Evaluation of methanol crossover in proton-conducting polyphosphazene membranes

Methanol crossover in proton-conducting polyphosphazene membranes was investigated using polymer electrolyte fuel cells. The transport of methanol through a membrane from the lower chamber of the cell to the upper chamber was conducted by molecular diffusion through the polymer structure. It is found that the methanol diffusion coefficients of phenyl phosphonic acid functionalized poly[aryloxyphosphazene] membranes in an aqueous methanol solution were 40 times lower than that of Nafion and 10-20 times lower with respect to sulfonated polyphosphazene membranes.