Modification of the commercial polymer electrolyte membrane （PEM） Nation 117 by γ-ray irradiation to produce an improved proton exchange membrane for direct methanol fuel cells （DMFCs） was described. The Nation 117 membrane was exposed under γ-ray irradiation circumstance with the irradiation doses from 103 to 105 Gy. Subsequently the properties of the membrane itself, in terms of swelling ratio, water uptake rate, proton conductivity and methanol permeability, together with the performance of its membrane electrode assembly （MEA） in DMFC were analyzed and contrasted with the untreated material. When the Nation 117 membrane was exposed under γ-ray irradiation circumstance, the degradation and crosslinking reactions occurred at the same time. Specific scopes of the γ-ray irradiation dose may cause the membrane crosslinking, thus reduce the membrane swelling ratio and decrease the methanol crossover. By reducing the membrane swelling ratio and methanol permeation, the single DMFC with the modified Nation 117 membrane produced reasonable power density performance as high as 32 W/m2 under 2 mol/L methanol solution at room temperature.
