▎ 摘　　要

Several different hydrogen storage systems including MgH2, MgH2-Graphene, MgH2-Ni and MgH2-Graphene-Ni were synthesized by a high energy ball milling technique. The phase compositions, microstructures and dehydrogenation properties of different systems were characterized by the testing methods such as X-ray diffraction, scanning electron microscope and differential scanning calorimeter. The effect of separate doping and co-doping of Graphene and Ni on dehydrogenation properties of MgH2 and the mechanism were also studied. Results show that the initial dehydrogenation temperature of Graphene-doped MgH2 decreases by, about 33 degrees C; it is attributed to the effect of grain refinement and uniform size of MgH2 particles caused by the structure confinement effect by Graphene in the ball-milling process. For the MgH2-Ni system, the initial dehydrogenation temperature of MgH2 significantly decreases by almost 136 degrees C due to the lattice deformation and the reduction of structural stability of MgH2 matrix where some Mg atoms are replaced by Ni atoms. However, the doping order plays an important role in the Graphene and Ni co-doped MgH2 system. When Graphene and Ni are doped in the MgH2 system at the same time, the initial dehydrogenation temperature of MgH2 system does not drop because the buffer function of MgH2 particle coated by Graphene makes it difficult for the Ni atoms to solid-solution into the MgH2 matrix. While when Graphene is doped in the MgH2 system after Ni atom, the initial dehydrogenation temperature further decreases by nearly 175 degrees C with respect to pure MgH2 system owing to both the effect of the realization of solid solution by Ni atom and the structure confinement effect by Graphene.