First-Principles Study of S Doping at the Rutile TiO2 (110) Surface

The structural, energetic, and electronic properties of various S-doping Configurations by substitution and adsorption at the Futile TiO2 (110) surface have been investigated by first-principles density functional theory calculations. The stability of these configurations has been compared on the basis of the Calculated formation and adsorption energies. Our results indicate that S dopants replace surface O atoms or bind to Ti atoms preferentially. Moreover, implantation of S dopants into the rutile lattice favored the formation of oxygen vacancies, which promotes further S incorporation. Doping of single S atoms into Ti sites (S-cation (loping) led to relatively small reductions of the photon transition energy, while S-substitution of O atoms (S-anion doping) and adsorption on the Surface (S-cation/anion doping) resulted in significant red shifts of the optical absorption edge. Our results Suggest that the interplay between S impurities and oxygen vacancies does not enhance visible light absorption in an obvious way, and helps to rationalize recent experimental Studies.