Preparation And Photocatalytic Activity Of Visible Light Induced Nitrogen And Metal Ions Codoped TiO₂ Photocatalysts

TiO₂ which can degrade the organic pollutants is the most prospective photocatalyst due to its nontoxicity, long-term stability, low cost, and, water-fast. However, the widespread technological use of TiO₂ is hindered by its wide band gap (3.2eV) and the requirement of ultraviolet irradiation (wavelength λ<380nm) for photocatalytic activity. In order to efficiently utilize visible light, which occupies the main part of the solar spectrum, it is the key part to shift TiO₂ optical response from the UV to the visible spectral range.The TiO₂ nanoparticles photocatalysts codoped with nitrogen and the transition matel ions such as La, Ce, Mn, Fe and Zn, were prepared by sol-gel and characterized by DRS, XRD, TG-DSC, XPS. The photocatalytic activities of the prepared photocatalysts under visible light irradiation were evaluated by monitoring the degradation of acid orange red or methyl orange dye, a probe pollutant. We intend to acquire the codoping mechanism and the relationship between codoping and photoactivity to instruct the next experiment.The results indicate the TiO₂ photocatalysts codoped with nitrogen and metal have good visible light responsivity. Compared with non-doped TiO₂ and nitrogen doped TiO₂, the N-M codoped TiO₂ show a better optical absorption coefficient in visible light range. Their band gaps minish, which result in the absorption threshold shift to the visible light range. The crystal type of N-M codoped TiO₂ photocatalyst is anatase TiO₂ and few rutile. The grain size of photocatalysts mainly distributes from 10nm to 20nm. The XPS of the N-M codoped TiO₂ photocatalysts imply that the photocatalyst is composed of N, O, Ti⁴⁺ and metal ions. In contrast with the non-doped TiO₂, N-TiO₂ and metal doped TiO₂, the degradation for acid orange red or methyl orange over N-M codoped TiO₂ photocatalysts under visible light irradiation is variable for different metal doping concentration. There is a best doping concentration for activity.