng, Yujie

    2014-12-01

    The rolling catalyst layers in air cathode microbial fuel cells (MFCs) are prepared by introducing NH4HCO3 as pore former (PF) with four PF/activated carbon mass ratios of 0.1, 0.2, 0.3 and 1.0. The maximum power density of 892 ± 8 mW m-2 is obtained by cathodes with the mass ratio of 0.2, which is 33% higher than that of the control reactor (without PF, 671 ± 22 mW m-2). Pore analysis indicates the porosity increases by 38% and the major pore range concentrates between 0.5 μm-0.8 μm which likely facilitates to enrich the active reaction sites compared to 0.8 μm-3.0 μm in the control and other PF-cathodes. In addition, pore structure endows the cathode improved exchange current density by 2.4 times and decreased charge transfer resistance by 44%, which are the essential reasons to enhance the oxygen reduction. These results show that addition of NH4HCO3 proves an effective way to change the porosity and pore distribution of catalyst layers and then enhance the MFC performance.

  9. Carbon supported cobalt oxide nanoparticles-iron phthalocyanine as alternative cathode catalyst for oxygen reduction in microbial fuel cells

    NASA Astrophysics Data System (ADS)

    Ahmed, Jalal; Yuan, Yong; Zhou, Lihua; Kim, Sunghyun

    2012-06-01

    The high cost and limited resources of precious metals as oxygen reduction catalysts (ORR) hindered the widespread use of microbial fuel cells (MFCs) in practice. Here, the feasibility of metal oxide assisted metal macrocyclic complex was investigated as a catalyst for ORR in an air-cathode MFC. Electrochemical results revealed that cobalt oxide (CoOx) incorporation increased the ORR activity of iron phthalocyanine (FePc). In MFCs, the maximum power density of 654 ± 32 mW m-2 was achieved from the C-CoOx-FePc cathode, which was 37% higher than the power density of carbon supported FePc (C-FePc). The voltage output of the MFC only decreased to 85% of its initial voltage after 50 cycles, suggesting that the synthesized catalyst showed acceptable long-term stability. The voltage drop partially resulted from the covering of biofilm on the catalyst layer. This work provided a potential alternative to Pt in MFCs for sustainable energy generation.

  10. Copper nitride nanocubes: size-controlled synthesis and application as cathode catalyst in alkaline fuel cells.

    PubMed

    Wu, Haibin; Chen, Wei

    2011-10-01

    Copper nitride nanocubes are synthesized in a facile one-phase process. The crystal size could be tuned easily by using different primary amines as capping agents. Such Pt-free nanocrystals exhibit electrocatalytic activity toward oxygen reduction and appear to be promising cathodic electrocatalysts in alkaline fuel cells. PMID:21894995

  11. High catalytic activity and pollutants resistivity using Fe-AAPyr cathode catalyst for microbial fuel cell application

    NASA Astrophysics Data System (ADS)

    Santoro, Carlo; Serov, Alexey; Villarrubia, Claudia W. Narvaez; Stariha, Sarah; Babanova, Sofia; Artyushkova, Kateryna; Schuler, Andrew J.; Atanassov, Plamen

    2015-11-01

    For the first time, a new generation of innovative non-platinum group metal catalysts based on iron and aminoantipyrine as precursor (Fe-AAPyr) has been utilized in a membraneless single-chamber microbial fuel cell (SCMFC) running on wastewater. Fe-AAPyr was used as an oxygen reduction catalyst in a passive gas-diffusion cathode and implemented in SCMFC design. This catalyst demonstrated better performance than platinum (Pt) during screening in “clean” conditions (PBS), and no degradation in performance during the operation in wastewater. The maximum power density generated by the SCMFC with Fe-AAPyr was 167 ± 6 μW cm-2 and remained stable over 16 days, while SCMFC with Pt decreased to 113 ± 4 μW cm-2 by day 13, achieving similar values of an activated carbon based cathode. The presence of S2- and showed insignificant decrease of ORR activity for the Fe-AAPyr. The reported results clearly demonstrate that Fe-AAPyr can be utilized in MFCs under the harsh conditions of wastewater.

  12. High catalytic activity and pollutants resistivity using Fe-AAPyr cathode catalyst for microbial fuel cell application

    PubMed Central

    Santoro, Carlo; Serov, Alexey; Villarrubia, Claudia W. Narvaez; Stariha, Sarah; Babanova, Sofia; Artyushkova, Kateryna; Schuler, Andrew J.; Atanassov, Plamen

    2015-01-01

    For the first time, a new generation of innovative non-platinum group metal catalysts based on iron and aminoantipyrine as precursor (Fe-AAPyr) has been utilized in a membraneless single-chamber microbial fuel cell (SCMFC) running on wastewater. Fe-AAPyr was used as an oxygen reduction catalyst in a passive gas-diffusion cathode and implemented in SCMFC design. This catalyst demonstrated better performance than platinum (Pt) during screening in “clean” conditions (PBS), and no degradation in performance during the operation in wastewater. The maximum power density generated by the SCMFC with Fe-AAPyr was 167 ± 6 μW cm−2 and remained stable over 16 days, while SCMFC with Pt decreased to 113 ± 4 μW cm−2 by day 13, achieving similar values of an activated carbon based cathode. The presence of S2− and showed insignificant decrease of ORR activity for the Fe-AAPyr. The reported results clearly demonstrate that Fe-AAPyr can be utilized in MFCs under the harsh conditions of wastewater. PMID:26563922

  13. Iron-nitrogen-activated carbon as cathode catalyst to improve the power generation of single-chamber air-cathode microbial fuel cells.

    PubMed

    Pan, Yajun; Mo, Xiaoping; Li, Kexun; Pu, Liangtao; Liu, Di; Yang, Tingting

    2016-04-01

    In order to improve the performance of microbial fuel cell (MFC), iron-nitrogen-activated carbon (Fe-N-C) as an excellent oxygen reduction reaction (ORR) catalyst was prepared here using commercial activated carbon (AC) as matrix and employed in single chamber MFC. In MFC, the maximum power density increased to 2437±55mWm(-2), which was 2 times of that with AC. The open circuit potential (OCP) of Fe-N-C cathode (0.47) was much higher than that of AC cathode (0.21V). The R0 of Fe-N-C decreased by 47% from 14.36Ω (AC) to 7.6Ω (Fe-N-C). From X-ray photoelectron spectroscopy (XPS), pyridinic nitrogen, quaternary nitrogen and iron species were present, which played an important role in the ORR performance of Fe-N-C. These results demonstrated that the as-prepared Fe-N-C material provided a potential alternative to Pt in AC air cathode MFC for relatively desirable energy generation and wastewater treatment. PMID:26898678

  14. Co-Pt core-shell nanostructured catalyst prepared by selective chemical vapor pulse deposition of Pt on Co as a cathode in polymer electrolyte fuel cells

    SciTech Connect

    Seo, Sang-Joon; Chung, Ho-Kyoon; Yoo, Ji-Beom; Chae, Heeyeop; Seo, Seung-Woo; Min Cho, Sung

    2014-01-15

    A new type of PtCo/C catalyst for use as a cathode in polymer electrolyte fuel cells was prepared by selective chemical vapor pulse deposition (CVPD) of Pt on the surface of Co. The activity of the prepared catalyst for oxygen reduction was higher than that of a catalyst prepared by sequential impregnation (IMP) with the two metallic components. This catalytic activity difference occurs because the former catalyst has smaller Pt crystallites that produce stronger Pt-Co interactions and have a larger Pt surface area. Consequently, the CVPD catalyst has a great number of Co particles that are in close contact with the added Pt. The Pt surface was also electronically modified by interactions with Co, which were stronger in the CVPD catalyst than in the IMP catalyst, as indicated by X-ray diffraction, X-ray photoemission spectroscopy, and cyclic voltammetry measurements of the catalysts.

  15. Bifunctional Ag/Fe/N/C Catalysts for Enhancing Oxygen Reduction via Cathodic Biofilm Inhibition in Microbial Fuel Cells.

    PubMed

    Dai, Ying; Chan, Yingzi; Jiang, Baojiang; Wang, Lei; Zou, Jinlong; Pan, Kai; Fu, Honggang

    2016-03-23

    Limitation of the oxygen reduction reaction (ORR) in single-chamber microbial fuel cells (SC-MFCs) is considered an important hurdle in achieving their practical application. The cathodic catalysts faced with a liquid phase are easily primed with the electrolyte, which provides more surface area for bacterial overgrowth, resulting in the difficulty in transporting protons to active sites. Ag/Fe/N/C composites prepared from Ag and Fe-chelated melamine are used as antibacterial ORR catalysts for SC-MFCs. The structure-activity correlations for Ag/Fe/N/C are investigated by tuning the carbonization temperature (600-900 °C) to clarify how the active-constituents of Ag/Fe and N-species influence the antibacterial and ORR activities. A maximum power density of 1791 mW m(-2) is obtained by Ag/Fe/N/C (630 °C), which is far higher than that of Pt/C (1192 mW m(-2)), only having a decline of 16.14% after 90 days of running. The Fe-bonded N and the cooperation of pyridinic N and pyrrolic N in Ag/Fe/N/C contribute equally to the highly catalytic activity toward ORR. The ·OH or O2(-) species originating from the catalysis of O2 can suppress the biofilm growth on Ag/Fe/N/C cathodes. The synergistic effects between the Ag/Fe heterojunction and N-species substantially contribute to the high power output and Coulombic efficiency of Ag/Fe/N/C catalysts. These new antibacterial ORR catalysts show promise for application in MFCs. PMID:26938657

  16. Load cycle durability of a graphitized carbon black-supported platinum catalyst in polymer electrolyte fuel cell cathodes

    NASA Astrophysics Data System (ADS)

    Takei, Chikara; Kakinuma, Katsuyoshi; Kawashima, Kazuhito; Tashiro, Keisuke; Watanabe, Masahiro; Uchida, Makoto

    2016-08-01

    We focus on Pt degradation occurring during fuel cell vehicle (FCV) combined drive cycles involving load and open circuit voltage (OCV) just after startup and during idling. Load cycle durability is evaluated as a function of OCV/load holding time, load rate and relative humidity (RH) with a graphitized carbon black-supported platinum catalyst (Pt/GCB) in the cathode. The degradation of Pt/GCB is suppressed for shorter OCV holding times, lower load rates and lower RH. Scanning ion microscopy (SIM) images of membrane cross-sections indicate that the amount of Pt deposited in the membrane decreases during drive cycles involving load with short OCV holding times. Investigations of the Pt distribution in the cathode catalyst layer (CL) by using scanning TEM-EDX show that the dissolution of Pt is suppressed on the membrane side in the CL. The Pt dissolution is accelerated by the high Pt oxidation due to the long OCV holding time. A load cycle with both long OCV holding time and low load inhibits the Pt2+ migration into the membrane but accelerates the Pt particle growth due to electrochemical Ostwald ripening; meanwhile, a load cycle with long OCV holding time at lower RH prevents both the Pt dissolution and particle growth.

  17. Catalysts for ultrahigh current density oxygen cathodes for space fuel cell applications

    NASA Technical Reports Server (NTRS)

    Tryk, D.; Yeager, E.; Shingler, M.; Aldred, W.; Wang, C.

    1990-01-01

    The objective of this research was to identify promising electrocatalyst/support systems for the oxygen cathode in alkaline fuel cells operating at relatively high temperatures, O2 pressures and current densities. A number of materials were prepared, including Pb-Ru and Pb-Ir pyrochlores, RuO2 and Pt-doped RuO2, and lithiated NiO. Several of these were prepared using techniques that had not been previously used to prepare them. Particularly interesting is the use of the alkaline solution technique to prepare the Pt-doped Pb-Ru pyrochlore in high area form. Well-crystallized Pb(2)Ru(2)O(7-y) was used to fabricate high performance O2 cathodes with relatively good stability in room temperature KOH. This material was also found to be stable over a useful potential range at approximately 140 C in concentrated KOH. Other pyrochlores were found to be either unstable (amorphous samples) or the fabrication of the gas-fed electrodes could not be fully optimized during this project period. Future work may be directed at this problem. High area platinum supported on conductive metal oxide supports produced mixed results: small improvements in O2 reduction performance for Pb(2)Ru(2)O(7-y) but a large improvement for Li-doped NiO at room temperature. Nearly reversible behavior was observed for the O2/OH couple for Li-doped NiO at approximately 200 C.

  18. 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. PMID:24239870

  19. PRELIMINARY IN-SITU X-RAY ABSORPTION FINE STRUCTURE EXAMINATION OF PT/C AND PTCO/C CATHODE CATALYSTS IN AN OPERATIONAL POLYMER ELECTROLYTE FUEL CELL

    SciTech Connect

    Phelan, B.T.; Myers, D.J.; Smith, M.C.

    2009-01-01

    State-of-the-art polymer electrolyte fuel cells require a conditioning period to reach optimized cell performance. There is insuffi cient understanding about the behavior of catalysts during this period, especially with regard to the changing environment of the cathode electrocatalyst, which is typically Pt nanoparticles supported on high surface area Vulcan XC-72 carbon (Pt/C). The purpose of this research was to record preliminary observations of the changing environment during the conditioning phase using X-Ray Absorption Fine Structure (XAFS) spectroscopy. XAFS was recorded for a Pt/C cathode at the Pt L3-edge and a PtCo/C cathode at both the Pt L3-edge and Co K-edge. Using precision machined graphite cell-blocks, both transmission and fl uorescence data were recorded at Sector 12-BM-B of Argonne National Laboratory’s Advanced Photon Source. The fl uorescence and transmission edge steps allow for a working description of the changing electrocatalyst environment, especially water concentration, at the anode and cathode as functions of operating parameters. These features are discussed in the context of how future analysis may correlate with potential, current and changing apparent thickness of the membrane electrode assembly through loss of catalyst materials (anode, cathode, carbon support). Such direct knowledge of the effect of the conditioning protocol on the electrocatalyst may lead to better catalyst design. In turn, this may lead to minimizing, or even eliminating, the conditioning period.

  20. Nickel oxide and carbon nanotube composite (NiO/CNT) as a novel cathode non-precious metal catalyst in microbial fuel cells.

    PubMed

    Huang, Jianjian; Zhu, Nengwu; Yang, Tingting; Zhang, Taiping; Wu, Pingxiao; Dang, Zhi

    2015-10-15

    Comparing with the precious metal catalysts, non-precious metal catalysts were preferred to use in microbial fuel cells (MFCs) due to the low cost and high oxygen reduction reaction (ORR) efficiency. In this study, the transmission electron microscope and X-ray diffraction as well as Raman investigation revealed that the prepared nanoscale NiO was attached on the surface of CNT. Cyclic voltammogram and rotating ring-disk electrode tests showed that the NiO/CNT composite catalyst had an apparent oxygen reduction peak and 3.5 electron transfer pathway was acquired under oxygen atmosphere. The catalyst performance was highly dependent on the percentage of NiO in the CNT nanocomposites. When 77% NiO/CNT nano-sized composite was applied as cathode catalyst in membrane free single-chamber air cathode MFC, a maximum power density of 670 mW/m(2) and 0.772 V of OCV was obtained. Moreover, the MFC with pure NiO (control) could not achieve more than 0.1 V. All findings suggested that NiO/CNT could be a potential cathode catalyst for ORR in MFCs. PMID:26002018

  1. Catalysts for ultrahigh current density oxygen cathodes for space fuel cell applications

    NASA Technical Reports Server (NTRS)

    Tryk, Donald A.; Yeager, E.

    1992-01-01

    The objective was to identify promising electrocatalyst/support systems for oxygen cathodes capable of operating at ultrahigh current densities in alkaline fuel cells. Such cells will require operation at relatively high temperatures and O2 pressures. A number of materials were prepared, including Pb-Ru and Pb-Ir pyrochlores, RuO2 and Pt-doped RuO2, lithiated NiO and La-Ni perovskites. Several of these materials were prepared using techniques that had not been previously used to prepare them. Particularly interesting was the use of the alkaline solution technique to prepare Pt-doped and Pb-Ru pyrochlores in high area form. Also interesting was the use of the fusion (melt) method for preparing the Pb-Ru pyrochlore. Several of the materials were also deposited with platinum. Well-crystallized Pb2Ru2O(7-y) was used to fabricate very high performance O2 cathodes with good stability in room temperature KOH. This material was also found to be stable over a useful potential range at approx. 140 C in concentrated KOH. For some of the samples, fabrication of the gas-fed electrodes could not be fully optimized during this project period. Future work may be directed at this problem. Pyrochlores that were not well-crystallized were found to be unstable in alkaline solution. Very good O2 reduction performance and stability were observed with Pb2RuO(7-y) in a carbon-based gas-fed electrode with an anion-conducting membrane placed on the electrolyte side of the electrode. The performance came within a factor of about two of that observed without carbon. High area platinum and gold supported on several conductive metal oxide supports were examined. Only small improvements in O2 reduction performance at room temperature were observed for Pb2Ru2O(7-y) as a support because of the high intrinsic activity of the pyrochlore. In contrast, a large improvement was observed for Li-doped NiO as a support for Pt. Very poor performance was observed for Au deposited on Li-NiO at approx. 150 C

  2. Nb doped TiO2 as a Cathode Catalyst Support Material for Polymer Electrolyte Membrane Fuel Cells

    NASA Astrophysics Data System (ADS)

    O'Toole, Alexander W.

    In order to reduce the emissions of greenhouse gases and reduce dependence on the use of fossil fuels, it is necessary to pursue alternative sources of energy. Transportation is a major contributor to the emission of greenhouse gases due to the use of fossil fuels in the internal combustion engine. To reduce emission of these pollutants into the atmosphere, research is needed to produce alternative solutions for vehicle transportation. Low temperature polymer electrolyte membrane fuel cells are energy conversion devices that provide an alternative to the internal combustion engine, however, they still have obstacles to overcome to achieve large scale implementation. T he following work presents original research with regards to the development of Nb doped TiO2 as a cathode catalyst support material for low temperature polymer electrolyte membrane fuel cells. The development of a new process to synthesize nanoparticles of Nb doped TiO2 with controlled compositions is presented as well as methods to scale up the process and optimize the synthesis for the aforementioned application. In addition to this, comparison of both electrochemical activity and durability with current state of the art Pt on high surface area carbon black (Vulcan XC-72) is investigated. Effects of the strong metal-support interaction on the electrochemical behavior of these materials is also observed and discussed.

  3. Carbon supported Ag nanoparticles as high performance cathode catalyst for H2/O2 anion exchange membrane fuel cell

    PubMed Central

    Xin, Le; Zhang, Zhiyong; Wang, Zhichao; Qi, Ji; Li, Wenzhen

    2013-01-01

    A solution phase-based nanocapsule method was successfully developed to synthesize non-platinum metal catalyst—carbon supported Ag nanoparticles (Ag/C). XRD patterns and TEM image show Ag nanoparticles with a small average size (5.4 nm) and narrow size distribution (2–9 nm) are uniformly dispersed on the carbon black Vulcan XC-72 support. The intrinsic activity and pathway of oxygen reduction reaction (ORR) on the Ag/C and commercial Pt/C were investigated using rotating ring disk electrode (RRDE) tests at room temperature. The results confirmed that the 4-electron pathway of ORR proceeds on small Ag nanoparticles, and showed comparable ORR activities on the self-prepared Ag/C and a commercial Pt/C. A single H2-O2 anion exchange membrane fuel cell (AEMFC) with the Ag/C cathode catalyst exhibited an open circuit potential of 0.98 V and a peak power density of 190 mW/cm2 at 80°C. PMID:24790944

  4. Development of ternary alloy cathode catalysts for phosphoric acid fuel cells: Final report

    SciTech Connect

    Jalan, V.; Kosek, J.; Giner, J.; Taylor, E. J.; Anderson, E.; Bianchi, V.; Brooks, C.; Cahill, K.; Cropley, C.; Desai, M.; Frost, D.; Morriseau, B.; Paul, B.; Poirier, J.; Rousseau, M.; Swette, L.; Waterhouse, R.

    1988-11-01

    The overall objective of the program was the identification development and incorporation of high activity platinum ternary alloys on corrosion resistant supports, for use in advanced phosphoric acid fuel cells. Two high activity ternary alloys, Pr-Cr-Ce and Pt-Ni-Co, both supported on Vulcan XC-72, were identified during the course of the program. The Pr-Ni-Co system was selected for optimization, including preparation and evaluation on corrosion resistant supports such as 2700/degree/C heat-treated Vulcan XC-72 and 2700/degree/ heat-treated Black Pearls 2000. A series of tests identified optimum metal ratios, heat-treatment temperatures and heat-treatment atmospheres for the Pr-Ni-Co system. During characterization testing, it was discovered that approximately 50% of the nickel and cobalt present in the starting material could be removed, subsequent to alloy formation, without degrading performance. Extremely stable full cell performance was observed for the Pt-Ni-Co system during a 10,000 hour atmosphere pressure life test. Several theories are proposed to explain the enhancement in activity due to alloy formation. Recommendations are made for future research in this area. 62 refs., 23 figs., 27 tabs.

  5. Effect of the nanosized TiO2 particles in Pd/C catalysts as cathode materials in direct methanol fuel cells.

    PubMed

    Choi, Mahnsoo; Han, Choonsoo; Kim, In-Tae; Lee, Ji-Jung; Lee, Hong-Ki; Shim, Joongpyo

    2011-07-01

    Pd-TiO2/C catalysts were prepared by impregnating titanium dioxide (TiO2) on carbon-supported Pd (Pd/C) for use as the catalyst for the oxygen reduction reaction (ORR) in direct methanol fuel cells (DMFCs). Transmission electron microscope (TEM), scanning electron microscope (SEM) and X-ray diffraction (XRD) analyses were carried to confirm the distribution, morphology and structure of Pd and TiO2 on the carbon support. In fuel cell test, we confirmed that the addition of TiO2 nanoparticles make the improved catalytic activity of oxygen reduction. The electrochemical characterization of the Pd-TiO2/C catalyst for the ORR was carried out by cyclic voltammetry (CV) in the voltage window of 0.04 V to 1.2 V with scan rate of 25 mV/s. With the increase in the crystallite size of TiO2, the peak potential for OH(ads) desorption on the surface of Pd particle shifted to higher potential. This implies that TiO2 might affect the adsorption and desorption of oxygen molecules on Pd catalyst. The performance of Pd-TiO2/C as a cathode material was found to be similar to or better performance than that of Pt/C. PMID:22121727

  6. Fibrous polyaniline@manganese oxide nanocomposites as supercapacitor electrode materials and cathode catalysts for improved power production in microbial fuel cells.

    PubMed

    Ansari, Sajid Ali; Parveen, Nazish; Han, Thi Hiep; Ansari, Mohammad Omaish; Cho, Moo Hwan

    2016-03-23

    Fibrous Pani-MnO2 nanocomposite were prepared using a one-step and scalable in situ chemical oxidative polymerization method. The formation, structural and morphological properties were investigated using a range of characterization techniques. The electrochemical capacitive behavior of the fibrous Pani-MnO2 nanocomposite was examined by cyclic voltammetry and galvanostatic charge-discharge measurements using a three-electrode experimental setup in an aqueous electrolyte. The fibrous Pani-MnO2 nanocomposite achieved high capacitance (525 F g(-1) at a current density of 2 A g(-1)) and excellent cycling stability of 76.9% after 1000 cycles at 10 A g(-1). Furthermore, the microbial fuel cell constructed with the fibrous Pani-MnO2 cathode catalyst showed an improved power density of 0.0588 W m(-2), which was higher than that of pure Pani and carbon paper, respectively. The improved electrochemical supercapacitive performance and cathode catalyst performance in microbial fuel cells were attributed mainly to the synergistic effect of Pani and MnO2 in fibrous Pani-MnO2, which provides high surface area for the electrode/electrolyte contact as well as electronic conductive channels and exhibits pseudocapacitance behavior. PMID:26967202

  7. 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.

  8. Nitrogen-doped graphene/CoNi alloy encased within bamboo-like carbon nanotube hybrids as cathode catalysts in microbial fuel cells

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

    Cost-effective catalysts are of key importance to the successful deployment of microbial fuel cells (MFCs) for electricity generation from organic wastes. Herein, a novel catalyst prepared by one-step synthesis strategy is reported. The catalyst features N-doped bamboo-like carbon nanotube (BCNT) in which CoNi-alloy is encapsulated at the end and/or the middle section of the tube with many graphene layers inside inner cavities of BCNT (N-G@CoNi/BCNT). The prepared N-G@CoNi/BCNT exhibits a high oxygen reduction reaction (ORR) activity with an early onset potential of 0.06 V vs. Ag/AgCl and a comparable exchange current density to that of commercial Pt/C. The excellent catalytic activity is further evidenced by a high electron transfer number of 3.63. When being applied in MFCs, the N-G@CoNi/BCNT yields an average current density of 6.7 A m-2, slightly lower than that of Pt/C but with a less mass transfer potential loss. The cost of the N-G@CoNi/BCNT for constructing a 1-m2 cathode electrode is 200 times lower than that of Pt/C. With such a competitive price and excellent electrocatalytic-activity resulting from its unique morphology, CoNi-alloy/nitrogen dopants, considerable specific surface area, and carbon-coated alloy/graphene hybridization, the present catalyst is a promising candidate for ORR catalysts in MFCs for energy recovery from wastes.

  9. Easy-to-operate and low-temperature synthesis of gram-scale nitrogen-doped graphene and its application as cathode catalyst in microbial fuel cells.

    PubMed

    Feng, Leiyu; Chen, Yinguang; Chen, Lang

    2011-12-27

    Nitrogen-doped graphene (NG), with unique electronic properties, is showing great promise for a wide range of practical applications. However, the reported approaches for NG synthesis are usually complex, require high temperatures, produce lower atomic ratios of nitrogen to carbon (N/C), and do not deliver products in a reasonably large quantity. Here we report an easy-to-operate and low-temperature method to synthesize NG in gram-scale quantities with a denotation process. High-resolution transmission electron microscopy, Raman spectroscopy, and X-ray diffraction characterization suggested that the synthesized NG films were uniformly multilayered and had a high crystalline quality. In the graphene sheets the existence of nitrogen substitution with an atomic ratio of N/C 12.5%, which was greater than those reported in the literature, was confirmed by X-ray photoelectron spectroscopic analysis. In the neutral phosphate buffer solution, the synthesized NG was demonstrated to act as a metal-free electrode with excellent electrocatalytic activity and long-term operation stability for oxygen reduction via a combination of two-electron and four-electron pathways. When the NG was applied as the cathode catalyst of microbial fuel cells (MFCs), the obtained maximum power density was comparable to that of conventional platinum catalyst. More importantly, MFCs with NG produced power more stably and less expensively than those with Pt catalyst, indicating that the synthesized NG might be used as a good alternative to Pt catalyst in MFCs with a long run. PMID:22029637

  10. Synthesis and electrochemical performances of LiNiCuZn oxides as anode and cathode catalyst for low temperature solid oxide fuel cell.

    PubMed

    Jing, Y; Qin, H; Liu, Q; Singh, M; Zhu, B

    2012-06-01

    Low temperature solid oxide fuel cell (LTSOFC, 300-600 degrees C) is developed with advantages compared to conventional SOFC (800-1000 degrees C). The electrodes with good catalytic activity, high electronic and ionic conductivity are required to achieve high power output. In this work, a LiNiCuZn oxides as anode and cathode catalyst is prepared by slurry method. The structure and morphology of the prepared LiNiCuZn oxides are characterized by X-ray diffraction and field emission scanning electron microscopy. The LiNiCuZn oxides prepared by slurry method are nano Li0.28Ni0.72O, ZnO and CuO compound. The nano-crystallites are congregated to form ball-shape particles with diameter of 800-1000 nm. The LiNiCuZn oxides electrodes exhibits high ion conductivity and low polarization resistance to hydrogen oxidation reaction and oxygen reduction reaction at low temperature. The LTSOFC using the LiNiCuZn oxides electrodes demonstrates good cell performance of 1000 mW cm(-2) when it operates at 470 degrees C. It is considered that nano-composite would be an effective way to develop catalyst for LTSOFC. PMID:22905585

  11. Synthesis of iron oxide/partly graphitized carbon composites as a high-efficiency and low-cost cathode catalyst for microbial fuel cells.

    PubMed

    Ma, Ming; Dai, Ying; Zou, Jin-long; Wang, Lei; Pan, Kai; Fu, Hong-gang

    2014-08-27

    Waste cornstalks and pomelo skins are used as carbon resources for preparing nanocomposites of iron oxide and partly graphitized carbon (Fe3O4/PGC-CS and Fe3O4/PGC-PS). The results showed that Fe3O4 with a face-centered cubic structure is uniformly dispersed on the skeleton of Fe3O4/GC, and the highest SBET values of Fe3O4/PGC-CS (476.5 m(2) g(-1)) and Fe3O4/PGC-PS (547.7 m(2) g(-1)) are obtained at 1000 °C. The electrical conductivity and density of catalytic active sites are correspondingly improved by the introduction of Fe species. Microbial fuel cells (MFCs) with a mixed composite (Fe3O4/PGC-CS:Fe3O4/PGC-PS = 1:1) cathode (three-dimensional structures) generate the highest power density of 1502 ± 30 mW m(-2), which is 26.01% higher than that of Pt/C (1192 ± 33 mW m(-2)) and only declines by 7.12% after 18 cycles. The Fe3O4/PGC-CS cathode has the highest Coulombic efficiency (24.3 ± 0.7%). The Fe3O4/PGC composites exhibit high oxygen reduction reactivity, low charge transfer resistances, and long-term stability and can be used as a low-cost and high-efficiency catalyst for MFCs. PMID:25084054

  12. Surface-Regulated Nano-SnO2/Pt3Co/C Cathode Catalysts for Polymer Electrolyte Fuel Cells Fabricated by a Selective Electrochemical Sn Deposition Method.

    PubMed

    Nagasawa, Kensaku; Takao, Shinobu; Nagamatsu, Shin-ichi; Samjeské, Gabor; Sekizawa, Oki; Kaneko, Takuma; Higashi, Kotaro; Yamamoto, Takashi; Uruga, Tomoya; Iwasawa, Yasuhiro

    2015-10-14

    We have achieved significant improvements for the oxygen reduction reaction activity and durability with new SnO2-nanoislands/Pt3Co/C catalysts in 0.1 M HClO4, which were regulated by a strategic fabrication using a new selective electrochemical Sn deposition method. The nano-SnO2/Pt3Co/C catalysts with Pt/Sn = 4/1, 9/1, 11/1, and 15/1 were characterized by STEM-EDS, XRD, XRF, XPS, in situ XAFS, and electrochemical measurements to have a Pt3Co core/Pt skeleton-skin structure decorated with SnO2 nanoislands at the compressive Pt surface with the defects and dislocations. The high performances of nano-SnO2/Pt3Co/C originate from efficient electronic modification of the Pt skin surface (site 1) by both the Co of the Pt3Co core and surface nano-SnO2 and more from the unique property of the periphery sites of the SnO2 nanoislands at the compressive Pt skeleton-skin surface (more active site 2), which were much more active than expected from the d-band center values. The white line peak intensity of the nano-SnO2/Pt3Co/C revealed no hysteresis in the potential up-down operations between 0.4 and 1.0 V versus RHE, unlike the cases of Pt/C and Pt3Co/C, resulting in the high ORR performance. Here we report development of a new class of cathode catalysts with two different active sites for next-generation polymer electrolyte fuel cells. PMID:26412503

  13. Nitrogen-doped carbonaceous catalysts for gas-diffusion cathodes for alkaline aluminum-air batteries

    NASA Astrophysics Data System (ADS)

    Davydova, E. S.; Atamanyuk, I. N.; Ilyukhin, A. S.; Shkolnikov, E. I.; Zhuk, A. Z.

    2016-02-01

    Cobalt tetramethoxyphenyl porphyrin and polyacrylonitrile - based catalysts for oxygen reduction reaction were synthesized and characterized by means of SEM, TEM, XPS, BET, limited evaporation method, rotating disc and rotating ring-disc electrode methods. Half-cell and Al-air cell tests were carried out to determine the characteristics of gas-diffusion cathodes. Effect of active layer thickness and its composition on the characteristics of the gas-diffusion cathodes was investigated. Power density of 300 mW cm-2 was achieved for alkaline Al-air cell with an air-breathing polyacrylonitrile-based cathode.

  14. Catalyst-infiltrated supporting cathode for thin-film SOFCs

    SciTech Connect

    Yamahara, Keiji; Jacobson, Craig P.; Visco, Steven J.; De Jonghe,Lutgard C.

    2004-04-12

    The fabrication and electrochemical performance of co-fired,LSM-SYSZ [i.e., La0.65Sr0.30MnO3 (LSM) - (Sc2O3)0.1(Y2O3)0.01(ZrO2)0.89] supported thin-film cells were examined using humidified hydrogen as a fuel. Co-firing of bi-layers and tri-layers was successful at 1250 C by optimizing the amount of carbon pore formers. A power density of a factor of 2.5 higher than that recently reported for the same type of cell at 800 C [3] was obtained for a cell with cobalt infiltration into the supporting cathode: the peak power densities were 455, 389, 285, 202, 141mW/cm2 at 800, 750, 700, 650, 600 C, respectively, and in most cases power densities at 0.7V exceeded more than 90 percent of the peak output. Increasing the cathode porosity from 43 to 53 percent improved peak power densities by as much as 1.3, shifting the diffusion limitation to high current densities. Cobalt infiltration into the support improved those by as much as a factor of 2 due to a significant reduction in non-ohmic resistance. These results demonstrate that cobalt catalyst-infiltrated LSM can be effective and low-cost supporting electrodes for reduced temperature, thin film SOFCs.

  15. Formic acid fuel cells and catalysts

    SciTech Connect

    Masel, Richard I.; Larsen, Robert; Ha, Su Yun

    2010-06-22

    An exemplary fuel cell of the invention includes a formic acid fuel solution in communication with an anode (12, 134), an oxidizer in communication with a cathode (16, 135) electrically linked to the anode, and an anode catalyst that includes Pd. An exemplary formic acid fuel cell membrane electrode assembly (130) includes a proton-conducting membrane (131) having opposing first (132) and second surfaces (133), a cathode catalyst on the second membrane surface, and an anode catalyst including Pd on the first surface.

  16. Hydrothermal synthesis of highly crystalline RuS{sub 2} nanoparticles as cathodic catalysts in the methanol fuel cell and hydrochloric acid electrolysis

    SciTech Connect

    Li, Yanjuan; Li, Nan; Yanagisawa, Kazumichi; Li, Xiaotian; Yan, Xiao

    2015-05-15

    Highlights: • Highly crystalline RuS{sub 2} nanoparticles have been first synthesized by a “one-step” hydrothermal method. • The product presents a pure cubic phase of stoichiometric ratio RuS{sub 2} with average particle size of 14.8 nm. • RuS{sub 2} nanoparticles were used as cathodic catalysts in methanol fuel cell and hydrochloric acid electrolysis. • The catalyst outperforms commercial Pt/C in methanol tolerance and stability towards Cl{sup −}. - Abstract: Highly crystalline ruthenium sulfide (RuS{sub 2}) nanoparticles have been first synthesized by a “one-step” hydrothermal method at 400 °C, using ruthenium chloride and thiourea as reactants. The products were characterized by powder X-ray diffraction (XRD), scanning electron microscopy/energy disperse spectroscopy (SEM/EDS), thermo gravimetric-differential thermal analyze (TG-DTA), transmission electron microscopy equipped with selected area electron diffraction (TEM/SAED). Fourier transform infrared spectra (IR), and X-ray photoelectron spectroscopy (XPS). XRD result illustrates that the highly crystalline product presents a pure cubic phase of stoichiometric ratio RuS{sub 2} and the average particle size is 14.8 nm. SEM and TEM images display the products have irregular shape of 6–25 nm. XPS analyst indicates that the sulfur exists in the form of S{sub 2}{sup 2−}. Cyclic voltammetry (CV), rotating disk electrode (RDE), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS) measurements are conducted to evaluate the electrocatalytic activity and stability of the highly crystalline RuS{sub 2} nanoparticles in oxygen reduction reaction (ORR) for methanol fuel cell and hydrochloric acid electrolysis. The results illustrate that RuS{sub 2} is active towards oxygen reduction reaction. Although the activity of RuS{sub 2} is lower than that of Pt/C, the RuS{sub 2} catalyst outperforms commercial Pt/C in methanol tolerance and stability towards Cl{sup −}.

  17. Fuel cell development for transportation: Catalyst development

    SciTech Connect

    Doddapaneni, N.

    1996-04-01

    Fuel cells are being considered as alternate power sources for transportation and stationary applications. With proton exchange membrane (PEM) fuel cells the fuel crossover to cathodes causes severe thermal management and cell voltage drop due to oxidation of fuel at the platinized cathodes. The main goal of this project was to design, synthesize, and evaluate stable and inexpensive transition metal macrocyclic catalysts for the reduction of oxygen and be electrochemically inert towards anode fuels such as hydrogen and methanol.

  18. Highly durable and active non-precious air cathode catalyst for zinc air battery

    NASA Astrophysics Data System (ADS)

    Chen, Zhu; Choi, Ja-Yeon; Wang, Haijiang; Li, Hui; Chen, Zhongwei

    The electrochemical stability of non-precious FeCo-EDA and commercial Pt/C cathode catalysts for zinc air battery have been compared using accelerated degradation test (ADT) in alkaline condition. Outstanding oxygen reduction reaction (ORR) stability of the FeCo-EDA catalyst was observed compared with the commercial Pt/C catalyst. The FeCo-EDA catalyst retained 80% of the initial mass activity for ORR whereas the commercial Pt/C catalyst retained only 32% of the initial mass activity after ADT. Additionally, the FeCo-EDA catalyst exhibited a nearly three times higher mass activity compared to that of the commercial Pt/C catalyst after ADT. Furthermore, single cell test of the FeCo-EDA and Pt/C catalysts was performed where both catalysts exhibited pseudolinear behaviour in the 12-500 mA cm -2 range. In addition, 67% higher peak power density was observed from the FeCo-EDA catalyst compared with commercial Pt/C. Based on the half cell and single cell tests the non-precious FeCo-EDA catalyst is a very promising ORR electrocatalyst for zinc air battery.

  19. Long term investigations of silver cathodes for alkaline fuel cells

    NASA Astrophysics Data System (ADS)

    Wagner, N.; Schulze, M.; Gülzow, E.

    Alkaline fuel cells (AFC) are an interesting alternative to polymer electrolyte fuel cells (PEFC). In AFC no expensive platinum metal is necessary; silver can be used for the oxygen reduction reaction (ORR) (cathode catalyst). For technical use of AFC the long term behavior of AFC components is important, especially that of the electrodes. The investigated cathodes for AFC consist of a mixture of silver catalyst and polytetrafluorethylene (PTFE) as organic binder rolled onto a metal web. The electrodes were electrochemically investigated through measuring V- i curves and electrochemical impedance spectroscopy (EIS). The electrochemical characterization and the long term tests were performed in half-cells at 70 °C using pure oxygen (1 bar) under galvanostatic conditions. The cathodes were electrochemically investigated in half-cells using reference electrodes (Hg/HgO) by periodically recording V- i curve and electrochemical impedance spectroscopy. In addition, the cathodes were physically characterized by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS).

  20. Development of highly active and stable hybrid cathode catalyst for PEMFCs

    NASA Astrophysics Data System (ADS)

    Jung, Won Suk

    Polymer electrolyte membrane fuel cells (PEMFCs) are attractive power sources of the future for a variety of applications including portable electronics, stationary power, and automobile application. However, sluggish cathode kinetics, high Pt cost, and durability issues inhibit the commercialization of PEMFCs. To overcome these drawbacks, research has been focused on alloying Pt with transition metals since alloy catalysts show significantly improved catalytic properties like high activity, selectivity, and durability. However, Pt-alloy catalysts synthesized using the conventional impregnation method exhibit uneven particle size and poor particle distribution resulting in poor performance and/or durability in PEMFCs. In this dissertation, a novel catalyst synthesis methodology is developed and compared with catalysts prepared using impregnation method and commercial catalysts. Two approaches are investigated for the catalyst development. The catalyst durability was studied under U. S. DRIVE Fuel Cell Tech Team suggested protocols. In the first approach, the carbon composite catalyst (CCC) having active sites for oxygen reduction reaction (ORR) is employed as a support for the synthesis of Pt/CCC catalyst. The structural and electrochemical properties of Pt/CCC catalyst are investigated using high-resolution transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy, while RDE and fuel cell testing are carried out to study the electrochemical properties. The synergistic effect of CCC and Pt is confirmed by the observed high activity towards ORR for the Pt/CCC catalyst. The second approach is the synthesis of Co-doped hybrid cathode catalysts (Co-doped Pt/CCC) by diffusing the Co metal present within the CCC support into the Pt nanoparticles during heat-treatment. The optimized Co-doped Pt/CCC catalyst performed better than the commercial catalysts and the catalyst prepared using the impregnation method in PEMFCs and showed high

  1. High performance, high durability non-precious metal fuel cell catalysts

    DOEpatents

    Wood, Thomas E.; Atanasoski, Radoslav; Schmoeckel, Alison K.

    2016-03-15

    This invention relates to non-precious metal fuel cell cathode catalysts, fuel cells that contain these catalysts, and methods of making the same. The fuel cell cathode catalysts are highly nitrogenated carbon materials that can contain a transition metal. The highly nitrogenated carbon materials can be supported on a nanoparticle substrate.

  2. Ex situ testing method to characterize cathode catalysts degradation under simulated start-up/shut-down conditions - A contribution to polymer electrolyte membrane fuel cell benchmarking

    NASA Astrophysics Data System (ADS)

    Marcu, A.; Toth, G.; Kundu, S.; Colmenares, L. C.; Behm, R. J.

    2012-10-01

    The paper introduces a novel ex situ test procedure that was developed to quantify the ageing of catalyst layers under critical automotive fuel cell conditions during start-up/shut-down phases. It is based on liquid electrolyte measurements, using a thin film catalyst electrode. The overall degradation under start-up/shut-down conditions is assessed by the decay in electrochemically active surface area. Furthermore, contributions from different processes leading to catalyst degradation such as Pt dissolution and Pt particle growth/agglomeration can be separated. Finally, using a differential electrochemical mass spectrometry (DEMS) set-up, also the extent and role of carbon corrosion under these conditions is accessible. The potential of this, compared to in situ fuel cell stack tests, rather fast and less costly ex situ test procedure is demonstrated in measurements using a commercial, graphitized carbon-supported Pt catalyst. The results of the degradation test and in particular the contributions from different degradation processes such as Pt dissolution, Pt particle growth/agglomeration and carbon corrosion during different stages of catalyst ageing are discussed.

  3. Degradation characteristics of air cathode in zinc air fuel cells

    NASA Astrophysics Data System (ADS)

    Ma, Ze; Pei, Pucheng; Wang, Keliang; Wang, Xizhong; Xu, Huachi; Liu, Yongfeng; peng, Guanlin

    2015-01-01

    The zinc air fuel cell (ZAFC) is a promising candidate for electrical energy storage and electric vehicle propulsion. However, its limited durability has become a major obstacle for its successful commercialization. In this study, 2-cell stacks, 25 cm² cells and three-electrode half-cells are constructed to experimentally investigate the degradation characteristics of the air cathode. The results of electrochemical tests reveal that the peak power density for the 25 cm2 cell with a new air cathode is 454 mW cm-2, which is twice as the value of the used air cathode. The electrochemical impedance analysis shows that both the charge transfer resistance and the mass transfer resistance of the used air cathodes have increased, suggesting that the catalyst surface area and gas diffusion coefficient have decreased significantly. Additionally, the microstructure and morphology of the catalytic layer (CL) and gas diffusion layer (GDL) are characterized by scanning electron microscopes (SEM). SEM results confirm that the micropores in CL and GDL of the used air cathode are seriously clogged, and many catalyst particles are lost. Therefore, the performance degradation is mainly due to the clogging of micropores and loss of catalyst particles. Furthermore, hypotheses of degradation mechanism and mitigation strategies for GDL and CL are discussed briefly.

  4. Effect of Particle Size and Operating Conditions on Pt3Co PEMFC Cathode Catalyst Durability

    DOE PAGESBeta

    Gummalla, Mallika; Ball, Sarah; Condit, David; Rasouli, Somaye; Yu, Kang; Ferreira, Paulo; Myers, Deborah; Yang, Zhiwei

    2015-05-29

    The initial performance and decay trends of polymer electrolyte membrane fuel cells (PEMFC) cathodes with Pt3Co catalysts of three mean particle sizes (4.9 nm, 8.1 nm, and 14.8 nm) with identical Pt loadings are compared. Even though the cathode based on 4.9 nm catalyst exhibited the highest initial electrochemical surface area (ECA) and mass activity, the cathode based on 8.1 nm catalyst showed better initial performance at high currents. Owing to the low mass activity of the large particles, the initial performance of the 14.8 nm Pt3Co-based electrode was the lowest. The performance decay rate of the electrodes with themore » smallest Pt3Co particle size was the highest and that of the largest Pt3Co particle size was lowest. Interestingly, with increasing number of decay cycles (0.6 to 1.0 V, 50 mV/s), the relative improvement in performance of the cathode based on 8.1 nm Pt3Co over the 4.9 nm Pt3Co increased, owing to better stability of the 8.1 nm catalyst. The electron microprobe analysis (EMPA) of the decayed membrane-electrode assembly (MEA) showed that the amount of Co in the membrane was lower for the larger particles, and the platinum loss into the membrane also decreased with increasing particle size. This suggests that the higher initial performance at high currents with 8.1 nm Pt3Co could be due to lower contamination of the ionomer in the electrode. Furthermore, lower loss of Co from the catalyst with increased particle size could be one of the factors contributing to the stability of ECA and mass activity of electrodes with larger cathode catalyst particles. To delineate the impact of particle size and alloy effects, these results are compared with prior work from our research group on size effects of pure platinum catalysts. The impact of PEMFC operating conditions, including upper potential, relative humidity, and temperature on the alloy catalyst decay trends, along with the EMPA analysis of the decayed MEAs, are reported.« less

  5. Durability and performance optimization of cathode materials for fuel cells

    NASA Astrophysics Data System (ADS)

    Colon-Mercado, Hector Rafael

    The primary objective of this dissertation is to develop an accelerated durability test (ADT) for the evaluation of cathode materials for fuel cells. The work has been divided in two main categories, namely high temperature fuel cells with emphasis on the Molten Carbonate Fuel Cell (MCFC) cathode current collector corrosion problems and low temperature fuel cells in particular Polymer Electrolyte Fuel Cell (PEMFC) cathode catalyst corrosion. The high operating temperature of MCFC has given it benefits over other fuel cells. These include higher efficiencies (>50%), faster electrode kinetics, etc. At 650°C, the theoretical open circuit voltage is established, providing low electrode overpotentials without requiring any noble metal catalysts and permitting high electrochemical efficiency. The waste heat is generated at sufficiently high temperatures to make it useful as a co-product. However, in order to commercialize the MCFC, a lifetime of 40,000 hours of operation must be achieved. The major limiting factor in the MCFC is the corrosion of cathode materials, which include cathode electrode and cathode current collector. In the first part of this dissertation the corrosion characteristics of bare, heat-treated and cobalt coated titanium alloys were studied using an ADT and compared with that of state of the art current collector material, SS 316. PEMFCs are the best choice for a wide range of portable, stationary and automotive applications because of their high power density and relatively low-temperature operation. However, a major impediment in the commercialization of the fuel cell technology is the cost involved due to the large amount of platinum electrocatalyst used in the cathode catalyst. In an effort to increase the power and decrease the cathode cost in polymer electrolyte fuel cell (PEMFC) systems, Pt-alloy catalysts were developed to increase its activity and stability. Extensive research has been conducted in the area of new alloy development and

  6. N-type Cu2O doped activated carbon as catalyst for improving power generation of air cathode microbial fuel cells.

    PubMed

    Zhang, Xi; Li, Kexun; Yan, Pengyu; Liu, Ziqi; Pu, Liangtao

    2015-01-01

    A novel n-type Cu2O doped activated carbon (AC) air cathode (Cu/AC) was developed as an alternative to Pt electrode for oxygen reduction in microbial fuel cells (MFCs). The maximum power density of MFCs using this novel air cathode was as high as 1390±76mWm(-2), almost 59% higher than the bare AC air cathode. Specifically, the resistance including total resistance and charge transfer resistance significantly decreased comparing to the control. Tafel curve also showed the faster electro-transfer kinetics of Cu/AC with exchange current density of 1.03×10(-3)Acm(-2), which was 69% higher than the control. Ribbon-like Cu2O was deposited on the surface of AC with the mesopore surface area increasing. Cubic Cu2O crystals exclusively expose (111) planes with the interplanar crystal spacing of 2.48Å, which was the dominate active sites for oxygen reduction reaction (ORR). N-type Cu2O with oxygen vacancies played crucial roles in electrochemical catalytic activity. PMID:25863207

  7. Catalyst and electrode research for phosphoric acid fuel cells

    NASA Technical Reports Server (NTRS)

    Antoine, A. C.; King, R. B.

    1987-01-01

    An account is given of the development status of phosphoric acid fuel cells' high performance catalyst and electrode materials. Binary alloys have been identified which outperform the baseline platinum catalyst; it has also become apparent that pressurized operation is required to reach the desired efficiencies, calling in turn for the use of graphitized carbon blacks in the role of catalyst supports. Efforts to improve cell performance and reduce catalyst costs have led to the investigation of a class of organometallic cathode catalysts represented by the tetraazaannulenes, and a mixed catalyst which is a mixture of carbons catalyzed with an organometallic and a noble metal.

  8. Degradation of Ionic Pathway in PEM Fuel Cell Cathode

    SciTech Connect

    Park, Seh Kyu; Shao, Yuyan; Wan, Haiying; Viswanathan, Vilayanur V.; Towne, Silas A.; Rieke, Peter C.; Liu, Jun; Wang, Yong

    2011-11-12

    The degradation of the ionic pathway throughout the catalyst layer in proton exchange membrane fuel cells was studied under an accelerated stress test of catalyst support (potential hold at 1.2 V). Electrochemical behaviors of the cathode based on graphitic mesoporous carbon supported Pt catalyst were examined using electrochemical impedance spectroscopy and cyclic voltammetry. Impedance data were plotted and expressed in the complex capacitance form to determine useful parameters in the transmission line model: the double-layer capacitance, peak frequency, and ionic resistance. Electrochemical surface area and hydrogen crossover current through the membrane were estimated from cyclic voltammogram, while cathode Faradaic resistance was compared with ionic resistance as a function of test time. It was observed that during an accelerated stress test of catalyst support, graphitic mesoporous carbon becomes hydrophilic which increases interfacial area between the ionomer and the catalyst up to 100 h. However, the ionic resistance in the catalyst layer drastically increases after 100 h with further carbon support oxidation. The underlying mechanism has been studied and it was found that significant degradation of ionic pathway throughout the catalyst layer due to catalyst support corrosion induces uneven hydration and mechanical stress in the ionomer.

  9. Cathodes for ceria-based fuel cells

    SciTech Connect

    Doshi, R.; Krumpelt, M.; Ricvhards, V.L.

    1997-08-01

    Work is underway to develop a solid oxide fuel cell that has a ceria-based electrolyte and operates at lower temperatures (500-600{degrees}C) than conventional zirconia-based cells. At present the performance of this ceria-based solid oxide fuel cell is limited by the polarization of conventional cathode materials. The performance of alternative cathodes was measured by impedance spectroscopy and dc polarization. The performance was found to improve by using a thin dense interface layer and by using two-phase cathodes with an electrolyte and an electronic phase. The cathode performance was also found to increase with increasing ionic conductivity for single phase cathodes.

  10. Cathode for aluminum producing electrolytic cell

    DOEpatents

    Brown, Craig W.

    2004-04-13

    A method of producing aluminum in an electrolytic cell comprising the steps of providing an anode in a cell, preferably a non-reactive anode, and also providing a cathode in the cell, the cathode comprised of a base material having low electrical conductivity reactive with molten aluminum to provide a highly electrically conductive layer on the base material. Electric current is passed from the anode to the cathode and alumina is reduced and aluminum is deposited at the cathode. The cathode base material is selected from boron carbide, and zirconium oxide.

  11. Cathodic oxygen reduction catalyzed by bacteria in microbial fuel cells.

    PubMed

    Rabaey, Korneel; Read, Suzanne T; Clauwaert, Peter; Freguia, Stefano; Bond, Philip L; Blackall, Linda L; Keller, Jurg

    2008-05-01

    Microbial fuel cells (MFCs) have the potential to combine wastewater treatment efficiency with energetic efficiency. One of the major impediments to MFC implementation is the operation of the cathode compartment, as it employs environmentally unfriendly catalysts such as platinum. As recently shown, bacteria can facilitate sustainable and cost-effective cathode catalysis for nitrate and also oxygen. Here we describe a carbon cathode open to the air, on which attached bacteria catalyzed oxygen reduction. The bacteria present were able to reduce oxygen as the ultimate electron acceptor using electrons provided by the solid-phase cathode. Current densities of up to 2.2 A m(-2) cathode projected surface were obtained (0.303+/-0.017 W m(-2), 15 W m(-3) total reactor volume). The cathodic microbial community was dominated by Sphingobacterium, Acinetobacter and Acidovorax sp., according to 16S rRNA gene clone library analysis. Isolates of Sphingobacterium sp. and Acinetobacter sp. were obtained using H(2)/O(2) mixtures. Some of the pure culture isolates obtained from the cathode showed an increase in the power output of up to three-fold compared to a non-inoculated control, that is, from 0.015+/-0.001 to 0.049+/-0.025 W m(-2) cathode projected surface. The strong decrease in activation losses indicates that bacteria function as true catalysts for oxygen reduction. Owing to the high overpotential for non-catalyzed reduction, oxygen is only to a limited extent competitive toward the electron donor, that is, the cathode. Further research to refine the operational parameters and increase the current density by modifying the electrode surface and elucidating the bacterial metabolism is warranted. PMID:18288216

  12. Optimization of carbon-supported platinum cathode catalysts for DMFC operation.

    SciTech Connect

    Zhu, Y.; Brosha, E. L.; Zelenay, P.

    2002-01-01

    In this paper, we describe performance and optimization of carbon-supported cathode catalysts at low platinum loading. We find that at a loading below 0.6 mg cm-2 carbon-supported platinum outperforms platinum black as a DMFC cathode catalyst. A catalyst with a 1:1 volume ratio of the dry NafionTM to the electronically conducting phase (platinum plus carbon support) provides the best performance in oxygen reduction reaction. Thanks to improved catalyst utilization, carbon-supported catalysts with a platinum content varying from 40 wt% to 80 wt% deliver very good DMFC performance, even at relatively modest precious metal loadings investigated in this work.

  13. Corrosion testing of candidates for the alkaline fuel cell cathode

    NASA Technical Reports Server (NTRS)

    Singer, Joseph; Fielder, William L.

    1990-01-01

    Current/voltage data have been obtained for specially made corrosion electrodes of some oxides and of gold materials for the purpose of developing a screening test of catalysts and supports for use at the cathode of the alkaline fuel cell. The data consist of measurements of current at fixed potentials and cyclic voltammograms. These data will have to be correlated with longtime performance data in order to evaluate fully this approach to corrosion screening.

  14. Ruthenium nanocrystals as cathode catalysts for lithium-oxygen batteries with a superior performance

    PubMed Central

    Sun, Bing; Munroe, Paul; Wang, Guoxiu

    2013-01-01

    The key factor to improve the electrochemical performance of Li-O2 batteries is to find effective cathode catalysts to promote the oxygen reduction and oxygen evolution reactions. Herein, we report the synthesis of an effective cathode catalyst of ruthenium nanocrystals supported on carbon black substrate by a surfactant assisting method. The as-prepared ruthenium nanocrystals exhibited an excellent catalytic activity as cathodes in Li-O2 batteries with a high reversible capacity of about 9,800 mAh g−1, a low charge-discharge over-potential (about 0.37 V), and an outstanding cycle performance up to 150 cycles (with a curtaining capacity of 1,000 mAh g−1). The electrochemical testing shows that ruthenium nanocrystals can significantly reduce the charge potential comparing to carbon black catalysts, which demonstrated that ruthenium based nanomaterials could be effective cathode catalysts for high performance lithium- O2 batteries. PMID:23873349

  15. Impact of liquid water on oxygen reaction in cathode catalyst layer of proton exchange membrane fuel cell: A simple and physically sound model

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaoxian; Gao, Yuan

    2016-06-01

    When cells work at high current density, liquid water accumulates in their catalyst layer (CL) and the gaseous oxygen could dissolve into the water and the ionomer film simultaneously; their associated dissolved concentrations in equilibrium with the gaseous oxygen are also different. Based on a CL acquired using tomography, we present new methods in this paper to derive agglomerate models for partly saturated CL by viewing the movement and reaction of the dissolved oxygen in the two liquids (water and ionomer) and the agglomerate as two independent random processes. Oxygen dissolved in the water moves differently from oxygen dissolved in the ionomer, and to make the analysis tractable, we use an average distribution function to describe the average movement of all dissolved oxygen. A formula is proposed to describe this average distribution function, which, in combination with the exponential distribution assumed in the literature for oxygen reaction, leads to a simple yet physically sound agglomerate model. The model has three parameters which can be directly calculated from CL structure rather than by calibration. We explain how to calculate these parameters under different water contents for a given CL structure, and analyse the impact of liquid water on cell performance.

  16. Organometallic catalysts for primary phosphoric acid fuel cells

    NASA Technical Reports Server (NTRS)

    Walsh, Fraser

    1987-01-01

    A continuing effort by the U.S. Department of Energy to improve the competitiveness of the phosphoric acid fuel cell by improving cell performance and/or reducing cell cost is discussed. Cathode improvement, both in performance and cost, available through the use of a class of organometallic cathode catalysts, the tetraazaannulenes (TAAs), was investigated. A new mixed catalyst was identified which provides improved cathode performance without the need for the use of a noble metal. This mixed catalyst was tested under load for 1000 hr. in full cell at 160 to 200 C in phosphoric acid H3PO4, and was shown to provide stable performance. The mixed catalyst contains an organometallic to catalyze electroreduction of oxygen to hydrogen peroxide and a metal to catalyze further electroreduction of the hydrogen peroxide to water. Cathodes containing an exemplar mixed catalyst (e.g., Co bisphenyl TAA/Mn) operate at approximately 650 mV vs DHE in 160 C, 85% H3PO4 with oxygen as reactant. In developing this mixed catalyst, a broad spectrum of TAAs were prepared, tested in half-cell and in a rotating ring-disk electrode system. TAAs found to facilitate the production of hydrogen peroxide in electroreduction were shown to be preferred TAAs for use in the mixed catalyst. Manganese (Mn) was identified as a preferred metal because it is capable of catalyzing hydrogen peroxide electroreduction, is lower in cost and is of less strategic importance than platinum, the cathode catalyst normally used in the fuel cell.

  17. Organometallic catalysts for primary phosphoric acid fuel cells

    NASA Astrophysics Data System (ADS)

    Walsh, Fraser

    1987-03-01

    A continuing effort by the U.S. Department of Energy to improve the competitiveness of the phosphoric acid fuel cell by improving cell performance and/or reducing cell cost is discussed. Cathode improvement, both in performance and cost, available through the use of a class of organometallic cathode catalysts, the tetraazaannulenes (TAAs), was investigated. A new mixed catalyst was identified which provides improved cathode performance without the need for the use of a noble metal. This mixed catalyst was tested under load for 1000 hr. in full cell at 160 to 200 C in phosphoric acid H3PO4, and was shown to provide stable performance. The mixed catalyst contains an organometallic to catalyze electroreduction of oxygen to hydrogen peroxide and a metal to catalyze further electroreduction of the hydrogen peroxide to water. Cathodes containing an exemplar mixed catalyst (e.g., Co bisphenyl TAA/Mn) operate at approximately 650 mV vs DHE in 160 C, 85% H3PO4 with oxygen as reactant. In developing this mixed catalyst, a broad spectrum of TAAs were prepared, tested in half-cell and in a rotating ring-disk electrode system. TAAs found to facilitate the production of hydrogen peroxide in electroreduction were shown to be preferred TAAs for use in the mixed catalyst. Manganese (Mn) was identified as a preferred metal because it is capable of catalyzing hydrogen peroxide electroreduction, is lower in cost and is of less strategic importance than platinum, the cathode catalyst normally used in the fuel cell.

  18. Fuel cell development for transportation: Catalyst development

    SciTech Connect

    Doddapaneni, N.; Ingersoll, D.

    1996-12-31

    Fuel cells are being considered as alternative power sources for transportation and stationary applications. The degradation of commonly used electrode catalysts (e.g. Pt, Ag, and others) and corrosion of carbon substrates are making commercialization of fuel cells incorporating present day technologies economically problematic. Furthermore, due to the instability of the Pt catalyst, the performance of fuel cells declines on long-term operation. When methanol is used as the fuel, a voltage drop, as well as significant thermal management problems can be encountered, the later being due to chemical oxidation of methanol at the platinized carbon at the cathode. Though extensive work was conducted on platinized electrodes for both the oxidation and reduction reactions, due to the problems mentioned above, fuel cells have not been fully developed for widespread commercial use. Several investigators have previously evaluated metal macrocyclic complexes as alternative catalysts to Pt and Pt/Ru in fuel cells. Unfortunately, though they have demonstrated catalytic activity, these materials were found to be unstable on long term use in the fuel cell environment. In order to improve the long-term stability of metal macrocyclic complexes, we have chemically bonded these complexes to the carbon substrate, thereby enhancing their catalytic activity as well as their chemical stability in the fuel cell environment. We have designed, synthesized, and evaluated these catalysts for O{sub 2} reduction, H{sub 2} oxidation, and direct methanol oxidation in Proton Exchange Membrane (PEM) and aqueous carbonate fuel cells. These catalysts exhibited good catalytic activity and long-term stability. In this paper we confine our discussion to the initial performance results of some of these catalysts in H{sub 2}/O{sub 2} PEM fuel cells, including their long-term performance characteristics as well as CO poisoning effects on these catalysts.

  19. Iron- and nitrogen-functionalized graphene as a non-precious metal catalyst for enhanced oxygen reduction in an air-cathode microbial fuel cell

    NASA Astrophysics Data System (ADS)

    Li, Sizhe; Hu, Yongyou; Xu, Qian; Sun, Jian; Hou, Bin; Zhang, Yaping

    2012-09-01

    In this work, iron- and nitrogen-functionalized graphene (Fe-N-G) as a non-precious metal catalyst is synthesized via a facile method of thermal treatment of a mixture of Fe salt, graphitic carbon nitride (g-C3N4) and chemically reduced graphene. The electrocatalytic activity of the prepared catalysts toward oxygen reduction reaction (ORR) evaluated by using linear sweep voltammetry tests shows that the Fe-N-G catalyst has more positive onset potential and increased reduction current densities as compared to the pristine graphene (P-G) catalyst, indicating an enhanced ORR activity of the Fe-N-G catalyst. More importantly, the Fe-N-G-MFC achieves the highest power density of 1149.8 mW m-2, which is ∼2.1 times of that generated with the Pt/C-MFC (561.1 mW m-2) and much higher than that of the P-G-MFC (109 mW m-2). These results demonstrate that the Fe-N-G catalyst can hold the promise of being an excellent alternative to the costly Pt catalyst for practical MFC applications.

  20. Cathode for molten carbonate fuel cell

    DOEpatents

    Kaun, Thomas D.; Mrazek, Franklin C.

    1990-01-01

    A porous sintered cathode for a molten carbonate fuel cell and method of making same, the cathode including a skeletal structure of a first electronically conductive material slightly soluble in the electrolyte present in the molten carbonate fuel cell covered by fine particles of a second material of possibly lesser electronic conductivity insoluble in the electrolyte present in the molten carbonate fuel cell, the cathode having a porosity in the range of from about 60% to about 70% at steady-state cell operating conditions consisting of both macro-pores and micro-pores.

  1. Enhanced Oxygen and Hydroxide Transport in a Cathode Interface by Efficient Antibacterial Property of a Silver Nanoparticle-Modified, Activated Carbon Cathode in Microbial Fuel Cells.

    PubMed

    Li, Da; Qu, Youpeng; Liu, Jia; Liu, Guohong; Zhang, Jie; Feng, Yujie

    2016-08-17

    A biofilm growing on an air cathode is responsible for the decreased performance of microbial fuel cells (MFCs). For the undesired biofilm to be minimized, silver nanoparticles were synthesized on activated carbon as the cathodic catalyst (Ag/AC) in MFCs. Ag/AC enhanced maximum power density by 14.6% compared to that of a bare activated carbon cathode (AC) due to the additional silver catalysis. After operating MFCs over five months, protein content on the Ag/AC cathode was only 38.3% of that on the AC cathode, which resulted in a higher oxygen concentration diffusing through the Ag/AC cathode. In addition, a lower pH increment (0.2 units) was obtained near the Ag/AC catalyst surface after biofouling compared to 0.8 units of the AC cathode, indicating that less biofilm on the Ag/AC cathode had a minor resistance on hydroxide transported from the catalyst layer interfaces to the bulk solution. Therefore, less decrements of the Ag/AC activity and MFC performance were obtained. This result indicated that accelerated transport of oxygen and hydroxide, benefitting from the antibacterial property of the cathode, could efficiently maintain higher cathode stability during long-term operation. PMID:27441786

  2. ETEM observation of Pt/C electrode catalysts in a moisturized cathode atmosphere

    NASA Astrophysics Data System (ADS)

    Yoshida, K.; Zhang, X.; Tanaka, N.; Boyes, E. D.; Gai, P. L.

    2014-06-01

    There have been reports of challenges in designing platinum carbon (Pt/C) electrode catalysts for PEMFC. Pt/C electrode catalysts deactivate much faster on the cathode (in moisturized O2) than on the anode (in H2). To understand influences of moisture and oxygen on the deactivation of the Pt/C catalysts in proton-exchange-membrane fuel cells (PEMFCs), spherical-aberration-corrected environmental transmission electron microscopy (AC-ETEM) was applied with a high-speed CCD camera. Structural changes of the Pt/C electrode catalysts were dynamically recorded in moisturized nitrogen, oxygen and hydrogen. The mass spectrometry confirmed the moisture content (between 5 to 30 %) of nitrogen driving gas through a humidifier. Coalescence of platinum nanoparticles (D = 3.24 nm) was carefully evaluated in pure N2 and moisturized N2 atmosphere. The Pt/C showed considerable structural weakness in a moisturized N2 atmosphere. Comparable results obtained by AC-ETEM in different gas atmospheres also suggested ways to improve the oxygen reduction reaction (ORR). In this paper, the deactivation process due to moisture (hydroxylation) of carbon supports is discussed using for comparison the movement of platinum nanoparticles measured in moisturized nitrogen and pure nitrogen atmospheres.

  3. Carbon support oxidation in PEM fuel cell cathodes

    NASA Astrophysics Data System (ADS)

    Maass, S.; Finsterwalder, F.; Frank, G.; Hartmann, R.; Merten, C.

    Oxidation of the cathode carbon catalyst support in polymer electrolyte fuel cells (PEMFC) has been examined. For this purpose platinum supported electrodes and pure carbon electrodes were fabricated and tested in membrane-electrode-assemblies (MEAs) in air and nitrogen atmosphere. The in situ experiments account for the fuel cell environment characterized by the presence of a solid electrolyte and water in the gas and liquid phases. Cell potential transients occurring during automotive fuel cell operation were simulated by dynamic measurements. Corrosion rates were calculated from CO 2 and CO concentrations in the cathode exhaust measured by non-dispersive infrared spectroscopy (NDIR). Results from these potentiodynamic measurements indicate that different potential regimes relevant for carbon oxidation can be distinguished. Carbon corrosion rates were found to be higher under dynamic operation and to strongly depend on electrode history. These characteristics make it difficult to predict corrosion rates accurately in an automotive drive cycle.

