Herein, graphene oxide nanosheets (GO) were synthesized and employed as an additive at various proportions to fabricate a novel cation exchange membrane based on grafted cellulose acetate with sodium 4-styrenesulfonate (GCA) via a solution casting method for direct methanol fuel cell (DMFC) applications. The structure of composite membranes has been examined using FTIR, TGA, SEM, and DSC. The physicochemical properties of the GCA/GO membranes, such as ion exchange capacity, water uptake, mechanical and chemical stability, methanol permeability, and proton conductivity, were measured. The inclusion of GO significantly improved the ability to block methanol, contributing to the observed effects. Among the several composite membranes developed, GCA/GO (2 wt.%) had the highest selectivity with a water uptake of 45%, proton conductivity of 5.99 × 10−3 S/cm, methanol permeability of 1.12 × 10−7 cm2/s, and electrical selectivity of 26.39 × 103 Ss/cm3. Simultaneously, the composite membranes’ mechanical, oxidative, and thermal stabilities were also enhanced. Single-cell estimation using a 2 wt.% GO modified membrane demonstrated a maximum power density of 31.85 mW.cm−2 at 30 °C. Overall, these findings highlight the perspective of the application of these developed membranes in the DMFC.

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