Suppression of Methanol and Formate Crossover through Sulfanilic‐Functionalized Holey Graphene as Proton Exchange Membranes

Abstract Proton exchange membranes with high proton conductivity and low crossover of fuel molecules are required to realize advanced fuel‐cell technology. The selective transportation of protons, which occurs by blocking the transportation of fuel molecules across a proton exchange membrane, is crucial to suppress crossover while maintaining a high proton conductivity. In this study, a simple yet powerful method is proposed for optimizing the crossover‐conductivity relationship by pasting sulfanilic‐functionalized holey graphenes onto a Nafion membrane. The results show that the sulfanilic‐functionalized holey graphenes supported by the membrane suppresses the crossover by 89% in methanol and 80% in formate compared with that in the self‐assembled Nafion membrane; an ≈60% reduction is observed in the proton conductivity. This method exhibits the potential for application in advanced fuel cells that use methanol and formic acid as chemical fuels to achieve high energy efficiency.