Preparation And Characterization Of Novel Photothermal Catalyst

Catalytic technology has broad application prospects in environmental purification.In recent years,photocatalysis,thermal catalysis and photoelectric catalysis have brought far-reaching influence on the degradation of pollutants.Among them,photocatalytic degradation of pollutants is a hot area of research,which uses light generated electron holes to decompose organic pollutants at room temperature to decompose organic matter into inorganic substances,such as CO₂ and H₂O.Semiconductor photocatalyst has the advantages of stable chemical properties,low cost and high recovery rate,which is an effective solution to environmental problems,but researchers still face difficulties and challenges at present.One challenge is the low quantum efficiency of photocatalysts due to the rapid binding of photogenerated electrons and holes in REDOX reactions.Another challenge is that during catalytic reactions,intermediate products that are difficult to degrade can sometimes be precipitated to cover the active sites on the surface of the material,preventing further adsorption of the reactants and thus reducing catalytic activity.In this study,we synthesized photocatalysts with abundant defects and large specific surface area,and studied the photothermal catalytic performance.In the degradation of gaseous organic pollutants,photothermal synergistic catalysis is shown.It is believed that this study will promote the application of semiconductor photocatalysis in air purification.1.Photothermal co-catalytic degradation of gaseous organic pollutants by ZnFe₂O₄ rich in oxygen vacancy.Zinc ferrite（ZnFe₂O₄）is an inorganic material with good properties,which is famous for its excellent soft magnetic properties.With stable chemical properties and high sensitivity to visible light,it is an excellent photocatalytic material,which has also attracted the attention of researchers.ZnFe₂O₄ with large specific surface area and oxygen-rich vacancy was prepared by sol-gel method by dissolving iron nitrate 9hydrate and zinc acetate dihydrate in a certain amount of deionized water,stirring,drying and calcining.Through the characterization test of ZnFe₂O₄,XRD proves that the sample has been successfully synthesized.By TG-DSC analysis,it can be concluded that the precursor has been completely transformed into high stability and high crystallization ZnFe₂O₄ at 400℃,indicating that when the calcination temperature reaches 400℃,ZnFe₂O₄ has been fully grown and has good crystallinity.Based on the analysis of N₂ adsorption-desorption curves,the sample prepared has a large specific surface area,with a maximum specific surface area of 56.4 m²g^-1.The results of UV-Vis diffuse reflectance spectra and EPR show that the synthesized samples have abundant oxygen vacancies.In the characterization of photocatalytic activity,ZnFe₂O₄-400 with large specific surface area and oxygen vacancy has a higher catalytic activity in degrading gaseous organic pollutants,which is 23.4 times higher than that of ZnFe₂O₄-700.The high activity of the sample is the result of the large specific surface area and oxygen vacancy,which can increase the adsorption site between the catalyst surface and contaminants.The oxygen vacancy can change the electronic structure of the material,reduce the energy of electron transition,promote the separation of electrons and holes,and improve the catalytic activity.2.Photothermal catalytic performance of highly active Cr₂O₃/CeO₂ composites.Cr₂O₃/CeO₂ photocatalytic materials with high activity were prepared by mixing,drying and calcining Cr₂O₃/CeO₂ with chromium nitrate nine water and cerium nitrate six water as precursors,dissolved in certain amount of deionized water.The results of XRD and SEM analysis show that Cr₂O₃ and CeO₂ have been successfully combined.According to the N₂ adsorption-desorption curve,the composite sample has a large specific surface area,with the maximum specific surface area reaching 85.196 m²g^-1.UV-Vis diffuse reflectance spectra showed that the light absorption capacity of the composite samples was enhanced.XPS indicated that Cr₂O₃/CeO₂ contained oxygen vacancy.Since Cr₂O₃ is p-type semiconductor material and CeO₂ is n-type semiconductor material,the formation of heterojunction at the interface between p-type and n-type semiconductor materials can effectively inhibit the recombination of carriers generated by photo excitation,thus improving the photo catalytic activity.Under the experimental conditions,the photo catalytic capacity of isopropanol was evaluated through the degradation of gaseous organic pollutants.From the characterization results,it can be seen that the activity of the composite material prepared is higher than that of pure CeO₂ and Cr₂O₃.Therefore,the Cr₂O₃/CeO₂ photocatalyst prepared in this experiment can effectively degrade gaseous organic pollutants,which improves a new method for the preparation of low-cost and high activity photocatalyst.