Characterization and activity of visible-light-driven TiO2 photocatalyst codoped with nitrogen and cerium

Nitrogen and cerium codoped TiO2 photocatalysts were prepared by a modified sol–gel process with doping precursors of cerium nitrate and urea, and characterized by X-ray diffraction (XRD), thermogravimetry–differential scanning calorimetry (TG–DSC), X-ray photoelectron spectra (XPS) and ultraviolet–visible light diffuse reflectance spectra (UV–vis DRS). Results indicate that anatase TiO2 is the dominant crystalline type in as-prepared samples, and CeO2 crystallites appear as the doping ratio of Ce/Ti reaches to 3.0 at%. The TiO2 starts to transform from amorphous phase to anatase at 987.1 K during calcination, according to the TG–DSC curves. The XPS show that three major metal ions of Ce3+, Ce4+, Ti4+ and one minor metal ion of Ti3+ coexist on the surface. The codoped TiO2 exhibits significant absorption within the range of 400–500 nm compared to the non-doped and only nitrogen-doped TiO2. The enhanced photocatalytic activity of the codoped TiO2 is demonstrated through degradation of methyl orange under visible light irradiation.