| Summary: | In the present work, phenol was used as a model molecule to the photocatalytic evaluation of TiO<sub>2</sub> impregnated with iron sulphide and chlorine on a visible-light reactor. The iron–chlorine catalyst was prepared by incipient impregnation with the metal precursors, Fe (NO<sub>3</sub>)<sub>3</sub> and NaCl on previously calcined TiO<sub>2</sub>. The catalyst was sulphurized with H2S at 300 °C for 1 h. The catalysts were prepared at different chlorine concentrations using HYDRA chemical equilibrium diagrams to obtain different fractions of FeCl<sup>+</sup>. The oxide catalysts were characterized with diffuse reflectance (DRS UV–Vis) and temperature programmed reduction analysis (TPR). Sulphurized catalysts were characterized with Raman spectrometry and X-ray photoelectron spectrometry (XPS). The FeS–2Cl/TiO<sub>2</sub> catalyst presented 8.35 times higher photodegradation than TiO<sub>2</sub> and 6.4 times higher compared to the FeS–0.25Cl/TiO<sub>2</sub> catalyst. DRS and XPS showed similar results of band gap, proving that the catalyst remain stable after sulphurisation. The TPR results of FeS–2Cl/TiO<sub>2</sub> showed an increment of 86.29% in Fe<sup>2+</sup>/Fe<sup>3+</sup> compared to FeS–0.25Cl/TiO<sub>2</sub>. XPS and Raman results for oxide and sulphated iron species relation suggested that FeS–2Cl/TiO<sub>2</sub> decreased 4.45% compared to FeS–0.25Cl/TiO<sub>2</sub> catalyst. XPS semiquantitative for S/Fe results showed that the FeS–2Cl/TiO<sub>2</sub> catalyst increased 73.17% in comparison to FeS–0.25Cl/TiO<sub>2</sub>. These results suggested the increment of sulphurisation degree for FeS–2Cl/TiO<sub>2</sub>. In this regard, the catalyst characterization results showed that the presence of FeCl<sup>+</sup> (0.85 fractions) in solution before impregnation promoted the active sulphide species maintaining the band gap and improved the degradation of phenol on visible light.
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