Preparation,Characterization Of NiCo₂O₄ Based Nanocomposites And Their Application In Organic Pollutants Degradation

The environmental and energy crisis,which caused by the burgeoning development of industrialization and urbanization,have garnered widespread attention in many years.Currently,photocatalysis is accounted as a crucial technology to relieve the above two problems,and aroused the interest of scientists and scholars.In order to enhance the photocatalytic efficiency,researchers are on a constant search for novel semiconductor materials.Among many semiconductor materials,NiCo₂O₄ can be severed as one of the representative candidates for photocatalysis due to its unique electronic structure,narrow band gap,and visible light response.However,the low photo-generated electron-hole pair separation efficiency has significantly restricted its research in the field of photocatalysis.Therefore,NiCo₂O₄ can be expanded to apply in the field of photocatalysis through reducing the recombination of photo-generated electron-hole pairs or changing the transfer path of photo-generated carriers.In this thesis,the NiCo₂O₄/BiOCl,CdS/NiCo₂O₄ and Zn_0.5Cd_0.5S/NiCo₂O₄ composites are prepared successfully,and characterized by a series of testing techniques to analyze their morphology,structure,and specific surface area.In addition,the photoelectric properties of CdS/NiCo₂O₄ and Zn_0.5Cd_0.5S/NiCo₂O₄ are analyzed by photoluminescence,transient photocurrent response,and electrochemical impedance?EIS?.The catalytic performance of the as-obtained composites is further researched.The main contents are as follows:1.The NiCo₂O₄/BiOCl composites are synthesized by three steps:hydrothermal,reflux and calcination.The as-synthesized material is used to catalytic reduction of4-nitrophenol and organic dyes?Rhodamine B,Congo red,Rhodamine 6G and Methyl orange?.Experimental results reveal that the catalytic reduction performance of the composites is more excellent than that of pure NiCo₂O₄ and BiOCl,and the catalytic reaction rate attains to 7.18×10^-33 s^-1.By recycling catalytic reduction of TC-HCl for seven times,the stability of NiCo₂O₄/BiOCl was evaluated.The results indicating that the NiCo₂O₄/BiOCl possesses excellent stability and reusability.At the same time,the degradation mechanism of organic contaminants?4-NP,Rhodamine B,Congo red,Rhodamine 6G and Methyl orange?and its application in practical environment are also studied.2.The NiCo₂O₄ substrate was prepared by two simple steps of reflux and calcination.Then,different percentage contents of CdS nanoparticles are decorated on the NiCo₂O₄nanosheets by a simple hydrothermal method.The photocatalytic performances of CdS/NiCo₂O₄ with different percentages of CdS for hexavalent chromium and tetracycline hydrochloride degradation were evaluated under the irradiation of visible light.The results indicate that the 60%CdS/NiCo₂O₄ exhibits the best photocatalytic performance.The free radical experiment confirms the formation of a Z-type heterojunction between the interface of NiCo₂O₄ and CdS,which further revealed that the recombination of electron-hole pairs is reduced,and the photocarrier transfer is speeded.3.The ternary Zn_0.5Cd_0.5S nanoparticles are loaded on NiCo₂O₄ nanosheets through water bath method.The photocatalytic action of Zn_0.5Cd_0.5S/NiCo₂O₄ composite is evaluated by the photocatalytic degradation of tetracycline hydrochloride.Comparative experiments were conducted among a series of Zn_0.5Cd_0.5S/NiCo₂O₄?X=30,40,50,60,70,0?,and the results show that the photocatalytic degradation efficiency of 60%Zn_0.5Cd_0.5S/NiCo₂O₄ is better than that of X%Zn_0.5Cd_0.5S/NiCo₂O₄?X=30,40,50,70,0?.Moreover,the degradation efficiency of 60%Zn_0.5Cd_0.5S/NiCo₂O₄ for tetracycline hydrochloride was almost unchanged even for three cycles.The free-radical capture experiment further illustrates the formation of a Z-type heterojunction between the interface of NiCo₂O₄ and CdS.