Graphene-loaded nickel−vanadium bimetal oxides as hydrogen pumps to boost solid-state hydrogen storage kinetic performance of magnesium hydride

Abstract

To modify the thermodynamics and kinetic performance of magnesium hydride (MgH₂) for solid-state hydrogen storage, Ni₃V₂O₈-rGO (rGO represents reduced graphene oxide) and Ni₃V₂O₈ nanocomposites were prepared by hydrothermal and subsequent heat treatment. The beginning hydrogen desorption temperature of 7 wt.% Ni₃V₂O₈-rGO modified MgH₂ was reduced to 208 °C, while the additive-free MgH₂ and 7 wt.% Ni₃V₂O₈ doped MgH₂ appeared to discharge hydrogen at 340 and 226 °C, respectively. A charging capacity of about 4.7 wt.% H₂ for MgH₂ + 7 wt.% Ni₃V₂O₈-rGO was achieved at 125 °C in 10 min, while the dehydrogenated MgH₂ took 60 min to absorb only 4.6 wt.% H₂ at 215 °C. The microstructure analysis confirmed that the in-situ generated Mg₂Ni/Mg₂NiH₄ and metallic V contributed significantly to the enhanced performance of MgH₂. In addition, the presence of rGO in the MgH₂ + 7 wt.% Ni₃V₂O₈-rGO composite reduced particle aggregation tendency of Mg/MgH₂, leading to improving the cyclic stability of MgH₂ during 20 cycles.