Dehydrogenation kinetics of magnesium hydride investigated by DFT and experiment

Periodic density functional theory (DFT) and nudged elastic Band (NEB) method have been used to investigate the hydrogen desorption on MgH2(0 0 1) and MgH2(1 1 0) surface as a first step towards understanding the dehydrogenation cycle. A study of reaction barriers for three and five pathways of MgH2(0 0 1) and MgH2(1 1 0) surface have been performed. The most favorable desorption channel needs activation energies of approximately 1.60 eV with H atoms binding on the same Mg atoms on the MgH2(1 1 0) surface. Meanwhile, the MgH2 sample was prepared by ball milling treatment and Chou method was used to investigate the hydrogen desorption kinetic mechanism of MgH2. The obtained activation energies are 1.58 ± 0.6 eV for H2 recombination on the pure surface. It is suggested that the rate-controlling step is recombination of H2 on the MgH2 surface.