Improvement of decomposition temperature and gravimetric density of MgH2 by transition metals and vacancies: A comparison study

An ab initio study is investigated to study the effects of transition metals and vacancies on the thermodynamic characteristics of magnesium hydride (MgH2) and compare the calculation results in terms of the decomposition temperature and the gravimetric density. The Green's function method is used to perform our calculations. In particular, the magnesium vacancies facilitate faster diffusion of hydrogen atoms within the MgH2 while the transition metals weaken the strong band between hydrogen and magnesium, which both improve the decomposition temperature. The creation of vacancies is more favorable than doping with transition metals in MgH2, with a concentration range of vacancies from 3.3 to 4.6% for practical use. In addition, the vacancies allow increasing the gravimetric density from 7.658 to 8.269 wt%, while using the transition metals reduces the density from 7.658 to 7.064 wt% for Mg1-xCrxH2 and 7.658 to 7.006 wt% for Mg1-xMnxH2.

Automated summary

An ab initio study examines the impact of transition metals and vacancies on the thermodynamic properties of magnesium hydride (MgH2), focusing on decomposition temperature and gravimetric density. The results show that magnesium vacancies promote hydrogen diffusion within MgH2, while transition metals weaken the hydrogen-magnesium bond, both improving the decomposition temperature. Vacancies are more favorable than transition metal doping, with a practical concentration range of 3.3% to 4.6%. Additionally, vacancies increase the gravimetric density from 7.658 to 8.269 wt%, while transition metals reduce the density to 7.064 wt% for Mg1-xCrxH2 and 7.006 wt% for Mg1-xMnxH2.