Improving thermodynamic properties and desorption temperature in MgH2 by doping Be: DFT study

Abstract

ABSTRACT Storage of hydrogen is a necessary prerequisite for the commercialisation of hydrogen used in the production of energy. The solid-state storage of hydrogen is one of the many different methods for storing hydrogen, requiring much research. This work aims to optimise the desorption temperature and kinetic characteristics of MgH2 by introducing Be doping at varying concentrations using density functional theory within the WIEN2k code. Gravimetric hydrogen storage capacity increases as the Be concentration increases. Formation energy, cohesive energy and desorption temperature improve with the doping of Be. Elastic constants are then used to determine which hydrides are mechanically stable. All of the hydrides, except for MgBe3H8, meet the Born stability conditions, which means that they are mechanically stable. The bonding characteristics, shear modulus, bulk modulus, Cauchy pressures and Vicker’s hardness test are all measured and analysed. These hydrides can be classified as semiconductors based on their electronic properties, and bandgap values decrease with the concentration of Be. Many previously undiscovered thermodynamic features of these hydrides are examined and presented. The Seebeck coefficient, a figure of merit, and electrical and electronic-thermal conductivities are also calculated to investigate the thermoelectric properties.