Au cluster anchored on TiO2/Ti3C2 hybrid composites for efficient photocatalytic CO2 reduction

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 CO2 reduction performance is still unclear. Here, Au cluster/TiO2/Ti3C2 and Au nanoparticle/TiO2/Ti3C2 were successfully prepared by deposition–precipitation method. The experimental results show that the photocatalytic CO2 reduction performance of Au cluster/TiO2/Ti3C2 with quantum size effect is stronger than that of Au nanoparticle/TiO2/Ti3C2 with surface plasmon resonance. The enhanced photocatalytic CO2 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 CO2, which greatly promotes the activation efficiency of CO2. The existence of Au cluster and the mechanism of photocatalytic CO2 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.Graphical abstract