jp312197g_si_001.pdf (110.6 kB)
Anionic or Cationic S‑Doping in Bulk Anatase TiO2: Insights on Optical Absorption from First Principles Calculations
journal contribution
posted on 2013-05-02, 00:00 authored by M. Harb, P. Sautet, P. RaybaudUsing first principles calculations,
we investigate the structural,
electronic, optical, and energetic properties of S-doped anatase TiO2 bulk systems. To ensure accurate band gap predictions, we
use the HSE06 exchange correlation functional, and the absorption
spectra are obtained with density functional perturbation (DFPT) theory
by employing HSE06. Various oxidation states (anionic and cationic)
of sulfur are considered depending on the location in bulk TiO2: in interstitial position or in substitution for either oxygen
or titanium atoms. Among the explored structures, two anionic and
one cationic configurations induce an improved optical absorption
response in the visible region as observed experimentally. Moreover,
we undertake a thermodynamic analysis as a function of the chemical
potential of oxygen and considering three relevant sulfur chemical
doping agents (S2, H2S, and thiourea). It highlights
that cationic configurations (S4+ and S6+) are
strongly stabilized in a wide range of oxygen chemical potential (including
standard conditions), whereas anionic species are stabilized only
at very low chemical potential of oxygen. The metastable cationic
Ti(1–2x)O2S2x system involving the presence of S4+ species
in substitution for Ti4+, with the formation of SO2 units, should offer the best compromise between the thermodynamic
conditions and the expected optical properties.