Nafion 117 membrane (DuPont) was used as the solid electrolyte. Prior to MEAs fabrication, the pretreatment of Nafion 117 was accomplished and treated in 3 wt.% H2O2 solution, distilled water, 0.5 mol L−1 H2SO4 solution, and then distilled water again, at 80∘C for 1 h each step.