Influence of CeO2 nanoparticles on microstructure and hydrogen storage performance of Mg-Ni-Zn alloy

Abstract

The Mg85Ni10Zn5 + x wt% CeO2 (x = 0, 2, 4, 8) composites were synthesized by high energy ball milling. The phase structures of as-milled composites were characterized, and the results showed that the hydrogen storage reaction mechanism can be concluded as: Mg + H2 ↔ MgH2, Mg2Ni + H2 ↔ Mg2NiH4, and MgZn2 phase and the catalyst CeO2 nanoparticles do not react during the hydrogenation/dehydrogenation process. The composites can absorb/desorb ~5.28 wt% hydrogen reversibly in about 10 min above 320 °C. Moreover, the hydriding/dehydriding reaction rate of CeO2 catalyzed composites is much faster than un-catalyzed one. The activation energy of dehydrogenation was decreased from 109.83 to 82.93 kJ/mol H2 by adding 4 wt% CeO2. It indicates that the hydrogen storage kinetics of the composites was expedited by the adding of catalyst CeO2 nanoparticles, which is attributing to more phase interfaces and grain boundaries were provided by milling Mg85Ni10Zn5 with CeO2 nanoparticles and it means more hydrogen atom diffusion channels and reaction nucleation positions were offered for hydrogenation/dehydrogenation reaction. However, the hydrogen storage thermodynamic properties of Mg85Ni10Zn5 alloy have enhanced slightly by milling Mg85Ni10Zn5 with CeO2 nanoparticles.