PEG based hybrid composite membranes and their properties for H₂/O₂ fuel cells

Hydrocarbon hybrid membranes of PEG/PMA/MPTMS/SiO₂ and PEG/PMA/MPTMS/SiO₂/GA were fabricated with various amounts of SiO₂ and glutaraldehyde by sol–gel method. The composition of the hybrid membranes was examined by X-ray diffraction patterns, Fourier transform infrared (FTIR) spectra (FTIR-ATR) and proton nuclear magnetic resonance (NMR) techniques. The surface morphology of the cast membranes were analyzed by scanning electron microscopy. The conductivity values for all composites displayed a magnitude of 10⁻³ S cm⁻¹, with greater improvements observed under conditions of various temperature and humidity. The proton conductivity of the composite membranes was measured at various temperatures at 50% RH using electrochemical impedance spectroscopy. In order to understand the proton conducting mechanism, the membranes were also subjected to conductivity measurement over wide RH range at 50 °C. It was observed that the hybrid membranes with glutaraldehyde additive as a crosslinking agent exhibited exceptionally high conductivity values at all RH conditions at 50 °C. The stable proton conductivity values at lower RH conditions indicate that the proton conduction mechanism is of diffusion type.