Light metal decorated graphene-like Si2BN monolayers as hydrogen storage media: A DFT investigation

Abstract

The hydrogen storage properties of an alkali metal (Li, Na, K) or alkaline earth metal (Be, Mg, Ca) decorated Si2BN monolayer were studied based on first-principles calculations. The study indicated that these metal atoms can be stably bonded on both sides of the Si2BN monolayer, but without promoting agglomeration. Compared with the original structure, the metal-decorated Si2BN monolayer exhibited significantly enhanced physical adsorption for H2 molecules. Furthermore, the Li, Na, Be and Ca-decorated Si2BN monolayers exhibited a high gravimetric density ranging from 7.1 to 11.7 wt% and a suitable adsorption energy range from −0.11 to −0.27 eV. In contrast, the K and Mg-decorated Si2BN monolayers were not suitable for practical applications due to their low adsorption energy (−0.07 eV) and poor gravimetric density (4.6 wt%). In particular, the Li-decorated Si2BN monolayer showed the highest hydrogen storage gravimetric density (11.7 wt%), whilst the Be-decorated Si2BN monolayer showed the closest desorption temperature (319 K) to room temperature. These findings provide theoretical insights into the excellent hydrogen storage properties of this novel graphene-like monolayer material after metal decoration.