  4. Functionally Graded Cathodes for Solid Oxide Fuel Cells

    SciTech Connect

    Lei Yang; Ze Liu; Shizhone Wang; Jaewung Lee; Meilin Liu

    2008-04-30

    The main objective of this DOE project is to demonstrate that the performance and long-term stability of the state-of-the-art LSCF cathode can be enhanced by a catalytically active coating (e.g., LSM or SSC). We have successfully developed a methodology for reliably evaluating the intrinsic surface catalytic properties of cathode materials. One of the key components of the test cell is a dense LSCF film, which will function as the current collector for the electrode material under evaluation to eliminate the effect of ionic and electronic transport. Since it is dense, the effect of geometry would be eliminated as well. From the dependence of the electrode polarization resistance on the thickness of a dense LSCF electrode and on partial pressure of oxygen, we have confirmed that the surface catalytic activity of LSCF limits the performances of LSCF-based cathodes. Further, we have demonstrated, using test cells of different configurations, that the performance of LSCF-based electrodes can be significantly enhanced by infiltration of a thin film of LSM or SSC. In addition, the stability of LSCF-based cathodes was also improved by infiltration of LSM or SSC. While the concept feasibility of the electrode architecture is demonstrated, many details are yet to be determined. For example, it is not clear how the surface morphology, composition, and thickness of the coatings change under operating conditions over time, how these changes influence the electrochemical behavior of the cathodes, and how to control the microscopic details of the coatings in order to optimize the performance. The selection of the catalytic materials as well as the detailed microstructures of the porous LSCF and the catalyst layer may critically impact the performance of the proposed cathodes. Further, other fundamental questions still remain; it is not clear why the degradation rates of LSCF cathodes are relatively high, why a LSM coating improves the stability of LSCF cathodes, which catalysts

  5. Catalyst inks and method of application for direct methanol fuel cells

    DOEpatents

    Zelenay, Piotr; Davey, John; Ren, Xiaoming; Gottesfeld, Shimshon; Thomas, Sharon C.

    2004-02-24

    Inks are formulated for forming anode and cathode catalyst layers and applied to anode and cathode sides of a membrane for a direct methanol fuel cell. The inks comprise a Pt catalyst for the cathode and a Pt--Ru catalyst for the anode, purified water in an amount 4 to 20 times that of the catalyst by weight, and a perfluorosulfonic acid ionomer in an amount effective to provide an ionomer content in the anode and cathode surfaces of 20% to 80% by volume. The inks are prepared in a two-step process while cooling and agitating the solutions. The final solution is placed in a cooler and continuously agitated while spraying the solution over the anode or cathode surface of the membrane as determined by the catalyst content.

  6. Cells having cathodes containing polycarbon disulfide materials

    DOEpatents

    Okamoto, Yoshi; Skotheim, Terje A.; Lee, Hung S.

    1995-08-15

    The present invention relates to an electric current producing cell which contains an anode, a cathode having as a cathode-active material one or more carbon-sulfur compounds of the formula (CS.sub.x).sub.n, in which x takes values from 1.2 to 2.3 and n is greater or equal to 2, and where the redox process does not involve polymerization and de-polymerization by forming and breaking S--S bonds in the polymer backbone. The cell also contains an electrolyte which is chemically inert with respect to the anode and the cathode.

  7. Cells having cathodes containing polycarbon disulfide materials

    DOEpatents

    Okamoto, Y.; Skotheim, T.A.; Lee, H.S.

    1995-08-15

    The present invention relates to an electric current producing cell which contains an anode, a cathode having as a cathode-active material one or more carbon-sulfur compounds of the formula (CS{sub x}){sub n}, in which x takes values from 1.2 to 2.3 and n is greater or equal to 2, and where the redox process does not involve polymerization and de-polymerization by forming and breaking S--S bonds in the polymer backbone. The cell also contains an electrolyte which is chemically inert with respect to the anode and the cathode. 5 figs.

  8. Effect of Particle Size and Operating Conditions on Pt3Co PEMFC Cathode Catalyst Durability

    SciTech Connect

    Gummalla, Mallika; Ball, Sarah; Condit, David; Rasouli, Somaye; Yu, Kang; Ferreira, Paulo; Myers, Deborah; Yang, Zhiwei

    2015-05-29

    The initial performance and decay trends of polymer electrolyte membrane fuel cells (PEMFC) cathodes with Pt3Co catalysts of three mean particle sizes (4.9 nm, 8.1 nm, and 14.8 nm) with identical Pt loadings are compared. Even though the cathode based on 4.9 nm catalyst exhibited the highest initial electrochemical surface area (ECA) and mass activity, the cathode based on 8.1 nm catalyst showed better initial performance at high currents. Owing to the low mass activity of the large particles, the initial performance of the 14.8 nm Pt3Co-based electrode was the lowest. The performance decay rate of the electrodes with the smallest Pt3Co particle size was the highest and that of the largest Pt3Co particle size was lowest. Interestingly, with increasing number of decay cycles (0.6 to 1.0 V, 50 mV/s), the relative improvement in performance of the cathode based on 8.1 nm Pt3Co over the 4.9 nm Pt3Co increased, owing to better stability of the 8.1 nm catalyst. The electron microprobe analysis (EMPA) of the decayed membrane-electrode assembly (MEA) showed that the amount of Co in the membrane was lower for the larger particles, and the platinum loss into the membrane also decreased with increasing particle size. This suggests that the higher initial performance at high currents with 8.1 nm Pt3Co could be due to lower contamination of the ionomer in the electrode. Furthermore, lower loss of Co from the catalyst with increased particle size could be one of the factors contributing to the stability of ECA and mass activity of electrodes with larger cathode catalyst particles. To delineate the impact of particle size and alloy effects, these results are compared with prior work from our research group on size effects of pure platinum catalysts. The impact of PEMFC operating conditions, including upper potential, relative humidity, and temperature on the alloy catalyst decay trends, along with the EMPA analysis

  9. Cathodes for lithium-air battery cells with acid electrolytes

    DOEpatents

    Xing, Yangchuan; Huang, Kan; Li, Yunfeng

    2016-07-19

    In various embodiments, the present disclosure provides a layered metal-air cathode for a metal-air battery. Generally, the layered metal-air cathode comprises an active catalyst layer, a transition layer bonded to the active catalyst layer, and a backing layer bonded to the transition layer such that the transition layer is disposed between the active catalyst layer and the backing layer.

  10. Cell performance of Pd-Sn catalyst in passive direct methanol alkaline fuel cell using anion exchange membrane

    NASA Astrophysics Data System (ADS)

    Kim, Jandee; Momma, Toshiyuki; Osaka, Tetsuya

    Direct methanol alkaline fuel cell (DMAFC) using anion exchange membrane (AEM) was operated in passive condition. Cell with AEM exhibits a higher open circuit voltage (OCV) and superior cell performance than those in cell using Nafion. From the concentration dependences of methanol, KOH in fuel and ionomer in anode catalyst layer, it is found that the key factors are to improve the ionic conductivity at the anode and to form a favorable ion conductive path in catalyst layer in order to enhance the cell performance. In addition, by using home-made Pd-Sn/C catalyst as a cathode catalyst on DMAFC, the membrane electrode assembly (MEA) using Pd-Sn/C catalyst as cathode exhibits the higher performance than the usual commercially available Pt/C catalyst in high methanol concentration. Therefore, the Pd-Sn/C catalyst with high tolerance for methanol is expected as the promising oxygen reduction reaction (ORR) catalyst in DMAFC.

  11. Improvement in high temperature proton exchange membrane fuel cells cathode performance with ammonium carbonate

    NASA Astrophysics Data System (ADS)

    Song, Ying; Wei, Yu; Xu, Hui; Williams, Minkmas; Liu, Yuxiu; Bonville, Leonard J.; Russell Kunz, H.; Fenton, James M.

    Proton exchange membrane (PEM) fuel cells with optimized cathode structures can provide high performance at higher temperature (120 °C). A "pore-forming" material, ammonium carbonate, applied in the unsupported Pt cathode catalyst layer of a high temperature membrane electrode assembly enhanced the catalyst activity and minimized the mass-transport limitations. The ammonium carbonate amount and Nafion ® loading in the cathode were optimized for performance at two conditions: 80 °C cell temperature with 100% anode/75% cathode R.H. and 120 °C cell temperature with 35% anode/35% cathode R.H., both under ambient pressure. A cell with 20 wt.% ammonium carbonate and 20 wt.% Nafion ® operating at 80 °C and 120 °C presented the maximum cell performance. Hydrogen/air cell voltages at a current density of 400 mA cm -2 using the Ionomem/UConn membrane as the electrolyte with a cathode platinum loading of 0.5 mg cm -2 were 0.70 V and 0.57 V at the two conditions, respectively. This was a 19% cell voltage increase over a cathode without the "pore-forming" ammonium carbonate at the 120 °C operating condition.

  12. Polyaniline-derived non-precious catalyst for the polymer electrolyte fuel cathode

    SciTech Connect

    Wu, Gang; Chen, Zhongwei; Garzon, Fernando; Zelenay, Piotr

    2008-01-01

    A novel polyaniline (PANI)-derived non-precious cathode catalyst was developed in this work, exhibiting remarkable activity (onset potential: 0.9 V, half-wave potential: 0.77 V) and selectivity (0.4 % H20 2 at 0.4 V). As a result, the generated current densities at high voltages associated with electrochemically kinetic activity can be achieved to 0.04 Acm-2 for 0.80V and 0.21 Acm-2 for 0.6 V, when air was used in fuel cell tests. MEA life test at a constant voltage of 0.4 V demonstrated a promising stability up to 450 hours, without obvious degradation. The current density during the test was measured around 0.32 A cm-2, a respectable performance for a cell with non-precious cathode, operated on air rather than oxygen. The possible active sites, related to pyridine- and pyrrole-like metal species were discussed according to presented XPS and XRD analysis.

  13. Improved Cathode Structure for a Direct Methanol Fuel Cell

    NASA Technical Reports Server (NTRS)

    Valdez, Thomas; Narayanan, Sekharipuram

    2005-01-01

    An improved cathode structure on a membrane/electrode assembly has been developed for a direct methanol fuel cell, in a continuing effort to realize practical power systems containing such fuel cells. This cathode structure is intended particularly to afford better cell performance at a low airflow rate. A membrane/electrode assembly of the type for which the improved cathode structure was developed (see Figure 1) is fabricated in a process that includes brush painting and spray coating of catalyst layers onto a polymer-electrolyte membrane and onto gas-diffusion backings that also act as current collectors. The aforementioned layers are then dried and hot-pressed together. When completed, the membrane/electrode assembly contains (1) an anode containing a fine metal black of Pt/Ru alloy, (2) a membrane made of Nafion 117 or equivalent (a perfluorosulfonic acid-based hydrophilic, proton-conducting ion-exchange polymer), (3) a cathode structure (in the present case, the improved cathode structure described below), and (4) the electrically conductive gas-diffusion backing layers, which are made of Toray 060(TradeMark)(or equivalent) carbon paper containing between 5 and 6 weight percent of poly(tetrafluoroethylene). The need for an improved cathode structure arises for the following reasons: In the design and operation of a fuel-cell power system, the airflow rate is a critical parameter that determines the overall efficiency, cell voltage, and power density. It is desirable to operate at a low airflow rate in order to obtain thermal and water balance and to minimize the size and mass of the system. The performances of membrane/electrode assemblies of prior design are limited at low airflow rates. Methanol crossover increases the required airflow rate. Hence, one way to reduce the required airflow rate is to reduce the effect of methanol crossover. Improvement of the cathode structure - in particular, addition of hydrophobic particles to the cathode - has been

  14. Multi-variable mathematical models for the air-cathode microbial fuel cell system

    DOE PAGESBeta

    Ou, Shiqi; Kashima, Hiroyuki; Aaron, Douglas S.; Regan, John M.; Mench, Matthew M.

    2016-03-10

    This research adopted the version control system into the model construction for the single chamber air-cathode microbial fuel cell (MFC) system, to understand the interrelation of biological, chemical, and electrochemical reactions. The anodic steady state model was used to consider the chemical species diffusion and electric migration influence to the MFC performance. In the cathodic steady state model, the mass transport and reactions in a multi-layer, abiotic cathode and multi-bacteria cathode biofilm were simulated. Transport of hydroxide was assumed for cathodic pH change. This assumption is an alternative to the typical notion of proton consumption during oxygen reduction to explainmore » elevated cathode pH. The cathodic steady state model provided the power density and polarization curve performance results that can be compared to an experimental MFC system. Another aspect we considered was the relative contributions of platinum catalyst and microbes on the cathode to the oxygen reduction reaction (ORR). We found simulation results showed that the biocatalyst in a cathode that includes a Pt/C catalyst likely plays a minor role in ORR, contributing up to 8% of the total power calculated by the models.« less

  15. Multi-variable mathematical models for the air-cathode microbial fuel cell system

    NASA Astrophysics Data System (ADS)

    Ou, Shiqi; Kashima, Hiroyuki; Aaron, Douglas S.; Regan, John M.; Mench, Matthew M.

    2016-05-01

    This research adopted the version control system into the model construction for the single chamber air-cathode microbial fuel cell (MFC) system, to understand the interrelation of biological, chemical, and electrochemical reactions. The anodic steady state model was used to consider the chemical species diffusion and electric migration influence to the MFC performance. In the cathodic steady state model, the mass transport and reactions in a multi-layer, abiotic cathode and multi-bacteria cathode biofilm were simulated. Transport of hydroxide was assumed for cathodic pH change. This assumption is an alternative to the typical notion of proton consumption during oxygen reduction to explain elevated cathode pH. The cathodic steady state model provided the power density and polarization curve performance results that can be compared to an experimental MFC system. Another aspect considered was the relative contributions of platinum catalyst and microbes on the cathode to the oxygen reduction reaction (ORR). Simulation results showed that the biocatalyst in a cathode that includes a Pt/C catalyst likely plays a minor role in ORR, contributing up to 8% of the total power calculated by the models.

  16. Tandem cathode for proton exchange membrane fuel cells.

    PubMed

    Siahrostami, Samira; Björketun, Mårten E; Strasser, Peter; Greeley, Jeff; Rossmeisl, Jan

    2013-06-21

    The efficiency of proton exchange membrane fuel cells is limited mainly by the oxygen reduction reaction at the cathode. The large cathodic overpotential is caused by correlations between binding energies of reaction intermediates in the reduction of oxygen to water. This work introduces a novel tandem cathode design where the full oxygen reduction, involving four electron-transfer steps, is divided into formation (equilibrium potential 0.70 V) followed by reduction (equilibrium potential 1.76 V) of hydrogen peroxide. The two part reactions contain only two electron-transfer steps and one reaction intermediate each, and they occur on different catalyst surfaces. As a result they can be optimized independently and the fundamental problem associated with the four-electron catalysis is avoided. A combination of density functional theory calculations and published experimental data is used to identify potentially active and selective materials for both catalysts. Co-porphyrin is recommended for the first step, formation of hydrogen peroxide, and three different metal oxides - SrTiO3(100), CaTiO3(100) and WO3(100) - are suggested for the subsequent reduction step. PMID:23661187

  17. Alternative cathodes for molten carbonate fuel cells

    SciTech Connect

    Bloom, I.; Lanagan, M.; Roche, M.F.; Krumpelt, M.

    1996-02-01

    Argonne National Laboratory (ANL) is developing advanced cathodes for pressurized operation of the molten carbonate fuel cell (MCFC). The present cathode, lithiated nickel oxide, tends to transport to the anode of the MCFC, where it is deposited as metallic nickel. The rate of transport increases with increasing CO{sub 2} pressure. This increase is due to an increased solubility of nickel oxide (NiO) in the molten carbonate electrolyte. An alternative cathode is lithium cobaltate (LiCoO{sub 2})-Solid solutions of LiCoO{sub 2} in LiFeO{sub 2} show promise for long-lived cathode materials. We have found that small additions of LiCoO{sub 2} to LiFeO{sub 2} markedly decrease the resistivity of the cathode material. Cells containing the LiCoO{sub 2}-LiFeO{sub 2} cathodes have stable performance for more than 2100 h of operation and display lower cobalt migration.

  18. A review on air cathodes for zinc-air fuel cells

    NASA Astrophysics Data System (ADS)

    Neburchilov, Vladimir; Wang, Haijiang; Martin, Jonathan J.; Qu, Wei

    This paper reviews the compositions, design and methods of fabrication of air cathodes for alkali zinc-air fuel cells (ZAFCs), one of the few successfully commercialized fuel cells. The more promising compositions for air cathodes are based on individual oxides, or mixtures of such, with a spinel, perovskite, or pyrochlore structure: MnO 2, Ag, Co 3O 4, La 2O 3, LaNiO 3, NiCo 2O 4, LaMnO 3, LaNiO 3, etc. These compositions provide the optimal balance of ORR activity and chemical stability in an alkali electrolyte. The sol-gel and reverse micelle methods supply the most uniform distribution of the catalyst on carbon and the highest catalyst BET surface area. It is shown that the design of the air cathode, including types of carbon black, binding agents, current collectors, Teflon membranes, thermal treatment of the GDL, and catalyst layers, has a strong effect on performance.

  19. Following ORR intermediates adsorbed on a Pt cathode catalyst during break-in of a PEM fuel cell by in operando X-ray absorption spectroscopy.

    PubMed

    Ramaker, D E; Korovina, A; Croze, V; Melke, J; Roth, C

    2014-07-21

    In operando X-ray absorption spectroscopy data using the Δμ X-ray Absorption Near Edge Spectroscopy (XANES) analysis procedure is used to follow the ORR intermediate adsorbate coverage on a working catalyst in a PEMFC during initial activation and break-in. The adsorbate coverage and log i (Tafel) curves reveal a strong correlation, i.e., an increase in adsorbate intermediate coverage poisons Pt sites thereby decreasing the current. A decrease in Pt-O bond strength commensurate with decrease in potential causes a sequence of different dominant adsorbate volcano curves to exist, namely first O, then OH, and then OOH exactly as predicted by the different ORR kinetics mechanisms. During break-in, the incipient O coverage coming from exposure to air during storage and MEA preparation is rather quickly removed, compared to the slower and more subtle nanoparticle morphological changes, such as the rounding of the Pt nanoparticle edges/corners and smoothing of the planar surfaces, driven by the nanoparticle's tendency to lower its surface energy. These morphological changes increase the Pt-Pt average coordination number, decrease the average Pt-O bond strength, and thereby decrease the coverage of ORR intermediates, allowing increase in the current. PMID:24664398

  20. Cathode for an electrochemical cell

    DOEpatents

    Bates, John B.; Dudney, Nancy J.; Gruzalski, Greg R.; Luck, Christopher F.

    2001-01-01

    Described is a thin-film battery, especially a thin-film microbattery, and a method for making same having application as a backup or primary integrated power source for electronic devices. The battery includes a novel electrolyte which is electrochemically stable and does not react with the lithium anode and a novel vanadium oxide cathode. Configured as a microbattery, the battery can be fabricated directly onto a semiconductor chip, onto the semiconductor die or onto any portion of the chip carrier. The battery can be fabricated to any specified size or shape to meet the requirements of a particular application. The battery is fabricated of solid state materials and is capable of operation between -15.degree. C. and 150.degree. C.

  1. On the actual cathode mixed potential in direct methanol fuel cells

    NASA Astrophysics Data System (ADS)

    Zago, M.; Bisello, A.; Baricci, A.; Rabissi, C.; Brightman, E.; Hinds, G.; Casalegno, A.

    2016-09-01

    Methanol crossover is one of the most critical issues hindering commercialization of direct methanol fuel cells since it leads to waste of fuel and significantly affects cathode potential, forming a so-called mixed potential. Unfortunately, due to the sluggish anode kinetics, it is not possible to obtain a reliable estimation of cathode potential by simply measuring the cell voltage. In this work we address this limitation, quantifying the mixed potential by means of innovative open circuit voltage (OCV) tests with a methanol-hydrogen mixture fed to the anode. Over a wide range of operating conditions, the resulting cathode overpotential is between 250 and 430 mV and is strongly influenced by methanol crossover. We show using combined experimental and modelling analysis of cathode impedance that the methanol oxidation at the cathode mainly follows an electrochemical pathway. Finally, reference electrode measurements at both cathode inlet and outlet provide a local measurement of cathode potential, confirming the reliability of the innovative OCV tests and permitting the evaluation of cathode potential up to typical operating current. At 0.25 A cm-2 the operating cathode potential is around 0.85 V and the Ohmic drop through the catalyst layer is almost 50 mV, which is comparable to that in the membrane.

  2. One-dimensional manganese-cobalt oxide nanofibres as bi-functional cathode catalysts for rechargeable metal-air batteries

    PubMed Central

    Jung, Kyu-Nam; Hwang, Soo Min; Park, Min-Sik; Kim, Ki Jae; Kim, Jae-Geun; Dou, Shi Xue; Kim, Jung Ho; Lee, Jong-Won

    2015-01-01

    Rechargeable metal-air batteries are considered a promising energy storage solution owing to their high theoretical energy density. The major obstacles to realising this technology include the slow kinetics of oxygen reduction and evolution on the cathode (air electrode) upon battery discharging and charging, respectively. Here, we report non-precious metal oxide catalysts based on spinel-type manganese-cobalt oxide nanofibres fabricated by an electrospinning technique. The spinel oxide nanofibres exhibit high catalytic activity towards both oxygen reduction and evolution in an alkaline electrolyte. When incorporated as cathode catalysts in Zn-air batteries, the fibrous spinel oxides considerably reduce the discharge-charge voltage gaps (improve the round-trip efficiency) in comparison to the catalyst-free cathode. Moreover, the nanofibre catalysts remain stable over the course of repeated discharge-charge cycling; however, carbon corrosion in the catalyst/carbon composite cathode degrades the cycling performance of the batteries. PMID:25563733

  3. One-dimensional manganese-cobalt oxide nanofibres as bi-functional cathode catalysts for rechargeable metal-air batteries.

    PubMed

    Jung, Kyu-Nam; Hwang, Soo Min; Park, Min-Sik; Kim, Ki Jae; Kim, Jae-Geun; Dou, Shi Xue; Kim, Jung Ho; Lee, Jong-Won

    2015-01-01

    Rechargeable metal-air batteries are considered a promising energy storage solution owing to their high theoretical energy density. The major obstacles to realising this technology include the slow kinetics of oxygen reduction and evolution on the cathode (air electrode) upon battery discharging and charging, respectively. Here, we report non-precious metal oxide catalysts based on spinel-type manganese-cobalt oxide nanofibres fabricated by an electrospinning technique. The spinel oxide nanofibres exhibit high catalytic activity towards both oxygen reduction and evolution in an alkaline electrolyte. When incorporated as cathode catalysts in Zn-air batteries, the fibrous spinel oxides considerably reduce the discharge-charge voltage gaps (improve the round-trip efficiency) in comparison to the catalyst-free cathode. Moreover, the nanofibre catalysts remain stable over the course of repeated discharge-charge cycling; however, carbon corrosion in the catalyst/carbon composite cathode degrades the cycling performance of the batteries. PMID:25563733

  4. One-dimensional manganese-cobalt oxide nanofibres as bi-functional cathode catalysts for rechargeable metal-air batteries

    NASA Astrophysics Data System (ADS)

    Jung, Kyu-Nam; Hwang, Soo Min; Park, Min-Sik; Kim, Ki Jae; Kim, Jae-Geun; Dou, Shi Xue; Kim, Jung Ho; Lee, Jong-Won

    2015-01-01

    Rechargeable metal-air batteries are considered a promising energy storage solution owing to their high theoretical energy density. The major obstacles to realising this technology include the slow kinetics of oxygen reduction and evolution on the cathode (air electrode) upon battery discharging and charging, respectively. Here, we report non-precious metal oxide catalysts based on spinel-type manganese-cobalt oxide nanofibres fabricated by an electrospinning technique. The spinel oxide nanofibres exhibit high catalytic activity towards both oxygen reduction and evolution in an alkaline electrolyte. When incorporated as cathode catalysts in Zn-air batteries, the fibrous spinel oxides considerably reduce the discharge-charge voltage gaps (improve the round-trip efficiency) in comparison to the catalyst-free cathode. Moreover, the nanofibre catalysts remain stable over the course of repeated discharge-charge cycling; however, carbon corrosion in the catalyst/carbon composite cathode degrades the cycling performance of the batteries.

  5. Corrosion-resistant catalyst supports for phosphoric acid fuel cells

    SciTech Connect

    Kosek, J.A.; Cropley, C.C.; LaConti, A.B.

    1990-01-01

    High-surface-area carbon blacks such as Vulcan XC-72 (Cabot Corp.) and graphitized carbon blacks such as 2700{degree}C heat-treated Black Pearls 2000 (HTBP) (Cabot Corp.) have found widespread applications as catalyst supports in phosphoric acid fuel cells (PAFCs). However, due to the operating temperatures and pressures being utilized in PAFCs currently under development, the carbon-based cathode catalyst supports suffer from corrosion, which decreases the performance and life span of a PAFC stack. The feasibility of using alternative, low-cost, corrosion-resistant catalyst support (CRCS) materials as replacements for the cathode carbon support materials was investigated. The objectives of the program were to prepare high-surface-area alternative supports and to evaluate the physical characteristics and the electrochemical stability of these materials. The O{sub 2} reduction activity of the platinized CRCS materials was also evaluated. 2 refs., 3 figs.

  6. Low temperature aluminum reduction cell using hollow cathode

    DOEpatents

    Brown, Craig W.; Frizzle, Patrick B.

    2002-08-20

    A method of producing aluminum in an electrolytic cell containing alumina dissolved in an electrolyte. A plurality of non-consumable anodes are disposed substantially vertically in the electrolyte along with a plurality of monolithic hollow cathodes. Each cathode has a top and bottom and the cathodes are disposed vertically in the electrolyte and the anodes and the cathodes are arranged in alternating relationship. Each of the cathodes is comprised of a first side facing a first opposing anode and a second side facing a second opposing anode. The first and second sides are joined by ends to form a reservoir in the hollow cathode for collecting aluminum therein deposited at the cathode.

  7. 15N solid-state nuclear magnetic resonance study of pyrolyzed metal-polyaniline cathode catalysts for oxygen reduction in fuel cells

    NASA Astrophysics Data System (ADS)

    Kuroki, Shigeki; Hosaka, Yo; Yamauchi, Chiharu; Nagata, Shinsuke; Sonoda, Mayu

    2015-09-01

    The oxygen reduction reaction (ORR) activity of pyrolyzed metal-free and metal (Mn, Fe, Co, Ni and Cu)-containing polyaniline (PANI) in polymer electrolyte fuel cell (PEFC) was studied. The metal-free PANI800 shows quite poor ORR catalytic activity, whilst the metal-containing PANIMe800 display a better ORR activity. The 15N CP/MAS NMR spectra of PANINi800 and PANICu800 show one weak peak at 118 ppm and there is no peak observed in PANIFe800, against that of PANI800, PANIMn800, PANICo800 and PANINi800 show two peaks at 273 and 118 ppm assigned to the pyridinic and pyridinium nitrogens. It is because of the paramagnetic effect of metal ions. The 15N spin-echo NMR spectra of PANIMe800 with fast recycle delay show the peaks at 140 and 270 ppm assigned to the graphitic and pyridinic nitrogens, against that of PANI800 shows no peak. The spectra of PANIMn800, PANICo800, PANINi800 and PANICu600 also contain a very broaden peak at 430 ppm assigned to the nitrogen with Fermi-contact effect from metal ions. The spectra of PANIFe800 show some spinning side bands and the average Fe3+-15N distance can be calculated. The some amount of iron ion are relieved and average Fe3+-15N distance increase after acid washing and the ORR activity decreases.

  8. Fuel cell applications for novel metalloporphyrin catalysts

    SciTech Connect

    Ryba, G.; Shelnutt, J.; Doddapaneni, N.; Zavadil, K.

    1997-04-01

    This project utilized Computer-Aided Molecular Design (CAMD) to develop a new class of metalloporphyrin materials for use as catalysts for two fuel cell reactions. The first reaction is the reduction of oxygen at the fuel cell cathode, and this reaction was the main focus of the research. The second reaction we attempted to catalyze was the oxidation of methanol at the anode. Two classes of novel metalloporphyrins were developed. The first class comprised the dodecaphenylporphyrins whose steric bulk forces them into a non-planar geometry having a pocket where oxygen or methanol is more tightly bound to the porphyrin than it is in the case of planar porphyrins. Significant improvements in the catalytic reduction of oxygen by the dodecaphenyl porphyrins were measured in electrochemical cells. The dodecaphenylporphyrins were further modified by fluorinating the peripheral phenyl groups to varying degrees. The fluorination strongly affected their redox potential, but no effect on their catalytic activity towards oxygen was observed. The second class of porphyrin catalysts was a series of hydrogen-bonding porphyrins whose interaction with oxygen is enhanced. Enhancements in the interaction of oxygen with the porphyrins having hydrogen bonding groups were observed spectroscopically. Computer modeling was performed using Molecular Simulations new CERIUS2 Version 1.6 and a research version of POLYGRAF from Bill Goddard`s research group at the California Institute of Technology. We reoptimized the force field because of an error that was in POLYGRAF and corrected a problem in treatment of the metal in early versions of the program. This improved force field was reported in a J. Am. Chem. Soc. manuscript. Experimental measurements made on the newly developed catalysts included the electrochemical testing in a fuel cell configuration and spectroscopic measurements (UV-Vis, Raman and XPS) to characterize the catalysts.

  9. Performance and stability of different cathode base materials for use in microbial fuel cells

    NASA Astrophysics Data System (ADS)

    Janicek, Anthony; Fan, Yanzhen; Liu, Hong

    2015-04-01

    Metal supporting materials are increasingly being used as base materials for microbial fuel cell (MFC) cathodes. However, the potential for corrosion may limit their use as base materials of MFCs during scale-up and long-term operation. In this study, the electrochemical performance, power generation in MFCs, hydrostatic pressure tolerance, and stability of activated carbon (catalyst) cathodes with carbon cloth or different size metal mesh as base materials are investigated. Electrochemical testing results show that the finest stainless steel mesh (250 × 250 openings per inch) outperforms carbon cloth cathodes by 10-40% at current densities ranging from 6 to 11.2 A m-2 over the typical cathode operating range of 0.1 V-0 V. When tested in MFCs, however, carbon cloth based cathodes out perform all stainless steel mesh cathodes by as much as 34%, reaching 1.72 W m-2; probably due to the corrosion and salt build-up on the surface of the stainless steel mesh cathodes. Carbon cloth cathodes also maintained high static pressure heads of 1.9 m. The high electrochemical performance, hydrostatic pressure tolerance, and corrosion resistance of carbon cloth suggest that carbon fiber based materials may be more suitable than metal based materials for use as MFC cathodes base material for some applications.

  10. A SnO2-Based Cathode Catalyst for Lithium-Air Batteries.

    PubMed

    Mei, Delong; Yuan, Xianxia; Ma, Zhong; Wei, Ping; Yu, Xuebin; Yang, Jun; Ma, Zi-Feng

    2016-05-25

    SnO2 and SnO2@C have been successfully synthesized with a simple hydrothermal procedure combined with heat treatment, and their performance as cathode catalysts of Li-air batteries has been comparatively evaluated and discussed. The results show that both SnO2 and SnO2@C are capable of catalyzing oxygen reduction reactions (ORR) and oxygen evolution reactions (OER) at the cathode of Li-air batteries, but the battery with SnO2@C displays better performance due to its unique higher conductivity, larger surface area, complex pore distribution, and huge internal space. PMID:27152996

  11. Proton exchange membrane fuel cell cathode contamination - Acetylene

    NASA Astrophysics Data System (ADS)

    Zhai, Y.; St-Pierre, Jean

    2015-04-01

    Acetylene adsorption on PEMFC electrodes and contamination in single cells are investigated with 300 ppm acetylene at a cathode held at 80 °C. The results of adsorption experiments suggest that acetylene adsorbs readily on electrodes and is reduced to ethylene and ethane under an open circuit potential of H2/N2, as the adsorbates can be electro-oxidized at high potentials. The cell voltage response shows that 300 ppm acetylene results in a cell performance loss of approximately 88%. The voltage degradation curve is divided into two stages by an inflection point, which suggests that potential-dependent processes are involved in acetylene poisoning. These potential-dependent processes may include acetylene oxidation and reduction as well as accumulation of intermediates on the electrode surface. Electrochemical impedance spectroscopy analysis suggests that acetylene affects the oxygen reduction reaction and may also affect mass transport processes. Acetylene also may be reduced in the steady poisoning state of the operating cell. After neat air operation, the cyclic voltammetry results imply that the cathode catalyst surface is almost completely restored, with no contaminant residues remaining in the MEA. Linear scanning voltammetry measurements show no change in hydrogen crossover caused by contamination, and polarization curves confirm complete recovery of cell performance.

  12. Power generation by packed-bed air-cathode microbial fuel cells.

    PubMed

    Zhang, Xiaoyuan; Shi, Juan; Liang, Peng; Wei, Jincheng; Huang, Xia; Zhang, Chuanyi; Logan, Bruce E

    2013-08-01

    Catalysts and catalyst binders are significant portions of the cost of microbial fuel cell (MFC) cathodes. Many materials have been tested as aqueous cathodes, but air-cathodes are needed to avoid energy demands for water aeration. Packed-bed air-cathodes were constructed without expensive binders or diffusion layers using four inexpensive carbon-based materials. Cathodes made from activated carbon produced the largest maximum power density of 676 ± 93 mW/m(2), followed by semi-coke (376 ± 47 mW/m(2)), graphite (122 ± 14 mW/m(2)) and carbon felt (60 ± 43 mW/m(2)). Increasing the mass of activated carbon and semi-coke from 5 to ≥ 15 g significantly reduced power generation because of a reduction in oxygen transfer due to a thicker water layer in the cathode (∼3 or ∼6 cm). These results indicate that a thin packed layer of activated carbon or semi-coke can be used to make inexpensive air-cathodes for MFCs. PMID:23732924

  13. Layered charge transfer complex cathodes or solid electrolyte cells

    SciTech Connect

    Louzos, D.V.

    1981-05-12

    Layered charge transfer complex cathodes for use in solid electrolyte cells are described wherein one layer of the cathode contains an electronic conductor which is isolated from the cell's solid electrolyte by a second layer of the cathode that does not contain an electronic conductor.

  14. Bifunctional silver nanoparticle cathode in microbial fuel cells for microbial growth inhibition with comparable oxygen reduction reaction activity.

    PubMed

    An, Junyeong; Jeon, Hongrae; Lee, Jaeyoung; Chang, In Seop

    2011-06-15

    Organic contamination of water bodies in which benthic microbial fuel cells (benthic MFCs) are installed, and organic crossover from the anode to the cathode of membraneless MFCs, is a factor causing oxygen depletion and substrate loss in the cathode due to the growth of heterotrophic aerobic bacteria. This study examines the possible use of silver nanoparticles (AgNPs) as a cathodic catalyst for MFCs suffering from organic contamination and oxygen depletion. Four treated cathodes (AgNPs-coated, Pt/C-coated, Pt/C+AgNPs-coated, and plain graphite cathodes) were prepared and tested under high levels of organics loading. During operation (fed with 50 mM acetate), the AgNPs-coated system showed the highest DO concentration (0.8 mg/L) in the cathode area as well as the highest current (ranging from 0.04 to 0.12 mA). Based on these results, we concluded that (1) the growth of oxygen-consuming heterotrophic microbes could be inhibited by AgNPs, (2) the function of AgNPs as a bacterial growth inhibitor resulted in a greater increase of DO concentration in the cathode than the other tested cathode systems, (3) AgNPs could be applied as a cathode catalyst for oxygen reduction, and as a result (4) the MFC with the AgNPs-coated cathode led to the highest current generation among the tested MFCs. PMID:21585217

  15. Effects of sulfide on microbial fuel cells with platinum and nitrogen-doped carbon powder cathodes.

    PubMed

    Feng, Yujie; Shi, Xinxin; Wang, Xin; Lee, He; Liu, Jia; Qu, Youpeng; He, Weihua; Kumar, S M Senthil; Kim, Byung Hong; Ren, Nanqi

    2012-05-15

    Because of the advantages of low cost, good electrical conductivity and high oxidation resistance, nitrogen-doped carbon (NDC) materials have a potential to replace noble metals in microbial fuel cells (MFCs) for wastewater treatment. In spite of a large volume of studies on NDC materials as catalysts for oxygen reduction reaction, the influence of sulfide on NDC materials has not yet been explicitly reported so far. In this communication, nitrogen-doped carbon powders (NDCP) were prepared by treating carbon powders in nitric acid under reflux condition. Sodium sulfide (Na(2)S) was added to the cathodic electrolyte to compare its effects on platinum (Pt) and NDCP cathodes. Cell voltages, power density and cathodic potentials were monitored without and with Na(2)S and after Na(2)S was removed. The maximum cell voltage of the MFCs with Pt cathode decreased by 10% in the presence of Na(2)S that did not change the performance of the MFC with NDCP cathode, and the maximum power density of the MFC with NDCP cathode was even 11.3% higher than that with Pt cathode (222.5 ± 8 mW m(-2) vs. 199.7 ± 4 mW m(-2)). PMID:22424752

  16. Design of graphene sheets-supported Pt catalyst layer in PEM fuel cells

    SciTech Connect

    Park, Seh K.; Shao, Yuyan; Wan, Haiying; Rieke, Peter C.; Viswanathan, Vilayanur V.; Towne, Silas A.; Saraf, Laxmikant V.; Liu, Jun; Lin, Yuehe; Wang, Yong

    2011-03-01

    A series of cathodes using Pt supported onto graphene sheets with different contents of carbon black in the catalyst layer were prepared and characterized. Carbon black was added as a spacer between two-dimensional graphene sheets in the catalyst layer to study its effect on the performances of proton exchange membrane fuel cell. Electrochemical properties and surface morphology of the cathodes with and without carbon black were characterized using cyclic voltammetry, ac-impedance spectroscopy, electrochemical polarization technique, and scanning electron microscopy. The results indicated that carbon black effectively modifies the array of graphene supports, resulting in more Pt nanoparticles available for electrochemical reaction and better mass transport in the catalyst layer.

  17. Structural and Electronic Transformations of Pt/C, Pd@Pt(1 ML)/C and Pd@Pt(2 ML)/C Cathode Catalysts in Polymer Electrolyte Fuel Cells during Potential-step Operating Processes Characterized by In-situ Time-resolved XAFS

    NASA Astrophysics Data System (ADS)

    Nagamatsu, Shin-ichi; Takao, Shinobu; Samjeské, Gabor; Nagasawa, Kensaku; Sekizawa, Oki; Kaneko, Takuma; Higashi, Kotaro; Uruga, Tomoya; Gayen, Sirshendu; Velaga, Srihari; Saniyal, Milan K.; Iwasawa, Yasuhiro

    2016-06-01

    The dynamic structural and electronic transformations of Pt/C, Pd@Pt(1 ML)/C, Pd@Pt(2 ML)/C cathode catalysts in polymer electrolyte fuel cells (PEFCs) during the potential-step operating processes between 0.4 and 1.4 VRHE (potential vs RHE) were characterized by in-situ (operando) time-resolved Pt LIII-edge quick-XAFS at 100 ms time-resolution. Potential-dependent surface structures and oxidation states of Pt, Pd@Pt(1 ML) and Pd@Pt(2 ML) nanoparticles on carbon at 0.4 and 1.4 VRHE were also analyzed by in-situ Pt LIII-edge and Pd K-edge quick-XAFS. The Pt, Pd@Pt(1 ML) and Pd@Pt(2 ML) nanoparticle surfaces were restructured and disordered at 1.4 VRHE, which were induced by strong Pt-O bonds as well as alloying effects. The rate constants for the changes of Pt valence, CN(Pt-Pt), CN(Pt-Pd) and CN(Pt-O) (CN: coordination number) in the potential-step operating processes were also determined and discussed in relation to the origin of oxygen reduction reaction (ORR) activities of the Pt/C, Pd@Pt(1 ML)/C and Pd@Pt(2 ML)/C cathode catalysts.

  18. MnCo2O4 nanowires anchored on reduced graphene oxide sheets as effective bifunctional catalysts for Li-O2 battery cathodes.

    PubMed

    Kim, Jong Guk; Kim, Youngmin; Noh, Yuseong; Kim, Won Bae

    2015-05-22

    A hybrid composite system of MnCo2 O4 nanowires (MCO NWs) anchored on reduced graphene oxide (RGO) nanosheets was prepared as the bifunctional catalyst of a Li-O2 battery cathode. The catalysts can be obtained from the hybridization of one-dimensional MCO NWs and two-dimensional RGO nanosheets. As O2 -cathode catalysts for Li-O2 cells, the MCO@RGO composites showed a high initial discharge capacity (ca. 11092.1 mAh gcarbon (-1) ) with a high rate performance. The Li-O2 cells could run for more than 35 cycles with high reversibility under a limited specific capacity of 1000 mAh gcarbon (-1) with a low potential polarization of 1.36 V, as compared with those of pure Ketjenblack and MCO NWs. The high cycling stability, low potential polarization, and rate capability suggest that the MCO@RGO composites prepared here are promising catalyst candidates for highly reversible Li-O2 battery cathodes. PMID:25908219

  19. Segmented cell testing for cathode parameter investigation

    NASA Astrophysics Data System (ADS)

    Tanasini, Pietro; Schuler, J. Andreas; Wuillemin, Zacharie; Ameur, Myriam L. Ben; Comninellis, Christos; Van herle, Jan

    The increasing quality and durability of solid oxide fuel cells (SOFCs) state-of-the-art materials renders the long-term testing of fuel cells difficult since considerably long equipment times are needed to obtain valuable results. Moreover, reproducibility issues are common due to the high sensitivity of the performance and degradation on the testing conditions. An original segmented cell configuration has been adopted in order to carry out four tests in parallel, thus decreasing the total experimental time and ensuring the same operating conditions for the four segments. The investigation has been performed on both anode-supported cells and symmetrical Lanthanum-Strontium Manganite-Yttria-stabilized Zirconia (LSM-YSZ) electrolyte-supported cells. In separate tests, the influence of variables like cathode thickness, current density and cathode composition on performance and degradation have been explored on anode-supported cells. Furthermore, the effect of chromium poisoning has been studied on electrolyte-supported symmetric cells by contacting one segment with a chromium-iron interconnect material. Long-term polarization of the segments is controlled with a multi-channel galvanostatic device designed in-house. Electrochemical characterization has been performed through electrochemical impedance spectroscopy (EIS) at different H 2 partial pressures, temperatures and bias current, effectively demonstrating the direct impact of each studied variable on the cell performance and degradation behavior. Segmented cell testing has been proven to be an effective strategy to achieve better reproducibility for SOFC measurements since it avoids the inevitable fluctuations found in a series of successively run tests. Moreover, simultaneous testing increased n-fold the data output per experiment, implying a considerable economy of time.

  20. High Performance and Durable Low PGM Cathode Catalysts

    SciTech Connect

    Wang, Yong; Liu, Jun; Shao, Yuyan; Cheng, Yingwen; Borup, Rodney L.; Rockward, Tommy; Brosha, Eric Lanich

    2015-08-17

    There is a strong need to decrease the amount of Pt electrocatalyst used in fuel cells and increase its durability for transportation application. Conventional strategies include Pt nanocrystals and Pt alloy with well-controlled structures, durable carbon support, non-carbon support, etc. We have developed the so-called “metal-metal oxide-carbon” triple junction concept to stabilize Pt and protect carbon from corrosion. It also improved the activity of Pt. The good performance was not achieved in fuel cell test mainly because of the transport issue due to the use of 2D graphene. In this project, our main goal is to demonstrate the concept in fuel cell device test using 3D porous graphene as support so that the transport issue could be addressed.

  1. Power generation using carbon mesh cathodes with different diffusion layers in microbial fuel cells

    NASA Astrophysics Data System (ADS)

    Luo, Yong; Zhang, Fang; Wei, Bin; Liu, Guangli; Zhang, Renduo; Logan, Bruce E.

    An inexpensive carbon material, carbon mesh, was examined to replace the more expensive carbon cloth usually used to make cathodes in air-cathode microbial fuel cells (MFCs). Three different diffusion layers were tested using carbon mesh: poly(dimethylsiloxane) (PDMS), polytetrafluoroethylene (PTFE), and Goretex cloth. Carbon mesh with a mixture of PDMS and carbon black as a diffusion layer produced a maximum power density of 1355 ± 62 mW m -2 (normalized to the projected cathode area), which was similar to that obtained with a carbon cloth cathode (1390 ± 72 mW m -2). Carbon mesh with a PTFE diffusion layer produced only a slightly lower (6.6%) maximum power density (1303 ± 48 mW m -2). The Coulombic efficiencies were a function of current density, with the highest value for the carbon mesh and PDMS (79%) larger than that for carbon cloth (63%). The cost of the carbon mesh cathode with PDMS/Carbon or PTFE (excluding catalyst and binder costs) is only 2.5% of the cost of the carbon cloth cathode. These results show that low cost carbon materials such as carbon mesh can be used as the cathode in an MFC without reducing the performance compared to more expensive carbon cloth.

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

    NASA Astrophysics Data System (ADS)

    Subramanian, Nalini Palaniappan

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

  3. Multiple cathodic reaction mechanisms in seawater cathodic biofilms operating in sediment microbial fuel cells.

    PubMed

    Babauta, Jerome T; Hsu, Lewis; Atci, Erhan; Kagan, Jeff; Chadwick, Bart; Beyenal, Haluk

    2014-10-01

    In this study, multiple reaction mechanisms in cathodes of sediment microbial fuel cells (SMFCs) were characterized by using cyclic voltammetry and microelectrode measurements of dissolved oxygen and pH. The cathodes were acclimated in SMFCs with sediment and seawater from San Diego Bay. Two limiting current regions were observed with onset potentials of approximately +400 mVAg/AgCl for limiting current I and -120 mVAg/AgCl for limiting current II. The appearance of two catalytic waves suggests that multiple cathodic reaction mechanisms influence cathodic performance. Microscale oxygen concentration measurements showed a zero surface concentration at the electrode surface for limiting current II but not for limiting current I, which allowed us to distinguish limiting current II as the conventional oxygen reduction reaction and limiting current I as a currently unidentified cathodic reaction mechanism. Microscale pH measurements further confirmed these results. PMID:25154833

  4. Porous Perovskite LaNiO3 Nanocubes as Cathode Catalysts for Li-O2 Batteries with Low Charge Potential

    NASA Astrophysics Data System (ADS)

    Zhang, Jian; Zhao, Yubao; Zhao, Xiao; Liu, Zhaolin; Chen, Wei

    2014-08-01

    Developing efficient catalyst for oxygen evolution reaction (OER) is essential for rechargeable Li-O2 battery. In our present work, porous LaNiO3 nanocubes were employed as electrocatalyst in Li-O2 battery cell. The as-prepared battery showed excellent charging performance with significantly reduced overpotential (3.40 V). The synergistic effect of porous structure, large specific surface area and high electrocatalytic activity of porous LaNiO3 nanocubes ensured the Li-O2 battery with enchanced capacity and good cycle stability. Furthermore, it was found that the lithium anode corrosion and cathode passivation were responsible for the capacity fading of Li-O2 battery. Our results indicated that porous LaNiO3 nanocubes represent a promising cathode catalyst for Li-O2 battery.

  5. Porous Perovskite LaNiO3 Nanocubes as Cathode Catalysts for Li-O2 Batteries with Low Charge Potential

    PubMed Central

    Zhang, Jian; Zhao, Yubao; Zhao, Xiao; Liu, Zhaolin; Chen, Wei

    2014-01-01

    Developing efficient catalyst for oxygen evolution reaction (OER) is essential for rechargeable Li-O2 battery. In our present work, porous LaNiO3 nanocubes were employed as electrocatalyst in Li-O2 battery cell. The as-prepared battery showed excellent charging performance with significantly reduced overpotential (3.40 V). The synergistic effect of porous structure, large specific surface area and high electrocatalytic activity of porous LaNiO3 nanocubes ensured the Li-O2 battery with enchanced capacity and good cycle stability. Furthermore, it was found that the lithium anode corrosion and cathode passivation were responsible for the capacity fading of Li-O2 battery. Our results indicated that porous LaNiO3 nanocubes represent a promising cathode catalyst for Li-O2 battery. PMID:25103186

  6. Properties of cathode materials in alkaline cells

    NASA Astrophysics Data System (ADS)

    Salkind, A. J.; McBreen, J.; Freeman, R.; Parkhurst, W. A.

    1984-04-01

    Conventional and new cathode materials in primary and secondary alkaline cells were investigated for stability, structure, electrochemical reversibility and efficiency. Included were various forms of AgO for reserve type silver zinc batteries, a new material - AgNiO2 and several nickel electrodes for nickel cadmium and nickel hydrogen cells for aerospace applications. A comparative study was made of the stability of electroformed and chemically prepared AgO. Stability was correlated with impurities. After the first discharge AgNiO2 can be recharged to the monovalent level. The discharge product is predominantly silver. Plastic bonded nickel electrodes display a second plateau on discharge. Additions of Co(OH)2 largely eliminate this.

  7. Polymer coatings as separator layers for microbial fuel cell cathodes

    NASA Astrophysics Data System (ADS)

    Watson, Valerie J.; Saito, Tomonori; Hickner, Michael A.; Logan, Bruce E.

    2011-03-01

    Membrane separators reduce oxygen flux from the cathode into the anolyte in microbial fuel cells (MFCs), but water accumulation and pH gradients between the separator and cathode reduces performance. Air cathodes were spray-coated (water-facing side) with anion exchange, cation exchange, and neutral polymer coatings of different thicknesses to incorporate the separator into the cathode. The anion exchange polymer coating resulted in greater power density (1167 ± 135 mW m-2) than a cation exchange coating (439 ± 2 mW m-2). This power output was similar to that produced by a Nafion-coated cathode (1114 ± 174 mW m-2), and slightly lower than the uncoated cathode (1384 ± 82 mW m-2). Thicker coatings reduced oxygen diffusion into the electrolyte and increased coulombic efficiency (CE = 56-64%) relative to an uncoated cathode (29 ± 8%), but decreased power production (255-574 mW m-2). Electrochemical characterization of the cathodes ex situ to the MFC showed that the cathodes with the lowest charge transfer resistance and the highest oxygen reduction activity produced the most power in MFC tests. The results on hydrophilic cathode separator layers revealed a trade off between power and CE. Cathodes coated with a thin coating of anion exchange polymer show promise for controlling oxygen transfer while minimally affecting power production.

  8. Improved Fabrication Of Cathodes For Solid-State Li Cells

    NASA Technical Reports Server (NTRS)

    Nagasubramanian, Ganesan

    1995-01-01

    Utilization of cathode material increased. Improved composite-cathode/polymer-electrolyte units for solid-state lithium secondary electrochemical cells fabricated in modified version of original method of fabrication. Further development of units may lead to increases in energy and power densities and in cycle lives of rechargeable lithium cells.

  9. Advanced Catalysts for Fuel Cells

    NASA Technical Reports Server (NTRS)

    Narayanan, Sekharipuram R.; Whitacre, Jay; Valdez, T. I.

    2006-01-01

    This viewgraph presentation reviews the development of catalyst for Fuel Cells. The objectives of the project are to reduce the cost of stack components and reduce the amount of precious metal used in fuel cell construction. A rapid combinatorial screening technique based on multi-electrode thin film array has been developed and validated for identifying catalysts for oxygen reduction; focus shifted from methanol oxidation in FY05 to oxygen reduction in FY06. Multi-electrode arrays of thin film catalysts of Pt-Ni and Pt-Ni-Zr have been deposited. Pt-Ni and have been characterized electrochemically and structurally. Pt-Ni-Zr and Pt-Ni films show higher current density and onset potential compared to Pt. Electrocatalytic activity and onset potential are found to be strong function of the lattice constant. Thin film Pt(59)Ni(39)Zr(2) can provide 10 times the current density of thin film Pt. Thin film Pt(59)Ni(39)Zr(2) also shows 65mV higher onset potential than Pt.

  10. Molten carbonate fuel cell cathode with mixed oxide coating

    DOEpatents

    Hilmi, Abdelkader; Yuh, Chao-Yi

    2013-05-07

    A molten carbonate fuel cell cathode having a cathode body and a coating of a mixed oxygen ion conductor materials. The mixed oxygen ion conductor materials are formed from ceria or doped ceria, such as gadolinium doped ceria or yttrium doped ceria. The coating is deposited on the cathode body using a sol-gel process, which utilizes as precursors organometallic compounds, organic and inorganic salts, hydroxides or alkoxides and which uses as the solvent water, organic solvent or a mixture of same.

  11. EFFECT OF PRETREATMENT ON PT-CO/C CATHODE CATALYSTS FOR THE OXYGEN-REDUCTION REACTION

    SciTech Connect

    Fox, E.; Colon-Mercado, H.

    2010-01-19

    Carbon supported Pt and Pt-Co electrocatalysts for the oxygen reduction reaction in low temperature fuel cells were prepared by the reduction of the metal salts with sodium borohydride and sodium formate. The effect of surface treatment with nitric acid on the carbon surface and Co on the surface of carbon prior to the deposition of Pt was studied. The catalysts where Pt was deposited on treated carbon the ORR reaction preceded more through the two electron pathway and favored peroxide production, while the fresh carbon catalysts proceeded more through the four electron pathway to complete the oxygen reduction reaction. NaCOOH reduced Pt/C catalysts showed higher activity that NaBH{sub 4} reduced Pt/C catalysts. It was determined that the Co addition has a higher impact on catalyst activity and active surface area when used with NaBH{sub 4} as reducing agent as compared to NaCOOH.

  12. Fuel cells and fuel cell catalysts

    DOEpatents

    Masel, Richard I.; Rice, Cynthia A.; Waszczuk, Piotr; Wieckowski, Andrzej

    2006-11-07

    A direct organic fuel cell includes a formic acid fuel solution having between about 10% and about 95% formic acid. The formic acid is oxidized at an anode. The anode may include a Pt/Pd catalyst that promotes the direct oxidation of the formic acid via a direct reaction path that does not include formation of a CO intermediate.

  13. Electro-catalysts for the cathode(s) to enhance its activity to reduce socl2 in li/socl2 battery

    SciTech Connect

    Venkatasetty, H. V.

    1981-02-24

    In a lithium-thionyl chloride cell having a lithium anode, an electrolyte including thionyl chloride and a cathode with current collector, the improvement comprising a coating of a metal phthalocyanine complex on a said cathode. Particularly preferred are transition metal phthalocyanine complexes, such as copper and cobalt phthalocyanine.

  14. Mesh optimization for microbial fuel cell cathodes constructed around stainless steel mesh current collectors

    NASA Astrophysics Data System (ADS)

    Zhang, Fang; Merrill, Matthew D.; Tokash, Justin C.; Saito, Tomonori; Cheng, Shaoan; Hickner, Michael A.; Logan, Bruce E.

    Mesh current collectors made of stainless steel (SS) can be integrated into microbial fuel cell (MFC) cathodes constructed of a reactive carbon black and Pt catalyst mixture and a poly(dimethylsiloxane) (PDMS) diffusion layer. It is shown here that the mesh properties of these cathodes can significantly affect performance. Cathodes made from the coarsest mesh (30-mesh) achieved the highest maximum power of 1616 ± 25 mW m -2 (normalized to cathode projected surface area; 47.1 ± 0.7 W m -3 based on liquid volume), while the finest mesh (120-mesh) had the lowest power density (599 ± 57 mW m -2). Electrochemical impedance spectroscopy showed that charge transfer and diffusion resistances decreased with increasing mesh opening size. In MFC tests, the cathode performance was primarily limited by reaction kinetics, and not mass transfer. Oxygen permeability increased with mesh opening size, accounting for the decreased diffusion resistance. At higher current densities, diffusion became a limiting factor, especially for fine mesh with low oxygen transfer coefficients. These results demonstrate the critical nature of the mesh size used for constructing MFC cathodes.

  15. Parameters characterization and optimization of activated carbon (AC) cathodes for microbial fuel cell application.

    PubMed

    Santoro, Carlo; Artyushkova, Kateryna; Babanova, Sofia; Atanassov, Plamen; Ieropoulos, Ioannis; Grattieri, Matteo; Cristiani, Pierangela; Trasatti, Stefano; Li, Baikun; Schuler, Andrew J

    2014-07-01

    Activated carbon (AC) is employed as a cost-effective catalyst for cathodic oxygen reduction in microbial fuel cells (MFC). The fabrication protocols of AC-based cathodes are conducted at different applied pressures (175-3500 psi) and treatment temperatures (25-343°C). The effects of those parameters along with changes in the surface morphology and chemistry on the cathode performances are comprehensively examined. The cathodes are tested in a three-electrode setup and explored in single chamber membraneless MFCs (SCMFCs). The results show that the best performance of the AC-based cathode is achieved when a pressure of 1400 psi is applied followed by heat treatment of 150-200°C for 1h. The influence of the applied pressure and the temperature of the heat treatment on the electrodes and SCMFCs is demonstrated as the result of the variation in the transfer resistance, the surface morphology and surface chemistry of the AC-based cathodes tested. PMID:24787317

  16. Phthalocyanine cathode materials for secondary lithium cells

    SciTech Connect

    Tamaki, J.; Yamaji, A.

    1982-01-01

    Discharge and charge characteristics of various phthalocyanine cathodes coupled with lithium metal are studied. The best capacity based only on cathode active material weight is 1440 A-hr/kg in the lithium/iron phthalocyanine system, and the cycle life of the lithium/Cu phthalocyanine system is more than 100 times at the discharge depth of 157 A-hr/kg. The cathode reaction mechanism is supposed to be lithium intercalation between phthalocyanine molecules. The results indicate that these phthalocyanines are promising cathode active materials for lithium secondary batteries.

  17. Performance of Stainless Steel Mesh Cathode and PVDF-graphite Cathode in Microbial Fuel Cells

    NASA Astrophysics Data System (ADS)

    Huang, Liping; Tian, Ying; Li, Mingliang; He, Gaohong; Li, Zhikao

    2010-11-01

    Inexpensive and conductive materials termed as stainless steel mesh and polyvinylidene fluoride (PVDF)-graphite were currently used as the air cathode electrodes in MFCs for the investigation of power production. By loading PTFE (poly(tetrafluoroethylene)) on the surface of stainless steel mesh, electricity production reached 3 times as high as that of the naked stainless steel. A much high catalytic activity for oxygen reduction was exhibited by Pt based and PTFE loading stainless steel mesh cathode, with an electricity generation of 1144±44 mW/m2 (31±1 W/m3) and a Coulombic efficiency (CE) of 77±2%. When Pt was replaced by an inexpensive transition metal based catalyst (cobalt tetramethylphenylporphyrin, CoTMPP), power production and CE were 845±21 mW/m2 (23±1 W/m3) and 68±1%, respectively. Accordingly, power production from PVDF-graphite (hydrophobic) MFC and PVDF-graphite (hydrophile) MFC were 286±20 mW/m2(8±1 W/m3) and 158±13 mW/m2(4±0.4 W/m3), respectively using CoTMPP as catalyst. These results give us new insight into materials like stainless steel mesh and PVDF-graphite as low cost cathode for reducing the costs of MFCs for wastewater treatment applications.

  18. Effects of Humidity on Solid Oxide Fuel Cell Cathodes

    SciTech Connect

    Hardy, John S.; Stevenson, Jeffry W.; Singh, Prabhakar; Mahapatra, Manoj K.; Wachsman, E. D.; Liu, Meilin; Gerdes, Kirk R.

    2015-03-17

    This report summarizes results from experimental studies performed by a team of researchers assembled on behalf of the Solid-state Energy Conversion Alliance (SECA) Core Technology Program. Team participants employed a variety of techniques to evaluate and mitigate the effects of humidity in solid oxide fuel cell (SOFC) cathode air streams on cathode chemistry, microstructure, and electrochemical performance.

  19. Microbial Fuel Cell Performance with a Pressurized Cathode Chamber

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Microbial fuel cell (MFC) power densities are often constrained by the oxygen reduction reaction rate on the cathode electrode. One important factor for this is the normally low solubility of oxygen in the aqueous cathode solution creating mass transport limitations, which hinder oxygen reduction a...

  20. Nanofiber Scaffold for Cathode of Solid Oxide Fuel Cell

    SciTech Connect

    Zhi, Mingjia; Mariani, Nicholas; Gemmen, Randall; Gerdes, Kirk; Wu, Nianqiang

    2010-10-01

    A high performance solid oxide fuel cell cathode using the yttria-stabilized zirconia (YSZ) nanofibers scaffold with the infiltrated La1-xSrxMnO3 (LSM) shows an enhanced catalytic activity toward oxygen reduction. Such a cathode offers a continuous path for charge transport and an increased number of triple-phase boundary sites.

  1. Performance of practical-sized membrane-electrode assemblies using titanium nitride-supported platinum catalysts mixed with acetylene black as the cathode catalyst layer

    NASA Astrophysics Data System (ADS)

    Shintani, Haruhiko; Kakinuma, Katsuyoshi; Uchida, Hiroyuki; Watanabe, Masahiro; Uchida, Makoto

    2015-04-01

    The performance of practical-sized membrane-electrode assemblies (MEAs) using titanium nitride-supported platinum (Pt/TiN) as the cathode catalysts was evaluated with the use of a practical single cell designed for microscale combined heat and power (CHP) applications. The performance can be controlled by adding acetylene black (AB), with the behavior being dominated by the percolation law. The electrical resistance of the MEAs drastically decreased for AB contents greater than 37 vol%. The Pt utilization percentage was close to 100% for Pt/TiN with percolated AB networks. It was also found that the percolated AB networks supplied effective gas transport pathways, which were not flooded by generated water, thus enhancing the oxygen mass transport. The practical-sized MEA using Pt/TiN + 47 vol% AB showed 1.5 times greater mass activity and a comparable performance under a practical operating condition for micro-CHP applications, compared with the MEA using a commercial graphitized carbon black-supported platinum catalyst.

  2. Electrochemical machining analysis on grid cathode composed of square cells

    NASA Astrophysics Data System (ADS)

    Lu, Yonghua; Liu, Kai; Zhao, Dongbiao

    2013-07-01

    During the electrochemical machining (ECM), the cathodes designed by the existing methods are mainly unitary cathodes, which can be only used to produce the workpieces with the same shapes. However, there are few researches on designing cathodes for machining the different workpieces with the different surfaces. This paper presents the grid cathode composed of the square cells to produce the workpieces with different shapes. Three types of the square cells, 2.5 mm×2.5 mm, 3 mm×3 mm, and 4 mm×4 mm, are utilized to construct the plane, the slant, and the blade cathode. The material of the cathode and the anode is CrNi18Ti9, and the ingredient of electrolyte is 15% NaCl and 15% NaNO3. The machining equilibrium machining current and time are acquired and analyzed, the machining process and the workpiece quality are compared between using the grid cathode and the unitary cathode. Moreover, the machining errors on the workpiece surface are measured and analyzed, and the error reasons are traced and discussed to obtain the better surface quality of the workpiece. The experiment and analysis results show that the grid cathode can be used to manufacture the workpieces with complex shapes in certain range of the error. The workpiece quality improves with the size of the square cell being reduced, and if the square element is small enough, the workpiece quality is almost equal to the one machined by the unitary cathode. The proposed research realizes a single cathode machining the different workpieces with the different surfaces.

  3. High surface area graphite as alternative support for proton exchange membrane fuel cell catalysts

    NASA Astrophysics Data System (ADS)

    Ferreira-Aparicio, P.; Folgado, M. A.; Daza, L.

    The suitability of a high surface area graphite (HSAG) as proton exchange membrane fuel cell (PEMFC) catalyst support has been evaluated and compared with that of the most popular carbon black: the Vulcan XC72. It has been observed that Pt is arranged on the graphite surface resulting in different structures which depend on the catalysts synthesis conditions. The influence that the metal particle size and the metal-support interaction exert on the catalysts degradation rate is analyzed. Temperature programmed oxidation (TPO) under oxygen containing streams has been shown to be a useful method to assess the resistance of PEMFC catalysts to carbon corrosion. The synthesized Pt/HSAG catalysts have been evaluated in single cell tests in the cathode catalytic layer. The obtained results show that HSAG can be a promising alternative to the traditionally used Vulcan XC72 carbon black when suitable catalysts synthesis conditions are used.

  4. Electrorefining cell with parallel electrode/concentric cylinder cathode

    SciTech Connect

    Gay, E.C.; Miller, W.E.; Laidler, J.J.

    1995-12-31

    A cathode-anode arrangement for use in an electrolytic cell is adapted for electrochemically refining spent nuclear fuel from a nuclear reactor and recovering purified uranium and a mixture of uranium and plutonium for use as a fresh blanket and core fuel in a nuclear reactor. The arrangement includes a plurality of inner anodic dissolution baskets that are each attached to a respective support rod, are submerged in a molten lithium halide salt, and are rotationally displaced. An inner hollow cylindrical-shaped cathode is concentrically disposed about the inner anodic dissolution baskets. Concentrically disposed about the inner cathode in a spaced manner are a plurality of outer anodic dissolution baskets, while an outer hollow cylindrical-shaped cathode is disposed about the outer anodic dissolution baskets. Uranium is deposited from the anode baskets in a uniform cylindrical shape on the inner and outer cathode cylinders by rotating the anode baskets within the molten lithium halide salt. Scrapers located on each anode basket abrade and remove the spent fuel deposits on the surfaces of the inner and outer cathode cylinders, with the spent fuel falling to the bottom of the cell for removal. Cell resistance is reduced and uranium collection efficiency enhanced by increasing the electrode area and reducing the anode-cathode spacing for enhanced trapping and recovery of uranium dendrites scraped off of the cylindrical cathodes which may be greater in number than two.

  5. Corrosion testing of candidates for the alkaline fuel cell cathode

    NASA Technical Reports Server (NTRS)

    Singer, Joseph; Fielder, William L.

    1989-01-01

    Current/voltage data was obtained for specially made corrosion electrodes of some oxides and of gold materials for the purpose of developing a screening test of catalysts and supports for use at the cathode of the alkaline fuel cell. The data consists of measurements of current at fixed potentials and cyclic voltammograms. These data will have to be correlated with longtime performance data in order to fully evaluate this approach to corrosion screening. Corrosion test screening of candidates for the oxygen reduction electrode of the alkaline fuel cell was applied to two substances, the pyrochlore Pb2Ru2O6.5 and the spinel NiCo2O4. The substrate gold screen and a sample of the IFC Orbiter Pt-Au performance electrode were included as blanks. The pyrochlore data indicate relative stability, although nothing yet can be said about long term stability. The spinel was plainly unstable. For this type of testing to be validated, comparisons will have to be made with long term performance tests.

  6. Testing Metal Chlorides For Use In Sodium-Cell Cathodes

    NASA Technical Reports Server (NTRS)

    Bugga, Ratnakumar V.; Attia, Alan I.; Halpert, Gerald

    1992-01-01

    Cyclic voltammetric curves of transition-metal wires in molten NaAlCl4 electrolyte used to eliminate suitability of transition metals as cathodes in sodium cells. Cyclic voltammetry used in conjunction with measurement of galvanostatic polarization curves determines whether given metal chloride suitable as cathode material in such cell. Cells useful in such high-energy-density and high-power-density applications as leveling loads on electric-power plants, supplying power to electric ground vehicles, and aerospace applications.

  7. Micro-nano structured Ni-MOFs as high-performance cathode catalyst for rechargeable Li-O2 batteries

    NASA Astrophysics Data System (ADS)

    Hu, Xiaofei; Zhu, Zhiqiang; Cheng, Fangyi; Tao, Zhanliang; Chen, Jun

    2015-07-01

    Rechargeable Li-O2 batteries with high theoretical energy density urgently require efficient cathode catalysts to improve their electrochemical performance. Here we first demonstrated the application of Ni-based organic frameworks of Ni(4,4'-bipy)(H3BTC) (4,4'-bipy = 4,4'-bipyridine H3BTC = 1,3,5-benzenetricarboxylic acid) (Ni-MOFs) as high-performance cathode catalysts for rechargeable Li-O2 batteries. It is found that Ni-MOFs with a three-dimensional (3D) micro-nano structure, open catalytic sites and large specific surface area can guarantee the free transfer of O2 and effective contact between the electrolyte and the catalytic sites. Preliminary testing of Ni-MOFs showed that they possess an extremely high capacity of 9000 mA h g-1, a high round-trip efficiency of 80%, and a respectable cycling of 170 cycles without obvious voltage drop. Furthermore, plastic rechargeable Li-O2 batteries with Ni-MOFs as the cathode catalyst have been assembled, displaying an energy density of 478 Wh kg-1. This study leads to both fundamental and technological advances of Ni-MOFs as the cathode for rechargeable Li-O2 batteries.Rechargeable Li-O2 batteries with high theoretical energy density urgently require efficient cathode catalysts to improve their electrochemical performance. Here we first demonstrated the application of Ni-based organic frameworks of Ni(4,4'-bipy)(H3BTC) (4,4'-bipy = 4,4'-bipyridine H3BTC = 1,3,5-benzenetricarboxylic acid) (Ni-MOFs) as high-performance cathode catalysts for rechargeable Li-O2 batteries. It is found that Ni-MOFs with a three-dimensional (3D) micro-nano structure, open catalytic sites and large specific surface area can guarantee the free transfer of O2 and effective contact between the electrolyte and the catalytic sites. Preliminary testing of Ni-MOFs showed that they possess an extremely high capacity of 9000 mA h g-1, a high round-trip efficiency of 80%, and a respectable cycling of 170 cycles without obvious voltage drop. Furthermore

  8. Facile and Gram-scale Synthesis of Metal-free Catalysts: Toward Realistic Applications for Fuel Cells

    NASA Astrophysics Data System (ADS)

    Kim, Ok-Hee; Cho, Yong-Hun; Chung, Dong Young; Kim, Min Jeong; Yoo, Ji Mun; Park, Ji Eun; Choe, Heeman; Sung, Yung-Eun

    2015-03-01

    Although numerous reports on nonprecious metal catalysts for replacing expensive Pt-based catalysts have been published, few of these studies have demonstrated their practical application in fuel cells. In this work, we report graphitic carbon nitride and carbon nanofiber hybrid materials synthesized by a facile and gram-scale method via liquid-based reactions, without the use of toxic materials or a high pressure-high temperature reactor, for use as fuel cell cathodes. The resulting materials exhibited remarkable methanol tolerance, selectivity, and stability even without a metal dopant. Furthermore, these completely metal-free catalysts exhibited outstanding performance as cathode materials in an actual fuel cell device: a membrane electrode assembly with both acidic and alkaline polymer electrolytes. The fabrication method and remarkable performance of the single cell produced in this study represent progressive steps toward the realistic application of metal-free cathode electrocatalysts in fuel cells.

