The growth pattern and electronic structures of Cun(n = 1–14) clusters on rutile TiO2(110) surface

Highlights: • The growth pattern and electronic properties of Cu_n (n = 1–14)/TiO₂(1 1 0) were studied by DFT method. • The supported Cu_n (n = 6, 8–14) clusters prefer three-dimensional structures. • The charge transfer from Cu_n clusters to TiO₂ surface was observed. • The visible light irradiation can further enhance the charge transfer from the Cu_n clusters to TiO₂ surface. The growth pattern and electronic properties of Cu_n (n = 1–14) clusters supported on rutile TiO₂(1 1 0) surface have been studied by using the density functional theory method. The calculation results showed that the supported Cu_n (n = 3–5,7) clusters prefer planar or quasi-planar structures, while Cu_n (n = 6,8–14) clusters prefer three-dimensional structures. The stabilities of Cu_n/TiO₂ show an odd–even oscillation behavior with the increasing n, except n = 2 and 7. For the supported Cu_n, the clusters with odd n are more stable than the adjacent clusters. The charge transfer from Cu_n clusters to TiO₂ surface was observed. The electron densities of Cu atoms adjacent to O atoms of the surface are obviously reduced. Electronic structure analysis indicated: (1) Electrons are transferred from Cu_n clusters to the valence band of TiO₂ surface. (2) The states from Cu_n clusters appear in the energy gap of the TiO₂ surface and the energy gaps between the occupied states from Cu_n clusters and the unoccupied states from TiO₂ surface decrease with the increasing n. Our calculations showed that the visible light irradiation can further enhance the charge transfer from the Cu_n clusters (with diameter smaller than 0.6 nm) to TiO₂ surface and facilitate the reduction reactions (such as CO₂ reduction reaction) on the TiO₂ surface.