Size Effect of (CuO)n (n = 1–6) Clusters on the Modification of Rutile–TiO2 Photocatalysts

The size‐dependent properties of metal/metal oxide clusters have received increasing interest due to their significant role in promoting heterogeneous catalysis. Herein, an ab initio method is used to investigate the photocatalytic properties of TiO 2 ‐supported (CuO) n nanoclusters ( n = 1−6). The molecular configuration and energetic evolution of gas‐phase (CuO) n clusters are first investigated using a combined simulated annealing–density functional theory (DFT) method, and the quantum size effect is found in planar cluster structures due to the scarcity of electron levels. Subsequently, by supporting the (CuO) n clusters on rutile–TiO 2 (110) facets, the stability, the light‐absorption ability, the charge separation efficiency, and the reactivity of excited electrons for different (CuO) n −TiO 2 heterojunctions are analyzed. It is noted that (CuO) 3 and (CuO) 4 clusters have the best antiaggregation property, and the small clusters usually possess higher charge separation efficiency, whereas large clusters show better light‐absorption performance. Photocatalytic hydrogen evolution reaction is favored on middle‐sized CuO clusters‐modified TiO 2 , e.g., (CuO) 3 −TiO 2 , due to its proper band alignment, high photoelectron reactivity, good light‐absorption ability, and structural stability.