Mo-N-TiO_2光催化剂的制备、表征及其活性提高机制

Preparation and characterization of Mo-N-TiO_2 photocatalyst activity enhanced-mechanism

以钼酸铵和氨水分别为钼源和氮源,采用溶胶-凝胶法制备了Mo-N-TiO2光催化剂,并对其进行了XRD、XPS和UV-visDRS表征。XRD结果表明,Mo、N共掺杂有效抑制了TiO2晶粒的生长,提高了TiO2由锐钛矿向金红石相的转变温度。UV-vis表明,Mo-N-TiO2光催化剂可见光吸收能力增强,吸收带边明显"红移",且钼酸铵添加量(相对TiO2)为0.5%的样品"红移"程度最大,最大吸收带边为550 nm。XPS分析结果表明,Mo取代了TiO2晶格中的部分Ti4+,以Mo6+形式存在的,而N以Ti—N及N—Ti—O形式存在。以罗丹明B为模型污染物,重点考察了钼酸铵添加量与焙烧温度对Mo-N-TiO2光催剂性能的影响。结果表明,400℃焙烧下、钼酸铵添加量为0.5%的样品催化活性最好。模拟太阳光下光照120min对罗丹明B的降解率达到96.8%,是纯TiO2的2.42倍。

Mo-N-codoped TiO2nanoparticles were synthesiezed by a sol-gel method using ammonium molybdate and ammonia water as the Mo source and N source, respectively. The resulting materials were characterized by XRD, XPS and UV-vis DRS. XRD showed that doping with Mo and N could effectively restrain the growth of crystallite and enhance the temperature of phase transformation from anatase to brookite. The UV-vis DRS results showed that the light absorption edge was extended to visible light region. Moreover, the modified TiO2 with 0.5% ammonium molyb- date doping amount exhibited the largest photoresponse with its absorption edge shifting to 550 nm. XPS analysis dis- played that Mo existing as cationic Mo6＋ by replacing Ti4~ and the structure of nitrogen was unsymmetric which could be attributed to the formation of O--Ti--N and Ti--N. The effects of calcination temperature and ammonium molyb- date doping amount on the simulated sunlight photocatalytic performance of modifed TiO2 for degrading RhB were in- vestigated. It was found that the Mo-N-TiO2 calcined at 400C with 0.5% ammonium molybdate doping amount exhib-ited the highest photocatalytic performance. Under the simulated sunlight irradiation with 120 min, the 96.8% degra- dation rate of RhB could be achieved, which was 2.42 times to that of pure TiO2.