Polymer electrolyte membranes based on sulfonated polysulfone and functionalized layered silicate for direct methanol fuel cell applications

Polymer electrolyte membranes (PEMs) of sulfonated polysulfone (SPSf) and sulfonated montmorillonite (SMMT) have been developed. Sodium montmorillonite (NaMMT) has been sulfonated with 4-sulfophthalic acid and incorporated into the SPSf matrix for further enhancement of proton conductivity. Sulfonation of NaMMT has been confirmed using Fourier transform infrared spectroscopy and X-ray diffraction (XRD) analysis. The XRD patterns proved that the SMMT layers were completely exfoliated within the SPSf matrix. The performances of the PEM in terms of their liquid uptake, oxidative stability, and proton conductivity were investigated. The morphological characterizations have been carried out using scanning electron microscopy and atomic force microscopy. SPSf/SMMT membrane with 5 wt% of SMMT loading showed adequate thermal stability and an improved proton conductivity. The reduction in methanol permeability from 8.9 ×10 −5 cm 2 s −1 to 2.4 × 10 −5 cm 2 s −1 has been observed when SMMT loading content increased from 1 wt% to 5 wt%. Direct methanol fuel cell (DMFC) performance showed a power density value of 49 mW cm −2 for SPSf/SMMT membrane, indicating its candidature for DMFC applications.