Photocatalytic Performance Research On The Composites Of TiO₂ Nanobelts

In recent years,one-dimensional(1-D)semiconductor nanostructures,such as nanotubes,nanorods,nanowires and nanobelts,have placed a premium on considerable research upsurge in a myriad of filed,such as solar cells,lithium-ion batteries,gas sensors,and especially for photocatalysis.Among them,TiO2 nanobelts(TNBs)become to be the potential application value and perfect photocatalyst in the field of semiconductors and optoelectronic field,owing to the unique geometry of the structure and physical properties.Firstly,1-D nanobelts structure facilitates fast and long-distance electron transport along the axial direction.Secondly,TNBs have relatively chemical stability and large surface area because of the high crystallinity and high length-to-diameter ratio,which make it an ideal building block for assembling various surface heterostructures.Nevertheless,TNBs always encompass the intrinsic drawbacks of limited sunlight utilization and the relatively high combination of photoinduced electron-hole pairs on the surface or inside,resulting in low quantum efficiency of photocatalytic reactions.Therefore,in my dissertation,TNBs complexes were synthesized to improve the separation effect of photo-generated carriers and enhanced the photocatalytic activity of degradation of liquid organic contaminants.Firstly,we have fabricated a well-defined TNBs/Ag binary heterostructure by the electrostatic self-assembly method.TNBs/Ag-4H binary heterostructure exhibited the best photocatalytic activity toward degradation of methylene blue(MB)under UV irradiation.The main reason is that a certain amount of Ag NPs serve as the efficient"electron reservoir" to prolong the lifetime of the photogenerated electron-hole pairs,thus giving rise to the significantly enhanced photocatalytic performance of the binary heterostructure.Secondly,the TNBs/ZnO binary heterostructures were synthesized by a one-step pyrolysis approach of Zn(NO3)2.TNBs/ZnO-2 binary heterostructure exhibited the best photocatalytic activity toward degradation organic pollutant(Rhodamine B)under UV irradiation.It is ascribed to synergy effect of grafted ZnO layer and TNBs,thus concurrently improving the separation effect of photogenerated carriers,prolonging the lifetime of photoindued electron-hole pairs and resulting in remarkably enhanced photoactivity.Thirdly,photochemical reduction was carried out to achieve Ag nanoparticles(Ag NPs)deposition on the surface of TNBs/ZnO heterostructures.TNBs/ZnO/Ag ternary heterostructure have the best photocatalytic activity toward degradation organic pollutant(Rhodamine B)under UV irradiation.The primary reason is due to the formation of the double heterojunctions between Ag,ZnO and TNBs.the ZnO layer could serve as favorable hole channels and receptors and Ag NPs serve as efficient "electron reservoir",thus concurrently improving the separation effect of photo-generated carriers,prolonging the lifetime of photogenerated electron-hole pairs and resulting in remarkably enhanced photoactivity.In addition,the primary active species were determined by ESR and control experiments,and we also elucidated the possible photocatalytic mechanism.