Graphene has been shown to act as an efficient sieve for hydrogen isotope separation since the perfect monolayer graphene is impermeable to almost all atoms and molecules but permeable to protons. Large-area graphene films can be produced by chemical vapor deposition (CVD) and exhibit a considerably high proton−deuteron separation factor of ∼8. However, the performance of the graphene-based membrane is often limited by the presence of cracks and imperfections introduced mainly during the transfer process. Here, we report a simple but effective method to transfer large-area CVD graphene onto commercial Nafion membranes with the aid of palladium thin films and thus fabricate the Pd/Graphene/Nafion composite membranes, which allow a proton−deuteron separation factor up to ∼10. This transfer method avoids the mechanical damage of graphene caused by deformation of the Nafion membrane. There is no need to remove the palladium thin film, and it will act as a catalyst for the reduction of hydrons during electrochemical pumping. The large-area transfer of graphene and fabrication of composite membranes for efficient separation of hydrogen isotopes will promote the development of graphene-based separation technologies.

Hydrogen isotope separation has been effectively achieved electrochemically by passage of gaseous H 2 /D 2 through graphene/Nafion composite membranes. Nevertheless, deuteron nearly does not exist in the form of gaseous D 2 in nature but as liquid water. Thus, it is a more feasible way to separate and enrich deuterium from water. Herein, we have successfully transferred monolayer graphene to a rigid and porous polymer substrate, PITEM (polyimide track-etched membrane), which could avoid the swelling problem of the Nafion substrate as well as keep the integrity of graphene. Meanwhile, defects in the large area of CVD graphene could be successfully repaired by interfacial polymerization resulting in a high separation factor. Moreover, a new model was proposed for the proton transport mechanism through monolayer graphene based on the kinetic isotope effect (KIE). In this model, graphene plays a significant role in the H/D separation process by completely breaking the O−H/O−D bond, which can maximize the KIE, leading to increased H/D separation performance. This work suggests a promising application for using monolayer graphene in the industry and proposes a pronounced understanding of proton transport in graphene.

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