Transition metal doping of Mg2FeH6 – a DFT insight into synthesis and electronic structure

Abstract

Mg₂FeH₆ is a promising hydrogen storage material with one of the highest volumetric hydrogen density among the known hydrogen storage materials. However, its complicated synthesis and high temperature of hydrogen desorption limit wider applications. In this paper we study the influence of transition metal (Ni, Co, Mn) doping on the structural, electronic and hydrogen sorption properties of Mg₂FeH₆, using first-principles density functional theory calculations. The thermodynamics of three different synthesis routes is addressed, and all of the mentioned transition metals are found to destabilize Mg₂FeH₆. In addition, a detailed study of electronic structure properties, including densities of states (DOS) and charge transfer analysis (AIM), reveals that the doping with Ni, Mn and Co leads to the reduction of the direct band gap of Mg₂FeH₆.