Conductivity of nafion®115 membranes doped with inorganic acids

The influence of doping of Nafion®115 membranes with inorganic acids on the transport characteristics at temperatures from 50 to–80°C was studied. The dependence of the conductivity of these membranes on the acid concentration is nonlinear and correlates well with the ion conductivity of the aqueous solutions of the doping acids. The proton conductivity of the membrane is maximum for the membrane sample kept in 3.4 M sulfuric acid (0.03 S/cm at 20°C). An increase in the concentration of the doping acid solution led to a shift of the phase transition temperature toward lower values: for the samples doped with 5 M acid solutions, the phase transition temperature was below–80°C.