Eur. Phys. J. B (2018) 91: 73
https://doi.org/10.1140/epjb/e2018-80520-4

Regular Article

Insight into destabilization mechanism of Mg-based hydrides interstitially co-doped with nonmetals: a DFT study

¹ School of Chemical Engineering and Technology, Xi’an Jiaotong University, Xi’an 710049, P.R. China
² State Key Laboratory of Multiphase Flow in Power Engineering, Xi’an Jiaotong University, Xi’an 710049, P.R. China
³ HySA Systems Competence Centre, South African Institute for Advanced Materials Chemistry (SAIAMC), University of the Western Cape, Cape Town, South Africa

^a e-mail: wuz2015@mail.xjtu.edu.cn

Received: 11 September 2017
Received in final form: 5 February 2018
Published online: 2 May 2018

Abstract

Mg-based metal hydride is one of the most promising materials for hydrogen energy storage. However, the high thermal stability due to strong bonding effects between the atoms limits its practical application. In order to reduce the thermal stability, a method of doping double nonmetals into Mg-based system was proposed in this study. The density functional theory (DFT) calculation results showed that the thermal stabilities of both the B-N co-doped Mg-based alloy and its hydride are reduced compared with pure Mg-based system. The relative formation enthalpies of the alloy and its hydride are 0.323 and 0.595 eV atom⁻¹, respectively. The values are much higher than those for either singly B- or N-doped Mg-based system. The more significant destabilization by doping double nonmetal elements than single element is mainly attributed to a dual effect in weakening Mg–Ni/NiH₄ bonds, caused by criss-cross interactions between B–Ni and N–Mg bonds.