Proton conductivity and structural properties of precursors mixed PVA/PWA-based hybrid composite membranes

A new class of hybrid nanocomposite membranes containing poly(vinyl alcohol) (PVA), phosphotungstic acid (PWA), 3-glycidyloxypropyltrimethoxysilane (GPTMS), 3-mercaptopropyltrimethoxysilane (MPTMS) and glutaraldehyde (GA) were prepared by a sol-gel method. The aim of this research study was to investigate these novel and highly proton-conducting membranes including their properties, and performances for proton exchange membrane fuel cells (PEMFCs) operating at low temperature. 'Swelling' was observed at room temperature for all the composites. The manner in which the conductivity depended on temperature and humidity was determined and a maximum conductivity value of 2.5 x 10(-2) S cm(-1) was found at a 140A degrees C and 30 % relative humidity (RH) for the PVA/PWA/GPTMS/MPTMS/P2O5/GA (50/5/15/10/10/10 wt.%) hybrid composite membrane. It was suggested that the conductivity depended strongly on the nature of the organic/inorganic components as well as on the acid concentration. X-ray diffraction (XRD) results demonstrated that this membrane had an amorphous phase, and Fourier transform infrared spectroscopy (FTIR) results confirmed the composite formation. Finally, membrane-electrode assemblies with a loading of 0.1 mg cm(-2) of Pt/C on a prepared electrode gave rise to a current density of 309 mA cm(-2) at 0.5 V.