Recent advances in magnesium hydride for solid-state hydrogen storage by mechanical treatment: A DFT study

Abstract

In this paper, using density functional theory (DFT), we investigate the impact of mechanical treatment in terms of uniaxial and biaxial strains on both hydrogenation states of magnesium compounds i.e. H2-free magnesium (Mg) and preliminarily hydrogenated magnesium (MgH2). The thermodynamic properties calculation shows that applying uniaxial and biaxial strains on the H2-free magnesium does not significantly affect the formation enthalpy and decomposition temperature of the hydride phase. On the other hand, strain energy contributions on preliminarily hydrogenated magnesium are found able to decrease and improve the formation enthalpy and the decomposition temperature, making it feasible for the operational conditions of proton exchange membrane (PEM) fuel cells at 289 – 393 K. Also, the findings demonstrate that the kinetic properties in terms of hydrogen atom diffusion show a decrease in the activation energy barrier, which means an improvement in the kinetics properties faster than that of strain-free magnesium hydride. These results potentially provide better clues for the development of a magnesium-based metal hydride for hydrogen storage applications.