Proton conducting membranes composed of phosphotungstic acid (PWA) and poly (vinyl alcohol) (PVA) were prepared. Conductivity and Fourier transform infrared spectrometer (FTIR) measurements show that most of the acid embedded are stable in the PVA matrix when the membrane is immerged in water or methanol solution at room temperature. Conductivity of the composite membranes scatters around 10-3 S-crn-1 at room temperature. The methanol crossover through the membranes is about an order of magnitude lower than that through Nafion 117 membrane.

A mathematic model is established to simulate the effects of methanol crossover on the DMPC. The transport and reactions of both oxygen and methanol at the cathode are described and the theory of "parallel electrode reactions" is applied to calculate the cathode over-potential caused by methanol crossover. The influence of methanol conentration, fuel cell temperature, oxygen pressure, and membrane properties on the cathode over-potential is evaluated. Simulation results show that methanol crossover considerably increases the cathode over-potential at low current density, but its effect is significantly reduced when the current density is increased to reasonable values. It also shows that of the two parameters characterizing a polymer electrolytemembrane, proton conductivity and methanol permeability, the former has more impact on the performance of a DMPC.

A novel composite membrane based on poly (vinyl alcohol) (PVA) with embedded phosphotungstic acid (PWA) were prepared and their proton conductivity and methanol permeability were studied. Infrared (IR) and UV spectrographic measurement indicates that the Keggin structure characteristic of the PW12O403- anion presents in the PVA membranes. Highest proton conductivity of 6.27

A highly ionic conductive solid-gel membrane based on polyacrylamide hydrogels with a K2CO3 additive was investigated. The polymer-based gel was prepared by adding ionic species K2CO3 to a monomer solution followed by polymerization. After polymerization, the ionic species was embedded in the polymer-based gel, where it remained. The ionic species behaved like a liquid electrolyte, whereas the polymer-based solid-gel membrane provided a smooth impenetrable surface that allowed for the exchange of ions. The gel membranes were obtained in the form of thin films of reasonable mechanical strength. Their ambient temperature conductivities were in the range 10-2 to 10-1S/cm. The effect of K2CO3 concentration on the conductivity of the gels prepared was examined in the temperature range from 0 to 100℃. The microstructure and chemical composition of the gels studied were characterized by environmental scanning electron microscopy and FTIR, respectively.