  9. Facile and Gram-scale Synthesis of Metal-free Catalysts: Toward Realistic Applications for Fuel Cells

    PubMed Central

    Kim, Ok-Hee; Cho, Yong-Hun; Chung, Dong Young; Kim, Min Jeong; Yoo, Ji Mun; Park, Ji Eun; Choe, Heeman; Sung, Yung-Eun

    2015-01-01

    Although numerous reports on nonprecious metal catalysts for replacing expensive Pt-based catalysts have been published, few of these studies have demonstrated their practical application in fuel cells. In this work, we report graphitic carbon nitride and carbon nanofiber hybrid materials synthesized by a facile and gram-scale method via liquid-based reactions, without the use of toxic materials or a high pressure-high temperature reactor, for use as fuel cell cathodes. The resulting materials exhibited remarkable methanol tolerance, selectivity, and stability even without a metal dopant. Furthermore, these completely metal-free catalysts exhibited outstanding performance as cathode materials in an actual fuel cell device: a membrane electrode assembly with both acidic and alkaline polymer electrolytes. The fabrication method and remarkable performance of the single cell produced in this study represent progressive steps toward the realistic application of metal-free cathode electrocatalysts in fuel cells. PMID:25728910

  10. Copper Chloride Cathode For Liquid-Sodium Cell

    NASA Technical Reports Server (NTRS)

    Bugga, Ratnakumar V.; Distefano, Salvador; Nagasubramanian, Ganesan; Bankston, Clyde P.

    1990-01-01

    Rechargeable liquid-sodium cell with copper chloride cathode offers substantial increase in energy density over cells made with other cathode materials. Unit has theoretical maximum energy density of 1135 W.h/kg. Generates electricity by electrochemical reaction of molten sodium and solid copper chloride immersed in molten electrolyte, sodium tetrachloroaluminate at temperature of equal to or greater than 200 degrees C. Wall of alumina tube separates molten electrolyte from molten sodium anode. Copper chloride cathode embedded in pores of sintered nickel cylinder or directly sintered.

  11. Conducting polymer-doped polyprrrole as an effective cathode catalyst for Li-O{sub 2} batteries

    SciTech Connect

    Zhang, Jinqiang; Sun, Bing; Ahn, Hyo-Jun; Wang, Chengyin; Wang, Guoxiu

    2013-12-15

    Graphical abstract: - Highlights: • Doped polypyrrole as cathode catalysts for Li-O{sub 2} batteries. • Polypyrrole has an excellent redox capability to activate oxygen reduction. • Chloride doped polypyrrole demonstrated an improved catalytic performance in Li-O{sub 2} batteries. - Abstract: Polypyrrole conducting polymers with different dopants have been synthesized and applied as the cathode catalyst in Li-O{sub 2} batteries. Polypyrrole polymers exhibited an effective catalytic activity towards oxygen reduction in lithium oxygen batteries. It was discovered that dopant significantly influenced the electrochemical performance of polypyrrole. The polypyrrole doped with Cl{sup −} demonstrated higher capacity and more stable cyclability than that doped with ClO{sub 4}{sup −}. Polypyrrole conducting polymers also exhibited higher capacity and better cycling performance than that of carbon black catalysts.

  12. Corrosion testing of candidates for the alkaline fuel cell cathode

    NASA Technical Reports Server (NTRS)

    Singer, Joseph; Fielder, William L.

    1989-01-01

    It is desirable to employ a corrosion screening test for catalyst or support candidates for the fuel cell cathode before entering upon optimization of the candidate or of the catalytic electrode. To this end, corrosion test electrodes, intended for complete immersion and maximum wetting, have been made with 30 to 40 vol. pct Teflon; with perovskites this is about 10 to 15 pct. The candidates were synthesized by methods intended for single-phase product without special emphasis on high surface area, although the substances tested were no coarser than 2 m squared/g. A typical loading was 25 mg/cm sq of the pure substance, usually on gold screen, a few mm squared of which were left bare for contacting. Contact to the gold lead wire was made by welding with a micro-torch or a spot-welder. Corrosion testing consisted of obtaining current-voltage data under flowing inert gas in the potential region for reduction of O2. The electrode was immersed in 30 pct KOH. Observations were made at 20 C and 80 C, and the results compared with data from gold standards. Results with some perovskites, pyrochlores, spinels, and interstitial compounds will be discussed.

  13. Metal-air batteries: from oxygen reduction electrochemistry to cathode catalysts.

    PubMed

    Cheng, Fangyi; Chen, Jun

    2012-03-21

    Because of the remarkably high theoretical energy output, metal-air batteries represent one class of promising power sources for applications in next-generation electronics, electrified transportation and energy storage of smart grids. The most prominent feature of a metal-air battery is the combination of a metal anode with high energy density and an air electrode with open structure to draw cathode active materials (i.e., oxygen) from air. In this critical review, we present the fundamentals and recent advances related to the fields of metal-air batteries, with a focus on the electrochemistry and materials chemistry of air electrodes. The battery electrochemistry and catalytic mechanism of oxygen reduction reactions are discussed on the basis of aqueous and organic electrolytes. Four groups of extensively studied catalysts for the cathode oxygen reduction/evolution are selectively surveyed from materials chemistry to electrode properties and battery application: Pt and Pt-based alloys (e.g., PtAu nanoparticles), carbonaceous materials (e.g., graphene nanosheets), transition-metal oxides (e.g., Mn-based spinels and perovskites), and inorganic-organic composites (e.g., metal macrocycle derivatives). The design and optimization of air-electrode structure are also outlined. Furthermore, remarks on the challenges and perspectives of research directions are proposed for further development of metal-air batteries (219 references). PMID:22254234

  14. Electrorefining cell with parallel electrode/concentric cylinder cathode

    DOEpatents

    Gay, E.C.; Miller, W.E.; Laidler, J.J.

    1997-07-22

    A cathode-anode arrangement for use in an electrolytic cell is adapted for electrochemically refining spent nuclear fuel from a nuclear reactor and recovering purified uranium for further treatment and possible recycling as a fresh blanket or core fuel in a nuclear reactor. The arrangement includes a plurality of inner anodic dissolution baskets that are each attached to a respective support rod, are submerged in a molten lithium halide salt, and are rotationally displaced. An inner hollow cylindrical-shaped cathode is concentrically disposed about the inner anodic dissolution baskets. Concentrically disposed about the inner cathode in a spaced manner are a plurality of outer anodic dissolution baskets, while an outer hollow cylindrical-shaped is disposed about the outer anodic dissolution baskets. Uranium is transported from the anode baskets and deposited in a uniform cylindrical shape on the inner and outer cathode cylinders by rotating the anode baskets within the molten lithium halide salt. Scrapers located on each anode basket abrade and remove the spent fuel deposits on the surfaces of the inner and outer cathode cylinders, with the spent fuel falling to the bottom of the cell for removal. Cell resistance is reduced and uranium deposition rate enhanced by increasing the electrode area and reducing the anode-cathode spacing. Collection efficiency is enhanced by trapping and recovery of uranium dendrites scrapped off of the cylindrical cathodes which may be greater in number than two. 12 figs.

  15. Electrorefining cell with parallel electrode/concentric cylinder cathode

    DOEpatents

    Gay, Eddie C.; Miller, William E.; Laidler, James J.

    1997-01-01

    A cathode-anode arrangement for use in an electrolytic cell is adapted for electrochemically refining spent nuclear fuel from a nuclear reactor and recovering purified uranium for further treatment and possible recycling as a fresh blanket or core fuel in a nuclear reactor. The arrangement includes a plurality of inner anodic dissolution baskets that are each attached to a respective support rod, are submerged in a molten lithium halide salt, and are rotationally displaced. An inner hollow cylindrical-shaped cathode is concentrically disposed about the inner anodic dissolution baskets. Concentrically disposed about the inner cathode in a spaced manner are a plurality of outer anodic dissolution baskets, while an outer hollow cylindrical-shaped is disposed about the outer anodic dissolution baskets. Uranium is transported from the anode baskets and deposited in a uniform cylindrical shape on the inner and outer cathode cylinders by rotating the anode baskets within the molten lithium halide salt. Scrapers located on each anode basket abrade and remove the spent fuel deposits on the surfaces of the inner and outer cathode cylinders, with the spent fuel falling to the bottom of the cell for removal. Cell resistance is reduced and uranium deposition rate enhanced by increasing the electrode area and reducing the anode-cathode spacing. Collection efficiency is enhanced by trapping and recovery of uranium dendrites scrapped off of the cylindrical cathodes which may be greater in number than two.

  16. 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. PMID:26908214

  17. Hybrid binuclear-cobalt-phthalocyanine as oxygen reduction reaction catalyst in single chamber microbial fuel cells

    NASA Astrophysics Data System (ADS)

    Li, Baitao; Zhou, Xiuxiu; Wang, Xiujun; Liu, Bingchuan; Li, Baikun

    2014-12-01

    A novel hybrid binuclear-cobalt-phthalocyanine (Bi-CoPc) is developed as the cathode catalyst to replace the costly platinum (Pt) in single chamber microbial fuel cells (SCMFCs). Bi-CoPc/C is integrated with metal oxides (NiO and CoO) to form macrocyclic complex for enhanced oxygen reduction rate (ORR). The characteristics of hybrid catalysts (Bi-CoPc/C-CoO and Bi-CoPc/C-NiO) are compared with Co-contained catalysts (CoPc/C and Bi-CoPc/C) and metal oxide catalysts (NiO and CoO). The increase in O and N functional groups indicates the benefits of NiO and CoO to the cathode catalysts. The cyclic voltammetry (CV) shows the reduction peak for Bi-CoPc/C-NiO and Bi-CoPc/C-CoO at -0.12 V and -0.22 V, respectively. The power densities (368 mW m-2 and 400 mW m-2) of SCMFCs with Bi-CoPc/C-CoO and Bi-CoPc-NiO/C are the highest among the cathodes tested, and close to that of Pt (450 mW m-2). This study demonstrates that hybrid Bi-CoPc/C with metal oxides has a great potential as a cost-effective catalyst in MFCs.

  18. Metal-catalyst-free carbohydrazide fuel cells with three-dimensional graphene anodes.

    PubMed

    Qi, Ji; Benipal, Neeva; Wang, Hui; Chadderdon, David J; Jiang, Yibo; Wei, Wei; Hu, Yun Hang; Li, Wenzhen

    2015-04-13

    As a potential solution to concerns on sustainable energy, the wide spread commercialization of fuel cell has long been hindered by limited reserves and relatively high costs of metal catalysts. 3D graphene, a carbon-only catalyst prepared by reduction of carbon monoxide with lithium oxide, is found to electrochemically catalyze carbohydrazide oxidation reaction efficiently. A prototype of a completely metal-catalyst-free anion exchange membrane fuel cell (AEMFC) with a 3D graphene anode catalyst and an N-doped CNT (N-CNT) cathode catalyst generate a peak power density of 24.9 mW cm(-2) . The average number of electrons electrochemically extracted from one carbohydrazide molecule is 4.9, indicating the existence of CN bond activation, which is a key factor contributing to high fuel utilization efficiency. PMID:25469500

  19. Performance and durability of anode-supported flat-tubular solid oxide fuel cells with Ag-infiltrated cathodes.

    PubMed

    Pi, Seuk-Hoon; Lee, Jong-Won; Lee, Seung-Bok; Lim, Tak-Hyoung; Park, Seok-Joo; Park, Chong-Ook; Song, Rak-Hyun

    2014-10-01

    An anode-supported flat-tubular solid oxide fuel cell is an advanced cell design, which offers many advantages including a high volumetric power density, a minimized sealing area and a high resistance to thermal cycling. Infiltration of nano-sized noble metal catalysts into a porous cathode is known to be an effective method to improve cathode performances at reduced temperatures, but the cathode stability is of potential concern. This study addresses the performance and durability of anode-supported flat-tubular solid oxide fuel cells with Ag-infiltrated cathodes. Uniformly dispersed Ag nanoparticles on the cathode are formed via a wet infiltration technique combined with subsequent heat-treatment. Although the Ag infiltration results in improved cell performance, the durability tests indicate that the cell performance degrades over time and that the degradation rate increases with increasing Ag loading in the cathode. The observed performance degradation is mainly attributed to formation of large-scale Ag agglomerates. A strategy based on an inter-dispersed composite of Ag and CeO2 nanoparticles is proposed to mitigate the performance degradation. PMID:25942845

  20. Functionally Graded Cathodes for Solid Oxide Fuel Cells

    SciTech Connect

    YongMan Choi; Meilin Liu

    2006-09-30

    This DOE SECA project focused on both experimental and theoretical understanding of oxygen reduction processes in a porous mixed-conducting cathode in a solid oxide fuel cell (SOFC). Elucidation of the detailed oxygen reduction mechanism, especially the rate-limiting step(s), is critical to the development of low-temperature SOFCs (400 C to 700 C) and to cost reduction since much less expensive materials may be used for cell components. However, cell performance at low temperatures is limited primarily by the interfacial polarization resistances, specifically by those associated with oxygen reduction at the cathode, including transport of oxygen gas through the porous cathode, the adsorption of oxygen onto the cathode surface, the reduction and dissociation of the oxygen molecule (O{sub 2}) into the oxygen ion (O{sup 2-}), and the incorporation of the oxygen ion into the electrolyte. In order to most effectively enhance the performance of the cathode at low temperatures, we must understand the mechanism and kinetics of the elementary processes at the interfaces. Under the support of this DOE SECA project, our accomplishments included: (1) Experimental determination of the rate-limiting step in the oxygen reduction mechanism at the cathode using in situ FTIR and Raman spectroscopy, including surface- and tip-enhanced Raman spectroscopy (SERS and TERS). (2) Fabrication and testing of micro-patterned cathodes to compare the relative activity of the TPB to the rest of the cathode surface. (3) Construction of a mathematical model to predict cathode performance based on different geometries and microstructures and analyze the kinetics of oxygen-reduction reactions occurring at charged mixed ionic-electronic conductors (MIECs) using two-dimensional finite volume models with ab initio calculations. (4) Fabrication of cathodes that are graded in composition and microstructure to generate large amounts of active surface area near the cathode/electrolyte interface using a

  1. Membrane catalyst layer for fuel cells

    DOEpatents

    Wilson, Mahlon S.

    1993-01-01

    A gas reaction fuel cell incorporates a thin catalyst layer between a solid polymer electrolyte (SPE) membrane and a porous electrode backing. The catalyst layer is preferably less than about 10 .mu.m in thickness with a carbon supported platinum catalyst loading less than about 0.35 mgPt/cm.sup.2. The film is formed as an ink that is spread and cured on a film release blank. The cured film is then transferred to the SPE membrane and hot pressed into the surface to form a catalyst layer having a controlled thickness and catalyst distribution. Alternatively, the catalyst layer is formed by applying a Na.sup.+ form of a perfluorosulfonate ionomer directly to the membrane, drying the film at a high temperature, and then converting the film back to the protonated form of the ionomer. The layer has adequate gas permeability so that cell performance is not affected and has a density and particle distribution effective to optimize proton access to the catalyst and electronic continuity for electron flow from the half-cell reaction occurring at the catalyst.

  2. Oxide Fiber Cathode Materials for Rechargeable Lithium Cells

    NASA Technical Reports Server (NTRS)

    Rice, Catherine E.; Welker, Mark F.

    2008-01-01

    LiCoO2 and LiNiO2 fibers have been investigated as alternatives to LiCoO2 and LiNiO2 powders used as lithium-intercalation compounds in cathodes of rechargeable lithium-ion electrochemical cells. In making such a cathode, LiCoO2 or LiNiO2 powder is mixed with a binder [e.g., poly(vinylidene fluoride)] and an electrically conductive additive (usually carbon) and the mixture is pressed to form a disk. The binder and conductive additive contribute weight and volume, reducing the specific energy and energy density, respectively. In contrast, LiCoO2 or LiNiO2 fibers can be pressed and sintered to form a cathode, without need for a binder or a conductive additive. The inter-grain contacts of the fibers are stronger and have fewer defects than do those of powder particles. These characteristics translate to increased flexibility and greater resilience on cycling and, consequently, to reduced loss of capacity from cycle to cycle. Moreover, in comparison with a powder-based cathode, a fiber-based cathode is expected to exhibit significantly greater ionic and electronic conduction along the axes of the fibers. Results of preliminary charge/discharge-cycling tests suggest that energy densities of LiCoO2- and LiNiO2-fiber cathodes are approximately double those of the corresponding powder-based cathodes.

  3. Autotrophic nitrite removal in the cathode of microbial fuel cells.

    PubMed

    Puig, Sebastià; Serra, Marc; Vilar-Sanz, Ariadna; Cabré, Marina; Bañeras, Lluís; Colprim, Jesús; Balaguer, M Dolors

    2011-03-01

    Nitrification to nitrite (nitritation process) followed by reduction to dinitrogen gas decreases the energy demand and the carbon requirements of the overall process of nitrogen removal. This work studies autotrophic nitrite removal in the cathode of microbial fuel cells (MFCs). Special attention was paid to determining whether nitrite is used as the electron acceptor by exoelectrogenic bacteria (biologic reaction) or by graphite electrodes (abiotic reaction). The results demonstrated that, after a nitrate pulse at the cathode, nitrite was initially accumulated; subsequently, nitrite was removed. Nitrite and nitrate can be used interchangeably as an electron acceptor by exoelectrogenic bacteria for nitrogen reduction from wastewater while producing bioelectricity. However, if oxygen is present in the cathode chamber, nitrite is oxidised via biological or electrochemical processes. The identification of a dominant bacterial member similar to Oligotropha carboxidovorans confirms that autotrophic denitrification is the main metabolism mechanism in the cathode of an MFC. PMID:21262566

  4. Photoconductive Cathode Interlayer for Highly Efficient Inverted Polymer Solar Cells.

    PubMed

    Nian, Li; Zhang, Wenqiang; Zhu, Na; Liu, Linlin; Xie, Zengqi; Wu, Hongbin; Würthner, Frank; Ma, Yuguang

    2015-06-10

    A highly photoconductive cathode interlayer was achieved by doping a 1 wt % light absorber, such as perylene bisimide, into a ZnO thin film, which absorbs a very small amount of light but shows highly increased conductivity of 4.50 × 10(-3) S/m under sunlight. Photovoltaic devices based on this kind of photoactive cathode interlayer exhibit significantly improved device performance, which is rather insensitive to the thickness of the cathode interlayer over a broad range. Moreover, a power conversion efficiency as high as 10.5% was obtained by incorporation of our photoconductive cathode interlayer with the PTB7-Th:PC71BM active layer, which is one of the best results for single-junction polymer solar cells. PMID:26016386

  5. Cathode preparation method for molten carbonate fuel cell

    DOEpatents

    Smith, James L.; Sim, James W.; Kucera, Eugenia H.

    1988-01-01

    A method of preparing a porous cathode structure for use in a molten carbonate fuel cell begins by providing a porous integral plaque of sintered nickel oxide particles. The nickel oxide plaque can be obtained by oxidizing a sintered plaque of nickel metal or by compacting and sintering finely divided nickel oxide particles to the desired pore structure. The porous sintered nickel oxide plaque is contacted with a lithium salt for a sufficient time to lithiate the nickel oxide structure and thus enhance its electronic conductivity. The lithiation can be carried out either within an operating fuel cell or prior to assembling the plaque as a cathode within the fuel cell.

  6. Magnetron cathodes in plasma electrode Pockels cells

    DOEpatents

    Rhodes, M.A.

    1995-04-25

    Magnetron cathodes, which produce high current discharges, form greatly improved plasma electrodes on each side of an electro-optic crystal. The plasma electrode has a low pressure gas region on both sides of the crystal. When the gas is ionized, e.g., by a glow discharge in the low pressure gas, the plasma formed is a good conductor. The gas electrode acts as a highly uniform conducting electrode. Since the plasma is transparent to a high energy laser beam passing through the crystal, the plasma is transparent. A crystal exposed from two sides to such a plasma can be charged up uniformly to any desired voltage. A typical configuration utilizes helium at 50 millitorr operating pressure and 2 kA discharge current. The magnetron cathode produces a more uniform plasma and allows a reduced operating pressure which leads to lower plasma resistivity and a more uniform charge on the crystal. 5 figs.

  7. Magnetron cathodes in plasma electrode pockels cells

    DOEpatents

    Rhodes, Mark A.

    1995-01-01

    Magnetron cathodes, which produce high current discharges, form greatly improved plasma electrodes on each side of an electro-optic crystal. The plasma electrode has a low pressure gas region on both sides of the crystal. When the gas is ionized, e.g., by a glow discharge in the low pressure gas, the plasma formed is a good conductor. The gas electrode acts as a highly uniform conducting electrode. Since the plasma is transparent to a high energy laser beam passing through the crystal, the plasma is transparent. A crystal exposed from two sides to such a plasma can be charged up uniformly to any desired voltage. A typical configuration utilizes helium at 50 millitorr operating. pressure and 2 kA discharge current. The magnetron cathode produces a more uniform plasma and allows a reduced operating pressure which leads to lower plasma resistivity and a more uniform charge on the crystal.

  8. Numerical study of the cathode electrode in the Microfluidic Fuel Cell using agglomerate model

    NASA Astrophysics Data System (ADS)

    Moein-Jahromi, M.; Movahed, S.; Kermani, M. J.

    2015-03-01

    Simulation of the cathode electrode of a Microfluidic Fuel Cell (hereafter MFC) is performed with focus on the electrochemical reaction. Oxygen transport phenomena are modeled from the microchannel inlet to the reaction sites surface (on the platinum particles) in the catalyst layer. The dissolved oxygen in sulfuric acid and the formic acid are considered as the oxidant and the fuel, respectively. The cathode catalyst layer is modeled using the agglomerate model versus the homogenous model which is incapable of predicting concentration loss at high current densities. The results are validated versus the experiments of Choban et al. published in 2004. A set of parametric study is performed to investigate the influence of operating and structural parameters on the cell performance; at the end, a sensitivity analysis is implemented to rank the studied parameters with rank 1 for the most influential parameters. The results indicate that oxygen concentration at the inlet of microchannel within the range 0.1 M-0.7 M is the most influential parameter, and the cell performance can enhance by 2.615 W m-2 at the studied range. The results could be used by the microfluidic fuel cell manufacturers to overcome the current drawbacks of the MFCs.

  9. Co3O4 nanoparticle-modified MnO2 nanotube bifunctional oxygen cathode catalysts for rechargeable zinc-air batteries

    NASA Astrophysics Data System (ADS)

    Du, Guojun; Liu, Xiaogang; Zong, Yun; Hor, T. S. Andy; Yu, Aishui; Liu, Zhaolin

    2013-05-01

    We report the preparation of MnO2 nanotubes functionalized with Co3O4 nanoparticles and their use as bifunctional air cathode catalysts for oxygen reduction reaction and oxygen evolution reaction in rechargeable zinc-air batteries. These hybrid MnO2/Co3O4 nanomaterials exhibit enhanced catalytic reactivity toward oxygen evolution reaction under alkaline conditions compared with that in the presence of MnO2 nanotubes or Co3O4 nanoparticles alone.We report the preparation of MnO2 nanotubes functionalized with Co3O4 nanoparticles and their use as bifunctional air cathode catalysts for oxygen reduction reaction and oxygen evolution reaction in rechargeable zinc-air batteries. These hybrid MnO2/Co3O4 nanomaterials exhibit enhanced catalytic reactivity toward oxygen evolution reaction under alkaline conditions compared with that in the presence of MnO2 nanotubes or Co3O4 nanoparticles alone. Electronic supplementary information (ESI) available: Zinc-air cell device, XPS survey scan and power density of the cell. See DOI: 10.1039/c3nr00300k

  10. Extended Platinum Nanotubes as Fuel Cell Catalysts

    SciTech Connect

    Alia, S.; Pivovar, B. S.; Yan, Y.

    2012-01-01

    Energy consumption has relied principally on fossil fuels as an energy source; fuel cells, however, can provide a clean and sustainable alternative, an answer to the depletion and climate change concerns of fossil fuels. Within proton exchange membrane fuel cells, high catalyst cost and poor durability limit the commercial viability of the device. Recently, platinum nanotubes (PtNTs) were studied as durable, active catalysts, providing a platform to meet US Department of Energy vehicular activity targets.[1] Porous PtNTs were developed to increase nanotube surface area, improving mass activity for oxygen reduction without sacrificing durability.[2] Subsurface platinum was then replaced with palladium, forming platinum-coated palladium nanotubes.[3] By forming a core shell structure, platinum utilization was increased, reducing catalyst cost. Alternative substrates have also been examined, modifying platinum surface facets and increasing oxygen reduction specific activity. Through modification of the PtNT platform, catalyst limitations can be reduced, ensuring a commercially viable device.

  11. Cathode side hardware for carbonate fuel cells

    DOEpatents

    Xu, Gengfu; Yuh, Chao-Yi

    2011-04-05

    Carbonate fuel cathode side hardware having a thin coating of a conductive ceramic formed from one of Perovskite AMeO.sub.3, wherein A is at least one of lanthanum and a combination of lanthanum and strontium and Me is one or more of transition metals, lithiated NiO (Li.sub.xNiO, where x is 0.1 to 1) and X-doped LiMeO.sub.2, wherein X is one of Mg, Ca, and Co.

  12. Functionally graded composite cathodes for solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Hart, N. T.; Brandon, N. P.; Day, M. J.; Lapeña-Rey, N.

    Functionally graded solid oxide fuel cell (SOFC) cathodes have been prepared from mixtures of strontium-doped lanthanum manganite (LSM) and gadolinia-doped ceria (CGO) using slurry spraying techniques. Similar samples were also prepared from mixtures of LSM and ytrria-stabilised zirconia (YSZ). A current collector comprising a mixture of LSM and strontium-doped lanthanum cobaltite (LSCO) was then applied to both cathode types. Samples were characterised using scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). Characterisation using EIS techniques showed that cathodes incorporating CGO into the structure gave improved performance over those fabricated using YSZ. These performance gains were most noticeable as the temperature was decreased towards 700 °C, and were maintained during the testing of three cell membrane electrode assemblies fabricated to the Rolls-Royce design.

  13. Fuel cell having dual electrode anode or cathode

    DOEpatents

    Findl, E.

    1984-04-10

    A fuel cell that is characterized by including a dual electrode anode that is operable to simultaneously electro-oxidize a gaseous fuel and a liquid fuel. In alternative embodiments, a fuel cell having a single electrode anode is provided with a dual electrode cathode that is operable to simultaneously reduce a gaseous oxidant and a liquid oxidant to electro-oxidize a fuel supplied to the cell.

  14. Fuel cell having dual electrode anode or cathode

    DOEpatents

    Findl, Eugene

    1985-01-01

    A fuel cell that is characterized by including a dual electrode anode that is operable to simultaneously electro-oxidize a gaseous fuel and a liquid fuel. In alternative embodiments, a fuel cell having a single electrode anode is provided with a dual electrode cathode that is operable to simultaneously reduce a gaseous oxidant and a liquid oxidant to electro-oxidize a fuel supplied to the cell.

  15. Catalysts compositions for use in fuel cells

    SciTech Connect

    Chuang, Steven S.C.

    2015-12-01

    The present invention generally relates to the generation of electrical energy from a solid-state fuel. In one embodiment, the present invention relates to a solid-oxide fuel cell for generating electrical energy from a carbon-based fuel, and to catalysts for use in a solid-oxide fuel cell.

  16. Influence of the cathode architecture in the frequency response of self-breathing proton exchange membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Ferreira-Aparicio, P.; Chaparro, A. M.

    2014-12-01

    Self-breathing proton exchange membrane fuel cells are apparently simple devices, but efficient water management is critical for their performance. The cathode configuration should guarantee balanced rates between O2 accessibility from the circumventing air and H2O removal, and a good electric contact between catalyst layers and current collectors at the same time. By applying progressive modifications to the initial concept of a conventional PEMFC, the effect of the cathode architecture on cell performance has been analyzed. Frequency response analyses of the cell during steady-state potentiostatic stepping have yielded relevant information regarding limitations originated by the cathode impedance under high current load conditions. The primitive cell design has been optimized for self-breathing operation by means of this diagnostic tool. The thickness of the perforated plate in the cathode has been found to be one of the main factors contributing to limit oxygen accessibility when a high current load is demanded. Adequate cathode architecture is critical for reducing mass transport limitations in the catalytic layer and enhancing performance under self-breathing conditions.

  17. Molybdenum In Cathodes Of Sodium/Metal Chloride Cells

    NASA Technical Reports Server (NTRS)

    Bugga, Ratnakumar V.; Attia, Alan I.; Halpert, Gerald

    1992-01-01

    Cyclic voltammetric curves of molybdenum wire in NaAlCl4 melt indicate molybdenum chloride useful as cathode material in rechargeable sodium/metal chloride electrochemical cells. Batteries used in electric vehicles, for electric-power load leveling, and other applications involving high energy and power densities.

  18. Efficient Pt catalysts for polymer electrolyte fuel cells

    SciTech Connect

    Fournier, J.; Gaubert, G.; Tilquin, J.Y.

    1996-12-31

    Commercialization of polymer electrolyte fuel cells (PEFCs) requires an important decrease in their production cost. Cost reduction for the electrodes principally concerns the decrease in the amount of Pt catalyst necessary for the functioning of the PEFC without affecting cell performance. The first PEFCs used in the Gemini Space Program had a loading of 4-10 mg pt/cm{sup 2}. The cost of the electrodes was drastically reduced when pure colloidal Pt was replaced by Pt supported on carbon (Pt/C) with a Pt content of 0.4 Mg/cm{sup 2}. Since the occurrence of that breakthrough, many studies have been aimed at further lowering the Pt loading. Today, the lowest loadings reported for oxygen reduction are of the order of 0.05 mg pt/cm{sup 2}. The carbon support of commercial catalysts is Vulcan XC-72 from Cabot, a carbon black with a specific area of 254 m{sup 2}/g. Graphites with specific areas ranging from 20 to 305 m{sup 2}/g are now available from Lonza. The first aim of the present study was to determine the catalytic properties for 02 reduction of Pt supported on these high specific area graphites. The second aim was to use Pt inclusion synthesis on these high area graphites, and to measure the catalytic performances of these materials. Lastly, this same Pt-inclusion synthesis was extended even for use with Vulcan and Black Pearls as substrates (two carbon blacks from Cabot). All these catalysts have been labelled Pt-included materials to distinguish them from the Pt-supported ones. It will be shown that the reduced Pt content Pt-included materials obtained with high specific area substrates a are excellent catalysts for oxygen reduction, especially at high currents. Therefore, Pt inclusion synthesis appears to be a new method to decrease the cathodic Pt loading.

  19. Lithium ferrate and lithium cobaltate cathodes for molten carbonate fuel cells

    SciTech Connect

    Krumpelt, M.; Roche, M.; Bloom, I.; Indacochea, J.E.; Kucera, G.

    1994-08-01

    The objective of this research is to develop cathodes for the molten carbonate fuel cells (MCFC) having a performance approaching that of the lithiated nickel oxide cathode and a significantly greater life, particularly in pressurized MCFCs. To meet this objective, cathodes containing either doubly doped lithium ferrate or lithium cobaltate are being developed. In this project, the authors are optimizing the composition, microstructure, and loading density of the doubly doped lithium ferrate cathode and the lithium cobaltate cathodes.

  20. Fuel Cell Cathode Contamination: Comparison of Prevention Strategies and their Viability

    NASA Astrophysics Data System (ADS)

    Tejaswi, Arjun

    Fuel cells are a major area of research in ongoing efforts to find alternate sources of energy. Today these efforts have become ever the more necessary in the face of spiraling costs of conventional sources of energy and concerns about global warming. Most fuel cells consume hydrogen to produce, for the most part, only water in their exhaust. They are also capable of achieving significantly higher efficiencies than conventional automobile internal combustion engines. Since cost still remains one of the most intractable challenges to the advent of fuel cells, it is imperative that every effort be made to lower the costs of fuel cell production, operation and maintenance as well as improving overall efficiency. The air circulation system of a fuel cell is designed to provide oxygen to the cathode of the fuel cell. Air taken from the surroundings, however, often contains pollutants including dust, SO2, NO 2 and various other gases. These gases may severely degrade various components of system, especially for polymer electrolyte membrane (PEM) type fuel cells, including the catalyst, membrane electrode assembly and other components. Moreover, these pollutants may lead to specific behavior based on ambient air composition at the test site thereby confusing researchers. In order to address these issues, this study seeks to identify these pollutants and examine the mitigation strategies to mitigate them. Also discussed is whether these pollutants have an effect debilitating enough to justify the extra cost and potential parasitic losses associated with these mitigation strategies. Adsorptive filtration is identified as the most appropriate cathode side air quality system for fuel cells. Performance of cathode side fuel cell filters are examined under varying relative humidity, temperature, air flow rate and pollutant concentration conditions. An estimated filter survival time under realistic conditions is also suggested.

  1. Electrocatalysis for dioxygen reduction by a μ-oxo decavanadium complex in alkaline medium and its application to a cathode catalyst in air batteries

    NASA Astrophysics Data System (ADS)

    Dewi, Eniya Listiani; Oyaizu, Kenichi; Nishide, Hiroyuki; Tsuchida, Eishun

    The redox behavior of a decavanadium complex [(VO) 10(μ 2-O) 9(μ 3-O) 3(C 5H 7O 2) 6] ( 1) was studied using cyclic voltammetry under acidic and basic conditions. The reduction potential of V(V) was found at less positive potentials for higher pH electrolyte solutions. The oxygen reduction at complex 1 immobilized on a modified electrode was examined using cyclic voltammetry and rotating ring-disk electrode techniques in the 1 M KOH solutions. On the basis of measurements using a rotating disk electrode (RDE), the complex 1 was found to be highly active for the direct four-electron reduction of dioxygen at -0.2 V versus saturated calomel electrode (SCE). The complex 1 as a reduction catalyst of O 2 with a high selectivity was demonstrated using rotating ring-disk voltammograms in alkaline solutions. The application of complex 1 as an oxygen reduction catalyst at the cathode of zinc-air cell was also examined. The zinc-air cell with the modified electrode showed a stable discharge potential at approximately 1 V with discharge capacity of 80 mAh g -1 which was about five times larger than that obtained with the commonly used manganese dioxide catalyst.

  2. Cells having cathodes with thiocyanogen-containing cathode-active materials

    SciTech Connect

    Rao, B.M.

    1980-03-11

    An electric current-producing cell which contains: (A) an anode metal higher than hydrogen in the electromotive series and having an atomic number no greater than 30; (B) a cathode material containing thiocyanogen, said material being selected from the group consisting of: (I) thiocyanogen of the formula: (ScN)/sub 2/ (II) parathiocyanogen of the formula: (ScN)/sub x/ wherein X is greater than 2; (III) halothiocyanogen of the formula: YScN wherein Y is a halogen selected from the group consisting of F, Cl, Br and I; (IV) parahalothiocyanogen of the formula: (YScN)/sub y/ wherein Y is as described above and wherein Y is equal to or greater than 2; (V) perthiocyanogen complex of an amine; (VI) perthiocyanogen complex of an ammonium ion; (VII) thiocyanogen complex of a metal cation which is the same as the metal cation in the anode; (VIII) thiocyanogen complex of a metal cation which is higher in the electromotive series than the metal cation in the anode; (IX) cathode intercalated material having halothiocyanogen of paragraph (III) above intercalated therein; (X) cathode intercalated material having parahalothiocyanogen of paragraph (IV) above intercalated therein; (XI) polymeric thiocyanogen-containing material obtained from oxidation of a polyvinyl thiocyanate; (XII) ammonium thiocyanate salt complex of thiocyanogen of paragraph (I) above; (XIII) ammonium thiocyanate salt complex of parathiocyanogen of paragraph (II) above; (XIV) ammonium thiocyanate salt complex of halothiocyanogen of paragraph (III) above; and (XV) ammonium thiocyanate salt complex of parahalothiocyanogen of paragraph (IV) above; and (C) an electrolyte which is chemically inert with respect to said anode and said cathode.

  3. Inert Anode/Cathode Program: Fiscal Year 1986 annual report. [For Hall-Heroult cells

    SciTech Connect

    Brenden, B.B.; Davis, N.C.; Koski, O.H.; Marschman, S.C.; Pool, K.H.; Schilling, C.H.; Windisch, C.F.; Wrona, B.J.

    1987-06-01

    Purpose of the program is to develop long-lasting, energy-efficient anodes, cathodes, and ancillary equipment for Hall-Heroult cells used by the aluminum industry. The program is divided into four tasks: Inert Anode Development, Cathode Materials Evaluation, Cathode Bonding Development, and Sensor Development. To devise sensors to control the chemistry of Hall-Heroult cells using stable anodes and cathodes. This report highlights the major FY86 technical accomplishments, which are presented in the following sections: Management, Materials Development, Materials Evaluation, Thermodynamic Evaluation, Laboratory Cell Tests, Large-Scale Tests, Cathode Materials Evaluation, Cathode Bonding Development, and Sensor Development.

  4. TOPICAL REVIEW: Nanostructured catalysts in fuel cells

    NASA Astrophysics Data System (ADS)

    Zhong, Chuan-Jian; Luo, Jin; Fang, Bin; Wanjala, Bridgid N.; Njoki, Peter N.; Loukrakpam, Rameshwori; Yin, Jun

    2010-02-01

    One of the most important challenges for the ultimate commercialization of fuel cells is the preparation of active, robust, and low-cost catalysts. This review highlights some findings of our investigations in the last few years in developing advanced approaches to nanostructured catalysts that address this challenge. Emphasis is placed on nanoengineering-based fabrication, processing, and characterization of multimetallic nanoparticles with controllable size (1-10 nm), shape, composition (e.g. MlnM2100-n, M1nM2mM3100-n-m, M1@M2, where M (1 or 2) = Pt, Co, Ni, V, Fe, Cu, Pd, W, Ag, Au etc) and morphology (e.g. alloy, core@shell etc). In addition to an overview of the fundamental issues and the recent progress in fuel cell catalysts, results from evaluations of the electrocatalytic performance of nanoengineered catalysts in fuel cell reactions are discussed. This approach differs from other traditional approaches to the preparation of supported catalysts in the ability to control the particle size, composition, phase, and surface properties. An understanding of how the nanoscale properties of the multimetallic nanoparticles differ from their bulk-scale counterparts, and how the interaction between the nanoparticles and the support materials relates to the size sintering or evolution in the thermal activation process, is also discussed. The fact that the bimetallic gold-platinum nanoparticle system displays a single-phase character different from the miscibility gap known for its bulk-scale counterpart serves as an important indication of the nanoscale manipulation of the structural properties, which is useful for refining the design and preparation of the bimetallic catalysts. The insight gained from probing how nanoparticle-nanoparticle and nanoparticle-substrate interactions relate to the size evolution in the activation process of nanoparticles on planar substrates serves as an important guiding principle in the control of nanoparticle sintering on different

  5. Effects of Membrane- and Catalyst-layer-thickness Nonuniformitiesin Polymer-electrolyte Fuel Cells

    SciTech Connect

    Weber, Adam Z.; Newman, John

    2006-09-01

    In this paper, results from mathematical, pseudo 2-D simulations are shown for four different along-the-channel thickness distributions of both the membrane and cathode catalyst layer. The results and subsequent analysis clearly demonstrate that for the membrane thickness distributions, cell performance is affected a few percent under low relative-humidity conditions and that the position along the gas channel is more important than the local thickness variations. However, for the catalyst-layer thickness distributions, global performance is not impacted, although for saturated conditions there is a large variability in the local temperature and performance depending on the thickness.

  6. Nanostructured Catalyst Systems for Fuel Cells: Synthesis and Characterization of Low Platinum Content Electrocatalysts for O{sub 2} Reduction

    SciTech Connect

    Adzic, Radoslav

    2007-02-01

    The objective of this project is to synthesize and characterize new O{sub 2} reduction catalysts with enhanced activity and ultra low Pt loading, and to test them in membrane electrode assemblies (MEAs) to determine their performance under fuel cell cathode operating conditions.

  7. Lithium-ferrate-based cathodes for molten carbonate fuel cells

    SciTech Connect

    Lanagan, M.T.; Bloom, I.; Kaun, T.D.

    1996-12-31

    Argonne National Laboratory is developing advanced cathodes for pressurized operation of the molten carbonate fuel cell (MCFC) at {approximately}650{degrees}C. To be economically viable for stationary power generation, molten carbonate fuel cells must have lifetimes of more than 25,000 h while exhibiting superior cell performance. In the present technology, lithiated NiO is used as the cathode. Over the lifetime of the cell, however, N{sup 2+} ions tend to transport to the anode, where they are reduced to metallic Ni. With increased CO{sub 2} partial pressure, the transport of Ni increases because of the increased solubility of NiO in the carbonate electrolyte. Although this process is slow in MCFCs operated at 1 atm and a low CO{sub 2} partial pressure (about 0.1 atm), transport of nickel to the anode may be excessive at a higher pressure (e.g., 3 atm) and a high CO{sub 2} partial pressure (e.g., about 0.3 arm). This transport is expected to lead eventually to poor MCFC performance and/or short circuiting. Several alternative cathode compositions have been explored to reduce cathode solubility in the molten salt electrolyte. For example, LiCoO{sub 2} has been studied extensively as a potential cathode material. The LiCoO{sub 2} cathode has a low resistivity, about 10-cm, and can be used as a direct substitute for NiO. Argonne is developing advanced cathodes based on lithium ferrate (LiFeO{sub 2}), which is attractive because of its very low solubility in the molten (Li,K){sub 2}CO{sub 3} electrolyte. Because of its high resistivity (about 3000-cm), however, LiFeO{sub 2} cannot be used as a direct substitute for NiO. Cation substitution is, therefore, necessary to decrease resistivity. We determined the effect of cation substitution on the resistivity and deformation of LiFeO{sub 2}. The substituents were chosen because their respective oxides as well as LiFeO{sub 2} crystallize with the rock-salt structure.

  8. Model of cathode reaction resistance in molten carbonate fuel cells

    SciTech Connect

    Morita, H.; Mugikura, Y.; Izaki, Y.; Watanabe, T.; Abe, T.

    1998-05-01

    A model of the performance of a molten carbonate fuel cell (MCFC) is required to estimate the efficiency of an MCFC power plant or to simulate the internal state of a stack. The model should provide an accurate representation of the performance under various operating conditions. However, the performance estimated by previous models has been found to deviate from the measured performance under low oxygen and carbon dioxide cathode partial pressures. To solve this problem, the authors carried out a systematic analysis of the performance of several bench-scale cells operated under various cathode gas conditions and investigated a model of cathode polarization according to the oxygen reduction mechanism in molten carbonate. As a result, it has been clarified that the behavior of cathode polarization under various conditions is described well by the dependence of mixed diffusion of superoxide ion O{sub 2}{sup {minus}} and CO{sub 2} in the melt on the assumed partial pressures at each total operating pressure.

  9. Nanoscale alloying effect of gold-platinum nanoparticles as cathode catalysts on the performance of a rechargeable lithium-oxygen battery

    NASA Astrophysics Data System (ADS)

    Yin, Jun; Fang, Bin; Luo, Jin; Wanjala, Bridgid; Mott, Derrick; Loukrakpam, Rameshowri; Ng, Mei Shan; Li, Zheng; Hong, Jian; Whittingham, M. Stanley; Zhong, Chuan-Jian

    2012-08-01

    The understanding of nanoscale alloying or the phase segregation effect of alloy nanoparticles on the catalytic properties is important for a rational design of the desired catalysts for a specific reaction. This paper describes findings of an investigation into this type of structural effect for carbon-supported bimetallic gold-platinum nanoparticles as cathode catalysts in a rechargeable lithium-oxygen battery. The nanoscale structural characteristics in terms of size, alloying and phase segregation were shown to affect the catalytic properties of the catalysts in the Li-O2 battery. In addition to the composition effect, the catalysts with a fully alloyed phase structure were found to exhibit a smaller discharge-charge voltage difference and a higher discharge capacity than those with a partial phase segregation structure. This finding is significant for the design of alloy nanoparticles as air cathode catalysts in rechargeable lithium-air batteries, demonstrating the importance of the control of the nanoscale composition and phase properties.

  10. Pt-Ni and Pt-Co Catalyst Synthesis Route for Fuel Cell Applications

    NASA Technical Reports Server (NTRS)

    Firdosy, Samad A.; Ravi, Vilupanur A.; Valdez, Thomas I.; Kisor, Adam; Narayan, Sri R.

    2013-01-01

    Oxygen reduction reactions (ORRs) at the cathode are the rate-limiting step in fuel cell performance. The ORR is 100 times slower than the corresponding hydrogen oxidation at the anode. Speeding up the reaction at the cathode will improve fuel cell efficiency. The cathode material is generally Pt powder painted onto a substrate (e.g., graphite paper). Recent efforts in the fuel cell area have focused on replacing Pt with Pt-X alloys (where X = Co, Ni, Zr, etc.) in order to (a) reduce cost, and (b) increase ORR rates. One of these strategies is to increase ORR rates by reducing the powder size, which would result in an increase in the surface area, thereby facilitating faster reaction rates. In this work, a process has been developed that creates Pt-Ni or Pt-Co alloys that are finely divided (on the nano scale) and provide equivalent performance at lower Pt loadings. Lower Pt loadings will translate to lower cost. Precursor salts of the metals are dissolved in water and mixed. Next, the salt mixtures are dried on a hot plate. Finally, the dried salt mixture is heattreated in a furnace under flowing reducing gas. The catalyst powder is then used to fabricate a membrane electrode assembly (MEA) for electrochemical performance testing. The Pt- Co catalyst-based MEA showed comparable performance to an MEA fabri cated using a standard Pt black fuel cell catalyst. The main objective of this program has been to increase the overall efficiencies of fuel cell systems to support power for manned lunar bases. This work may also have an impact on terrestrial programs, possibly to support the effort to develop a carbon-free energy source. This catalyst can be used to fabricate high-efficiency fuel cell units that can be used in space as regenerative fuel cell systems, and terrestrially as primary fuel cells. Terrestrially, this technology will become increasingly important when transition to a hydrogen economy occurs.

  11. Method of depositing a catalyst on a fuel cell electrode

    DOEpatents

    Dearnaley, Geoffrey; Arps, James H.

    2000-01-01

    Fuel cell electrodes comprising a minimal load of catalyst having maximum catalytic activity and a method of forming such fuel cell electrodes. The method comprises vaporizing a catalyst, preferably platinum, in a vacuum to form a catalyst vapor. A catalytically effective amount of the catalyst vapor is deposited onto a carbon catalyst support on the fuel cell electrode. The electrode preferably is carbon cloth. The method reduces the amount of catalyst needed for a high performance fuel cell electrode to about 0.3 mg/cm.sup.2 or less.

  12. Tolerance of non-platinum group metals cathodes proton exchange membrane fuel cells to air contaminants

    NASA Astrophysics Data System (ADS)

    Reshetenko, Tatyana; Serov, Alexey; Artyushkova, Kateryna; Matanovic, Ivana; Sarah Stariha; Atanassov, Plamen

    2016-08-01

    The effects of major airborne contaminants (SO2, NO2 and CO) on the spatial performance of Fe/N/C cathode membrane electrode assemblies were studied using a segmented cell system. The injection of 2-10 ppm SO2 in air stream did not cause any performance decrease and redistribution of local currents due to the lack of stably adsorbed SO2 molecules on Fe-Nx sites, as confirmed by density functional theory (DFT) calculations. The introduction of 5-20 ppm of CO into the air stream also did not affect fuel cell performance. The exposure of Fe/N/C cathodes to 2 and 10 ppm NO2 resulted in performance losses of 30 and 70-75 mV, respectively. DFT results showed that the adsorption energies of NO2 and NO were greater than that of O2, which accounted for the observed voltage decrease and slight current redistribution. The cell performance partially recovered when the NO2 injection was stopped. The long-term operation of the fuel cells resulted in cell performance degradation. XPS analyses of Fe/N/C electrodes revealed that the performance decrease was due to catalyst degradation and ionomer oxidation. The latter was accelerated in the presence of air contaminants. The details of the spatial performance and electrochemical impedance spectroscopy results are presented and discussed.

  13. Characterization and optimization of cathodic conditions for H2O2 synthesis in microbial electrochemical cells

    EPA Science Inventory

    Cathode potential and O2 supply methods were investigated to improve H2O2 synthesis in an electrochemical cell, and optimal cathode conditions were applied for microbial electrochemical cells (MECs). Using aqueous O2 for the cathode significantly improved current density, but H2...

  14. Doped lanthanum nickelates with a layered perovskite structure as bifunctional cathode catalysts for rechargeable metal-air batteries.

    PubMed

    Jung, Kyu-Nam; Jung, Jong-Hyuk; Im, Won Bin; Yoon, Sukeun; Shin, Kyung-Hee; Lee, Jong-Won

    2013-10-23

    Rechargeable metal-air batteries have attracted a great interest in recent years because of their high energy density. The critical challenges facing these technologies include the sluggish kinetics of the oxygen reduction-evolution reactions on a cathode (air electrode). Here, we report doped lanthanum nickelates (La2NiO4) with a layered perovskite structure that serve as efficient bifunctional electrocatalysts for oxygen reduction and evolution in an aqueous alkaline electrolyte. Rechargeable lithium-air and zinc-air batteries assembled with these catalysts exhibit remarkably reduced discharge-charge voltage gaps (improved round-trip efficiency) as well as high stability during cycling. PMID:24053465

  15. Integrating NiCo Alloys with Their Oxides as Efficient Bifunctional Cathode Catalysts for Rechargeable Zinc-Air Batteries.

    PubMed

    Liu, Xien; Park, Minjoon; Kim, Min Gyu; Gupta, Shiva; Wu, Gang; Cho, Jaephil

    2015-08-10

    The lack of high-efficient, low-cost, and durable bifunctional electrocatalysts that act simultaneously for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) is currently one of the major obstacles to commercializing the electrical rechargeability of zinc-air batteries. A nanocomposite CoO-NiO-NiCo bifunctional electrocatalyst supported by nitrogen-doped multiwall carbon nanotubes (NCNT/CoO-NiO-NiCo) exhibits excellent activity and stability for the ORR/OER in alkaline media. More importantly, real air cathodes made from the bifunctional NCNT/CoO-NiO-NiCo catalysts further demonstrated superior performance to state-of-the-art Pt/C or Pt/C+IrO2 catalysts in primary and rechargeable zinc-air batteries. PMID:26118973

  16. Ruthenium oxide modified titanium dioxide nanotube arrays as carbon and binder free lithium-air battery cathode catalyst

    NASA Astrophysics Data System (ADS)

    Zhao, Guangyu; Niu, Yanning; Zhang, Li; Sun, Kening

    2014-12-01

    RuO2 modified TiO2 nanotube arrays, growing on Ti foams, are used as carbon and binder free cathodes for Li-O2 batteries. The micrometer pores in Ti foams and nanometer pores in TiO2 nanotubes supply facilitated transport channels for oxygen diffusing into/out of the catalysts in discharge and charge processes. The RuO2 catalyst exhibits outstanding catalytic active toward oxygen evolution reaction (OER), which leads the charge voltage maintaining around 3.7 V all through the battery cycling. The stability of TiO2/Ti support, abundant oxygen transport path and favorable catalytic activity of RuO2 toward OER enable the Li-O2 batteries exhibiting 130 cycle discharge/charge.

  17. Functionally Graded Cathodes for Solid Oxide Fuel Cells

    SciTech Connect

    Harry Abernathy; Meilin Liu

    2006-12-31

    One primary suspected cause of long-term performance degradation of solid oxide fuels (SOFCs) is the accumulation of chromium (Cr) species at or near the cathode/electrolyte interface due to reactive Cr molecules originating from Cr-containing components (such as the interconnect) in fuel cell stacks. To date, considerable efforts have been devoted to the characterization of cathodes exposed to Cr sources; however, little progress has been made because a detailed understanding of the chemistry and electrochemistry relevant to the Cr-poisoning processes is still lacking. This project applied multiple characterization methods - including various Raman spectroscopic techniques and various electrochemical performance measurement techniques - to elucidate and quantify the effect of Cr-related electrochemical degradation at the cathode/electrolyte interface. Using Raman microspectroscopy the identity and location of Cr contaminants (SrCrO{sub 4}, (Mn/Cr){sub 3}O{sub 4} spinel) have been observed in situ on an LSM cathode. These Cr contaminants were shown to form chemically (in the absence of current flowing through the cell) at temperatures as low as 625 C. While SrCrO{sub 4} and (Mn/Cr){sub 3}O{sub 4} spinel must preferentially form on LSM, since the LSM supplies the Sr and Mn cations necessary for these compounds, LSM was also shown to be an active site for the deposition of Ag{sub 2}CrO{sub 4} for samples that also contained silver. In contrast, Pt and YSZ do not appear to be active for formation of Cr-containing phases. The work presented here supports the theory that Cr contamination is predominantly chemically-driven and that in order to minimize the effect, cathode materials should be chosen that are free of cations/elements that could preferentially react with chromium, including silver, strontium, and manganese.

  18. Investigation of carbon supported Pd-Cu nanoparticles as anode catalysts for direct borohydride fuel cell

    NASA Astrophysics Data System (ADS)

    Behmenyar, Gamze; Akın, Ayşe Nilgün

    2014-03-01

    Carbon supported Pd and bimetallic Pd-Cu nanoparticles with different compositions are prepared by a modified polyol method and used as anode catalysts for direct borohydride fuel cell (DBFC). The physical and electrochemical properties of the as-prepared electrocatalysts are investigated by transmission electron microscopy (TEM), X-ray diffraction (XRD), ICP-AES, cyclic voltammetry (CV), chronoamperometry (CA), and fuel cell experiments. The results show that the carbon supported Pd-Cu bimetallic catalysts have much higher catalytic activity for the direct oxidation of BH4- than the carbon supported pure nanosized Pd catalyst, especially the Pd50Cu50/C catalyst presents the highest catalytic activity among all as-prepared catalysts, and the DBFC using Pd50Cu50/C as anode catalyst and Pt/C as cathode catalyst gives the best performance, and the maximum power density is 98 mW cm-2 at a current density of 223 mA cm-2 at 60 °C.

  19. Investigating Microbial Fuel Cell Bioanode Performance Under Different Cathode Conditions

    SciTech Connect

    Borole, Abhijeet P; Hamilton, Choo Yieng; Aaron, D; Tsouris, Costas

    2009-01-01

    A compact, three-in-one, flow-through, porous, electrode design with minimal electrode spacing and minimal dead volume was implemented to develop a microbial fuel cell (MFC) with improved anode performance. A biofilm-dominated anode consortium enriched under a multimode, continuous-flow regime was used. The increase in the power density of the MFC was investigated by changing the cathode (type, as well as catholyte strength) to determine whether anode was limiting. The power density obtained with an air-breathing cathode was 56 W/m3 of net anode volume (590 mW/m2) and 203 W/m3 (2160 mW/m2) with a 50-mM ferricyanide- based cathode. Increasing the ferricyanide concentration and ionic strength further increased the power density, reaching 304 W/m3 (3220 mW/m2, with 200 mM ferricyanide and 200 mM buffer concentration). The increasing trend in the power density indicated that the anode was not limiting and that higher power densities could be obtained using cathodes capable of higher rates of oxidation. The internal solution resistance for the MFC was 5 6 X, which supported the improved performance of the anode design. A new parameter defined as the ratio of projected surface area to total anode volume is suggested as a design parameter to relate volumetric and area-based power densities and to enable comparison of various MFC configurations.

  20. Galvanic Cells: Anodes, Cathodes, Signs and Charges

    ERIC Educational Resources Information Center

    Goodwin, Alan

    2011-01-01

    Electrochemistry is a difficult subject for students at school and beyond and even for their teachers. This article explores the difficult "truth" that, when a current flows from a galvanic cell, positive ions within the cell electrolyte move towards the electrode labelled positive. This seems to contravene the basic rule that like charges repel…

  1. Effect of catalyst layer defects on local membrane degradation in polymer electrolyte fuel cells

    NASA Astrophysics Data System (ADS)

    Tavassoli, Arash; Lim, Chan; Kolodziej, Joanna; Lauritzen, Michael; Knights, Shanna; Wang, G. Gary; Kjeang, Erik

    2016-08-01

    Aiming at durability issues of fuel cells, this research is dedicated to a novel experimental approach in the analysis of local membrane degradation phenomena in polymer electrolyte fuel cells, shedding light on the potential effects of manufacturing imperfections on this process. With a comprehensive review on historical failure analysis data from field operated fuel cells, local sources of iron oxide contaminants, catalyst layer cracks, and catalyst layer delamination are considered as potential candidates for initiating or accelerating the local membrane degradation phenomena. Customized membrane electrode assemblies with artificial defects are designed, fabricated, and subjected to membrane accelerated stress tests followed by extensive post-mortem analysis. The results reveal a significant accelerating effect of iron oxide contamination on the global chemical degradation of the membrane, but dismiss local traces of iron oxide as a potential stressor for local membrane degradation. Anode and cathode catalyst layer cracks are observed to have negligible impact on the membrane degradation phenomena. Notably however, distinct evidence is found that anode catalyst layer delamination can accelerate local membrane thinning, while cathode delamination has no apparent effect. Moreover, a substantial mitigating effect for platinum residuals on the site of delamination is observed.

  2. Electricity generation of microbial fuel cell with waterproof breathable membrane cathode

    NASA Astrophysics Data System (ADS)

    Xing, Defeng; Tang, Yu; Mei, Xiaoxue; Liu, Bingfeng

    2015-12-01

    Simplification of fabrication and reduction of capital cost are important for scale-up and application of microbial electrochemical systems (MES). A fast and inexpensive method of making cathode was developed via assembling stainless steel mesh (SSM) with waterproof breathable membrane (WBM). Three assemble types of cathodes were fabricated; Pt@SSM/WBM (SSM as cathode skeleton, WBM as diffusion layer, platinum (Pt) catalyst applied on SSM), SSM/Pt@WBM and Pt@WBM. SSM/Pt@WBM cathode showed relatively preferable with long-term stability and favorable power output (24.7 W/m3). Compared to conventional cathode fabrication, air-cathode was made for 0.5 h. The results indicated that the novel fabrication method could remarkably reduce capital cost and simplify fabrication procedures with a comparable power output, making MFC more prospective for future application.

  3. Fuel Cell Stations Automate Processes, Catalyst Testing

    NASA Technical Reports Server (NTRS)

    2010-01-01

    Glenn Research Center looks for ways to improve fuel cells, which are an important source of power for space missions, as well as the equipment used to test fuel cells. With Small Business Innovation Research (SBIR) awards from Glenn, Lynntech Inc., of College Station, Texas, addressed a major limitation of fuel cell testing equipment. Five years later, the company obtained a patent and provided the equipment to the commercial world. Now offered through TesSol Inc., of Battle Ground, Washington, the technology is used for fuel cell work, catalyst testing, sensor testing, gas blending, and other applications. It can be found at universities, national laboratories, and businesses around the world.

  4. Graphene-Supported Platinum Catalyst-Based Membrane Electrode Assembly for PEM Fuel Cell

    NASA Astrophysics Data System (ADS)

    Devrim, Yilser; Albostan, Ayhan

    2016-08-01

    The aim of this study is the preparation and characterization of a graphene-supported platinum (Pt) catalyst for proton exchange membrane fuel cell (PEMFC) applications. The graphene-supported Pt catalysts were prepared by chemical reduction of graphene and chloroplatinic acid (H2PtCl6) in ethylene glycol. X-ray powder diffraction, thermogravimetric analysis (TGA) and scanning electron microscopy have been used to analyze structure and surface morphology of the graphene-supported catalyst. The TGA results showed that the Pt loading of the graphene-supported catalyst was 31%. The proof of the Pt particles on the support surfaces was also verified by energy-dispersive x-ray spectroscopy analysis. The commercial carbon-supported catalyst and prepared Pt/graphene catalysts were used as both anode and cathode electrodes for PEMFC at ambient pressure and 70°C. The maximum power density was obtained for the Pt/graphene-based membrane electrode assembly (MEA) with H2/O2 reactant gases as 0.925 W cm2. The maximum current density of the Pt/graphene-based MEA can reach 1.267 and 0.43 A/cm2 at 0.6 V with H2/O2 and H2/air, respectively. The MEA prepared by the Pt/graphene catalyst shows good stability in long-term PEMFC durability tests. The PEMFC cell voltage was maintained at 0.6 V without apparent voltage drop when operated at 0.43 A/cm2 constant current density and 70°C for 400 h. As a result, PEMFC performance was found to be superlative for the graphene-supported Pt catalyst compared with the Pt/C commercial catalyst. The results indicate the graphene-supported Pt catalyst could be utilized as the electrocatalyst for PEMFC applications.

  5. Graphene-Supported Platinum Catalyst-Based Membrane Electrode Assembly for PEM Fuel Cell

    NASA Astrophysics Data System (ADS)

    Devrim, Yilser; Albostan, Ayhan

    2016-06-01

    The aim of this study is the preparation and characterization of a graphene-supported platinum (Pt) catalyst for proton exchange membrane fuel cell (PEMFC) applications. The graphene-supported Pt catalysts were prepared by chemical reduction of graphene and chloroplatinic acid (H2PtCl6) in ethylene glycol. X-ray powder diffraction, thermogravimetric analysis (TGA) and scanning electron microscopy have been used to analyze structure and surface morphology of the graphene-supported catalyst. The TGA results showed that the Pt loading of the graphene-supported catalyst was 31%. The proof of the Pt particles on the support surfaces was also verified by energy-dispersive x-ray spectroscopy analysis. The commercial carbon-supported catalyst and prepared Pt/graphene catalysts were used as both anode and cathode electrodes for PEMFC at ambient pressure and 70°C. The maximum power density was obtained for the Pt/graphene-based membrane electrode assembly (MEA) with H2/O2 reactant gases as 0.925 W cm2. The maximum current density of the Pt/graphene-based MEA can reach 1.267 and 0.43 A/cm2 at 0.6 V with H2/O2 and H2/air, respectively. The MEA prepared by the Pt/graphene catalyst shows good stability in long-term PEMFC durability tests. The PEMFC cell voltage was maintained at 0.6 V without apparent voltage drop when operated at 0.43 A/cm2 constant current density and 70°C for 400 h. As a result, PEMFC performance was found to be superlative for the graphene-supported Pt catalyst compared with the Pt/C commercial catalyst. The results indicate the graphene-supported Pt catalyst could be utilized as the electrocatalyst for PEMFC applications.

  6. New Cathode Materials for Intermediate Temperature Solid Oxide Fuel Cells

    SciTech Connect

    Allan J. Jacobson

    2005-11-17

    Operation of SOFCs at intermediate temperatures (500-800 C) requires new combinations of electrolyte and electrode materials that will provide both rapid ion transport across the electrolyte and electrode--electrolyte interfaces and efficient electrocatalysis of the oxygen reduction and fuel oxidation reactions. This project concentrates on materials and issues associated with cathode performance that are known to become limiting factors as the operating temperature is reduced. The specific objectives of the proposed research are to develop cathode materials that meet the electrode performance targets of 1.0 W/cm{sup 2} at 0.7 V in combination with YSZ at 700 C and with GDC, LSGM or bismuth oxide based electrolytes at 600 C. The performance targets imply an area specific resistance of {approx}0.5 {Omega}cm{sup 2} for the total cell. The research strategy is to investigate both established classes of materials and new candidates as cathodes, to determine fundamental performance parameters such as bulk diffusion, surface reactivity and interfacial transfer, and to couple these parameters to performance in single cell tests. In this report, the oxygen exchange kinetics of a P2 composition are described in detail. The oxygen exchange kinetics of the oxygen deficient double perovskite LnBaCo{sub 2}O{sub 5.5+{delta}} (Ln=Pr and Nd) have been determined by electrical conductivity relaxation. The high electronic conductivity and rapid diffusion and surface exchange kinetics of PBCO suggest its application as cathode material in intermediate temperature solid oxide fuel cells.

  7. Carbon Nanohorn-Derived Graphene Nanotubes as a Platinum-Free Fuel Cell Cathode.

    PubMed

    Unni, Sreekuttan M; Illathvalappil, Rajith; Bhange, Siddheshwar N; Puthenpediakkal, Hasna; Kurungot, Sreekumar

    2015-11-01

    Current low-temperature fuel cell research mainly focuses on the development of efficient nonprecious electrocatalysts for the reduction of dioxygen molecule due to the reasons like exorbitant cost and scarcity of the current state-of-the-art Pt-based catalysts. As a potential alternative to such costly electrocatalysts, we report here the preparation of an efficient graphene nanotube based oxygen reduction electrocatalyst which has been derived from single walled nanohorns, comprising a thin layer of graphene nanotubes and encapsulated iron oxide nanoparticles (FeGNT). FeGNT shows a surface area of 750 m(2)/g, which is the highest ever reported among the metal encapsulated nanotubes. Moreover, the graphene protected iron oxide nanoparticles assist the system to attain efficient distribution of Fe-Nx and quaternary nitrogen based active reaction centers, which provides better activity and stability toward the oxygen reduction reaction (ORR) in acidic as well as alkaline conditions. Single cell performance of a proton exchange membrane fuel cell by using FeGNT as the cathode catalyst delivered a maximum power density of 200 mW cm(-2) with Nafion as the proton exchange membrane at 60 °C. The facile synthesis strategy with iron oxide encapsulated graphitic carbon morphology opens up a new horizon of hope toward developing Pt-free fuel cells and metal-air batteries along with its applicability in other energy conversion and storage devices. PMID:26458554

  8. Measurement of effective gas diffusion coefficients of catalyst layers of PEM fuel cells with a Loschmidt diffusion cell

    NASA Astrophysics Data System (ADS)

    Shen, Jun; Zhou, Jianqin; Astrath, Nelson G. C.; Navessin, Titichai; Liu, Zhong-Sheng (Simon); Lei, Chao; Rohling, Jurandir H.; Bessarabov, Dmitri; Knights, Shanna; Ye, Siyu

    In this work, using an in-house made Loschmidt diffusion cell, we measure the effective coefficient of dry gas (O 2-N 2) diffusion in cathode catalyst layers of PEM fuel cells at 25 °C and 1 atmosphere. The thicknesses of the catalyst layers under investigation are from 6 to 29 μm. Each catalyst layer is deposited on an Al 2O 3 membrane substrate by an automated spray coater. Diffusion signal processing procedure is developed to deduce the effective diffusion coefficient, which is found to be (1.47 ± 0.05) × 10 -7 m 2 s -1 for the catalyst layers. Porosity and pore size distribution of the catalyst layers are also measured using Hg porosimetry. The diffusion resistance of the interface between the catalyst layer and the substrate is found to be negligible. The experimental results show that the O 2-N 2 diffusion in the catalyst layers is dominated by the Knudsen effect.

  9. Highly Dispersed Metal Catalyst for Fuel Cell Electrodes

    SciTech Connect

    2009-03-01

    This factsheet describes a study that will bring industrial catalyst experience to fuel cell research. Specifically, industrial catalysts, such as those used in platforming, utilize precious metal platinum as an active component in a finely dispersed form.

  10. Cathode materials for the molten carbonate fuel cell

    SciTech Connect

    Kucera, G.H.; Brown, A.P.; Roche, M.F.; Indacochea, E.J.; Krumpelt, M.; Myles, K.M.

