Hydrogen molecules permeate graphene: Permeate way and the breaking and recombination of bonds

Abstract

Monolayer non-defect graphene is generally considered to be impermeable. However, recent study has shown that a small amount of molecular hydrogen can permeate it. This process involves the breaking and recombination of bonds, which are closely related to the permeation mode of hydrogen molecules. Here we studied the penetration of hydrogen molecules into three types of graphene (non-defect, Stone-Wales defect and undergoes biaxial tensile) using density functional theory. We found the penetration mode from rings is more favorable for bond breaking although the barrier of vertical mode is lower. In addition, the reduced barrier of Stone-Wales defects is comparable to that of 12% biaxial tensile strain regardless of whether hydrogen molecules permeate in vertical or parallel manner. Our work provides a unique perspective on the breaking of chemical bonds. It also provides a theoretical basis for potential applications of graphene in gas separation and transport.