Bifunctional N-Doped Mesoporous TiO₂ Photocatalysts

Abstract

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, N2 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 °C (N-TiO2-400) has Brönsted 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.