Abstract

In this work, sulfur (S) doped (001)-face exposed TiO₂ was synthesized via the vapor-thermal method at 180 °C or 250 °C, with an S/Ti molar ratio R_S/Ti of 0, 0.5, 1, 2, 3, 4, and 5. The S-doped samples at 250 °C exhibited significantly improved photocatalytic performance. The effects of S doping were as follows: (1) The S element exhibits different chemical states in the samples with different R_S/Ti. Specifically, it exists in the form of S²⁻ replacing O²⁻ at R_S/Ti = 1, and S⁶⁺ replacing Ti⁴⁺ at R_S/Ti ≥ 2. As a result, S doping causes a lattice distortion because the ionic radii of S²⁻ and S⁶⁺ differ from that of the O²⁻ and Ti⁴⁺. (2) S-doping increases the adsorption coefficient A_e for methylene blue (MB) from 0.9% to 68.5% due to the synergistic effects of the oxygen vacancies, the SO₄²⁻ adsorbed on the TiO₂ surface, and the pore size. (3) S-doping increases the MB degradation rate from 6.9 × 10⁻² min⁻¹ to 18.2 × 10⁻² min⁻¹ due to an increase in the amount of •OH and •O²⁻ radicals.

Keywords: Vapour-thermal; S-doping; TiO₂; photocatalytic properties; chemical state

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Sun, X.; Zhang, X.; Sun, X.; Qian, N.; Wang, M.; Ma, Y. Beilstein Arch. 2019, 201944. doi:10.3762/bxiv.2019.44.v1

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