Enhanced hydrogen sorption properties of MgH2 when doped with mechanically alloyed amorphous Zr0·67Ni0.33 particles

Abstract

In the present study, the effect of amorphous Zr0·67Ni0.33 additive containing nano-ZrO2 on the hydrogen sorption kinetics and thermodynamics of Mg/MgH2 was investigated. The amorphous Zr0·67Ni0.33 particles prepared by mechanical alloying of stoichiometric elements were introduced into MgH2 powder through high-energy milling to produce a MgH2/Zr0·67Ni0.33 composite. Structural and morphological analyses revealed that the nanostructuring effect of the ZrO2 containing amorphous Zr0·67Ni0.33 has led to significant grain-size refinement of MgH2 to the nanometric scale. As a result, the MgH2/Zr0·67Ni0.33 composite demonstrates enhanced hydrogenation and dehydrogenation kinetics (4.0 wt%/50 s/250 °C and 5.0 wt%/4 min/325 °C, respectively). Meantime, substantially lowered enthalpies (−63.40 and 67.06 kJ/mol H2 obtained through pressure-composition-isotherm measurements) and reduced desorption temperature (~270 °C) were observed in the composite as compared to the pure MgH2, possibly due to the dissolution of Ni into MgH2 lattice during ball milling.