The Construction Of Cu-based Oxide Heterojunction And Its Photocatalytic Performance

Energy is the most basic driving force for the development of the entire world and economic growth,and it is the foundation on which human beings depend.While mankind enjoys the benefits of economic development and technological progress brought about by energy,it also encounters a series of unavoidable energy crises.The excessive use of energy has caused energy shortages and environmental pollution,which threaten human survival and development.As the energy crisis is approaching,new energy has become one of the world's major energy sources.Solar energy is an inexhaustible healthy energy for the earth,and it is bound to become the mainstay of new energy.Semiconductor materials can be used as a medium to convert solar energy into chemical energy,such as using solar power to generate electricity,degrade organic pollutants,and synthesize important organic substances.Cu₂O is one of the basic semiconductor materials to realize this process,but the photocorrosion phenomenon of Cu₂O under light and the single Cu₂O electron-hole pairs cannot be effectively separated,which seriously hinders its development in the field of photocatalysis.Therefore,we hope to utilize Cu₂O and other semiconductor materials to build heterojunctions to change its electronic structure and improve its stability and photocatalytic performance.1.The Cu₂O hexapetalous flowers were obtained through hydrothermal procedure,and then Cu S in-situ grew on Cu₂O to form core-shell structure by CVD,which effectively inhibited the photocorrosion of Cu₂O.Meanwhile,Cu₂O@Cu S core-shell structure could extend the light absorption range to 1500 nm;promote the separation of electrons and holes in photocatalytic system.Thus,under the wide-spectral region,Cu₂O@Cu S exhibited excellent photocatalytic performance for the degradation of tetracycline with 91%degradation rate and had good cycling ability,resulting from the effective separation of photogenerated charges,more free radicals generated such as·OH and·O₂^-,and increases of utilization rate of visible-light.These results indicate that in-situ surface deposition Cu S strategy is an effective method to improve visible-light photocatalytic activity and stability of Cu₂O.2.The supramolecular precursor based on the melamine was obtained through the hydrothermal reaction,and copper oxide was synchronously modified on its surface.After heat treatment at 400?,supramolecular precursor transformed into C₃N₄ tube.Meanwhile,due to the thermal reduction and N-source from the pyrolysis of supramolecular,copper oxide turned into Cu/Cu₂O/Cu₃N.The Cu/Cu₂O/Cu₃N@C₃N₄ tube composite was subjected to photocatalytic oxidative self-coupling reaction at low temperature?323 K?in air.Due to the effective separation of electron and hole pairs and the oxidative free radicals?such as·OH and·O₂^-?were generated by the catalyst under visible-light irradiation converted benzylamine to imine.Therefore,the photocatalyst could achieve high conversion and selectivity of 99%and 98%,respectively for benzylamine coupling.The presence of Cu and Cu₃N also accelerated electron and hole transfer,resulting in improved oxidation efficiency.Hence,the synthesized Cu/Cu₂O/Cu₃N on C₃N₄tube is a feasible catalyst for effective photocatalytic oxidative coupling of benzylamine.3.Cu₂O cubes with special crystal planes were grown in situ on the C₃N₄tube by a wet chemical method,and a Cu₂O/C₃N₄heterojunction was obtained.The stability of Cu₂O is improved by using the high stable?100?crystal plane of cubic Cu₂O,and the photocatalytic action of C₃N₄is used to jointly promote the photocatalytic activity.Cu₂O nanoparticles with special crystal planes are smaller in size?about 300 nm?and have a larger specific surface area.At the same time,the specific surface area of the Cu₂O/C₃N₄composite is increased(275 m²g^-1),which makes it more active substances.Therefore,the heterojunction constructed by Cu₂O with special crystal planes and C₃N₄can also effectively enhance the separation and migration of photo-generated carriers,thereby improving photocatalytic activity.The degradation rate of Cu₂O/C₃N₄composites in photocatalytic degradation of tetracycline is as high as 98%,and it accords with first-order kinetics.