Direct synthesis of nanocrystalline titanium dioxide/carbon composite and its catalytic effect on NaAlH4 for hydrogen storage

Nanocrystalline titanium dioxide/carbon composite (TiO2/C) was synthesized through a direct solution-phase carburization using tetrabutyl titanate (Ti(OBu)4) and resol as precursors. The prepared TiO2/C composite was mainly in the anatase structure with an average particle size under 20 nm, which was then introduced in NaAlH4 as a catalyst through ball milling. The desorption curves show that both nanocrystalline TiO2/C and TiO2 can obviously improve the kinetics of NaAlH4, while NaAlH4 with 3 mol% TiO2/C exhibits better cycling stability than NaAlH4 with 3 mol%TiO2. The hydrogen storage capacity of NaAlH4 with TiO2/C remains stable after 5th cycle, and about 94% of initial hydrogen is released, while the capacity of NaAlH4 with TiO2 decreases continuously during cycling, and only 88% of initial hydrogen is released after 10th cycle. Furthermore, NaAlH4 with 3 mol%TiO2/C exhibits good reversibility at relatively low hydrogen pressures, and it can reload 4.16 and 1.63wt% hydrogen at 50 and 30 bar hydrogen pressures, respectively.