Effects of subnanometer silver clusters on the AgBr(110) photocatalyst surface: A theoretical investigation

The geometrical and electronic structures and photocatalytic performance of subnanometer Ag_n clusters (n = 2-6) deposited on AgBr(110) are studied under the framework of density functional theory (DFT) plus Hubbard U contributions. The most stable adsorption is facilitated by AgBr(110) interacting with the most stable structure of Ag_n and results in a new metal-induced gap band (MIGB) located between the valence (VB) and the conduction bands (CB). Both the MIGB and CB are mainly contributed by the sp hybridization states from the metal clusters, while the VB is composed primarily of the 4p states of the surface Br and the 4d states of Ag from both the adsorbate and the surface. The variety of the electronic structures favors visible and infrared light absorption, which strengthens substantially as the cluster size is enlarged. The dominant localization of the photo-excited electrons on the Ag_n clusters facilitates the oxidation-reduction reactions occurring on the surface and reduces effectively the photolysis of AgBr under sunlight irradiation. The overpotentials of the CB and VB edges indicate that photocatalytic conversion of CO₂ with H₂O to methanol is possible on AgBr(110) deposited with the Ag_n clusters which has been realized experimentally.