Influence of Ag Clusters on the Electronic Structures of β-Ga 2 O 3 Photocatalyst Surfaces.

In order to understand the photocatalytic carbon dioxide reduction over Ag-loaded β-Ga 2 O 3 photocatalysts, first principles calculations based on density functional theory were performed on the surface model of a Ag cluster-adsorbed β-Ga 2 O 3 system. The stable adsorption structures of Ag n ( n = 1 to 4) clusters on the β-Ga 2 O 3 (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 Ga 2 O 3 , leading the Fermi level of Ag n /β-Ga 2 O 3 to shift to the bottom of the conduction band. It was also revealed that the unoccupied states of Ag n 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 Ga 2 O 3 surface, enhancing the electron transfer between the Ag clusters and the Ga 2 O 3 surface. That is, excited electrons toward Ag n clusters or the perimeter of Ag-Ga 2 O 3 should be the important key to promote photocatalytic CO 2 reduction.