Silicon carbide monolayer with alkali and alkaline earth metal adatoms for H₂ storage: A computational study

Given their great surface-to-volume ratio, bidimensional monolayers are ideal for hydrogen storage in fuel cell systems. It has been demonstrated that the silicon carbide (SiC) monolayer has a sp² hybridization which makes it an alternative to graphene. In this work, the hydrogen adsorption properties of a silicon carbide monolayer decorated with alkali and alkaline earth metal atoms are analysed by means of first-principles calculations. The results suggest that the adatoms cause little distortion to the monolayer, and they tend to be adsorbed on sites above Si atoms. The adatoms act as adsorption sites for H₂ molecules: up to seven molecules can be adsorbed by K, Mg and Ca. The adsorption energies suggest that H₂ molecules are physisorbed over the decorated SiC monolayer, which means that no chemical bonds are created between H₂ and the adatoms. This is beneficial because the breaking of chemical bonds, which would be needed to make use of the stored H₂, is energetically expensive. These results add to a continuing effort to develop efficient means of reversible hydrogen storage.