Modification of the commercial polymer electrolyte membrane(PEM) Nafion 117 byγ-ray irradiation to produce an improved proton exchange membrane for direct methanol fuel cells(DMFCs) was described.The Nafion 117 membrane was exposed under 7-ray irradiation circumstance with the irradiation doses from 10~3 to 10~5 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 Nafion 117 membrane was exposed underγ-ray irradiation circumstance,the degradation and crosslinking reactions occurred at the same time.Specific scopes of theγ-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 Nafion 117 membrane produced reasonable power density performance as high as 32 W/m^2 under 2 mol/L methanol solution at room temperature.
