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Abstract Nowadays, catalytic doping has been regarded as one of the most promising and effective methods to improve the sluggish kinetics of magnesium hydride (MgH 2). Herein, we synthesized Ni/TiO 2 nanocomposite with the particle sizes about 20 nm by an extremely facile solvothermal method. Then, the Ni/TiO 2 nanocomposite was doped into MgH 2 to enhance its reversible hydrogen storage properties. A remarkably enhancement of de/rehydrogenation kinetics of MgH 2 can be achieved by doped with Ni/TiO 2 nanocomposite, compared to that solely doped with Ni or TiO 2 nanoparticles. The hydrogen desorption peak temperature of MgH 2 Ni/TiO 2 is 232 °C, which is 135.4 °C lower than that of ball-milled MgH 2 (367.4 °C). Moreover, the MgH 2 Ni/TiO 2 can desorb 6.5 wt% H 2 within 7 min at 265 °C and absorb ∼5 wt% H 2 within 10 min at 100 °C. In particular, the apparent activation energy of MgH 2 Ni/TiO 2 is obviously decreased from 160.5 kJ/mol (ball-milled MgH 2) 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 Mg 2 Ni particles after dehydrogenation, and the in-situ formed Mg 2 Ni will transform into Mg 2 NiH 4 in the subsequent rehydrogenation process. The significantly improved hydrogen absorption/desorption properties of MgH 2 Ni/TiO 2 can be ascribed to the synergistic catalytic effect of reversible transformation of Mg 2 Ni/Mg 2 NiH 4 which act as "hydrogen pump", and the multiple valence titanium compounds (Ti4+/3+/2+) which promote the electrons transfer of MgH 2 /Mg. Highlights • Ni/TiO 2 with particle sizes ∼20 nm was synthesized and doped into MgH 2. • MgH 2 Ni/TiO 2 starts to release hydrogen at 190 °C with ∼6.5 wt% H 2. • Enhanced hydrogen storage properties are due to synergistic catalytic mechanism. [ABSTRACT FROM AUTHOR]

NbF 5 and eutectic 0.68LiBH 4 –0.32Ca(BH 4 ) 2 were successively infiltrated into highly ordered mesoporous carbon (CMK-3) to obtain a LiBH 4 –Ca(BH 4 ) 2 –NbF 5 @CMK-3 composite. A synergetic effect of nanoconfinement and catalysis on hydrogen desorption properties of the composite was achieved. The onset desorption temperature of LiBH 4 –Ca(BH 4 ) 2 –NbF 5 @CMK-3 is dramatically lower than 120 °C compared with that of as-milled LiBH 4 –Ca(BH 4 ) 2 or LiBH 4 –Ca(BH 4 ) 2 @CMK-3. A hydrogen amount as high as 13.3 wt% can be released within 250 min for LiBH 4 –Ca(BH 4 ) 2 –NbF 5 @CMK-3, compared with only 10.4 wt% for pure LiBH 4 –Ca(BH 4 ) 2 , in which nanoconfinement and catalysis both make some contribution. The cycling hydrogen desorption performance of the composite becomes better likewise due to the addition of NbF 5 . Further microstructure analysis reveals that F − tended to bind with Ca 2+ to form CaF 2 , whereas Nb compound is believed to catalyze the whole system in the form of Nb-based boride (NbB 2 ). [ABSTRACT FROM AUTHOR]