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

To modify the thermodynamics and kinetic performance of magnesium hydride (MgH 2 ) for solid-state hydrogen storage, Ni 3 V 2 O 8 -rGO (rGO represents reduced graphene oxide) and Ni 3 V 2 O 8 nanocomposites were prepared by hydrothermal and subsequent heat treatment. The beginning hydrogen desorption temperature of 7 wt.% Ni 3 V 2 O 8 -rGO modified MgH 2 was reduced to 208 °C, while the additive-free MgH 2 and 7 wt.% Ni 3 V 2 O 8 doped MgH 2 appeared to discharge hydrogen at 340 and 226 °C, respectively. A charging capacity of about 4.7 wt.% H 2 for MgH 2 + 7 wt.% Ni 3 V 2 O 8 -rGO was achieved at 125 °C in 10 min, while the dehydrogenated MgH 2 took 60 min to absorb only 4.6 wt.% H 2 at 215 °C. The microstructure analysis confirmed that the in-situ generated Mg 2 Ni/Mg 2 NiH 4 and metallic V contributed significantly to the enhanced performance of MgH 2 . In addition, the presence of rGO in the MgH 2 + 7 wt.% Ni 3 V 2 O 8 -rGO composite reduced particle aggregation tendency of Mg/MgH 2 , leading to improving the cyclic stability of MgH 2 during 20 cycles.