Control of valence states in Rh-doped TiO2 by Sb co-doping: A study by high resolution X-ray photoemission spectroscopy

► Rh doping in TiO2 introduces new states above the valence band edge. ► Rh induced states may be observed directly in photoemission spectra. ► Rh doping pins Fermi level at lower energy than in undoped material. ► Sb co-doping restores Fermi level to close to conduction band minimum. ► Sb co-doping ensures Rh substitutes into TiO2 as Rh(III).