Preparation And Modification Of Cobalt Tetroxide For Photocatalytic Properties

Photocatalytic degradation of pollutants is a very meaningful way,it has the advantages of low cost,easy operation and non-toxicity.Metal oxide semiconductors with high photocatalytic properties are one of the most popular photocatalysts.Cobalt tetroxide?Co₃O₄?is a p-type semiconductor metal oxide with narrow bandgap.The photocatalytic properties can be enhanced by controlling the bandgap,increasing the specific surface area and heterojunction recombination.In this paper,hydrothermal method was used to prepare Co₃O₄photocatalyst.During the preparation process,technological parameters such as solvent fillings,hydrothermal reaction temperature and reaction time were considered to compare the differences in structure and photocatalytic properties of Co₃O₄.The mechanism of photocatalytic properties of Co₃O₄ was discussed.The experimental results show that hydrothermal method has good photocatalytic properties for the Co₃O₄ materials prepared by solvent fillings of70 mL,hydrothermal temperature of 120?,hydrothermal time of 5 h and calcination for 2 h at 400?,taking Rhodamine B?RhB?as a model,three hours for the degradation of RhB solution reached 80.84%.Secondly,the Co₃O₄ material was prepared by metal organic framework?MOF?template method.During the preparation process,technological parameters such as reactant molar ratio,reaction time and calcination temperature were considered to compare the differences in structure and photocatalytic properties of Co₃O₄.The Co₃O₄ material characteristic by X-ray diffraction?XRD?,fourier transform infrared spectroscopy?FT-IR?,UV-visible diffuse reflectance spectrum?DRS?specific surface area?BET?and other methods.Comparing the differences in structure,photocatalytic properties and degradation rate of Co₃O₄ prepared by hydrothermal method,than discuss the mechanism of photocatalytic properties.The experimental results show that increasing the specific surface area of Co₃O₄ can improve the efficiency of photocatalytic degradation of RhB.The MOF template method in reactant molar ratio n?Co?:n?N?=1:11,reaction after 6 h to get the sample of the 3 h under300?calcination get Co₃O₄ photocatalytic properties is best,and its specific surface area is 110.45 m²·g^-1,three hours for the degradation of RhB solution reached 92.91%.Finally,the n-type semiconductor metal oxide WO₃ and Co₃O₄ were combined to construct a semiconductor metal oxide p-n heterojunction photocatalyst,and preliminarily explored the mechanism of photocatalytic properties of heterojunction structure.The hydrothermal reaction time,hydrothermal reaction temperature,calcination temperature and reactant molar ratio were used to compare the differences in structure and photocatalytic properties of Co₃O₄/WO₃.The results show that the Co₃O₄/WO₃ composite material prepared in reactant molar ratio n?Co?:n?W?=1:2,hydrothermal at120?for 5 h before calcination at 400?for 2 h has maximum degradation rate of RhB solution reached 94.63%.After 5 times of recycling and reuse,the samples maintained good catalytic activity,and the degradation rate of RhB dye remained above 90%.