Study On The Carrier Separation Efficiency And Photocatalytic Performance Of TiO₂ Enhanced By Internal And External Electric Fields

After antibiotics are produced and used,they are discharged into the natural environment,directly or indirectly harming human health.Photocatalysis is a mild advanced oxidation-reduction technology that can effectively remove water pollutants.Among them,the photocatalyst TiO₂ has been extensively studied and gradually commercialize.However,due to the wide band gap of TiO ₂ and the high probability of intrinsic photogenerated carriers recombination,practical applications are limited.In this paper,we choose ultra-thin TiO₂ nanosheets with high exposure（001）crystal plane as the research object,modify its shortcomings,and conduct a detailed study on its internal mechanism.The specific content is as follows:（1）Preparation of ultra-thin nanosheets with high exposure（001）crystal plane Fe-doped TiO₂（FTF）by hydrothermal method,which broadens the light absorption range of TiO₂ and increases its specific surface area.In-situ XPS results show that Fe³⁺is the photo-generated electron capture site.Through ESR,O₂ TPD,and CV tests,it can be seen that the captured photo-generated electrons are quickly transferred to O ₂to form^·O₂^-.In addition,Fe³⁺doping causes oxygen defects（O_D）on the surface of the sample.According to DFT,ESR,photo-generated hole injection efficiency and other tests,it can be seen that O_D generation is more conducive to water adsorption and activation,thereby strengthening the photo-generated holes and water.Interaction to produce more^·OH.Therefore,while Fe³⁺doping generates an internal electric field inside the crystal,it also realizes the capture of photogenerated electrons and the simultaneous consumption of photogenerated holes,so that FTF samples have greater photocurrent density,lower interface resistance and higher light.Catalytic activity.（2）On the basis of the previous chapter,composite FTF and Ag loaded TiO₂（FTA）ultra-thin nanosheets to obtain FTF/FTA composite photocatalytic material.It can be seen from the structural characterization of FTF/FTA that the two kinds of TiO ₂ ultra-thin nanosheets are recombined in a face-to-face manner,thereby providing a larger separation channel for carrier transport.XPS results show that there is a built-in electric field（IEF）directed from FTF to FTA in the FTF/FTA system,and an external electric field is constructed on the basis of the internal electric field of the FTF to further transmit and separate photo-generated carriers.According to SPV,Zeta potential,VB XPS,DRS,free radical capture experiments,etc,the photogenerated carriers are transported and separated in a Z-shaped manner on FTF/FTA,which maximizes the retention of the system’s redox potential while simultaneously reducing the photogenerated carriers.Carriers are separated to the maximum extent.Therefore,in the photocatalytic degradation process,FTF/FTA exhibits higher catalytic activity than FTF and FTA.（3）Carry out the actual water purification simulation test on the combined photocatalyst,and use PMS to eliminate the negative influence of the complex components in the actual water body on the photocatalytic water purification process.The study found that under the applied light source,in 25 mg/L CIP municipal wastewater（MW）,when 0.7 g/L PMS and 0.3 g/L FTF/FTA were added,the optimal photodegradation effect was achieved.The MW-FTF/FTA-PMS system shows excellent photodegradation activity for different antibiotics and dyes.After analysis,it can be known that after adding PMS,there is a synergistic effect of free radical-activated active substances and non-radical-activated active substances in the system.Therefore,the adverse effects of complex components in MW can be effectively offset.Finally,TOC and GC-MS were used to analyze the degradation process of antibiotic CIP and dye Rh B in MW,which provided theoretical data for the practical application of photocatalytic technology.