Graphene Nanosheet‐Based Mixed Proton‐Electron Conducting Membranes for Efficient Hydrogen Purification

ABSTRACT Efficient separation of hydrogen from carbon dioxide is essential in conventional hydrogen production processes such as steam methane reforming. Here, we report a graphene/phosphoric acid (GP) mixed proton‐electron conducting (MPEC) membrane that enables highly selective hydrogen purification at elevated temperatures. The GP membrane, constructed from monolayer polyethyleneimine‐functionalized graphene nanosheets and nanoconfined phosphoric acid, integrates rapid proton conduction through hydrogen‐bonded acid networks with fast electron transport along the interconnected graphene framework. When configured as a catalyst‐coated membrane reactor, the GP membrane achieves nearly 100% H 2 /CO 2 selectivity and a hydrogen permeance of 69 GPU at 250°C. This outstanding performance arises from the synergistic coupling of proton and electron conduction and the excellent thermal stability of the 2D composite membrane. The findings highlight a promising strategy for designing 2D material‐based MPEC membranes for high‐temperature hydrogen purification and ultra‐pure hydrogen production in next‐generation clean‐energy systems.