Synthesis And Photocatalytic Degradation Performance Of CdIn₂S₄ And Its Composite

With the speedy progress of the medical and pharmaceutical industries,antibiotics have become a new type of water pollutant,both the ecological environment and health of human beings have been seriously threatened.It is imminent to develop efficient pollution treatment strategies.Semiconductor photocatalysis has shown great development prospects in the field of environmental remediation by virtue of its green and efficiency.However,the vast majority of current semiconductor photocatalysts are still constrained by problems such as limited photoresponse range,grave carrier recombination,poor quantum efficiency,and insufficient stability,leading to unsatisfactory photocatalytic efficiency.Hence,the design and synthesis of high-performance photocatalysts are of exceeding significance.The ternary metal sulfide CdIn₂S₄ has good visible light response and is considered to be a photocatalyst with great application potential.However,the easy recombination of photogenerated carriers seriously affects its photocatalytic performance.On the ground of above problems,focusing on the performance optimization of CdIn₂S₄ photocatalyst and its application in environmental remediation,the main work of this paper is carried out from the following two aspects:（1）Targeting metal-organic framework materials as a template,the CdIn₂S₄ with a hollow structure was designed and fabricated.The light absorption ability and carrier separation performance of the material were improved by means of morphology control,so as to achieve efficient antibiotic degradation.（2）A CdIn₂S₄/WO₃ heterojunction system was constructed,and the effective separation of electron-hole pairs was realized through a Z-scheme electron transfer mechanism,which improved the photocatalytic degradation performance.The main content of the thesis is elaborated from the following parts:This paper first briefly presents the hazards of antibiotic-containing wastewater and summarizes the common wastewater treatment methods.The development history and the fundamentals of semiconductor photocatalysis technology are introduced,and the typically used strategies for catalyst modification are outlined.In addition,the development status and the existing synthetic methods of hollow structures are briefly summarized,which provides new ideas for the optimization of catalyst performance.Our work starts with the morphology control of the catalysts.Using the iron-based metal-organic framework MIL-88A as a template,we successfully designed and synthesized hollow CdIn₂S₄ with a unique spindle shape and apply it to visible-light-driven photocatalytic degradation of tetracycline（TC）.Simultaneously with the growth of CdIn₂S₄,the template can be etched by S^2-,eliminating the time-consuming template removal step in the traditional hard template method.Thus,this synthesis route is simple and convenient.The experimental results showed that the spindle-like hollow CdIn₂S₄has better tetracycline degradation activity than the sample synthesized under no-template conditions.This is benefited from its unique hollow structure,which enhances the light absorption capacity and improves the separation and transport performance of photogenerated carriers.Secondly,from the perspective of constructing semiconductor heterojunctions,a series of CdIn₂S₄/WO₃ heterojunctions with different ratios were prepared by in-situ growth method.A series of characterization results confirmed the formation of close interfacial contact between CdIn₂S₄ and WO₃,and the system is conformed to be Z-scheme heterojunction.Through the Z-scheme charge transfer mechanism,the efficient separation of photogenerated carriers is achieved,thus the heterojunction system exhibits enhanced photocatalytic activity for tetracycline degradation compared with pure CdIn₂S₄ and WO₃.At the same time,compared with pure CdIn₂S₄,the CdIn₂S₄/WO₃ system showed better photochemical stability,and the photocorrosion phenomenon was improved.In the end,we summed up all the research outcomes in this thesis and analyzed the current status and development tendency of photocatalysis.Moreover,we put forward new prospects for the future development of photocatalytic technology.