Hydrogen Adsorption on the Vertical Heterostructures of Graphene and Two-Dimensional Electrides: A First-Principles Study

Synergetic effects in two-dimensional heterostructures have attracted considerable attention in the field of catalysis. Herein, we present a first-principles study of hydrogen adsorption on the vertical heterostructures of graphene and electride (Ca2N or Y2C) monolayers. Density functional theory calculations revealed that a substantial charge transfer from the electride layers to the graphene facilitated hydrogen adsorption onto the graphene. The graphene/Ca2N and graphene/Y2C heterostructures possess adsorption free energies of 0.73 and 0.51 eV, respectively, much lower than that of the pristine graphene (1.9 eV). Moreover, doping graphene with N can further reduce the adsorption free energy of the heterostructures down to 0.29 eV, close to the optimal zero value. These results suggest that heterostructure formation activates graphene for hydrogen-evolution reactions, providing an innovative and promising strategy for hydrogen production.