    1993-08-01

    Both LiFeO{sub 2} and Li{sub 2},MnO{sub 3} were stable in the cathode environment, had low solubility, and were nonprecipitating in the anode environment. Dopants were employed to enhance the electronic conductivity of both materials. Cobalt-doped LiFeO{sub 2} was a factor of 30 more conductive than the undoped LiFeO{sub 2}; Nb-doped Li{sub 2}MnO{sub 3} was a factor of 60 more conductive than its undoped form. However, only the Co-doped LiFeO{sub 2} Li{sub 2} exhibited the desired p-type conduction. Half- and full-cell tests with Co-doped LiFeO{sub 2} as the cathode material showed that its performance strongly depended on the oxygen partial pressure. Under simulated high-pressure conditions, where the O{sub 2} partial pressure was 70 kPa, the performance was good. LiCoO{sub 2} had low solubility and was a good electronic conductor undoped. In addition, it exhibited p-type conduction, and, when used as a cathode material, gave good cell performance. It precipitated as cobalt metal under reducing conditions in anode. However, neither rate of deposition nor conditions influencing deposition and location are known.

  11. A reduced temperature solid oxide fuel cell with three-dimensionally ordered macroporous cathode

    SciTech Connect

    Liang, B.; Suzuki, T.; Hamamoto, K.; Yamaguchi, T.; Sumi, H.; Fujishiro, Y.; Ingram, B. J.; Carter, J. D.

    2012-01-01

    Three-dimensionally ordered macroporous cathode was fabricated for a zirconia based micro-tubular solid oxide fuel cells (SOFCs). Three different cathodes (cathode A, no pore former; cathode B, with pore former (1.5 {micro}m in diameter); cathode C, with pore former (0.8 {micro}m in diameter)) were compared to investigate how the microstructure of it affected the cell performance at various operating temperatures. Micro-sized pores were well distributed within cathode B and C. The total porosity of cathode A is 35%, while it respectively reached 42 and 50% for cathodes B and C. At the same time, the specific surface area of them was 28.8 and 52.0% larger than that of the cathode A. As a result, the peak power density of the zirconia based cell, with cathode C, was 0.25 and 0.56 W cm{sup -2} at 550 and 600 C, while the respective value was just 0.11 and 0.30 W cm{sup -2} for the cell with cathode A. Thus, optimizing microstructure of cathode should be one of the best approaches for lowering the operating temperature for SOFCs.

  12. Moderate temperature sodium cells. I - Transition metal disulfide cathodes

    NASA Technical Reports Server (NTRS)

    Abraham, K. M.; Pitts, L.; Schiff, R.

    1980-01-01

    TiS2, VS2, and Nb(1.1)S2 transition metal disulfides were evaluated as cathode materials for a moderate temperature rechargeable Na cell operating at 130 C. The 1st discharge of TiS2 results in a capacity of 0.85 eq/mole; approximately half of the Na in the 1st phase spanning the Na range from zero to 0.30 and almost all the Na in the 2nd phase spanning the 0.37 to 0.80 range are rechargeable. VS2 intercalates up to one mole of Na/mole of VS2 in the 1st discharge; the resulting Na(x)VS2 ternary consists of 3 phases in the 3 ranges of Na from zero to 1. Niobium disulfide undergoes a phase change in the 1st discharge; the average rechargeable capacity in extended cycling of this cathode is 0.50 eq/mole.

  13. Contribution of properties of composite cathode and cathode/electrolyte interface to cell performance in a planar solid oxide fuel cell stack

    NASA Astrophysics Data System (ADS)

    Wu, Wei; Guan, Wanbing; Wang, Weiguo

    2015-04-01

    Solid oxide fuel cells (SOFCs) with distinct cathode materials usually differ in output performance. In this study, 2 μm-thick Pt voltage probes are embedded into the cathode/electrolyte interface. The effects of the electrical properties and cathode/electrolyte interfaces of LSCF-GDC and LSM-YSZ composite cathodes on cell performance are investigated in situ for anode-supported planar SOFCs. Results show that the voltage and maximum output power density measured by the probes on both sides of the LSCF-GDC and LSM-YSZ composite cathodes are 7% and 4%, respectively, of those of the corresponding cell during instantaneous current-voltage testing. The enhanced LSCF cell performance is mainly attributed to the rough GDC/LSCF-GDC interface that is responsible for the three-dimensional contact between the GDC layer and LSCF-GDC cathode particles and increases the triple-phase boundary (TPB) length. The LSM-YSZ cathode performance degradation is attributed to the variation in polarization resistance caused by cathode particle growth. However, the primary factor for the degradation of LSCF-GDC cathode performance is structural instability, such as inner cracks.

  14. Highly Active and Redox-Stable Ce-Doped LaSrCrFeO-Based Cathode Catalyst for CO2 SOECs.

    PubMed

    Zhang, Ya-Qian; Li, Jian-Hui; Sun, Yi-Fei; Hua, Bin; Luo, Jing-Li

    2016-03-01

    Lanthanum chromate-based perovskite oxides have attracted great attention as the cathode materials in the high-temperature CO2 electrolysis because of its good redox stability. However, the unsatisfied electrochemical catalytic activity and insufficient adsorption of CO2 at operating temperature still hindered the further improvement of electrochemical performance and the Faraday efficiency of the electrolysis cell. In this work, the catalytic and redox active Ce was doped into A site of La0.7Sr0.3Cr0.5Fe0.5O3-δ (LSCrF) to promote the catalytic performance, and to introduce oxygen vacancies in the lattice in situ after reduction under the operational condition. The increased amount of oxygen vacancies not only facilitates the mobility of oxygen ions, but also provides favorable accommodation for chemical adsorption of CO2. The CO2 electrolysis tests demonstrated the superior electrochemical performances, higher Faraday efficiencies of the Ce-doped LSCrF cathode catalyst in comparison with that without Ce doping, indicating the perspective application of this functional material. PMID:26901862

  15. Poly(vinylidene fluoride-co-hexafluoropropylene) phase inversion coating as a diffusion layer to enhance the cathode performance in microbial fuel cells

    NASA Astrophysics Data System (ADS)

    Yang, Wulin; Zhang, Fang; He, Weihua; Liu, Jia; Hickner, Michael A.; Logan, Bruce E.

    2014-12-01

    A low cost poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) phase inversion coating was developed as a cathode diffusion layer to enhance the performance of microbial fuel cells (MFCs). A maximum power density of 1430 ± 90 mW m-2 was achieved at a PVDF-HFP loading of 4.4 mg cm-2 (4:1 polymer:carbon black), with activated carbon as the oxygen reduction cathode catalyst. This power density was 31% higher than that obtained with a more conventional platinum (Pt) catalyst on carbon cloth (Pt/C) cathode with a poly(tetrafluoroethylene) (PTFE) diffusion layer (1090 ± 30 mW m-2). The improved performance was due in part to a larger oxygen mass transfer coefficient of 3 × 10-3 cm s-1 for the PVDF-HFP coated cathode, compared to 1.7 × 10-3 cm s-1 for the carbon cloth/PTFE-based cathode. The diffusion layer was resistant to electrolyte leakage up to water column heights of 41 ± 0.5 cm (4.4 mg cm-2 loading of 4:1 polymer:carbon black) to 70 ± 5 cm (8.8 mg cm-2 loading of 4:1 polymer:carbon black). This new type of PVDF-HFP/carbon black diffusion layer could reduce the cost of manufacturing cathodes for MFCs.

  16. The performance and mechanism of modified activated carbon air cathode by non-stoichiometric nano Fe3O4 in the microbial fuel cell.

    PubMed

    Fu, Zhou; Yan, Litao; Li, Kexun; Ge, Baochao; Pu, Liangtao; Zhang, Xi

    2015-12-15

    Cathodic catalyst is one of the key materials in microbial fuel cell (MFC). The addition of non-stoichiometric nano Fe3O4 in activated carbon (NSFe3O4/AC) air cathode was beneficial to boosting the charge transfer of the cathode accompanying with the enhancement of power performance in MFC. The air cathode modified by NSFe3O4 (5%, Wt%) increased the maximum power density by 83.3% from 780 mW/m(2) to 1430 mW/m(2) compared with bare air cathode. The modified cathodes showed enhanced electrochemical properties and appeared the maximum exchange current density of 18.71×10(-4) A/cm(2) for oxygen reduction reaction. The mechanism of oxygen reduction for the NSFe3O4/AC catalyst was a 4-electron pathway. The oxygen vacancy of the NSFe3O4 played a crucial role in electrochemical catalytic activity. The great catalytic performance made NSFe3O4 have a promising outlook applied in MFC. PMID:26264265

  17. Efficient Oxygen Evolution Reaction Catalysts for Cell Reversal and Start/Stop Tolerance in Fuel Cells

    SciTech Connect

    Atanasoski, Radoslav; Atanasoska, Liliana; Cullen, David A

    2013-01-01

    Minute amounts of ruthenium and iridium on platinum nanostructured thin films have been evaluated in an effort to reduce carbon corrosion and Pt dissolution during transient conditions in proton exchange membrane fuel cells. Electrochemical tests showed the catalysts had a remarkable oxygen evolution reaction (OER) activity, even greater than that of bulk, metallic thin films. Stability tests within a fuel cell environment showed that rapid Ru dissolution could be managed with the addition of Ir. Membrane electrode assemblies containing a Ru to Ir atomic ratio of 1:9 were evaluated under startup/shutdown and cell reversal conditions for OER catalyst loadings ranging from 1 to 10 g/cm2. These tests affirmed that electrode potentials can be controlled through the addition of OER catalysts without impacting the oxygen reduction reaction on the cathode or the hydrogen oxidation reaction on the anode. The morphology and chemical structure of the thin OER layers were characterized by scanning transmission electron microscopy and X-ray photoelectron spectroscopy in an effort to establish a correlation between interfacial properties and electrochemical behavior.

  18. Temporal variations of cathode performance in air-cathode single-chamber microbial fuel cells with different separators

    NASA Astrophysics Data System (ADS)

    Ma, Jinxing; Wang, Zhiwei; Suor, Denis; Liu, Shumeng; Li, Jiaqi; Wu, Zhichao

    2014-12-01

    An ideal separator is essential for efficient power production from air-cathode single-chamber microbial fuel cells (MFCs). In this study, we use different kinds of membranes as separators, including Nafion 117 proton exchange membrane, polyethersulfone and poly(vinylidene fluoride) microfiltration membranes. Temporal variations of cathode performance are monitored during the experiment. Results show that MFCs with microfiltration membranes present higher power output but deterioration is still observed after about 600-h operation. With the utilization of appropriate separators (e.g., polyethersulfone membrane), biofouling, cation fouling and chemical scale fouling of the cathodes are alleviated while reaction fouling seems inevitable. Moreover, it is found that Coulombic efficiency (CE) and energy efficiency (EE) are also related to the cathode performance. Despite relatively high oxygen diffusivity (1.49 × 10-5 cm2 s-1), CE and EE of the MFC with 0.1 μm pore-size polyethersulfone membrane can reach 92.8% and 13.7%, respectively, when its average power density registers 403.5 mW m-2. This phenomenon might be attributed to the finding that the overall substrate consumption rate due to oxygen reduction and respiration is almost constant in the air-cathode MFCs. Oxygen leakage into the electrolyte can be inhibited due to the efficient oxygen reduction reaction on the surface of the cathode.

  19. Sulfur-doped graphene as an efficient metal-free cathode catalyst for oxygen reduction.

    PubMed

    Yang, Zhi; Yao, Zhen; Li, Guifa; Fang, Guoyong; Nie, Huagui; Liu, Zheng; Zhou, Xuemei; Chen, Xi'an; Huang, Shaoming

    2012-01-24

    Tailoring the electronic arrangement of graphene by doping is a practical strategy for producing significantly improved materials for the oxygen-reduction reaction (ORR) in fuel cells (FCs). Recent studies have proven that the carbon materials doped with the elements, which have the larger (N) or smaller (P, B) electronegative atoms than carbon such as N-doped carbon nanotubes (CNTs), P-doped graphite layers and B-doped CNTs, have also shown pronounced catalytic activity. Herein, we find that the graphenes doped with the elements, which have the similar electronegativity with carbon such as sulfur and selenium, can also exhibit better catalytic activity than the commercial Pt/C in alkaline media, indicating that these doped graphenes hold great potential for a substitute for Pt-based catalysts in FCs. The experimental results are believed to be significant because they not only give further insight into the ORR mechanism of these metal-free doped carbon materials, but also open a way to fabricate other new low-cost NPMCs with high electrocatalytic activity by a simple, economical, and scalable approach for real FC applications. PMID:22201338

  20. High pressure pyrolyzed non-precious metal oxygen reduction catalysts for alkaline polymer electrolyte membrane fuel cells.

    PubMed

    Sanetuntikul, Jakkid; Shanmugam, Sangaraju

    2015-05-01

    Non-precious metal catalysts, such as metal-coordinated to nitrogen doped-carbon, have shown reasonable oxygen reduction reaction (ORR) performances in alkaline fuel cells. In this report, we present the development of a highly active, stable and low-cost non-precious metal ORR catalyst by direct synthesis under autogenic-pressure conditions. Transmission electron microscopy studies show highly porous Fe-N-C and Co-N-C structures, which were further confirmed by Brunauer-Emmett-Teller surface area measurements. The surface areas of the Fe-N-C and Co-N-C catalysts were found to be 377.5 and 369.3 m(2) g(-1), respectively. XPS results show the possible existence of N-C and M-Nx structures, which are generally proposed to be the active sites in non-precious metal catalysts. The Fe-N-C electrocatalyst exhibits an ORR half-wave potential 20 mV higher than the reference Pt/C catalyst. The cycling durability test for Fe-N-C over 5000 cycles shows that the half-wave potential lost only 4 mV, whereas the half-wave potential of the Pt/C catalyst lost about 50 mV. The Fe-N-C catalyst exhibited an improved activity and stability compared to the reference Pt/C catalyst and it possesses a direct 4-electron transfer pathway for the ORR process. Further, the Fe-N-C catalyst produces extremely low HO2(-) content, as confirmed by the rotating ring-disk electrode measurements. In the alkaline fuel single cell tests, maximum power densities of 75 and 80 mW cm(-2) were observed for the Fe-N-C and Pt/C cathodes, respectively. Durability studies (100 h) showed that decay of the fuel cell current was more prominent for the Pt/C cathode catalyst compared to the Fe-N-C cathode catalyst. Therefore, the Fe-N-C catalyst appears to be a promising new class of non-precious metal catalysts prepared by an autogenic synthetic method. PMID:25833146

  1. Optimization of ink composition based on a non-platinum cathode for single membrane electrode assembly proton exchange membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Artyushkova, K.; Habel-Rodriguez, D.; Olson, T. S.; Atanassov, P.

    2013-03-01

    Non-Pt based oxygen reduction catalyst H2-air fuel cell performance is reported for various electrode compositions. Ink formulations for pyrolyzed Co porphyrin based cathode electrocatalysts were evaluated in a membrane electrode assembly (MEA) configuration and X-ray photoelectron spectroscopy was performed on the MEA catalyst layers. The effect of cooling time trajectories of the catalysts after pyrolysis as well as Nafion content in the ink formulation were studied. By building statistical structure-to-property relationships between XPS and MEA performance using multivariate analysis we have determined that the higher stability of fast-cooled containing inks is mainly associated with better preserved graphic carbon from the carbon black and C-F moieties of the Nafion, while better MEA performance is a result of the presence of these moieties as well as pyridinic nitrogen and nitrogen associated with metal in the pyropolymer. Optimal Nafion content is determined at 1:1 catalyst:Nafion weight ratio, while higher Nafion concentrations causes oxidation of the Nafion backbone itself as well as leaching of the CoxOy particles from the catalyst and formation of oxidized species of Co, O, C and F. Further, we report 1500 h of continuous fuel cell operation for two different non-platinum cathode catalysts in the optimized MEA.

  2. Performance Enhancement of Small Molecular Solar Cells by Bilayer Cathode Buffer.

    PubMed

    Sun, Qinjun; Zhao, Huanbin; Zhou, Miao; Gao, Liyan; Hao, Yuying

    2016-04-01

    An effective composite bilayer cathode buffer structure is proposed for use in small molecular solar cells. CsF was doped in Alq3 to form the first cathode buffer, leading to small serial resistances. BCP was used as the second cathode buffer to block the holes to the electrode. The optimized bilayer cathode buffer significantly increased the short circuit and fill factor of devices. By integrating this bilayer cathode buffer, the CuPc/C60 small molecular heterojunction cell exhibited a power conversion efficiency of up to 0.8%, which was an improvement of 56% compared to a device with only the Alq3 cathode buffer. Meanwhile, the bilayer cathode buffer still has a good protective effect on the performance of the device. PMID:27451719

  3. Anion-Intercalating Cathodes for High-Energy-Density Cells

    NASA Technical Reports Server (NTRS)

    West, William

    2006-01-01

    A report discusses physicochemical issues affecting a fluoride-intercalating cathode that operates in conjunction with a lithium ion-intercalating anode in a rechargeable electrochemical cell described in a cited prior report. The instant report also discusses corresponding innovations made in solvent and electrolyte compositions since the prior report. The advantages of this cell, relative to other lithium-ion-based cells, are said to be greater potential (5 V vs. 4 V), and greater theoretical cathode specific capacity (0.9 to 2.2 A-h/g vs. about 0.18 A-h/g). The discussion addresses a need for the solvent to be unreactive toward the lithium anode and to resist anodic oxidation at potentials greater than about 4.5 V vs. lithium; the pertinent innovation is the selection of propylene carbonate (PC) as a solvent having significantly more stability, relative to other solvents that have been tried. The discussion also addresses the need for an electrolyte additive, denoted an anion receptor, to complex the fluoride ion; the pertinent innovation is the selection of tris(hexafluoroisopropyl) borate as a superior alternative to the prior anion receptor, which was tris(pentafluorophenyl) borate.

  4. Activated carbon nanofibers (ACNF) as cathode for single chamber microbial fuel cells (SCMFCs)

    NASA Astrophysics Data System (ADS)

    Santoro, Carlo; Stadlhofer, Astrid; Hacker, Viktor; Squadrito, Gaetano; Schröder, Uwe; Li, Baikun

    2013-12-01

    The suitability of carbon nanofibers (CNF) based cathodes as alternative to the platinum (Pt)-based cathode in single chamber microbial fuel cells (SCMFCs) were extensively studied over 3-month operational period. MFCs were fed with two solutions: synthetic wastewater (phosphate buffer (PBS) plus sodium acetate) and real wastewater (mixed liquor suspendedsolid (MLSS) solution). CNFs were chemically activated using HNO3 and then hot pressed on a carbon cloth support to increase surface area. The cathode polarization showed a better behavior of the clean Pt-based cathode in abiotic conditions. The activation of the nanofibers (ACNFs) gave an advantage to the cathode performances compared to the raw CNFs. The SCMFCs fed with PBS showed four times higher power generation compared to MLSS solution. All the cathodes showed a decrease in performances over time, and the advantage of the Pt over CNF/ACNF disappeared. CNF/ACNF cathodes showed more stability in performances in long time operations. Biofilm formation, salt precipitations on the cathode, and the presence of hydrogen sulfide decreased the activity of Pt cathodes. A degradation and Pt detachment were noticed on Pt cathodes over time. In contrast, CNF/ACNF cathodes exhibited less deterioration throughout the operational period, which demonstrated a great potential as cost-effective cathodes for long-term operation.

  5. Advanced electro-Fenton degradation of biologically-treated coking wastewater using anthraquinone cathode and Fe-Y catalyst.

    PubMed

    Li, Haitao; Li, Yuping; Cao, Hongbin; Li, Xingang; Zhang, Yi

    2011-01-01

    The electrocatalytic activity of bare and 2-ethyl anthraquinone-modified graphite felt (2-EAQ/GF) toward oxygen reduction was investigated using a cyclic voltammetry technique in a neutral solution. The prepared cathodes were tested for electrogeneration of H2O2 and electro-Fenton oxidation (EFO) treatment of neutral coking wastewater (CW) after biological process, using a graphite anode and Fezeolite Y catalyst. The results showed that (i) H2O2 yield and current efficiency greatly depended on cathodic potential and materials; (ii) hydroxyl radicals, generated from Fe-zeolite Y-catalyzed H2O2 decomposition, played a great role in EFO treatment, while anodic direct and indirect oxidation was insignificant; (iii) chemical oxygen demand, total organic carbon (TOC) and acute toxicity of wastewater decreased by 40-50, 30-40 and 50-60%, respectively, and biodegradability increased after 1 h of EFO treatment. Due to the free-pH adjustment, EFO presents a potential engineering application for advanced treatment of CW. PMID:22053459

  6. Effects of carbon supports on Pt distribution, ionomer coverage and cathode performance for polymer electrolyte fuel cells

    NASA Astrophysics Data System (ADS)

    Park, Young-Chul; Tokiwa, Haruki; Kakinuma, Katsuyoshi; Watanabe, Masahiro; Uchida, Makoto

    2016-05-01

    We investigate the effects of the carbon supports on the Pt distribution, ionomer coverage and cathode performance of carbon-supported Pt catalysts, by using STEM observation, N2 adsorption analysis and electrochemical characterization. According to the STEM observation, the effective Pt surface area (S(e)Pt), which is determined by the location and size of the Pt particles on the supports, increases in the following order: c-Pt/CB < c-Pt/GCB < n-Pt/AB800 < n-Pt/AB250. The N2 adsorption analyses show that the Pt particles observed in the interior of the CB and AB800-supported Pt catalysts during the STEM observation could be ascribed to the hollow structures inside the carbon supports, which decrease their effective Pt surface areas. The S(e)Pt values are in good agreement with the cell performance in the high current density region. In spite of the highest Pt utilization (UPt) value (>90%) and uniform ionomer coverage, the c-Pt/CB catalyst shows the lowest cell performance due to the lower S(e)Pt value. On the other hand, the n-Pt/AB250 catalyst, for which all of the Pt particles exist only on the exterior surface, is found to be the most attractive in order to generate the large current densities required by actual fuel cell operation.

  7. Effects of carbon supports on Pt distribution, ionomer coverage and cathode performance for polymer electrolyte fuel cells

    NASA Astrophysics Data System (ADS)

    Park, Young-Chul; Tokiwa, Haruki; Kakinuma, Katsuyoshi; Watanabe, Masahiro; Uchida, Makoto

    2016-05-01

    We investigate the effects of the carbon supports on the Pt distribution, ionomer coverage and cathode performance of carbon-supported Pt catalysts, by using STEM observation, N2 adsorption analysis and electrochemical characterization. According to the STEM observation, the effective Pt surface area (S(e)Pt), which is determined by the location and size of the Pt particles on the supports, increases in the following order: c-Pt/CB < c-Pt/GCB < n-Pt/AB800 < n-Pt/AB250. The N2 adsorption analyses show that the Pt particles observed in the interior of the CB and AB800-supported Pt catalysts during the STEM observation could be ascribed to the hollow structures inside the carbon supports, which decrease their effective Pt surface areas. The S(e)Pt values are in good agreement with the cell performance in the high current density region. In spite of the highest Pt utilization (UPt) value (>90%) and uniform ionomer coverage, the c-Pt/CB catalyst shows the lowest cell performance due to the lower S(e)Pt value. On the other hand, the n-Pt/AB250 catalyst, for which all of the Pt particles exist only on the exterior surface, is found to be the most attractive in order to generate the large current densities required by actual fuel cell operation.

  8. Enhanced hydrogen production in microbial electrolysis cell with 3D self-assembly nickel foam-graphene cathode.

    PubMed

    Cai, Weiwei; Liu, Wenzong; Han, Jinglong; Wang, Aijie

    2016-06-15

    In comparison to precious metal catalyst especially Platinum (Pt), nickel foam (NF) owned cheap cost and unique three-dimensional (3D) structure, however, it was scarcely applied as cathode material in microbial electrolysis cell (MEC) as the intrinsic laggard electrochemical activity for hydrogen recovery. In this study, a self-assembly 3D nickel foam-graphene (NF-G) cathode was fabricated by facile hydrothermal approach for hydrogen evolution in MECs. Electrochemical analysis (linear scan voltammetry and electrochemical impedance spectroscopy) revealed the improved electrochemical activity and effective mass diffusion after coating with graphene. NF-G as cathode in MEC showed a significant enhancement in hydrogen production rate compared with nickel foam at a variety of biases. Noticeably, NF-G showed a comparable averaged hydrogen production rate (1.31 ± 0.07 mL H2 mL(-1) reactor d(-1)) to Platinum/carbon (Pt/C) (1.32 ± 0.07 mL H2 mL(-1) reactor d(-1)) at 0.8 V. Profitable energy recovery could be achieved by NF-G cathode at higher applied voltage, which performed the best hydrogen yield of 3.27 ± 0.16 mol H2 mol(-1) acetate at 0.8 V and highest energy efficiency of 185.92 ± 6.48% at 0.6 V. PMID:26807526

  9. Effect of ionic conductivity of zirconia electrolytes on the polarization behavior of various cathodes in solid oxide fuel cells

    SciTech Connect

    Uchida, Hiroyuki; Yoshida, Manabu; Watanabe, Masahiro

    1999-01-01

    The polarization behaviors of porous platinum and La(Sr)MnO{sub 3} (LSM) cathodes coupled with zirconia electrolytes with various ionic conductivities ({sigma}{sub ion}) were investigated. The exchange current density, j{sub 0}, on Pt cathode was not influenced by the {sigma}{sub ion} at 900 and 1,000 C, whereas j{sub 0} increased proportionally to {sigma}{sub ion} at a lower temperature of 800 C. However, the j{sub 0} on LSM cathodes increased in proportion to the {sigma}{sub ion} in the temperature region between 800 and 1,000 C. The dispersion of nanometer-sized Pt catalysts on LSM particles greatly enhanced the performance, the magnitude of which depended on the temperature, the {sigma}{sub ion}, and the microstructure of LSM. The observations are well explained kinetically, i.e., the cathode performance is controlled by the transport rate of O{sup 2{minus}} at the interface when the surface reaction rate is sufficiently high. Consequently, the use of high-performance electrodes in combination with the solid electrolyte having high {sigma}{sub ion} is very important for achieving the high performance of solid oxide fuel cells.

  10. Accelerated OH(-) transport in activated carbon air cathode by modification of quaternary ammonium for microbial fuel cells.

    PubMed

    Wang, Xin; Feng, Cuijuan; Ding, Ning; Zhang, Qingrui; Li, Nan; Li, Xiaojing; Zhang, Yueyong; Zhou, Qixing

    2014-04-01

    Activated carbon (AC) is a promising catalyst for the air cathode of microbial fuel cells (MFCs) because of its high performance and low cost. To increase the performance of AC air cathodes, the acceleration of OH(-) transport is one of the most important methods, but it has not been widely investigated. Here we added quaternary ammonium to ACs by in situ anchoring of a quaternary ammonium/epoxide-reacting compound (QAE) or ex situ mixing with anion exchange resins in order to modify ACs from not only the external surface but also inside the pores. In 50 mM phosphate buffer solution (PBS), the in situ anchoring of QAE was a more effective way to increase the power. The highest power density of 2781 ± 36 mW/m(2), which is 10% higher than that of the control, was obtained using QAE-anchored AC cathodes. When the medium was switched to an unbuffered NaCl solution, the increase in maximum power density (885 ± 25 mW/m(2)) was in accordance with the anion exchange capacity (0.219 mmol/g). The highest power density of the anion exchange resin-mixed air cathode was 51% higher than that of the control, indicating that anion exchange is urgently needed in real wastewaters. Excess anchoring of QAE blocked both the mesopores and micropores, causing the power output to be inhibited. PMID:24597673

  11. Ultrasonic synthesis and evaluation of non-platinum catalysts for alkaline direct methanol fuel cells

    NASA Astrophysics Data System (ADS)

    Bunazawa, Hideaki; Yamazaki, Yohtaro

    Ultrasonic synthesis was investigated as a synthesis method of non-platinum catalysts for alkaline direct methanol fuel cells (alkaline DMFCs) such as 20% mass Pd/C, Au/C, and PdAu/C. Among four kinds of solvents, ethylene glycol was demonstrated to be the optimum solvent for the synthesis of those catalysts. When ethylene glycol was used, the synthesized metal nanoparticles were highly dispersed on carbon particles. The synthesized Pd/C and PdAu/C showed the high oxygen reduction reaction (ORR) activity in alkaline condition (0.5 M NaOH aqueous solution), which was comparable to conventional Pt/C. Moreover, they showed lower methanol oxidation reaction (MOR) activity. Membrane electrode assemblies (MEAs) containing the synthesized Pd/C cathode catalysts and alkaline ion exchange membranes were fabricated and evaluated by single cell tests. They showed high performance that was comparable to MEAs with Pt/C cathode. In addition, it was found that the synthesized Pd/C was relatively tolerant to methanol crossover.

  12. EFFECT OF PRETREATMENT ON PT-CO/C CATHODE CATALYSTS FOR THE OXYGEN-REDUCTION REACTION

    SciTech Connect

    Fox, E.

    2009-05-13

    In order to reduce the precious metal loading without sacrificing activity and stability, a new method for the preparation of bimetallic catalysts is proposed. Currently, Pt-alloy particles, with 2 to 3 nm in diameter, are loaded on high surface area carbon supports. Of the Pt loaded, only the surface atoms interact with the reactants. In order to increase the Pt utilization per metal particle the new process for catalyst preparation will incorporate a non-noble transition metal core coated with a skin layer of Pt deposited on high surface area carbon. The effect of reducing agent strength during synthesis was also explored. It was determined that the Co addition has a higher impact on catalyst when used with NaBH4 as reducing agent as compared to NaCOOH.

  13. Bifunctional quaternary ammonium compounds to inhibit biofilm growth and enhance performance for activated carbon air-cathode in microbial fuel cells

    NASA Astrophysics Data System (ADS)

    Li, Nan; Liu, Yinan; An, Jingkun; Feng, Cuijuan; Wang, Xin

    2014-12-01

    The slow diffusion of hydroxyl out of the catalyst layer as well as the biofouling on the surface of cathode are two problems affecting power for membrane-less air-cathode microbial fuel cells (MFCs). In order to solve both of them simultaneously, here we simply modify activated carbon air-cathode using a bifunctional quaternary ammonium compound (QAC) by forced evaporation. The maximum power density reaches 1041 ± 12 mW m-2 in an unbuffered medium (0.5 g L-1 NaCl), which is 17% higher than the control, probably due to the accelerated anion transport in the catalyst layer. After 2 months, the protein content reduced by a factor of 26 and the power density increases by 33%, indicating that the QAC modification can effectively inhibit the growth of cathodic biofilm and improve the stability of performance. The addition of NaOH and QAC epoxy have a negative effect on power production due to the clogging of pores in catalyst layer.

  14. Discharge characteristics of lithium/molten nitrate thermal battery cells using silver salts as solid cathode materials

    NASA Astrophysics Data System (ADS)

    McManis, G. E.; Miles, M. H.; Fletcher, A. N.

    1985-12-01

    Thermal battery cells using molten nitrate electrolytes and liquid lithium anodes have been evaluated using several silver salts with low solubility in molten nitrates as solid cathode materials. These cathode materials do not readily diffuse into the anolyte and, thus, do not have parasitic reactions with the lithium anode. Furthermore, the solid cathode materials have voltammetric characteristics as favorable as many soluble silver salt cathodes. This paper presents the effects of temperature, current density, and cathode material on cell discharge characteristics.

  15. Metal-free selenium doped carbon nanotube/graphene networks as a synergistically improved cathode catalyst for oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Jin, Zhiping; Nie, Huagui; Yang, Zhi; Zhang, Jing; Liu, Zheng; Xu, Xiangju; Huang, Shaoming

    2012-09-01

    The ongoing search for new non-precious-metal catalysts (NPMCs) with excellent electrocatalytic performance to replace Pt-based catalysts has been viewed as an important strategy to promote the development of fuel cells. Recent studies have proven that carbon materials doped with atoms which have a relatively small atomic size (e.g. N, B, P or S), have also shown pronounced catalytic activity. Herein, we demonstrate the successful fabrication of CNT/graphene doped with Se atoms, which has a relatively large atomic size, by a simple, economical, and scalable approach. The electrocatalytic performance of the resulting Se-doped CNT-graphene catalyst exhibits excellent catalytic activity, long-term stability, and a high methanol tolerance compared to commercial Pt/C catalysts. Our results confirmed that combining CNTs with graphene is an effective strategy to synergistically improve ORR activity. More importantly, it is also suggested that the development of graphite materials doped with Se or other heteroatoms of large size will open up a new route to obtain ideal NPMCs with realistic value for fuel cell applications.The ongoing search for new non-precious-metal catalysts (NPMCs) with excellent electrocatalytic performance to replace Pt-based catalysts has been viewed as an important strategy to promote the development of fuel cells. Recent studies have proven that carbon materials doped with atoms which have a relatively small atomic size (e.g. N, B, P or S), have also shown pronounced catalytic activity. Herein, we demonstrate the successful fabrication of CNT/graphene doped with Se atoms, which has a relatively large atomic size, by a simple, economical, and scalable approach. The electrocatalytic performance of the resulting Se-doped CNT-graphene catalyst exhibits excellent catalytic activity, long-term stability, and a high methanol tolerance compared to commercial Pt/C catalysts. Our results confirmed that combining CNTs with graphene is an effective strategy to

  16. Modeling Low-Platinum-Loading Effects in Fuel-Cell Catalyst Layers

    SciTech Connect

    Yoon, Wonseok; Weber, Adam Z.

    2011-01-20

    The cathode catalyst layer within a proton-exchange-membrane fuel cell is the most complex and critical, yet least understood, layer within the cell. The exact method and equations for modeling this layer are still being revised and will be discussed in this paper, including a 0.8 reaction order, existence of Pt oxides, possible non-isopotential agglomerates, and the impact of a film resistance towards oxygen transport. While the former assumptions are relatively straightforward to understand and implement, the latter film resistance is shown to be critically important in explaining increased mass-transport limitations with low Pt-loading catalyst layers. Model results demonstrate agreement with experimental data that the increased oxygen flux and/or diffusion pathway through the film can substantially decrease performance. Also, some scale-up concepts from the agglomerate scale to the more macroscopic porous-electrode scale are discussed and the resulting optimization scenarios investigated.

  17. La0.6Sr0.4Co0.2Fe0.8O3 cathodes incorporated with Sm0.2Ce0.8O2 by three different methods for solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Shen, Fengyu; Lu, Kathy

    2015-11-01

    The incorporation of Sm0.2Ce0.8O2 (SDC) into La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) is carried out by three methods: mechanical mixing, infiltration, and dip coating. The effects of SDC on the electrochemical performance of the LSCF cathodes are studied by electrochemical impedance spectroscopy (EIS) at 800 °C for 100 h. LSCF mechanically mixed with SDC as the cathode decreases the electrochemical performance of the half-cell; the LSCF cathode infiltrated with SDC offers faster activation and decreased resistance with thermal treatment time; and the LSCF cathode dip coated with SDC has the smallest polarization resistance. These cathodes also show clear microstructure differences at the cathode/interconnect interface after 100 h of thermal treatment. SrCrO4 phase forms on all the cathodes near the interconnect. Reactions between the mechanically mixed cathode and the YSZ electrolyte destroy the electrolyte. The influence of SDC catalyst on oxygen adsorption, dissociation, and incorporation is explained for each type of cathodes. Overall, dip coating method is recommended for incorporation of SDC into the LSCF cathode.

  18. Performance enhancement of low temperature polymer electrolyte membrane fuel cells by catalyst and support layer modifications

    NASA Astrophysics Data System (ADS)

    Hall, Timothy David

    Possible enhancement of low temperature polymer electrolyte membrane fuel cells (PEMFC) or direct methanol fuel cells (DMFC) was investigated by modifying catalyst and support layers. Platinum (Pt) and platinum cobalt (Pt xCo1-x) alloys were prepared by pulsed electrodeposition onto Toray carbon paper. Composite supports composed of either commercial multi-walled nanofiber (MWNF) mats or MWNF layers on a commercial backing were also investigated. X-ray diffraction (XRD), scanning electron microscopy (SEM), inductively coupled plasma-optical emission spectroscopy (ICP-OES), and energy dispersive x-ray (EDX) were used to characterize the surface structure, composition, and catalyst loading. Various electrochemical techniques with a wet electrochemical cell, a Nuvant multi-array system, and a Scribner fuel cell system were used to study and rank the effectiveness of the catalysts and supports toward both the methanol oxidation reaction and the oxygen reduction reaction. The activity toward methanol oxidation of the electrodeposited Pt catalyst was found to be dependent on the deposited mass. Further comparisons between commercial electrodes in the Nuvant system showed these deposits can yield activities comparable to those of commercially available electrodes. The structure of the Pt electrodeposits was highly non-uniform due to the H2 evolution during the deposition process blocking the cathodes surface. The activities of the planar structured PtxCo1-x deposits were insignificant for both oxygen reduction and methanol oxidation. The composition of the deposits ranged from 5 to 15 at% Pt. It was found by both the Nuvant and Scribner systems that the addition of a thin hydrophilic MWNF layer to a hydrophobic electrode would enhance the performance of a DMFC anode. In the Nuvant system, the addition of a thin hydrophilic MWNF layer to a hydrophobic electrode also enhanced the PEM cathode activity. This however was not corroborated by Scribner analysis, showing a

  19. New Cathode Materials for Intermediate Temperature Solid Oxide Fuel Cells

    SciTech Connect

    Allan J. Jacobson

    2006-09-30

    Operation of SOFCs at intermediate temperatures (500-800 C) requires new combinations of electrolyte and electrode materials that will provide both rapid ion transport across the electrolyte and electrode-electrolyte interfaces and efficient electrocatalysis of the oxygen reduction and fuel oxidation reactions. This project concentrates on materials and issues associated with cathode performance that are known to become limiting factors as the operating temperature is reduced. The specific objectives of the proposed research are to develop cathode materials that meet the electrode performance targets of 1.0 W/cm{sup 2} at 0.7 V in combination with YSZ at 700 C and with GDC, LSGM or bismuth oxide based electrolytes at 600 C. The performance targets imply an area specific resistance of {approx}0.5 {Omega}cm{sup 2} for the total cell. The research strategy is to investigate both established classes of materials and new candidates as cathodes, to determine fundamental performance parameters such as bulk diffusion, surface reactivity and interfacial transfer, and to couple these parameters to performance in single cell tests. The initial choices for study were perovskite oxides based on substituted LaFeO{sub 3} (P1 compositions), where significant data in single cell tests exist at PNNL for example, for La{sub 0.8}Sr{sub 0.2}FeO{sub 3} cathodes on both YSZ and CSO/YSZ. The materials selection was then extended to La{sub 2}NiO{sub 4} compositions (K1 compositions), and then in a longer range task we evaluated the possibility of completely unexplored group of materials that are also perovskite related, the ABM{sub 2}O{sub 5+{delta}}. A key component of the research strategy was to evaluate for each cathode material composition, the key performance parameters, including ionic and electronic conductivity, surface exchange rates, stability with respect to the specific electrolyte choice, and thermal expansion coefficients. In the initial phase, we did this in parallel with

  20. Cellulose-derived nitrogen and phosphorus dual-doped carbon as high performance oxygen reduction catalyst in microbial fuel cell

    NASA Astrophysics Data System (ADS)

    Liu, Qin; Zhou, Yan; Chen, Shuiliang; Wang, Zejie; Hou, Haoqing; Zhao, Feng

    2015-01-01

    Microbial fuel cells (MFCs) couple functions of waste removal and electricity generation. The future success of MFCs inevitably depends on the increase of performance at decrease of material cost. Therefore, the use of renewable and sustainable materials, e.g. cellulose, to prepare high performance materials for MFCs would be an inevitable trend. In this communication, nitrogen and phosphorus dual-doped carbons were prepared by pyrolysis of cellulose using ammonium phosphate as doping source and employed as oxygen reduction reaction (ORR) catalyst in air-cathode of MFCs. A maximum power density of 2293 ± 50 mW m-2 was generated by the air-cathode using the dual-doped carbon catalyst, which was higher than the air-cathode using Pt/C catalyst with Pt load of 0.5 mg cm-2 (1680 ± 32 mW m-2). This study provided a facile and sustainable way to prepare low-cost and high-efficient ORR catalyst for scaled-up MFC applications.

  1. Electrode surface modification for cathode catalysis in semi-fuel cells. End of the year report

    SciTech Connect

    Bessette, R.R.

    1998-07-07

    The program objective is to identify the optimum conditions for fabricating a stable electrocatalytic cathode of palladium and iridium that will: improve the cathode polarization potential, diminish the heterogeneous decomposition and direct chemical reactions and significantly improve (gain of 50%) the overall electrochemical cell efficiency. The second objective is to evaluate the electrochemical performance of the catalyzed cathode. The third objective is to characterize the structure and composition of the catalytic surface.

  2. Metal-free selenium doped carbon nanotube/graphene networks as a synergistically improved cathode catalyst for oxygen reduction reaction.

    PubMed

    Jin, Zhiping; Nie, Huagui; Yang, Zhi; Zhang, Jing; Liu, Zheng; Xu, Xiangju; Huang, Shaoming

    2012-10-21

    The ongoing search for new non-precious-metal catalysts (NPMCs) with excellent electrocatalytic performance to replace Pt-based catalysts has been viewed as an important strategy to promote the development of fuel cells. Recent studies have proven that carbon materials doped with atoms which have a relatively small atomic size (e.g. N, B, P or S), have also shown pronounced catalytic activity. Herein, we demonstrate the successful fabrication of CNT/graphene doped with Se atoms, which has a relatively large atomic size, by a simple, economical, and scalable approach. The electrocatalytic performance of the resulting Se-doped CNT-graphene catalyst exhibits excellent catalytic activity, long-term stability, and a high methanol tolerance compared to commercial Pt/C catalysts. Our results confirmed that combining CNTs with graphene is an effective strategy to synergistically improve ORR activity. More importantly, it is also suggested that the development of graphite materials doped with Se or other heteroatoms of large size will open up a new route to obtain ideal NPMCs with realistic value for fuel cell applications. PMID:22955444

  3. A catalyst layer optimisation approach using electrochemical impedance spectroscopy for PEM fuel cells operated with pyrolysed transition metal-N-C catalysts

    NASA Astrophysics Data System (ADS)

    Malko, Daniel; Lopes, Thiago; Ticianelli, Edson A.; Kucernak, Anthony

    2016-08-01

    The effect of the ionomer to carbon (I/C) ratio on the performance of single cell polymer electrolyte fuel cells is investigated for three different types of non-precious metal cathodic catalysts. Polarisation curves as well as impedance spectra are recorded at different potentials in the presence of argon or oxygen at the cathode and hydrogen at the anode. It is found that a optimised ionomer content is a key factor for improving the performance of the catalyst. Non-optimal ionomer loading can be assessed by two different factors from the impedance spectra. Hence this observation could be used as a diagnostic element to determine the ideal ionomer content and distribution in newly developed catalyst-electrodes. An electrode morphology based on the presence of inhomogeneous resistance distribution within the porous structure is suggested to explain the observed phenomena. The back-pressure and relative humidity effect on this feature is also investigated and supports the above hypothesis. We give a simple flowchart to aid optimisation of electrodes with the minimum number of trials.

  4. Nanoscale alloying effect of gold-platinum nanoparticles as cathode catalysts on the performance of a rechargeable lithium-oxygen battery.

    PubMed

    Yin, Jun; Fang, Bin; Luo, Jin; Wanjala, Bridgid; Mott, Derrick; Loukrakpam, Rameshowri; Ng, Mei Shan; Li, Zheng; Hong, Jian; Whittingham, M Stanley; Zhong, Chuan-Jian

    2012-08-01

    The understanding of nanoscale alloying or the phase segregation effect of alloy nanoparticles on the catalytic properties is important for a rational design of the desired catalysts for a specific reaction. This paper describes findings of an investigation into this type of structural effect for carbon-supported bimetallic gold-platinum nanoparticles as cathode catalysts in a rechargeable lithium-oxygen battery. The nanoscale structural characteristics in terms of size, alloying and phase segregation were shown to affect the catalytic properties of the catalysts in the Li-O(2) battery. In addition to the composition effect, the catalysts with a fully alloyed phase structure were found to exhibit a smaller discharge-charge voltage difference and a higher discharge capacity than those with a partial phase segregation structure. This finding is significant for the design of alloy nanoparticles as air cathode catalysts in rechargeable lithium-air batteries, demonstrating the importance of the control of the nanoscale composition and phase properties. PMID:22781275

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

    PubMed

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

    2016-09-01

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

  6. Carbon and binder free rechargeable Li-O2 battery cathode with Pt/Co3O4 flake arrays as catalyst

    NASA Astrophysics Data System (ADS)

    Zhao, Guangyu; Lv, Jixian; Xu, Zhanming; Zhang, Li; Sun, Kening

    2014-02-01

    Pt nanoparticles modified Co3O4 flake arrays are prepared by an electrochemically assisted method and the subsequent cool sputtering, a carbon and binder free approach. When used as the cathode catalysts of Li-O2 batteries, these porous films supply the O2 transport adequate channels by the macropores surrounded by Co3O4 flakes, which endow the cathodes stable two-phase interface in discharge/charge processes. The superior ability of Pt catalyzing O2 evolution leads the batteries showing a much lower overpotential (3.2 V) in charge process compared with those using pristine Co3O4 arrays as catalysts (4.0 V). The enhancement of decomposing the discharging precipitate promotes the Li-O2 batteries' reversibility obviously, which realize more than 30 discharge/charge cycles.

  7. Gold nanoparticles: novel catalyst for the preparation of direct methanol fuel cell.

    PubMed

    Kuralkar, Mayuri; Ingle, Avinash; Gaikwad, Swapnil; Gade, Aniket; Rai, Mahendra

    2015-04-01

    The authors report the biosynthesis of gold nanoparticles (Au-NPs) using plant pathogenic Phoma glomerata (MTCC 2210). The synthesis of nanoparticles was characterised by visual observation followed UV-visible spectrophotometric analysis, Fourier transform infrared spectroscopy and nanoparticle tracking analysis. Later, direct methanol fuel cell (DMFC) was constructed using two chambers (anodic chamber and cathodic chamber). These Au-NPs as catalysts have various advantages over the other catalysts that are used in the DMFC. Most importantly, it is cheaper as compared with other catalysts like platinum, and showed higher catalytic activity because of its effective surface structure. Being nano in size, it provides more surface area for the attachment of reactant molecules (methanol molecules). The DMFC catalysed by Au-NPs are found to be suitable to replace lithium ion battery technology in consumer electronics like cell phones, laptops and so on due to the fact that they can produce a high amount of energy in a small space. As long as fuel and air are supplied to the DMFC, it will continue to produce power, so it does not need to be recharged. The use of Au-NPs as catalyst in DMFC has not been reported in the past; it is reported here the first time. PMID:25829171

  8. Electrochemical Performance and Stability of the Cathode for Solid Oxide Fuel Cells IV. On the Ohmic loss in anode supported button cells with LSM or LSCF cathodes

    SciTech Connect

    Lu, Zigui; Zhou, Xiao Dong; Templeton, Jared W.; Stevenson, Jeffry W.

    2010-05-08

    Anode-supported solid oxide fuel cells (SOFC) with a variety of YSZ electrolyte thicknesses were fabricated by tape casting and lamination. The preparation of the YSZ electrolyte tapes with various thicknesses was accomplished by using doctor blades with different gaps between the precision machined, polished blade and the casting surface. The green tape was cut into discs, sintered at 1385°C for 2 h, and subsequently creep-flattened at 1350°C for 2 h. Either LSCF with an SDC interlayer or LSM+YSZ composite was used as the cathode material for the fuel cells. The ohmic resistances of these anode-supported fuel cells were characterized by electrochemical impedance spectroscopy at temperatures from 500°C to 750°C. A linear relationship was found between the ohmic resistance of the fuel cell and the YSZ electrolyte thickness at all the measuring temperatures for both LSCF and LSM+YSZ cathode fuel cells. The ionic conductivities of the YSZ electrolyte, derived for the fuel cells with LSM+YSZ or LSCF cathodes, were independent of the cathode material and cell configuration. The ionic conductivities of the YSZ electrolyte was slightly lower than that of the bulk material, possibly due to Ni-doping into the electrolyte. The fuel cell with a SDC interlayer and LSCF cathode showed larger intercept resistance than the fuel cell with LSM+YSZ cathode, which was possibly due to the imperfect contact between the SDC interlayer and the YSZ electrolyte and the migration of Zr into the SDC interlayer to form an insulating solid solution during cell fabrication. Calculations of the contribution of the YSZ electrolyte to the total ohmic resistance showed that YSZ was still a satisfactory electrolyte at temperatures above 650°C. Explorations should be directed to reduce the intercept resistance to achieve significant improvement in cell performance.

  9. Combinatorial synthesis and screening of fuel cell catalysts

    NASA Astrophysics Data System (ADS)

    Jayaraman, Shrisudersan

    Polymer electrolyte membrane fuel cells (PEMFCs) are compact power sources that can operate with high efficiencies and low emission of environmentally harmful gases. One of the major barriers impeding the development of PEMFCs as a competitive energy source is the inability of existing anode catalysts to oxidize fuels other than hydrogen at sufficient levels due to catalyst deactivation by carbon monoxide (CO) and other partial oxidation products. The focus of this research is the development and application of combinatorial strategies to construct and interrogate electrooxidation (anode) catalysts pertaining to PEMFCs to discover catalysts with enhanced performance in catalyst deactivating environments. A novel method (known as the "gel-transfer" method) for synthesizing catalyst composition gradient libraries for combinatorial catalyst discovery was developed. This method involved transferring a spatial concentration gradient of precursor metal salts created within a polymer gel on to a solid conducting substrate by electrochemical reduction. Chemically sensitive surface-imaging techniques, namely, scanning electrochemical microscopy (SECM) and optical screening with a pH-dependent fluorescence probe were used to characterize the combinatorial catalyst samples. The utility of SECM as a screening tool to measure the activity of multicomponent catalyst libraries towards fuel cell electrooxidation reactions was established with simple catalyst libraries including a platinum coverage gradient and platinum-ruthenium and platinum-ruthenium-molybdenum arrays. A platinum-ruthenium surface composition gradient was constructed through the gel-transfer method and its reactivity towards hydrogen oxidation in the presence of a catalyst poison (CO) was mapped using the SECM. Ruthenium composition between 20 and 30% exhibited superior performance than the rest of the binary. The gel-transfer method was extended to construct a ternary platinum-ruthenium-rhodium catalyst library

  10. Elucidating the degradation mechanism of the cathode catalyst of PEFCs by a combination of electrochemical methods and X-ray fluorescence spectroscopy.

    PubMed

    Monzó, J; van der Vliet, D F; Yanson, A; Rodriguez, P

    2016-08-10

    In this study, we report a methodology which enables the determination of the degradation mechanisms responsible for catalyst deterioration under different accelerated stress protocols (ASPs) by combining measurements of the electrochemical surface area (ECSA) and Pt content (by X-ray fluorescence). The validation of this method was assessed on high surface area unsupported Pt nanoparticles (Pt-NPs), Pt nanoparticles supported on TaC (Pt/TaC) and Pt nanoparticles supported on Vulcan carbon (Pt/Vulcan). In the load cycle protocol, the degradation of Pt-NPs and Pt/Vulcan follows associative processes (e.g. agglomeration) in the first 2000 cycles, however, in successive cycles the degradation goes through dissociative processes such as Pt dissolution, as is evident from a similar decay of ECSA and Pt content. In contrast, the degradation mechanism for Pt nanoparticles dispersed on TaC occurs continuously through the dissociative processes (e.g. Pt dissolution or particle detachment), with similar decay rates of both Pt content and ECSA. In the start-up/shut-down protocol, high surface area Pt-NPs follow associative processes (e.g. Ostwald ripening) in the first 4000 cycles, after which the degradation continues through dissociative processes. On the other hand, dissociative mechanisms always govern the degradation of Pt/TaC under start-up/shut-down protocol conditions. Finally, we report that Pt nanoparticles supported on TaC exhibit the highest catalytic activity and long term durability of the three nanoparticle systems tested. This makes Pt/TaC a potentially valuable catalyst system for application in polymer electrolyte fuel cell cathodes. PMID:27464340

  11. Cathode for a hall-heroult type electrolytic cell for producing aluminum

    DOEpatents

    Brown, Craig W.

    2004-04-13

    A method of producing aluminum from alumina in an electrolytic cell including using a cathode comprised of a base material having low electrical conductivity and wettable with molten aluminum to form a reaction layer having a high electrical conductivity on said base layer and a cathode bar extending from said reaction layer through said base material to conduct electrical current from said reaction layer.

  12. Oxygen-hydrogen fuel cell with an iodine-iodide cathode - A concept

    NASA Technical Reports Server (NTRS)

    Javet, P.

    1970-01-01

    Fuel cell uses a porous cathode through which is fed a solution of iodine in aqueous iodide solution, the anode is a hydrogen electrode. No activation polarization appears on the cathode because of the high exchange-current density of the iodine-iodide electrode.

  13. Electrochemical storage cell comprising an anode and a cathode made of a synthetic polymer

    SciTech Connect

    Weddigen, G.

    1985-07-30

    Rechargeable electrochemical storage cell with an anode and a cathode, both of which are made of synthetic polymer and are surrounded by a liquid electrolyte. The anode as well as the cathode are made of synthetic polymers which has triaromatic methane units as building blocks, and the polymers are electrochemically doped reversably with ionic doping substances.

  14. Development of Lanthanum Ferrite SOFC Cathodes

    SciTech Connect

    Simner, Steve P.; Bonnett, Jeff F.; Canfield, Nathan L.; Meinhardt, Kerry D.; Shelton, Jayne P.; Sprenkle, Vince L.; Stevenson, Jeffry W.

    2003-01-01

    A number of studies have been conducted concerning compositional/microstructural modifications of a Sr-doped lanthanum ferrite (LSF) cathode and protective Sm-doped ceria (SDC) layer in an anode supported solid oxide fuel cell (SOFC). Emphasis was placed on achieving enhanced low temperature (700-800 degrees C) performance, and long-term cell stability. Investigations involved manipulation of the lanthanum ferrite chemistry, addition of noble metal oxygen reduction catalysts, incorporation of active cathode layer compositions containing Co, Fe and higher Sr contents, and attempts to optimize the ceria barrier layer between the LSF cathode and YSZ electrolyte.

  15. Sustainable energy recovery in wastewater treatment by microbial fuel cells: stable power generation with nitrogen-doped graphene cathode.

    PubMed

    Liu, Yuan; Liu, Hong; Wang, Chuan; Hou, Shuang-Xia; Yang, Nuan

    2013-12-01

    Microbial fuel cells (MFCs) recover energy sustainably in wastewater treatment. Performance of non-noble cathode catalysts with low cost in neutral medium is vital for stable power generation. Nitrogen-doped graphene (NG) as cathode catalyst was observed to exhibit high and durable activity at buffered pH 7.0 during electrochemical measurements and in MFCs with respect to Pt/C counterpart. Electrochemical measurements showed that the oxygen reduction reaction (ORR) on NG possessed sustained activity close to the state-of-art Pt/C in terms of onset potential and electron transfer number. NG-MFCs displayed maximum voltage output of 650 mV and maximum power density of 776 ± 12 mW m(-2), larger than 610 mV and 750 ± 19 mW m(-2) of Pt/C-MFCs, respectively. Furthermore, long-time test lasted over 90 days, during which the maximum power density of NG-MFCs declined by 7.6%, with stability comparable to Pt/C-MFCs. Structure characterization of NG implied that the relatively concentrated acidic oxygen-containing groups improved such long-time stability by repelling the protons due to the same electrostatic force, and thus the C-N active centers for ORR were left undestroyed. These findings demonstrated the competitive advantage of NG to advance the application of MFCs for recovering biomass energy in treatment of wastewater with neutral pH. PMID:24219223

  16. Thin Film Catalyst Layers for Direct Methanol Fuel Cells

    NASA Technical Reports Server (NTRS)

    Witham, C. K.; Chun, W.; Ruiz, R.; Valdez, T. I.; Narayanan, S. R.

    2000-01-01

    One of the primary obstacles to the widespread use of the direct methanol fuel cell (DMFC) is the high cost of the catalyst. Therefore, reducing the catalyst loading well below the current level of 8-12 mg/cm 2 would be important to commercialization. The current methods for preparation of catalyst layers consisting of catalyst, ionomer and sometimes a hydrophobic additive are applied by either painting, spraying, decal transfer or screen printing processes. Sputter deposition is a coating technique widely used in manufacturing and therefore particularly attractive. In this study we have begun to explore sputtering as a method for catalyst deposition. Present experiments focus on Pt-Ru catalyst layers for the anode.

  17. On the mechanism of operation of a cathode spot cell in a vacuum arc

    SciTech Connect

    Mesyats, G. A.; Petrov, A. A.; Bochkarev, M. B.; Barengolts, S. A.

    2014-05-05

    The erosive structures formed on a tungsten cathode as a result of the motion of the cathode spot of a vacuum arc over the cathode surface have been examined. It has been found that the average mass of a cathode microprotrusion having the shape of a solidified jet is approximately equal to the mass of ions removed from the cathode within the lifetime of a cathode spot cell carrying a current of several amperes. The time of formation of a new liquid-metal jet under the action of the reactive force of the plasma ejected by the cathode spot is about 10 ns, which is comparable to the lifetime of a cell. The growth rate of a liquid-metal jet is ∼10{sup 4} cm/s. The geometric shape and size of a solidified jet are such that a new explosive emission center (spot cell) can be initiated within several nanoseconds during the interaction of the jet with the dense cathode plasma. This is the underlying mechanism of the self-sustained operation of a vacuum arc.

  18. Ceria catalyst for inert-substrate-supported tubular solid oxide fuel cells running on methane fuel

    NASA Astrophysics Data System (ADS)

    Zhao, Kai; Kim, Bok-Hee; Du, Yanhai; Xu, Qing; Ahn, Byung-Guk

    2016-05-01

    A ceria catalyst is applied to an inert-substrate supported tubular single cell for direct operation on methane fuel. The tubular single cell comprises a porous yttria-stabilized zirconia (YSZ) supporter, a Ni-Ce0.8Sm0.2O1.9 anode, a YSZ/Ce0.8Sm0.2O1.9 bi-layer electrolyte, and a La0.6Sr0.4Co0.2Fe0.8O3-δ cathode. The ceria catalyst is incorporated into the porous YSZ supporter layer by a cerium nitrate impregnation. The effects of ceria on the microstructure and electrochemical performance of the tubular single cell are investigated with respect to the number of impregnations. The optimum number of impregnations is determined to be four based on the maximum power density and polarization property of the tubular single cell in hydrogen and methane fuels. At 700 °C, the tubular single cell shows similar maximum power densities of ∼260 mW cm-2 in hydrogen and methane fuels, respectively. Moreover, the ceria catalyst significantly improves the performance stability of the cell running on methane fuel. At a current density of 350 mA cm-2, the single cell shows a low degradation rate of 2.5 mV h-1 during the 13 h test in methane fuel. These results suggest the feasibility of applying the ceria catalyst to the inert-substrate supported tubular single cell for direct operation on methane fuel.

  19. A comparative study of Pt/C cathodes in Sn 0.9In 0.1P 2O 7 and H 3PO 4 ionomers for high-temperature proton exchange membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Jin, Y. C.; Okada, M.; Hibino, T.

    New Pt/C cathodes with many reaction sites for the oxygen reduction reaction as well as high tolerance to Pt corrosion have been designed for high-temperature proton exchange membrane fuel cells (PEMFCs), wherein a composite mixture of Sn 0.9In 0.1P 2O 7 (SIPO) and sulfonated polystyrene-b-poly(ethylene/butylene)-b-polystyrene (sSEBS) functioned as an ionomer. The microstructure of the Pt-SIPO-sSEBS/C cathode was characterized by homogeneous distribution of the ionomer over the catalyst layer and close contact between the ionomer and the Pt/C powder. As a result, the activation and concentration overpotentials of the Pt-SIPO-sSEBS/C cathode between 100 and 200 °C were lower than those of an H 3PO 4-impregnated Pt/C cathode, which suggests that the present ionomer can avoid poisoning of Pt by phosphate anions and the limitation of gas diffusion through the catalyst layer. Moreover, agglomeration of Pt in the Pt-SIPO-sSEBS/C cathode was not observed during a durability test at 150 °C for 6 days, although it was significant in the Pt-H 3PO 4/C cathode. Therefore, it is concluded that the Pt-SIPO-sSEBS/C electrode is a very promising cathode candidate for high-temperature PEMFCs.

  20. Oxygen reduction kinetics on graphite cathodes in sediment microbial fuel cells.

    PubMed

    Renslow, Ryan; Donovan, Conrad; Shim, Matthew; Babauta, Jerome; Nannapaneni, Srilekha; Schenk, James; Beyenal, Haluk

    2011-12-28

    Sediment microbial fuel cells (SMFCs) have been used as renewable power sources for sensors in fresh and ocean waters. Organic compounds at the anode drive anodic reactions, while oxygen drives cathodic reactions. An understanding of oxygen reduction kinetics and the factors that determine graphite cathode performance is needed to predict cathodic current and potential losses, and eventually to estimate the power production of SMFCs. Our goals were to (1) experimentally quantify the dependence of oxygen reduction kinetics on temperature, electrode potential, and dissolved oxygen concentration for the graphite cathodes of SMFCs and (2) develop a mechanistic model. To accomplish this, we monitored current on polarized cathodes in river and ocean SMFCs. We found that (1) after oxygen reduction is initiated, the current density is linearly dependent on polarization potential for both SMFC types; (2) current density magnitude increases linearly with temperature in river SMFCs but remains constant with temperature in ocean SMFCs; (3) the standard heterogeneous rate constant controls the current density temperature dependence; (4) river and ocean SMFC graphite cathodes have large potential losses, estimated by the model to be 470 mV and 614 mV, respectively; and (5) the electrochemical potential available at the cathode is the primary factor controlling reduction kinetic rates. The mechanistic model based on thermodynamic and electrochemical principles successfully fit and predicted the data. The data, experimental system, and model can be used in future studies to guide SMFC design and deployment, assess SMFC current production, test cathode material performance, and predict cathode contamination. PMID:22052235

  1. Collaboration between primitive cell membranes and soluble catalysts.

    PubMed

    Adamala, Katarzyna P; Engelhart, Aaron E; Szostak, Jack W

    2016-01-01

    One widely held model of early life suggests primitive cells consisted of simple RNA-based catalysts within lipid compartments. One possible selective advantage conferred by an encapsulated catalyst is stabilization of the compartment, resulting from catalyst-promoted synthesis of key membrane components. Here we show model protocell vesicles containing an encapsulated enzyme that promotes the synthesis of simple fatty acid derivatives become stabilized to Mg(2+), which is required for ribozyme activity and RNA synthesis. Thus, protocells capable of such catalytic transformations would have enjoyed a selective advantage over other protocells in high Mg(2+) environments. The synthetic transformation requires both the catalyst and vesicles that solubilize the water-insoluble precursor lipid. We suggest that similar modified lipids could have played a key role in early life, and that primitive lipid membranes and encapsulated catalysts, such as ribozymes, may have acted in conjunction with each other, enabling otherwise-impossible chemical transformations within primordial cells. PMID:26996603

  2. Collaboration between primitive cell membranes and soluble catalysts

    PubMed Central

    Adamala, Katarzyna P.; Engelhart, Aaron E.; Szostak, Jack W.

    2016-01-01

    One widely held model of early life suggests primitive cells consisted of simple RNA-based catalysts within lipid compartments. One possible selective advantage conferred by an encapsulated catalyst is stabilization of the compartment, resulting from catalyst-promoted synthesis of key membrane components. Here we show model protocell vesicles containing an encapsulated enzyme that promotes the synthesis of simple fatty acid derivatives become stabilized to Mg2+, which is required for ribozyme activity and RNA synthesis. Thus, protocells capable of such catalytic transformations would have enjoyed a selective advantage over other protocells in high Mg2+ environments. The synthetic transformation requires both the catalyst and vesicles that solubilize the water-insoluble precursor lipid. We suggest that similar modified lipids could have played a key role in early life, and that primitive lipid membranes and encapsulated catalysts, such as ribozymes, may have acted in conjunction with each other, enabling otherwise-impossible chemical transformations within primordial cells. PMID:26996603

  3. Two-phase flow and transport in the air cathode of proton exchange membrane fuel cells

    SciTech Connect

    WANG,Z.H.; WANG,C.Y.; CHEN,KEN S.

    2000-03-20

    Two-phase flow and transport of reactants and products in the air cathode of proton exchange membrane (PEM) fuel cells is studied analytically and numerically. Four regimes of water distribution and transport are classified by defining three threshold current densities and a maximum current density. They correspond to first appearance of liquid water at the membrane/cathode interface, extension of the gas-liquid two-phase zone to the cathode/channel interface, saturated moist air exiting the gas channel, and complete consumption of oxygen by the electrochemical reaction. When the cell operates above the first threshold current density, liquid water appears and a two-phase zone forms within the porous cathode. A two-phase, multi-component mixture model in conjunction with a finite-volume-based computational fluid dynamics (CFD) technique is applied to simulate the cathode operation in this regime. The model is able to handle the situation where a single-phase region co-exists with a two-phase zone in the air cathode. For the first time, the polarization curve as well as water and oxygen concentration distributions encompassing both single- and two-phase regimes of the air cathode are presented. Capillary action is found to be the dominant mechanism for water transport inside the two-phase zone. The liquid water saturation within the cathode is predicted to reach 6.3% at 1.4 A/cm{sup 2}.

  4. Iron-based perovskite cathodes for solid oxide fuel cells

    DOEpatents

    Ralph, James M.; Rossignol, Cecile C.R.; Vaughey, John T.

    2007-01-02

    An A and/or A' site deficient perovskite of general formula of (A.sub.1-xA'.sub.x).sub.1-yFeO.sub.3-.delta. or of general formula A.sub.1-x-yA'.sub.xFeO.sub.3-67, wherein A is La alone or with one or more of the rare earth metals or a rare earth metal other than Ce alone or a combination of rare earth metals and X is in the range of from 0 to about 1; A' is Sr or Ca or mixtures thereof and Y is in the range of from about 0.01 to about 0.3; .delta. represents the amount of compensating oxygen loss. If either A or A' is zero the remaining A or A' is deficient. A fuel cell incorporating the inventive perovskite as a cathode is disclosed as well as an oxygen separation membrane. The inventive perovskite is preferably single phase.

  5. Graphitic biochar as a cathode electrocatalyst support for microbial fuel cells.

    PubMed

    Huggins, Tyler M; Pietron, Jeremy J; Wang, Heming; Ren, Zhiyong Jason; Biffinger, Justin C

    2015-11-01

    Graphitic biochar (BC) was generated using high temperature gasification and alkaline post-treatment (BCw) of wood-based biomass. The BCw was evaluated as a manganese oxide electrocatalytic support (MnO/BCw) and microbial fuel cell (MFC) air cathode. Nano-structured MnO2 crystals were successfully immobilized on biomass-based graphitic sheets and characterized using physical, chemical, and electrochemical analyses. Cyclic voltammetry of MnO/BCw/Nafion inks showed electrochemical features typical of β-MnO2 with a current density of 0.9 mA cm(-2). BC showed satisfactory maximum power densities of 146.7 mW m(-2) (BCw) and 187.8 W m(-2) (MnO/BCw), compared with Vulcan Carbon (VC) (156.8 mW m(-2)) and manganese oxide VC composites (MnO/VC) (606.1 mW m(-2)). These materials were also tested as oxygen reduction reaction (ORR) catalysts for single chamber MFCs inoculated with anaerobic sludge. Our results demonstrate that BC can serve as an effective, low cost, and scalable material for MFC application. PMID:26141670

  6. Preparation of nano-sized nickel as anode catalyst for direct urea and urine fuel cells

    NASA Astrophysics Data System (ADS)

    Lan, Rong; Tao, Shanwen

    Nano-sized nickel with primary particle size of 2-3 nm has been successfully prepared for use as efficient anode catalysts in urea and urine fuel cells. XRD, SEM and TEM were used for characterisation of nano-sized nickel. Based on the previous communication, the performance of urea and urine fuel cells has been further improved when the relative humidity at the cathode was 100%. A maximum power density of 14.2 mW cm -2 was achieved when 1 M urea was used as fuel, humidified air as oxidant. The performance of urine fuel cells operating above room temperature was also reported for the first time and a power density of 4.23 mW cm -2 was achieved at 60 °C indicating potential application in urea-rich waste water treatment.

