Preparation Of Layered-double-hydroxide Based Photocatalyst And Study On The Performance Of Synthetic Ammonia

In recent years,a series of problems such as energy shortage and ecological destruction have become imminent.Countries all over the world are actively seeking a sustainable and green development technology.Nowadays,solar energy is considered a sustainable and clean source of energy with high economic value.Therefore,utilize solar energy driven semiconductor photocatalytic technology is one of the most promising solutions.Some two-dimensional semiconductor photocatalytic materials with outstanding characteristics have been extensively studied,and layered double hydroxide（LDH）is one of them.The typical two-dimensional sheet structure makes it have excellent photocatalytic potential and unique light response ability.It has been used in photocatalytic N2 reduction,organic pollutant degradation,CO2 reduction and water decomposition and other fields.However,for bulk LDH materials,their small surface area,easy recombination of photogenerated electron-hole pairs,and insufficient active site exposure,greatly hinder the performance improvement of LDH photocatalysts.Hence,it is particularly important to effectively increase the specific active area of LDH photocatalyst,improve the transmission rate of photogenerated carriers,and inhibit the recombination of electron-hole pairs to improve the photocatalytic activity of LDH.Here,this article synthesized a series of ultra-thin LDH photocatalytic materials through in-situ etching and template control methods,which provides a new method for the application prospects of LDH photocatalytic materials.The specific content is as follows:（1）Synthesis of M^ⅡM^Ⅲ-LDH（M^Ⅱ=Mg,Co,Ni;M^Ⅲ=Al）:First,we synthesized the bulk hydrotalcite（LDH-Bulk）comparative material by the co-precipitation method.Next,using commercial cuprous oxide（Cu2O）as a template,a series of ultra-thin hydrotalcite（LDH-NS）nanomaterials were prepared via in-situ etching.The characterization test results show that:LDH-NS nanosheets are successfully synthesized,and have a smaller sheet structure and thickness,which will provide a new way for the synthesis of two-dimensional ultra-thin hydrotalcite materials.（2）Zn Al-LDH photocatalytic nitrogen fixation for ammonia synthesis:First,we successfully synthesized ultra-thin Zn Al-LDH-NS photocatalytic material based on the previous chapter.A series of characterization results proved the chemical structure characteristics of Zn Al-LDH-NS.The synthetic ammonia performance test shows that under the irradiation of a 300 W xenon lamp,the Zn Al-LDH-NS photocatalytic material has obvious ammonia synthesis activity,while the bulk Zn Al-LDH-Bulk hardly produces ammonia.（3）Synthesize three-dimensional micro-nano structure Zn Al-LDH（3D-LDH）and test the performance of ammonia synthesis.First,the cubic template Cu2O was synthesized,and then the three-dimensional Zn Al-LDH photocatalytic material was successfully prepared by in-situ etching.A series of characterization results analyzed the morphological characteristics of 3D-LDH.During the in-situ etching process,the LDH nano-units grow along the radial direction of the template,resulting in the formation of micro-nano structures.Moreover,due to the special chemical properties of the micro-structure surface,3D-LDH can enrich nitrogen and promote the increase in the concentration of reactant nitrogen on the catalyst surface,thus effectively improving the reaction rate.The performance test results show that under the irradiation of 300 W xenon lamp,the 3D-LDH photocatalytic ammonia synthesis rate is as high as 77.85μmol g^-1 h^-1,which is 8 times higher than the performance of ultra-thin Zn Al-LDH（2D-LDH）.