Preparation,Modification And Photocatalytic Activity Of TiO₂ Nanobelts

Currently,TiO₂ is the most widely studied semiconductor photocatalyst due to its advantages,such as non-toxicity,high chemical stability and low cost.However,it can only absorb ultraviolet light because of its wide band gap?³.2 eV?,while the content of ultraviolet light in sunlight is only about 4%,which leads to its low utilization of solar energy;the high recombination rate of photogenerated carriers leads to its relatively low quantum efficiency,these two bottlenecks hinder the wide application of TiO₂photocatalyst.Modification of TiO₂ to improve its solar energy utilization and quantum efficiency,or the development of more effective new photocatalysts are the major trends in the field of photocatalysis.In order to solve the above problems,one-dimensional TiO₂nanobelt catalyst was prepared by hydrothermal method,and TiO₂ was modified by low concentration H₂SO₄ and BiOBr,which improved its photocatalytic performance and expanded its application range.The main contents of this research include:1)Preparation,acidification modification and photocatalytic properties of TiO₂nanobeltsThe TiO₂ nanobelts were prepared by hydrothermal method and calcination method using commercial P25 as raw material and NaOH as solvent.The effects of preparation conditions such as hydrothermal temperature and acidification modification conditions on the morphology,structure and ultraviolet photocatalytic activity of TiO₂ were investigated.The structure of the catalyst was analyzed by FESEM,TEM and XRD tests.The results show that TiO₂ nanobelts are composed of monoclinic TiO₂-B and anatase TiO₂;hydrothermal temperature and NaOH concentration have great influence on the formation of banded structure of TiO₂;NaOH concentration,hydrothermal temperature and calcination temperature have great influence on the crystalline form of TiO₂;Na⁺can promote the growth of banded structure and monoclinic TiO₂-B crystalline form.The anatase TiO₂ nanoparticle/TiO₂ nanobelt heterojunction catalyst was prepared by acidification of H₂SO₄;EDS analysis shows that S element will not be doped in the acidification modification of H₂SO₄.The photocatalytic experiments show that the decolorization rate of RhB reaches 82.81%and 97.64%respectively,after 100 minutes of ultraviolet light irradiation with TiO₂ nanobelt and acidified modified TiO₂ nanobelt as catalyst.2)Preparation and photocatalytic activity of BiOBr/TiO₂ nanobelt composite catalystsBiOBr/TiO₂ nanobelt composite catalysts were prepared from Bi?NO₃?₃�5H₂O,KBr and acidified modified TiO₂ nanobelts.The effects of preparation conditions such as hydrothermal temperature and reaction conditions such as solution pH on the photocatalytic decolorization of RhB were studied.The morphology,structure and optical properties of the catalysts were analyzed by FESEM,TEM,XRD and UV-Vis DRS tests.The results show that the visible light photocatalytic activity of the BiOBr/TiO₂ nanobelt composite catalyst is the best when the molar ratio of BiOBr to coarsened TiO₂ nanobelt is 2:1,the hydrothermal temperature is 120?and the hydrothermal time is 6 h.The composite catalyst is formed by coupling of lamellar BiOBr adhering to the surface of coarsened TiO₂ nanobelts;the composite of BiOBr and the coarsened TiO₂ nanobelts can narrow the band gap width of TiO₂ and expand its absorption range of visible light.The results of photocatalytic experiments show that the RhB has the best decolorization effect under the condition of the composite catalyst dosage of 0.8 g�L^-1,the initial dye concentration of 20 mg�L^-1 and the initial pH of the solution of 6,and the decolorization rate of RhB reaches 97.52%after 15 minutes of visible light catalytic reaction.The results of mechanism analysis show that superoxide radical?�O₂^-?is the main active species in the visible photocatalytic decolorization process;in the photocatalytic reaction of RhB,the ring-opening oxidation of benzene ring and the deethylation reaction are carried out simultaneously.3)Preparation and photocatalytic activity of BiOBr/TiO₂ heterojunction catalystsBiOBr/TiO₂ heterojunction catalysts were prepared with KOH as alkali solvent.The effect of the ratio of BiOBr and TiO₂ on the visible light catalytic performance of RhB was investigated.The morphology,structure and optical properties of the catalysts were analyzed by FESEM,TEM,XRD,XPS,Mott-Schottky plots,UV-Vis DRS and PL techniques.The results show that the p-n heterojunction is formed at the interface between BiOBr and TiO₂;the heterojunction catalyst is formed by attaching anatase TiO₂nanoparticles to the surface of BiOBr flower spheres.The decolorization rate of RhB is the highest when the molar ratio of TiO₂ to BiOBr is 2:1,the decolorization rate of RhB reaches 96.46%after 15 minutes of visible light catalytic reaction;the decolorization rate of RhB decreased by only 7.94%after four cycles,which indicates that the catalyst has good stability.The results of mechanism analysis show that p-n heterojunction can effectively separate photogenerated electrons and holes;�O₂^-is the main active species in the visible photocatalytic decolorization process;in the photocatalytic reaction of RhB,the ring-opening oxidation of benzene ring and the deethylation reaction are carried out simultaneously.