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.