Synthesis of porous Ni@rGO nanocomposite and its synergetic effect on hydrogen sorption properties of MgH2

Abstract

A porous Ni@rGO nanocomposite was successfully prepared by the ethylene glycol method followed by an annealing process. It was shown that fcc Ni nanoparticles anchored on reduced graphene oxide sheets producing a porous structure. It was also found that Ni@rGO nanocomposite had a good catalytic effect on de/hydrogenation of MgH2. The MgH2–5 wt% Ni@rGO composite acquired by ball milling exhibited improved faster sorption kinetics and relatively lower sorption temperature than pure MgH2. The desorption peak temperature shifted from 356 °C for pure milled MgH2 to 247 °C for MgH2–5 wt% Ni@rGO. The MgH2–5 wt% Ni@rGO composite could desorb 6.0 wt% H2 within 10 min at 300 °C even after nine cycles, in contrast, only 2.7 wt% H2 was desorbed even after 120 min for undoped MgH2. In addition, the activation energy (Ea) decreased significantly compared to MgH2 and the presence of a few layer reduced graphene oxide sheets on the MgH2 surface prevented the nanograins sintering and agglomeration during cycling, which enhanced the MgH2 decomposition and cycling stability. It was suggested that the porous Ni@rGO composite had a synergetic effect on the MgH2 sorption properties.