Preparation And Properties Of WO₃-based Composite Photocatalytic Heterojunction Materials

Major diseases and deaths caused by bacterial infection threaten the survival safety of human beings.The traditional disinfection methods,such as ultraviolet sterilization and chlorine-containing compound sterilization,have disadvantages such as site limitations and easy to produce secondary pollution.Therefore,it is particularly important to develop some efficient antibacterial materials.The green environmental protection technology represented by Ti O₂ in photocatalysis has attracted much attention,and gradually emerged in the field of photocatalysis and antibacterial activity.However,there are some problems,such as low utilization rate of solar energy and easy combination of photoelectron-hole.The development of new and efficient visible light-responsive photocatalytic materials is one of the research hotspots at home and abroad.In this paper,Bi/WO₃ and CN-75/WO₃ composite photocatalytic materials were prepared by coupling tungsten oxide（WO₃）with bismuth（Bi）and p-type carbon nitride（CN-75）,respectively.The composition,morphology,structure,photochemical properties,and photocatalytic antibacterial properties were systematically investigated,and the antibacterial mechanism was speculated through a quenching agent experiment.The optimized powder material was further loaded onto the filter paper to prepare the photocatalytic film and test the antibacterial property of the film material under the actual solar light condition.The main research contents are as follows:（1）The Bi/WO₃ composite photocatalytic materials were synthesized by the hydrothermal method and then by UV reduction.The composition,morphology,structure,and functional groups of the composite were analyzed by XRD,SEM,XPS,and FT-IR,and the results showed that Bi/WO₃ composite could be successfully prepared.i-t curves and EIS results showed that the Bi/WO₃ complex had excellent electron transfer performance.Under visible light irradiation,Bi/WO₃ was used to testing the antibacterial performance of E.coli and S.aureus.The results showed that Bi/W-3 in this system could completely kill E.coli and S.aureus within 90 min,and its antibacterial effect was significantly higher than that of WO₃,Bi/W-3 also had significant effects on E.coli and S.aureus under single-band LED lamp.and the optimal ratio Bi/W-3 was tested for its antibacterial performance under a single wavelength.The active free radicals in the reaction system were detected by ESR technology and combined with the quench agent experiment,revealing the major role of Bi/WO₃complex in the antibacterial process of free radicals.The results showed that O₂·^-and HO·were the main active species in the photocatalytic sterilization process.（2）CN-75/WO₃ composite photocatalytic material was prepared in one step by melamine and triaminopyrimidine as raw materials at high temperature.The composition,structure,and functional group of the composite were characterized by XRD,XPS,FT-IR,UV-Vis DRS,and BET.The results showed that the CN-75/WO₃composite was successfully prepared.I-t curves and EIS results showed that the CN-75/WO₃ complex had excellent electron transfer performance.The antibacterial properties of E.coli and S.aureus were tested under visible light irradiation,and the results showed that CN-75/W-2 in this composite system could completely kill E.coli and S.aureus within 90 min,and its bactericidal effect was significantly better than that of monomer CN-75 and WO₃.Meanwhile,the antibacterial properties of CN-75/WO₃and unmodified CN/WO₃ were compared,which proved that the antibacterial properties were enhanced after modification.After screening the optimal ratio CN-75/WO₃,it was found that the antibacterial effect in the infrared region with a single wavelength was better than that in the ultraviolet region.Finally,the main action of free radicals in the photocatalytic antibacterial process of CN-75/WO₃ complex was revealed by the quench agent experiment,and the results showed that cavitation（h⁺）played a major role in the antibacterial process.（3）The photocatalytic materials Bi/W-3 and CN-75/W-2 prepared in the first two chapters were used to load the powder material onto the filter to make the antibacterial film by simple filtration method,and the antibacterial effect of different kinds of photocatalytic films under the actual sunlight condition was explored.At the same time,the photocatalytic films were used to study the stability and cycling of the photocatalytic antibacterial films.