External electric field induced hydrogen storage/release on calcium-decorated single-layer and bilayer silicene

Abstract

Hydrogen storage and release are two essential parameters that define the efficiency of a hydrogen storage medium. Herein, we investigate the effects of the external electric field F on the adsorption–desorption of H₂ on a Ca-decorated silicene system (Ca–silicene) based on density functional theory calculations. Our study demonstrates that nine H₂ molecules per Ca atom can be adsorbed and 6.4 wt% H₂ can be adsorbed on Ca–silicene with an average binding energy of 0.19 eV per H₂, while the appropriate F can be used to effectively enhance the hydrogen storage–release on the Ca–silicene system. The high synergetic effect may be attributed to the observation that F induces an enhancement of the charge transfer between H₂ molecules and the Ca–silicene system. Thus, the Ca–silicene system together with the synergy of F can efficiently facilitate H₂ adsorption–desorption, completing the whole hydrogen storage–release cycle.