Anode Aging during PEMFC Start-Up and Shut-Down: H2-Air Fronts vs Voltage Cycles

Start-upandshut-down(SUSD)eventsinprotonexchangemembranefuelcells(PEMFCs)areamajorsourceofcathodedegradation,causingalossofelectrochemicalsurfacearea( ECSA ) and carbon corrosion. Our study reveals that also the anode suffers significant damage during SUSD, dominated by the loss of ECSA , induced by potential cycling between ≈ 0 and ≈ 1 V upon the passage of H 2 /air fronts. Furthermore, we demonstrate the analogy of SUSD-induced anode degradation and that originating from quasi-square wave potential cycling between 0.05 and 1.05 V RHE . The performance penalties arising from a decrease of the kinetics of the hydrogen oxidation reaction (HOR) and growing H 2 mass-transport resistances are measured via H 2 -pump experiments. The thus projected anode voltage losses for low anode Pt loadings (25 μ g Pt cm − 2 ) predict HOR kinetic losses of ≈ 40 mV at 80 ◦ C and 3 A cm − 2 for aged anode catalyst layers, suggesting that anode degradation by SUSD could be a significant durability issue in future PEMFC systems with ultra-low Pt loadings and with more stable cathode catalyst carbon supports. Moreover, SUSD-induced H 2 mass-transport related overpotentials were identified and attributed to carbon corrosion, indicated by a thinning of the anode catalyst layer upon aging.