Fabrication And Catalytic Performance Of Three-Dimensional Micro-Nano Structure Heterojunction Visible Light Catalysts

With the development of society and economy,antibiotics are widely used in human health,animal husbandry and aquaculture.A large amount of antibiotics are discharged into natural water bodies through excreta and waste water,causing serious pollution to the environment and remaining in nature.Antibiotics in the water enter the human body along with the food chain,damaging people's health.Therefore,it is very urgent and necessary to find an efficient and environmentally friendly method for removing antibiotics.Light/photoelectrocatalytic technology is an emerging new degradation technology with rapid potential,high efficiency and environmental protection.In this paper,three-dimensional peony-like CoO@?-Bi₂O₃ Z-type heterojunction materials,three-dimensional hollow sphere V₂O₅@Ni₃V₂O₈heterojunction materials and three-dimensional massive CoFe₂O₄@ZnFe₂O₄heterojunction materials were designed and prepared.Three materials were used for photo/photoelectrocatalytic degradation of tetracycline antibiotics.The main research contents of this paper are as follows:Three-dimensional graded peony-like CoO@?-Bi₂O₃ Z-type semiconductor heterojunction was successfully prepared.The three-dimensionally graded flower-like morphology facilitates the absorption of incident light on the surface and inside of the material through multiple reflections and scattering,improving the absorption of visible light by the catalyst.The unique flower-like morphology has a large specific surface area and is exposed to abundant activity.The site is beneficial to improve the catalytic performance of the catalyst.The formation of the Z-type p-n junction not only effectively suppresses the recombination of photogenerated electron-hole pairs,but also preserves the outstanding oxidizing ability of the semiconductor material.The photocatalytic performance of CoO@?-Bi₂O₃ was studied by photocatalytic degradation experiments of tetracycline?TC?,chlortetracycline?CTC?and oxytetracycline?OTC?under visible light irradiation.The experimental results show that the degradation efficiencies of TC,CTC and OTC are 86%,84.6%and 85.9%,respectively,within 120 minutes.The removal rate of TOC in the solution reached70%by the determination of organic carbon content,which proved that the CoO@?-Bi₂O₃ Z-type semiconductor heterojunction has strong photocatalytic degradation effect on tetracycline antibiotics.In addition,after four cycles of experiments,the photocatalytic degradation rate of tetracycline antibiotics is not less than 80%,indicating that the material has good stability.Through the hole and free radical trap experiments,combined with the Mott-Schottky test,it is proved that a Z-type p-n junction is formed between CoO and?-Bi₂O₃,and the photocatalytic degradation mechanism is discussed in detail.Three-dimensional hollow spherical V₂O₅@Ni₃V₂O₈ S-type semiconductor heterojunction was successfully prepared,and the V₂O₅ nanoparticles were grown in situ on the hollow spherical Ni₃V₂O₈ surface by a simple one-step hydrothermal method.The three-dimensional hollow structure is beneficial for the incident light to be absorbed by multiple reflections and scattering inside the material,thereby improving the absorption capacity of the catalyst for visible light.The unique hollow structure has a large specific surface area and is exposed to abundant active sites,which is beneficial to improving the catalyst.The formation of the S-type heterojunction can effectively suppress the recombination of photogenerated electron-hole pairs.The photocatalytic performance of V₂O₅@Ni₃V₂O₈ was studied by photocatalytic degradation experiments of TC and OTC under visible light irradiation.The experimental results show that the degradation efficiencies of TC and OTC reach 80.2%and 69.4%,respectively,within 120 minutes.In addition,after four cycles of experiments,V₂O₅@Ni₃V₂O₈ still showed excellent catalytic effect,indicating that the material has good stability.Through the hole and free radical trap experiments,combined with the Mott-Schottky test,it is proved that an S-type heterojunction is formed between V₂O₅ and Ni₃V₂O₈,and the photocatalytic degradation mechanism is discussed in detail.Three-dimensionalbulkCoFe₂O₄@ZnFe₂O₄S-typesemiconductor heterojunction was successfully prepared.The rough surface structure enhances the absorption of visible light by the catalyst and exposes the active site,which is beneficial to improve the catalytic performance of the catalyst.The formation of the S-type heterojunction can effectively suppress the recombination of photogenerated electron-hole pairs.The photoelectrocatalytic properties of CoFe₂O₄@ZnFe₂O₄ were investigated by photoelectrocatalytic degradation experiments of TC and CTC under externally applied bias voltage of 0.8V.The experimental results show that the photocatalytic degradation efficiencies of TC and CTC are 79%and 70.4%,respectively,within 120 minutes.In order to further explore the properties of CoFe₂O₄@ZnFe₂O₄,the photocatalytic,electrocatalytic and photoelectrocatalytic reactions of tetracycline were carried out,and CoFe₂O₄@ZnFe₂O₄ showed the best catalytic performance.Compared with the photocatalytic oxidation reaction,the photocatalytic oxidation efficiency of CoFe₂O₄@ZnFe₂O₄ is improved by the forced transfer of photogenerated electrons to the photoanode in the presence of an applied bias voltage,so that the photogenerated carriers are more effectively separated.For electrocatalysis,it is due to the presence of visible light.In addition,after four cycles of experiments,CoFe₂O₄@ZnFe₂O₄ still showed excellent catalytic effect,indicating that the material has good stability.Through the hole and radical trapping experiments,combined with the Mott-Schottky test,it was proved that an S-type heterojunction was formed between CoFe₂O₄ and ZnFe₂O₄,and the photocatalytic degradation mechanism was discussed in detail.