Transient Platinum Oxide Formation and Oxygen Reduction on Carbon-Supported Platinum and Platinum-Alloy Electrocatalysts

Chronoamperometry studies at a fixed potential of 0.9V vs. the reversible hydrogen electrode (RHE) have been performed on three PEM fuel cell catalysts (50 wt.% Pt/C, 30 wt. % PtM1/C and 30 wt. % PtM2/C) on both rotating disk electrodes (RDEs) and membrane electrode assemblies (MEAs), in order to investigate similarities and differences between Pt and Pt-alloy catalysts for transient behavior of the oxygen reduction reaction (ORR). Similar trends of reversible activity degradation were shown for both RDEs and MEAs. Compared to the baseline Pt/C catalyst, alloy catalysts under potential hold were found to have higher oxide coverage and faster oxide-growth rate, with the latter related to their faster transient ORR activity degradation rate. In addition, PtM1/C showed a higher ORR activity than PtM2/C in MEA tests, while the opposite trend was found in RDE tests, which could be attributed to their different transient stability under potential hold.