  7. Electricity generation and nutrients removal from high-strength liquid manure by air-cathode microbial fuel cells.

    PubMed

    Lin, Hongjian; Wu, Xiao; Nelson, Chad; Miller, Curtis; Zhu, Jun

    2016-01-01

    Air-cathode microbial fuel cells (MFCs) are widely tested to recover electrical energy from waste streams containing organic matter. When high-strength wastewater, such as liquid animal manure, is used as a medium, inhibition on anode and cathode catalysts potentially impairs the effectiveness of MFC performance in power generation and pollutant removal. This study evaluated possible inhibitive effects of liquid swine manure components on MFC power generation, improved liquid manure-fed MFCs performance by pretreatment (dilution and selective adsorption), and modeled the kinetics of organic matter and nutrients removal kinetics. Parameters monitored included pH, conductivity, chemical oxygen demand (COD), volatile fatty acids (VFAs), total ammoniacal nitrogen (TAN), nitrite, nitrate, and phosphate concentrations. The removals of VFA and TAN were efficient, indicated by the short half-life times of 4.99 and 7.84 d, respectively. The mechanism for phosphate decrease was principally the salt precipitation on cathode, but the removal was incomplete after 42-d operation. MFC with an external resistor of 2.2 kΩ and fed with swine wastewater generated relatively small power (28.2 μW), energy efficiency (0.37%) and Coulombic efficiency (1.5%). Dilution of swine wastewater dramatically improved the power generation as the inhibitory effect was decreased. Zeolite and granular activated carbon were effective in the selective adsorption of ammonia or organic matter in swine wastewater, and so substantially improved the power generation, energy efficiency, and Coulombic efficiency. A smaller external resistor in the circuit was also observed to promote the organic matter degradation and thus to shorten the treatment time. Overall, air-cathode MFCs are promising for generating electrical power from livestock wastewater and meanwhile reducing the level of organic matter and nutrients. PMID:26654000

  8. Quantifying the Water Content in the Cathode of Enzyme Fuel Cells via Neutron Imaging

    SciTech Connect

    Aaron, D; Borole, Abhijeet P; Hussey , Daniel; Jacobson, David; Yiacoumi, Sotira; Tsouris, Costas

    2011-01-01

    Neutron imaging was used to study cathode water content over time in a three-dimensional-cathode enzyme fuel cell (EFC). A porous carbon felt cathode allowed air to flow through the electrode. A solution with laccase and a mediator formed an aqueous layer on the electrode surface. Water loss was observed in situ via neutron imaging for varying experimental conditions, including flow rates of hydrogen and air, cathode inlet humidity, volume of enzyme solution, and its composition. Cathode water loss occurred for all experimental conditions, but the loss rate was noticeably reduced when a high-salt-concentration enzyme solution was used in the cathode in conjunction with increased humidity in the air feed stream. Results from neutron imaging and power density analysis were used in analyzing the causes that could contribute to EFC water loss. An increase in temperature due to the exothermic cathode reaction is considered a plausible cause of cathode water loss via evaporation. This is the first reported application of neutron imaging as a technique to study EFC water management. The results suggest that neutron imaging can be employed to provide a better understanding of EFC phenomena and thereby contribute to design and operational improvements of EFCs.

  9. The Impact of Cathode Material and Shape on Current Density in an Aluminum Electrolysis Cell

    NASA Astrophysics Data System (ADS)

    Song, Yang; Peng, Jianping; Di, Yuezhong; Wang, Yaowu; Li, Baokuan; Feng, Naixiang

    2016-02-01

    A finite element model was developed to determine the impact of cathode material and shape on current density in an aluminum electrolysis cell. For the cathode material, results show that increased electrical resistivity leads to a higher cathode voltage drop; however, the horizontal current is reduced in the metal. The horizontal current magnitude for six different cathode materials in decreasing order is graphitized, semi-graphitized, full graphitic, 50% anthracite (50% artificial graphite), 70% anthracite (30% artificial graphite), 100% anthracite. The modified cathode shapes with an inclined cathode surface, higher collector bar and cylindrical protrusions are intended to improve horizontal current and flow resistance. Compared to a traditional cathode, modified collector bar sizes of 70 mm × 230 mm and 80 mm × 270 mm can reduce horizontal current density component Jx by 10% and 19%, respectively, due to better conductivity of the steel. The horizontal current in the metal decreases with increase of cathode inclination. The peak value of Jx can be approximately reduced by 20% for a 2° change in inclination. Cylindrical protrusions lead to local horizontal current increase on their tops, but the average current is less affected and the molten metal is effectively slowed down.

  10. The development of catalytic performance by coating Pt-Ni on CMI7000 membrane as a cathode of a microbial fuel cell.

    PubMed

    Cetinkaya, Afsin Y; Ozdemir, Oguz Kaan; Koroglu, Emre Oguz; Hasimoglu, Aydin; Ozkaya, Bestami

    2015-11-01

    Performance of cathode materials in microbial fuel cell (MFC) from dairy wastewater has been investigated in laboratory tests. Both cyclic voltammogram experiments and MFC tests showed that Pt-Ni cathode much better than pure Pt cathode. MFC with platinum cathode had the maximum power density of 0.180 W m(-2) while MFC with Pt:Ni (1:1) cathode produced the maximum power density of 0.637 W m(-2), even if the mass mixing ratio of Pt is lower in the alloy were used. The highest chemical oxygen demand (COD) removal efficiency was around 82-86% in both systems. The cyclic voltammogram (CV) analyses show that Pt:Ni (1:1) offers higher specific surface area than Pt alone does. X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM) results showed that entire Pt:Ni (1:1) alloys can reduce the oxygen easily than pure platinum, even though less precious metal amount. The main outcome of this study is that Pt-Ni, may serve as a alternative catalyst in MFC applications. PMID:26116447

  11. Layered Nickel Oxide-Based Cathodes for Lithium Cells: Analysis ofPerformance Loss Mechanisms

    SciTech Connect

    Kerlau, Marie; Reimer, Jeffrey A.; Cairns, Elton J.

    2004-10-01

    Spectroscopic and electrochemical diagnostic measurements are reported for the cell components of a Generation 2 (Gen 2) Li-Ion cell from the US Department of Energy's Advanced Technology Development (ATD) project. The cells are composed of LiNi{sub 0.8}Co{sub 0.15}Al{sub 0.05}O{sub 2} positive electrodes (cathode), carbon graphite anodes and electrolyte consisting of 1.2 M LiPF{sub 6} in EC:EMC 3:7. Fluorophosphates were observed by {sup 19}F and {sup 31}P NMR in the electrolyte obtained from a Gen 2 cell aged 72 weeks at 45 C and presenting 50% power fade. These electrolyte decomposition products were also observed by {sup 31}P solid-state NMR on the surface of the cathode of the same cell. Samples were cut from the aged cathode from the original cell, subjected to different treatments (ultrasonic washing in anhydrous DMC, pressing, ultrasonic washing and pressing), and subsequently reassembled into small lab cells for electrochemical characterization. These treatments recovered the capacity of the electrodes to within a few percent of the original value, with the most improvement being obtained with the washed and pressed cathode. The impedance of the cathodes was also lowered after the ultrasonic washing and pressing treatments. Electron microscopy revealed that the ultrasonic washing of the aged Gen 2 cathode material resulted in the removal of small particles covering the surface of the active cathode. These findings are interpreted in terms of a model whereby capacity loss, and thus power capability, is restored by removing the fluorophosphate deposit and restoring electronic contact to the active cathode material.

  12. Simple template fabrication of porous MnCo2O4 hollow nanocages as high-performance cathode catalysts for rechargeable Li-O2 batteries

    NASA Astrophysics Data System (ADS)

    Cao, Y. L.; Lv, F. C.; Yu, S. C.; Xu, J.; Yang, X.; Lu, Z. G.

    2016-04-01

    Porous MnCo2O4 hollow nanocages have been fabricated via a simple template method using carbon spheres as a template. The hydrophilic surface of carbon spheres can adsorb Mn2+ and Co2+ ions simultaneously to form Mn,Co-adsorbed carbon spheres. The calcination of Mn,Co-adsorbed carbon spheres can result in porous hollow nanocages of MnCo2O4. The MnCo2O4 hollow nanocages are built by nanoscale MnCo2O4 crystals. Because of the unique porous hollow nanostructures, the resulting MnCo2O4/KB cathode shows an efficient electrocatalytic performance in LiTFSI/TEGDME electrolyte-based Li-O2 batteries. The MnCo2O4 hollow nanocages as the cathode catalysts can deliver better performance during the discharge/charge processes and good cycle stability compared with that of the pure KB carbon. The preliminary results manifest that porous MnCo2O4 hollow nanocages are promising high-performance cathode catalysts for Li-O2 batteries. This template technique is a simple, general, low-cost and controllable method and can be extended to prepare other transition metal oxide hollow nanostructures.

  13. Simple template fabrication of porous MnCo2O4 hollow nanocages as high-performance cathode catalysts for rechargeable Li-O2 batteries.

    PubMed

    Cao, Y L; Lv, F C; Yu, S C; Xu, J; Yang, X; Lu, Z G

    2016-04-01

    Porous MnCo2O4 hollow nanocages have been fabricated via a simple template method using carbon spheres as a template. The hydrophilic surface of carbon spheres can adsorb Mn(2+) and Co(2+) ions simultaneously to form Mn,Co-adsorbed carbon spheres. The calcination of Mn,Co-adsorbed carbon spheres can result in porous hollow nanocages of MnCo2O4. The MnCo2O4 hollow nanocages are built by nanoscale MnCo2O4 crystals. Because of the unique porous hollow nanostructures, the resulting MnCo2O4/KB cathode shows an efficient electrocatalytic performance in LiTFSI/TEGDME electrolyte-based Li-O2 batteries. The MnCo2O4 hollow nanocages as the cathode catalysts can deliver better performance during the discharge/charge processes and good cycle stability compared with that of the pure KB carbon. The preliminary results manifest that porous MnCo2O4 hollow nanocages are promising high-performance cathode catalysts for Li-O2 batteries. This template technique is a simple, general, low-cost and controllable method and can be extended to prepare other transition metal oxide hollow nanostructures. PMID:26894375

  14. Graphitic Carbon Nitride Supported Catalysts for Polymer Electrolyte Fuel Cells.

    PubMed

    Mansor, Noramalina; Jorge, A Belen; Corà, Furio; Gibbs, Christopher; Jervis, Rhodri; McMillan, Paul F; Wang, Xiaochen; Brett, Daniel J L

    2014-04-01

    Graphitic carbon nitrides are investigated for developing highly durable Pt electrocatalyst supports for polymer electrolyte fuel cells (PEFCs). Three different graphitic carbon nitride materials were synthesized with the aim to address the effect of crystallinity, porosity, and composition on the catalyst support properties: polymeric carbon nitride (gCNM), poly(triazine) imide carbon nitride (PTI/Li(+)Cl(-)), and boron-doped graphitic carbon nitride (B-gCNM). Following accelerated corrosion testing, all graphitic carbon nitride materials are found to be more electrochemically stable compared to conventional carbon black (Vulcan XC-72R) with B-gCNM support showing the best stability. For the supported catalysts, Pt/PTI-Li(+)Cl(-) catalyst exhibits better durability with only 19% electrochemical surface area (ECSA) loss versus 36% for Pt/Vulcan after 2000 scans. Superior methanol oxidation activity is observed for all graphitic carbon nitride supported Pt catalysts on the basis of the catalyst ECSA. PMID:24748912

  15. Graphitic Carbon Nitride Supported Catalysts for Polymer Electrolyte Fuel Cells

    PubMed Central

    2014-01-01

    Graphitic carbon nitrides are investigated for developing highly durable Pt electrocatalyst supports for polymer electrolyte fuel cells (PEFCs). Three different graphitic carbon nitride materials were synthesized with the aim to address the effect of crystallinity, porosity, and composition on the catalyst support properties: polymeric carbon nitride (gCNM), poly(triazine) imide carbon nitride (PTI/Li+Cl–), and boron-doped graphitic carbon nitride (B-gCNM). Following accelerated corrosion testing, all graphitic carbon nitride materials are found to be more electrochemically stable compared to conventional carbon black (Vulcan XC-72R) with B-gCNM support showing the best stability. For the supported catalysts, Pt/PTI-Li+Cl– catalyst exhibits better durability with only 19% electrochemical surface area (ECSA) loss versus 36% for Pt/Vulcan after 2000 scans. Superior methanol oxidation activity is observed for all graphitic carbon nitride supported Pt catalysts on the basis of the catalyst ECSA. PMID:24748912

  16. Pressure pyrolysed non-precious oxygen reduction catalysts for proton exchange membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Nallathambi, Vijayadurga

    2011-12-01

    Worldwide energy demand has driven long-term efforts towards developing a clean, hydrogen-based energy economy. Polymer electrolyte membrane fuel cells (PEMFC) are low emissions and high efficiency devices that utilize the power of hydrogen and are a key enabling technology for the hydrogen economy. Carbon supported platinum-black is the state-of the art catalyst for oxygen reduction in a PEMFC because it can withstand the acidic environment. However, the high cost and low abundance of this precious metal has limited large-scale commercialization of PEMFCs. Current efforts focus on developing alternative inexpensive, non-noble metal-based catalysts for oxygen reduction with performance comparable to conventional platinum based electrocatalysts. In this work, inexpensive metal-nitrogen-carbon (MNC) catalysts have been synthesized by pyrolyzing transition metal and nitrogen precursors together with high surface area carbon materials in a closed, constant-volume quartz tube. High pressure generated due to nitrogen precursor evaporation lead to increased surface nitrogen content in the catalysts post-pyrolysis. Electrochemical oxygen reduction activity of MNC catalysts was analyzed using half-cell Rotating Ring Disc Electrode (RRDE) studies. The effect of nitrogen precursor morphology on the generation of active sites has been explored in detail. By increasing the Nitrogen/Carbon ratio of the nitrogen precursor, the accessible active site density increased by reducing carbon deposition in the pores of the carbon support during pyrolysis. The most active catalysts were obtained using melamine, having a N/C ratio of 2. Single PEMFC measurements employing MNC catalysts as cathodes indicated kinetic current density as high as 15 A cm-3 at 0.8 ViR-free and over 100 h of stable current at 0.5 V were observed. Effects of carbon free ammonia generating solid nitrogen precursors such as urea and ammonium carbamate were also studied. These precursors etched the carbon support

  17. Platinum-cobalt catalysts for the oxygen reduction reaction in high temperature proton exchange membrane fuel cells - Long term behavior under ex-situ and in-situ conditions

    NASA Astrophysics Data System (ADS)

    Schenk, Alexander; Grimmer, Christoph; Perchthaler, Markus; Weinberger, Stephan; Pichler, Birgit; Heinzl, Christoph; Scheu, Christina; Mautner, Franz-Andreas; Bitschnau, Brigitte; Hacker, Viktor

    2014-11-01

    Platinum cobalt catalysts (Pt-Co) have attracted much interest as cathode catalysts for proton exchange membrane fuel cells (PEMFCs) due to their high activity toward oxygen reduction reaction (ORR). Many of the reported catalysts show outstanding performance in ex-situ experiments. However, the laborious synthesis protocols of these Pt-Co catalysts disable an efficient and economic production of membrane electrode assemblies (MEAs). We present an economic, flexible and continuous Pt-M/C catalyst preparation method as part of a large scale membrane electrode assembly manufacturing. In comparison, the as-prepared Pt-Co/C based high temperature (HT)-PEM MEA showed an equal performance to a commercially available HT-PEM MEA during 600 h of operation under constant load, although the commercial one had a significantly higher Pt loading at the cathode.

  18. Study of superhydrophobic electrosprayed catalyst layers using a localized reference electrode technique

    NASA Astrophysics Data System (ADS)

    Chaparro, A. M.; Ferreira-Aparicio, P.; Folgado, M. A.; Brightman, E.; Hinds, G.

    2016-09-01

    The performance of electrosprayed cathode catalyst layers in a polymer electrolyte membrane fuel cell (PEMFC) is studied using a localized reference electrode technique. Single cells with an electrosprayed cathode catalyst layer show an increase of >20% in maximum power density under standard testing conditions, compared with identical cells assembled with a conventional, state-of-the-art, gas diffusion cathode. When operated at high current density (1.2 A cm-2) the electrosprayed catalyst layers show more homogeneous distribution of the localized cathode potential, with a standard deviation from inlet to outlet of <50 mV, compared with 79 mV for the conventional gas diffusion cathode. Higher performance and homogeneity of cell response is attributed to the superhydrophobic nature of the macroporous electrosprayed catalyst layer structure, which enhances the rate of expulsion of liquid water from the cathode. On the other hand, at low current densities (<0.5 A cm-2), the electrosprayed layers exhibit more heterogeneous distribution of cathode potential than the conventional cathodes; this behavior is attributed to less favorable kinetics for oxygen reduction in very hydrophobic catalyst layers. The optimum performance may be obtained with electrosprayed catalyst layers employing a high Pt/C catalyst ratio.

  19. CeO2 nanocubes-graphene oxide as durable and highly active catalyst support for proton exchange membrane fuel cell

    PubMed Central

    Lei, M.; Wang, Z. B.; Li, J. S.; Tang, H. L.; Liu, W. J.; Wang, Y. G.

    2014-01-01

    Rapid degradation of cell performance still remains a significant challenge for proton exchange membrane fuel cell (PEMFC). In this work, we develop novel CeO2 nanocubes-graphene oxide nanocomposites as durable and highly active catalyst support for proton exchange membrane fuel cell. We show that the use of CeO2 as the radical scavenger in the catalysts remarkably improves the durability of the catalyst. The catalytic activity retention of Pt-graphene oxide-8 wt.% CeO2 nanocomposites reaches as high as 69% after 5000 CV-cycles at a high voltage range of 0.8–1.23 V, in contrast to 19% for that of the Pt-graphene oxide composites. The excellent durability of the Pt-CeO2 nanocubes-graphene oxide catalyst is attributed to the free radical scavenging activity of CeO2, which significantly slows down the chemical degradation of Nafion binder in catalytic layers, and then alleviates the decay of Pt catalysts, resulting in the excellent cycle life of Pt-CeO2-graphene oxide nanocomposite catalysts. Additionally, the performance of single cell assembled with Nafion 211 membrane and Pt-CeO2-graphene oxide catalysts with different CeO2 contents in the cathode as well as the Pt-C catalysts in the anode are also recorded and discussed in this study. PMID:25491655

  20. Oxidation-resistant catalyst supports for proton exchange membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Chhina, Harmeet

    In automotive applications, when proton exchange membrane fuel cells (PEMFCs) are subjected to frequent startup-shutdown cycles, a significant drop in performance is observed. One reason for this drop in performance is oxidation of the carbon in the catalyst layer when cathode potential excursions as high as 1.5V are observed. In this work, non-carbon based catalyst support materials were studied. The materials investigated include: tungsten carbide (WC), tungsten oxide (WOx), and niobium (Nb) or tungsten (W) doped titania. Platinum was dispersed on commercial samples of WC and WO x. Stability tests were performed by stepping the materials between 0.6 to 1.8V. Higher stability of both WC and WOx was observed compared to carbon based commercial catalyst (HiSpec 4000). The performance of Pt supported on WC or WOx was found to be lower than that of Pt/C due to poor dispersion of Pt on these low surface area commercial powders. High surface area Nb and W doped titania materials synthesized using sol-gel techniques were subjected to several heat treatments and atmospheres, and their resulting physical properties characterized. The materials' phase changes and their impact on electrical conductivity were evaluated. W doped titania was found to be resistive, and for Nb doped titania, the rutile phase was found to be more conductive than the anatase phase. Conventionally, 10-50 wt% Pt is supported on carbon, but as the non-carbon catalyst support materials have different densities, similar mass ratios of catalyst to support will not result in directly comparable performances. It is recommended that the ratio of Pt surface area to the support surface area should be similar when comparing Pt supported on carbon to Pt supported on a non-carbon support. A normalization approach was investigated in this work, and the ORR performance of 40wt.%Pt/C was found to be similar to that of 10wt.%Pt/Nb-TiO2. Fuel cell performance tests showed significantly higher stability of Pt on Nb

  1. ACTIVE CATHODES FOR SUPER-HIGH POWER DENSITY SOLID OXIDE FUEL CELLS THROUGH SPACE CHARGE EFFECTS

    SciTech Connect

    Anil V. Virkar

    2003-11-03

    This report summarizes the work done during the third quarter of the project. Effort was directed in two areas: (1) Further development of the model on the role of connectivity on ionic conductivity of porous bodies, including the role of grain boundaries, and its relationship to cathode polarization. Included indirectly through the grain boundary effect is the effect of space charge. (2) Synthesis of LSC + SDC composite cathode powders by combustion synthesis. (3) Fabrication and testing of anode-supported single cells made using synthesized LSC + ScDC composite cathodes.

  2. Calcium Ion Flow Permeates Cells through SOCs to Promote Cathode-Directed Galvanotaxis.

    PubMed

    Guo, Liang; Xu, Chunyan; Li, Dong; Zheng, Xiulan; Tang, Jiebing; Bu, Jingyi; Sun, Hui; Yang, Zhengkai; Sun, Wenjing; Yu, Xiaoguang

    2015-01-01

    Sensing and responding to endogenous electrical fields are important abilities for cells engaged in processes such as embryogenesis, regeneration and wound healing. Many types of cultured cells have been induced to migrate directionally within electrical fields in vitro using a process known as galvanotaxis. The underlying mechanism by which cells sense electrical fields is unknown. In this study, we assembled a polydimethylsiloxane (PDMS) galvanotaxis system and found that mouse fibroblasts and human prostate cancer PC3 cells migrated to the cathode. By comparing the effects of a pulsed direct current, a constant direct current and an anion-exchange membrane on the directed migration of mouse fibroblasts, we found that these cells responded to the ionic flow in the electrical fields. Taken together, the observed effects of the calcium content of the medium, the function of the store-operated calcium channels (SOCs) and the intracellular calcium content on galvanotaxis indicated that calcium ionic flow from the anode to the cathode within the culture medium permeated the cells through SOCs at the drift velocity, promoting migration toward the cathode. The RTK-PI3K pathway was involved in this process, but the ROCK and MAPK pathways were not. PC3 cells and mouse fibroblasts utilized the same mechanism of galvanotaxis. Together, these results indicated that the signaling pathway responsible for cathode-directed cellular galvanotaxis involved calcium ionic flow from the anode to the cathode within the culture medium, which permeated the cells through SOCs, causing cytoskeletal reorganization via PI3K signaling. PMID:26447479

  3. Calcium Ion Flow Permeates Cells through SOCs to Promote Cathode-Directed Galvanotaxis

    PubMed Central

    Guo, Liang; Xu, Chunyan; Li, Dong; Zheng, Xiulan; Tang, Jiebing; Bu, Jingyi; Sun, Hui; Yang, Zhengkai; Sun, Wenjing; Yu, Xiaoguang

    2015-01-01

    Sensing and responding to endogenous electrical fields are important abilities for cells engaged in processes such as embryogenesis, regeneration and wound healing. Many types of cultured cells have been induced to migrate directionally within electrical fields in vitro using a process known as galvanotaxis. The underlying mechanism by which cells sense electrical fields is unknown. In this study, we assembled a polydimethylsiloxane (PDMS) galvanotaxis system and found that mouse fibroblasts and human prostate cancer PC3 cells migrated to the cathode. By comparing the effects of a pulsed direct current, a constant direct current and an anion-exchange membrane on the directed migration of mouse fibroblasts, we found that these cells responded to the ionic flow in the electrical fields. Taken together, the observed effects of the calcium content of the medium, the function of the store-operated calcium channels (SOCs) and the intracellular calcium content on galvanotaxis indicated that calcium ionic flow from the anode to the cathode within the culture medium permeated the cells through SOCs at the drift velocity, promoting migration toward the cathode. The RTK-PI3K pathway was involved in this process, but the ROCK and MAPK pathways were not. PC3 cells and mouse fibroblasts utilized the same mechanism of galvanotaxis. Together, these results indicated that the signaling pathway responsible for cathode-directed cellular galvanotaxis involved calcium ionic flow from the anode to the cathode within the culture medium, which permeated the cells through SOCs, causing cytoskeletal reorganization via PI3K signaling. PMID:26447479

  4. 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.

  5. DIRECT METHANOL FUEL CELLS AT REDUCED CATALYST LOADINGS

    SciTech Connect

    P. ZELENAY; F. GUYON; SM. GOTTESFELD

    2001-05-01

    We focus in this paper on the reduction of catalyst loading in direct methanol fuel cells currently under development at Los Alamos National Laboratory. Based on single-cell DMFC testing, we discuss performance vs. catalyst loading trade-offs and demonstrate optimization of the anode performance. We also show test data for a short five-cell DMFC stack with the average total platinum loading of 0.53 mg cm{sup {minus}2} and compare performance of this stack with the performance of a single direct methanol fuel cell using similar total amount of precious metal.

  6. Stainless steel mesh supported nitrogen-doped carbon nanofibers for binder-free cathode in microbial fuel cells.

    PubMed

    Chen, Shuiliang; Chen, Yu; He, Guanghua; He, Shuijian; Schröder, Uwe; Hou, Haoqing

    2012-04-15

    In this communication, we report a binder-free oxygen reduction cathode for microbial fuel cells. The binder-free cathode is prepared by growth of nitrogen-doped carbon nanofibers (NCNFs) on stainless steel mesh (SSM) via simple pyrolysis of pyridine. The interaction force between NCNFs and SSM surface is very strong which is able to tolerate water flush. The NCNFs/SSM cathode shows high and stable electrocatalytic activity for oxygen reduction reaction, which is comparable to that of Pt/SSM and ferricyanide cathode. This study proposes a promising low-cost binder-free cathode for microbial fuel cells. PMID:22336437

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

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

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

  8. Impact of the Usage of a Slotted Cathode Carbon Block on Thermoelectric Field in an Aluminum Reduction Cell

    NASA Astrophysics Data System (ADS)

    Tao, Wenju; Li, Tuofu; Wang, Zhaowen; Gao, Bingliang; Shi, Zhongning; Hu, Xianwei; Cui, Jianzhong

    2015-05-01

    The horizontal current in a metal pad of an aluminum reduction cell is critical because of its effect on the fluctuation of the metal pad. In this study, a novel cathode with a slotted cathode carbon block was proposed to decrease the horizontal current. The effects of the slotted cathode carbon block on the horizontal and vertical currents in the metal pad, cathode voltage, and temperature distribution in the cathode were calculated using the finite-element method. The results show that the slotted cathode carbon has great potential to decrease the horizontal current. When the length of slot b equals 400 mm, the maximum horizontal current density decreased by 50.4%. However, the cathode voltage in the cathode with the slotted cathode carbon was ~43 mV higher than that in a conventional cell, and the temperature in the slotted cathode carbon was slightly higher than that in a conventional carbon cell. Moreover, with increasing length of slot b, the maximum horizontal and vertical currents in the metal pad moved toward the cell center. The result of this study may provide the database in understanding the effect of the slotted cathode carbon on cell.

  9. Direct methanol feed fuel cell with reduced catalyst loading

    NASA Technical Reports Server (NTRS)

    Kindler, Andrew (Inventor)

    1999-01-01

    Improvements to direct feed methanol fuel cells include new protocols for component formation. Catalyst-water repellent material is applied in formation of electrodes and sintered before application of ionomer. A membrane used in formation of an electrode assembly is specially pre-treated to improve bonding between catalyst and membrane. The improved electrode and the pre-treated membrane are assembled into a membrane electrode assembly.

  10. Long-term testing and evaluation of cathode components in a commercial aluminum cell

    SciTech Connect

    Gee, J.T.; Tucker, K.W; Joo, L.A.; Stewart, D.V.; Alcorn, T.; Tabereaux, A.

    1989-08-01

    Since 1886, essentially all primary aluminum has been produced in Hall-Heroult electrolytic cells which electrochemically reduce alumina to the metal in an energy/capital intensive process. Nearly five per cent of the electrical energy generated in the United States is consumed in this Hall-Heroult process, at the rate of 6--8 kwh/lb of aluminum produced. It has been in the aluminum industry's interest for the past several decades to utilize titanium diboride in some capacity as the cell cathode, either with conventional consumable carbon anodes or ultimately with nonconsumable, inert anodes. Eventual achievement of either or both of these goals will represent a technological breakthrough and make possible a significant reduction in the energy requirement to produce aluminum. The overall objective and achievement of this program was to better define the technical and economic viability of graphite-containing titanium diboride materials in low-cost shapes for use as cathodes in aluminum electrolytic cells as a precursor to subsequent demonstration and commercial application. Included are mathematical models for the prediction of cost-reducing cathode shapes, optimizing ratios of electrode areas, voltage reduction, and the effect on current efficiency from reduced anode-cathode distance. As part of the program, cathode shapes were produced using proprietary material processing technologies. Long-term commercial and medium-term pilot cell operations for data acquisition and cathode longevity determinations were completed, as were analyses of as-fabricated and as-tested cathodes, development of possible failure mechanisms, development of cathode holder/anode stops and an assessment of energy savings and technical/economic viability.

  11. Study of azo dye decolorization and determination of cathode microorganism profile in air-cathode microbial fuel cells.

    PubMed

    Kumru, Mert; Eren, Hilal; Catal, Tunc; Bermek, Hakan; Akarsubaşi, Alper Tunga

    2012-09-01

    Five textile azo dyes, as part of an artificial mixture, were treated in single-chamber air-cathode microbial fuel cells while simultaneously utilizing acetate for electricity production. Remazol Black, Remazol Brilliant Blue, Remazol Turquoise Blue, Reactive Yellow and Reactive Red at concentrations of 40 or 80 mg L(-1) were decolorized to a similar extent, at averages of 78, 95, 53, 93 and 74%, respectively, in 24 hours. During the process of decolorization, electricity generation from acetate oxidation continued. Power densities obtained in the presence of textile dyes ranged from 347 to 521 mW m(-2) at the current density range of 0.071 - 0.086 mA cm(-2). Microbial community analyses of cathode biofilm exhibited dynamic changes in abundant species following dye decolorization. Upon the addition of the first dye, a major change (63%) in microbial diversity was observed; however, subsequent addition of other dyes did not affect the community profile significantly. Actinobacteria, Aquamicrobium, Mesorhizobium, Ochrobactrum, Thauera, Paracoccus, Achromobacter and Chelatacoccus affiliated phylotypes were the major phylotypes detected. Our results demonstrate that microbial fuel cells could be a promising alternative for treatment of textile wastewaters and an active bacterial community can rapidly be established for simultaneous azo dye decolorization and sustainable electricity generation. PMID:23240212

  12. Novel strategy to mitigate cathode catalyst degradation during air/air startup cycling via the atmospheric resistive switching mechanism of a hydrogen anode with a platinum catalyst supported on tantalum-doped titanium dioxide

    NASA Astrophysics Data System (ADS)

    Shintani, Haruhiko; Kojima, Yuya; Kakinuma, Katsuyoshi; Watanabe, Masahiro; Uchida, Makoto

    2015-10-01

    We propose a new strategy for alleviating the reverse current phenomenon using a unique "atmospheric resistive switching mechanism" (ARSM) of a metal oxide semiconductor support, such that the electrical resistivity changes depending on the gas atmosphere. The membrane-electrode assembly (MEA) using Ta-doped TiO2-supported platinum (Pt/Ta-TiO2) as the anode catalyst showed approximately one order of magnitude greater resistance in air than in hydrogen. The overpotential of the hydrogen oxidation reaction was negligible up to at least 1.5 A cm-2. The losses of electrochemically active surface area and carbon corrosion of the cathode catalyst during air/air startup cycling were significantly suppressed by the use of the Pt/Ta-TiO2 anode. The decrease in the degradation is attributed to a reduction of the reverse current due to a low oxygen reduction reaction rate at the anode, which showed high resistivity in air. These results demonstrate the effectiveness of the ARSM in mitigating cathode catalyst degradation during air/air startup cycling.

  13. Hydrogen production in single chamber microbial electrolysis cells with stainless steel fiber felt cathodes

    NASA Astrophysics Data System (ADS)

    Su, Min; Wei, Liling; Qiu, Zhaozheng; Wang, Gang; Shen, Jianquan

    2016-01-01

    Microbial electrolysis cell (MEC) is a promising technology for sustainable production of hydrogen from biodegradable carbon sources. Employing a low-cost and high efficient cathode to replace platinum catalyzed cathode (Pt/C) for hydrogen generation is a challenge for commercialization of MEC. Here we show that a 3D macroporous stainless steel fiber felt (SSFF) with high electrochemical active surface area has an excellent catalytic activity for hydrogen generation, which is comparable to Pt/C cathode and superior to stainless steel mesh (SSM) cathode in the single-chamber MEC. The SSFF cathode (mean filter rating 100 μm) produces hydrogen at a rate of 3.66 ± 0.43 m3 H2 m-3d-1 (current density of 17.29 ± 1.68 A m-2), with a hydrogen recovery of 76.37 ± 15.04% and overall energy efficiency of 79.61 ± 13.07% at an applied voltage of 0.9 V. The performance of SSFF cathode improves over time due to a decrease in overpotential which caused by corrosion. These results demonstrate that SSFF can be a promising alternative for Pt catalytic cathode in MEC for hydrogen production.

  14. Improvement of microbial fuel cell cathodes using cost-effective polyvinylidene fluoride

    NASA Astrophysics Data System (ADS)

    Qiu, Zhaozheng; Su, Min; Wei, Liling; Han, Hongliang; Jia, Qibo; Shen, Jianquan

    2015-01-01

    In this study polyvinylidene fluoride (PVDF) is investigated as an alternative to polytetrafluoroethylene (PTFE) for air-cathode diffusion layers (DLs) in microbial fuel cells (MFCs) for the improvement of MFC power generation. It is found that the cathode fabricated with PVDF achieves a higher maximum power density (MPD) than a PTFE cathode. Successive PVDF or PVDF/carbon black DLs are applied on the base layers in order to optimize cathode performance. The results show significant improvements in such performances as the coulombic efficiency (CE), MPD, and water loss. In electrochemical tests, the cathode coated with four PVDF DLs has the largest current response at a given applied potential, yielding the highest MPD of 0.123 mW cm-2 (normalized to the projected cathode surface area) and largest CE (10.7%) in the MFC test. Carbon black is added to the DLs in order to test its effect on the MFC power generation. Cathodes made from pure PVDF DLs perform better than those containing PVDF/carbon black DLs in electrochemical and MFC tests. In addition, a smaller MFC (28 mL) produces a much higher MPD than a larger MFC (700 mL), resulting in an increase in the CE.

  15. High performance polymer solar cells with as-prepared zirconium acetylacetonate film as cathode buffer layer.

    PubMed

    Tan, Zhan'ao; Li, Shusheng; Wang, Fuzhi; Qian, Deping; Lin, Jun; Hou, Jianhui; Li, Yongfang

    2014-01-01

    Low-work-function active metals are commonly used as cathode in polymer solar cells (PSCs), but sensitivity of the active metals towards moisture and oxygen results in poor stability of the devices. Therefore, solution-proceessable and stable cathode buffer layer is of great importance for the application of PSCs. Here we demonstrate high performance PSCs by employing as-prepared zirconium acetylacetonate (a-ZrAcac) film spin-cast from its ethanol solution as cathode buffer layer. The PSCs based on a low bandgap polymer PBDTBDD as donor and PC60BM as acceptor with a-ZrAcac/Al cathode demonstrated an average power conversion efficiency (PCE) of 8.75% which is significantly improved than that of the devices with traditional Ca/Al cathode. The improved photovoltaic performance is benefitted from the decreased series resistance and enhanced light harvest of the PSCs with the a-ZrAcac/Al cathode. The results indicate that a-ZrAcac is a promising high performance cathode buffer layer for fabricating large area flexible PSCs. PMID:24732976

  16. Silver electrodeposition on the activated carbon air cathode for performance improvement in microbial fuel cells

    NASA Astrophysics Data System (ADS)

    Pu, Liangtao; Li, Kexun; Chen, Zhihao; Zhang, Peng; Zhang, Xi; Fu, Zhou

    2014-12-01

    The present work was to study silver electrodeposition on the activated carbon (AC) air cathode for performance improvement in microbial fuel cells (MFCs). The treated cathodes were proved to be effective to enhance the performance of MFCs. The maximum power density of MFC with silver electrodeposition time of 50 s (Ag-50) cathode was 1080 ± 60 mW m-2, 69% higher than the bare AC air cathode. X-ray photoelectron spectroscopy (XPS) results showed that zero-valent, monovalent and divalent silver were present to transform mutually, which illustrated that the oxygen reduction reaction (ORR) at the cathode took place through four-electron pathway. From electrochemical impedance spectroscopy (EIS) analysis, the electrodeposition method made the total resistance of the electrodes largely reduced. Meanwhile the deposited silver had no toxic effects on anode culture but inhibited the biofilm growth of the cathodes. This kind of antimicrobial efficient cathode, prepared with a simple, fast and economical method, was of good benefit to the performance improvement of MFCs.

  17. Carbon corrosion of proton exchange membrane fuel cell catalyst layers studied by scanning transmission X-ray microscopy

    NASA Astrophysics Data System (ADS)

    Hitchcock, Adam P.; Berejnov, Viatcheslav; Lee, Vincent; West, Marcia; Colbow, Vesna; Dutta, Monica; Wessel, Silvia

    2014-11-01

    Scanning Transmission X-ray Microscopy (STXM) at the C 1s, F 1s and S 2p edges has been used to investigate degradation of proton exchange membrane fuel cell (PEM-FC) membrane electrode assemblies (MEA) subjected to accelerated testing protocols. Quantitative chemical maps of the catalyst, carbon support and ionomer in the cathode layer are reported for beginning-of-test (BOT), and end-of-test (EOT) samples for two types of carbon support, low surface area carbon (LSAC) and medium surface area carbon (MSAC), that were exposed to accelerated stress testing with upper potentials (UPL) of 1.0, 1.2, and 1.3 V. The results are compared in order to characterize catalyst layer degradation in terms of the amounts and spatial distributions of these species. Pt agglomeration, Pt migration and corrosion of the carbon support are all visualized, and contribute to differing degrees in these samples. It is found that there is formation of a distinct Pt-in-membrane (PTIM) band for all EOT samples. The cathode thickness shrinks due to loss of the carbon support for all MSAC samples that were exposed to the different upper potentials, but only for the most aggressive testing protocol for the LSAC support. The amount of ionomer per unit volume significantly increases indicating it is being concentrated in the cathode as the carbon corrosion takes place. S 2p spectra and mapping of the cathode catalyst layer indicates there are still sulfonate groups present, even in the most damaged material.

  18. Membrane patterned by pulsed laser micromachining for proton exchange membrane fuel cell with sputtered ultra-low catalyst loadings

    NASA Astrophysics Data System (ADS)

    Cuynet, S.; Caillard, A.; Kaya-Boussougou, S.; Lecas, T.; Semmar, N.; Bigarré, J.; Buvat, P.; Brault, P.

    2015-12-01

    Proton exchange membranes were nano- and micro-patterned on their cathode side by pressing them against stainless steel molds previously irradiated by a Ti:Sapphire femtosecond laser. The membranes were associated to ultra-low loaded thin catalytic layers (25 μgPt cm-2) prepared by plasma magnetron sputtering. The Pt catalyst was sputtered either on the membrane or on the porous electrode. The fuel cell performance in dry conditions were found to be highly dependent on the morphology of the membrane surface. When nanometric ripples covered by a Pt catalyst were introduced on the surface of the membrane, the fuel cell outperformed the conventional one with a flat membrane. By combining nano- and micro-patterns (nanometric ripples and 11-24 μm deep craters), the performance of the cells was clearly enhanced. The maximum power density achieved by the fuel cell was multiplied by a factor of 3.6 (at 50 °C and 3 bar): 438 mW cm-2 vs 122 mW cm-2. This improvement is due to high catalyst utilization with a high membrane conductivity. When Pt is sputtered on the porous electrode (and not on the membrane), the contribution of the patterned membrane to the fuel cell efficiency was less significant, except in the presence of nanometric ripples. This result suggests that the patterning of the membrane must be consistent with the way the catalyst is synthesized, on the membrane or on the porous electrode.

  19. Simulation of Magnetohydrodynamic Multiphase Flow Phenomena and Interface Fluctuation in Aluminum Electrolytic Cell with Innovative Cathode

    NASA Astrophysics Data System (ADS)

    Wang, Qiang; Li, Baokuan; He, Zhu; Feng, Naixiang

    2013-12-01

    A three-dimensional (3D) transient mathematical model has been developed to understand the effect of innovative cathode on molten cryolite (bath)/molten aluminum (metal) interface fluctuation as well as energy-saving mechanism in aluminum electrolytic cell with innovative cathode. Based on the finite element method, the steady charge conservation law, Ohm's law, and steady-state Maxwell's equations were solved in order to investigate electric current field, magnetic field, and electromagnetic force (EMF) field. Then, an inhomogeneous multiphase flow model of three phases including bath, metal, and gas bubbles, based on the finite volume method, was implemented using the Euler/Euler approach to investigate melt motion and bath/metal interface fluctuation. EMF was incorporated into the momentum equations of bath and metal as a source term. Additionally, the interphase drag force was employed to consider different phase interactions. Thus, present work owns three main features: (1) magnetohydrodynamic multiphase flow are demonstrated in detail both in aluminum electrolytic cell with traditional cathode and innovative cathode; (2) bath/metal interface fluctuation due to different driving forces of gas bubbles, EMF, and the combined effect of the two driving forces is investigated, which is critical to the energy saving; and (3) the effect of innovative cathode on melt flow and motion of gas bubbles. A good agreement between the predicated results and measurement is obtained. The velocity difference leading to the melt oscillation decreases due to more uniform flow field. The average velocity of metal in the cell with innovative cathode decreases by approximately 33.98 pct. The gas bubbles in the cell with innovative cathode releases more quickly under the effect of protrusion on the cathode. The average bubble release frequency increases from 1.1 to 1.98 Hz. Hence, the voltage drop caused by gas bubbles would decrease significantly. In addition, the two large vortices

  20. MoO3 Cathodes for High-Temperature Lithium Thin-Film Cells

    NASA Technical Reports Server (NTRS)

    West, William; Whitacre, Jay

    2007-01-01

    MoO3 has shown promise as a cathode material that can extend the upper limit of operating temperature of rechargeable lithium thin-film electrochemical cells. Cells of this type are undergoing development for use as energy sources in cellular telephones, wireless medical sensors, and other, similarly sized portable electronic products. The LiCoO2 and LiMn2O4 cathodes heretofore used in these cells exhibit outstanding cycle lives (of the order of hundreds of thousands of cycles) at room temperature, but operation at higher temperatures reduces their cycle lives substantially: for example, at a temperature of 150 C, cells containing LiCoO2 cathodes lose half their capacities in 100 charge/discharge cycles. The superiority of MoO3 as a cathode material was demonstrated in experiments on lithium thin-film cells fabricated on glass slides. Each cell included a layer of Ti (for adhesion to the glass slide), a patterned layer of Pt that served as a cathode current collector, a cathode layer of MoO3, a solid electrolyte layer of Li3.3 PO3.8 N0.22 ("LiPON"), and an anode layer of Li. All the layers were deposited by magnetron sputtering except for the Li layer, which was deposited by thermal evaporation. These cells, along with similar ones containing LiCoO2 cathodes, were subjected to several tests, including measurements of specific capacity in charge/discharge cycling at a temperature of 150 C. The results of these measurements, plotted in the figure, showed that whereas specific capacity of the cells containing LiCoO2 cathodes faded to about half its initial value after only 100 cycles, the specific capacity of the cells containing the MoO3 cathodes faded only slightly during the first few hundred cycles and thereafter not only recovered to its initial value but continued to increase up to at least 5,500 cycles.

  1. Cell performance of ultra-thin polymer-cathode cell systems. Part 2. Cation intercalating composite polymer cathode. Technical report, 1 January 1989-1 March 1990

    SciTech Connect

    Naoi, K.; Smyrl, W.H.; Owens, B.B.

    1990-03-15

    Theoretical specific energy and power densities for thin film Li/LE or SPE/CP cell systems were calculated by modeling a bipolar-design polymer cathode rechargeable cell with hardware where LE, SPE and CP represent the liquid electrolyte (2M LiClO4(PC)), solid polymer electrolyte (PEO(8)LiX) and the conductive polymer(polypyrrole). The cell performance is obtained for a cation-intercalating PPy-PVS composite film which is composed of polypyrrole(PPy) into which has been incorporated the polymer anion, polyvinylsolfonate(PVS) during deposition. The energy and power densities are estimated as a function of cathode thickness (1 to 100,000 micron), active cell area (1 to 10,000 sq cm) and the number of bipolar units(1 to 100). Compared to the anion-consuming polymer cathode system, significant enhancement of specific energy was achieved. The theoretical specific energy amounts to ca. 290 Wh/kg (bare cell) and ca. 209 Wh/kg for a bipolar Li/LE or SPE/PPy-PVS cell system (with hardware).

  2. SOLID OXIDE FUEL CELL CATHODES: Polarization Mechanisms and Modeling of the Electrochemical Performance

    NASA Astrophysics Data System (ADS)

    Fleig, Jurgen

    2003-08-01

    Several recent experimental and numerical investigations have contributed to the improved understanding of the electrochemical mechanisms taking place at solid oxide fuel cell (SOFC) cathodes and yielded valuable information on the relationships between alterable parameters (geometry/material) and the cathodic polarization resistance. Efforts to reduce the polarization resistance in SOFCs can benefit from these results, and some important aspects of the corresponding studies are reviewed. Experimental results, particularly measurements using geometrically well-defined Sr-doped LaMnO3 (LSM) cathodes, are discussed. In regard to simulations, the different levels of sophistication used in SOFC electrode modeling studies are summarized and compared. Exemplary simulations of mixed conducting cathodes that show the capabilities and limits of different modeling levels are described.

  3. Endurance test on a single cell of a novel cathode material for MCFC

    NASA Astrophysics Data System (ADS)

    Soler, J.; González, T.; Escudero, M. J.; Rodrigo, T.; Daza, L.

    The molten carbonate fuel cell (MCFC) is expected to be an efficient device for the conversion of chemical energy in the near future. However, one of the major limits to the lifetime is the dissolution of the nickel oxide cathode in the electrolyte. This problem can be overcome by the addition of new compounds to the nickel oxide. In this way, the performance and the endurance of a new Ni-Ce cathode for MCFC has been tested and the results compared to a commercial nickel cathode. The polarisation curves were measured in order to check the degradation of the cell performance with time. The results showed a better performance with the novel cathode material (136 mW/cm 2 at 200 mA/cm 2 during 2100 h) than the commercial one (the voltage decreased from 120 to 108 mW/cm 2 at 150 mA/cm 2 in 1000 h). The better performance of Ni-Ce cathode with respect to the Ni one can be attributed to the good effect of cerium in the cathode. The change in the nickel crystalline structure reduces the dissolution of nickel in the electrolyte and implies a greater endurance of the cell. The current-voltage curves were measured and showed the same trend for both cells. Postmortem analyses were done in order to characterise the cells. As a conclusion, the addition of cerium can be beneficial to overcome the dissolution of the nickel cathode in the electrolyte, which is considered one of the major limits to the lifetime of a MCFC.

  4. Non-isothermal electrochemical model for lithium-ion cells with composite cathodes

    NASA Astrophysics Data System (ADS)

    Basu, Suman; Patil, Rajkumar S.; Ramachandran, Sanoop; Hariharan, Krishnan S.; Kolake, Subramanya Mayya; Song, Taewon; Oh, Dukjin; Yeo, Taejung; Doo, Seokgwang

    2015-06-01

    Transition metal oxide cathodes for Li-ion batteries offer high energy density and high voltage. Composites of these materials have shown excellent life expectancy and improved thermal performance. In the present work, a comprehensive non-isothermal electrochemical model for a Lithium ion cell with a composite cathode is developed. The present work builds on lithium concentration-dependent diffusivity and thermal gradient of cathode potential, obtained from experiments. The model validation is performed for a wide range of temperature and discharge rates. Excellent agreement is found for high and room temperature with moderate success at low temperatures, which can be attributed to the low fidelity of material properties at low temperature. Although the cell operation is limited by electronic conductivity of NCA at room temperature, at low temperatures a shift in controlling process is seen, and operation is limited by electrolyte transport. At room temperature, the lithium transport in Cathode appears to be the main source of heat generation with entropic heat as the primary contributor at low discharge rates and ohmic heat at high discharge rates respectively. Improvement in electronic conductivity of the cathode is expected to improve the performance of these composite cathodes and pave way for its wider commercialization.

  5. Characterization and optimization of cathodic conditions for H2O2 synthesis in microbial electrochemical cells.

    PubMed

    Sim, Junyoung; An, Junyeong; Elbeshbishy, Elsayed; Ryu, Hodon; Lee, Hyung-Sool

    2015-11-01

    Cathode potential and O2 supply methods were investigated to improve H2O2 synthesis in an electrochemical cell, and optimal cathode conditions were applied for microbial electrochemical cells (MECs). Using aqueous O2 for the cathode significantly improved current density, but H2O2 conversion efficiency was negligible at 0.3-12%. Current density decreased for passive O2 diffusion to the cathode, but H2O2 conversion efficiency increased by 65%. An MEC equipped with a gas diffusion cathode was operated with acetate medium and domestic wastewater, which presented relatively high H2O2 conversion efficiency from 36% to 47%, although cathode overpotential was fluctuated. Due to different current densities, the maximum H2O2 production rate was 141 mg H2O2/L-h in the MEC fed with acetate medium, but it became low at 6 mg H2O2/L-h in the MEC fed with the wastewater. Our study clearly indicates that improving anodic current density and mitigating membrane fouling would be key parameters for large-scale H2O2-MECs. PMID:26141667

  6. The economics of inert anodes and wettable cathodes for aluminum reduction cells

    NASA Astrophysics Data System (ADS)

    Keniry, Jeff

    2001-05-01

    Estimating the impact of inert-anode and wettable-cathode technologies on smelter costs must be speculative because no such technologies have yet been commercialized. Even so, some broad conclusions can be drawn about the economic merit of inert anodes in retrofit and greenfield smelter scenarios. Study suggests that retrofitting inert anodes to existing prebake cells generates insufficient economic benefit to justify this objective. Drained cathode cells offer potential for energy savings coupled with increased production, provided that the cell life is greater than three years. Unlocking the potential value of both inert anode and wettable cathode materials will require their use in vertical electrode configurations, where the impact on operating costs and, particularly, capital costs, is expected to be significant. To be economically and technically viable, vertical electrode cells will require wear rates of less than approximately 5 mm per year on the inert electrode surfaces, much less than has so far been reported.

  7. Nitrogen-doped graphene-rich catalysts derived from heteroatom polymers for oxygen reduction in nonaqueous lithium-O2 battery cathodes.

    PubMed

    Wu, Gang; Mack, Nathan H; Gao, Wei; Ma, Shuguo; Zhong, Ruiqin; Han, Jiantao; Baldwin, Jon K; Zelenay, Piotr

    2012-11-27

    In this work, we present a synthesis approach for nitrogen-doped graphene-sheet-like nanostructures via the graphitization of a heteroatom polymer, in particular, polyaniline, under the catalysis of a cobalt species using multiwalled carbon nanotubes (MWNTs) as a supporting template. The graphene-rich composite catalysts (Co-N-MWNTs) exhibit substantially improved activity for oxygen reduction in nonaqueous lithium-ion electrolyte as compared to those of currently used carbon blacks and Pt/carbon catalysts, evidenced by both rotating disk electrode and Li-O(2) battery experiments. The synthesis-structure-activity correlations for the graphene nanostructures were explored by tuning their synthetic chemistry (support, nitrogen precursor, heating temperature, and transition metal type and content) to investigate how the resulting morphology and nitrogen-doping functionalities (e.g., pyridinic, pyrrolic, and quaternary) influence the catalyst activity. In particular, an optimal temperature for heat treatment during synthesis is critical to creating a high-surface-area catalyst with favorable nitrogen doping. The sole Co phase, Co(9)S(8), was present in the catalyst but plays a negligible role in ORR. Nevertheless, the addition of Co species in the synthesis is indispensable for achieving high activity, due to its effects on the final catalyst morphology and structure, including surface area, nitrogen doping, and graphene formation. This new route for the preparation of a nitrogen-doped graphene nanocomposite with carbon nanotube offers synthetic control of morphology and nitrogen functionality and shows promise for applications in nonaqueous oxygen reduction electrocatalysis for Li-O(2) battery cathodes. PMID:23036092

  8. Percolation in a Proton Exchange Membrane Fuel Cell Catalyst Layer

    SciTech Connect

    Stacy, Stephen; Allen, Jeffrey

    2012-07-01

    Water management in the catalyst layers of proton exchange membrane fuel cells (PEMFC) is confronted by two issues, flooding and dry out, both of which result in improper functioning of the fuel cell and lead to poor performance and degradation. At the present time, the data that has been reported about water percolation and wettability within a fuel cell catalyst layer is limited. A method and apparatus for measuring the percolation pressure in the catalyst layer has been developed based upon an experimental apparatus used to test water percolation in porous transport layers (PTL). The experimental setup uses a pseudo Hele-Shaw type testing where samples are compressed and a fluid is injected into the sample. Testing the samples gives percolation pressure plots which show trends in increasing percolation pressure with an increase in flow rate. A decrease in pressure was seen as percolation occurred in one sample, however the pressure only had a rising effect in the other sample.

  9. Platinum-free cathode for dye-sensitized solar cells using poly(3,4-ethylenedioxythiophene) (PEDOT) formed via oxidative molecular layer deposition.

    PubMed

    Kim, Do Han; Atanasov, Sarah E; Lemaire, Paul; Lee, Kyoungmi; Parsons, Gregory N

    2015-02-25

    Thin ∼ 20 nm conformal poly(3,4-ehylenedioxythiophene) (PEDOT) films are incorporated in highly conductive mesoporous indium tin oxide (m-ITO) by oxidative molecular layer deposition (oMLD). These three-dimensional catalytic/conductive networks are successfully employed as Pt-free cathodes for dye-sensitized solar cells (DSSCs) with open circuit voltage equivalent to Pt cathode devices. Thin and conformal PEDOT films on m-ITO by oMLD create high surface area and efficient electron transport paths to promote productive reduction reaction on the PEDOT film. Because of these two synergetic effects, PEDOT-coated m-ITO by oMLD shows power conversion efficiency, 7.18%, comparable to 7.26% of Pt, and higher than that of planar PEDOT coatings, which is 4.85%. Thus, PEDOT-coated m-ITO is an exceptional opportunity to compete with Pt catalysts for low-cost energy conversion devices. PMID:25668707

  10. Pt-free carbon-based fuel cell catalyst prepared from spherical polyimide for enhanced oxygen diffusion

    PubMed Central

    Nabae, Yuta; Nagata, Shinsuke; Hayakawa, Teruaki; Niwa, Hideharu; Harada, Yoshihisa; Oshima, Masaharu; Isoda, Ayano; Matsunaga, Atsushi; Tanaka, Kazuhisa; Aoki, Tsutomu

    2016-01-01

    The development of a non-precious metal (NPM) fuel cell catalyst is extremely important to achieve globalization of polymer electrolyte fuel cells due to the cost and scarcity of platinum. Here, we report on a NPM cathode catalyst prepared by the pyrolysis of spherical polyimide nanoparticles that contain small amounts of Fe additive. 60 nm diameter Fe-containing polyimide nanoparticles were successfully synthesized by the precipitation polymerization of pyromellitic acid dianhydride and 1,3,5-tris(4-aminophenyl)benzene with Fe(acac)3 (acac = acetylacetonate) as an additive. The particles were subsequently carbonized by multistep pyrolysis to obtain the NPM catalyst while retaining the small particle size. The catalyst has good performance and promising durability for fuel cell applications. The fuel cell performance under a 0.2 MPa air atmosphere at 80 °C of 1.0 A cm−2 at 0.46 V is especially remarkable and better than that previously reported. PMID:26987682

  11. Pt-free carbon-based fuel cell catalyst prepared from spherical polyimide for enhanced oxygen diffusion

    NASA Astrophysics Data System (ADS)

    Nabae, Yuta; Nagata, Shinsuke; Hayakawa, Teruaki; Niwa, Hideharu; Harada, Yoshihisa; Oshima, Masaharu; Isoda, Ayano; Matsunaga, Atsushi; Tanaka, Kazuhisa; Aoki, Tsutomu

    2016-03-01

    The development of a non-precious metal (NPM) fuel cell catalyst is extremely important to achieve globalization of polymer electrolyte fuel cells due to the cost and scarcity of platinum. Here, we report on a NPM cathode catalyst prepared by the pyrolysis of spherical polyimide nanoparticles that contain small amounts of Fe additive. 60 nm diameter Fe-containing polyimide nanoparticles were successfully synthesized by the precipitation polymerization of pyromellitic acid dianhydride and 1,3,5-tris(4-aminophenyl)benzene with Fe(acac)3 (acac = acetylacetonate) as an additive. The particles were subsequently carbonized by multistep pyrolysis to obtain the NPM catalyst while retaining the small particle size. The catalyst has good performance and promising durability for fuel cell applications. The fuel cell performance under a 0.2 MPa air atmosphere at 80 °C of 1.0 A cm‑2 at 0.46 V is especially remarkable and better than that previously reported.

  12. Pt-free carbon-based fuel cell catalyst prepared from spherical polyimide for enhanced oxygen diffusion.

    PubMed

    Nabae, Yuta; Nagata, Shinsuke; Hayakawa, Teruaki; Niwa, Hideharu; Harada, Yoshihisa; Oshima, Masaharu; Isoda, Ayano; Matsunaga, Atsushi; Tanaka, Kazuhisa; Aoki, Tsutomu

    2016-01-01

    The development of a non-precious metal (NPM) fuel cell catalyst is extremely important to achieve globalization of polymer electrolyte fuel cells due to the cost and scarcity of platinum. Here, we report on a NPM cathode catalyst prepared by the pyrolysis of spherical polyimide nanoparticles that contain small amounts of Fe additive. 60 nm diameter Fe-containing polyimide nanoparticles were successfully synthesized by the precipitation polymerization of pyromellitic acid dianhydride and 1,3,5-tris(4-aminophenyl)benzene with Fe(acac)3 (acac = acetylacetonate) as an additive. The particles were subsequently carbonized by multistep pyrolysis to obtain the NPM catalyst while retaining the small particle size. The catalyst has good performance and promising durability for fuel cell applications. The fuel cell performance under a 0.2 MPa air atmosphere at 80 °C of 1.0 A cm(-2) at 0.46 V is especially remarkable and better than that previously reported. PMID:26987682

  13. An intermediate-temperature solid oxide fuel cell with electrospun nanofiber cathode

    SciTech Connect

    Zhi, Mingjia; Lee, Shiwoo; Miller, Nicholas; Menzler, Norbert H.; Wu, Nianqiang

    2012-05-01

    Lanthanum strontium cobalt ferrite (LSCF) nanofibers have been fabricated by the electrospinning method and used as the cathode of an intermediate-temperature solid oxide fuel cell (SOFC) with yttria-stabilized zirconia (YSZ) electrolyte. The three-dimensional nanofiber network cathode has several advantages: (i) high porosity; (ii) high percolation; (iii) continuous pathway for charge transport; (iv) good thermal stability at the operating temperature; and (v) excellent scaffold for infiltration. The fuel cell with the monolithic LSCF nanofiber cathode exhibits a power density of 0.90 W cm{sup −2} at 1.9 A cm{sup −2} at 750 °C. The electrochemical performance of the fuel cell has been further improved by infiltration of 20 wt% of gadolinia-doped ceria (GDC) into the LSCF nanofiber cathode. The fuel cell with the LSCF–20% GDC composite cathode shows a power density of 1.07 W cm{sup −2} at 1.9 A cm{sup −2} at 750 °C. The results obtained show that one-dimensional nanostructures such as nanofibers hold great promise as electrode materials for intermediate-temperature SOFCs.

  14. Simulated coal-gas-fueled molten carbonate fuel cell development program. Topical report: Cathode compatibility tests

    SciTech Connect

    Johnson, W.H.

    1992-07-01

    In previous work, International Fuel Cells Corporation (EFC) found interactions between molten carbonate fuel cell cathode materials being considered as replacements for the presently used nickel oxide and matrix materials. Consequently, this work was conducted to screen additional new materials for mutual compatibility. As part of this program, experiments were performed to examine the compatibility of several candidate, alternative cathode materials with the standard lithium aluminate matrix material in the presence of electrolyte at cell potentials. Initial cathode candidates were materials lithium ferrite, yttrium iron garnet, lithium manganite and doped ceria which were developed by universities, national laboratories, or contractors to DOE, EPRI, or GRI. These investigations were conducted in laboratory scale experiments. None of the materials tested can directly replace nickel oxide or indicate greater stability of cell performance than afforded by nickel oxide. Specifically: (1) no further work on niobium doped ceria is warranted; (2) cobalt migration was found in the lithium ferrite cathode tested. This could possibly lead to shorting problems similiar to those encountered with nickel oxide; (3) Possible shorting problems may also exist with the proprietary dopant in YIG; (4) lithium ferrite and YIG cathode were not single phase materials. Assessment of the chemical stability, i.e., dopant loss, was severely impeded by dissolution of these second phases in the electrolyte; and (5) Magnesium doped lithium manganite warrants further work. Electrolytes should contain Mg ions to suppress dopant loss.

  15. DEVELOPMENT OF HIGH TEMPERATURE MEMBRANES AND IMPROVED CATHODE CATALYSTS; PROJECT PERIOD JANUARY 1, 2002 - DECEMBER 31, 2005

    SciTech Connect

    Lesia Protsailo

    2006-04-20

    Polymer Electrolyte Membranes (PEMs) currently available for fuel cell development work are limited to the temperature range of 60-80°C. For mass commercialization in the transportation arena, three important disadvantages that are linked with the relatively low operating temperature range need to be addressed. These three disadvantages are: (a) sluggish cathode kinetics, (b) CO poisoning at the anode and (c) inefficient thermal characteristics. All three of the above mentioned disadvantages could be solved by increasing the operating temperature range to 100-120°C. To understand the issues associated with high temperature PEMFCs operation, UTCFC has teamed with leading research groups that possess competencies in the field of polymer chemistry. The subcontractors on the program were investigating modified Nafion® and new non-Nafion® based, reinforced and non-reinforced membrane systems. Nafion® based PEMs rely on using high temperature inorganic solid conductor fillers like phosphotungstic acid. Hydrocarbon membrane systems are based on poly (arylene ether sulfone) polymers, PEEK, PAN, etc.

  16. Effect of chemically modified Vulcan XC-72R on the performance of air-breathing cathode in a single-chamber microbial fuel cell.

    PubMed

    Duteanu, N; Erable, B; Senthil Kumar, S M; Ghangrekar, M M; Scott, K

    2010-07-01

    The catalytic activity of modified carbon powder (Vulcan XC-72R) for oxygen reduction reaction (ORR) in an air-breathing cathode of a microbial fuel cell (MFC) has been investigated. Chemical modification was carried out by using various chemicals, namely 5% nitric acid, 0.2N phosphoric acid, 0.2N potassium hydroxide and 10% hydrogen peroxide. Electrochemical study was performed for ORR of these modified carbon materials in the buffer solution pH range of 6-7.5 in the anodic compartment. Although, these treatments influenced the surface properties of the carbon material, as evident from the SEM-EDX analysis, treatment with H(2)PO(4), KOH, and H(2)O(2) did not show significant activity during the electrochemical test. The HNO(3) treated Vulcan demonstrated significant ORR activity and when used in the single-chamber MFC cathode, current densities (1115mA/m(2), at 5.6mV) greater than those for a Pt-supported un-treated carbon cathode were achieved. However, the power density for the latter was higher. Such chemically modified carbon material can be a cheaper alternative for expensive platinum catalyst used in MFC cathode construction. PMID:20171090

  17. The addition of ortho-hexagon nano spinel Co3O4 to improve the performance of activated carbon air cathode microbial fuel cell.

    PubMed

    Ge, Baochao; Li, Kexun; Fu, Zhou; Pu, Liangtao; Zhang, Xi

    2015-11-01

    Commercial Co3O4 and ortho-hexagon spinel nano-Co3O4 (OHSNC) were doped in the AC at a different percentage (5%, 10% and 15%) to enhance the performance of microbial fuel cell (MFC). The maximum power density of MFC with 10% OHSNC doped cathode was 1500±14 mW m(-2), which was 97.36% and 41.24% higher than that with the bare AC air cathode and commercial Co3O4 respectively. The electrocatalytic behavior for their better performance was discussed in detail with the help of various structural and electrochemical techniques. The OHSNC was characterized via X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM). The results showed that the improved performance owed to the enhancement of both kinetics activity and the number of electron transfer in the ORR, and the internal resistance was largely reduced. Therefore, OHSNC was proved to be an excellent cathodic catalyst in AC air cathode MFC. PMID:26112347

  18. Cathode bubbles induced by moisture electrolysis in TiO2-x -based resistive switching cells

    NASA Astrophysics Data System (ADS)

    Yin, Qiaonan; Wei, Chunyang; Xia, Yidong; Xu, Bo; Yin, Jiang; Liu, Zhiguo

    2016-03-01

    H2 production has been predicted in some metal-insulator-metal resistive switching devices and similar structures, but experimentally has not yet been reported. Here we discovered cathode bubbles in Pt/TiO2-x /Pt unipolar resistive switching cells when electroforming is implemented in a humid environment. But then these bubbles are absent when cells are operated in an anhydrous environment. The focused ion beam technique was used to observe the deformation of the cell induced by bubbles. These bubbles are deduced to be filled with H2 generated at the cathode by the reduction of protons from adsorbed water. Reduced oxides containing abundant oxygen vacancies facilitate the dissociation of adsorbed water and supply sufficient protons diffusing towards the cathode.

  19. Comparative study on power generation of dual-cathode microbial fuel cell according to polarization methods.

    PubMed

    Lee, Kang-yu; Ryu, Wyan-seuk; Cho, Sung-il; Lim, Kyeong-ho

    2015-11-01

    Microbial fuel cells (MFCs) exist in various forms depending on the type of pollutant to be removed and the expected performance. Dual-cathode MFCs, with their simple structure, are capable of removing both organic matter and nitrogen. Moreover, various methods are available for the collection of polarization data, which can be used to calculate the maximum power density, an important factor of MFCs. Many researchers prefer the method of varying the external resistance in a single-cycle due to the short measurement time and high accuracy. This study compared power densities of dual-cathode MFCs in a single-cycle with values calculated over multi-cycles to determine the optimal polarization method. External resistance was varied from high to low and vice versa in the single-cycle, to calculate power density. External resistance was organized in descending order with initial start-up at open circuit voltage (OCV), and then it was organized in descending order again after the initial start-up at 1000 Ω. As a result, power density was underestimated at the anoxic cathode when the external resistance was varied from low to high, and overestimated at the aerobic cathode and anoxic cathode when external resistance at OCV was reduced following initial start-up. In calculating the power densities of dual-cathode MFCs, this paper recommends the method of gradually reducing the external resistance after initial start-up with high external resistance. PMID:26210028

  20. High-throughput screening of binary catalysts for oxygen electroreduction

    NASA Astrophysics Data System (ADS)

    Liu, Jing Hua; Jeon, Min Ku; Woo, Seong Ihl

    2006-01-01

    A series of Pt based and non-Pt catalysts for proton exchange membrane fuel cell (PEMFC) and direct methanol fuel cell (DMFC) have been evaluated towards oxygen reduction, by high-throughput optical screening. Fluorescein was first used as pH indicator for detecting pH change of the electrolyte in the vicinity of cathode caused by oxygen reduction. Arrays of catalyst spot comprised of binary catalysts and pure Pt were prepared by using robotic micro-dispenser. The analysis of fluorescence images has showed that some of Pt based catalysts including PtBi, PtCu, PtSe, PtTe and PtIr, as well as RuFe, as a non-Pt catalyst, exhibited higher activities and methanol tolerance than pure Pt. Moreover, acceptable stability of these catalysts at high potential in acid environment suits them to the requirements of cathode catalyst in PEMFC or DMFC.

  1. A fundamental study of chromium deposition on solid oxide fuel cell cathode materials

    NASA Astrophysics Data System (ADS)

    Tucker, Michael C.; Kurokawa, Hideto; Jacobson, Craig P.; De Jonghe, Lutgard C.; Visco, Steven J.

    Chromium contamination of metal oxides and SOFC cathode catalysts is studied in the range 700-1000 °C. Samples are exposed to a moist air atmosphere saturated with volatile Cr species in the presence and absence of direct contact between the sample and ferritic stainless steel powder. Chromium contamination of the samples is observed to occur via two separate pathways: surface diffusion from the stainless steel surface and vapor deposition from the atmosphere. Surface diffusion dominates in all cases. Surface diffusion is found to be a significant source of Cr contamination for LSM and LSCF at 700, 800, and 1000 °C. Vapor deposition of Cr onto LSCF was observed at each of these temperatures, but was not observed for LSM at 700 or 800 °C. Comparison of the behavior for LSM, LSCF, and single metal oxides suggests that Mn and Co, respectively, are responsible for the Cr contamination of these catalysts.

