Sulfonated polyether ether ketone/strontium zirconite@TiO2 nanocomposite membranes for direct methanol fuel cells

Abstract

Nanocomposite membranes consisting of sulfonated perovskite-type strontium zirconite (sSrZrO₃) and sSrZrO₃@TiO₂ nanofillers integrated into a sulfonated polyether ether ketone (SPEEK) matrix have been explored as ion-exchange membranes for direct methanol fuel cells (DMFCs). The perovskite fillers improved the thermal and oxidative stabilities of the SPEEK membranes. Due to the hygroscopic characteristics of sSrZrO₃@TiO₂, the SPEEK/sSrZrO₃@TiO₂ nanocomposite membrane adsorbed a large amount of water, which facilitated the dissolution of acid moieties and led to enhanced proton conductivity. The narrower channels formed in the SPEEK/sSrZrO₃@TiO₂ nanocomposite via the uniform distribution of sSrZrO₃@TiO₂ fillers in the SPEEK matrix restricted fuel transport and improved the selectivity ratio of proton conductivity to methanol permeation. A DMFC constructed with the SPEEK/sSrZrO₃@TiO₂ membrane offered superior power and current densities of 140 mW cm⁻² and 639 mA cm⁻², respectively, at 80 °C, compared to those obtained with a Nafion 117 membrane.