Development of robust proton exchange membranes using a sPVA–silica composite with different crosslinkers and evaluation of their fuel cell performance

Abstract

Development of high energy conversion and environment-friendly proton exchange membranes is important for the commercial application of fuel cell technologies. The performance of proton exchange membrane fuel cells (PEMFCs) is highly dependent on the physico-chemical properties of the proton exchange membranes. Thus, we have developed sulfonated poly(vinyl alcohol) (sPVA) membranes incorporated with 1.5 mass% of sulfonated nano-silica and then crosslinked with different crosslinkers, such as formaldehyde, glutaraldehyde, poly(styrene sulfonic acid-co-malic acid) (PSSA-MA) and tetraethyl orthosilicate (TEOS). The physico-chemical properties of the resulting crosslinked membranes were investigated using Fourier transform infrared (FT-IR) spectroscopy, wide-angle X-ray diffractometry (WAXD), atomic force microscopy (AFM), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The mechanical properties of the membranes were studied using a universal testing machine (UTM). The proton conductivity and dielectric properties of the membranes were measured using a high precession impedance analyzer. The water uptake ratio, swelling ratio and ion exchange capacity of the membranes were evaluated and discussed based on their molecular structures. The fuel cell performance of the membranes was determined at 80 °C using a fuel cell workstation. Among the membranes developed, the TEOS crosslinked composite membrane (sPVA–Si/TEOS) demonstrated the highest mechanical strength, ion exchange capacity and proton conductivity. The ion exchange capacity and proton conductivity were found to be 1.1 meq g⁻¹ and 0.56 S cm⁻¹, respectively. The same membrane demonstrated the highest power density of 0.70 W cm⁻² at a current density of 1.25 A cm⁻². These data were compared with the commercially available Nafion® 117 and 212 membranes. The sPVA–Si/TEOS composite membrane showed better performance than Nafion® 117 and 212 membranes with greater economic viability. Thus, TEOS could be a potential crosslinker for sulfonated poly(vinyl alcohol)–silica incorporated hydrophilic membranes and could be employed as a promising candidate for fuel cell application.