Comprehensive experiment design of the photocatalytic degradation of organic dyes by ZnO1-xSx heterojunctions
[Objective]Comprehensive chemistry experiments play a crucial role in cultivating undergraduate chemistry majors'scientific innovation thinking and comprehensive practical abilities,which has become a key focus of experimental teaching reform.To improve the high-order nature of comprehensive chemistry experiments,universities have extensively implemented and strongly advocated the teaching model of science and education integration in recent years.Comprehensive chemistry experiments characterized by innovation and exploration have been offered based on professional training objectives,cutting-edge research hotspots,and teacher's research projects.Semiconductor photocatalysis technology is an ideal way to solve the energy and environmental crises facing the world today,which has become one of the hot research fields.Introducing the innovative training project integrating the preparation,characterization,and performance testing of photocatalysts into undergraduate teaching is of great significance for cultivating independent,innovative talents and developing energy and environmental catalysis.Herein,a comprehensive chemistry experiment entitled"photocatalytic degradation of organic dyes by ZnO1-xSx heterojunctions"was designed for science and education integration based on cutting-edge research hotspots in energy and environmental catalysis.[Method]In this comprehensive experiment,ZnO nanoparticles were prepared by a facile hydrothermal route using zinc chloride and sodium hydroxide as source materials.Then,ZnO1-xSx heterojunctions with a controllable component ratio were constructed via an in-situ sulfurization strategy using the as-prepared ZnO nanoparticles as the substrate and thioacetamide as the sulfur source.The structure,morphology,and optical properties of ZnO,ZnS,and ZnO1-xSx heterojunctions were characterized by X-ray diffraction patterns,scanning electron microscope images and ultraviolet-visible diffuse reflection spectra.The photocatalytic performance of ZnO1-xSx heterojunctions was measured using methyl orange dye as the organic pollutant model under simulated sunlight irradiation.[Results]The results reveal that ZnO1-xSx heterojunctions are a hollow structure with a wider light absorption wavelength range,higher visible light utilization efficiency,and significantly enhanced photocatalytic performance compared with pure ZnO and ZnS.Meanwhile,the photocatalytic performance of the ZnO1-xSx heterojunctions increases first and then decreases as the molar ratio of[ZnS]to[ZnO]increases.When the molar ratio of[ZnS]to[ZnO]is 6:4,the optimal photocatalytic degradation efficiency is achieved.Furthermore,the trapping experiments suggest that photogenerated holes and hydroxyl radicals are the main active species during the photocatalytic reactions.The photocatalytic mechanism and carrier transfer pathway of the ZnO1-xSx heterojunctions were demonstrated to be a type-Ⅱmodel.[Conclusions]This comprehensive chemistry experiment simulates the entire scientific research process,focusing on hydrothermal synthesis,structure/morphology characterization,performance testing,and data analysis of ZnO1-xSx heterojunction photocatalysts.By participating in experimental research,students can independently explore the influence of the component ratio of the ZnO1-xSx heterojunction on its structure,optical properties,and photocatalytic performance and preliminarily infer the transfer path of photogeneration carriers at the heterojunction interface.This experiment project can train students'understanding and comprehensive application of the knowledge from multiple chemistry disciplines,which helps cultivate students'independent innovation awareness,practical application ability,and critical thinking,thereby improving undergraduate teaching quality and promoting the integration of science and education.
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