Effect of protective layer from in-situ heteroatom incorporation on the hydriding reaction of Mg(0001): A density functional theory study

To understand the effect of the protective layer on Mg hydriding, four nonmetallic heteroatoms (C, O, N and S) were introduced into the Mg(0001), and their effects on H2 adsorption, dissociation, and subsequent H atom diffusion were explored through density functional theory (DFT) calculations. After being adsorbed by Mg (0001), the CO2, NO2, and SO2 molecules can dissociate into C, O, N, and S heteroatoms, which then combine in situ with Mg(0001) to form a protective layer. The incorporated heteroatoms can improve the localized electronic structure of Mg(0001), thereby facilitating H2 adsorption and dissociation. Although the incorporated heteroatoms limit the surface diffusion of H atoms, they facilitate the penetration of these atoms through the first Mg layer and enhance bulk diffusion, thereby favoring the hydriding reaction of Mg. This work clarifies the effect of protective layer from in-situ heteroatom incorporation on Mg hydriding, benefiting for the design of highperformance and safe Mg-based hydrogen storage materials.