  2. Microbial fuel cell with an algae-assisted cathode: A preliminary assessment

    NASA Astrophysics Data System (ADS)

    González del Campo, Araceli; Cañizares, Pablo; Rodrigo, Manuel A.; Fernández, Francisco J.; Lobato, Justo

    2013-11-01

    A microbial fuel cell (MFC) with an algae-assisted cathode, i.e., a system where the oxygen required by the cathode is not provided by aeration but by the photosynthetic process of the algae (Chlorella vulgaris), has been studied. The cathode was illuminated for 12 h each day (from 8:00 h to 20:00 h). 25 days was necessary to achieve steady state conditions. The time evolution of dissolved oxygen and cell voltage were assessed over the course of each day. As expected, the dissolved oxygen values were not constant throughout the day, reaching maximum values between 14:00 h and 20:00 h when dark phase reactions began and the algae started to consume oxygen. Cell voltage (Rext 120 Ω) followed the same trend as the oxygen profile. The supply of CO2 in the cathode was also studied, and half an hour was enough time to get the system working properly. During the acclimation stage, power density increased up to 13.5 mW m-2 at steady state conditions. However, impedance analysis showed that polarization resistance was higher at the cathode than at the anode. Nevertheless, it can be concluded that the studied system is a feasible method to treat wastewater in a self-sustainable way.

  3. Pore Scale Modeling of the Reactive Transport of Chromium in the Cathode of a Solid Oxide Fuel Cell

    SciTech Connect

    Ryan, Emily M.; Tartakovsky, Alexandre M.; Recknagle, Kurtis P.; Khaleel, Mohammad A.; Amon, Cristina

    2011-01-01

    We present a pore scale model of a solid oxide fuel cell (SOFC) cathode. Volatile chromium species are known to migrate from the current collector of the SOFC into the cathode where over time they decrease the voltage output of the fuel cell. A pore scale model is used to investigate the reactive transport of chromium species in the cathode and to study the driving forces of chromium poisoning. A multi-scale modeling approach is proposed which uses a cell level model of the cathode, air channel and current collector to determine the boundary conditions for a pore scale model of a section of the cathode. The pore scale model uses a discrete representation of the cathode to explicitly model the surface reactions of oxygen and chromium with a cathode material. The pore scale model is used to study the reaction mechanisms of chromium by considering the effects of reaction rates, diffusion coefficients, chromium vaporization, and oxygen consumption on chromium’s deposition in the cathode. The study shows that chromium poisoning is most significantly affected by the chromium reaction rates in the cathode and that the reaction rates are a function of the local current density in the cathode.

  4. Effects of short-side-chain perfluorosulfonic acid ionomers as binders on the performance of low Pt loading fuel cell cathodes

    NASA Astrophysics Data System (ADS)

    Park, Young-Chul; Kakinuma, Katsuyoshi; Uchida, Hiroyuki; Watanabe, Masahiro; Uchida, Makoto

    2015-02-01

    We investigated the effects of short-side-chain (SSC) perfluorosulfonic acid ionomers on the electrochemical properties, fuel cell performance and ionomer distribution of a highly dispersed Pt/GCB catalyst with a low Pt loading, 0.05 mg cm-2. The SSC ionomers in the cathode catalyst layers (CLs) resulted in an improvement of the Pt utilization (UPt) and Pt effectiveness (EfPt) values compared with those for the conventional long-side-chain (LSC) ionomer. Furthermore, the SSC ionomers with high ion exchange capacity (IEC), e.g., SSC-1.43 and SSC-1.80 ionomers, exhibited significantly enhanced cell performance under low to medium relative humidity (RH) conditions. This result is ascribed to the higher proton conductivity of the SSC ionomers and more effective trapping of water that is produced during the oxygen reduction reaction (ORR) than those of the LSC ionomer. It was also found that the SSC ionomers showed better continuity and uniformity on the Pt and carbon particles than the LSC ionomer, which might have led to improvement of both the mass transport and the proton-conducting network in the CLs. The application of the SSC ionomers as binders demonstrated an increase of the performance at the low Pt loading fuel cell cathode over a wide range of humidity.

  5. Understanding and controlling nanoporosity formation for improving the stability of bimetallic fuel cell catalysts.

    PubMed

    Gan, Lin; Heggen, Marc; O'Malley, Rachel; Theobald, Brian; Strasser, Peter

    2013-03-13

    Nanoporosity is a frequently reported phenomenon in bimetallic particle ensembles used as electrocatalysts for the oxygen reduction reaction (ORR) in fuel cells. It is generally considered a favorable characteristic, because it increases the catalytically active surface area. However, the effect of nanoporosity on the intrinsic activity and stability of a nanoparticle electrocatalyst has remained unclear. Here, we present a facile atmosphere-controlled acid leaching technique to control the formation of nanoporosity in Pt-Ni bimetallic nanoparticles. By statistical analysis of particle size, composition, nanoporosity, and atomic-scale core-shell fine structures before and after electrochemical stability test, we uncover that nanoporosity formation in particles larger than ca. 10 nm is intrinsically tied to a drastic dissolution of Ni and, as a result of this, a rapid drop in intrinsic catalytic activity during ORR testing, translating into severe catalyst performance degradation. In contrast, O2-free acid leaching enabled the suppression of nanoporosity resulting in more solid core-shell particle architectures with thin Pt-enriched shells; surprisingly, such particles maintained high intrinsic activity and improved catalytic durability under otherwise identical ORR tests. On the basis of these findings, we suggest that catalytic stability could further improve by controlling the particle size below ca. 10 nm to avoid nanoporosity. Our findings provide an explanation for the degradation of bimetallic particle ensembles and show an easy to implement pathway toward more durable fuel cell cathode catalysts. PMID:23360425

  6. Studies on niobium triselenide cathode material for lithium rechargeable cells

    NASA Technical Reports Server (NTRS)

    Ratnakumar, B. V.; Ni, C. L.; Distefano, S.; Somoano, R. B.; Bankston, C. P.

    1988-01-01

    NbSe3 exhibits superior characteristics such as high capacity, high volumetric and gravimetric energy densities, and high discharge rate capability, as compared to other intercalating cathodes. This paper reports the preparation, characterization, and performance of NbSe3. Several electrochemical techniques, such as cyclic voltammetry, constant-current/constant-potential discharges, dc potentiodynamic scans, ac impedance, and ac voltammetry, have been used to give insight to the mechanisms of intercalation of three lithiums with NbSe3 and also into the rate determining process in the reduction of NbSe3.

  7. Electrochemical behavior of niobium triselenide cathode in lithium secondary cells

    NASA Technical Reports Server (NTRS)

    Ratnakumar, B. V.; Di Stefano, S.; Bankston, C. P.

    1988-01-01

    Niobium triselenide cathodes in Li ambient-temperature rechargeable batteries for space applications undergo a topotactic reaction, with three equivalents of Li at high positive potential furnishing high energy density. It also yields good electronic conductivity, a long life cycle, and high diffusivity for Li. An attempt is presently made to characterize the intercalation mechanism between Li and NbSe3 by means of an ac impedance study conducted at various charge stages in the process of SbSe3 reduction. An effort is also made to predict the charge state of NbSe3 nondestructively, on the basis of the impedance parameters.

  8. Proton conducting intermediate-temperature solid oxide fuel cells using new perovskite type cathodes

    NASA Astrophysics Data System (ADS)

    Li, Meiling; Ni, Meng; Su, Feng; Xia, Changrong

    2014-08-01

    Sr2Fe1.5Mo0.5O6-δ (SFM) is proposed as the electrodes for symmetric solid oxide fuel cells (SOFCs) based on oxygen-ion conducting electrolytes. In this work SFM is investigated as the cathodes for SOFCs with proton conducting BaZr0.1Ce0.7Y0.2O3-δ (BZCY) electrolyte. SFM is synthesized with a combined glycine and citric acid method and shows very good chemical compatibility with BZCY under 1100 °C. Anode-supported single cell (Ni-BZCY anode, BZCY electrolyte, and SFM-BZCY cathode) and symmetrical fuel cell (SFM-BZCY electrodes and BZCY electrolyte) are fabricated and their performances are measured. Impedance spectroscopy on symmetrical cell consisting of BZCY electrolyte and SFM-BZCY electrodes demonstrates low area-specific interfacial polarization resistance Rp, and the lowest Rp, 0.088 Ω cm2 is achieved at 800 °C when cathode is sintered at 900 °C for 2 h. The single fuel cell achieves 396 mW cm-2 at 800 °C in wet H2 (3 vol% H2O) at a co-sintering temperature of 1000 °C. This study demonstrates the potential of SFM-BZCY as a cathode material in proton-conducting intermediate-temperature solid oxide fuel cells.

  9. Modeling and validation of single-chamber microbial fuel cell cathode biofilm growth and response to oxidant gas composition

    DOE PAGESBeta

    Ou, Shiqi; Zhao, Yi; Aaron, Douglas S.; Regan, John M.; Mench, Matthew M.

    2016-08-15

    This work describes experiments and computational simulations to analyze single-chamber, air-cathode microbial fuel cell (MFC) performance and cathodic limitations in terms of current generation, power output, mass transport, biomass competition, and biofilm growth. Steady-state and transient cathode models were developed and experimentally validated. Two cathode gas mixtures were used to explore oxygen transport in the cathode: the MFCs exposed to a helium-oxygen mixture (heliox) produced higher current and power output than the group of MFCs exposed to air or a nitrogen-oxygen mixture (nitrox), indicating a dependence on gas-phase transport in the cathode. Multi-substance transport, biological reactions, and electrochemical reactions inmore » a multi-layer and multi-biomass cathode biofilm were also simulated in a transient model. The transient model described biofilm growth over 15 days while providing insight into mass transport and cathodic dissolved species concentration profiles during biofilm growth. Lastly, simulation results predict that the dissolved oxygen content and diffusion in the cathode are key parameters affecting the power output of the air-cathode MFC system, with greater oxygen content in the cathode resulting in increased power output and fully-matured biomass.« less

  10. An efficient approach to cathode operational parameters optimization for microbial fuel cell using response surface methodology

    PubMed Central

    2014-01-01

    Background In the recent study, optimum operational conditions of cathode compartment of microbial fuel cell were determined by using Response Surface Methodology (RSM) with a central composite design to maximize power density and COD removal. Methods The interactive effects of parameters such as, pH, buffer concentration and ionic strength on power density and COD removal were evaluated in two-chamber microbial batch-mode fuel cell. Results Power density and COD removal for optimal conditions (pH of 6.75, buffer concentration of 0.177 M and ionic strength of cathode chamber of 4.69 mM) improve by 17 and 5%, respectively, in comparison with normal conditions (pH of 7, buffer concentration of 0.1 M and ionic strength of 2.5 mM). Conclusions In conclusion, results verify that response surface methodology could successfully determine cathode chamber optimum operational conditions. PMID:24423039

  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. PMID:26606182

  12. Nd-nickelate solid oxide fuel cell cathode sensitivity to Cr and Si contamination

    NASA Astrophysics Data System (ADS)

    Andreas Schuler, J.; Lübbe, Henning; Hessler-Wyser, Aïcha; Van herle, Jan

    2012-09-01

    The stability of Nd-nickelate, considered as an alternative solid oxide fuel cell (SOFC) cathode material, was evaluated in this work on its tolerance towards contaminants. Symmetrical cells with Nd1.95NiO4+δ (NNO) electrodes sintered on gadolinia-doped ceria electrolyte supports were monitored over time-spans of 1000 h at 700 °C under polarization in an air-flux with deliberate chromium contamination. Impedance spectroscopy pointed out a polarization increase with time by the growth of the low frequency arc describing the electrode's oxygen reduction and incorporation processes. Post-test observations revealed polluted cathode regions with increasing amounts of Cr accumulations towards the electrolyte/cathode interface. Cr deposits were evidenced to surround active nickelate grain surfaces forming Nd-containing Cr oxides. In addition to exogenous Cr contamination, endogenous contamination was revealed. Silicon, present as impurity material in the raw NNO powder (introduced by milling during powder processing), reacts during sintering steps to form Nd-silicate phases, which decreases the active cathode surface. Nd-depletion of the nickelate, as a result of secondary phase formation with the contaminants Cr and Si (NdCrO4 and Nd4Si3O12), then triggers the thermally-induced decomposition of NNO into stoichiometric Nd2NiO4+δ and NiO. Summarized, the alternative Nd-nickelate cathode also suffers from degradation caused by pollutant species, like standard perovskites.

  13. Method to improve catalyst layer model for modelling proton exchange membrane fuel cell

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaoxian; Gao, Yuan; Ostadi, Hossein; Jiang, Kyle; Chen, Rui

    2015-09-01

    Correctly describing oxygen reduction within the cathode catalyst layer (CL) in modelling proton exchange membrane fuel cell is an important issue remaining unresolved. In this paper we show how to derive an agglomerate model for calculating oxygen reactions by describing dissolved oxygen in the agglomerates using two independent random processes. The first one is the probability that an oxygen molecule, which dissolves in the ionomer film on the agglomerate surface, moves into and then remains in the agglomerates; the second one is the probability of the molecule being consumed in reactions. The first probability depends on CL structure and can be directly calculated; the second one is derived by assuming that the oxygen reduction is first-order kinetic. It is found that the distribution functions of the first process can be fitted to a generalised gamma distribution function, which enables us to derive an analytical agglomerate model. We also expend the model to include oxygen dissolution in the ionomer film, and apply it to simulate cathode electrodes. The results reveal that the resistance to oxygen diffusion in ionomer film and agglomerate in modern CL is minor, and that the main potential loss is due to oxygen dissolution in the ionomer film.

  14. Analysis of the electrochemical characteristics of a direct methanol fuel cell based on a Pt-Ru/C anode catalyst

    SciTech Connect

    Arico, A.S.; Creti, P.; Mantegna, R.

    1996-12-31

    This paper deals with a vapour-feed direct methanol fuel cell (DMFC) based on a Nafion 117{reg_sign} solid polymer electrolyte. Pt-Ru/C and Pt/C catalysts were employed for methanol oxidation and oxygen reduction, respectively. Structure and surface chemistry of catalysts were investigated by X-ray powder diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Membrane/electrode assembly (M&E) was prepared by using a {open_quotes}paste process{close_quotes} method. Electrical power densities of about 150 mW cm{sup -2} were obtained at 95{degrees} C with Pt loadings of 0.8 and 0.5 mg cm{sup -2} at anode and cathode respectively.

  15. Noble metal/vanadium alloy catalyst and method for making

    SciTech Connect

    Jalan, V.M.

    1980-05-13

    A novel catalyst comprises an alloy of a noble metal and vanadium. The catalyst is particularly useful in an electrochemical cell cathode electrode. The method for making the alloy involves reacting a vanadium compound with sodium dithionite to form a sol of a finely dispersed vanadium sulfite complex, and then reacting noble metal particles with the complex in a reducing environment.

  16. Composite Cathode for High-Power Density Solid Oxide Fuel Cells

    SciTech Connect

    Ilwon Kim; Scott Barnett; Yi Jiang; Manoj Pillai; Nikkia McDonald; Dan Gostovic; Zhongryang Zhan; Jiang Liu

    2004-01-31

    Reduction of solid oxide fuel cell (SOFC) operating temperature will play a key role in reducing the stack cost by allowing the use of low-cost metallic interconnects and new approaches to sealing, while making applications such as transportation more feasible. Reported results for anode-supported SOFCs show that cathode polarization resistance is the primary barrier to achieving high power densities at operating temperatures of 700 C and lower. This project aims to identify and develop composite cathodes that could reduce SOFC operating temperatures below 700 C. This effort focuses on study and use of (La,Sr)(Co,Fe)O{sub 3} (LSCF) based composite cathodes, which have arguably the best potential to substantially improve on the currently-used, (La,Sr)MnO{sub 3}-Yttria-stabilized Zirconia. During this Phase I, it was successfully demonstrated that high performances can be achieved with LSCF/Gadolinium-Doped Ceria composite cathodes on Ni-based anode supported cells operating at 700 C or lower. We studied electrochemical reactions at LSCF/Yttria-stabilized Zirconia (YSZ) interfaces, and observed chemical reactions between LSCF and YSZ. By using ceria electrolytes or YSZ electrolytes with ceria diffusion barrier layers, the chemical reactions between LSCF and electrolytes were prevented under cathode firing conditions necessary for the optimal adhesion of the cathodes. The protection provided by ceria layer is expected to be adequate for stable long-term cathode performances, but more testing is needed to verify this. Using ceria-based barrier layers, high performance Ni-YSZ anode supported cells have been demonstrated with maximum power densities of 0.8W/cm2 at 700 C and 1.6W/cm{sup 2} at 800 C. Ni-SDC anode supported cells with SDC electrolytes yielded >1W/cm{sup 2} at 600 C. We speculate that the power output of Ni-YSZ anode supported cell at 700 C and lower, was limited by the quality of the Ceria and Ceria YSZ interface. Improvements in the low

  17. Metal chelate catalysts for fuel cells

    NASA Astrophysics Data System (ADS)

    Darby, R.; White, R.; Yamana, M.; Tsutsue, M.

    1981-07-01

    A variety of metal chelates were synthesized and evaluated for their activity as oxygen cathode electrocatalysts in strong acidic electrolytes. It was found that Cobalt tetraazaanulene (CoTAA) and iron phthalocyanine (FePc) exhibit the best activity of all the metal chelates synthesized, but have very limited stability. The proposed solution to this problem is the synthesis of polymeric forms of these chelates, with comparable active and considerably greater stability than the monomers. Three methods for stability testing were developed: (1) Potentiostatic, with periodic measurement of the current potential characteristic; (2) potentiostatic, with continuous monitoring of the current, and; (3) galvanostatic, with continuous monitoring of potential. Each method provides a good evaluation of activity versus time, and the method to be used depends upon the objective of the test. A polymeric form of Co(TAA) was synthesized by means of an acetylene terminated monomer, which in turn was made via a Co(TAA)Br2 intermediate. The activity of the polymer was found to be comparable to that of Co(TAA) monomer, and significantly greater than that of either the stacked or sheet polymeric forms of Cobalt tetraphenylporphrine (CoTPP) previously synthesized and tested.

  18. 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.

  19. Silver/iron oxide/graphitic carbon composites as bacteriostatic catalysts for enhancing oxygen reduction in microbial fuel cells

    NASA Astrophysics Data System (ADS)

    Ma, Ming; You, Shijie; Gong, Xiaobo; Dai, Ying; Zou, Jinlong; Fu, Honggang

    2015-06-01

    Biofilms from anode heterotrophic bacteria are inevitably formed over cathodic catalytic sites, limiting the performances of single-chamber microbial fuel cells (MFCs). Graphitic carbon (GC) - based nano silver/iron oxide (AgNPs/Fe3O4/GC) composites are prepared from waste pomelo skin and used as antibacterial oxygen reduction catalysts for MFCs. AgNPs and Fe3O4 are introduced in situ into the composites by one-step carbothermal reduction, enhancing their conductivity and catalytic activity. To investigate the effects of Fe species on the antibacterial and catalytic properties, AgNPs/Fe3O4/GC is washed with sulfuric acid (1 mol L-1) for 0.5 h, 1 h, and 5 h and marked as AgNPs/Fe3O4/GC-x (x = 0.5 h, 1 h and 5 h, respectively). A maximum power density of 1712 ± 35 mW m-2 is obtained by AgNPs/Fe3O4/GC-1 h, which declines by 4.12% after 17 cycles. Under catalysis of all AgNP-containing catalysts, oxygen reduction reaction (ORR) proceeds via the 4e- pathway, and no toxic effects to anode microorganisms result from inhibiting the cathodic biofilm overgrowth. With the exception of AgNPs/Fe3O4/GC-5 h, the AgNPs-containing composites exhibit remarkable power output and coulombic efficiency through lowering proton transfer resistance and air-cathode biofouling. This study provides a perspective for the practical application of MFCs using these efficient antibacterial ORR catalysts.

  20. Cathode and electrolyte materials for solid oxide fuel cells and ion transport membranes

    DOEpatents

    Jacobson, Allan J; Wang, Shuangyan; Kim, Gun Tae

    2014-01-28

    Novel cathode, electrolyte and oxygen separation materials are disclosed that operate at intermediate temperatures for use in solid oxide fuel cells and ion transport membranes based on oxides with perovskite related structures and an ordered arrangement of A site cations. The materials have significantly faster oxygen kinetics than in corresponding disordered perovskites.

  1. Hollow nanoparticle cathode materials for sodium electrochemical cells and batteries

    DOEpatents

    Shevchenko, Elena; Rajh, Tijana; Johnson, Christopher S.; Koo, Bonil

    2016-07-12

    A cathode comprises, in its discharged state, a layer of hollow .gamma.-Fe.sub.2O.sub.3 nanoparticles disposed between two layers of carbon nanotubes, and preferably including a metallic current collector in contact with one of the layers of carbon nanotubes. Individual particles of the hollow .gamma.-Fe.sub.2O.sub.3 nanoparticles comprise a crystalline shell of .gamma.-Fe.sub.2O.sub.3 including cation vacancies within the crystal structure of the shell (i.e., iron vacancies of anywhere between 3% to 90%, and preferably 44 to 77% of available octahedral iron sites). Sodium ions are intercalated within at least some of the cation vacancies within the crystalline shell of the hollow .gamma.-Fe.sub.2O.sub.3 nanoparticles.

  2. Copper cobalt spinel as a high performance cathode for intermediate temperature solid oxide fuel cells.

    PubMed

    Shao, Lin; Wang, Qi; Fan, Lishuang; Wang, Pengxiang; Zhang, Naiqing; Sun, Kening

    2016-06-30

    CuCo2O4 spinel prepared via an EDTA-citric acid process was studied as a candidate solid oxide fuel cell (SOFC) cathode material at intermediate temperatures (IT). CuCo2O4 cathodes were measured using thermal gravimetric analysis, X-ray diffraction and scanning electron microscopy. AC impedance spectroscopy and DC polarization measurements were used to study the electrode performance. The obtained value of the polarization resistances at 800 °C was 0.12 Ω cm(2) with a maximum power density of 972 mW cm(-2). PMID:27326915

  3. Chromium poisoning in (La,Sr)MnO3 cathode: Three-dimensional simulation of a solid oxide fuel cell

    NASA Astrophysics Data System (ADS)

    Miyoshi, Kota; Iwai, Hiroshi; Kishimoto, Masashi; Saito, Motohiro; Yoshida, Hideo

    2016-09-01

    A three-dimensional numerical model of a single solid oxide fuel cell (SOFC) considering chromium poisoning on the cathode side has been developed to investigate the evolution of the SOFC performance over long-term operation. The degradation model applied in the simulation describes the loss of the cathode electrochemical activity as a decrease in the active triple-phase boundary (TPB) length. The calculations are conducted for two types of cell: lanthanum strontium manganite (LSM)/yttria-stabilized zirconia (YSZ)/Ni-YSZ and LSM-YSZ/YSZ/Ni-YSZ. Their electrode microstructures are acquired by imaging with a focused ion beam scanning-electron microscope (FIB-SEM). The simulation results qualitatively reproduce the trends of chromium poisoning reported in the literature. It has been revealed that the performance degradation by chromium is primarily due to an increase in the cathode activation overpotential. In addition, in the LSM-YSZ composite cathode, TPBs in the vicinity of the cathode-electrolyte interface preferentially deteriorate, shifting the active reaction site towards the cathode surface. This also results in an increase in the cathode ohmic loss associated with oxide ion conduction through the YSZ phase. The effects of the cell temperature, the partial pressure of steam at the chromium source, the cathode microstructure, and the cathode thickness on chromium poisoning are also discussed.

  4. Phase field modeling of microstructure evolution of electrocatalyst-infiltrated solid oxide fuel cell cathodes

    NASA Astrophysics Data System (ADS)

    Liang, Linyun; Li, Qun; Hu, Jiamian; Lee, Shiwoo; Gerdes, Kirk; Chen, Long-Qing

    2015-02-01

    A phase field model is developed to examine microstructural evolution of an infiltrated solid oxide fuel cell cathode. It is employed to generate the three-phase backbone microstructures and morphology of infiltrate nano-particles [La1-xSrxMnO3 (LSM)]. Two-phase Y2O3 + ZrO2 and LSM backbones composed of 0.5-1 μm particles are first generated and then seeded with infiltrate, and evolution is compared for starting infiltrate particle diameters of 5 nm and 10 nm. The computed lifetime triple phase boundary (3PB) density of the infiltrated cathode is then compared to the cathode backbone. Results indicate that initial coarsening of infiltrate nano-particles is the primary evolution process, and infiltrate coarsening is the majority contributor to 3PB reduction. However, at all times, the infiltrated cathode possesses significantly greater 3PB length than even the uncoarsened backbone. Infiltrate particle size effects indicate that the smaller particle size produces greater 3PB length for the same infiltration amount, consistent with intuition. A maximum 3PB enhancement is reached when increasing infiltrate particle loading, and the maximum enhancement depends on infiltrate particle size. It is found that architectural degradation modes will insignificantly affect the lifetime performance of infiltrated cathodes. This work suggests that lifetime optimized particle size/loading combinations are identifiable, and can be precise if additional fundamental data become available.

  5. Uncovering the role of cathode buffer layer in organic solar cells

    NASA Astrophysics Data System (ADS)

    Qi, Boyuan; Zhang, Zhi-Guo; Wang, Jizheng

    2015-01-01

    Organic solar cells (OSCs) as the third generation photovoltaic devices have drawn intense research, for their ability to be easily deposited by low-cost solution coating technologies. However the cathode in conventional OSCs, Ca, can be only deposited by thermal evaporation and is highly unstable in ambient. Therefore various solution processible cathode buffer layers (CBLs) are synthesized as substitute of Ca and show excellent effect in optimizing performance of OSCs. Yet, there is still no universal consensus on the mechanism that how CBL works, which is evidently a critical scientific issue that should be addressed. In this article detailed studies are targeted on the interfacial physics at the interface between active layer and cathode (with and without treatment of a polar CBL) by using ultraviolet photoelectron spectroscopy, capacitance-voltage measurement, and impedance spectroscopy. The experimental data demonstrate that CBL mainly takes effect in three ways: suppressing surface states at the surface of active layer, protecting the active layer from being damaged by thermally evaporated cathode, and changing the energy level alignment by forming dipole moments with active layer and/or cathode. Our findings here provide a comprehensive picture of interfacial physics in devices with and without CBL.

  6. Uncovering the role of cathode buffer layer in organic solar cells.

    PubMed

    Qi, Boyuan; Zhang, Zhi-Guo; Wang, Jizheng

    2015-01-01

    Organic solar cells (OSCs) as the third generation photovoltaic devices have drawn intense research, for their ability to be easily deposited by low-cost solution coating technologies. However the cathode in conventional OSCs, Ca, can be only deposited by thermal evaporation and is highly unstable in ambient. Therefore various solution processible cathode buffer layers (CBLs) are synthesized as substitute of Ca and show excellent effect in optimizing performance of OSCs. Yet, there is still no universal consensus on the mechanism that how CBL works, which is evidently a critical scientific issue that should be addressed. In this article detailed studies are targeted on the interfacial physics at the interface between active layer and cathode (with and without treatment of a polar CBL) by using ultraviolet photoelectron spectroscopy, capacitance-voltage measurement, and impedance spectroscopy. The experimental data demonstrate that CBL mainly takes effect in three ways: suppressing surface states at the surface of active layer, protecting the active layer from being damaged by thermally evaporated cathode, and changing the energy level alignment by forming dipole moments with active layer and/or cathode. Our findings here provide a comprehensive picture of interfacial physics in devices with and without CBL. PMID:25588623

  7. Nanostructured MnO2-Based Cathodes for Li-Ion/Polymer Cells

    NASA Technical Reports Server (NTRS)

    Skandan, Ganesh; Singhal, Amit

    2005-01-01

    Nanostructured MnO2-based cathodes for Li-ion/polymer electrochemical cells have been investigated in a continuing effort to develop safe, high-energy-density, reliable, low-toxicity, rechargeable batteries for a variety of applications in NASA programs and in mass-produced commercial electronic equipment. Whereas the energy densities of state-of-the-art lithium-ion/polymer batteries range from 150 to 175 W h/kg, the goal of this effort is to increase the typical energy density to about 250 W h/kg. It is also expected that an incidental benefit of this effort will be increases in power densities because the distances over which Li ions must diffuse through nanostructured cathode materials are smaller than those through solid bulk cathode materials.

  8. Low-Work-Function, ITO-Free Transparent Cathodes for Inverted Polymer Solar Cells.

    PubMed

    Xue, Zhichao; Liu, Xingyuan; Lv, Ying; Zhang, Nan; Guo, Xiaoyang

    2015-09-16

    A low-work-function, indium tin oxide (ITO)-free transparent cathode having a tin oxide (SnOX)/Ag/SnOX/bismuth oxide (Bi2O3) (SASB) structure is developed without using annealing treatment. This represents the first time that Bi2O3 has been introduced to lower the work function of transparent electrodes. The SASB transparent cathode exhibits excellent photoelectric properties with a maximum transmittance of ∼88%, a low sheet resistance of ∼9.0 Ω·sq(-1), and a suitable work function of 4.22 eV that matches the lowest unoccupied molecular orbital level of the acceptor for exacting electrons efficiently. The power conversion efficiency of the polymer solar cell with the SASB electrode is 6.21%, which is comparable to that of ITO-based devices. The results indicate that SASB is a good alternative to ITO as transparent cathodes in optoelectronic devices. PMID:26323711

  9. Effect of cathode electron acceptors on simultaneous anaerobic sulfide and nitrate removal in microbial fuel cell.

    PubMed

    Cai, Jing; Zheng, Ping; Mahmood, Qaisar

    2016-01-01

    The current investigation reports the effect of cathode electron acceptors on simultaneous sulfide and nitrate removal in two-chamber microbial fuel cells (MFCs). Potassium permanganate and potassium ferricyanide were common cathode electron acceptors and evaluated for substrate removal and electricity generation. The abiotic MFCs produced electricity through spontaneous electrochemical oxidation of sulfide. In comparison with abiotic MFC, the biotic MFC showed better ability for simultaneous nitrate and sulfide removal along with electricity generation. Keeping external resistance of 1,000 Ω, both MFCs showed good capacities for substrate removal where nitrogen and sulfate were the main end products. The steady voltage with potassium permanganate electrodes was nearly twice that of with potassium ferricyanide. Cyclic voltammetry curves confirmed that the potassium permanganate had higher catalytic activity than potassium ferricyanide. The potassium permanganate may be a suitable choice as cathode electron acceptor for enhanced electricity generation during simultaneous treatment of sulfide and nitrate in MFCs. PMID:26901739

  10. Performance and durability of electrodes with platinum catalysts in polymer electrolyte cells prepared by ultrasonic spray deposition

    NASA Astrophysics Data System (ADS)

    Rigdon, William A.

    The development of stable platinum electrocatalysts for durable electrode performance has been a goal of this research. Cost of these materials is a major barrier to commercialization of technology such as polymer electrolyte fuel cells. Catalysts need to be supported on inexpensive materials that use a minimal amount of platinum while maintaining a high activity over the life of the device. Carbon support corrosion is the origin of many problems plaguing electrocatalyst longevity. Instead of replacing carbon with a ceramic or another single phase material, this dissertation has explored a composite consisting of both carbon nanotubes and titania to support platinum catalysts. Graphitized carbons and stable metal oxides have become a popular material selection for catalyst supports in many recent publications, but their design lacks a fundamental understanding. High performance and durability have been reported, although successful application in working electrodes is necessary to validate these advantages. Titania and carbon nanotube supports for platinum were able to better preserve catalyst performance than a control without titania in the cathode. Choice of a niobium donor dopant in titania was used in an approach to modify the structure and electronic properties of the metal oxide phase when integrated into the anode. When included into electrocatalysts, semiconductor oxides promote bifunctional mechanisms through junctions formed with the catalyst. Strong metal-support interactions enhanced catalyst bonding characteristics extended from the support. An ultrasonic spray deposition process was used to prepare membrane electrode assemblies from the synthesized electrocatalysts. A synergy between both performance and durability of electrodes can be realized by design of better composite supports used in fuel cells and potentially other related electrochemical devices.

  11. Catalysts of plant cell wall loosening

    PubMed Central

    Cosgrove, Daniel J.

    2016-01-01

    The growing cell wall in plants has conflicting requirements to be strong enough to withstand the high tensile forces generated by cell turgor pressure while selectively yielding to those forces to induce wall stress relaxation, leading to water uptake and polymer movements underlying cell wall expansion. In this article, I review emerging concepts of plant primary cell wall structure, the nature of wall extensibility and the action of expansins, family-9 and -12 endoglucanases, family-16 xyloglucan endotransglycosylase/hydrolase (XTH), and pectin methylesterases, and offer a critical assessment of their wall-loosening activity PMID:26918182

  12. Design of an Advanced Membrane Electrode Assembly Employing a Double-Layered Cathode for a PEM Fuel Cell.

    PubMed

    Kim, GyeongHee; Eom, KwangSup; Kim, MinJoong; Yoo, Sung Jong; Jang, Jong Hyun; Kim, Hyoung-Juhn; Cho, EunAe

    2015-12-23

    The membrane electrolyte assembly (MEA) designed in this study utilizes a double-layered cathode: an inner catalyst layer prepared by a conventional decal transfer method and an outer catalyst layer directly coated on a gas diffusion layer. The double-layered structure was used to improve the interfacial contact between the catalyst layer and membrane, to increase catalyst utilization and to modify the removal of product water from the cathode. Based on a series of MEAs with double-layered cathodes with an overall Pt loading fixed at 0.4 mg cm(-2) and different ratios of inner-to-outer Pt loading, the MEA with an inner layer of 0.3 mg Pt cm(-2) and an outer layer of 0.1 mg Pt cm(-2) exhibited the best performance. This performance was better than that of the conventional single-layered electrode by 13.5% at a current density of 1.4 A cm(-2). PMID:26630367

  13. Different materials as a cathode modification layer on the impact of organic solar cells

    NASA Astrophysics Data System (ADS)

    Zhong, Jian; Huang, Qiuyan; Yu, Junsheng; Jiang, Yadong

    2010-10-01

    Organic thin film solar cells based on conjugated polymer or small molecules have showed an interesting approach to energy conversion since Tang reported a single donor-accepter hetero-junction solar cell. The power conversion efficiency of organic solar cells has increased steadily over last decade. Small-molecular weight organic double heterojunction donor-acceptor layer organic solar cells (OSC) with a structure of indium-tin-oxide (ITO)/CuPc(200Å)/C60(400Å)/x/Ag(1000Å), using CuPc(copper Phthalocyanine)as donor layer, and Alq3(8-Hydroxyquinoline aluminum salt), BCP(Bromocresol purple sodium salt) and Bphen(4'7-diphyenyl-1,10-phenanthroline) as cathode modification layer, respectively were fabricated. The performance of OSC was studied as a function of the different materials as an cathode modification layer to optimize the structure. The current-voltage characteristic of the solar cell under AM1.5 solar illumination at an intensity of 100 mw/cm2 showed that the power conversion efficiency (PCE) was dependent of the different materials of the cathode modification layer. the efficiency along with the different materials as an cathode modification layer will diminish under that standard solar illumination(AM1.5)was obtained. Using a double heterostructure of ITO/CuPc(200Å)/C60(400Å)/Alq3(60Å)/Ag(1000Å) with high-vacuum evaporation technology, the efficiency was 0.587%.the efficiency was 0.967% when the material of the cathode modification layer was BCP, with the structure of ITO/CuPc(200Å)/C60(400Å)/BCP(35Å)/Ag(1000Å), and the efficiency was 0.742% when the material of the cathode modification layer was Bphen, with the structure of ITO/CuPc(200Å)/C60(400Å)/ Bphen(50Å)/Ag(1000Å).Using different materials as a cathode modification layer, it can be seen that the material which matches the energy level could even eventually be able to improve the energy conversion efficiency more.

  14. Cathodes for secondary electrochemical power-producing cells. [layers of porous substrates impregnated with S alternate with layers containing electrolyte

    DOEpatents

    Cairns, E.J.; Kyle, M.; Shimotake, H.

    1973-02-13

    A secondary electrochemical power-producing cell includes an anode containing lithium, an electrolyte containing lithium ions, and a cathode containing sulfur. The cathode comprises plates of a porous substrate material impregnated with sulfur alternating with layers (which may also comprise porous substrate plates) containing electrolyte.

  15. High-performance, low Pt content catalysts for the electroreduction of oxygen in polymer-electrolyte fuel cells

    SciTech Connect

    Fournier, J.; Faubert, G.; Tilquin, J.Y.; Cote, R.; Guay, D.; Dodelet, J.P.

    1997-01-01

    Pt-included and Pt-supported catalysts have been synthesized using graphite and carbon black supports of various specific areas. The graphites are KS6 (20 m{sup 2}/g), HS100 (110 m{sup 2}/g), and HS300 (305 m{sup 2}/g) from Lonza, and the carbon blacks are Vulcan (254 m{sup 2}/g) and Black Pearls (1475 m{sup 2}/g) from Cabot. The Pt-included and Pt-supported catalysts were used at the cathode of a H{sub 2}/O{sub 2} fuel cell, and their polarization curves were compared to each other and to those of various Pt-supported catalysts from E-TEK. In the high current region of interest to fuel cell developers, it is shown that Pt-supported catalysts perform better than Pt-included ones when the specific area of the support is small. The contrary is true when the specific area of the support is large. The best catalysts are HS300-Pti [8.3 weight percent (w/o) Pt included in HS300 graphite] and Vu-Pti (6.1 w/o Pt included in Vulcan XC-72R). These catalysts display very high mass and specific activities for O{sub 2} reduction. Furthermore, the iR-corrected polarization curves of both HS300-Pti (with a Pt loading of 0.110 mg/cm{sup 2}) and Vu-Pti (with a Pt loading of 0.070 mg/cm{sup 2}) cross at high current the polarization curve of the electrode prepared with E-TEK20 (20 w/o of supported Pt, with a Pt loading of 0.287 mg/cm{sup 2}). Pt inclusion in graphite or carbon black is therefore an interesting way of reducing the Pt loading of fuel cell cathodes without lowering electrochemical performance. HS300-Pti have been characterized by X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy. These analyses indicate that they both contain metallic Pt and Pt(II and IV) oxides and/or hydroxides.

  16. Platinum-ruthenium-palladium alloys for use as a fuel cell catalyst

    DOEpatents

    Gorer, Alexander

    2002-01-01

    A noble metal alloy composition for a fuel cell catalyst, a ternary alloy composition containing platinum, ruthenium and palladium. The alloy shows increased activity as compared to well-known catalysts.

  17. NREL Team Creates High-Activity, Durable Platinum Extended Surface Catalyst for Fuel Cells (Fact Sheet)

    SciTech Connect

    Not Available

    2011-02-01

    Researchers with NREL's Fuel Cell team showed that platinum can replace copper nanowires in such a way that high-surface-area and high-specific-activity catalysts are produced, potentially allowing for lower-cost catalysts.

  18. Phase III Advanced Anodes and Cathodes Utilized in Energy Efficient Aluminum Production Cells

    SciTech Connect

    R.A. Christini; R.K. Dawless; S.P. Ray; D.A. Weirauch, Jr.

    2001-11-05

    During Phase I of the present program, Alcoa developed a commercial cell concept that has been estimated to save 30% of the energy required for aluminum smelting. Phase ii involved the construction of a pilot facility and operation of two pilots. Phase iii of the Advanced Anodes and Cathodes Program was aimed at bench experiments to permit the resolution of certain questions to be followed by three pilot cells. All of the milestones related to materials, in particular metal purity, were attained with distinct improvements over work in previous phases of the program. NiO additions to the ceramic phase and Ag additions to the Cu metal phase of the cermet improved corrosion resistance sufficiently that the bench scale pencil anodes met the purity milestones. Some excellent metal purity results have been obtained with anodes of the following composition: Further improvements in anode material composition appear to be dependent on a better understanding of oxide solubilities in molten cryolite. For that reason, work was commissioned with an outside consultant to model the MeO - cryolite systems. That work has led to a better understanding of which oxides can be used to substitute into the NiO-Fe2O3 ceramic phase to stabilize the ferrites and reduce their solubility in molten cryolite. An extensive number of vertical plate bench electrolysis cells were run to try to find conditions where high current efficiencies could be attained. TiB2-G plates were very inconsistent and led to poor wetting and drainage. Pure TiB2 did produce good current efficiencies at small overlaps (shadowing) between the anodes and cathodes. This bench work with vertical plate anodes and cathodes reinforced the importance of good cathode wetting to attain high current efficiencies. Because of those conclusions, new wetting work was commissioned and became a major component of the research during the third year of Phase III. While significant progress was made in several areas, much work needs to be

  19. Improving performance of inverted organic solar cells using ZTO nanoparticles as cathode buffer layer

    NASA Astrophysics Data System (ADS)

    Tsai, Meng-Yen; Cheng, Wen-Hui; Jeng, Jiann-Shing; Chen, Jen-Sue

    2016-06-01

    In this study, a low-temperature solution-processed zinc tin oxide (ZTO) films are successfully utilized as the cathode buffer layer in the inverted organic P3HT:PCBM bulk heterojunction solar cells. ZTO film cathode buffer layer with an appropriate Sn-doping concentration outperforms the zinc oxide (ZnO) film with an improved power conversion efficiency (1.96% (ZTO film) vs. 1.56% (ZnO film)). Furthermore, ZTO nanoparticles (NPs) are also synthesized via low-temperature solution route and the device with ZTO NPs buffer layer exhibits a significant improvement in device performance to reach a PCE of 2.60%. The crystallinity of the cathode buffer layer plays an influential factor in the performance. From impedance spectroscopy analysis, a correlation between short circuit current (Jsc), carrier life time (τavg) and, thus, PCE is observed. The interplay between composition and crystallinity of the cathode buffer layers is discussed to find their influences on the solar cell performance.

  20. An investigation of anode and cathode materials in photomicrobial fuel cells.

    PubMed

    Schneider, Kenneth; Thorne, Rebecca J; Cameron, Petra J

    2016-02-28

    Photomicrobial fuel cells (p-MFCs) are devices that use photosynthetic organisms (such as cyanobacteria or algae) to turn light energy into electrical energy. In a p-MFC, the anode accepts electrons from microorganisms that are either growing directly on the anode surface (biofilm) or are free floating in solution (planktonic). The nature of both the anode and cathode material is critical for device efficiency. An ideal anode is biocompatible and facilitates direct electron transfer from the microorganisms, with no need for an electron mediator. For a p-MFC, there is the additional requirement that the anode should not prevent light from perfusing through the photosynthetic cells. The cathode should facilitate the rapid reaction of protons and oxygen to form water so as not to rate limit the device. In this paper, we first review the range of anode and cathode materials currently used in p-MFCs. We then present our own data comparing cathode materials in a p-MFC and our first results using porous ceramic anodes in a mediator-free p-MFC. PMID:26755764

  1. Non-noble catalysts and catalyst supports for phosphoric acid fuel cells

    NASA Technical Reports Server (NTRS)

    Mcalister, A. J.

    1981-01-01

    Tungsten carbide, which is active for hydrogen oxidation, is CO tolerant and has a hexagonal structure is discussed. Titanium carbide is inactive and has a cubic structure. Four different samples of the cubic alloys W sub x-1Ti sub XC sub 1-y were found to be active and CO tolerant. When the activities of these cubic alloys are weighted by the reciprocal of the square to those of highly forms of WC. They offer important insight into the nature of the active sites on W-C anode catalysts for use in phosphoric acid fuel cells.

  2. Non-noble catalysts and catalyst supports for phosphoric acid fuel cells

    NASA Technical Reports Server (NTRS)

    Mcalister, A. J.

    1981-01-01

    Four different samples of the cubic alloys W sub x-1 Ti sub x C sub 1-y were prepared and found to be active and CO tolerant. When the activities of these cubic alloys were weighted by the reciprocal of the square of the W exchange, they displayed magnitudes and dependence on bulk C deficiency comparable to those of highly active forms of WC. It is concluded that they may offer important insight into the nature of the active sites on, and means for improving the performance of, W-C anode catalysts for use in phosphoric acid fuel cells.

  3. Non-noble catalysts and catalyst supports for phosphoric acid fuel cells

    NASA Technical Reports Server (NTRS)

    Mcalister, A. J.

    1980-01-01

    Tungsten carbide, which is known to be active for hydrogen oxidation and CO tolerant has a hexagonal structure. Titanium carbide is inactive and has a cubic structure. Four different samples of the cubic alloys Wx-1TixC were prepared and found to be active and CO tolerant. These alloys are of interest as possible phosphoric acid fuel cell catalysts. They also are of interest as opportunities to study the activity of W in a different crystalline environment and to correlate the activities of the surface sites with surface composition.

  4. Low platinum loading cathode modified with Cs3H2PMo10V2O40 for polymer electrolyte membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Renzi, M.; D'Angelo, G.; Marassi, R.; Nobili, F.

    2016-09-01

    The catalytic activity of commercial Pt nanoparticles mixed with mesoporous polyoxometalate Cs3H2PMo10V2O40 towards oxygen reduction reaction is evaluated. The polyoxometalate co-catalyst is prepared by titration of an aqueous solution of phosphovanadomolibdic acid. SEM micrography shows reduction particle size to less than 300 nm, while XRD confirms that the resulting salt maintains the Kegging structure. The composite catalyst is prepared by mixing the POM salt with Pt/C by sonication. RRDE studies show better kinetics for ORR with low Pt loading at the electrode surface. A MEA is assembled by using a Pt/POM-based cathode, in order to assess performance in a working fuel cell. Current vs. potential curves reveals comparable or better performances at 100%, 62% and 17% relative humidity for the POM-modified MEA with respect to a commercial MEA with higher Pt loading at the cathode. Electrochemical impedance spectroscopy (EIS) confirms better kinetics at low relative humidity. Finally, an accelerated stress test (AST) with square wave (SW) between 0.4 V and 0.8 V is performed to evaluate MEA stability for at least 100 h and make predictions about lifetime, showing that after initial losses the catalytic system can retain stable performance and good morphological stability.

  5. Nano-Engineered Catalysts for Direct Methanol Fuel Cells

    NASA Technical Reports Server (NTRS)

    Myung, Nosang; Narayanan, Sekharipuram; Wiberg, Dean

    2008-01-01

    Nano-engineered catalysts, and a method of fabricating them, have been developed in a continuing effort to improve the performances of direct methanol fuel cells as candidate power sources to supplant primary and secondary batteries in a variety of portable electronic products. In order to realize the potential for high energy densities (as much as 1.5 W h/g) of direct methanol fuel cells, it will be necessary to optimize the chemical compositions and geometric configurations of catalyst layers and electrode structures. High performance can be achieved when catalyst particles and electrode structures have the necessary small feature sizes (typically of the order of nanometers), large surface areas, optimal metal compositions, high porosity, and hydrophobicity. The present method involves electrodeposition of one or more catalytic metal(s) or a catalytic-metal/polytetrafluoroethylene nanocomposite on an alumina nanotemplate. The alumina nanotemplate is then dissolved, leaving the desired metal or metal/polytetrafluoroethylene-composite catalyst layer. Unlike some prior methods of making fine metal catalysts, this method does not involve processing at elevated temperature; all processing can be done at room temperature. In addition, this method involves fewer steps and is more amenable to scaling up for mass production. Alumina nanotemplates are porous alumina membranes that have been fabricated, variously, by anodizing either pure aluminum or aluminum that has been deposited on silicon by electronbeam evaporation. The diameters of the pores (7 to 300 nm), areal densities of pores (as much as 7 x 10(exp 10)sq cm), and lengths of pores (up to about 100 nm) can be tailored by selection of fabrication conditions. In a given case, the catalytic metal, catalytic metal alloy, or catalytic metal/ polytetrafluoroethylene composite is electrodeposited in the pores of the alumina nanotemplate. The dimensions of the pores, together with the electrodeposition conditions

  6. Immobilized Enzymes and Cells as Practical Catalysts

    NASA Astrophysics Data System (ADS)

    Klibanov, Alexander M.

    1983-02-01

    Performance of enzymes and whole cells in commercial applications can often be dramatically improved by immobilization of the biocatalysts, for instance, by their covalent attachment to or adsorption on solid supports, entrapment in polymeric gels, encapsulation, and cross-linking. The effect of immobilization on enzymatic properties and stability of biocatalysts is considered. Applications of immobilized enzymes and cells in the chemical, pharmaceutical, and food industries, in clinical and chemical analyses, and in medicine, as well as probable future trends in enzyme technology are discussed.

  7. Immobilized enzymes and cells as practical catalysts

    SciTech Connect

    Klibanov, A.M.

    1983-02-11

    Performance of enzymes and whole cells in commercial applications can often be dramatically improved by immobilization of the biocatalysts, for instance, by their covalent attachment to or adsorption on solid supports, entrapment in polymeric gels, encapsulation, and cross-linking. The effect of immobilization on enzymatic properties and stability of biocatalysts is considered. Applications of immobilized enzymes and cells in the chemical, pharmaceutical, and food industries, in clinical and chemical analyses, and in medicine, as well as probable future trends in enzyme technology are discussed.

  8. Formation of Deposits on the Cathode Surface of Aluminum Electrolysis Cells

    NASA Astrophysics Data System (ADS)

    Allard, François; Soucy, Gervais; Rivoaland, Loig

    2014-12-01

    The efficiency of electrolysis cells for aluminum production is reduced when deposits are formed on the cathode block surface. Overfeeding of alumina or excessive heat loss in industrial cells leads to the formation of highly resistive deposits. In this study, the chemical composition of sludge, ledge toe, and thin deposits was investigated at the bottom of both industrial and experimental electrolysis cells. The formation of deposits in laboratory experiments was demonstrated in acidic, neutral, and basic electrolytic bath. A gradient of chiolite (Na5Al3F14) and α-Al2O3 was observed in the deposits. The bath at the bottom of the experimental electrolysis cell had a higher cryolite ratio implying a higher liquidus temperature. The sludge formed at the bottom of the cell can lift the aluminum metal resulting in an important reduction of the contact surface between the aluminum and the cathode block. Moreover, the deposits disturb the current path and generate horizontal current components in the metal which enhance the motion and lower the current efficiency. A thin film of bath supersaturated in alumina was observed under the metal. This work provides clarification on the formation mechanisms of the various deposits responsible for the deterioration of the cathode surface.

  9. Composite cathode materials development for intermediate temperature solid oxide fuel cell systems

    NASA Astrophysics Data System (ADS)

    Qin, Ya

    Solid oxide fuel cell (SOFC) systems are of particular interest as electrochemical power systems that can operate on various hydrocarbon fuels with high fuel-to-electrical energy conversion efficiency. Within the SOFC stack, La0.8Sr 0.2Ga0.8Mg0.115Co0.085O3-delta (LSGMC) has been reported as an optimized composition of lanthanum gallate based electrolytes to achieve higher oxygen ionic conductivity at intermediate temperatures, i.e., 500-700°C. The electrocatalytic properties of interfaces between LSGMC electrolytes and various candidate intermediate-temperature SOFC cathodes have been investigated. Sm0.5Sr0.5CoO 3-delta (SSC), and La0.6Sr0.4Co0.2Fe 0.8O3-delta (LSCF), in both pure and composite forms with LSGMC, were investigated with regards to both oxygen reduction and evolution, A range of composite cathode compositions, having ratios of SSC (in wt.%) with LSGMC (wt.%) spanning the compositions 9:1, 8:2, 7:3, 6:4 and 5:5, were investigated to determine the optimal cathode-electrolyte interface performance at intermediate temperatures. All LSGMC electrolyte and cathode powders were synthesized using the glycine-nitrate process (GNP). Symmetrical electrochemical cells were investigated with three-electrode linear dc polarization and ac impedance spectroscopy to characterize the kinetics of the interfacial reactions in detail. Composite cathodes were found to perform better than the single phase cathodes due to significantly reduced polarization resistances. Among those composite SSC-LSGMC cathodes, the 7:3 composition has demonstrated the highest current density at the equivalent overpotential values, indicating that 7:3 is an optimal mixing ratio of the composite cathode materials to achieve the best performance. For the composite SC-LSGMC cathode/LSGMC interface, the cathodic overpotential under 1 A/cm2 current density was as low as 0.085 V at 700°C, 0.062V at 750°C and 0.051V at 800°C in air. Composite LSCF-LSGMC cathode/LSGMC interfaces were found to have

  10. A dual-chambered microbial fuel cell with Ti/nano-TiO2/Pd nano-structure cathode

    NASA Astrophysics Data System (ADS)

    Hosseini, Mir Ghasem; Ahadzadeh, Iraj

    2012-12-01

    In this research, Ti/nano-TiO2/Pd nano-structure electrode is prepared, characterized and applied as cathode electrode in a dual-chambered microbial fuel cell with graphite anode and Flemion cation exchange membrane. Prepared nano-structured electrode morphology and mixed-culture biofilm formed on the anode are studied by scanning electron microscopy (SEM). Cell performance is investigated by polarization, cyclic voltammetery (CV) and electrochemical impedance spectroscopy (EIS) methods. Results show that Ti/nano-TiO2/Pd electrode exhibits satisfactory long term performance as a cathode to reduce water dissolved oxygen. The maximum output power of the cell is about 200 mW m-2 normalized to the cathode surface area. Open circuit potential (OCP) of the cell is about 480 mV and value of the short circuit current is 0.21 mA cm-2 of the cathode geometric surface area. Thus this nano-structure cathode can produce comparable output power to that of platinum-based cathodes such as Pt-doped carbon paper; therefore due to the ease of preparation and low cost, this electrode can be applied as alternative to platinum-based cathodes in microbial fuel cells.

  11. Solution-Processed 8-Hydroquinolatolithium as Effective Cathode Interlayer for High-Performance Polymer Solar Cells.

    PubMed

    Liu, Wenqing; Liang, Tao; Chen, Qi; Yu, Zhikai; Zhang, Yingying; Liu, Yujing; Fu, Weifei; Tang, Feng; Chen, Liwei; Chen, Hongzheng

    2016-04-13

    Solution-processed 8-hydroxyquinolinatolithium (s-Liq) was successfully applied as an efficient cathode interlayer in bulk heterojunction polymer solar cells (PSCs), giving rise to enhancement in device performance. The ultraviolet photoelectron spectra results revealed that the presence of s-Liq could lower work function of Al cathode, allowing for the ohmic contacts with the fullerene acceptor for better electron extraction and also a larger work function difference between the two electrodes, which leads to an increase in open-circuit voltage (V(oc)). Scanning Kelvin probe microscopy study on the surface potential of active layers suggested that an interfacial dipole was formed in the s-Liq interlayer between the active layer and the Al cathode, which enhanced the intrinsic built-in potential in the device for better charge transportation and extraction. Consequently, the V(oc), fill factor, and current density of the device can be improved by the introduction of s-Liq interlayer, leading to a power conversion efficiency (PCE) improvement. With PTB7 (or PTB7-Th) as the donor and PC71BM as the acceptor, the s-Liq-based PSC devices exhibited a PCE of 8.37% (or 9.04%), much higher than those of devices with the evaporated Liq (7.62%) or commonly used PFN (8.14%) as the cathode interlayer. Moreover, the s-Liq-based devices showed good stability, maintaining 75% (in N2) and 45% (in air) of the initial PCE after 7 days, respectively. These results suggest the great potential of s-Liq as cathode interlayer material for high-performance solar cells application. PMID:27015527

  12. Cathode pressure modeling of the Buckeye Bullet II 500kW PEM fuel cell system

    NASA Astrophysics Data System (ADS)

    Hillstrom, Edward T.

    This dissertation details the development of a model that simulates the pressure dynamics of the cathode supply system for the Buckeye Bullet 2, the worlds fastest hydrogen fuel cell vehicle. Due to the extreme power levels of the BB2 system, and the unique use of heliox as the oxidant supply, it is shown that existing system level models for predicting the fuel cell pressure dynamics do not adequately capture the dynamics of the BB2 system. Several modeling attempts are evaluated, and eventually the most robust model is a model which is derived from a rational system decomposition of the cathode system. By separating the major losses of the cathode system into an upstream and downstream resistance, the performance of the model is significantly improved. It is shown that the rate at which water exits the cathode plays a significant role accurately capturing the pressure dynamics. With this in mind, a distributed parameter model is developed to provide estimates of how the rate of liquid water removal from cathode changes with time. The results of this model are validated through physical testing. The resulting model relies on five empirically tunable parameters to tune the model performance to match that of the system. The method of calibrating these parameters is outlined, and the resulting model developed with stationary test data is compared to data from the actual BB2 race data. Only a few parameters need to be recalibrated, which is due to physical system differences between the data from the stationary tests and the race data.

  13. Transparent ITO/Ag-Pd-Cu/ITO multilayer cathode use in inverted organic solar cells

    SciTech Connect

    Kim, Hyo-Joong; Kim, Han-Ki; Lee, Hyun Hwi; Kal, Jinha; Hahn, Jungseok

    2015-10-15

    The characteristics of transparent ITO/Ag-Pd-Cu (APC)/ITO multilayer cathodes were investigated for use in inverted organic solar cells (IOSCs). The insertion of an APC interlayer into the ITO film effectively led to crystallization of the top ITO layer, unlike that in the Ag interlayer, and resulted in a low sheet resistance of 6.55 Ohm/square and a high optical transmittance of 84.14% without post annealing. In addition, the alloying of the Pd and Cu elements into Ag prevented agglomeration and oxidization of the metal interlayer and led to more stable ITO/APC/ITO films under ambient conditions. The microstructure and interfacial structure of the transparent ITO/APC/ITO cathode in the IOSCs were examined in detail by synchrotron X-ray scattering and high resolution transmission electron microscopy. Furthermore, we suggested a possible mechanism to explain the lower PCE of the IOSCs with an ITO/APC/ITO cathode than that of a reference IOSC with a crystalline ITO cathode using the external quantum efficiency of the IOSCs.

  14. Comparative analysis of microbial community between different cathode systems of microbial fuel cells for denitrification.

    PubMed

    Li, Chao; Xu, Ming; Lu, Yi; Fang, Fang; Cao, Jiashun

    2016-03-01

    Two types of cathodic biofilm in microbial fuel cells (MFC) were established for comparison on their performance and microbial communities. Complete autotrophic simultaneous nitrification and denitrification (SND) without organics addition was achieved in nitrifying-MFC (N-MFC) with a total nitrogen (TN) removal rate of 0.35 mg/(L·h), which was even higher than that in denitrifying-MFC (D-MFC) at same TN level. Integrated denaturing gradient gel electrophoresis analysis based on both 16S rRNA and nirK genes showed that Alpha-, Gammaproteobacteria were the main denitrifier communities. Some potential autotrophic denitrifying bacteria which can use electrons and reducing power from cathodes, such as Shewanella oneidensis, Shewanella loihica, Pseudomonas aeruginosa, Starkeya novella and Rhodopseudomonas palustris were identified and selectively enriched on cathode biofilms. Further, relative abundance of denitrifying bacteria characterized by nirK/16S ratios was much higher in biofilm than suspended sludge according to real-time polymerase chain reaction. The highest enrichment efficiency for denitrifiers was obtained in N-MFC cathode biofilms, which confirmed autotrophic denitrifying bacteria enrichment is the key factor for a D-MFC system. PMID:26278100

  15. Sequestration of CO2 discharged from anode by algal cathode in microbial carbon capture cells (MCCs).

    PubMed

    Wang, Xin; Feng, Yujie; Liu, Jia; Lee, He; Li, Chao; Li, Nan; Ren, Nanqi

    2010-08-15

    Due to increased discharge of CO(2) is incurring problems, CO(2) sequestration technologies require substantial development. By introducing anodic off gas into an algae grown cathode (Chlorella vulgaris), new microbial carbon capture cells (MCCs) were constructed and demonstrated here to be an effective technology for CO(2) emission reduction with simultaneous voltage output without aeration (610+/-50 mV, 1000 Omega). Maximum power densities increased from 4.1 to 5.6 W/m(3) when the optical density (OD) of cathodic algae suspension increased from 0.21 to 0.85 (658 nm). Compared to a stable voltage of 706+/-21 mV (1000 Omega) obtained with cathodic dissolved oxygen (DO) of 6.6+/-1.0 mg/L in MCC, voltage outputs decreased from 654 to 189 mV over 70 h in the control reactor (no algae) accompanied with a decrease in DO from 7.6 to 0.9 mg/L, indicating that cathode electron acceptor was oxygen. Gas analysis showed that all the CO(2) generated from anode was completely eliminated by catholyte, and the soluble inorganic carbon was further converted into algal biomass. These results showed the possibility of a new method for simultaneous carbon fixing, power generation and biodiesel production during wastewater treatment without aeration. PMID:20547055

  16. Transparent ITO/Ag-Pd-Cu/ITO multilayer cathode use in inverted organic solar cells

    NASA Astrophysics Data System (ADS)

    Kim, Hyo-Joong; Lee, Hyun Hwi; Kal, Jinha; Hahn, Jungseok; Kim, Han-Ki

    2015-10-01

    The characteristics of transparent ITO/Ag-Pd-Cu (APC)/ITO multilayer cathodes were investigated for use in inverted organic solar cells (IOSCs). The insertion of an APC interlayer into the ITO film effectively led to crystallization of the top ITO layer, unlike that in the Ag interlayer, and resulted in a low sheet resistance of 6.55 Ohm/square and a high optical transmittance of 84.14% without post annealing. In addition, the alloying of the Pd and Cu elements into Ag prevented agglomeration and oxidization of the metal interlayer and led to more stable ITO/APC/ITO films under ambient conditions. The microstructure and interfacial structure of the transparent ITO/APC/ITO cathode in the IOSCs were examined in detail by synchrotron X-ray scattering and high resolution transmission electron microscopy. Furthermore, we suggested a possible mechanism to explain the lower PCE of the IOSCs with an ITO/APC/ITO cathode than that of a reference IOSC with a crystalline ITO cathode using the external quantum efficiency of the IOSCs.

  17. Secondary cell with orthorhombic alkali metal/manganese oxide phase active cathode material

    DOEpatents

    Doeff, M.M.; Peng, M.Y.; Ma, Y.; Visco, S.J.; DeJonghe, L.C.

    1996-09-24

    An alkali metal manganese oxide secondary cell is disclosed which can provide a high rate of discharge, good cycling capabilities, good stability of the cathode material, high specific energy (energy per unit of weight) and high energy density (energy per unit volume). The active material in the anode is an alkali metal and the active material in the cathode comprises an orthorhombic alkali metal manganese oxide which undergoes intercalation and deintercalation without a change in phase, resulting in a substantially linear change in voltage with change in the state of charge of the cell. The active material in the cathode is an orthorhombic structure having the formula M{sub x}Z{sub y}Mn{sub (1{minus}y)}O{sub 2}, where M is an alkali metal; Z is a metal capable of substituting for manganese in the orthorhombic structure such as iron, cobalt or titanium; x ranges from about 0.2 in the fully charged state to about 0.75 in the fully discharged state, and y ranges from 0 to 60 atomic %. Preferably, the cell is constructed with a solid electrolyte, but a liquid or gelatinous electrolyte may also be used in the cell. 11 figs.

  18. Real-time thermal imaging of solid oxide fuel cell cathode activity in working condition.

    PubMed

    Montanini, Roberto; Quattrocchi, Antonino; Piccolo, Sebastiano A; Amato, Alessandra; Trocino, Stefano; Zignani, Sabrina C; Faro, Massimiliano Lo; Squadrito, Gaetano

    2016-09-01

    Electrochemical methods such as voltammetry and electrochemical impedance spectroscopy are effective for quantifying solid oxide fuel cell (SOFC) operational performance, but not for identifying and monitoring the chemical processes that occur on the electrodes' surface, which are thought to be strictly related to the SOFCs' efficiency. Because of their high operating temperature, mechanical failure or cathode delamination is a common shortcoming of SOFCs that severely affects their reliability. Infrared thermography may provide a powerful tool for probing in situ SOFC electrode processes and the materials' structural integrity, but, due to the typical design of pellet-type cells, a complete optical access to the electrode surface is usually prevented. In this paper, a specially designed SOFC is introduced, which allows temperature distribution to be measured over all the cathode area while still preserving the electrochemical performance of the device. Infrared images recorded under different working conditions are then processed by means of a dedicated image processing algorithm for quantitative data analysis. Results reported in the paper highlight the effectiveness of infrared thermal imaging in detecting the onset of cell failure during normal operation and in monitoring cathode activity when the cell is fed with different types of fuels. PMID:27607294

  19. Secondary cell with orthorhombic alkali metal/manganese oxide phase active cathode material

    DOEpatents

    Doeff, Marca M.; Peng, Marcus Y.; Ma, Yanping; Visco, Steven J.; DeJonghe, Lutgard C.

    1996-01-01

    An alkali metal manganese oxide secondary cell is disclosed which can provide a high rate of discharge, good cycling capabilities, good stability of the cathode material, high specific energy (energy per unit of weight) and high energy density (energy per unit volume). The active material in the anode is an alkali metal and the active material in the cathode comprises an orthorhombic alkali metal manganese oxide which undergoes intercalation and deintercalation without a change in phase, resulting in a substantially linear change in voltage with change in the state of charge of the cell. The active material in the cathode is an orthorhombic structure having the formula M.sub.x Z.sub.y Mn.sub.(1-y) O.sub.2, where M is an alkali metal; Z is a metal capable of substituting for manganese in the orthorhombic structure such as iron, cobalt or titanium; x ranges from about 0.2 in the fully charged state to about 0.75 in the fully discharged state, and y ranges from 0 to 60 atomic %. Preferably, the cell is constructed with a solid electrolyte, but a liquid or gelatinous electrolyte may also be used in the cell.

  20. Oxidation catalyst

    DOEpatents

    Ceyer, Sylvia T.; Lahr, David L.

    2010-11-09

    The present invention generally relates to catalyst systems and methods for oxidation of carbon monoxide. The invention involves catalyst compositions which may be advantageously altered by, for example, modification of the catalyst surface to enhance catalyst performance. Catalyst systems of the present invention may be capable of performing the oxidation of carbon monoxide at relatively lower temperatures (e.g., 200 K and below) and at relatively higher reaction rates than known catalysts. Additionally, catalyst systems disclosed herein may be substantially lower in cost than current commercial catalysts. Such catalyst systems may be useful in, for example, catalytic converters, fuel cells, sensors, and the like.

  1. Inkjet-Printed Porous Silver Thin Film as a Cathode for a Low-Temperature Solid Oxide Fuel Cell.

    PubMed

    Yu, Chen-Chiang; Baek, Jong Dae; Su, Chun-Hao; Fan, Liangdong; Wei, Jun; Liao, Ying-Chih; Su, Pei-Chen

    2016-04-27

    In this work we report a porous silver thin film cathode that was fabricated by a simple inkjet printing process for low-temperature solid oxide fuel cell applications. The electrochemical performance of the inkjet-printed silver cathode was studied at 300-450 °C and was compared with that of silver cathodes that were fabricated by the typical sputtering method. Inkjet-printed silver cathodes showed lower electrochemical impedance due to their porous structure, which facilitated oxygen gaseous diffusion and oxygen surface adsorption-dissociation reactions. A typical sputtered nanoporous silver cathode became essentially dense after the operation and showed high impedance due to a lack of oxygen supply. The results of long-term fuel cell operation show that the cell with an inkjet-printed cathode had a more stable current output for more than 45 h at 400 °C. A porous silver cathode is required for high fuel cell performance, and the simple inkjet printing technique offers an alternative method of fabrication for such a desirable porous structure with the required thermal-morphological stability. PMID:27045453

  2. 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.

  3. Silver-praseodymium oxy-sulfate cermet: A new composite cathode for intermediate temperature solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Yang, Tao; Shaula, Aliaksandr L.; Mikhalev, Sergey M.; Ramasamy, Devaraj; Fagg, Duncan P.

    2016-02-01

    Ag-Pr2O2SO4 is identified as a promising new composite material to enhance the cathodic oxygen reduction reaction in solid oxide fuel cells. Ag-Pr2O2SO4 was studied in terms of synthesis, stability of Pr2O2SO4 in CO2, and electrochemical behavior as a cathode. The performance of the composite cathode was assessed as a function of temperature by A.C. impedance using a symmetrical cell arrangement in oxygen. The global performance of an anode-supported fuel cell Ag-Pr2O2SO4/CGO/NiO-CGO was also assessed, the highest power density being 1.5 W cm-2 at 800 °C. A longevity test of this cell performed at 800 °C under load for 24 days demonstrated high stability with Ag-Pr2O2SO4 cathode.

