Fabrication of Polybenzimidazole Membrane Based on Phosphotungstic Acid Doped For Fuel Cell Application

Abstract

In this study, phosphotungstic acid (PWA) doped polybenzimidazole (PBI) membranes were prepared by solution casting method with different content of PWA (0.05 M, 0.10 M and 0.15 M) for proton exchange membrane fuel cell (PEMFC). PWA was used for improving the properties of high temperature PBI based proton exchange membranes. The effect of inorganic filler on the membrane structural and optical absorption properties were investigated by using attenuated total reflectance fourier transform infrared spectroscopy (ATR-FTIR spectroscopy) and diffuse reflectance ultraviolet visible-spectroscopy (DR-UV Vis spectroscopy). Scanning electron microscopy-energy dispersive X-ray (SEM-EDX) micrograph reveals the dispersion of PWA in the PBI matrices. Electrochemical impedance spectroscopy (EIS) was used to evaluate the proton conductivities of the membranes. The best results are observed when the membrane with composition 25wt% of PBI are doped with 0.15 M PWA gave proton conductivity of 2.32 x 10-11 S/cm which is higher than pristine PBI membrane. The incorporation of PWA in the PBI-based membranes showed improved proton conductivity. It was also found that the fuel cell performance can be improved by optimizing the weight percent of the PBI polymers and content of the acid. Thus, the addition of inorganic heteropolyacid (HPA) into PBI significantly increase the proton conductivity of PBI membranes and can be better candidates for fuel cell application.