Effects of Valence Electron Layer Thickness of Metal Clusters on Electron-Hole Separation at the Metal/TiO2 Interface

To elucidate the effects of valence electron layer thickness of metal clusters on charge separation in TiO2 surface, we have conducted nonadiabatic molecular dynamics simulations. Our simulations demonstrate that the valence electron transfer from the conduction band of TiO2 to metal clusters significantly depends on the type of metal clusters. As the thickness of the valence electron layer of metal cluster approaches that of Ti atoms, the valence electrons more easily transfer from the metal cluster to TiO2, giving rise to a strong built-in electric field. Furthermore, the establishment of this built-in electric field intensifies the nonadiabatic (NA) coupling between the metal cluster and TiO2, resulting in a rapid photogenerated electron transfer from the TiO2 surface to the metal clusters and efficient charge separation. Thus, the electron transfer times follow the order of Au-13/TiO2 > Ag-13/TiO2 > Cu-13/TiO2. These results provide critical new insights into developing highly efficient photocatalysts by adjusting the valence electron layer thickness of metal clusters to enhance charge separation and prolongs charge carrier lifetimes, improving overall catalytic efficiency.