High Selectivity of Sulfonated Graphene Oxide Incorporated Nafion-PVA Membrane for Direct Methanol Fuel Cell

A novel composite membrane was synthesized by incorporating sulfonated graphene oxide (SGO) into Nafion-polyvinyl alcohol (N-PVA) polymer matrix via a green and physical crosslinking process. In the preparation of graphene oxide (GO), different drying methods, including freeze drying and thermal drying, were applied, and highly oxidized GO was selected for the synthesis of SGO. The oxygen-related groups in GO were preserved during freeze-drying, and their participation in sulfonation of GO led to the production of SGO with a satisfactory sulfonation degree. Introducing the as-prepared SGO into N-PV A significantly improved the proton conductivity of membrane by at most 1.4 times, thanks to the sulfonic acid groups that served as building blocks for additional proton transport pathways. N-PV A membrane containing SGO filler also showed a 22.6% improvement in methanol diffusion resistance and a 17.2 % increase in power density compared to recast N afion. The overall functional properties of the N-PVA-SGO composite membrane surpassed the recast Nafion membrane, suggesting the vast potential of the composite membrane as an alternative proton exchange membrane (PEM) for direct methanol fuel cells (DMFCs).