  4. Photoregenerative I−/I3− couple as a liquid cathode for proton exchange membrane fuel cell

    PubMed Central

    Liu, Zhen; Wang, Yadong; Ai, Xinping; Tu, Wenmao; Pan, Mu

    2014-01-01

    A photoassisted oxygen reduction reaction (ORR) through I−/I3− redox couple was investigated for proton exchange membrane (PEM) fuel cell cathode reaction. The I−/I3−-based liquid cathode was used to replace conventional oxygen cathode, and its discharge product I− was regenerated to I3− by photocatalytic oxidation with the participation of oxygen. This new and innovative approach may provide a strategy to eliminate the usage of challenging ORR electrocatalysts, resulting in an avenue for developing low-cost and high-efficiency PEM fuel cells. PMID:25348812

  5. Direct deposit of catalyst on the membrane of direct feed fuel cells

    NASA Technical Reports Server (NTRS)

    Chun, William (Inventor); Narayanan, Sekharipuram R. (Inventor); Jeffries-Nakamura, Barbara (Inventor); Valdez, Thomas I. (Inventor); Linke, Juergen (Inventor)

    2001-01-01

    An improved direct liquid-feed fuel cell having a solid membrane electrolyte for electrochemical reactions of an organic fuel. Catalyst utilization and catalyst/membrane interface improvements are disclosed. Specifically, the catalyst layer is applied directly onto the membrane electrolyte.

  6. Oxygen Tolerance of a Molecular Engineered Cathode for Hydrogen Evolution Based on a Cobalt Diimine-Dioxime Catalyst.

    PubMed

    Kaeffer, Nicolas; Morozan, Adina; Artero, Vincent

    2015-10-29

    We report here that a bioinspired cobalt diimine-dioxime molecular catalyst for hydrogen evolution immobilized onto carbon nanotube electrodes proves tolerant toward oxygen. The cobalt complex catalyzes O2 reduction with an onset potential of +0.55 V vs RHE. In this process, a mixture of water and hydrogen peroxide is produced in a 3:1 ratio. Our study evidences that such side-reductions have little impact on effectiveness of proton reduction by the grafted molecular catalyst which still displays good activity for H2 evolution in the presence of O2. The presence of O2 in the media is not detrimental toward H2 evolution under the conditions used, which simulate turn-on conditions of a water-splitting device. PMID:25993343

  7. Numerical Simulation of Current Distribution in Cathode Carbon Block of an Aluminum Reduction Cell

    NASA Astrophysics Data System (ADS)

    Tao, Wenju; Li, Tuofu; Wang, Zhaowen; Gao, Bingliang; Shi, Zhongning; Hu, Xianwei; Cui, Jianzhong

    2015-11-01

    Cathode carbon block wear is the main limiting factor for the lifetime of aluminum reduction cells. The wear rate is enhanced by current density. In this article, the current distribution at the surface of carbon block was calculated using a thermoelectric coupled model. Then the effects of effective length ( l e), height of the cathode carbon block ( h c), and width and height of the collector ( w b and h b) on current distribution were investigated. The results show that l e has a great effect on the current distribution. With l e decreasing, the maximum current density increases rapidly and shifts toward the cell center. When the l e decreases from 1.67 m to 1.51 m, the maximum current density increases by 57.9%. Moreover, the maximum current density will be reduced with increasing h c or h b × w b. For h b × w b = 180 mm × 180 mm2, the maximum current density is reduced by 27.8%. However, increasing h c or h b × w b will decrease the temperature in the cathode carbon block. The results of this study may provide the database optimization of cell operation and design.

  8. Improvement of performance in low temperature solid oxide fuel cells operated on ethanol and air mixtures using Cu-ZnO-Al2O3 catalyst layer

    NASA Astrophysics Data System (ADS)

    Morales, M.; Espiell, F.; Segarra, M.

    2015-10-01

    Anode-supported single-chamber solid oxide fuel cells with and without Cu-ZnO-Al2O3 catalyst layers deposited on the anode support have been operated on ethanol and air mixtures. The cells consist of gadolinia-doped ceria electrolyte, Ni-doped ceria anode, and La0.6Sr0.4CoO3-δ-doped ceria cathode. Catalyst layers with different Cu-ZnO-Al2O3 ratios are deposited and sintered at several temperatures. Since the performance of single-chamber fuel cells strongly depends on catalytic properties of electrodes for partial oxidation of ethanol, the cells are electrochemically characterized as a function of the temperature, ethanol-air molar ratio and gas flow rate. In addition, catalytic activities of supported anode, catalytic layer-supported anode and cathode for partial oxidation of ethanol are analysed. Afterwards, the effect of composition and sintering temperature of catalyst layer on the cell performance are determined. The results indicate that the cell performance can be significantly enhanced using catalyst layers of 30:35:35 and 40:30:30 wt.% Cu-ZnO-Al2O3 sintered at 1100 °C, achieving power densities above 50 mW cm-2 under 0.45 ethanol-air ratio at temperatures as low as 450 °C. After testing for 15 h, all cells present a gradual loss of power density, without carbon deposition, which is mainly attributed to the partial re-oxidation of Ni at the anode.

  9. Influence of (La,Sr)MnO3+δ cathode composition on cathode/electrolyte interfacial structure during long-term operation of solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Matsui, Toshiaki; Mikami, Yuichi; Muroyama, Hiroki; Eguchi, Koichi

    2013-11-01

    Time-dependent events during operation of SOFCs, i.e., performance enhancement and/or deterioration, can be readily observed for the cell composed of strontium-doped lanthanum manganite (LSM) cathode and yttria-stabilized zirconia (YSZ) electrolyte, concomitant with the change in interfacial structure of LSM/YSZ. The influence of LSM composition on the electrochemical properties and microstructure of LSM/YSZ interface during prolonged operation was investigated. Four different LSM cathodes were used and the change in microstructure, especially TPB-length, was evaluated quantitatively by a focused ion beam-scanning electron microscope (FIB-SEM). For LSM cathodes with A-site deficient compositions, the change in TPB-length had a minor contribution to the performance enhancement after 20 h of galvanostatic operation. On the other hand, for 100 h duration an increase in cathode overpotential was confirmed, accompanied with the formation of thin layer of LSM over YSZ electrolyte. A series of phenomena were triggered by the change in oxygen nonstoichiometry of LSM under polarized states. The mechanism for microstructural change was proposed and the long-term stability of LSM/YSZ interface was discussed.

  10. Co-flow anode/cathode supply heat exchanger for a solid-oxide fuel cell assembly

    DOEpatents

    Haltiner, Jr., Karl J.; Kelly, Sean M.

    2005-11-22

    In a solid-oxide fuel cell assembly, a co-flow heat exchanger is provided in the flow paths of the reformate gas and the cathode air ahead of the fuel cell stack, the reformate gas being on one side of the exchanger and the cathode air being on the other. The reformate gas is at a substantially higher temperature than is desired in the stack, and the cathode gas is substantially cooler than desired. In the co-flow heat exchanger, the temperatures of the reformate and cathode streams converge to nearly the same temperature at the outlet of the exchanger. Preferably, the heat exchanger is formed within an integrated component manifold (ICM) for a solid-oxide fuel cell assembly.

  11. The Effect of Cathode Composition on the Thermal Characteristics of Lithium-Ion Cells

    NASA Technical Reports Server (NTRS)

    Vaidyanathan, Hari; Rao, Gopalakrishna M.

    1999-01-01

    The specific thermal capacity and heat dissipation rate for lithium ion cells containing LiNiO2 and mixed oxide (75%LiCoO2+ 25%LiNiO2) as cathode materials are compared. The experimental measurements were made using a radiative calorimeter consisting of a copper chamber maintained at -168 C by circulating liquid nitrogen and enclosed in a vacuum bell jar. The specific thermal capacity was determined based on warm-up and cool-down transients. The heat dissipation rate was calculated from the values measured for heat radiated and stored, and the resulting values were corrected for conductive heat dissipation through the leads. The specific heat was 1.117 J/ C-g for the LiNiO2 cell and 0.946 J/ C-g for the 75%LiCoO2,25%LiNiO2 cell. Endothermic cooling at the beginning of charge was very apparent for the cell containing 75%LiCoO2,25%LiNiO2 as the cathode. Exothermic heating began at a higher state of charge for the cell with the 75%LiCoO2,25%LiNiO2 cathode compared to the LiNiO2 cathode cell. During discharge, the rate of heat dissipation increased with increase in the discharge current for both types of cells. The maximum heat dissipated at C/5 discharge was 0.065 W and 0.04 W for the LiNiO2 and 75%LiCoO2,25%LiNiO2 cells, respectively, The thermoneutral potential showed variability toward the end of discharge. The plateau region of the curves was used to calculate average thermoneutral potentials of 3.698 V and 3.837 V for the LiNiO2 cell and the 75%LiCoO2,25%LiNiO2 cell, respectively.

  12. Polypyrrole/carbon black composite as a novel oxygen reduction catalyst for microbial fuel cells

    NASA Astrophysics Data System (ADS)

    Yuan, Yong; Zhou, Shungui; Zhuang, Li

    A polypyrrole/carbon black (Ppy/C) composite has been employed as an electrocatalyst for the oxygen reduction reaction (ORR) in an air-cathode microbial fuel cell (MFC). The electrocatalytic activity of the Ppy/C is evaluated toward the oxygen reduction using cyclic voltammogram and linear sweep voltammogram methods. In comparison with that at the carbon black electrode, the peak potential of the ORR at the Pp/C electrode shifts by approximate 260 mV towards positive potential, demonstrating the electrocatalytic activity of Ppy toward ORR. Additionally, the results of the MFC experiments show that the Ppy/C is well suitable to fully substitute the traditional cathode materials in MFCs. The maximum power density of 401.8 mW m -2 obtained from the MFC with a Ppy/C cathode is higher than that of 90.9 mW m -2 with a carbon black cathode and 336.6 mW m -2 with a non-pyrolysed FePc cathode. Although the power output with a Ppy/C cathode is lower than that with a commercial Pt cathode, the power per cost of a Ppy/C cathode is 15 times greater than that of a Pt cathode. Thus, the Ppy/C can be a good alternative to Pt in MFCs due to the economic advantage.

  13. Microstructural engineering of composite cathode systems for intermediate and low-temperature solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Camaratta, Matthew

    Solid oxide fuel cells (SOFCs) are electrochemical devices with the potential to generate power at high efficiency with little environmental impact. However, in order to improve their commercial appeal, operating temperatures must be lowered from the 800-1000°C temperature range to 500-700°C and below. Due to the high bond strength of oxygen molecules, the kinetics of oxygen reduction are orders of magnitude slower than those of fuel oxidation. Consequently, much research in the reduced-temperature SOFC field is aimed at enhancing cathode performance. A composite cathode makes use of an electronic conducting phase as well as an ion conducting phase in order to spread the 3PB reaction zone beyond the cathode/electrolyte interface. Silver-stabilized bismuth oxide composite cathodes exhibit low resistance to oxygen reduction due to a combination of high catalytic activity for oxygen reduction of both phases, as well as high ionic conductivity of the bismuth oxide phase. Isothermal comparisons were made between pure silver cathodes, silver-yttrium stabilized bismuth oxide (YSB) cathodes, and silver-erbium stabilized bismuth oxides (ESB) at 650°C. The performance of all cathodes was shown to degrade with time. Cathode area specific resistance (ASR) of both the Ag-YSB and Ag-ESB electrodes increased by around 70%, while the pure Ag system experienced a near fourfold increase during the same length of time under open circuit conditions. In light of the electrochemical, microstructural, and chemical evidence presented, it was concluded that electrode microstructural evolution due to growth, agglomeration, and coalescence of the silver phase, rather than chemical reactivity of the bismuth oxide phase, was responsible for the observed degradation in electrochemical performance. Attempts were made to reduce the microstructural evolution of the silver phase in Ag-ESB20 composites by introduction of small particles (nano-size 8YSZ or vibratory-milled ESB20 particles) into

  14. High-performance cathode-supported solid oxide fuel cells with copper cermet anodes

    NASA Astrophysics Data System (ADS)

    Zhao, Lin; Ye, Xiaofeng; Zhan, Zhongliang

    2011-08-01

    Thin film solid oxide fuel cells, composed of thin coatings of 8 mol% Y2O3-stabilized ZrO2 (YSZ), thick substrates of infiltrated La0.8S0.2FeO3 (LSF)-YSZ cathodes and CuO-SDC (Ce0.85Sm0.15O1.925)-ceria anodes, are fabricated using the conventional tape casting and infiltration methods. Infiltrated LSF-YSZ cathodes exhibit a much lower interfacial polarization resistance than (La0.8Sr0.2)0.98MnO3 (LSM)-YSZ cathodes due to the mixed ionic and electronic conducting behavior of LSF, especially at low operation temperatures. The single cell has shown good and stable performance in hydrogen and hydrocarbon fuels. Maximum power densities for hydrogen, propane, dodecane and low sulfur diesel at 800 °C are 0.62 W cm-2, 0.40 W cm-2, 0.37 W cm-2 and 0.36 W cm-2, respectively.

  15. First Principles based thermo-kinetic modeling of electrocatalytic processes at fuel cell cathodes

    NASA Astrophysics Data System (ADS)

    Gadre, Milind Jayram

    Fuel Cells are promising alternative-energy technologies for the future. The design of efficient, cost-effective materials to catalyze the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is a major hurdle facing the large-scale commercialization of these technologies. Perovskites of transition metal oxides and related hetero-structures are promising, cheap materials for oxygen electro-catalysis. Understanding the detailed nature of OER and ORR catalytic activity of various surfaces of perovskite oxides can help design highly active perovskite cathodes. My research work involves first principles based thermo-kinetic modeling of various oxygen electro-catalytic processes on the surfaces of transition metal perovskites, to develop detailed mechanistic understanding of oxygen reduction/evolution reactions, and to suggest ways to engineer better cathode materials.

  16. Scaled-up dual anode/cathode microbial fuel cell stack for actual ethanolamine wastewater treatment.

    PubMed

    An, Byung-Min; Heo, Yoon; Maitlo, Hubdar-Ali; Park, Joo-Yang

    2016-06-01

    The aim of this work was to develop the scale-up microbial fuel cell technology for actual ethanolamine wastewater treatment, dual anode/cathode MFC stacks connected in series to achieve any desired current, treatment capacity, and volume capacity. However, after feeding actual wastewater into the MFC, maximum power density decreased while the corresponding internal resistance increased. With continuous electricity production, a stack of eight MFCs in series achieved 96.05% of COD removal and 97.30% of ammonia removal at a flow rate of 15.98L/d (HRT 12h). The scaled-up dual anode/cathode MFC stack system in this research was demonstrated to treat actual ETA wastewater with the added benefit of harvesting electricity energy. PMID:26888335

  17. Long-term testing and evaluation of cathode components in a commercial aluminum cell

    SciTech Connect

    Church, K.D.; Morris, E.G.; Joo', L.A. ); Stewart, D.V.; Morgan, W.R.; Tabereaux, A. )

    1990-04-01

    The purpose of modeling thermal stresses in TiB{sub 2}-G cathode elements was to aide in the design of the final TiB{sub 2}-G cathode element shape to be used in an industrial reduction cell based on knowledge of thermal stress values and an estimate of the probability of element failure. Five finite element models of four TiB{sub 2}-G cathode element shapes were constructed (Figures 1-5) to model thermal stresses resulting from step changes in temperature of 25{degree}C--960{degree}C and 300{degree}C--960{degree}C. The models were developed to represent worst case'' conditions, that is, conditions representing the greatest anticipated values of thermal stress likely to be encountered. ANSYS was used to perform the thermal stress modeling. ANSYS is a general purpose finite element code available from Swanson Analysis Systems, Incorporated. Modeling thermal stress in ANSYS for a step change in temperature requires an initial transient thermal analysis followed by a structural analysis. After the geometry of each model was defined, material properties were specified, and heat transfer boundary conditions developed. The finite element models were constructed using convective heat transfer boundary conditions as a means of specifying heat flow into the models. Convection faces and convective heat transfer coefficients were defined at the TiB{sub 2}-G -- molten metal interfaces. A uniform starting temperature of either 25{degree}C or 300{degree}C was assigned and the models were solved for transient temperature distribution and thermally induced stress. LCHEM codes were utilized to model voltage distribution and current density in reduction cells utilizing TiB{sub 2}-G cathode elements. 4 refs., 119 figs., 9 tabs.

  18. Fullerene derivative-doped zinc oxide nanofilm as the cathode of inverted polymer solar cells with low-bandgap polymer (PTB7-Th) for high performance.

    PubMed

    Liao, Sih-Hao; Jhuo, Hong-Jyun; Cheng, Yu-Shan; Chen, Show-An

    2013-09-14

    Modification of a ZnO cathode by doping it with a hydroxyl-containing derivative - giving a ZnO-C60 cathode - provides a fullerene-derivative-rich surface and enhanced electron conduction. Inverted polymer solar cells with the ZnO-C60 cathode display markedly improved power conversion efficiency compared to those with a pristine ZnO cathode, especially when the active layer includes the low-bandgap polymer PTB7-Th. PMID:23939927

  19. Modulated ionomer distribution in the catalyst layer of polymer electrolyte membrane fuel cells for high temperature operation.

    PubMed

    Choo, Min-Ju; Oh, Keun-Hwan; Kim, Hee-Tak; Park, Jung-Ki

    2014-08-01

    Ionomer distribution is an important design parameter for high performance polymer electrolyte membrane fuel cells (PEMFCs); however, the nano-scale modulation of the ionomer morphology has not been intensively explored. Here, we propose a new route to modulate the ionomer distribution that features the introduction of poly(ethylene glycol) (PEG) to the cathode catalyst layer and the leaching the PEG phase from the catalyst layer using a water effluent during operation. The key concept in the approach is the expansion of the ionomer thin film through the PEG addition. We demonstrate that the modulated ionomer distribution increases the electrochemical active area and proton transport property, without loss in oxygen transport, at a fixed ionomer content. At a high temperature of 120 °C, the power performance at 0.6 V is increased by 1.73-fold with the modulated ionomer distribution as a result of 1.25-fold increase in the electrochemical active area and two-fold increase in the proton transport rate in the catalyst layer. PMID:24777945

  20. Long-term room-temperature hydrazine/air fuel cells based on low-cost nanotextured Cu-Ni catalysts

    NASA Astrophysics Data System (ADS)

    Filanovsky, Boris; Granot, Eran; Presman, Igor; Kuras, Iliya; Patolsky, Fernando

    2014-01-01

    We present here a long-term room-temperature (RT) direct-liquid hydrazine/air fuel cell device. This hydrazine/air fuel cell is based on low-cost easily-prepared nanotextured Cu-Ni anodes as the hydrazine (Hz) catalyst, combined with a commercial anion-exchange membrane film and a commercial air cathode. In addition, our hydrazine/air fuel cell consists on an improved novel design that results in remarkably high mechanical and chemical stabilities for long periods of operation. This hydrazine/air fuel cell can operates continuously for about ∼2000 h (limited mainly by cathode and membrane deterioration) with continuous fuel supply, and supplies about 0.58 V at 1 A (14.3 mA cm-2, with a discharge efficiency of about 70% (drift is less than 0.01% h-1), and appears to be suitable for mass production. The use of optimally-combined multi-metal electrodes suggests the possibility to create novel catalysts of improved electrochemical efficiency and stability. Our fuel cell devices can find broad applications in different civilian and military field mobile and stationary uses, for instance, in future fuel-cell operated vehicles and stationary back-up power electrical stations.

  1. Fuel Cell Animation

    NASA Video Gallery

    Oxygen (O2) and hydrogen (H2) migrate into the fuel cell. The oxygen molecules migrate to the catalyst where the anode strips some of their electrons. This allows them to move through the cathode a...

  2. Theory and simulation of backbombardment in single-cell thermionic-cathode electron guns

    DOE PAGESBeta

    Edelen, J.  P.; Biedron, S.  G.; Harris, J.  R.; Milton, S.  V.; Lewellen, J.  W.

    2015-04-01

    This paper presents a comparison between simulation results and a first principles analytical model of electron back-bombardment developed at Colorado State University for single-cell, thermionic-cathode rf guns. While most previous work on back-bombardment has been specific to particular accelerator systems, this work is generalized to a wide variety of guns within the applicable parameter space. The merits and limits of the analytic model will be discussed. This paper identifies the three fundamental parameters that drive the back-bombardment process, and demonstrates relative accuracy in calculating the predicted back-bombardment power of a single-cell thermionic gun.

  3. Prediction and inhibition of molten carbonate fuel cell shorting by NiO cathode dissolution

    SciTech Connect

    Ogawa, Takashi; Nirasawa, Hitoshi; Murata, Kenji

    1995-12-31

    A model of time until shorting begins due to NiO dissolution/precipitation in MCFC was developed on the assumption that electronic conduction in the cell would happen when the concentration of dispersed nickel particles exceeded a critical value at the anode/electrolyte interface. The equation for the estimation of time-to-short-beginning (TTS) was derived as: TTS{sup 0.5}/t = A + B/K{sub Ni} pCO{sub 2} (t: matrix thickness, K{sub Ni}: NiO solubility at pCO{sub 2} = 1 atm., and A, B: constant). Life tests under different conditions on several single cells proved the usability of this equation. For the purpose of retarding MCFC shorting, a cell with a low rate of NiO dissolution, with a LiFeO{sub 2} layer, an out-of-cell oxidized NiO cathode, and a Li{sub 2}CO{sub 3}-Na{sub 2}CO{sub 3} eutectic electrolyte was made. The life test results showed that the nickel dissolution rate in the cell was less than 1/5 slower than that in the ordinary cells with an in situ oxidized NiO cathode and high Li{sub 2}CO{sub 3}-K{sub 2}CO{sub 3} eutectic electrolyte.

  4. Fabrication of biofuel cell containing enzyme catalyst immobilized by layer-by-layer method

    NASA Astrophysics Data System (ADS)

    Hyun, Kyu Hwan; Han, Sang Won; Koh, Won-Gun; Kwon, Yongchai

    2015-07-01

    Enzymatic biofuel cell (EBC) employing a layer-by-layer (LbL) structure consisting of multiple layers of glucose oxidase (GOx) and poly(ethyleneimine) (PEI) at carbon nanotube (CNT) ([GOx/PEI]n/CNT) is fabricated. The [GOx/PEI]n/CNT serves as anode catalyst for promoting glucose reaction, while Pt is employed as cathode catalyst. To evaluate effect of [GOx/PEI]n/CNT on EBC performance and stability, several characterizations are conducted. The optimal GOx/PEI layer is determined electrochemically, and it turns out that [GOx/PEI]2/CNT is the best. Electron transfer rate constant of the optimal layer is 11.3 s-1, its glucose sensitivity is 83 μAmM-1cm-2, and maximum power density of EBC adopting [GOx/PEI]2/CNT is 1.34 mWcm-2. The values are superior to those of other reference structures, indicating that the [GOx/PEI]2/CNT can produce excellent reactivity, followed by improved EBC performance. In terms of redox reaction mechanism of flavin adenine dinucleotide (FAD) within [GOx/PEI]2/CNT, glucose does not affect the redox reaction of FAD, while oxygen serves as mediator in transferring electrons and protons produced by glucose oxidation into those for reduction reaction of FAD. It is also found that the [GOx/PEI]2/CNT is confined by surface reaction and the reaction is quasi-reversible. Regarding long-term stability, [GOx/PEI]2/CNT maintains ∼83% of initial activity even after two weeks.

  5. Continuum and Quantum-Chemical Modeling of Oxygen Reduction on the Cathode in a Solid Oxide Fuel Cell

    SciTech Connect

    Choi, Yongman; Mebane, David S.; Wang, Jeng-Han; Liu, Meilin

    2009-10-08

    Solid oxide fuel cells (SOFCs) have several advantages over other types of fuels cells such as high-energy efficiency and excellent fuel flexibility. To be economically competitive, however, new materials with extraordinary transport and catalytic properties must be developed to dramatically improve the performance while reducing the cost. This article reviews recent advancements in understanding oxygen reduction on various cathode materials using phenomenological and quantum chemical approaches in order to develop novel cathode materials with high catalytic activity toward oxygen reduction. We summarize a variety of results relevant to understanding the interactions between O2 and cathode materials at the molecular level as predicted using quantum-chemical cal-culations and probed using in situ surface vibrational spectroscopy. It is hoped that this in-depth understanding may provide useful insights into the design of novel cath-ode materials for a new generation of SOFCs.

  6. Acidic and alkaline pretreatments of activated carbon and their effects on the performance of air-cathodes in microbial fuel cells.

    PubMed

    Wang, Xin; Gao, Ningshengjie; Zhou, Qixing; Dong, Heng; Yu, Hongbing; Feng, Yujie

    2013-09-01

    Activated carbon (AC) is a high performing and cost effective catalyst for oxygen reduction reactions (ORRs) of air-cathodes in microbial fuel cells (MFCs). Acidic (HNO3) and alkaline (KOH) pretreatments on AC at low temperature (85°C) are conducted to enhance the performance of MFCs. The alkaline pretreatment increased the power density by 16% from 804±70 to 957±31 mW m(-2), possibly due to the decrease of ohmic resistance (from 20.58 to 19.20 Ω) and the increase of ORR activities provided by the adsorbed hydroxide ion and extra micropore area/volume after alkaline pretreatment. However, acidic pretreatment decreased the power output to 537±36 mW m(-2), which can be mainly attributed to the corrosion by adsorbed proton at the interface of AC powder and stainless steel mesh and the decreased pore area. PMID:23890977

  7. XRD and Mössbauer studies on Pt Fe nano-particles synthesized by polyol method for cathode catalyst of PEFCS

    NASA Astrophysics Data System (ADS)

    Toriyama, T.; Kawahara, N.; Maeda, Y.; Suruga, T.; Wakabayashi, H.; Takagi, Y.

    2008-04-01

    Pt50 Fe50 nanoparticles were synthesized by the chemically wet process for developing a new high efficiency cathode catalyst in PEFCs. The particle morphology and crystal structure of as synthesized Pt Fe particles, and electronic state of Fe atoms in them were evaluated using transmission electron microscopy(TEM), X-ray diffraction(XRD) and transmission Mössbauer spectroscopy (TMS), respectively. They are confirmed to be of chemically disordered fcc structure from XRD pattern and the average diameter of them was estimated to be 3.1 nm from both TEM and the width of (111) peak in XRD pattern. From TMS spectrum, it was concluded to consist of mainly the component of Fe oxides connected with the organic ligands according to XPS results mentioned below. But, probably it contains the component for superparamagnetic Pt Fe nanoparticles. Also the electrocatalytic activity and a hydrogen adsorption/desorption behavior for as synthesized Pt Fe nanoparticles was observed by cyclic voltammetry and the oxidation of Fe atoms in as synthesized Pt Fe nanoparticles, Fe metal and Fe oxides were measured.

  8. Enhanced Salt Removal in an Inverted Capacitive Deionization Cell Using Amine Modified Microporous Carbon Cathodes.

    PubMed

    Gao, Xin; Omosebi, Ayokunle; Landon, James; Liu, Kunlei

    2015-09-15

    Microporous SpectraCarb carbon cloth was treated using nitric acid to enhance negative surface charges of COO(-) in a neutral solution. This acid-treated carbon was further modified by ethylenediamine to attach -NH2 surface functional groups, resulting in positive surface charges of -NH3(+) via pronation in a neutral solution. Through multiple characterizations, in comparison to pristine SpectraCarb carbon, amine-treated SpectraCarb carbon displays a decreased potential of zero charge but an increased point of zero charge, which is opposed to the effect obtained for acid-treated SpectraCarb carbon. An inverted capacitive deionization cell was constructed using amine-treated cathodes and acid-treated anodes, where the cathode is the negatively polarized electrode and the anode is the positively polarized electrode. Constant-voltage switching operation using NaCl solution showed that the salt removal capacity was approximately 5.3 mg g(-1) at a maximum working voltage of 1.1/0 V, which is an expansion in both the salt capacity and potential window from previous i-CDI results demonstrated for carbon xerogel materials. This improved performance is accounted for by the enlarged cathodic working voltage window through ethylenediamine-derived functional groups, and the enhanced microporosity of the SpectraCarb electrodes for salt adsorption. These results expand the use of i-CDI for efficient desalination applications. PMID:26302134

  9. Glass-containing composite cathode contact materials for solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Tucker, Michael C.; Cheng, Lei; DeJonghe, Lutgard C.

    2011-10-01

    The feasibility of adding glass to conventional SOFC cathode contact materials in order to improve bonding to adjacent materials in the cell stack is assessed. A variety of candidate glass compositions are added to LSM and SSC. The important properties of the resulting composites, including conductivity, sintering behavior, coefficient of thermal expansion, and adhesion to LSCF and Mn1.5Co1.5O4-coated 441 stainless steel are used as screening parameters. Adhesion of LSM to LSCF improved from 3.9 to 5.3 MPa upon addition of SCZ-8 glass. Adhesion of LSM to coated stainless steel improved from 1.8 to 3.9 MPa upon addition of Schott GM31107 glass. The most promising cathode contact material/glass composites are coated onto Mn1.5Co1.5O4-coated 441 stainless steel substrates and subjected to area-specific resistance testing at 800 °C. In all cases, area-specific resistance is found to be in the range 2.5-7.5 mOhm cm2 and therefore acceptable. Indeed, addition of glass is found to improve bonding of the cathode contact material layer without sacrificing acceptable conductivity.

  10. Ag/C nanoparticles as an cathode catalyst for a zinc-air battery with a flowing alkaline electrolyte

    NASA Astrophysics Data System (ADS)

    Han, Jia-Jun; Li, Ning; Zhang, Tian-Yun

    The cyclic voltammetry indicated that the oxygen reduction reaction (ORR) proceeded by the four-electron pathway mechanism on larger Ag particles (174 nm), and that the ORR proceeded by the four-electron pathway and the two-electron pathway mechanisms on finer Ag particles (4.1 nm), simultaneously. The kinetics towards ORR was measured at a rotating disk electrode (RDE) with Ag/C electrode. The number of exchanged electrons for the ORR was found to be close to four on larger Ag particles (174 nm) and close to three on finer Ag particles (4.1 nm). The zinc-air battery with Ag/C catalysts (25.9 nm) was fabricated and examined.

  11. Lightweight Cathodes For Nickel Batteries

    NASA Technical Reports Server (NTRS)

    Britton, Doris L.

    1996-01-01

    Lightweight cathodes for rechargeable nickel-based electrochemical cells undergoing development. In cathodes, mats of nickel fibers are substrates providing structural support of, and electrical contact with, active cathode material. Offers specific energies greater than sintered nickel plaque cathodes. Electrodes used in rechargeable batteries for applications in which weight major concern, including laptop computers, cellular phones, flashlights, soldiers' backpacks, and electric vehicles.

  12. Analysis of liquid water formation in polymer electrolyte membrane (PEM) fuel cell flow fields with a dry cathode supply

    NASA Astrophysics Data System (ADS)

    Gößling, Sönke; Klages, Merle; Haußmann, Jan; Beckhaus, Peter; Messerschmidt, Matthias; Arlt, Tobias; Kardjilov, Nikolay; Manke, Ingo; Scholta, Joachim; Heinzel, Angelika

    2016-02-01

    PEM fuel cells can be operated within a wide range of different operating conditions. In this paper, the special case of operating a PEM fuel cell with a dry cathode supply and without external humidification of the cathode, is considered. A deeper understanding of the water management in the cells is essential for choosing the optimal operation strategy for a specific system. In this study a theoretical model is presented which aims to predict the location in the flow field at which liquid water forms at the cathode. It is validated with neutron images of a PEM fuel cell visualizing the locations at which liquid water forms in the fuel cell flow field channels. It is shown that the inclusion of the GDL diffusion resistance in the model is essential to describe the liquid water formation process inside the fuel cell. Good agreement of model predictions and measurement results has been achieved. While the model has been developed and validated especially for the operation with a dry cathode supply, the model is also applicable to fuel cells with a humidified cathode stream.

  13. Electricity generation and bivalent copper reduction as a function of operation time and cathode electrode material in microbial fuel cells

    NASA Astrophysics Data System (ADS)

    Wu, Dan; Huang, Liping; Quan, Xie; Li Puma, Gianluca

    2016-03-01

    The performance of carbon rod (CR), titanium sheet (TS), stainless steel woven mesh (SSM) and copper sheet (CS) cathode materials are investigated in microbial fuel cells (MFCs) for simultaneous electricity generation and Cu(II) reduction, in multiple batch cycle operations. After 12 cycles, the MFC with CR exhibits 55% reduction in the maximum power density and 76% increase in Cu(II) removal. In contrast, the TS and SSM cathodes at cycle 12 show maximum power densities of 1.7 (TS) and 3.4 (SSM) times, and Cu(II) removal of 1.2 (TS) and 1.3 (SSM) times higher than those observed during the first cycle. Diffusional resistance in the TS and SSM cathodes is found to appreciably decrease over time due to the copper deposition. In contrast to CR, TS and SSM, the cathode made with CS is heavily corroded in the first cycle, exhibiting significant reduction in both the maximum power density and Cu(II) removal at cycle 2, after which the performance stabilizes. These results demonstrate that the initial deposition of copper on the cathodes of MFCs is crucial for efficient and continuous Cu(II) reduction and electricity generation over prolonged time. This effect is closely associated with the nature of the cathode material. Among the materials examined, the SSM is the most effective and inexpensive cathode for practical use in MFCs.

  14. Development of membrane electrode assembly for high temperature proton exchange membrane fuel cell by catalyst coating membrane method

    NASA Astrophysics Data System (ADS)

    Liang, Huagen; Su, Huaneng; Pollet, Bruno G.; Pasupathi, Sivakumar

    2015-08-01

    Membrane electrode assembly (MEA), which contains cathode and anode catalytic layer, gas diffusion layers (GDL) and electrolyte membrane, is the key unit of a PEMFC. An attempt to develop MEA for ABPBI membrane based high temperature (HT) PEMFC is conducted in this work by catalyst coating membrane (CCM) method. The structure and performance of the MEA are examined by scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS) and I-V curve. Effects of the CCM preparation method, Pt loading and binder type are investigated for the optimization of the single cell performance. Under 160 °C and atmospheric pressure, the peak power density of the MEA, with Pt loading of 0.5 mg cm-2 and 0.3 mg cm-2 for the cathode and the anode, can reach 277 mW cm-2, while a current density of 620 A cm-2 is delivered at the working voltage of 0.4 V. The MEA prepared by CCM method shows good stability operating in a short term durability test: the cell voltage maintained at ∼0.45 V without obvious drop when operated at a constant current density of 300 mA cm-2 and 160 °C under ambient pressure for 140 h.

  15. Degradation mechanisms of Platinum Nanoparticle Catalysts in Proton Exchange Membrane Fuel Cells: The Role of Particle Size

    SciTech Connect

    Yu, Kang; Groom, Daniel J.; Wang, Xiaoping; Yang, Zhiwei; Gummalla, Mallika; Ball, Sarah C.; Myers, Deborah J.; Ferreira, Paulo J.

    2014-10-14

    Five membrane-electrode assemblies (MEAs) with different average sizes of platinum (Pt) nanoparticles (2.2, 3.5, 5.0, 6.7, and 11.3 nm) in the cathode were analyzed before and after potential cycling (0.6 to 1.0 V, 50 mV/s) by transmission electron microscopy. Cathodes loaded with 2.2 nm and 3.5 nm catalyst nanoparticles exhibit the following changes during electrochemical cycling: (i) substantial broadening of the size distribution relative to the initial size distribution, (ii) presence of coalesced particles within the electrode, and (iii) precipitation of sub-micron-sized particles with complex shapes within the membrane. In contrast, cathodes loaded with 5.0 nm, 6.7 nm and 11.3 nm size catalyst nanoparticles are significantly less prone to the aforementioned effects. As a result, the electrochemically-active surface area (ECA) of MEA cathodes loaded with 2.2 nm and 3.5 nm nanoparticle catalysts degrades dramatically within 1,000 cycles of operation, while the electrochemically-active surface area of MEA cathodes loaded with 5.0 nm, 6.7 nm and 11.3 nm nanoparticle catalysts appears to be stable even after 10,000 cycles. The loss in MEA performance for cathodes loaded with 2.2 nm and 3.5 nm nanoparticle catalysts appears to be due to the loss in electrochemically-active surface area concomitant with the observed morphological changes in these nanoparticle catalysts

  16. Performance and durability of carbon black-supported Pd catalyst covered with silica layers in membrane-electrode assemblies of proton exchange membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Fujii, Keitaro; Ito, Mizuki; Sato, Yasushi; Takenaka, Sakae; Kishida, Masahiro

    2015-04-01

    Pd metal particles supported on a high surface area carbon black (Pd/CB) were covered with silica layers to improve the durability under severe cathode condition of proton exchange membrane fuel cells (PEMFCs). The performance and the durability of the silica-coated Pd/CB (SiO2/Pd/CB) were investigated by rotating disk electrode (RDE) in aqueous HClO4 and single cell test of the membrane-electrode assemblies (MEAs). SiO2/Pd/CB showed excellent durability exceeding Pt/CB during potential cycle in single cell test as well as in RDE measurement while Pd/CB significantly degraded. Furthermore, the MEA using SiO2/Pd/CB as the cathode catalyst showed higher performance than that using Pd/CB even in the initial state. The catalytic activity of SiO2/Pd/CB was higher than that of Pd/CB, and the drop of the cell performances due to the inhibition of electron conduction, proton conduction, and oxygen diffusion by the silica layer was not significant. It has been shown that the silica-coating is a very practical technique that can stabilize metal species originally unstable in the cathode condition of PEMFCs without a decrease in the cell performance.

  17. The water catalysis at oxygen cathodes of lithium–oxygen cells

    PubMed Central

    Li, Fujun; Wu, Shichao; Li, De; Zhang, Tao; He, Ping; Yamada, Atsuo; Zhou, Haoshen

    2015-01-01

    Lithium–oxygen cells have attracted extensive interests due to their high theoretical energy densities. The main challenges are the low round-trip efficiency and cycling instability over long time. However, even in the state-of-the-art lithium–oxygen cells the charge potentials are as high as 3.5 V that are higher by 0.70 V than the discharge potentials. Here we report a reaction mechanism at an oxygen cathode, ruthenium and manganese dioxide nanoparticles supported on carbon black Super P by applying a trace amount of water in electrolytes to catalyse the cathode reactions of lithium–oxygen cells during discharge and charge. This can significantly reduce the charge overpotential to 0.21 V, and results in a small discharge/charge potential gap of 0.32 V and superior cycling stability of 200 cycles. The overall reaction scheme will alleviate side reactions involving carbon and electrolytes, and shed light on the construction of practical, rechargeable lithium–oxygen cells. PMID:26206379

  18. Miniature fuel cell with monolithically fabricated Si electrodes - Alloy catalyst formation -

    NASA Astrophysics Data System (ADS)

    Ogura, Daiki; Suzuki, Takahiro; Katayama, Noboru; Dowaki, Kiyoshi; Hayase, Masanori

    2013-12-01

    A novel Pd-Pt catalyst formation process was proposed for reduction of Pt usage. In our miniature fuel cells, porous Pt was used as the catalyst, and the Pt usage was quite high. To reduce the Pt usage, we have attempted to deposit Pt on porous Pd by galvanic replacement, and relatively large output was demonstrated. In this study, in order to reduce more Pt usage and explore the alloy catalyst formation process, atomic layer deposition by UPD-SLRR (Under Potential Deposition - Surface Limited Redox Replacement) was applied to the Pd-Pt catalyst formation. The new process was verified at each process steps by EDS elemental analysis, and the expected spectra were obtained. Prototype cells were constructed by the new process, and cell output was raised to 420mW/cm2 by the Pd-Pt catalyst from 125mW/cm2 with Pd catalyst.

  19. Method for producing electricity using a platinum-ruthenium-palladium catalyst in a fuel cell

    DOEpatents

    Gorer, Alexander

    2004-01-27

    A method for producing electricity using a fuel cell that utilizes a ternary alloy composition as a fuel cell catalyst, the ternary alloy composition containing platinum, ruthenium and palladium. The alloy shows increased activity as compared to well-known catalysts.

  20. Theory, Investigation and Stability of Cathode Electrocatalytic Activity

    SciTech Connect

    Ding, Dong; Liu, Mingfei; Lai, Samson; Blinn, Kevin; Liu, Meilin

    2012-09-30

    The main objective of this project is to systematically characterize the surface composition, morphology, and electro-catalytic properties of catalysts coated on LSCF, aiming to establish the scientific basis for rational design of high-performance cathodes by combining a porous backbone (such as LSCF) with a thin catalyst coating. The understanding gained will help us to optimize the composition and morphology of the catalyst layer and microstructure of the LSCF backbone for better performance. More specifically, the technical objectives include: (1) to characterize the surface composition, morphology, and electro-catalytic properties of catalysts coated on LSCF; (2) to characterize the microscopic details and stability of the LSCF-catalyst (e.g., LSM) interfaces; (3) to establish the scientific basis for rational design of high-performance cathodes by combining a porous backbone (such as LSCF) with a thin catalyst coating; and (4) to demonstrate that the performance and stability of porous LSCF cathodes can be enhanced by the application of a thin-film coating of LSM through a solution infiltration process in small homemade button cells and in commercially available cells of larger dimension. We have successfully developed dense, conformal LSM films with desired structure, composition, morphology, and thickness on the LSCF surfaces by two different infiltration processes: a non-aqueous and a water-based sol-gel process. It is demonstrated that the activity and stability of LSCF cathodes can be improved by the introduction of a thin-film LSM coating through an infiltration process. Surface and interface of the LSM-coated LSCF cathode were systematically characterized using advanced microscopy and spectroscopy techniques. TEM observation suggests that a layer of La and Sr oxide was formed on LSCF surfaces after annealing. With LSM infiltration, in contrast, we no longer observe such La/Sr oxide layer on the LSM-coated LSCF samples after annealing under similar

  1. 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

    2016-08-01

    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. PMID:27376964

  2. OPTIMIZATION OF THE CATHODE LONG-TERM STABILITY IN MOLTEN CARBONATE FUEL CELLS: EXPERIMENTAL STUDY AND MATHEMATICAL MODELING

    SciTech Connect

    Dr. Ralph E. White

    2000-09-30

    The dissolution of NiO cathodes during cell operation is a limiting factor to the successful commercialization of molten carbonate fuel cells (MCFCs). Microencapsulation of the NiO cathode has been adopted as a surface modification technique to increase the stability of NiO cathodes in the carbonate melt. The material used for surface modification should possess thermodynamic stability in the molten carbonate and also should be electro catalytically active for MCFC reactions. A simple first principles model was developed to understand the influence of exchange current density and conductivity of the electrode material on the polarization of MCFC cathodes. The model predictions suggest that cobalt can be used to improve the corrosion resistance of NiO cathode without affecting its performance. Cobalt was deposited on NiO cathode by electroless deposition. The morphology and thermal oxidation behavior of Co coated NiO was studied using scanning electron microscopy and thermal gravimetric analysis respectively. The electrochemical performance of cobalt encapsulated NiO cathodes were investigated with open circuit potential measurement and current-potential polarization studies. These results were compared to that of bare NiO. The electrochemical oxidation behavior of cobalt-coated electrodes is similar to that of the bare NiO cathode. Dissolution of nickel into the molten carbonate melt was less in case of cobalt encapsulated nickel cathodes. Co coated on the surface prevents the dissolution of Ni in the melt and thereby stabilizes the cathode. Finally, cobalt coated nickel shows similar polarization characteristics as nickel oxide. A similar surface modification technique has been used to improve the performance of the SS 304 current collectors used in MCFC cells. SS 304 was encapsulated with nanostructured layers of NiCo and NiMo by electroless deposition. The corrosion behavior of bare and surface modified SS 304 in molten carbonate under cathode gas atmosphere was

  3. Particle-in-cell based parameter study of 12-cavity, 12-cathode rising-sun relativistic magnetrons for improved performance

    NASA Astrophysics Data System (ADS)

    Majzoobi, A.; Joshi, R. P.; Neuber, A. A.; Dickens, J. C.

    2015-10-01

    Particle-in-cell simulations are performed to analyze the efficiency, output power and leakage currents in a 12-Cavity, 12-Cathode rising-sun magnetron with diffraction output (MDO). The central goal is to conduct a parameter study of a rising-sun magnetron that comprehensively incorporates performance enhancing features such as transparent cathodes, axial extraction, the use of endcaps, and cathode extensions. Our optimum results demonstrate peak output power of about 2.1 GW, with efficiencies of ˜70% and low leakage currents at a magnetic field of 0.45 Tesla, a 400 kV bias with a single endcap, for a range of cathode extensions between 3 and 6 centimeters.

  4. Particle-in-cell based parameter study of 12-cavity, 12-cathode rising-sun relativistic magnetrons for improved performance

    SciTech Connect

    Majzoobi, A.; Joshi, R. P. Neuber, A. A.; Dickens, J. C.

    2015-10-15

    Particle-in-cell simulations are performed to analyze the efficiency, output power and leakage currents in a 12-Cavity, 12-Cathode rising-sun magnetron with diffraction output (MDO). The central goal is to conduct a parameter study of a rising-sun magnetron that comprehensively incorporates performance enhancing features such as transparent cathodes, axial extraction, the use of endcaps, and cathode extensions. Our optimum results demonstrate peak output power of about 2.1 GW, with efficiencies of ∼70% and low leakage currents at a magnetic field of 0.45 Tesla, a 400 kV bias with a single endcap, for a range of cathode extensions between 3 and 6 centimeters.

  5. Mesoporous CuCo2O4 nanoparticles as an efficient cathode catalyst for Li-O2 batteries

    NASA Astrophysics Data System (ADS)

    Wang, Peng-Xiang; Shao, Lin; Zhang, Nai-Qing; Sun, Ke-Ning

    2016-09-01

    Extremely high energy density and environment friendly reaction make Li-O2 batteries a promising energy storage system. In order to improve the energy efficiency and cycle life of Li-O2 battery, spinel mesoporous CuCo2O4 was successfully synthesized by a facile hydrothermal method and investigated in Li-O2 batteries. The electrochemical measurements show that mesoporous CuCo2O4 possess higher oxygen reduction and oxygen evolution activity than bulk CuCo2O4 both in alkaline and non-aqueous solution. Owing to the inherent catalytic activity, high conductivity and facile mass transfer of mesoporous CuCo2O4, Li-O2 battery shows enhanced electrochemical performances, including much lower charge overpotential and a high capacity up to 5288 mAh g-1. When restricting the discharge capacity at 500 mAh g-1, it could operate over 80 cycles and exhibit superior cycle stability. These results indicate that mesoporous CuCo2O4 nanoparticles are appropriate bifunctional catalysts for Li-O2 batteries.

  6. Stabilizing platinum in phosphoric acid fuel cells

    NASA Technical Reports Server (NTRS)

    Remick, R. J.

    1982-01-01

    Platinum sintering on phosphoric acid fuel cell cathodes is discussed. The cathode of the phosphoric acid fuel cell uses a high surface area platinum catalyst dispersed on a conductive carbon support to minimize both cathode polarization and fabrication costs. During operation, however, the active surface area of these electrodes decreases, which in turn leads to decreased cell performance. This loss of active surface area is a major factor in the degradation of fuel cell performance over time.

  7. New Catalysts for Direct Methanol Oxidation Fuel Cells

    SciTech Connect

    Adzic, Radoslav

    1998-08-01

    A new class of efficient electrocatalytic materials based on platinum - metal oxide systems has been synthetized and characterized by several techniques. Best activity was found with NiWO{sub 4}-, CoWO{sub 4}-, and RuO{sub 2}- sr¡pported platinum catalysts. A very similar activity at room temperature was observed with the electrodes prepared with the catalyst obtained from International Fuel Cells Inc. for the same Pt loading. Surprisingly, the two tungstates per se show a small activity for methanol oxidation without any Pt loading. Synthesis of NiWO{sub 4} and CoWO{sub 4} were carried out by solid-state reactions. FTIR spectroscopy shows that the tungstates contain a certain amount of physically adsorbed water even after heating samples at 200{degrees}C. A direct relationship between the activity for methanol oxidation and the amount of adsorbed water on those oxides has been found. The Ru(0001) single crystal shows a very small activity for CO adsorption and oxidation, in contrast to the behavior of polycrystalline Ru. In situ extended x-ray absorption fine structure spectroscopy (EXAFS) and x-ray absorption near edge spectroscopy (XANES) showed that the OH adsorption on Ru in the Pt-Ru alloy appears to be the limiting step in methanol oxidation. This does not occur for Pt-RuO{SUB 2} electrocatalyst, which explains its advantages over the Pt-Ru alloys. The IFCC electrocatalyst has the properties of the Pt-Ru alloy.

  8. Spray-on polyvinyl alcohol separators and impact on power production in air-cathode microbial fuel cells with different solution conductivities.

    PubMed

    Hoskins, Daniel L; Zhang, Xiaoyuan; Hickner, Michael A; Logan, Bruce E

    2014-11-01

    Separators are used to protect cathodes from biofouling and to avoid electrode short-circuiting, but they can adversely affect microbial fuel cell (MFC) performance. A spray method was used to apply a polyvinyl alcohol (PVA) separator to the cathode. Power densities were unaffected by the PVA separator (339±29mW/m(2)), compared to a control lacking a separator in a low conductivity solution (1mS/cm) similar to wastewater. Power was reduced with separators in solutions typical of laboratory tests (7-13mS/cm), compared to separatorless controls. The PVA separator produced more power in a separator assembly (SEA) configuration (444±8mW/m(2)) in the 1mS/cm solution, but power was reduced if a PVA or wipe separator was used in higher conductivity solutions with either Pt or activated carbon catalysts. Spray and cast PVA separators performed similarly, but the spray method is preferred as it was easier to apply and use. PMID:25260178

  9. Particle-in-cell simulations for virtual cathode oscillator including foil ablation effects

    NASA Astrophysics Data System (ADS)

    Singh, Gursharn; Chaturvedi, S.

    2011-06-01

    We have performed two- and three-dimensional, relativistic, electromagnetic, particle-in-cell simulations of an axially extracted virtual cathode oscillator (vircator). The simulations include, for the first time, self-consistent dynamics of the anode foil under the influence of the intense electron beam. This yields the variation of microwave output power as a function of time, including the role of anode ablation and anode-cathode gap closure. These simulations have been done using locally developed particle-in-cell (PIC) codes. The codes have been validated using two vircator designs available from the literature. The simulations reported in the present paper take account of foil ablation due to the intense electron flux, the resulting plasma expansion and shorting of the anode-cathode gap. The variation in anode transparency due to plasma formation is automatically taken into account. We find that damage is generally higher near the axis. Also, at all radial positions, there is little damage in the early stages, followed by a period of rapid erosion, followed in turn by low damage rates. A physical explanation has been given for these trends. As a result of gap closure due to plasma formation from the foil, the output microwave power initially increases, reaches a near-flat-top and then decreases steadily, reaching a minimum around 230 ns. This is consistent with a typical plasma expansion velocity of ˜2 cm/μs reported in the literature. We also find a significant variation in the dominant output frequency, from 6.3 to 7.6 GHz. This variation is small as long as the plasma density is small, up to ˜40 ns. As the AK gap starts filling with plasma, there is a steady increase in this frequency.

  10. Compatibility between strontium-doped ferrite cathode and metallic interconnects in solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Miguel-Pérez, Verónica; Martínez-Amesti, Ana; Arriortua, María Isabel

    2015-04-01

    One of the most important issues related to the performance of solid oxide fuel cells (SOFCs) is the chromium poisoning of the perovskite-type materials used as cathodes by the gaseous chromium species from metallic interconnects. In this study, powder mixtures of LSF40-Cr2O3 were heated at 800 °C and 1000 °C in air and were subsequently analysed by X-ray powder diffraction. For all the mixtures, the crystallisation of SrCrO4 was observed. In addition, the degradation occurring between three alloys with different compositions, Crofer 22 APU, SS430 and Conicro 4023 W 188, as metallic interconnects and La0.6Sr0.4FeO3 (LSF40) ceramic material as a cathode was studied. The results show significant chromium deposition and the formation of SrCrO4, LaCrO3 and La2O3 that block the active LSF40 electrode surface and degrade the stack (YSZ/SDC/LSF40/Interconnect) performance. LSF40 assembled with SS430 exhibited substantial Cr deposition. The deposition of the Cr species and the reaction with the LSF40 cathode is related to the composition of the oxide scales formed at each metallic interconnect and at the same time is related to the composition of the alloys. The best results obtained were for the half-cell (YSZ/SDC/LSF40) in contact with Conicro 4023 W 188 and Crofer 22 APU after heat treatment in air at 800 °C for 100 h.

  11. Enhanced oxygen reduction activity and solid oxide fuel cell performance with a nanoparticles-loaded cathode.

    PubMed

    Zhang, Xiaomin; Liu, Li; Zhao, Zhe; Tu, Baofeng; Ou, Dingrong; Cui, Daan; Wei, Xuming; Chen, Xiaobo; Cheng, Mojie

    2015-03-11

    Reluctant oxygen-reduction-reaction (ORR) activity has been a long-standing challenge limiting cell performance for solid oxide fuel cells (SOFCs) in both centralized and distributed power applications. We report here that this challenge has been tackled with coloading of (La,Sr)MnO3 (LSM) and Y2O3 stabilized zirconia (YSZ) nanoparticles within a porous YSZ framework. This design dramatically improves ORR activity, enhances fuel cell output (200-300% power improvement), and enables superior stability (no observed degradation within 500 h of operation) from 600 to 800 °C. The improved performance is attributed to the intimate contacts between nanoparticulate YSZ and LSM particles in the three-phase boundaries in the cathode. PMID:25686380

  12. Microbial fuel cell using anaerobic respiration as an anodic reaction and biomineralized manganese as a cathodic reactant.

    PubMed

    Rhoads, Allison; Beyenal, Haluk; Lewandowski, Zbigniew

    2005-06-15

    We have operated a microbial fuel cell in which glucose was oxidized by Klebsiella pneumoniae in the anodic compartment, and biomineralized manganese oxides, deposited by Leptothrix discophora, were electrochemically reduced in the cathodic compartment. In the anodic compartment, to facilitate the electron transfer from glucose to the graphite electrode, we added a redox mediator, 2-hydroxy-1,4-naphthoquinone. We did not add any redox mediator to the cathodic compartment because the biomineralized manganese oxides were deposited on the surface of a graphite electrode and were reduced directly by electrons from the electrode. We have demonstrated that biomineralized manganese oxides are superiorto oxygen when used as cathodic reactants in microbial fuel cells. The current density delivered by using biomineralized manganese oxides as the cathodic reactant was almost 2 orders of magnitude higher than that delivered using oxygen. Several fuel cells were operated for 500 h, reaching anodic potentials of -441.5 +/- 31 mVscE and cathodic potentials of +384.5 +/- 64 mVscE. When the electrodes were connected by a 50 Ohms resistor, the fuel cell delivered the peak power density of 126.7 +/- 31.5 mW/m2. PMID:16047807

  13. Modeling the cathode pressure dynamics in the Buckeye Bullet II 540 kW hydrogen PEM fuel cell system

    NASA Astrophysics Data System (ADS)

    Hillstrom, Edward T.; Canova, Marcello; Guezennec, Yann; Rizzoni, Giorgio

    2013-11-01

    The Buckeye Bullet 2 (BB2) is the world's fastest hydrogen fuel cell vehicle, with an international speed record of 302.9 mph. In order to achieve the power levels necessary for reaching the top speed, a unique gas supply system was designed to feed the PEM fuel cell modules. Stored Heliox with 40% oxygen content was used as the oxidizer and supplied to the cathode at high pressure. The high oxygen concentration at the cathode leads to a high rate of water formation in the GDL, with considerable influence on the pressure dynamics. For this reason, a precise monitoring of the pressure and water formation is required so that the cathode can operate at the maximum allowable pressure. This paper presents a novel control-oriented modeling approach to predict the cathode pressure dynamics of the BB2 PEM fuel cell system, developed for system optimization, monitoring and control. A distributed-parameter model was designed to characterize the liquid water formation and transport in the cathode channels, starting from the conservation laws for viscous fluid flow. The model was validated against a set of laboratory tests and actual race data. In this context, the proposed model is compared to a well known control-oriented PEM fuel cell model, to illustrate how the ability to predict the water transport at high reaction rates allows for an improved prediction of the pressure dynamics.

  14. Metal catalyst technique for texturing silicon solar cells

    DOEpatents

    Ruby, Douglas S.; Zaidi, Saleem H.

    2001-01-01

    Textured silicon solar cells and techniques for their manufacture utilizing metal sources to catalyze formation of randomly distributed surface features such as nanoscale pyramidal and columnar structures. These structures include dimensions smaller than the wavelength of incident light, thereby resulting in a highly effective anti-reflective surface. According to the invention, metal sources present in a reactive ion etching chamber permit impurities (e.g. metal particles) to be introduced into a reactive ion etch plasma resulting in deposition of micro-masks on the surface of a substrate to be etched. Separate embodiments are disclosed including one in which the metal source includes one or more metal-coated substrates strategically positioned relative to the surface to be textured, and another in which the walls of the reaction chamber are pre-conditioned with a thin coating of metal catalyst material.

  15. 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. PMID:25227449

  16. Chlorobenzene Poisoning and Recovery of Platinum-Based Cathodes in Proton Exchange Membrane Fuel Cells

    PubMed Central

    Zhai, Yunfeng; Baturina, Olga; Ramaker, David; Farquhar, Erik; St-Pierre, Jean; Swider-Lyons, Karen

    2015-01-01

    The platinum electrocatalysts found in proton exchange membrane fuel cells are poisoned both reversibly and irreversibly by air pollutants and residual manufacturing contaminants. In this work, the poisoning of a Pt/C PEMFC cathode was probed by a trace of chlorobenzene in the air feed. Chlorobenzene inhibits the oxygen reduction reaction and causes significant cell performance loss. The performance loss is largely restored by neat air operation and potential cycling between 0.08 V and 1.2 V under H2/N2 (anode/cathode). The analysis of emissions, in situ X-ray absorption spectroscopy and electrochemical impedance spectra show the chlorobenzene adsorption/reaction and molecular orientation on Pt surface depend on the electrode potential. At low potentials, chlorobenzene deposits either on top of adsorbed H atoms or on the Pt surface via the benzene ring and is converted to benzene (ca. 0.1 V) or cyclohexane (ca. 0 V) upon Cl removal. At potentials higher than 0.2 V, chlorobenzene binds to Pt via the Cl atom and can be converted to benzene (less than 0.3 V) or desorbed. Cl− is created and remains in the membrane electrode assembly. Cl− binds to the Pt surface much stronger than chlorobenzene, but can slowly be flushed out by liquid water. PMID:26388963

  17. Modeling of thermal expansion coefficient of perovskite oxide for solid oxide fuel cell cathode

    NASA Astrophysics Data System (ADS)

    Heydari, F.; Maghsoudipour, A.; Alizadeh, M.; Khakpour, Z.; Javaheri, M.

    2015-09-01

    Artificial intelligence models have the capacity to eliminate the need for expensive experimental investigation in various areas of manufacturing processes, including the material science. This study investigates the applicability of adaptive neuro-fuzzy inference system (ANFIS) approach for modeling the performance parameters of thermal expansion coefficient (TEC) of perovskite oxide for solid oxide fuel cell cathode. Oxides (Ln = La, Nd, Sm and M = Fe, Ni, Mn) have been prepared and characterized to study the influence of the different cations on TEC. Experimental results have shown TEC decreases favorably with substitution of Nd3+ and Mn3+ ions in the lattice. Structural parameters of compounds have been determined by X-ray diffraction, and field emission scanning electron microscopy has been used for the morphological study. Comparison results indicated that the ANFIS technique could be employed successfully in modeling thermal expansion coefficient of perovskite oxide for solid oxide fuel cell cathode, and considerable savings in terms of cost and time could be obtained by using ANFIS technique.

  18. Bismuth doped lanthanum ferrite perovskites as novel cathodes for intermediate-temperature solid oxide fuel cells.

    PubMed

    Li, Mei; Wang, Yao; Wang, Yunlong; Chen, Fanglin; Xia, Changrong

    2014-07-23

    Bismuth is doped to lanthanum strontium ferrite to produce ferrite-based perovskites with a composition of La(0.8-x)Bi(x)Sr0.2FeO(3-δ) (0 ≤ x ≤ 0.8) as novel cathode material for intermediate-temperature solid oxide fuel cells. The perovskite properties including oxygen nonstoichiometry coefficient (δ), average valence of Fe, sinterability, thermal expansion coefficient, electrical conductivity (σ), oxygen chemical surface exchange coefficient (K(chem)), and chemical diffusion coefficient (D(chem)) are explored as a function of bismuth content. While σ decreases with x due to the reduced Fe(4+) content, D(chem) and K(chem) increase since the oxygen vacancy concentration is increased by Bi doping. Consequently, the electrochemical performance is substantially improved and the interfacial polarization resistance is reduced from 1.0 to 0.10 Ω cm(2) at 700 °C with Bi doping. The perovskite with x = 0.4 is suggested as the most promising composition as solid oxide fuel cell cathode material since it has demonstrated high electrical conductivity and low interfacial polarization resistance. PMID:24971668

  19. Olive mill wastewater treatment in single-chamber air-cathode microbial fuel cells.

    PubMed

    Bermek, Hakan; Catal, Tunc; Akan, S Süha; Ulutaş, Mehmet Sefa; Kumru, Mert; Özgüven, Mine; Liu, Hong; Özçelik, Beraat; Akarsubaşı, Alper Tunga

    2014-04-01

    Olive mill wastewaters create significant environmental issues in olive-processing countries. One of the most hazardous groups of pollutants in these wastewaters is phenolic compounds. Here, olive mill wastewater was used as substrate and treated in single-chamber air-cathode microbial fuel cells. Olive mill wastewater yielded a maximum voltage of 381 mV on an external resistance of 1 kΩ. Notable decreases in the contents of 3,4-dihydroxybenzoic acid, tyrosol, gallic acid and p-coumaric acid were detected. Chemical oxygen demand removal rates were 65 % while removal of total phenolics by the process was lower (49 %). Microbial community analysis during the olive mill wastewater treating MFC has shown that both exoelectrogenic and phenol-degrading microorganisms have been enriched during the operation. Brevundimonas-, Sphingomonas- and Novosphingobium-related phylotypes were enriched on the anode biofilm, while Alphaproteobacteria and Bacteriodetes dominated the cathode biofilm. As one of the novel studies, it has been demonstrated that recalcitrant olive mill wastewaters could be treated and utilized for power generation in microbial fuel cells. PMID:24165748

  20. Cubic PdNP-based air-breathing cathodes integrated in glucose hybrid biofuel cells

    NASA Astrophysics Data System (ADS)

    Faggion Junior, D.; Haddad, R.; Giroud, F.; Holzinger, M.; Maduro de Campos, C. E.; Acuña, J. J. S.; Domingos, J. B.; Cosnier, S.

    2016-05-01

    Cubic Pd nanoparticles (PdNPs) were synthesized using ascorbic acid as a reducing agent and were evaluated for the catalytic oxygen reduction reaction. PdNPs were confined with multiwalled carbon nanotube (MWCNT) dispersions to form black suspensions and these inks were dropcast onto glassy carbon electrodes. Different nanoparticle sizes were synthesized and investigated upon oxygen reduction capacities (onset potential and electrocatalytic current densities) under O2 saturated conditions at varying pH values. Strong evidence of O2 diffusion limitation was demonstrated. In order to overcome oxygen concentration and diffusion limitations in solution, we used a gas diffusion layer to create a PdNP-based air-breathing cathode, which delivered -1.5 mA cm-2 at 0.0 V with an onset potential of 0.4 V. This air-breathing cathode was combined with a specially designed phenanthrolinequinone/glucose dehydrogenase-based anode to form a complete glucose/O2 hybrid bio-fuel cell providing an open circuit voltage of 0.554 V and delivering a maximal power output of 184 +/- 21 μW cm-2 at 0.19 V and pH 7.0.Cubic Pd nanoparticles (PdNPs) were synthesized using ascorbic acid as a reducing agent and were evaluated for the catalytic oxygen reduction reaction. PdNPs were confined with multiwalled carbon nanotube (MWCNT) dispersions to form black suspensions and these inks were dropcast onto glassy carbon electrodes. Different nanoparticle sizes were synthesized and investigated upon oxygen reduction capacities (onset potential and electrocatalytic current densities) under O2 saturated conditions at varying pH values. Strong evidence of O2 diffusion limitation was demonstrated. In order to overcome oxygen concentration and diffusion limitations in solution, we used a gas diffusion layer to create a PdNP-based air-breathing cathode, which delivered -1.5 mA cm-2 at 0.0 V with an onset potential of 0.4 V. This air-breathing cathode was combined with a specially designed phenanthrolinequinone

  1. Development of Ni1-xCoxO as the cathode/interconnect contact for solid oxide fuel cells

    SciTech Connect

    Lu, Zigui; Xia, Guanguang; Templeton, Joshua D.; Li, Xiaohong S.; Nie, Zimin; Yang, Zhenguo; Stevenson, Jeffry W.

    2011-06-01

    A new type of material, Ni1-xCoxO, was developed for solid oxide fuel cell (SOFC) cathode/interconnect contact applications. The phase structure, coefficient of thermal expansion, sintering behavior, electrical property, and mechanical bonding strength of these materials were evaluated against the requirements of the SOFC cathode/interconnect contact. A dense cathode/interconnect contact layer was developed through reaction sintering from Ni and Co metal powders. An area specific resistance (ASR) as low as 5.5 mohm.cm2 was observed after 1000 h exposure in air at 800 °C for the LSM/Ni0.33Co0.67O/AISI441 assembly. Average mechanical strengths of 6.8 and 5.0 MPa were obtained for the cathode/contact/cathode and interconnect/contact/interconnect structures, respectively. The significantly low ASR was probably due to the dense structure and therefore improved electrical conductivity of the Ni0.33Co0.67O contact and the good bonding of the interfaces between the contact and the cathode, and between the contact and the interconnect.

  2. Effect of carbon black materials on the electrochemical properties of sulfur-based composite cathode for lithium-sulfur cells.

    PubMed

    Jeong, Bo Ock; Kwon, Sang Woon; Kim, Tae Jeong; Lee, Eun Hee; Jeong, Seong Hun; Jung, Yongju

    2013-12-01

    To investigate the effect of the electrode materials on the electrochemical performance of Li-S cells, sulfur cathodes were constructed using four types of carbon blacks: Ketjenblack EC-600JD (KB-600), Printex XE-2, Cabot BP-2000, and Super-P. It was found that the electrochemical performance of sulfur cathode was strongly dependent on the type of carbon black used. In the first discharge, the sulfur cathodes containing carbon blacks with a high surface area, KB-600 (SBET = 1270 m2/g), Printex XE-2 (SBET = 950 m2/g), or Cabot BP-2000 (SBET = 1487 m2/g), showed much higher discharge capacities (>1200 mA h/g) than the sulfur cathode (710 mA h/g) with Super-P (SBET = 62 m2/g). It was observed that the sulfur cathodes with KB-600, Printex XE-2, or Cabot BP-2000, which showed very similar discharge capacities one another at a low rate of 0.2 C, exhibited significantly different electrochemical behavior (the discharge capacity and midvoltage) at a high rate of 1.0 C. In particular, the sulfur cathode with KB-600 showed an extremely high capacity (831 mA h/g) with a midvoltage of 2.07 V at a 1.0 C rate, and excellent capacity retention (79%) after 50 cycles. PMID:24266155

  3. OPTIMIZATION OF THE CATHODE LONG-TERM STABILITY IN MOLTEN CARBONATE FUEL CELLS: EXPERIMENTAL STUDY AND MATHEMATICAL MODELING

    SciTech Connect

    Dr. Ralph E. White; Dr. Branko N. Popov

    2002-04-01

    The dissolution of NiO cathodes during cell operation is a limiting factor to the successful commercialization of molten carbonate fuel cells (MCFCs). Lithium cobalt oxide coating onto the porous nickel electrode has been adopted to modify the conventional MCFC cathode which is believed to increase the stability of the cathodes in the carbonate melt. The material used for surface modification should possess thermodynamic stability in the molten carbonate and also should be electro catalytically active for MCFC reactions. Two approaches have been adopted to get a stable cathode material. First approach is the use of LiNi{sub 0.8}Co{sub 0.2}O{sub 2}, a commercially available lithium battery cathode material and the second is the use of tape cast electrodes prepared from cobalt coated nickel powders. The morphology and the structure of LiNi{sub 0.8}Co{sub 0.2}O{sub 2} and tape cast Co coated nickel powder electrodes were studied using scanning electron microscopy and X-Ray diffraction studies respectively. The electrochemical performance of the two materials was investigated by electrochemical impedance spectroscopy and polarization studies. A three phase homogeneous model was developed to simulate the performance of the molten carbonate fuel cell cathode. The homogeneous model is based on volume averaging of different variables in the three phases over a small volume element. The model gives a good fit to the experimental data. The model has been used to analyze MCFC cathode performance under a wide range of operating conditions.

  4. Highly redox-resistant solid oxide fuel cell anode materials based on La-doped SrTiO3 by catalyst impregnation strategy

    NASA Astrophysics Data System (ADS)

    Shen, X.; Sasaki, K.

