Investigation of Platinum Oxidation in PEM Fuel Cells at Various Relative Humidities

Surface oxidation of Pt cathode of proton exchange membrane (PEM) fuel cells at different relative humidities (RHs) was studied using cyclic voltammetry. The degree of platinum oxidation increased significantly with an increase in RH from 20% to 72%. Holding the cathode at high potentials and exposing it to air instead of resulted in the formation of more platinum oxides. At 20% RH, , and 100°C, both water and oxygen equally contribute to platinum oxidation; at 100% RH, , and 100°C, water produces more than 70% of the platinum oxidation while 30% forms from oxygen.