Platinum oxidation responsible for degradation of platinum-cobalt alloy cathode catalysts for polymer electrolyte fuel cells

► Large particles and hot annealing improves Pt-Co alloy catalyst durability. ► The Pt 4f XPS spectra suggests that high Pt(OH)2 contents increase Pt dissolution. ► Applying the potential step of 1.2 V, Pt oxides, PtO and PtO2, were produced. ► Pt-Co alloy catalyst durability can be improved by preventing Pt oxidization.