Non-covalently polyimide-modified few-layer graphene (FLG) as a filler in polysulfone membrane for enhanced H₂/CO₂ separation

Hydrogen is a key energy carrier for achieving Net Zero Emissions (NZE) owing to its carbon-free combustion and high energy efficiency. Membrane-based systems stand out among separation technologies for hydrogen purification due to their efficient energy use and adaptability to scale. In this study, few-layer graphene (FLG) was synthesized through the electrochemical exfoliation of graphite and subsequently modified with polyimide P84 to enhance its compatibility with the polymer matrix. Polyimide-modified FLG was incorporated at low loading into a polysulfone (PSf) membrane, followed by thermal annealing at 250, 300, and 350 °C to assess its impact on the gas separation performance. Single-gas permeation experiments using H₂ and CO₂ revealed that the membrane annealed at 350 °C exhibited superior performance, achieving H₂ and CO₂ permeabilities of 111.75 and 22.51 Barrer, respectively, with an H₂/CO₂ selectivity of 4.96. Compared to the pristine PSf membrane, this represents a 213.32% increase in H₂ permeability and a 25.59% improvement in H₂/CO₂ selectivity, slightly exceeding the Robeson upper bound for polymeric membranes under single gas permeation conditions. These findings demonstrate that the synergistic combination of imide-modified FLG and high-temperature annealing effectively enhances the membrane transport properties, highlighting the strong potential of this membrane system for hydrogen purification and advanced gas separation applications.