Role of electron localisation in H adsorption and hydride formation in the Mg basal plane under aqueous corrosion: a first-principles study

Understanding hydrogen-metal interactions is important in various fields of surface science, including the aqueous corrosion of metals. The interaction between atomic H and a Mg surface is a key process for the formation of sub-surface Mg hydride, which may play an important role in Mg aqueous corrosion. In the present work, we performed first-principles Density Functional Theory (DFT) calculations to study the mechanisms for hydrogen adsorption and crystalline Mg hydride formation under aqueous conditions. The Electron Localisation Function (ELF) is found to be a promising indicator for predicting stable H adsorption in the Mg surface. It is found that H adsorption and hydride layer formation is dominated by high ELF adsorption sites. Our calculations suggest that the on-surface adsorption of atomic H, OH radicals and atomic O could enhance the electron localisation at specific sites in the sub-surface region, thus forming effective H traps locally. This is predicted to result in the formation of a thermodynamically stable sub-surface hydride layer, which is a potential precursor of the crucial hydride corrosion product of magnesium.

Automated summary

Understanding the interaction between hydrogen and metals is crucial for surface science, particularly in studying the corrosion of metals in aqueous environments. This study used first-principles Density Functional Theory (DFT) calculations to investigate the mechanisms of hydrogen adsorption and crystalline magnesium hydride formation under aqueous conditions. The Electron Localisation Function (ELF) was identified as a useful indicator for predicting stable hydrogen adsorption on magnesium surfaces. The research suggests that the adsorption of atomic hydrogen, hydroxyl radicals, and atomic oxygen on the surface can enhance electron localisation in specific sub-surface regions, leading to the formation of thermodynamically stable sub-surface hydride layers.