Graphene-anchored Ni6MnO8 nanoparticles with steady catalytic action to accelerate the hydrogen storage kinetics of MgH2

Abstract

Transition metal-based oxides have been proven to have a substantial catalytic influence on boosting the hydrogen sorption performance of MgH2. Herein, the catalytic action of Ni6MnO8@rGO nanocomposite in accelerating the hydrogen sorption properties of MgH2 was investigated. The MgH2 + 5 wt% Ni6MnO8@rGO composites began delivering H2 at 218 °C, with about 2.7 wt%, 5.4 wt%, and 6.6 wt% H2 released within 10 min at 265 °C, 275 °C, and 300 °C, respectively. For isothermal hydrogenation at 75 °C and 100 °C, the dehydrogenated MgH2 + 5 wt% Ni6MnO8@rGO sample could absorb 1.0 wt% and 3.3 wt% H2 in 30 min, respectively. Moreover, as compared to addition-free MgH2, the de/rehydrogenation activation energies for doped MgH2 composites were lowered to 115 ± 11 kJ/mol and 38 ± 7 kJ/mol, and remarkable cyclic stability was reported after 20 cycles. Microstructure analysis revealed that the in-situ formed Mg2Ni/Mg2NiH4, Mn, MnO2, and reduced graphene oxide synergically enhanced the hydrogen de/absorption properties of the Mg/MgH2 system.