Size transformation of Au nanoclusters for enhanced photocatalytic hydrogen generation: Interaction behavior at nanocluster/ semiconductor interface

Recently, atomically precise metal nanoclusters (NCs) become a new class of photosensitizer for light energy conversion in metal-cluster-sensitized semiconductor (MCSS) system. However, fundamental understanding for the suitable combination of NCs and semiconductor is still unclear. Aside from aspects of light harvesting, energy level alignment and catalytic activity, interfacial interaction behavior at NCs/semiconductor interface is also crucial due to its important influence in charge transportation. In this work, the interface interaction between Au NCs and TiO2 is examined by precise transformation of Au NCs from Au22(SG)18 to Au18(SG)14, as well as its effect on photocatalytic hydrogen production activity. From the optical, charge transport and solid-states spectroscopy analyses, it is able to display that precisely tuning the number of core atoms from Au22(SG)18 to Au18(SG)14 results in the strong interface interaction between Au NCs and TiO2, reflecting in high difference of work function and modified surface band bending of TiO2, therefore promoting the injection of electrons from NCs to TiO2 and reducing interfacial charges recombination. As a result, Au18(SG)14/TiO2 shows higher hydrogen generation rate than Au22(SG)18/TiO2 under light irradiation. This work would provide new insights into rational combination of metal NCs with semiconductor and highlights the overlooked effect of interfacial interaction behavior on light energy conversion.

Automated summary

Recently, metal nanoclusters have been used as photosensitizers in metal-cluster-sensitized semiconductor systems, but the suitable combination of nanoclusters and semiconductors is still not clear. In this study, the interaction between Au nanoclusters and TiO2 was examined, and it was found that tuning the number of core atoms in the nanoclusters resulted in a strong interface interaction, promoting electron injection from the nanoclusters to TiO2 and reducing interfacial charge recombination. As a result, Au18(SG)14/TiO2 showed higher hydrogen generation rate than Au22(SG)18/TiO2 under light irradiation. This work provides new insights into the rational combination of metal nanoclusters with semiconductors and highlights the importance of interfacial interaction behavior in light energy conversion.