▎ 摘　　要

This study highlights the separation of hydrogen from H-2-He mixture gas by a graphene-coated halloysite nanoclay membrane. The graphene-coated clay membrane along with its pure day counterpart is successfully developed and studied for gas separation using hydrogen (H-2)-helium (He) single and mixture gases. Hydrothermal and nonhydrothermal methods were applied for the synthesis of a "coated" membrane on a porous alumina substrate from the graphene and halloysite clay. To date, nanoporous zeolites are the potential materials for gas separation based on a molecular sieving mechanism. A similar separation mechanism for hydrogen and helium from mixture gases may not work efficaciously due to the closeness of their kinetic diameter (H-2: 2.89 angstrom and He: 2.6 angstrom). The presence of defects and torn nanopores between graphene layers along with the different surface charges of the inner and outer layer of halloysite nanotubes facilitates the "coated" membrane to show an appreciable H-2/He separation factor of similar to 4 using H-2-He (1:1) mixture gas compared to 2.86 for the pure halloysite membrane. The available charge layer of graphene also has a significant contribution for this increased H-2/He selectivity value. The permeate flux of H-2 and He through both the graphene-coated clay membrane and pure clay membrane has also been noted. The permeate flux of pure H-2 and He was 2 x 10(-7) and 1.3 x 10(-7) mol m(-2) s(-1) Pa-1 for the clay membrane, whereas for the "coated" clay membrane, the values changed to 0.1 x 10(-7) and similar to 0.05 x 10(-7) mol m(-2) s(-1) Pa-1 at 100 kPa, respectively.