Effect of Dwell Time and Scan Rate during Voltage Cycling on Catalyst Degradation in PEM Fuel Cells

Catalyst degradation in membrane electrode assemblies was studied by voltage cycling in hydrogen/air atmosphere. The loss of electrochemically active surface area (ECSA) was quantified by cyclic voltammetry. The influence of cycle duration and dwell time during square wave voltage cycling on catalyst degradation was investigated, as well as the effect of scan rate on ECSA loss during triangular wave voltage cycling. Degradation rates per voltage cycle increased with longer cycle duration and lower scan rate, while degradation rates normalized to operating time were approximately constant over a wide range of cycle lengths and scan rates. The results suggest that the formation of a (sub-)surface oxide layer and cathodic dissolution are important processes in the platinum dissolution mechanism.