Controllable synthesis of 2D TiH2 nanoflakes with superior catalytic activity for low-temperature hydrogen cycling of NaAlH4

Nanosized titanium compounds are particularly effective in catalyzing hydrogen cycling by NaAlH 4 . Titanium hydride (TiH 2 ), as a catalyst, is highly interesting since it contributes hydrogen in addition to active Ti. However, it has been challenging to fabricate nanosized TiH 2 due to the strong affinity of Ti with oxygen. Herein, TiH 2 nanoflakes with a lateral size of ~10 nm and thickness of ~1 nm are successfully synthesized through a novel facile one-pot solvothermal process. In an anhydrous THF solution, LiH reacts with TiCl 4 rapidly at 100 °C forming TiH 2 and LiCl. The newly formed TiH 2 nucleates and grows epitaxially on the graphene surface due to the well-matched lattice parameters, giving rise to the formation of TiH 2 nanoflakes. Both theoretical calculations and experiments reveal the generation of Cl· radicals and unsaturated C C bonds when TiCl 4 reacts with THF, which promotes the formation of TiH 2 . The nanoflake-like TiH 2 on graphene enables an outstanding hydrogen storage performance of NaAlH 4 , i.e., full dehydrogenation at 80 °C and hydrogenation at 30 °C and under 100 bar H 2 , with a practical hydrogen capacity of 4.9 wt%, which has been never reported before.