Fabrication and properties of hybrid membranes based on salts of heteropolyacid, zirconium phosphate and polyvinyl alcohol

The fabrication and properties of a hybrid membrane based on cesium salt of heteropoly acid, zirconium phosphate and polyvinyl alcohol are described. The fabricated membranes were characterized for their intra molecular interaction, thermal stability, surface morphology, water content and surface-charge properties using Fourier transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), water uptake and ion-exchange capacity measurements. These membranes showed reduced methanol crossover (for possible application in DMFC) relative to that of Nafion® 115. At 50% of relative humidity, the protonic conductivity of the hybrid membranes was in the range of 10-3 to 10-2 S cm-1. The feasibility of these hybrid membranes as proton conducting electrolyte in direct methanol fuel cell (DMFC) was investigated and preliminary results are compared with that of Nafion® 115. A maximum power density of 6 mW cm-2 with PVA-ZrP-Cs2STA hybrid membrane was obtained with the cell operated in passive mode at 373 K and atmospheric pressure. Open circuit voltage of the cell operated with hybrid membranes are high compared to that of Nafion® 115 indicating reduced methanol crossover. © 2006 Elsevier B.V. All rights reserved.