Reverse-Current Decay in Hydroxide Exchange Membrane Fuel Cells

In proton exchange membrane fuel cells (PEMFCs), the cathode carbon support corrodes during startup and shutdown by reverse-current decay (RCD). We show for the first time that hydroxide exchange membrane fuel cells (HEMFCs) also undergo RCD. We find that decreasing the oxygen reduction reaction (ORR) activity of the anode catalyst mitigates RCD: a Ru anode causes less corrosion than Pt, Ir, and Pd anodes, as expected from their ORR activities. After an intensive 6 h RCD test, an HEMFC based on Ru shows six times lower internal resistance compared to Pt (1.02 vs. 6.01 Ω cm2). Due to its enhanced ORR activity in base, carbon alone can sustain RCD. To minimize RCD the carbon support should be eliminated from the anode catalyst.