Template-free sol-gel preparation and characterization of free-standing visible light responsive C,N-modified porous monolithic TiO₂

Visible light responsive C,N-modified porous monolithic titania (MT_f) has been successfully synthesized. The template-free sol-gel synthesis method accompanied by phase separation and in situ C,N-modification has been used. The molar ratio of water to tetrabutyl titanate (f) in starting solution plays an important role in the porous structure and photoactivity of MT_f. Scanning electron microscopy (SEM) analysis and N₂ adsorption-desorption analysis show that MT_f possess mesoporous structure as well as macroporous structure. MT₂₂ has been further characterized by using X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and UV-vis diffuse reflectance spectra (DRS). The results show that both nitrogen and carbon elements exist in MT₂₂ and result in the visible light photocatalytic activity of MT₂₂. The observed reaction rate of decolorization of methyl orange is 0.0026min^-1.