Improved dehydriding property of polyvinylpyrrolidone coated Mg-Ni hydrogen storage nano-composite prepared by hydriding combustion synthesis and wet mechanical milling

In this work, polyvinylpyrrolidone (PVP) coated Mg₉₅Ni₅ nano-composites were prepared by hydriding combustion synthesis (HCS) plus wet mechanical milling (WM) with tetrahydrofuran (THF) and donated as WM-x wt% PVP (x = 1, 3, 5 and 7) respectively. The phase compositions, microstructures and dehydriding property, as well as the co-effect of PVP and THF were investigated in detail. XRD results showed that the average crystal size of MgH₂ in the milled Mg₉₅Ni₅ decreased from 23 nm without PVP to 18 nm with 1 wt% PVP. The peak temperature of dehydrogenation of MgH₂ in the milled Mg₉₅Ni₅ decreased from 293.0 °C without THF to 250.4 °C with THF. The apparent activation energy for decomposition of MgH₂ in WM-7 wt% PVP was estimated to be 66.94 kJ/mol, which is 37.70 kJ/mol lower than that of milled Mg₉₅Ni₅ without THF and PVP. PVP and THF can facilitate the refinement of particle size during mechanical milling process. Attributed to small particle sizes and synergistic effect of PVP and THF, the composites exhibit markedly improved dehydriding properties.