Preparation And Photocatalytic Properties Of Nitrogen-doped TiO₂ Photocatalyst

In the field of environment pollution abatement, of the materials being developed for photocatalytic applications, TiO₂ remains the most promising due to its high efficiency, low cost, chemical inertness, and photostability etc. However, the use of TiO₂ photo catalyst has been restrained by its only activated under UV radiation, and this limits its utilization of sun's energy and application significantly, thus any red-shift in the optical response of TiO₂ from the UV band to the visible band will have a profound positive effect on the photocatalytic efficiency of the materials. Recently, the desired band gap narrowing of TiO₂ can be achieved by replacing lattice oxygen with anionic dopant species, especially nitrogen doping TiO₂ particles or thin films, receiving a lot of attention for its effective response to the visible region and photostability.In this study, N-doped TiO₂ nanoparticles and thin films were prepared with urea as nitrogen source, which structure and properties of catalysts were characterized by SEM, TEM, XRD, FT-IR, DRS, BET and XPS, in addition, the activities of the catalysts were estimated by photocatalytic degradation of cationic dye aqueous of Rhodamine B under ultraviolet light irradiation.V and N co-doped TiO₂ prepared by hydrothermal method with TiCl₃ as a precursor were all the anatase crystal structure. In contrast to the N-doped samples, the V and N co-doped TiO₂ catalysts showed higher photocatalytic activity than N-doped TiO₂ resulted from the synergetic effect of the doped N and V. The highest catalytic efficiency of co-doped TiO₂ catalysts was obtained at 0.045at% V⁵⁺ doping content and urea/TiCl₃ molar ratio of 4.N-TiO₂ nanoparticles were prepared by modified sol-gel method with tetrabutyl titanate as a precursor, and the N-TiO₂ calcined at 300-500℃for 2h were all anatase crystal structure. The N-TiO₂ calcined at 300℃(6-nm-sized nanoparticle) with a high surface area of 167.2 m²/g had already obtained the desired crystallinity. From the XPS analysis, the wide peak around 399.8 eV in N1s core levels was observed, indicating that nitrogen was doped into substitutional sites of O in TiO₂, providing structural information for O-Ti-N formation, the substitutional doping and nitrogen adsorbed compounds such as NO_x or NH_x were formed on TiO₂ surface. From the principle analysis, it was found that urea has taken part in the hydrolysis of TBT, a large number of -NH₂ existed in N-TiO₂ gel may have great effect on surface structure of TiO₂ particle and photocatalytic activity. N-TiO₂ thin films were prepared on nickel mesh, nickel sheet and Al sheet by a sol-gel-diping method. The effect results of different coat thickness and substrates on the photodegradation of RB showed that the highest catalytic efficiency of N-TiO₂ thin film was of 5 layers on nickel mesh. According to UV-Vis optical spectrum of thin films, the absorption edge of synthesized N-TiO₂ thin film reached at 600nm by extending the activating spectrum to the visible range. The photocatalytic activity of N-TiO₂ nanoparticle and thin film were all improved by nitrogen doping.