    2016-07-01

    An anode backbone using 40 wt% (ZrO2)0.89(Sc2O3)0.1(CeO2)0.01 (SSZ)-Sr0.9La0.1TiO3 (SLT) cermet was prepared for SSZ electrolyte-supported SOFC single cells. 15 mgcm-2 Ce0.9Gd0.1O2 (GDC) was impregnated to totally cover the SSZ-SLT anode backbone surface acting as a catalyst, and the cell voltage achieved 0.865 V at 200 mAcm-2 using (La0.75Sr0.25)0.98MnO3 (LSM)-SSZ cathode in 3%-humidified hydrogen fuel at 800 °C. Cell performance was substantially improved from 0.865 V to >0.97 V when 0.03 mgcm-2 Pd or Ni was further incorporated as a secondary catalyst into the anode layer. 50 redox cycles were performed to investigate redox stability of this high performance anode. It was found that even after the 50 redox cycle long-term degradation test, cell voltage at 200 mAcm-2 was retained around 0.94 V, higher than the cell performance using the conventional Ni-SSZ cermet anode. The catalytically-active reaction sites at ceria-Pd or ceria-Ni may account for the excellent performance, and the extremely low metal catalyst concentration prevent serious metal aggregation in achieving excellent redox stability.

  5. Artificial Neural Network Modeling of Pt/C Cathode Degradation in PEM Fuel Cells

    NASA Astrophysics Data System (ADS)

    Maleki, Erfan; Maleki, Nasim

    2016-08-01

    Use of computational modeling with a few experiments is considered useful to obtain the best possible result for a final product, without performing expensive and time-consuming experiments. Proton exchange membrane fuel cells (PEMFCs) can produce clean electricity, but still require further study. An oxygen reduction reaction (ORR) takes place at the cathode, and carbon-supported platinum (Pt/C) is commonly used as an electrocatalyst. The harsh conditions during PEMFC operation result in Pt/C degradation. Observation of changes in the Pt/C layer under operating conditions provides a tool to study the lifetime of PEMFCs and overcome durability issues. Recently, artificial neural networks (ANNs) have been used to solve, predict, and optimize a wide range of scientific problems. In this study, several rates of change at the cathode were modeled using ANNs. The backpropagation (BP) algorithm was used to train the network, and experimental data were employed for network training and testing. Two different models are constructed in the present study. First, the potential cycles, temperature, and humidity are used as inputs to predict the resulting Pt dissolution rate of the Pt/C at the cathode as the output parameter of the network. Thereafter, the Pt dissolution rate and Pt ion diffusivity are regarded as inputs to obtain values of the Pt particle radius change rate, Pt mass loss rate, and surface area loss rate as outputs. The networks are finely tuned, and the modeling results agree well with experimental data. The modeled responses of the ANNs are acceptable for this application.

  6. Interface investigation of the alcohol-/water-soluble conjugated polymer PFN as cathode interfacial layer in organic solar cells

    NASA Astrophysics Data System (ADS)

    Zhong, Shu; Wang, Rui; Ying Mao, Hong; He, Zhicai; Wu, Hongbin; Chen, Wei; Cao, Yong

    2013-09-01

    In this work, in situ ultraviolet photoelectron spectroscopy measurements were used to investigate the working mechanism of an alcohol-/water-soluble conjugated polymer poly [(9,9-bis(3'-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)] (PFN) as the cathode interfacial layer in organic solar cells from the view of interfacial energy level alignment. Fullerene (C60) was chosen as the model acceptor material in contact with PFN as well as two other cathode interfacial layers ZnO and TiO2 in the configuration of an inverted solar cell structure. Significant charge transfer between PFN modified ITO (indium tin oxide) electrode and C60 is observed due to the low work function of PFN. This results in the Fermi level of the substrate pinned very close to the lowest unoccupied molecular orbital of C60 as well as an additional electric field at the cathode/acceptor interface. Both of them facilitate the electron extraction from the acceptor C60 to the ITO cathode, as confirmed by the electrical measurements of the electron-only devices with PFN modification. The better electron extraction originated from the Fermi level pinning and the additional interface electric field are believed to contribute to the efficiency enhancement of the inverted organic solar cells employing PFN as cathode interfacial layer.

  7. Effect of flow pulsation on mass transport in a cathode channel of polymer electrolyte membrane fuel cell

    NASA Astrophysics Data System (ADS)

    Han, Hun Sik; Kim, Yun Ho; Kim, Seo Young; Hyun, Jae Min

    2012-09-01

    An experimental and theoretical study on the cathode flow pulsation in a polymer electrolyte membrane (PEM) fuel cell is performed. A 10-cell PEM fuel cell stack with open-air cathode channels is employed to investigate the effects of the cathode flow pulsation on the overall performance. The polarization and corresponding power curves obtained show that both the limiting current density and the maximum power density are substantially enhanced when the pulsating component is added to the cathode mainstream flow. The flow pulsation at Re = 77 provides the maximum increment of 40% and 35.5% in the limiting current density and in the maximum power density, respectively. The enhancement of the overall performance is more pronounced at low Reynolds numbers. Also, the theoretical mass transport analysis in the pulsating cathode flow channel is carried out to verify the present experimental results. The momentum and species conservation equations are analytically solved, and the effective time-averaged dispersion coefficient is defined to account for the enhanced mass transport by the flow pulsation. Comprehensive analytical solutions show that the effect of the relevant parameters is in well accordance with the experimental results.

  8. Determination of Optimal Parameters for Dual-Layer Cathode of Polymer Electrolyte Fuel Cell Using Computational Intelligence-Aided Design

    PubMed Central

    Chen, Yi; Huang, Weina; Peng, Bei

    2014-01-01

    Because of the demands for sustainable and renewable energy, fuel cells have become increasingly popular, particularly the polymer electrolyte fuel cell (PEFC). Among the various components, the cathode plays a key role in the operation of a PEFC. In this study, a quantitative dual-layer cathode model was proposed for determining the optimal parameters that minimize the over-potential difference and improve the efficiency using a newly developed bat swarm algorithm with a variable population embedded in the computational intelligence-aided design. The simulation results were in agreement with previously reported results, suggesting that the proposed technique has potential applications for automating and optimizing the design of PEFCs. PMID:25490761

  9. Device lifetime improvement of polymer-based bulk heterojunction solar cells by incorporating copper oxide layer at Al cathode

    NASA Astrophysics Data System (ADS)

    Wang, Mingdong; Xie, Fangyan; Xie, Weiguang; Zheng, Shizhao; Ke, Ning; Chen, Jian; Zhao, Ni; Xu, J. B.

    2011-05-01

    Organic solar cells are commonly susceptible to degradation in air. We present that insertion of a thin layer of thermally evaporated copper oxide (CuOx) between the organic active layer and the Al cathode can greatly extend the lifetime of P3HT:PCBM based bulk heterojunction solar cells. The performance can be further improved by applying an interfacial bilayer of CuOx/LiF. Our results suggest that the CuOx functions not only as a charge transport layer but also as a protection layer, which prevents formation of thick organic-Al interdiffusion area. This leads to a more air-resistive cathode/organic interface.

  10. Impact of micro-porous layer on liquid water distribution at the catalyst layer interface and cell performance in a polymer electrolyte membrane fuel cell

    NASA Astrophysics Data System (ADS)

    Tabe, Yutaka; Aoyama, Yusuke; Kadowaki, Kazumasa; Suzuki, Kengo; Chikahisa, Takemi

    2015-08-01

    In polymer electrolyte membrane fuel cells, a gas diffusion layer (GDL) with a micro-porous layer (MPL) gives better anti-flooding performance than GDLs without an MPL. To investigate the function and mechanism of the MPL to suppress water flooding, the liquid water distribution at the cathode catalyst layer (CL) surface are observed by a freezing method; in the method liquid water is immobilized in ice form by rapid freezing, followed by disassembling the cell for observations. The ice covered area is quantified by image processing and cells with and without an MPL are compared. The results show that the MPL suppresses water accumulation at the interface due to smaller pore size and finer contact with the CL, and this results in less water flooding. Investigation of ice formed after -10 °C cold start shutdowns and the temporary performance deterioration at ordinary temperatures also indicates a significant influence of the liquid water accumulating at the interface. The importance of the fine contact between CL and MPL, the relative absence of gaps, is demonstrated by a gas diffusion electrode (GDE) which is directly coated with catalyst ink on the surface of the MPL achieving finer contact of the layers.

  11. Copper-substituted perovskite compositions for solid oxide fuel cell cathodes and oxygen reduction electrodes in other electrochemical devices

    DOEpatents

    Rieke, Peter C.; Coffey, Gregory W.; Pederson, Larry R.; Marina, Olga A.; Hardy, John S.; Singh, Prabhaker; Thomsen, Edwin C.

    2010-07-20

    The present invention provides novel compositions that find advantageous use in making electrodes for electrochemical cells. Also provided are electrochemical devices that include active oxygen reduction electrodes, such as solid oxide fuel cells, sensors, pumps and the like. The compositions comprises a copper-substituted ferrite perovskite material. The invention also provides novel methods for making and using the electrode compositions and solid oxide fuel cells and solid oxide fuel cell assemblies having cathodes comprising the compositions.

  12. Platinum-rare earth cathodes for direct borohydride-peroxide fuel cells

    NASA Astrophysics Data System (ADS)

    Cardoso, D. S. P.; Santos, D. M. F.; Šljukić, B.; Sequeira, C. A. C.; Macciò, D.; Saccone, A.

    2016-03-01

    Hydrogen peroxide (H2O2) is being actively investigated as an oxidant for direct borohydride fuel cells. Herein, platinum-rare earth (RE = Sm, Dy, Ho) alloys are prepared by arc melting and their activity for hydrogen peroxide reduction reaction (HPRR) is studied in alkaline media. Cyclic voltammetry and chronoamperometry measurements show that Pt-Sm electrode displays the highest catalytic activity for HPRR with the lowest activation energy, followed by Pt-Ho, while Pt-Dy alloys show practically no activity. Laboratory direct borohydride-peroxide fuel cells (DBPFCs) are assembled using these alloys. The DBPFC with Pt-Sm cathode gives the highest peak power density of 85 mW cm-2, which is more than double of that obtained in a DBPFC with Pt electrodes.

  13. OPTIMIZATION OF THE CATHODE LONG TERM STABILITY IN MOLTEN CARBONATE FUEL CELLS: EXPERIMENTAL STUDY AND MATHEMATICAL MODELING

    SciTech Connect

    Anand Durairajan; Bala Haran; Branko N. Popov; Ralph E. White

    2000-05-01

    The cathode materials for molten carbonate fuel cells (MCFCs) must have low dissolution rate, high structural strength and good electrical conductivity. Currently available cathodes are made of lithiated NiO which have acceptable structural strength and conductivity. However a study carried out by Orfeld et al. and Shores et al. indicated that the nickel cathodes dissolved, then precipitated and reformed as dendrites across the electrolyte matrix. This results in a decrease in cell utilization and eventually leads to shorting of the cell. The solubility of NiO was found to depend upon the acidity/basicity of the melt (basicity is directly proportional to log P{sub CO2}), carbonate composition, H{sub 2}O partial pressure and temperature. Urushibata et al. found that the dissolution of the cathode is a primary life limiting constraint of MCFCs, particularly in pressurized operation. With currently available NiO cathodes, the goal of 40,000 hours for the lifetime of MCFC appears achievable with cell operation at atmospheric pressure. However, the cell life at 10 atm and higher cell pressures is in the range between 5,000 to 10,000 hours. The overall objective of this research is to develop a superior cathode for MCFC's with improved catalytic ability, enhanced corrosion resistance with low ohmic losses, improved electronic conductivity. We also plan to understand the corrosion processes occurring at the cathode/molten carbonate interface. The following cathode materials will be subjected to detailed electrochemical, performance, structural and corrosion studies. (i) Passivated NiO alloys using chemical treatment with yttrium ion implantation and anodic yttrium molybdate treatment; (ii) Novel composite materials based on NiO and nanosized Ce, Yt, Mo; (iii) Co doped LiNiO{sub 2} LiNiO{sub 2} doped with 10 to 20% Co (LiCo{sub 0.2}NiO{sub 2}) and NiO cathodes; and (iv) CoO as a replacement for NiO. Passivation treatments will inhibit corrosion and increase the stability

  14. High rate Li/SOCl(2) cells. 2. Effect of catalyst on cell performance

    NASA Astrophysics Data System (ADS)

    Kilroy, W. P.; Pitts, L.; Abraham, K. M.

    1985-04-01

    As part of the ongoing High Energy Batteries for Weapons Programs at NSWC, various cell parameters were investigated to examine their effect on the performance, safety, and chemistry of Li/SOCl2 cells. This report summarizes the influence of cobalt dibenzo-tetraazaannulene (Co-TAA) cataylsis on the discharge and overdischarge chemistry and performance of spirally wound commercial C-size cells. Co-TAA catalyst improved the performance and safety of C-size Li/SOCl2 cells. The catalyst was most effective at high rate or low temperature operation. The presence of water increased the risk of hazards at high rates of discharge. The generation of gases such as COS, CS2, HCl, etc. was dependent on the internal temperature.

  15. Nanoporous silver cathode surface treated by atomic layer deposition of CeO(x) for low-temperature solid oxide fuel cells.

    PubMed

    Neoh, Ke Chean; Han, Gwon Deok; Kim, Manjin; Kim, Jun Woo; Choi, Hyung Jong; Park, Suk Won; Shim, Joon Hyung

    2016-05-01

    We evaluated the performance of solid oxide fuel cells (SOFCs) with a 50 nm thin silver (Ag) cathode surface treated with cerium oxide (CeO(x)) by atomic layer deposition (ALD). The performances of bare and ALD-treated Ag cathodes were evaluated on gadolinia-doped ceria (GDC) electrolyte supporting cells with a platinum (Pt) anode over 300 °C-450 °C. Our work confirms that ALD CeO(x) treatment enhances cathodic performance and thermal stability of the Ag cathode. The performance difference between cells using a Ag cathode optimally treated with an ALD CeO(x) surface and a reference Pt cathode is about 50% at 450 °C in terms of fuel cell power output in our experiment. The bare Ag cathode completely agglomerated into islands during fuel cell operation at 450 °C, while the ALD CeO(x) treatment effectively protects the porosity of the cathode. We also discuss the long-term stability of ALD CeO(x)-treated Ag cathodes related to the microstructure of the layers. PMID:27008979

  16. Nanoporous silver cathode surface treated by atomic layer deposition of CeO x for low-temperature solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Chean Neoh, Ke; Han, Gwon Deok; Kim, Manjin; Kim, Jun Woo; Jong Choi, Hyung; Park, Suk Won; Shim, Joon Hyung

    2016-05-01

    We evaluated the performance of solid oxide fuel cells (SOFCs) with a 50 nm thin silver (Ag) cathode surface treated with cerium oxide (CeO x ) by atomic layer deposition (ALD). The performances of bare and ALD-treated Ag cathodes were evaluated on gadolinia-doped ceria (GDC) electrolyte supporting cells with a platinum (Pt) anode over 300 °C-450 °C. Our work confirms that ALD CeO x treatment enhances cathodic performance and thermal stability of the Ag cathode. The performance difference between cells using a Ag cathode optimally treated with an ALD CeO x surface and a reference Pt cathode is about 50% at 450 °C in terms of fuel cell power output in our experiment. The bare Ag cathode completely agglomerated into islands during fuel cell operation at 450 °C, while the ALD CeO x treatment effectively protects the porosity of the cathode. We also discuss the long-term stability of ALD CeO x -treated Ag cathodes related to the microstructure of the layers.

  17. Reactivity Descriptors for Direct Methanol Fuel Cell Anode Catalysts

    SciTech Connect

    Ferrin, Peter; Nilekar, Anand U.; Greeley, Jeffrey P.; Mavrikakis, Manos; Rossmeisl, Jan

    2008-11-01

    We have investigated the anode reaction in direct methanol fuel cells using a database of adsorption free energies for 16 intermediates on 12 close-packed transition metal surfaces calculated with periodic, selfconsistent, density functional theory (DFT–GGA). This database, combined with a simple electrokinetic model of the methanol electrooxidation reaction, yields mechanistic insights that are consistent with previous experimental and theoretical studies on Pt, and extends these insights to a broad spectrum of other transition metals. In addition, by using linear scaling relations between the adsorption free energies of various intermediates in the reaction network, we find that the results determined with the full database of adsorption energies can be estimated by knowing only two key descriptors for each metal surface: the free energies of OH and CO on the surface. Two mechanisms for methanol oxidation to CO₂ are investigated: an indirect mechanism that goes through a CO intermediate and a direct mechanism where methanol is oxidized to CO₂ without the formation of a CO intermediate. For the direct mechanism, we find that, because of CO poisoning, only a small current will result on all non-group 11 transition metals; of these metals, Pt is predicted to be the most active. For methanol decomposition via the indirect mechanism, we find that the onset potential is limited either by the ability to activate methanol, by the ability to activate water, or by surface poisoning by CO* or OH*/O*. Among pure metals, there is no obvious candidate for a good anode catalyst, and in order to design a better catalyst, one has to look for bi-functional surfaces such as the well-studied PtRu alloy.

  18. Development and characterization of novel cathode materials for molten carbonate fuel cell

    NASA Astrophysics Data System (ADS)

    Giorgi, L.; Carewska, M.; Patriarca, M.; Scaccia, S.; Simonetti, E.; Dibartolomeo, A.

    1994-04-01

    In the development of molten carbonate fuel cell (MCFC) technology, the corrosion of materials is a serious problem for long-term operation. Indeed, slow dissolution of lithiated-NiO cathode in molten carbonates is the main obstacle for the commercialization of MCFCs. In the search of new, more stable, cathode materials, alternative compounds such as LiFeO2, Li2MnO3, and La(1-x)Sr(x)CoO3 are presently under investigation to replace the currently used lithiated-NiO. The aim of the present work was to investigate the possibility to produce electrode based on LiCoO2, a promising cathode material. At first, Li(x)CoO2 powder samples (0.8 less than x less than 1.1) were made by thermal decomposition of carbonate precursors in air. The synthesis processes were monitored by thermal analysis (TGA, DTA). The calcined and sintered powder samples were characterized by x ray diffraction (XRD) andatomic absorption spectrophotometry (F-AAS). A single phase was detected in all the samples, without any change in crystal structure as a function of lithium content. Porous sintered electrodes were prepared starting from lithium cobaltite powders mixed with different pore-formers by cold pressing and sintering. A bimodal pore-size distribution with a mean pore diameter in the range of 0.15 to 8 micron, a surface area of 2 to 12 sq m/g and a porosity of 10 to 65%, determined by the Hg-intrusion technique, were observed in all the materials. Conductivity measurements were carried out in the temperature range of 500-700 C, in air. The influence of the deviations from stoichiometry on the electronic properties was determined, the conductivity value of the stoichiometric compound being the lowest. A linear relationship between the electronic conductivity and the sample porosity was found. Solubility testing of the materials was carried out to evaluate their chemical stability in the electrolyte. The sampling method (F-AAS) and square wave voltammetry (SWV) were used to determine the

  19. Finite element thermal stress analysis of solid oxide fuel cell cathode microstructures

    NASA Astrophysics Data System (ADS)

    Vaidya, Sushrut; Kim, Jeong-Ho

    2013-03-01

    Two-dimensional images of solid oxide fuel cell (SOFC) cathode microstructures (50:50 wt.% LSM:YSZ) are used to generate three-dimensional finite element (FE) models. An approximate, heuristic scheme is developed to derive a microstructure of 30:70 wt.% LSM:YSZ composition from the original, real microstructures. The derived model is validated by calculating three-phase boundary (TPB) and phase surface area densities by comparing with data available in the literature. Construction of such derived microstructures will provide insights on the effects of phase compositions on the mechanics of electrode structures. The heuristic scheme is not proposed as a replacement for rigorous approaches such as the random packing model, but rather as a simplified approach for deriving reasonably realistic microstructures of different compositions within a limited range of validity. The models are analyzed using finite elements to estimate thermal stresses and probability of failure using Weibull analysis. The effects of temperature-dependent material properties and phase volume fractions on probability of failure of the cathode are discussed.

  20. Development of carbon free diffusion layer for activated carbon air cathode of microbial fuel cells.

    PubMed

    Yang, Wulin; Kim, Kyoung-Yeol; Logan, Bruce E

    2015-12-01

    The fabrication of activated carbon air cathodes for larger-scale microbial fuel cells requires a diffusion layer (DL) that is highly resistant to water leakage, oxygen permeable, and made using inexpensive materials. A hydrophobic polyvinylidene fluoride (PVDF) membrane synthesized using a simple phase inversion process was examined as a low cost ($0.9/m(2)), carbon-free DL that prevented water leakage at high pressure heads compared to a polytetrafluoroethylene/carbon black DL ($11/m(2)). The power density produced with a PVDF (20%, w/v) DL membrane of 1400±7mW/m(2) was similar to that obtained using a wipe DL [cloth coated with poly(dimethylsiloxane)]. Water head tolerance reached 1.9m (∼19kPa) with no mesh supporter, and 2.1m (∼21kPa, maximum testing pressure) with a mesh supporter, compared to 0.2±0.05m for the wipe DL. The elimination of carbon black from the DL greatly simplified the fabrication procedure and further reduced overall cathode costs. PMID:26342345

  1. Carbon filtration cathode in microbial fuel cell to enhance wastewater treatment.

    PubMed

    Zuo, Kuichang; Liang, Shuai; Liang, Peng; Zhou, Xuechen; Sun, Dongya; Zhang, Xiaoyuan; Huang, Xia

    2015-06-01

    A homogeneous carbon membrane with multi-functions of microfiltration, electron conduction, and oxygen reduction catalysis was fabricated without using noble metals. The produced carbon membrane has a pore size of 553nm, a resistance of 6.0±0.4Ωcm(2)/cm, and a specific surface area of 32.2m(2)/g. After it was assembled in microbial fuel cell (MFC) as filtration air cathode, a power density of 581.5mW/m(2) and a current density of 1671.4mA/m(2) were achieved, comparable with previous Pt air cathode MFCs. The filtration MFC was continuously operated for 20days and excellent wastewater treatment performance was also achieved with removal efficiencies of TOC (93.6%), NH4(+)-N (97.2%), and total nitrogen (91.6%). In addition, the carbon membrane was much cheaper than traditional microfiltration membrane, suggesting a promising multi-functional material in wastewater treatment field. PMID:25782632

  2. Rational design of novel cathode materials in solid oxide fuel cells using first-principles simulations

    NASA Astrophysics Data System (ADS)

    Choi, YongMan; Lin, M. C.; Liu, Meilin

    The search for clean and renewable sources of energy represents one of the most vital challenges facing us today. Solid oxide fuel cells (SOFCs) are among the most promising technologies for a clean and secure energy future due to their high energy efficiency and excellent fuel flexibility (e.g., direct utilization of hydrocarbons or renewable fuels). To make SOFCs economically competitive, however, development of new materials for low-temperature operation is essential. Here we report our results on a computational study to achieve rational design of SOFC cathodes with fast oxygen reduction kinetics and rapid ionic transport. Results suggest that surface catalytic properties are strongly correlated with the bulk transport properties in several material systems with the formula of La 0.5Sr 0.5BO 2.75 (where B = Cr, Mn, Fe, or Co). The predictions seem to agree qualitatively with available experimental results on these materials. This computational screening technique may guide us to search for high-efficiency cathode materials for a new generation of SOFCs.

  3. Combined Theoretical and Experimental Analysis of Processes Determining Cathode Performance in Solid Oxide Fuel Cells

    SciTech Connect

    Kukla, Maija M.; Kotomin, Eugene Alexej; Merkle, R.; Mastrikov, Yuri; Maier, J.

    2013-02-11

    Solid oxide fuel cells (SOFC) are under intensive investigation since the 1980’s as these devices open the way for ecologically clean direct conversion of the chemical energy into electricity, avoiding the efficiency limitation by Carnot’s cycle for thermochemical conversion. However, the practical development of SOFC faces a number of unresolved fundamental problems, in particular concerning the kinetics of the electrode reactions, especially oxygen reduction reaction. We review recent experimental and theoretical achievements in the current understanding of the cathode performance by exploring and comparing mostly three materials: (La,Sr)MnO3 (LSM), (La,Sr)(Co,Fe)O3 (LSCF) and (Ba,Sr)(Co,Fe)O3 (BSCF). Special attention is paid to a critical evaluation of advantages and disadvantages of BSCF, which shows the best cathode kinetics known so far for oxides. We demonstrate that it is the combined experimental and theoretical analysis of all major elementary steps of the oxygen reduction reaction which allows us to predict the rate determining steps for a given material under specific operational conditions and thus control and improve SOFC performance.

  4. Stabilizing nanostructured solid oxide fuel cell cathode with atomic layer deposition.

    PubMed

    Gong, Yunhui; Palacio, Diego; Song, Xueyan; Patel, Rajankumar L; Liang, Xinhua; Zhao, Xuan; Goodenough, John B; Huang, Kevin

    2013-09-11

    We demonstrate that the highly active but unstable nanostructured intermediate-temperature solid oxide fuel cell cathode, La0.6Sr0.4CoO3-δ (LSCo), can retain its high oxygen reduction reaction (ORR) activity with exceptional stability for 4000 h at 700 °C by overcoating its surfaces with a conformal layer of nanoscale ZrO2 films through atomic layer deposition (ALD). The benefits from the presence of the nanoscale ALD-ZrO2 overcoats are remarkable: a factor of 19 and 18 reduction in polarization area-specific resistance and degradation rate over the pristine sample, respectively. The unique multifunctionality of the ALD-derived nanoscaled ZrO2 overcoats, that is, possessing porosity for O2 access to LSCo, conducting both electrons and oxide-ions, confining thermal growth of LSCo nanoparticles, and suppressing surface Sr-segregation is deemed the key enabler for the observed stable and active nanostructured cathode. PMID:23924170

  5. Cubic PdNP-based air-breathing cathodes integrated in glucose hybrid biofuel cells.

    PubMed

    Faggion Junior, D; Haddad, R; Giroud, F; Holzinger, M; Maduro de Campos, C E; Acuña, J J S; Domingos, J B; Cosnier, S

    2016-05-21

    Cubic Pd nanoparticles (PdNPs) were synthesized using ascorbic acid as a reducing agent and were evaluated for the catalytic oxygen reduction reaction. PdNPs were confined with multiwalled carbon nanotube (MWCNT) dispersions to form black suspensions and these inks were dropcast onto glassy carbon electrodes. Different nanoparticle sizes were synthesized and investigated upon oxygen reduction capacities (onset potential and electrocatalytic current densities) under O2 saturated conditions at varying pH values. Strong evidence of O2 diffusion limitation was demonstrated. In order to overcome oxygen concentration and diffusion limitations in solution, we used a gas diffusion layer to create a PdNP-based air-breathing cathode, which delivered -1.5 mA cm(-2) at 0.0 V with an onset potential of 0.4 V. This air-breathing cathode was combined with a specially designed phenanthrolinequinone/glucose dehydrogenase-based anode to form a complete glucose/O2 hybrid bio-fuel cell providing an open circuit voltage of 0.554 V and delivering a maximal power output of 184 ± 21 μW cm(-2) at 0.19 V and pH 7.0. PMID:27142300

  6. Analysis of long-term performance and microbial community structure in bio-cathode microbial desalination cells.

    PubMed

    Zhang, Huichao; Wen, Qinxue; An, Zhongyi; Chen, Zhiqiang; Nan, Jun

    2016-03-01

    A microbial desalination cell (MDC) could desalinate salt water without energy consumption and simultaneously generate bioenergy. Compared with an abiotic cathode MDC, an aerobic bio-cathode MDC is more sustainable and is less expensive to operate. In this study, the long-term operation (5500 h) performance of a bio-cathode MDC was investigated in which the power density, Coulombic efficiency, and salt removal rate were decreased by 71, 44, and 27 %, respectively. The primary reason for the system performance decrease was biofouling on the membranes, which increased internal resistance and reduced the ionic transfer and energy conversion efficiency. Changing membranes was an effective method to recover the MDC performance. The microbial community diversity in the MDC anode was low compared with that of the reported microbial fuel cell (MFC), while the abundance of Proteobacteria was 30 % higher. The content of Planctomycetes in the cathode biofilm sample was much higher than that in biofouling on the cation exchange membrane (CEM), indicating that Planctomycetes were relevant to cathode oxygen reduction. PMID:26596826

  7. Simultaneous selection of soil electroactive bacterial communities associated to anode and cathode in a two-chamber Microbial Fuel Cell

    NASA Astrophysics Data System (ADS)

    Chiellini, Carolina; Bacci, Giovanni; Fani, Renato; Mocali, Stefano

    2016-04-01

    Different bacteria have evolved strategies to transfer electrons over their cell surface to (or from) their extracellular environment. This electron transfer enables the use of these bacteria in bioelectrochemical systems (BES) such as Microbial Fuel Cells (MFCs). In MFC research the biological reactions at the cathode have long been a secondary point of interest. However, bacterial biocathodes in MFCs represent a potential advantage compared to traditional cathodes, for both their low costs and their low impact on the environment. The main challenge in biocathode set-up is represented by the selection of a bacterial community able to efficiently accept electrons from the electrode, starting from an environmental matrix. In this work, a constant voltage was supplied on a two-chamber MFC filled up with soil over three weeks in order to simultaneously select an electron donor bacterial biomass on the anode and an electron acceptor biomass on the cathode, starting from the same soil. Next Generation Sequencing (NGS) analysis was performed to characterize the bacterial community of the initial soil, in the anode, in the cathode and in the control chamber not supplied with any voltage. Results highlighted that both the MFC conditions and the voltage supply affected the soil bacterial communities, providing a selection of different bacterial groups preferentially associated to the anode (Betaproteobacteria, Bacilli and Clostridia) and to the cathode (Actinobacteria and Alphaproteobacteria). These results confirmed that several electroactive bacteria are naturally present within a top soil and, moreover, different soil bacterial genera could provide different electrical properties.

  8. Enhanced performance of an air-cathode microbial fuel cell with oxygen supply from an externally connected algal bioreactor.

    PubMed

    Kakarla, Ramesh; Kim, Jung Rae; Jeon, Byong-Hun; Min, Booki

    2015-11-01

    An algae bioreactor (ABR) was externally connected to air-cathode microbial fuel cells (MFCs) to increase power generation by supplying a high amount of oxygen to cathode electrode. The MFC with oxygen fed from ABR produced maximum cell voltage and cathode potential at a fixed loading of 459 mV and 10 mV, respectively. During polarization analysis, the MFC displayed a maximum power density of 0.63 W/m(2) (at 2.06 A/m(2)) using 39.2% O2 from ABR, which was approximately 30% higher compared with use of atmospheric air (0.44 W/m(2), 20.8% O2,). The cyclic voltammogram analysis exhibited a higher reduction current of -137 mA with 46.5% O2 compared to atmospheric air (-115 mA). Oxygen supply by algae bioreactor to air-cathode MFC could also maintain better MFC performance in long term operation by minimizing cathode potential drop over time. PMID:26188984

  9. OPTIMIZATION OF THE CATHODE LONG-TERM STABILITY IN MOLTEN CARBONATE FUEL CELLS: EXPERIMENTAL STUDY AND MATHEMATICAL MODELING

    SciTech Connect

    Hector Colonmer; Prabhu Ganesan; Nalini Subramanian; Dr. Bala Haran; Dr. Ralph E. White; Dr. Branko N. Popov

    2002-09-01

    This project focused on addressing the two main problems associated with state of art Molten Carbonate Fuel Cells, namely loss of cathode active material and stainless steel current collector deterioration due to corrosion. We followed a dual approach where in the first case we developed novel materials to replace the cathode and current collector currently used in molten carbonate fuel cells. In the second case we improved the performance of conventional cathode and current collectors through surface modification. States of art NiO cathode in MCFC undergo dissolution in the cathode melt thereby limiting the lifetime of the cell. To prevent this we deposited cobalt using an electroless deposition process. We also coated perovskite (La{sub 0.8}Sr{sub 0.2}CoO{sub 3}) in NiO thorough a sol-gel process. The electrochemical oxidation behavior of Co and perovskites coated electrodes is similar to that of the bare NiO cathode. Co and perovskite coatings on the surface decrease the dissolution of Ni into the melt and thereby stabilize the cathode. Both, cobalt and provskites coated nickel oxide, show a higher polarization compared to that of nickel oxide, which could be due to the reduced surface area. Cobalt substituted lithium nickel oxide (LiNi{sub 0.8}Co{sub 0.2}O{sub 2}) and lithium cobalt oxide were also studied. LiNi{sub x}Co{sub 1-x}O{sub 2} was synthesized by solid-state reaction procedure using lithium nitrate, nickel hydroxide and cobalt oxalate precursor. LiNi{sub x}Co{sub 1-x}O{sub 2} showed smaller dissolution of nickel than state of art nickel oxide cathode. The performance was comparable to that of nickel oxide. The corrosion of the current collector in the cathode side was also studied. The corrosion characteristics of both SS304 and SS304 coated with Co-Ni alloy were studied. This study confirms that surface modification of SS304 leads to the formation of complex scales with better barrier properties and better electronic conductivity at 650 C. A three

  10. OPTIMIZATION OF THE CATHODE LONG-TERM STABILITY IN MOLTEN CARBONATE FUEL CELLS: EXPERIMENTAL STUDY AND MATHEMATICAL MODELING

    SciTech Connect

    Dr. Ralph E. White; Dr. Branko N. Popov

    2001-10-01

    The dissolution of NiO cathodes during cell operation is a limiting factor to the successful commercialization of molten carbonate fuel cells (MCFCs). Lithium cobalt oxide coating onto the porous nickel electrode has been adopted to modify the conventional MCFC cathode which is believed to increase the stability of the cathodes in the carbonate melt. The material used for surface modification should possess thermodynamic stability in the molten carbonate and also should be electro catalytically active for MCFC reactions. Lithium Cobalt oxide was coated on Ni cathode by a sol-gel coating. The morphology and the LiCoO{sub 2} formation of LiCoO{sub 2} coated NiO was studied using scanning electron microscopy and X-Ray diffraction studies respectively. The electrochemical performance lithium cobalt oxide coated NiO cathodes were investigated with open circuit potential measurement and current-potential polarization studies. These results were compared to that of bare NiO. Dissolution of nickel into the molten carbonate melt was less in case of lithium cobalt oxide coated nickel cathodes. LiCoO{sub 2} coated on the surface prevents the dissolution of Ni in the melt and thereby stabilizes the cathode. Finally, lithium cobalt oxide coated nickel shows similar polarization characteristics as nickel oxide. Conventional theoretical models for the molten carbonate fuel cell cathode are based on the thin film agglomerate model. The principal deficiency of the agglomerate model, apart from the simplified pore structure assumed, is the lack of measured values for film thickness and agglomerate radius. Both these parameters cannot be estimated appropriately. Attempts to estimate the thickness of the film vary by two orders of magnitude. To avoid these problems a new three phase homogeneous model has been developed using the volume averaging technique. The model considers the potential and current variation in both liquid and solid phases. Using this approach, volume averaged

  11. The effect of cathode felt geometries on electrochemical characteristics of sodium sulfur (NaS) cells: Planar vs. tubular

    NASA Astrophysics Data System (ADS)

    Kim, Goun; Park, Yoon-Cheol; Lee, Younki; Cho, Namung; Kim, Chang-Soo; Jung, Keeyoung

    2016-09-01

    Two sodium sulfur (NaS) cells, one with a planar design and the other with a tubular design, were subject to discharge-charge cycles in order to investigate the effect of cathode felt geometries on electrochemical characteristics of NaS cells. Their discharge-charge behaviors over 200 cycles were evaluated at the operation temperature of 350 °C with the current densities of 100 mA cm-2 for discharge and 80 mA cm-2 for charge. The results showed that the deviation from theoretical open circuit voltage changes of a planar cell was smaller than those of a tubular cell resulting in potential specific power loss reduction during operation. In order to understand the effect, a three dimensional statistically representative matrix for a cathode felt has been generated using experimentally measured data. It turns out that the area specific fiber number density in the outer side area of a tubular cathode felt is smaller than that of a planar felt resulting in occurrence of larger voltage drops via retarded convection of cathode melts during cell operation.

  12. Influence of different morphology of three-dimensional Cu(x)O with mixed facets modified air-cathodes on microbial fuel cell.

    PubMed

    Liu, Ziqi; Li, Kexun; Zhang, Xi; Ge, Baochao; Pu, Liangtao

    2015-11-01

    Three kinds of three-dimensional (3D) CuxO catalysts were prepared to modify activated carbon air-cathode using a facile electrochemical method with addition of surfactants. The maximum power density of MFC using SC-Cu air cathode (added sodium citrate into the electrolyte solution in electrodeposition process) was 1550±47 mW m(-2), almost 77% higher than AC cathode. Specifically, the charge transfer resistance significantly decreased by 89% from 9.3980 Ω to 1.0640 Ω compared to the control. Lumphy and mutually embedded filmy sheet structure were observed in SEM, which provided sufficient active sites for oxygen adsorption and diffusion. In XRD and TEM result, CuxO with mixed facets showed special structure which had a better performance. Crystallization condition of electrodeposited materials played a significant role in their nature electrochemical properties, morphology controlled by surfactant of CuxO exhibited high properties on the air-cathode MFC. PMID:26122090

  13. Long-term testing and evaluation of cathode components in a commercial aluminum cell

    SciTech Connect

    Church, K.D.; Morris, E.G.; Joo, L.A. ); Stewart, D.V.; Morgan, W.R.; Tabereaux, A. )

    1990-04-01

    Since 1886, essentially all primary aluminum has been produced in Hall-Heroult electrolytic cells which electrochemically reduce alumina to the metal in an energy/capital intensive process. Nearly five per cent of the electrical energy generated in the United States in consumed in this Hall-Heroult process, at the rate of 6--8 kwh/lb. of aluminum produced. It has been in the aluminum industry's interest for the past several decades to utilize titanium diboride in some capacity as the cell cathode, either with conventional consumable carbon anodes or ultimately with nonconsumable, inert anodes. Eventual achievement of either or both of these goals will represent a technological breakthrough and make possible a significant reduction in the energy requirement to produce aluminum. The overall objective and achievement of this program was to better define the technical and economic viability of graphite-containing titanium diboride materials in low-cost shapes for use as cathodes in aluminum electrolytic cells as a precursor to subsequent demonstration and commercial application. This report covers the development of possible failure mechanisms, evaluations of the thermal shock resistance of non-cylindrical shapes, and an assessment of energy savings and technical/economic viability. In this program, titanium diboride-graphite (TiB{sub 2}-G) materials was demonstrated to be superior to dense TiB{sub 2} materials which had been previously evaluated in studies by others in terms of longevity, thermal shock properties, and the ability to manufacture large, complex components. 129 figs., 5 tabs.

  14. Nanoporous silver cathodes surface-treated by atomic layer deposition of Y:ZrO2 for high-performance low-temperature solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Li, You Kai; Choi, Hyung Jong; Kim, Ho Keun; Chean, Neoh Ke; Kim, Manjin; Koo, Junmo; Jeong, Heon Jae; Jang, Dong Young; Shim, Joon Hyung

    2015-11-01

    We report high-performance solid-oxide fuel cells (SOFCs) with silver cathodes surface-treated using yttria-stabilized zirconia (YSZ) nano-particulates fabricated by atomic layer deposition (ALD). Fuel cell tests are conducted on gadolinia-doped ceria electrolyte pellets with a platinum anode at 250-450 °C. In our tests, the fuel cell performance of the SOFCs with an optimized ALD YSZ surface treatment is close to that of SOFCs with porous Pt, which is known as the best performing catalyst in the low-temperature regime. Electrochemical impedance spectroscopy confirms that the performance enhancement is due to improved electrode kinetics by the increase in charge transfer reaction sites between the surface of supporting silver and the ALD-YSZ particulates. Fuel cell durability tests shows that the ALD YSZ surface treatment improves the long-term stability. X-ray photoelectron spectroscopy also confirms that the ALD YSZ capping prevents reduction of the surface silver oxide and destruction of the mesh morphology.

  15. A combinatorial study on catalytic synergism in supported metal catalysts for fuel cell technology

    NASA Astrophysics Data System (ADS)

    Kobayashi, Tetsuhiko; Ueda, Atsushi; Yamada, Yusuke; Shioyama, Hiroshi

    2004-02-01

    In order to accelerate the catalyst development for the increasing demand on the fuel cell technology, it has been attempted to adopt a combinatorial approach. The catalytic synergism, often observed on the supported metal catalysts for the fuel cell utilization, has been subjected to study. It is proposed herein that not only a comparison of catalysts in one reaction, but also the comparison of interrelated reactions by use of a common catalyst library brings about important information to elucidate the catalytic synergism. Preliminary results of the comparison between the water-gas shift reaction and the steam reforming of MeOH on a given set of catalyst library are presented. An important indicator to predict the serendipitous synergism is expected to be obtained from such information by use of artificial intelligence.

  16. Mechanical and electrochemical performance of composite cathode contact materials for solid oxide fuel cells

    SciTech Connect

    Tucker, Michael C.; Dejonghe, Lutgard C.; Garcia-Negron, Valerie; Trejo, Rosa M; Lara-Curzio, Edgar

    2013-01-01

    The feasibility of adding glass or inorganic binder to conventional SOFC cathode contact materials (CCM) in order to improve bonding to adjacent materials in the cell stack is assessed. Two glasses (SEM-COM SCZ-8 and Schott GM31107) and one inorganic binder (Aremco 644A) are mixed with LSM particles to produce composite CCM pastes. These are used to bond Mn1.5Co1.5O4-coated stainless steel mesh current collectors to anode-supported button cells. The cells are operated at 800 C for about 1000 h. The cell with SCZ-8 addition to the CCM displays quite stable operation (3.9%/1000 h degradation), whereas the other additives lead to somewhat higher degradation rate. Bonding of the CCM to coated stainless steel coupons is also assessed. Interfacial fracture toughness is determined using a four-point bend test. The fracture toughness for LSM Schott glass (12.3 N mm 1), LSM SCZ-8 glass (6.8 N mm 1) and LSM 644A binder (5.4 N mm 1) are significantly improved relative to pure LSM (1.7 N mm 1). Indeed, addition of binder or glass is found to improve bonding of the CCM layer without sacrificing cell performance.

  17. Methods for using novel cathode and electrolyte materials for solid oxide fuel cells and ion transport membranes

    DOEpatents

    Jacobson, Allan J.; Wang, Shuangyan; Kim, Gun Tae

    2016-01-12

    Methods using novel cathode, electrolyte and oxygen separation materials operating at intermediate temperatures for use in solid oxide fuel cells and ion transport membranes include oxides with perovskite related structures and an ordered arrangement of A site cations. The materials have significantly faster oxygen kinetics than in corresponding disordered perovskites.

  18. Method of making metal-polymer composite catalysts

    DOEpatents

    Zelena, Piotr; Bashyam, Rajesh

    2009-06-23

    A metal-polymer-carbon composite catalyst for use as a cathode electrocatalyst in fuel cells. The catalyst includes a heteroatomic polymer; a transition metal linked to the heteroatomic polymer by one of nitrogen, sulfur, and phosphorus, and a recast ionomer dispersed throughout the heteroatomic polymer-carbon composite. The method includes forming a heteroatomic polymer-carbon composite and loading the transition metal onto the composite. The invention also provides a method of making a membrane electrode assembly for a fuel cell that includes the metal-polymer-carbon composite catalyst.

  19. Graphene cathode-based ZnO nanowire hybrid solar cells.

    PubMed

    Park, Hyesung; Chang, Sehoon; Jean, Joel; Cheng, Jayce J; Araujo, Paulo T; Wang, Mingsheng; Bawendi, Moungi G; Dresselhaus, Mildred S; Bulović, Vladimir; Kong, Jing; Gradečak, Silvija

    2013-01-01

    Growth of semiconducting nanostructures on graphene would open up opportunities for the development of flexible optoelectronic devices, but challenges remain in preserving the structural and electrical properties of graphene during this process. We demonstrate growth of highly uniform and well-aligned ZnO nanowire arrays on graphene by modifying the graphene surface with conductive polymer interlayers. On the basis of this structure, we then demonstrate graphene cathode-based hybrid solar cells using two different photoactive materials, PbS quantum dots and the conjugated polymer P3HT, with AM 1.5G power conversion efficiencies of 4.2% and 0.5%, respectively, approaching the performance of ITO-based devices with similar architectures. Our method preserves beneficial properties of graphene and demonstrates that it can serve as a viable replacement for ITO in various photovoltaic device configurations. PMID:23205637

  20. Preparation of Carbon-Platinum-Ceria and Carbon-Platinum-Cerium catalysts and its application in Polymer Electrolyte Fuel Cell: Hydrogen, Methanol, and Ethanol

    NASA Astrophysics Data System (ADS)

    Guzman Blas, Rolando Pedro

    This thesis is focused on fuel cells using hydrogen, methanol and ethanol as fuel. Also, in the method of preparation of catalytic material for the anode: Supercritical Fluid Deposition (SFD) and impregnation method using ethylenediaminetetraacetic acid (EDTA) as a chelating agent. The first part of the thesis describes the general knowledge about Hydrogen Polymer Exchange Membrane Fuel Cell (HPEMFC),Direct Methanol Fuel Cell (DMFC) and Direct Ethanol Fuel Cell (DEFC), as well as the properties of Cerium and CeO2 (Ceria). The second part of the thesis describes the preparation of catalytic material by Supercritical Fluid Deposition (SFD). SFD was utilized to deposit Pt and ceria simultaneously onto gas diffusion layers. The Pt-ceria catalyst deposited by SFD exhibited higher methanol oxidation activity compared to the platinum catalyst alone. The linear sweep traces of the cathode made for the methanol cross over study indicate that Pt-Ceria/C as the anode catalyst, due to its better activity for methanol, improves the fuel utilization, minimizing the methanol permeation from anode to cathode compartment. The third and fourth parts of the thesis describe the preparation of material catalytic material Carbon-Platinum-Cerium by a simple and cheap impregnation method using EDTA as a chelating agent to form a complex with cerium (III). This preparation method allows the mass production of the material catalysts without additional significant cost. Fuel cell polarization and power curves experiments showed that the Carbon-Platinum-Cerium anode materials exhibited better catalytic activity than the only Vulcan-Pt catalysts for DMFC, DEFC and HPEMFC. In the case of Vulcan-20%Pt-5%w Cerium, this material exhibits better catalytic activity than the Vulcan-20%Pt in DMFC. In the case of Vulcan-40% Pt-doped Cerium, this material exhibits better catalytic activity than the Vulcan-40% Pt in DMFC, DEFC and HPEMFC. Finally, I propose a theory that explains the reason why the

  1. Development of a standard bench-scale cell for electrochemical studies on inert anodes. Inert Anode/Cathode Program

    SciTech Connect

    Windisch, C.F. Jr.; Boget, D.I.

    1986-07-01

    Objective of this work was to develop a standard bench-scale cell for performing short-term ac and dc polarization studies on inert anode candidate materials in molten cryolite. Two designs for electrochemical cells were developed and successfully evaluated in short-term experiments. Both cells consisted on the inert anode as a small cylindrical specimen partially sheathed in alumina, an Al/Al/sub 2/O/sub 3/ reference electrode, and a cryolite bath saturated in alumina. The difference between the two cells was in the design of the cathode. One cell used a bare solid metal cathode; the other used an aluminum pad similar to the Hall-Heroult configuration.

  2. An Aurivillius Oxide Based Cathode with Excellent CO2 Tolerance for Intermediate-Temperature Solid Oxide Fuel Cells.

    PubMed

    Zhu, Yinlong; Zhou, Wei; Chen, Yubo; Shao, Zongping

    2016-07-25

    The Aurivillius oxide Bi2 Sr2 Nb2 MnO12-δ (BSNM) was used as a cobalt-free cathode for intermediate-temperature solid oxide fuel cells (IT-SOFCs). To the best of our knowledge, the BSNM oxide is the only alkaline-earth-containing cathode material with complete CO2 tolerance that has been reported thus far. BSNM not only shows favorable activity in the oxygen reduction reaction (ORR) at intermediate temperatures but also exhibits a low thermal expansion coefficient, excellent structural stability, and good chemical compatibility with the electrolyte. These features highlight the potential of the new BSNM material as a highly promising cathode material for IT-SOFCs. PMID:27294808

  3. Scaled-down particle-in-cell simulation of cathode plasma expansion in magnetically insulated coaxial diode

    NASA Astrophysics Data System (ADS)

    Zhu, Danni; Zhang, Jun; Zhong, Huihuang; Cai, Dan

    2016-03-01

    The expansion of cathode plasma in magnetically insulated coaxial diode (MICD) is investigated in theory and particle-in-cell (PIC) simulation. The temperature and density of the cathode plasma are about several eV and 1013-1016 cm-3, respectively, and its expansion velocity is of the level of few cm/μs. Through hydrodynamic theory analysis, expressions of expansion velocities in axial and radial directions are obtained. The characteristics of cathode plasma expansion have been simulated through scaled-down PIC models. Simulation results indicate that the expansion velocity is dominated by the ratio of plasma density other than the static electric field. The electric field counteracts the plasma expansion reverse of it. The axial guiding magnetic field only reduces the radial transport coefficients by a correction factor, but not the axial ones. Both the outward and inward radial expansions of a MICD are suppressed by the much stronger guiding magnetic field and even cease.

  4. Catalyzed electrochemical gasification of carbonaceous materials at anode and electrowinning of metals at cathode

    SciTech Connect

    Vaughan, R.J.

    1983-09-20

    The electrochemical gasification reaction of carbonaceous materials by anodic oxidation in an aqueous acidic electrolyte to produce oxides of carbon at the anode and metallic elements at the cathode of an electrolysis cell is catalyzed by the use of an iron catalyst.

  5. Diesel steam reforming with a nickel-alumina spinel catalyst for solid oxide fuel cell application

    NASA Astrophysics Data System (ADS)

    Fauteux-Lefebvre, Clémence; Abatzoglou, Nicolas; Braidy, Nadi; Achouri, Ines Esma

    Liquid hydrocarbons (LC) are considered as fuel cells feed and, more particularly, as solid oxide fuel cell feed. Cost-effective LC-reforming catalysts are critically needed for the successful commercialization of such technologies. An alternative to noble metal catalysts, proposed by the authors in a previous publication, has been proven efficient for diesel steam reforming (SR). Nickel, less expensive and more readily available than noble metals, was used in a form that prevents deactivation. The catalyst formulation is a Ni-alumina spinel (NiAl 2O 4) supported on alumina (Al 2O 3) and yttria-stabilized zirconia (YSZ). SR of commercial diesel was undertaken for more than 15 h at high gas hourly space velocities and steam-to-carbon ratios lower than 2. Constant diesel conversion and high hydrogen concentrations were obtained. Ni catalyst characterization revealed no detectable amounts of carbon on the spinel catalyst surface Ni. The effect of catalyst composition (Ni concentration and YSZ presence) was studied to understand and optimize the developed catalyst. Two phenomena were found to be influenced by relative catalyst composition: water-gas-shift vs reforming reaction extent, and concentration of light hydrocarbons in products.

  6. Electro-thermal impedance spectroscopy applied to an open-cathode polymer electrolyte fuel cell

    NASA Astrophysics Data System (ADS)

    Engebretsen, Erik; Robinson, James B.; Obeisun, Oluwamayowa; Mason, Tom; Finegan, Donal; Hinds, Gareth; Shearing, Paul R.; Brett, Daniel J. L.

    2016-01-01

    The development of in-situ diagnostic techniques is critical to ensure safe and effective operation of polymer electrolyte fuel cell systems. Infrared thermal imaging is an established technique which has been extensively applied to fuel cells; however, the technique is limited to measuring surface temperatures and is prone to errors arising from emissivity variations and reflections. Here we demonstrate that electro-thermal impedance spectroscopy can be applied to enhance infrared thermal imaging and mitigate its limitations. An open-cathode polymer electrolyte fuel cell is used as a case study. The technique operates by imposing a periodic electrical stimulus to the fuel cell and measuring the consequent surface temperature response (phase and amplitude). In this way, the location of heat generation from within the component can be determined and the thermal conduction properties of the materials and structure between the point of heat generation and the point of measurement can be determined. By selectively 'locking-in' to a suitable modulation frequency, spatially resolved images of the relative amplitude between the current stimulus and temperature can be generated that provide complementary information to conventional temporal domain thermograms.

  7. Novel pore-filled polyelectrolyte composite membranes for cathodic microbial fuel cell application

    NASA Astrophysics Data System (ADS)

    Gohil, J. M.; Karamanev, D. G.

    2013-12-01

    Novel pore-filled polyelectrolyte membrane (PEM) was produced using track etched polycarbonate (PC) as porous substrate and poly(vinyl alcohol) (PVA) as pore filling material. PVA in PC pores was stabilized through cross-linking of PVA matrix with glutaraldehyde (GA). Cross-link time was varied from 24 h to 96 h while keeping the membranes in GA solution. Pore sizes of substrate PC membrane tested were 0.01, 0.1 and 0.2 μm. The membranes were characterized by Fourier-transform infrared spectroscopy and scanning electron microscopy. Ionic conductivity, water uptake, contact angle and gel content have been measured to determine membranes performance. The ionic crossover (iron ions and protons) through membranes was studied in a complete fuel cell. The single-cell performance of membrane was tested in a cathodic microbial fuel cell (MFC, Biogenerator). The physiochemical properties and membranes fuel cell performance were highly depended on the cross-link density of PVA matrices. Membranes cross-liked with GA for 72 h showed maximum gel content and their peak power density has reached 110 mW cm-2 at current density of 378 mA cm-2. Among all, membrane cross-linked for 72 h was studied for continuous long-term stability, which showed consistency for application in MFC.

  8. Enhanced human bone marrow mesenchymal stem cell functions on cathodic arc plasma-treated titanium.

    PubMed

    Zhu, Wei; Teel, George; O'Brien, Christopher M; Zhuang, Taisen; Keidar, Michael; Zhang, Lijie Grace

    2015-01-01

    Surface modification of titanium for use in orthopedics has been explored for years; however, an ideal method of integrating titanium with native bone is still required to this day. Since human bone cells directly interact with nanostructured extracellular matrices, one of the most promising methods of improving titanium's osseointegration involves inducing bio-mimetic nanotopography to enhance cell-implant interaction. In this regard, we explored an approach to functionalize the surface of titanium by depositing a thin film of textured titanium nanoparticles via a cathodic arc discharge plasma. The aim is to improve human bone marrow mesenchymal stem cell (MSC) attachment and differentiation and to reduce deleterious effects of more complex surface modification methods. Surface functionalization was analyzed by scanning electron microscopy, atomic force microscopy, contact angle testing, and specific protein adsorption. Scanning electron microscopy and atomic force microscopy examination demonstrate the deposition of titanium nanoparticles and the surface roughness change after coating. The specific fibronectin adsorption was enhanced on the modified titanium surface that associates with the improved hydrophilicity. MSC adhesion and proliferation were significantly promoted on the nanocoated surface. More importantly, compared to bare titanium, greater production of total protein, deposition of calcium mineral, and synthesis of alkaline phosphatase were observed from MSCs on nanocoated titanium after 21 days. The method described herein presents a promising alternative method for inducing more cell favorable nanosurface for improved orthopedic applications. PMID:26677327

  9. Solid Oxide Fuel Cell Cathodes. Unraveling the Relationship Between Structure, Surface Chemistry and Oxygen Reduction

    SciTech Connect

    Gopalan, Srikanth

    2013-03-31

    In this work we have considered oxygen reduction reaction on LSM and LSCF cathode materials. In particular we have used various spectroscopic techniques to explore the surface composition, transition metal oxidation state, and the bonding environment of oxygen to understand the changes that occur to the surface during the oxygen reduction process. In a parallel study we have employed patterned cathodes of both LSM and LSCF cathodes to extract transport and kinetic parameters associated with the oxygen reduction process.

  10. Improving the performance of a biofuel cell cathode with laccase-containing culture supernatant from Pycnoporus sanguineus.

    PubMed

    Fokina, Oleksandra; Eipper, Jens; Winandy, Lex; Kerzenmacher, Sven; Fischer, Reinhard

    2015-01-01

    Laccases are multicopper oxidoreductases that can be used in biofuel cells to improve cathode performance by cathodic oxygen reduction. Here we present a laccase from the ligninolytic white-rot fungus Pycnoporus sanguineus that, in contrast to the Trametes versicolor laccase, can be produced in the absence of inducers in a standard culture medium. After 7days of cultivation the activity of this laccase in culture supernatant reached 2.5U/ml, which is high enough for direct application of the supernatant in biofuel cells. The highest current density of 115.0±3.5μA/cm(2) at 400mV vs. SCE was obtained at pH 5 with a buckypaper cathode with a laccase-containing culture supernatant. The enzyme also showed electrocatalytic activity at pH 6 and 7. These results not only present a new cost-efficient laccase for improving cathode performance, but also show that new laccases with different catalytic properties can be suitable for biofuel cells. PMID:25459854

  11. Insight into the structure and functional application of the Sr0.95Ce0.05CoO3-δ cathode for solid oxide fuel cells.

    PubMed

    Yang, Wei; Zhang, Huairuo; Sun, Chunwen; Liu, Lilu; Alonso, J A; Fernández-Díaz, M T; Chen, Liquan

    2015-04-01

    A new perovskite cathode, Sr0.95Ce0.05CoO3-δ, performs well for oxygen-reduction reactions in solid oxide fuel cells (SOFCs). We gain insight into the crystal structure of Sr1-xCexCoO3-δ (x = 0.05, 0.1) and temperature-dependent structural evolution of Sr0.95Ce0.05CoO3-δ by X-ray diffraction, neutron powder diffraction, and scanning transmission electron microscopy experiments. Sr0.9Ce0.1CoO3-δ shows a perfectly cubic structure (a = a0), with a large oxygen deficiency in a single oxygen site; however, Sr0.95Ce0.05CoO3-δ exhibits a tetragonal perovskite superstructure with a double c axis, defined in the P4/mmm space group, that contains two crystallographically different cobalt positions, with distinct oxygen environments. The structural evolution of Sr0.95Ce0.05CoO3-δ at high temperatures was further studied by in situ temperature-dependent NPD experiments. At 1100 K, the oxygen atoms in Sr0.95Ce0.05CoO3-δ show large and highly anisotropic displacement factors, suggesting a significant ionic mobility. The test cell with a La0.8Sr0.2Ga0.83Mg0.17O3-δ-electrolyte-supported (∼300 μm thickness) configuration yields peak power densities of 0.25 and 0.48 W cm(-2) at temperatures of 1023 and 1073 K, respectively, with pure H2 as the fuel and ambient air as the oxidant. The electrochemical impedance spectra evolution with time of the symmetric cathode fuel cell measured at 1073 K shows that the Sr0.95Ce0.05CoO3-δ cathode possesses superior ORR catalytic activity and long-term stability. Mixed ionic-electronic conduction properties of Sr0.95Ce0.05CoO3-δ account for its good performance as an oxygen-reduction catalyst. PMID:25756843

  12. Oxygen-consuming chlor alkali cell configured to minimize peroxide formation

    DOEpatents

    Chlistunoff, Jerzy B.; Lipp, Ludwig; Gottesfeld, Shimshon

    2006-08-01

    Oxygen-consuming zero gap chlor-alkali cell was configured to minimize peroxide formation. The cell included an ion-exchange membrane that divided the cell into an anode chamber including an anode and a cathode chamber including an oxygen gas diffusion cathode. The cathode included a single-piece of electrically conducting graphitized carbon cloth. Catalyst and polytetrafluoroethylene were attached to only one side of the cloth. When the cathode was positioned against the cation exchange membrane with the catalyst side away from the membrane, electrolysis of sodium chloride to chlorine and caustic (sodium hydroxide) proceeded with minimal peroxide formation.

  13. Improvement of activated carbons as oxygen reduction catalysts in neutral solutions by ammonia gas treatment and their performance in microbial fuel cells

    NASA Astrophysics Data System (ADS)

    Watson, Valerie J.; Nieto Delgado, Cesar; Logan, Bruce E.

    2013-11-01

    Commercially available activated carbon (AC) powders from different precursor materials (peat, coconut shell, coal, and hardwood) were treated with ammonia gas at 700 °C to improve their performance as oxygen reduction catalysts in neutral pH solutions used in microbial fuel cells (MFCs). The ammonia treated ACs exhibited better catalytic performance in rotating ring-disk electrode tests than their untreated precursors, with the bituminous based AC most improved, with an onset potential of Eonset = 0.12 V (untreated, Eonset = 0.08 V) and n = 3.9 electrons transferred in oxygen reduction (untreated, n = 3.6), and the hardwood based AC (treated, Eonset = 0.03 V, n = 3.3; untreated, Eonset = -0.04 V, n = 3.0). Ammonia treatment decreased oxygen content by 29-58%, increased nitrogen content to 1.8 atomic %, and increased the basicity of the bituminous, peat, and hardwood ACs. The treated coal based AC cathodes had higher maximum power densities in MFCs (2450 ± 40 mW m-2) than the other AC cathodes or a Pt/C cathode (2100 ± 1 mW m-2). These results show that reduced oxygen abundance and increased nitrogen functionalities on the AC surface can increase catalytic performance for oxygen reduction in neutral media.

  14. High performance catalyzed-reaction layer for medium temperature operating solid oxide fuel cells. 3: Effects of composition and morphology on performance of anode and cathode layers

    SciTech Connect

    Watanabe, Masahiro; Uchida, Hiroyuki; Suzuki, Hiroaki; Tsuno, A.

    1995-12-31

    Polarization properties of catalyzed-reaction layers, which the authors developed for medium temperature operating SOFC, were greatly improved by controlling their compositions and microstructures. The amount of Pt catalysts loaded on Sr-doped LaMnO{sub 3} (LSM) cathode was reduced down to 1/5 by decreasing size of Pt particles. A large depolarizing effect was observed on the Pt-catalyzed LSM cathode, especially at high current densities. The anodic overpotential for the samaria-doped ceria (SDC) layer was appreciably lowered by applying both highly dispersed Ru microcrystals and 0.1{micro}m-sized SDC particles onto the SDC layer.

  15. Analysis of multi-phase transport phenomena with catalyst reactions in polymer electrolyte membrane fuel cells - A review

    NASA Astrophysics Data System (ADS)

    Khan, Munir Ahmed; Sundén, Bengt; Yuan, Jinliang

    2011-10-01

    A review is presented for two-phase modeling approaches to study various transport processes and reactions in polymer electrolyte membrane (PEM) fuel cells along with some experimental work. It has been noted that water management is still one of the least accurate modeled phenomena. The lackness in complete descriptive models for water management inside PEM fuel cells can be attributed to the complexity of the phenomena, lack of empirical or measured data and non-availability of apt governing equations. Another discrepancy found in present models is the proper validation of the numerical work as it has been observed that mere comparison with V-I curve can sometimes lead to misguided conclusions. Additionally, keeping in mind the multi-scale nature of a PEM fuel cell, application of the Lattice Boltzmann (LB) method has also been reviewed in this work and it was noticed that LB methods offer bright perspective at meso-scale by incorporating details of local structure. Furthermore, a brief description of the catalyst layer models is also presented with some technological developments at nano-scale to improve the physio- and electro-chemical properties. A test case for a 2D PEM cathode is also simulated for different operating voltages to predict the water saturation effects.

  16. Metal foams application to enhance cooling of open cathode polymer electrolyte membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Sajid Hossain, Mohammad; Shabani, Bahman

    2015-11-01

    Conventional channel flow fields of open cathode Polymer Electrolyte Membrane Fuel Cells (PEMFCs) introduce some challenges linked to humidity, temperature, pressure and oxygen concentration gradients along the conventional flow fields that reduce the cell performance. According to previous experimental reports, with conventional air flow fields, hotspot formation due to water accumulation in Gas Diffusion Layer (GDL) is common. Unlike continuous long flow passages in conventional channels, metal foams provide randomly interrupted flow passages. Re-circulation of fluid, due to randomly distributed tortuous ligaments, enhances temperature and humidity uniformity in the fluid. Moreover, the higher electrical conductivity of metal foams compared to non-metal current collectors and their very low mass density compared to solid metal materials are expected to increase the electrical performance of the cell while significantly reducing its weight. This article reviews the existing cooling systems and identifies the important parameters on the basis of reported literature in the air cooling systems of PEMFCs. This is followed by investigating metal foams as a possible option to be used within the structure of such PEMFCs as an option that can potentially address cooling and flow distribution challenges associated with using conventional flow channels, especially in air-cooled PEMFCs.

  17. Enhanced human bone marrow mesenchymal stem cell functions on cathodic arc plasma-treated titanium

    PubMed Central

    Zhu, Wei; Teel, George; O’Brien, Christopher M; Zhuang, Taisen; Keidar, Michael; Zhang, Lijie Grace

    2015-01-01

    Surface modification of titanium for use in orthopedics has been explored for years; however, an ideal method of integrating titanium with native bone is still required to this day. Since human bone cells directly interact with nanostructured extracellular matrices, one of the most promising methods of improving titanium’s osseointegration involves inducing bio-mimetic nanotopography to enhance cell–implant interaction. In this regard, we explored an approach to functionalize the surface of titanium by depositing a thin film of textured titanium nanoparticles via a cathodic arc discharge plasma. The aim is to improve human bone marrow mesenchymal stem cell (MSC) attachment and differentiation and to reduce deleterious effects of more complex surface modification methods. Surface functionalization was analyzed by scanning electron microscopy, atomic force microscopy, contact angle testing, and specific protein adsorption. Scanning electron microscopy and atomic force microscopy examination demonstrate the deposition of titanium nanoparticles and the surface roughness change after coating. The specific fibronectin adsorption was enhanced on the modified titanium surface that associates with the improved hydrophilicity. MSC adhesion and proliferation were significantly promoted on the nanocoated surface. More importantly, compared to bare titanium, greater production of total protein, deposition of calcium mineral, and synthesis of alkaline phosphatase were observed from MSCs on nanocoated titanium after 21 days. The method described herein presents a promising alternative method for inducing more cell favorable nanosurface for improved orthopedic applications. PMID:26677327

  18. Two-phase flow modeling for the cathode side of a polymer electrolyte fuel cell

    NASA Astrophysics Data System (ADS)

    Qin, Chaozhong; Rensink, Dirk; Fell, Stephan; Majid Hassanizadeh, S.

    2012-01-01

    Liquid water flooding in micro gas channels is an important issue in the water management of polymer electrolyte fuel cells (PEFCs). However, in most previous numerical studies liquid water transport in the gas channels (GC) has been simplified by the mist flow assumption. In this work, we present a two-phase flow model for the cathode side of a PEFC. The GC is assumed to be a structured porous medium with the porosity of 1.0. The two-phase Darcy's law is applied to both diffusion layers and GC. Based on the developed model, the liquid water flooding in the GC and its impact on the liquid water distribution in the diffusion layers are explored in detail. Furthermore, we study the effect of the immobile saturation on the predicted liquid water distribution in the diffusion layers. The results show that neglecting the GC flooding leads to an incorrect prediction of liquid water distribution in the diffusion layers and an overestimation of the cell performance. The gas flow rate in the GC can be optimized to achieve the best cell performance. Finally, when considering the immobile saturation in the model, more liquid water is predicted in the diffusion layers.

  19. 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

  20. Al-TiO₂ composite-modified single-layer graphene as an efficient transparent cathode for organic solar cells.

    PubMed

    Zhang, Di; Xie, Fengxian; Lin, Peng; Choy, Wallace C H

    2013-02-26

    While there are challenges in tuning the properties of graphene (surface wettability, work function alignment, and carrier transport) for realizing an efficient graphene cathode in organic solar cells (OSCs), we propose and demonstrate using an Al-TiO₂ composite to modify single-layer graphene as an efficient cathode for OSCs. To unveil the contributions of the composite in addressing the aforementioned challenges, the evaporated aluminum nanoclusters in the composite benefit the graphene cathode by simultaneously achieving two roles of improving its surface wettability for subsequent TiO₂ deposition and reducing its work function to offer better energy alignment. To address challenges related to charge transport, solution-processed TiO₂ with excellent electron transport can offer charge extraction enhancement to the graphene cathode, which is essential to efficient devices. However, it is a well-known issue for methods such as spin-coating to produce uniform films on the initially hydrophobic graphene, even with improved wettability. The undesirable morphology of TiO₂ by such methods considerably inhibits its effectiveness in enhancing charge extraction. We propose a self-assembly method to deposit the solution-processed TiO₂ on the Al-covered graphene for forming the Al-TiO₂ composite. Compared with spin-coating, the self-assembly method is found to achieve more uniform coating on the graphene surface, with highly controllable thickness. Consequently, the graphene cathode modified with the Al-TiO₂ composite in inverted OSCs gives rise to enhanced power conversion efficiency of 2.58%, which is 2-fold of the previously best reported efficiency (1.27%) for graphene cathode OSCs, reaching ∼75% performance of control devices using indium tin oxide. PMID:23327464