Bifunctional N-Doped Mesoporous TiO2 Photocatalysts

We have successfully prepared visible-light-active mesoporous N-doped TiO2 (N-TiO2) photocatalysts by the precipitation of titanyl oxalate complex ([TiO(C2O4)(2)](2-)) by ammonium hydroxide at a low temperature followed by calcination at different temperatures. The structures of N-TiO2 photocatalysts have been characterized in detail by means of powder X-ray diffraction, N-2 adsorption-desorption isotherms, infrared spectroscopy, diffuse reflectance UV-vis spectroscopy, X-ray photoelectron spectroscopy, and transmission electron microscope. The calcination process of the catalyst precursor was also studied by means of temperature-programmed reaction spectroscopy. N-TiO2 Photocatalysts exhibit comparable UV-light activity and visible-light activity in the photodegradation of methyl orange. The doped N species locates at the interstitial sites in TiO2, which leads to the band gap narrowing of TiO2. A novel and interesting result is that N-doped TiO2 calcined at 400 degrees C (N-TiO2-400) has Bronsted acid sites arising from covalently bonded dicarboxyl groups, which greatly enhances the adsorption capacity for methyl orange. The N-TiO2-400 catalyst is a promising adsorption-photodegradation integration catalyst; meanwhile, it is also a promising acid catalysis-photocatalysis bifunctional catalyst.