Construction Of TiO₂ Active Surface,Band Gap Modulation And Photocatalytic Performance

In recent years,the proposal of carbon neutrality makes photocatalytic technology using solar energy the focus of scientific research.Among a wide variety of photocatalysts,titanium dioxide（TiO₂）has received extensive attention due to its advantages of low toxicity and chemical stability.However,the large band gap of TiO₂makes the visible-light utilization low,which restricts the practical development of TiO₂materials to a certain extent.Aiming at narrowing the band gap,realizing visible-light response and constructing an active surface,this thesis takes TiO₂as the research object to improve photocatalytic performance of TiO₂through doping,defect control and heterostructure construction.The main researches are as follows:（1）The ultra-small TiO₂（～5 nm）is prepared by sol-gel method,and then a plasma-induced（PIT）technology is adopted to achieve a binary core-shell structure containing surface continuous defect layer of oxygen vacancy and crystallized TiO₂core.The outstanding photocatalytic activity of carbon-doped TiO₂with a continuous oxygen-deficient layer（OV-TiO₂@C）for visible-light-driven degradation of Rh B and MO originates from narrowed band gap（～2.30 e V）and improved photo-induced charge separation.Moreover,the degradation efficiency of Rh B could reach to 100%even in a wide p H range（3.0-11.0）.Furthermore,the synergistic effect by surface oxygen-vacancies layer and interstitial carbon doping significantly enhances the photoelectrochemical（PEC）performances significantly.Combined with liquid chromatography-mass spectrometry（LC/MS）and the total organic carbon（TOC）tests,it confirms that the photodegradation process over Rh B contains N-de-ethylation,chromophore cleavage and mineralization to finally H₂O and CO₂under the action of·O₂^-and h⁺.（2）Al₂O₃ is deposited on the surface of OV-TiO₂@C by atomic layer deposition（ALD）technology,and its enhanced photocatalytic performance is studied.The mesoporous structure of the composite photocatalyst increases the specific surface area（515.949 m~2/g）,providing a larger contact area for pollutants.Furthermore,the composite obtained by Al₂O₃deposition at 180℃ shows optimal photocatalytic activity,which can absorb 88%of Rh B after 20 min in the dark condition and achieve 100%decolorization of Rh B after 12 min under the visible-light irradiation.Excellent catalytic activity is maintained after 4 cycles of Rh B degradation（100%）.Even at a relatively low dosages（0.25 g/L）,in a wide p H range（3.0-11.0）and an environment with 5-fold increased concentration of Rh B,100%Rh B degradation can be achieved in a short time.Since the amorphous Al₂O₃with the porous structure is favorable for electron transport to the surface to participate in the catalytic reaction,the separation and mobility of photogenerated carriers are improved to significantly enhance the PEC performance.In conclusion,in-situ carbon doping and defect-engineering jointly improve the photocatalytic performance of the ultra-small TiO₂,which can effectively narrow the band gap and realize visible-light response.The disordered Al₂O₃layer effectively passivates recombination centers on the surface of OV-TiO₂@C and enhances the photocatalytic adsorption and activation reactions on the surface.