Nowadays, catalytic doping has been regarded as one of the most promising and effective methods to improve the sluggish kinetics of magnesium hydride (MgH2). Herein, we synthesized Ni/TiO2 nanocomposite with the particle sizes about 20 nm by an extremely facile solvothermal method. Then, the Ni/TiO2 nanocomposite was doped into MgH2 to enhance its reversible hydrogen storage properties. A remarkably enhancement of de/rehydrogenation kinetics of MgH2 can be achieved by doped with Ni/TiO2 nanocomposite, compared to that solely doped with Ni or TiO2 nanoparticles. The hydrogen desorption peak temperature of MgH2-Ni/TiO2 is 232 degrees C, which is 135.4 degrees C lower than that of ball-milled MgH2 (367.4 degrees C). Moreover, the MgH2-Ni/TiO2 can desorb 6.5 wt% H-2 within 7 min at 265 degrees C and absorb similar to 5 wt% H-2 within 10 min at 100 degrees C. In particular, the apparent activation energy of MgH2-Ni/TiO2 is obviously decreased from 160.5 kJ/mol (ball-milled MgH2) to 43.7 +/- 1.5 kJ/mol. Based on the analyses of microstructure evolution, it is proved that metallic Ni particles can react with Mg easily to form fine Mg2Ni particles after dehydrogenation, and the in-situ formed Mg2Ni will transform into Mg2NiH4 in the subsequent rehydrogenation process. The significantly improved hydrogen absorption/desorption properties of MgH2-Ni/TiO2 can be ascribed to the synergistic catalytic effect of reversible transformation of Mg2Ni/Mg2NiH4 which act as "hydrogen pump", and the multiple valence titanium compounds (Ti4+/3+/2+) which promote the electrons transfer of MgH2/Mg. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.