Anode Aging through Voltage Cycling Induced by H2-Air Fronts during System Start-Up and Shut-Down

Passing a H2/air front through the anode compartment during start-up or shut-down (SUSD) is a major source of degradation for PEMFC systems, due to the severe cathode carbon support oxidation and cathode ECSA loss during the induced reverse current event. In this publication, we quantified the anode degradation in a low temperature proton exchange membrane fuel cell (PEMFC) during SUSD for the first time, occurring predominantly in the form of ECSA loss, measured by cyclic voltammetry on both anode and cathode after aging MEAs by SUSD cycling: after 3200 SUSD cycles, the anode ECSA decreased by ≈43%, while the cathode ECSA decreased by ≈76%. We suggest that the anode ECSA loss derives from the change of gas atmosphere upon the passage of the H2/air front during SUSD, effectively inducing rapid voltage cycles between ≈0 and ≈1 V. Even though the decrease in anode ECSA is lower compared to the cathode, estimates of the HOR overpotential changes due to anode ECSA loss project significant kinetic voltage losses at the anode for ultra-low Pt loadings (≤ 50 µgPt cm-2).