The nature and effects of rhodium and antimony dopants on the electronic structure of TiO2: towards design of Z-scheme photocatalysts

Abstract

The nature and effects of rhodium and antimony doping in TiO₂ have been investigated using X-ray diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), Extended X-ray Absorption Fine Structure (EXAFS) analysis, X-ray Absorption Near Edge Structure (XANES) analysis and diffuse reflectance spectroscopy. Together these techniques build up a comprehensive picture of the dopant chemistry in this system. A range of Sb/Rh ratios have been analysed, and it is shown that the Fermi level can be tuned within the band gap through control of dopant stoichiometry, offering the possibility of designing Z-scheme components with specific band offsets. Spontaneous spatial segregation of dopants is measured using TiO₂ (110) single crystals. This is shown to have a direct impact on the electronic structure in the region of the semiconductor surface, creating band bending that is expected to be critical for photocatalytic activity of these materials.