Complete photocatalytic mineralization of Nile blue on hetero-structured CoTiO₃ nano-composite coated on glass in a sol–gel process using diethylene glycol as stabilizer: effect of charge separation and calcination temperature on activity

Hetero-structured CoTiO₃ nano-composite photocatalyst was produced by a modified sol–gel process diethylene glycol as as stabilizer and coated on glass as a thin film by Doctor Blade coating. CoTiO₃ nano-composites were calcinated at 550, 650 and 750 °C to study the structure and phase formation of CoTiO₃ nano-composites. X-ray diffraction results showed that the pure CoTiO₃ nano-crystalline phase is formed at 650 °C while Co₃O₄ and TiO₂ were present as impurities at 550 and 750 °C annealing temperatures. Field emission scanning electron microscopy and energy dispersive X-ray spectroscopy analysis of hetero-structured CoTiO₃ nano-composite coated on a glass reveal the formation of spherical shape of nano-crystalline phases with an average size of 75 nm. The Fourier transform infrared spectroscopy results showed the existence of Co–O, Ti–O, and Ti–O–Co bonds. Thermogravimetric and derivative thermogravimetric analysis show that the weight loss phases are completed at 750 °C with peak temperatures of 107 and 345 °C. The UV–vis diffuse reflectance spectra reveal the optical band gaps of 1.587 eV (781 nm) and 2.079 eV (596 nm). Photocatalytic activity of hetero-structured CoTiO₃ nano-composite photocatalyst was examined for degradation of Nile blue dye and the results showed complete degradation in 2.5 h of light irradiation. This is attributed to the efficient separation of electron–hole pairs of the CoTiO₃ nano-composite, narrow band gap, and visible-light harvesting ability.