Highly visible-light-active sulfur and carbon co-doped TiO (SC-TiO) heterogeneous photocatalysts prepared by underwater discharge plasma.

To promptly and simply create highly crystalline S/C co-doped TiO (SC-TiO) photocatalysts at room temperature and atmospheric pressure, we suggest a novel plasma-assisted sol-gel synthesis method. This method is a simultaneous synthetic process, in which an underwater plasma undergoes continuous reactions to generate high-energy atomic and molecular species that enable TiO to achieve crystallinity, a large surface area, and a heterogeneous structure within a few minutes. In particular, it was demonstrated that the heterogeneously structured TiO was formed by doping that sulfur and carbon replace O or Ti atoms in the TiO lattice depending on the composition of the synthesis solution during underwater plasma treatment. The resultant SC-TiO photocatalysts had narrowed bandgap energies and extended optical absorption scope into the visible range by inducing the intermediate states within bandgap due to generation of oxygen vacancies on the surface of TiO through synthesis, crystallization, and doping. Correspondingly, SC-TiO showed a significant degradation efficiency ([k] = 6.91 h) of tetracycline (TC, antibiotics) under solar light irradiation, up to approximately 4 times higher compared to commercial TiO ([k] = 1.68 h), resulting in great water purification. Therefore, we anticipate that this underwater discharge plasma system will prove to be an advantageous technique for producing heterostructural TiO photocatalysts with superior photocatalytic efficiency for environmental applications.