- Abstract The kinetics of hydrogen storage in magnesium can be accelerated by nanocarbon additives. In this study, we show that loading magnesium by graphene nanoplatelets (GNP) enhances the kinetics by more than an order of magnitude. The GNP presence reduces the Mg agglomeration, induced by de/hydriding, and accelerates the kinetics by connecting between Mg particles. The GNP were prepared by top-down graphite ball-milling in the presence of various organic protective agents. We found that both the molecular structure of the protective agent and the milling energy dictated the GNP properties, namely, size, thickness, defect density and specific surface area. We demonstrated how manipulation of the GNP size has a major effect on the hydrogen storage kinetics in magnesium-GNP composites.