Computational Insights into Selective Water-Methanol Transport in rGO/PSS Composite Films

Reduced graphene oxide (rGO) wrapped with poly(styrenesulfonate) (PSS) forms a stable hybrid material (rGO/PSS) capable of producing ultrathin films with promising barrier properties for Direct Methanol Fuel Cell (DMFC) applications. These films aim to mitigate methanol crossover, one of the major limitations of DMFC technology. In this work, we investigate the mechanisms underlying the methanol barrier effect of rGO/PSS, while maintaining water permeability. Classical Molecular Dynamics simulations were employed to explore the structural and dynamic properties of rGO/PSS at different polymer ionization fractions in a solvent mixture of water, methanol, and hydronium. The influence of the sulfonation fraction on film self-assembly was analyzed, including its impact on PSS conformation, rGO sheet distribution, and PSS-rGO interactions. Finally, the effect of the rGO/PSS structure on solvent diffusion was investigated, and the mechanisms responsible for the selective transport of methanol were elucidated.