Nanostructured Titanium Dioxide In Hierarchical Control And Performance Improvement

Photocatalysts play an important role in hydrogen production and photodegradation due to their unique properties.Of these,TiO₂ is a research hotspot in recent decades.However,the photoresponse range of TiO₂ is narrow,it can only absorb visible light,and its quantum efficiency is low.Also,photogenerated electrons and holes tend to recombine during the transfer to the surface.These disadvantages restrict the photocatalytic activity of TiO₂.In particular,defects have an important influence on the electronic structure of the semiconductor material,the spectral absorption and the excitation,migration and recombination processes of the carriers.Among them,oxygen vacancies have strong electron trapping ability,promote the separation of photoelectron holes,and broaden the photoresponse range,which plays an important role in improving photocatalytic activity.Commonly used oxygen vacancies introduced are hydrogen roasting,low-oxygen ambient roasting,and ion sputtering.These methods are complicated and costly.The introduction of oxygen vacancies through direct induction is still a challenge.Based on the above background,the main research content of this paper is:（1）The oxygen vacancies were introduced into the already synthesized macro/mesoporous TiO₂ by means of fluorine induction,and oxygen vacancy defects were introduced into the hierarchical structure material.The presence of oxygen vacancies was demonstrated by electron paramagnetic resonance and the effects of oxygen vacancies on the band gap and carrier recombination were explored.At the same time,the macroporous mesoporous structure of the synthesized sample is conducive to enhancing the mass transfer and increasing the specific surface area.The photocatalytic activity of the macroporous mesoporous TiO₂ with oxygen vacancies was investigated by liquid phase degradation of methylene blue and gas phase degradation of acetone.（2）Oxygen vacancies are further introduced into the TiO₂ hollow microspheres by fluorine induction.The commonly used TiO₂ microspheres were selected as the modal structure and formed a hollow structure after hydrothermal treatment.With the introduction of oxygen vacancies,the band gap of TiO₂ decreases,the probability of recombination of photoelectrons and holes decreases,and the photocatalytic activity increases.（3）This thesis further in-situ synthesis of MoS₂@TiO₂ composites with oxygen vacancies by hydrothermal method.The protonated titanate nanosheets were used as TiO₂ precursors to introduce oxygen vacancies during the hydrothermal conversion.Oxygen vacancy enhances the carrier’s transmission efficiency,improves the photocatalytic activity of MoS2@TiO2,and is also conducive to the improvement of its electrocatalytic hydrogen evolution performance.