Sulfo ethyl cellulose/Nafion composite for high‐temperature proton exchange membrane

Abstract

This study investigated the potential enhancement of proton conductivity in Nafion membranes through the incorporation of sulfo ethyl cellulose (SEC) at varying weight ratios (5 and 10 wt.%). Results indicated that increasing the weight ratio of SEC led to improvements in water absorption, activation energy, and proton conductivity within the composite membranes. Specifically, the composite membrane exhibited a significant increase in proton conductivity, reaching up to 170 mS cm−1, in contrast to the pristine Nafion membrane which recorded 40.08 mS cm−1, particularly at temperatures exceeding 120°C. At the sub‐molecular level, Fourier transfer inferred spectroscopy (FTIR) analysis of Nafion/SEC membranes unveiled cross‐linking interactions occurring between the sulfo acid groups of Nafion chains and the hydroxyls within the SEC matrix. Moreover, X‐ray diffraction (XRD) findings of the composite membranes were instrumental in identifying crystalline phases, orientation, and structural features. The results indicated variations in atomic radius and alterations in lattice parameters at the nanoscale, induced by heightened surface forces resulting from the inclusion of SEC in the Nafion matrix. This phenomenon leads to a reduction in crystallite size, accompanied by an increase in peak broadening and surface area within the composite membranes. Such changes signify a clear interaction between SEC and Nafion, as confirmed by both scanning electron microscopy and thermal gravimetry analyses. Taken together, these findings strongly indicate that the cross‐linked composite membranes utilizing SEC‐Nafion hold significant promise as proton exchange membranes.