Au cluster anchored on TiO 2 /Ti 3 C 2 hybrid composites for efficient photocatalytic CO 2 reduction

Abstract The size of metal nanoparticles is a key factor to enhance the photocatalytic activity of photocatalysts. However, the mechanism of this factor to the improvement of photocatalytic CO 2 reduction performance is still unclear. Here, Au cluster/TiO 2 /Ti 3 C 2 and Au nanoparticle/TiO 2 /Ti 3 C 2 were successfully prepared by deposition–precipitation method. The experimental results show that the photocatalytic CO 2 reduction performance of Au cluster/TiO 2 /Ti 3 C 2 with quantum size effect is stronger than that of Au nanoparticle/TiO 2 /Ti 3 C 2 with surface plasmon resonance. The enhanced photocatalytic CO 2 reduction activity is assigned to the establishment of an overlapping orbital between the lowest unoccupied molecular orbital (LUMO) of the Au cluster and the anti‐bonding orbital of CO 2 , which greatly promotes the activation efficiency of CO 2 . The existence of Au cluster and the mechanism of photocatalytic CO 2 reduction performance were certified by high‐angle annular dark‐field scanning transmission electron microscopy (HAADF–STEM) and in situ Fourier transform infrared spectroscopy (ISFTIR). This work may open new opportunities for the establishment of stable and active metal nanocatalysts.