Preparation And Properties Of Photocatalytic Materials Doped With Co₃O₄ And SnS₂

Since the beginning of the 21st century,the problem of energy shortage and environmental pollution around the world has been increasing rapidly.Serious environmental pollution and global warming will bring many negative impacts on human life,which seriously violates the concept of sustainable development.Catalytic processes such as degradation of polluting gases produced in industrial production,photocatalytic synthesis of ammonia and photocatalytic reduction of CO₂ are effective means to solve the problems of environmental pollution and global warming.In the process of photocatalysis,photocatalyst is an important driving material.How to choose high performance photocatalyst is one of the important topics in the study of catalysis.The photocatalytic process is photoexcitation to produce photogenerated carriers、electrons transition to conduction band、holes gather in the valence band、and enough electron holes participate in the catalytic reaction on the surface of the catalyst.In order to carry out the photocatalysis reaction smoothly,a good photocatalysis material needs a suitable band gap and a conduction band valence band position matching with the redox potential.At the same time,it also needs to meet the characteristics of large specific surface area,good carrier separation and transmission efficiency,stability and corrosion resistance.It is difficult to meet the above conditions with simple semiconductor photocatalyst.Therefore,improving the existing photocatalytic materials is one of the important factors to improve the photocatalytic activity.The separation efficiency of photogenerated carrier can be changed by doping metal ions,recombination,manufacturing defects and surface modification,broadening the range of light absorption,increasing the active site on the catalyst surface,and improving the catalytic performance of the photocatalyst.In this paper,the catalytic performance of photocatalyst was improved by doping metal elements.The narrow band gap semiconductor Co₃O₄ and SnS₂ were selected as the research objects.The effect of doping modification on photocatalytic performance and catalytic mechanism were investigated.The following was the specific research content:（1）Preparation,analysis and characterization of Cr-doped Co₃O₄ nanomaterials,photocatalytic degradation of isopropanol and photocatalytic nitrogen fixation performance test.In this paper,Cr-doped Co₃O₄ photocatalytic material was successfully prepared by sol-gel method.Cr（NO₃）₃·9H₂O was used as the source of chromium.A certain amount of Cr（NO₃）₃·9H₂O and chelating agent were added into Co（NO₃）₂·9H₂O.Through XRD,XPS,SEM,nitrogen adsorption desorption and UV-visible absorption and other technical tests,could accurately describe the physical properties of the sample,surface chemical characteristics,morphological characteristics,specific surface area size,aperture distribution range,UV-visible absorption efficiency and band gap characteristics.Among them,only the diffraction peak of Co₃O₄ appeared in the XRD test pattern,and no impurity peak appeared,indicating that Cr was successfully doped into Co₃O₄.The specific surface area of 5Cr-Co₃O₄ was 19.13 m²g^-1,4.1 times that of Co₃O₄.The number of pores in the diameter distribution of 30-50nm was significantly increased.The photocurrent of 5Cr-Co₃O₄ was 5.25 m A·cm^-2,5.1 times that of pure Co₃O₄.Within1h,the photocatalytic degradation rate of isopropyl alcohol by 5Cr-Co₃O₄ was 7.4times that of pure Co₃O₄.The results of photocatalytic nitrogen fixation showed that the yield of 5Cr-Co₃O₄ ammonia was 244μmol/g_mat,which was 6.38 times of that of pure Co₃O₄.（2）Preparation,analysis and characterization of Ce-doped SnS₂ nanomaterials and photocatalytic CO₂ reduction performance test.In this paper,Ce doped SnS₂ photocatalyst was successfully prepared by hydrothermal method.By changing the Ce doping amount,the photocatalytic CO₂reduction performance of SnS₂ samples with different doping amounts was explored.Different amounts of Ce（NO₃）₃·9H₂O were controlled as the source of cerium,SnCl₄·5H₂O was added,the solution was formed by full stirring,and the liquid was heated for several hours.After centrifugation and drying,Ce doped SnS₂ powder was prepared.Only SnS₂ diffraction peak appeared in the XRD pattern,and no other impurity peak appeared,indicating that Ce was successfully doped into SnS₂.SEM results also showed that Ce was uniformly distributed in SnS₂.The specific surface area of the doped sample was 28 m²g^-1,2.2 times that of pure SnS₂.The photocatalytic CO₂ reduction to CO of 5Ce-SnS₂ was 187.76μmolg^-1h^-1,which was3.21 times that of pure SnS₂.