Nano-Fe⁰ Modification And Crystal Facets Optimization Of TiO₂ Photocatalysts And The Regulation Of Redox Properties

In order to extend spectral response range of TiO₂ and promote the separation of photogenerated electron-hole,enhance its photocatalytic activity.TiO₂/nano-Fe⁰photocatalysts,anatase TiO₂ single crystals and mesoporous-?001?facets TiO₂ single crystals were synthesized in this work through two aspects of the modification of the external auxiliary coordination and the control of the structural morphology?crystal facet?.Their crystal structure,morphology and specific surface area were characterized by XRD,SEM,TEM,XPS,EDX,UV-vis DRS and specific surface area analytical instrument.And,the redox catalytic properties of the photocatalysts were also studied.The main research contents are as follows:1.TiO₂/nano-Fe⁰ photocatalysts were synthesized via a liquid phase reduction method.The results showed that this composite photocatalyst forms a jellyfish morphology and heterojunction structure.The composite of nano-Fe⁰ and TiO₂ could effectively compensate the consumption of nano-Fe⁰ and promote the generation of hydroxyl radicals?·OH?by a synergistic effect.Furthermore,the formation of a heterojunction structure not only makes this composite photocatalyst have a higher catalytic efficiency in the visible region by the photo-response redshift effect,but also blocks the recombination of the photogenerated electron–hole pairs.Besides,the synergistic effect and the dynamic circulation reaction mechanism of TiO₂/nano-Fe⁰photocatalysts were also investigated.This composite photocatalyst possessed the highest photocatalytic activity for Acid Red B under acidic and aerobic conditions with the optimal loading of 10 wt%nano-Fe⁰.The photocatalytic degradation activity of acid red B was 1.3 times that of P25.2.Anatase Ti O₂ single crystals were synthesized through a solvothermal route using hydrofluoric acid as a morphology controlling agent.The exposure ratio of?001?facets could be regulated by adding adjust the amount of hydrofluoric acid in the reaction system.In the synthesis process,the surface hydroxylation and substitution effect will make the?001?facets easy to be corroded.Hydrofluoric acid can not only accelerate the nucleation of single crystal,increase the size of crystal,but also promote the growth of?001?surface.The photocatalytic activity of TiO₂ single crystal with 30%and 60%?001?facets were evaluated by hydroxyl radical?·OH?and reducing nitro method.The photocatalytic activity of TiO₂ single crystal is 4-5 times of anatase TiO₂ nanocrystals due to the crystal facet effect and high activity?001?facets.And,in the photocatalytic reaction,the?001?facets possess strong oxidation property,while the?101?facets with reducibility.3.Mesoporous-?001?facets TiO₂ single crystals were synthesized through a two-step solvothermal route without any template.It belongs to anatase,and its?001?facets have a mesoporous structure,?100?and?010?facets were covered by the flower–shaped Ti O₂ crystals.This special and interesting structure can effectively increase the specific surface area and greatly promote the transfer of photogenerated electron-hole,and provides more active sites for improving the photocatalytic activity.The photocatalytic degradation activity of rhodamine B was twice that of anatase TiO₂single crystals.Furthermore,the synthesis mechanism of mesoporous-?001?TiO₂single crystals was studied based on the characteristics of preparation process and crystal structure.4.The anatase TiO₂ single crystals with?001?and?101?facets were used as the photocatalyst,and the 3,4-dichloronitrobenzene was used as the target substrate.The study on the integration of oxidation and reduction by adjusting the conditions of photocatalytic reaction.In the photocatalytic reaction system,the characteristic of the solvent?methanol/water?can play a decisive role in the photocatalytic oxidation and reduction reaction.When the proportion of water in the solvent is large,the photocatalytic oxidation is dominant,the 3,4-dichloronitrobenzene and the product3,4-dichloroaniline can be simultaneously oxidized and degraded.