Microstructure and improved hydrogen storage properties of Mg85Zn5Ni10 alloy catalyzed by Cr2O3 nanoparticles

Abstract

The influences of catalyst Cr2O3 on the microstructure and hydrogen storage performances of Mg85Zn5Ni10 have been studied. The Mg85Zn5Ni10 - x wt.% Cr2O3 (x = 0, 4, 8) alloys prepared via ball milling consist of the major phase Mg, the secondary phase Mg2Ni, a little MgZn2 and Cr2O3. X-ray diffraction and high resolution transmission electron microscope results show that MgZn2 and Cr2O3 do not react with hydrogen. The Cr2O3 nanoparticles are conducive to the formation of phase interfaces, hydrogen diffusion channels, grain boundaries and nucleation sites. The hydrogen storage kinetics of Mg85Zn5Ni10 alloy has been improved by reducing the total potential barrier caused by the microstructures after ball milling with Cr2O3. The dehydrogenation activation energy has been reduced to 82.867 ± 0.21 kJ/mol from 109.83 ± 0.55 kJ/mol by adding 8 wt% Cr2O3. The dehydrogenation enthalpy values (ΔH) and entropy values (ΔS) show a downward trend with the increase of Cr2O3 contents. The catalyst Cr2O3 enhances the hydrogen storage kinetics significantly.