4 research outputs found
Polybenzimidazole (PBI) Functionalized Nanographene as Highly Stable Catalyst Support for Polymer Electrolyte Membrane Fuel Cells (PEMFCs)
Nanoscale graphenes were used as cathode catalyst supports in proton exchange membrane fuel cells (PEMFCs). Surface-initiated polymerization that covalently bonds polybenzimidazole (PBI) polymer on the surface of graphene supports enables the uniform distribution of the Pt nanoparticles, as well as allows the sealing of the unterminated carbon bonds usually present on the edge of graphene from the chemical reduction of graphene oxide. The nanographene effectively shortens the length of channels and pores for O2 diffusion/water dissipation and significantly increases the primary pore volume. Further addition of p-phenyl sulfonic functional graphitic carbon particles as spacers, increases the specific volume of the secondary pores and greatly improves O2 mass transport within the catalyst layers. The developed composite cathode catalyst of Pt/PBI-nanographene (50 wt%) + SO3H-graphitic carbon black demonstrates a higher beginning of life (BOL) PEMFC performance as compared to both Pt/PBI-nanographene (50 wt%) and Pt/PBI-graphene (50 wt%) + SO3H-graphitic carbon black (GCB). Accelerated stress tests show excellent support durability compared to that of traditional Pt/Vulcan XC72 catalysts, when subjected to 10,000 cycles from 1.0 V to 1.5 V. This study suggests the promise of using PBI-nanographene + SO3H-GCB hybrid supports in fuel cells to achieve the 2020 DOE targets for transportation applications
Electrocatalysis of Oxygen Reduction with in-Situ formed Pt Nano-Rafts on Molybdenum Carbide Support
Proton exchange membrane fuel cell (PEMFC), is a technology that has the
potential to economically replace combustion engines for transport with high
efficiency, and clean (only water emission) energy. The US department of
energy (DOE) identifies two remaining major hurdles to the deployment of this
alternative: cost and durability of the cathode. Reducing the amount of
platinum, still the only material with the needed catalytic activity for oxygen
reduction reaction on the cathode, and the most expensive component, will
help overcome the first problem and the creation of a new, ‘non-carbon’,
more oxidation-resistant catalyst support material could overcome the
second.US Department of Energy, Office of Energy
Efficiency and Renewable Energy, Vehicle Technology and Fuel Cell
Technology Program
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Development of analytical techniques to study H2s poisoning of PEMFCs and components
Polymer electrolyte membrane fuel cells are sensitive to impurities that may be present in either the oxidizer or fuel. H{sub 2}S, even at the ppb level, will have a dramatic and adverse affect on fuel cell performance. Not only is it important to know a particular material's affinity to adsorb H{sub 2}S, when considering materials for PEMFC applications, issues such as permeation and crossover rates also become extremely important Several experimental methods have been developed to quantify H{sub 2}S adsorption onto surfaces and to quantify H{sub 2}S permeation through Nafion(reg.) membranes using readily available and inexpensive Ag/AgS ion probes. In addition to calculating the H{sub 2}S uptake on commonly used XC-72 carbon supports and PtlXC-72 catalysts, the H{sub 2}S permeability through dry and humidified Nafion(reg.) PEMFC membranes was also studied using these specialized techniques. In each ion probe experiment performed, a sulfide anti-oxidant buffer solution was used to trap and concentrate trace quantities of H{sub 2}S during the course of the measurement. Crossover experiments were conducted for up to 24 hours in order to achieve sulfide ion concentrations high enough to be precisely determined by subsequent titration with Pb(NO{sub 3}){sub 2}. By using these techniques, we have confirmed H{sub 2}S crossover in Nafion(reg.) membranes and have calculated preliminary rates of H{sub 2}S crossover
Polybenzimidazole (PBI) Functionalized Nanographene as Highly Stable Catalyst Support for Polymer Electrolyte Membrane Fuel Cells (PEMFCs)
Nanoscale graphenes were used as cathode catalyst supports in proton exchange membrane fuel cells (PEMFCs). Surface-initiated polymerization that covalently bonds polybenzimidazole (PBI) polymer on the surface of graphene supports enables the uniform distribution of the Pt nanoparticles, as well as allows the sealing of the unterminated carbon bonds usually present on the edge of graphene from the chemical reduction of graphene oxide. The nanographene effectively shortens the length of channels and pores for O2 diffusion/water dissipation and significantly increases the primary pore volume. Further addition of p-phenyl sulfonic functional graphitic carbon particles as spacers, increases the specific volume of the secondary pores and greatly improves O2 mass transport within the catalyst layers. The developed composite cathode catalyst of Pt/PBI-nanographene (50 wt%) + SO3H-graphitic carbon black demonstrates a higher beginning of life (BOL) PEMFC performance as compared to both Pt/PBI-nanographene (50 wt%) and Pt/PBI-graphene (50 wt%) + SO3H-graphitic carbon black (GCB). Accelerated stress tests show excellent support durability compared to that of traditional Pt/Vulcan XC72 catalysts, when subjected to 10,000 cycles from 1.0 V to 1.5 V. This study suggests the promise of using PBI-nanographene + SO3H-GCB hybrid supports in fuel cells to achieve the 2020 DOE targets for transportation applications.This article is published as Xin, Le, Fan Yang, Yang Qiu, Aytekin Uzunoglu, Tommy Rockward, Rodney L. Borup, Lia A. Stanciu, Wenzhen Li, and Jian Xie. "Polybenzimidazole (PBI) functionalized nanographene as highly stable catalyst support for polymer electrolyte membrane fuel cells (PEMFCs)." Journal of The Electrochemical Society 163, no. 10 (2016): F1228. DOI: 10.1149/2.0921610jes. Posted with permission.</p