Performance and Durability of a Polymer Electrolyte Fuel Cell Operating with Reformate: Effects of CO, CO2, and Other Trace Impurities

The performance and durability of a polymer electrolyte fuel cell (PEFC) operating with reformate is discussed. Brief overviews are given on how dilution affects the thermodynamic driving force and how diffusion of N2 and CO2, two major components in a typical reformate mix, affects the overall voltage. The primary focus is on the impact of CO on the voltage performance of the PEFC, i.e., the anode overpotential at different CO levels. Specifically, the effects of CO concentration and the impact of various CO mitigation methods on durability and degradation are presented. CO/air bleed interactions are discussed in connection with peroxide-induced membrane/ionomer degradation rates. Furthermore, the possibility of in situ anode CO formation from CO2 via the reverse water-gas-shift reaction is assessed for realistic PEFC operating conditions. The discussion includes results obtained at high CO levels and the stability of Pt–Ru catalysts. The impact of trace impurities such as NH3, H2S, and small organic molecules is also described.