Enhanced Hydrogen Storage Properties of MgH 2 Using a Ni and TiO 2 Co-Doped Reduced Graphene Oxide Nanocomposite as a Catalyst

To improve the hydrogen storage properties of Mg/MgH , a Ni and TiO co-doped reduced graphene oxide [(Ni-TiO )@rGO] nanocomposite is synthesized by a facile impregnation method and introduced into Mg via ball milling. The results demonstrated that the dispersive distribution of Ni and TiO with a particle size of 20-200 nm in the reduced graphene oxide matrix led to superior catalytic effects on the hydrogen storage properties of Mg-(Ni-TiO )@rGO. The initial hydrogenation/dehydrogenation temperature for Mg-(Ni-TiO )@rGO decreased to 323/479 K, 75/84 K lower than that of the additive-free sample. The hydrogen desorption capacity of the Mg-(Ni-TiO )@rGO composite released 1.47 wt.% within 120 min at 498 K. When the temperature was increased to 523 K, the hydrogen desorption capacity increased to 4.30 wt.% within 30 min. A hydrogenation/dehydrogenation apparent activation energy of 47.0/99.3 kJ·mol was obtained for the Mg-(Ni-TiO )@rGO composite. The improvement in hydrogenation and dehydrogenation for the Mg-(Ni-TiO )@rGO composite was due to the reduction of the apparent activation energy by the catalytic action of (Ni-TiO )@rGO.