Dependence of Mg, Be and Al substitution on the hydrogen storage characteristics of ZrNiH 3

The effect of Zr substitution by alkaline earth metals Mg, Be and post-transition metal Al on the evolution of hydrogen storage properties of ZrNiH 3 has been investigated by ab-initio calculations based on density functional theory. The stability of the quaternary hydrides is studied by the determination of the formation enthalpy and the desorption temperature. The obtained results indicate a reduction of the formation enthalpy as well as the desorption temperature , hence reflecting the enhancement of hydrogen storage properties of ZrNiH 3. Interestingly, each dopant (Mg, Be and Al) achieved its optimum substitution effect at a particular concentration, with Al and Be elements are found to exhibit the lowest substituting content 17% and 23% respectively and Mg with the highest concentration 85%, to achieve an ideal formation enthalpy (ΔH = −40 kJ/mol.H 2) and desorption temperatures (289 to 393 K), as required for practical use of proton exchange membrane fuel cells (PEMFC) without affecting the hydrogen storage capacity as seen in pure ZrNiH 3 .More-over, the electronic structure investigated by partial density of states (PDOS), reveals the metallic nature of Zr 1−x AM x NiH 3 (AM = Mg, Be and Al) hydrides. Highlights • The ZrNiH 3 hydride presents high stability and high decomposition temperature. • The stability decreases significantly when doping ZrNiH 3 with Mg, Be and Al. • The density of states reveals the metallic nature of Zr 1−x AM x NiH 3 hydrides. K E Y W O R D S density functional theory, hydrogen storage, Ni-MH batteries, thermodynamic properties, ZrNiH 3