Degradation analyses of Ru85Se15 catalyst layer in proton exchange membrane fuel cells

► The lowest performance loss of 44% obtained with 0.27 mg Ru cm−2 and 33% Nafion. ► Degradation mechanism of MEAs with Ru85Se15 catalysts in fuel cells. ► Effects of Ru and Nafion loads in the catalyst layer on cell degradation. ► The dissolutions and migrations of Se and Ru proved by SEM, HRTEM and EDX analyses.