Hydrogen diffusion in MgH2 doped with Ti, Mn and Fe

Abstract

Incorporation of suitable dopants in MgH₂ is widely investigated as the way of improving hydrogen storage characteristics of this material. The catalytic role of transition metal dopants on hydrogen desorption from MgH₂ is very promising, but further attention is required in order to optimize the experimental methods and design materials with desired properties. In this paper we investigate the role of Ti, Fe, and Mn on the transport properties of hydrogen in MgH₂, which are marked as limiting factor in the effort to lower the hydrogen desorption temperature. Taking into account the lattice relaxation around the impurities, we consider a number of different diffusion paths in the pure and doped system. Using PAW DFT calculations in combination with the NEB method, we demonstrate that the diffusion of the most relevant positively charged hydrogen vacancy and negatively charged interstitial hydrogen atom is locally hindered by the presence of the impurity atoms.