Boosting Visible-Light-Driven Photocatalytic Hydrogen Production through Sensitizing TiO 2 via Novel Nanoclusters

Improving the light utilization and electron–hole separation efficiency plays a central role in photocatalysis for converting light energy to hydrogen energy. Herein, for the first time, a stable, highly dispersible discrete T4 [Cd 3 In 17 Se 31 ] 5– cluster is developed as a novel photosensitizer to sensitize TiO 2 for photocatalytic hydrogen production. Compared with pristine TiO 2 (near zero) and the T4 clusters (19.5 μmol g –1 h –1 ) that exhibit low hydrogen evolution activities, the T4/TiO 2 composite, constructed from traces of 0.127 mol % T4 cluster-sensitized TiO 2, exhibits a dramatically improved photocatalytic activity of 328.2 μmol g –1 h –1, highlighting that the photocatalytic efficiency strongly correlates with that of the T4 cluster. In the meantime, the T4/TiO 2 composites are highly stable, remaining robust in a long-time test of 50 h for photocatalytic hydrogen production. Ultrafast transient absorption spectroscopy, in combination with electrochemical analyses, steady-state and time-resolved photoluminescence, and density functional theory calculations, indicates that the T4 cluster not only serve as a photosensitizer to absorb visible light but also form a heterojunction between the interface of the T4 cluster and TiO 2 to accelerate electron injection. This work highlights the great potential of the stable and highly dispersed discrete metal chalcogenide clusters as high-efficiency photosensitizers for converting solar energy to chemical energy.