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

Abstract

The effect of Zr substitution by alkaline earth metals Mg, Be and post-transition metal Al on the evolution of hydrogen storage properties of ZrNiH3 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 ZrNiH3. 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.H2) 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 ZrNiH3.Moreover, the electronic structure investigated by partial density of states (PDOS), reveals the metallic nature of Zr1−xAMxNiH3 (AM = Mg, Be and Al) hydrides. Highlights The ZrNiH3 hydride presents high stability and high decomposition temperature. The stability decreases significantly when doping ZrNiH3 with Mg, Be and Al. The density of states reveals the metallic nature of Zr1−xAMxNiH3 hydrides.