Synthesis of C-N-S co-doped TiO2 mischcrystal with an isobandgap characteristic and its photocatalytic activity under visible light

In this paper, a simple thermal decomposition synthesis route for a carbon-nitrogen-sulfur (C-N-S) co-doped titanium dioxide (TiO 2 ) mischcrystal with an isobandgap property for visible light applications using urea as the C, and N source and titanium( iv ) sulfate [Ti(SO 4 ) 2 ] as S source is reported. The C-N-S co-doped TiO 2 mischcrystal exhibited a unique isobandgap characteristic and prominent red-shift in the ultraviolet-visible absorption spectrum and a much narrower band gap (2.42 eV and 1.39 eV) because of defects and impurity levels which were confirmed using powder X-ray diffraction, diffuse reflectance spectroscopy (DRS), photoluminescence, Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). The excellent photocatalytic performance of the C-N-S co-doped TiO 2 mischcrystal samples was demonstrated using degradation of methylene blue and phenol under visible light. The apparent degradation rate of black TiO 2 is 4-7 times higher than that of C-N-S co-doped TiO 2 (anatase or rutile) under visible light irradiation. The valence band XPS and DRS results were carefully examined to understand the band gap reduction of C-N-S co-doped TiO 2 . This study confirms that the band gap structure of C-N-S co-doped TiO 2 is determined by the mixed crystalline structure and the formation of impurity levels and defective levels. A new idea is presented that will be useful for the design of band gap structure for photocatalysts with higher photocatalytic activities under visible light irradiation. In this paper, a simple thermal decomposition synthesis route for a carbon-nitrogen-sulfur (C-N-S) co-doped titanium dioxide (TiO 2 ) mischcrystal with an isobandgap property for visible light applications using urea as the C, and N Ti(SO 4 ) 2 as S source is reported.