Enhanced hydrogen sorption kinetics of co-doped MgH2 hydrides

Abstract

Double substituted MgH2 sorption kinetic is studied by combining density functional theory (DFT) and Kinetic Monte Carlo (KMC) simulations. The DFT calculations were performed to compute the energy barriers of the relevant elementary processes, which will be used as a database for the KMC simulations. The study provides a discussion of the mechanism behind the hydrogen reaction path on magnesium hydride (adsorption, dissociation, surface migration, penetration, and diffusion) as we took into account the density distribution of hydrogen atoms as well as the filling ratios, the diffusion time and finally the temperature. Based on the obtained results, the double substitution not only improves MgH2 stability and desorption temperature but also its adsorption and desorption kinetics. Among the studied systems Mg14ZnLiH32 exhibits the best results with the fastest ab/desorption kinetic, in addition to its ideal heat of formation ΔH=-38.27 kJ/mol and high gravimetric capacity 7.25 wt%.