Boosting Visible-Light-Driven Photocatalytic Hydrogen Production through Sensitizing TiO₂ 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 [Cd3In17Se31]5– cluster is developed as a novel photosensitizer to sensitize TiO2 for photocatalytic hydrogen production. Compared with pristine TiO2 (near zero) and the T4 clusters (19.5 μmol g–1 h–1) that exhibit low hydrogen evolution activities, the T4/TiO2 composite, constructed from traces of 0.127 mol % T4 cluster-sensitized TiO2, 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/TiO2 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 TiO2 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.