Failure Mode Analysis of Membrane Electrode Assembly (MEA) for PEMFC under Low Humidity Operation

Abstract

The degradation mechanisms and phenomena of membrane electrode assembly (MEA) for proton exchange membrane fuel cell (PEMFC under low humidity operation were investigated by means of several on-line electrochemical methods and transmission electron microscopy (TEM). Electrochemical active surface area (ECSA) of catalyst and hydrogen crossover of MEA were evaluated by cyclic voltagram (CV) and linear sweep voltagram (LSV), respectively. The decrease of catalytic active site and degradation of membrane were evident by ECSA loss and hydrogen crossover rate increase after long-term discharging test. Membrane degradation played the major role for MEAs failure under low humidity operation in this study. The Pt clusters were also observed in the membrane, formed by Pt ions migration and reduction in the membrane, which can react with the crossover gases to produce free radicals that attack membrane and ionomers in the catalyst layer.Those phenomena will drive membrane to rupture and cause a short circuit in MEA. By AST experiments and fluoride release rate results, the MEA with Pt-alloy/C catalyst can show better performance and durability due to its high selectivity on ORR to depress the free radicals formation. Fig. 1. Cross section of PEMFC and full cell reaction. CHEMICAL SOCIETY Fig. 10. OCV holding test of Pt/C and Pt-alloy/C MEA as a function of operation time. Cell temperature 80°C, 30 %RH, 100 sccm (H2)/100 sccm (Air) at anode and cathode side, respectively.