Improved proton conductivity and single cell performance of magnetically aligned magnetite-embedded metal-organic framework fillers in sulfonated polyether ether ketone membrane

Randomly dispersed proton-conductive fillers in polymer electrolyte membranes often create tortuous transport pathways that limit through-plane proton conduction. Here, Fe₃O₄-anchored proton-conductive MOF1 (Fe₃O₄@MOF1) was incorporated into SPEEK and magnetically aligned to construct anisotropic proton-transport channels. The aligned SPEEK/Fe₃O₄@MOF1 membrane showed optimum performance at 1 wt% filler, with improved dimensional stability and thermomechanical strength. Under fully hydrated conditions, the aligned membrane achieved a proton conductivity of 96 mS cm−1 at 80 °C and 100% RH, higher than the unaligned membrane, neat SPEEK, and NRE-212. At partially hydrated conditions, it reached 121.42 mS cm−1 at 150 °C and 60% RH, confirming the effectiveness of magnetic alignment in reducing transport resistance. The membrane also delivered the highest peak power density of 41.67 mW cm−2 and exhibited improved stability during 40 h of continuous PEMFC operation. These results demonstrate that magnetic alignment of Fe₃O₄@MOF1 is an effective strategy for developing high-performance SPEEK-based PEMs for operation across a wide range of temperatures and humidity levels.