Theoretical investigation of Cu5/silicates deposited on rutile TiO2 as a photocatalyst

Abstract

Titanium dioxide (TiO2) is an exceptional compound with unique optical properties, which have been intensively used for applications in photocatalysis. Recent studies show that Cu5 atomic quantum clusters (AQCs) could facilitate visible light absorption and enhance the photocatalytic properties of rutile TiO2 by creating mid-gap states. In this work, to move the theory of these catalysts closer to the experiment, we investigate the electronic structures of Cu5 adsorbed on a perfect and reduced rutile TiO2 surface in the absence and presence of silicate SiO_3^(2-) ions, which are introduced for the purification of Cu5 AQCs. Encouragingly, our DFT simulations predict that the presence of SiO_3^(2-) does not reduce the gap states of the Cu5@TiO2 composite and could even enhance them by shifting more states into the band gap. Our results also demonstrate that the polarons created by oxygen vacancies (Ov) and Cu5 coexist within the band gap of TiO2. Indeed an Ov behaves like a negative gate on the electronic states located on the AQCs, thereby shifting states out of the valence band into the band gap, which could lead to enhanced photocatalytic performance.