Influence of Ag Clusters on the Electronic Structures of β-Ga2O3 Photocatalyst Surfaces.

Abstract

In order to understand the photocatalytic carbon dioxide reduction over Ag-loaded β-Ga2O3 photocatalysts, first principles calculations based on density functional theory were performed on the surface model of a Ag cluster-adsorbed β-Ga2O3 system. The stable adsorption structures of Agn (n = 1 to 4) clusters on the β-Ga2O3 (100) surface were determined. In the electronic structure analysis, the valence states of all Ag clusters mixed with the top of the O 2p valence band of Ga2O3, leading the Fermi level of Agn/β-Ga2O3 to shift to the bottom of the conduction band. It was also revealed that the unoccupied states of Agn clusters overlapped with the Ga unoccupied states, and occupied electronic states of Ag clusters were formed in the band gap. These calculation results corresponded to the experimental ones obtained in our previous study, i.e., small Ag clusters had strong interaction with the Ga2O3 surface, enhancing the electron transfer between the Ag clusters and the Ga2O3 surface. That is, excited electrons toward Agn clusters or the perimeter of Ag-Ga2O3 should be the important key to promote photocatalytic CO2 reduction.