Synthesis of Tungsten-Modified Sn3O4 through the Cetyltrimethylammonium Bromide-Assisted Solvothermal Method for Dye Decolorization under Visible Light Irradiation

Novel tungsten-modified mixed-valence tin oxides (Sn3O4) with two oxidation numbers, such as Sn2+ and Sn4+, were successfully prepared by the cetyltrimethylammonium bromide (CTAB)-assisted solvothermal method in one-step using tin (II) chloride dihydrate and sodium tungstate (IV) dihydrate as the precursors for dye degradation of methyl orange (MO) under visible light irradiation. The synthesized materials were characterized by various techniques to investigate the surface/structural morphology and the optical property. The presence of tungsten and the optimized amount of CTAB in the preparation method were favorable for the photocatalytic dye degradation reaction. In particular, when 0.03 of CTAB was added to W-modified Sn3O4 (W-Sn3O4@CTAB) and its concentration was 0.6 mg/mL, 10 mg/L of MO could be decolorized almost completely in 40 min, with the apparent reaction rate constant of 0.0496 min(-1). The improvement of photocatalytic activity for this proposed W-Sn3O4 results from increased reduction power, enhanced separation of electron-hole pairs, extended visible light absorption range, and optimized band structure by CTAB additive. The radical trapping experiments showed that the main reactive species during the photocatalytic reaction are superoxide ions. The developed photocatalysts may contribute to the development of environmental improvement technology.