Hydrogen storage capacities of alkali and alkaline-earth metal atoms on SiC monolayer: A first-principles study

A detailed theoretical Density-Functional-Theory-based investigation of hydrogen adsorption on silicon carbide monolayers (SiC-ML) decorated with alkali and alkaline-earth metal atoms is presented. The results show that the favourable position for all adsorbed metal atoms is above a Si atom. These metal atoms are chemisorbed to the SiC-ML, except for Mg which is physisorbed. The adsorbed atoms act in turn as adsorption sites for H₂ molecules. The single-sided K-functionalized SiC-ML can store up to six H₂ molecules. For double-side K-decorated SiC-ML, up to ten H₂ molecules can be captured. In all cases, the H₂ molecules are physisorbed. This is beneficial because the breaking of chemical bonds, which otherwise would be needed to make use of the stored H₂, is energetically expensive. These results find decorated SiC-ML as a promising material for hydrogen storage systems.