Mo-N-TiO2光催化剂的制备、表征及其活性提高机制

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。

Preparation and characterization of Mo-N-TiO2 photocatalyst activity enhanced-mechanism

Mo-N-codoped TiO2 nanoparticles 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 molybdate doping amount exhibited the largest photoresponse with its absorption edge shifting to 550 nm.XPS analysis displayed 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 molybdate doping amount on the simulated sunlight photocatalytic performance of modifed TiO2 for degrading RhB were investigated.It was found that the Mo-N-TiO2 calcined at 400℃ with 0.5% ammonium molybdate doping amount exhibited the highest photocatalytic performance.Under the simulated sunlight irradiation with 120 min,the 96.8% degradation rate of RhB could be achieved,which was 2.42 times to that of pure TiO2.