Synthesis and characterization of nanostructured Co-Si co-doped TiO2 with enhanced visible-light photocatalytic performance in phenol red degradation

Visible-light active Co-Si co-doped TiO 2 powders with varying dopants concentration were successfully synthesized by simple precipitation method followed by annealing at 350, 600 and 900 °C. Structural and morphological characterization was performed using SEM, TEM, XRD, XPS, FT-IR, FT-Raman, UV–vis and PL spectroscopy. X-ray diffraction and Raman spectroscopy confirmed that materials annealed at 350 and 600 °C consist of anatase as the main phase, while those treated at 900 °C are multiphase composites consisting of anatase, rutile, and CoTiO 3 . FT-IR spectroscopy revealed the presence of functional groups related to SiO 2 and CoTiO 3 phases. UV-vis spectra of co-doped TiO 2 showed a red-shifted absorption edge and absorption peaks in the visible spectral range near 610 nm. Band gap energy estimated from Tauc’s plots showed a significant decrease with Co doping, reaching a minimum of 2.25 eV at a Co/Si ratio of 0.17. Formation of additional defect levels located in the optical band gap due to co-doping was confirmed by photoluminescence spectroscopy. XPS analysis revealed that cobalt was present in the +2-oxidation state. The prepared Co-Si co-doped TiO 2 materials showed photocatalytic activity in the reaction of phenol red degradation under visible light, with maximum photodegradation efficiency of above 90% in 120 min discovered for samples annealed at 350 and 600°C. These results suggest that Co-Si co-doped anatase TiO 2 offer improved photocatalytic performance for application in wastewater purification under sunlight.