掺杂基团对氮改性TiO2紫外光催化活性影响的机理研究

以TiCl₄为钛前驱体，采用沉淀法制备了氮掺杂和纯TiO₂. X射线衍射（XRD）和N₂吸附－脱附等温线表征结果表明：所制催化剂以锐钛矿相为主，具有介孔结构. X射线光电子能谱（XPS）证实掺杂的氮以系列NO_x存在. 由紫外－可见漫反射吸收光谱（UV-Vis）可知：氮掺杂TiO₂ ( N-TiO₂ )在400～550nm的可见光区出现新的吸收带. 4-氯苯酚(4-CP)降解实验表明，N-TiO₂的紫外和可见光催化活性均高于纯TiO₂. N-TiO₂具有较高紫外光活性的原因可归于催化剂中含有的NO_x. NO_x在不改变TiO₂禁带宽度的情况下，拓展了它的感光范围，激发更多的光生电子和空穴参与反应，并可降低电子和空穴的复合几率，从而提高了催化剂的紫外光活性.

Mechanism of the Doping Species Controlling the UV Photocatalytic Activity of Nitrogen Doped TiO2

Nitrogen doped and pure TiO₂ photocatalysts were synthesized by precipitation method using TiCl₄ as titanium precursor. Both X-ray diffraction (XRD) and N₂ adsorption desorption isotherms show that the as prepared samples consis of anatase phase except for trace brookite phase with mesoporous structure. X-ray photoelectron spectroscopy(XPS) confirms that the incorporated nitrogen element exists as the chemical state of NO_x. The UV-Vis diffuse reflection absorption spectra (UV-Vis) reveal that the nitrogen doped TiO₂ shows a new absorption region at 400-550nm. The photocatalytic activities of the nitrogen doped TiO2 utilized for the photodegradation of 4-chlorophenol (4-CP) are higher than those of the pure TiO2 under UV and visible light irradiation. The improved photocatalytic activities under UV light irradiation of the nitrogen doped TiO₂ are attributed to the presence of NO_x. With no influence on the energy gap of TiO₂, NO_x can extend the optical response of TiO₂, excite more photoinduced electrons holes for photocatalysis and reduce the recombination probabilities of carriers.