▎ 摘　　要

NOVELTY - Preparing educed graphene oxide-magnesium nanocrystal composite involves contacting graphene oxide with a first reducing agent and co-reducing the graphene oxide and a precursor of magnesium in the presence of a second reducing agent. The size of the magnesium nanocrystals in the composite is controlled by adjusting the amount of the first agent in contact with graphene oxide. A weight ratio of graphene oxide to first agent is 1:1-1:20. The precursor of magnesia is bis(cyclopentadienyl) magnesium, magnesium chloride, and/or di-n-butyl magnesium. USE - The method for preparing a reduced graphene oxide-magnesium nanocrystal composite used as a hydrogen storage material. ADVANTAGE - The method enables to prepare reduced graphene oxide-magnesium nanocrystal composite that has high power density and short charging/discharging time, which can be applied for commercial vehicles such as trucks and buses. The size of the magnesium nanocrystals in the composite may be readily controlled by adjusting the amount of the reducing agent through the method for preparing the composite, and thus hydrogen storage capacity and kinetics of the composites may be easily controlled. DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of controlling the size of magnesium in a reduced graphene oxide-magnesium nanocrystal composite.