Ab initio study of the effects of transition metal doping of Mg2NiH4

Michiel J. van Setten, Gilles A. de Wijs, G. Brocks

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Abstract

Mg2NiH4 is a promising hydrogen storage material with fast (de)hydrogenation kinetics. Its hydrogen desorption enthalpy, however, is too large for practical applications. In this paper we study the effects of transition metal doping by first-principles density functional theory calculations. We show that the hydrogen desorption enthalpy can be reduced by ~0.1 eV/H2 if one in eight Ni atoms is replaced by Cu or Fe. Replacing Ni by Co atoms, however, increases the hydrogen desorption enthalpy. We study the thermodynamic stability of the dopants in the hydrogenated and dehydrogenated phases. Doping with Co or Cu leads to marginally stable compounds, whereas doping with Fe leads to an unstable compound. The optical response of Mg2NiH4 is also substantially affected by doping. The direct gap in Mg2NiH4 is ~1.7 eV. Doping with Co, Fe, or Cu leads to impurity bands that reduce the direct gap by up to 0.5 eV.
Original languageUndefined
Pages (from-to)075125-1-075125-8
Number of pages8
JournalPhysical review B: Condensed matter and materials physics
Volume76
Issue number7
DOIs
Publication statusPublished - 2007

Keywords

  • IR-59158
  • METIS-241529

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