First principles study to identify the reversible reaction step of a multinary hydrogen storage “Li–Mg–B–N–H” system

A density functional theory study with the generalized gradient approximation (GGA) and projected augmented wave (PAW) method is performed for the hydrogen storage properties of the complex multinary storage Li–Mg–B–N–H system. Using ab initio methods, stability of the structures at finite temperatures is confirmed via. phonon spectrum calculations. Thermodynamic properties such as heat of reaction, and Gibbs energy for each reactant and product in the reaction steps in different temperature zones are calculated. It is found that reversibility occurs in the temperature range of 160–225 °C with approximately 4.38 wt % hydrogen storage capacity. The enthalpy of reversible re-/de-hydrogenation is found to be 55.17 kJ/mol H2, which is supported by experimental data. The total hydrogen storage capacity of this material is calculated to be 8.76 wt% from the desorption behavior observed at different temperatures up to 350 °C. These theoretically established reactions are validated with the suggested mechanism from experimental observations for the dehydrogenation reaction of this Li–Mg–B–N–H multinary system. These efforts are expected to contribute toward identification of suitable hydrogen storage materials.