Effects of double substitution on MgH2 hydrogen storage properties: An Ab initio study

Abstract

Using Ab-initio calculations, we investigate the destabilizing effects of co-doped MgH2 with Li and TM (Sc, Ti, V, Cr, Y, Zr, Nb, Mo). The calculations are performed using the all-electron full-potential local-orbital minimum-basis scheme (FPLO9.00-34). Our findings indicate that the doping of Li beside TM played an important role in improving the thermodynamic properties of MgH2. Through this double substitution, a reduction of heat of formation/desorption and preservation of the optimum gravimetric capacity are obtained. Precisely, we find that the co-doping with VLi; ZrLi; TiLi; YLi, have desorption temperatures within the optimum range 289 K–393 K, for the practical applications. More precisely, the VLi co-doping exposes a heat of formation −39.21kj/mol which is the closest to the ideal heat of formation −40kj/mol. Besides, our results suggested that, the combination of Li with V into MgH2 is greatly favourable compared to V doping alone. To understand the processes for absorption/desorption of MgH2, detailed discussion of the electronegativity, the charge exchange and the density of states is carried out.