西北师大光催化二氧化钛.ppt

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1、报告人：安宁单 位：西北师范大学化学化工学院 生态环境相关高分子材料教育部重点实验室日 期：2012年11月17日,文献阅读汇报,Semiconductor-mediated photodegradation of pollutants under visible-light irradiation,Chem.Soc.Rev.,2010,39,42064219,The adsorbed dye or other color species can absorb visible light to be excited.The excited species can inject electron

2、s into the conduction band of the semiconductor,forming conduction band electrons(ecb-)and the oxidized antenna molecules to realize the charge separation(2)and(3).,1.Introduction,2.Background and mechanistic features2.1 Activation of O2 and organic pollutants at room temperature,A线：三重态的3O2与线状有机化合物在

3、没有催化剂的条件下反应需要翻越很高的能垒,B线：当催化剂与氧气和有机污染物一 起反应时就会形成如S1的稳态中间体和如T1、T2的过渡态中间体。这个过程相对于之前需要少得多的能量。,C线：光化学作用会为反应提供一定的能量。,The absorption of a photon with energy larger than the band gap of the semiconductor can excite an electron from the valence band to the conduction band.This bandband excitation produces th

4、e reductive conduction band electrons(ecb-)and oxidative valence band holes(hvb+).,超氧自由基负离子,能垒很小的反应,(1)it possesses suitable redox potentials of conduction band and valence band to ensure the simultaneous reduction of O2 and oxidation of the H2O or organic compounds;(2)It also has many desirable pro

5、perties as environmental photocatalysts,such as high efficiency,ready availability,non-toxicity,and high chemical stability.,TiO2：,2.2 Efficient use of visible light from the sun,SMPD(Semiconductor-mediated Photodegradation),(1)在有氧气的环境下，当照射可见光TiO2会分解染料(eqn 10).,(2)在染料同时生成的有机自由基和活性氧会吸引其他共存的有机污染物，并将他们

6、分解(eqn 11).,(3)通过染料改性的催化剂可以在可见光下分解无色的有机污染物同时自身的有颜色的有机集团在反映后不会发生分解和变色(eqn12).,(4)有机卤化物可以被注入的电子还原发生脱卤素反应(eqn 13).,2.3 Mechanistic characteristics of SMPD,Photogenerated Holes,2.4 Role of the semiconductor in SMPD,b:从有机染料注入的电子转向半导体表面；c:电子被捕获；d:电子与电子受体发生反应；e:电子克服能垒从捕获陷阱中出来；f:反向转移到被氧化的有机染料上,3.SMPD of org

7、anic pollutants3.1.1 SMPD of organic dye pollutants themselves,(A)TiO2 表面的羟基与染料的羧基发生酯化作用。,(B)邻位的两个羟基与氧原子形成二配位的螯合共价键。,3.1.2 Performance of the degradation of dye pollutants by SMPD.,Rate of decolorization,Extent of mineralization to CO2,H2O and other inorganic species,Formation of intermediates and p

8、roducts,The degradation process of the dyes can be characterized by several parameters,3.2 Removal of co-existing pollutants on TiO2 modified by organic dyes,活性氧离子,颜料自由基,苯酚、水杨酸、苯硫酚、苯醌等有机污染物,卤素化合物、高价态过渡金属离子,3.3 Effects of surface modification on SMPD,然而催化剂吸附上具有很强氧化性质的过渡金属离子如(Cu2+or Fe3+)时，TiO2 的活性会降低。,Thank You!,