The Controllable Synthesis Of TiO₂ Nanomaterials And The Research Of Its Photocatalytic Performance

In recent years,TiO₂ based photocatalyst has been widely used in pollutant degradation,artificial photosynthesis and hydrogen evolution due to its excellent stability,low price,non-toxic,etc.In spite of that,some inherent factors considerably restrict its further applications.The large bandgap?3.0-3.3 eV?determines that TiO₂ can only absorb UV photons which occupy a small part of sunlight?4%?,while cannot make use of visible light?40%of sunlight?.Meanwhile,the fast recombination rate of photogenerated carries makes it impossible for electrons and holes to migrate to the surface of TiO₂ and participate in photocatalytic reactions.In order to improve its performance,a series of modifications have been made in this work.The results of the research are summarized as follows.1.We report a facile and economical photoassisted strategy for synthesizing the highly active N,F-codoped oxygen-deficient based TiO₂ with coexposed{001}and{101}facets.NH₄TiOF₃ mesocrystals were used to be the resource of dopants and the intermediate to fabricate TiO₂ with highly active{001}facets.Comprehensive analysis based on X-ray photoelectron spectroscopy,transmission electron microscopy and electron spin resonances manifested that F,N and oxygen vacancies were simultaneously introduced to TiO₂ through the photoassisted process.The test of phenol and Rhodamine B?RhB?degradation under visible light demonstrates that the as-prepared N,F codoped oxygen-deficient TiO₂ exhibits higher photocatalytic activity than its references.The increased photocatalytic performances results from the synergetic effect of the induced Vo's and N,F codoping in TiO₂ with co-exposed{001}and{101}facets,favoring the visible light utilization as well as the separation of photogenerated carriers.2.The morphology of photocatalytic materials has a very important impact on its performance.Herein,based on the previous work,we mainly designed and synthesized defect-engineered N,F-doped well-defined TiO₂ hollow spiny nancubes,constructed from NH₄TiOF₃ as precursor.The topological transformation of NH₄TiOF₃ mesocrystal to TiO₂ was carried out in H₃BO₃ solution,accompanying with F and N ions releasing,which can be used as doping source.The characterization results show that hollow structure was assembled from many small{001}facet dominated TiO₂ nanosheets based on a certain direction.Photo-assisted reduction strategy facilitated the introduction of oxygen vacancies and dopants into TiO₂,which greatly improve the photodegradation of phenol and Rh B as well as its PEC performance under visible light illumination.The enhanced performance of TiO₂ mainly due to the following reasons,?1?the formation of defect energy levels narrow the band gap of TiO₂ by the existence of Vo's,enhancing its visible-light absorption ability,?2?the multi-reflections of incident light was achieved in the hollow spiny structure,which enables TiO₂ to make full use of incident light,?3?the improvement of electrons and holes separation efficiency synergistically made by Vo's,F^-doping as well as the unique hollow architectures.