Unveiling the potential of [MIm][HSO4]/Nafion hybrid proton exchange membranes for high-efficiency water electrolysis via combined experimental and molecular simulation

Protic ionic liquids (PILs) serve as efficient proton carriers to enhance the proton conductivity of composite proton exchange membranes (PEMs). However, systematic investigations and durability evaluations of PIL-based PEMs for water electrolysis are insufficient, and their underlying microscopic mechanisms remain ambiguous. Herein, Nafion composite membranes modified with different concentrations of 1-methyl imidazolium hydrogen sulfate ([MIm][HSO 4 ]) were fabricated. The optimized 5% [MIm][HSO 4 ] membrane achieves a 12% enhancement in proton conductivity. Molecular dynamics simulations demonstrate that [MIm][HSO 4 ] induces water accumulation around sulfonic acid groups, constructing interconnected water channels and stable hydrogen-bonding networks to facilitate proton transport. The corresponding membrane electrode assembly delivers 3.8% higher electrolysis efficiency and a low degradation rate of 0.21 mV/h. Further, 96 h constant-current and 24 h dynamic load tests demonstrate the promising durability of the composite membrane.