Preparation And Photocatalytic Application Of Palygorskite Based Full Spectrum Nanocomposites

Energy and environmental issues remain challenges for the development of all countries.With the decreasing of fossil fuels in traditional energy,photocatalysis technology has the advantages of lower energy consumption and mild reaction conditions compared with traditional catalysis.However,photocatalytic technology also has some problems,such as low utilization rate of solar light,easy recombination of electrons and holes and high catalyst cost,which restricts its practical application.In this work,using 1D clay silicate mineral palygorskite(Pal)as the matrix material,W₁₈O₄₉/H-Pal,MoO_3-x/H-Pal and Bi₁₂SiO₂₀/BiO_2-x nanocomposites were prepared by microwave hydrothermal method.and they were utilized in reduction application of nitrogen and carbon dioxide.The main work of this paper is as follows:The W₁₈O₄₉/H-Pal composite was prepared by microwave hydrothermal method using phosphoric acid modified palygorskite(H-Pal)as matrix.It is used for photocatalytic reduction of nitrogen to produce ammonia.The results show that the LSPR effect W₁₈O₄₉ can broaden the light response range to near infrared light.In this photocatalyst system,a Z-scheme heterojunction is formed between W₁₈O₄₉ and H-Pal,which retains strong redox ability and reduces the recombination rate of electrons and holes.The W₁₈O₄₉can produce hot electrons to reduction N₂ and improves the utilization of sunlight as well as the yield of ammonia production.Under full spectrum,the yield of ammonium ion reaches the highest of 138.76?mol·g^-1·h^-1when the loading amount of W₁₈O₄₉ is 40%,while achieving 78.76?mol·g^-1·h^-1ammonia production rate under NIR light.The MoO_3-x/H-Pal composite was prepared by microwave hydrothermal method using phosphoric acid modified palygorskite(H-Pal)as matrix.MoO_3-x quantum dots with LSPR effect grew in situ on the H-Pal surface,showing a good broad-spectrum absorption.At the same time,the photo-generated charges and holes follow the S-type heterojunction mechanism,which improves the efficiency of electron-hole separation.The abundant oxygen vacancies in MoO_3-x can act as charge carrier acceptors to inhibit the recombination of photo-generated electrons/holes and promote the transfer of interfacial charge carriers.Oxygen vacancies and the metal coordination unsaturation points brought about by them are conducive to capturing electrons to generate CO₂^·-,and oxygen vacancies can adsorption and activation of CO₂,which in turn promotes the process of CO₂ photocatalytic reduction.Under simulated sunlight irradiation,the reduction performance of the composite material is the highest when the loading quality score of MoO_3-x quantum dots is 30%,and the reduction performance of CH₃OH and CH₄ are 6.2?mol·g^-1·h^-1 and 2.5?mol·g^-1·h^-1,respectively.Under NIR light,the rate of CH₃OH generation is 2.1?mol·g^-1·h^-1,which realizes full-spectrum absorption and uses solar energy to reduce carbon dioxide.Using Pal as the silicon source,the Bi₁₂SiO₂₀/BiO_2-x nanocomposite was prepared by the microwave hydrothermal method,and applied to photocatalytic reduction of carbon dioxide under simulated sunlight.The results show that Pal retains its unique silicate tidal structure after strong acid treatment,and the introduction of Biions enables the in-place conversion of one-dimensional silicate material to two-dimensional visible light in response to Bi₁₂SiO₂₀nanosheet.The precipitated BiO_2-x can reach the near-infrared light region due to its extremely narrow band gap.Moreover,the two-dimensional bismuth silicate nanosheets have the advantages of large specific surface area and abundant active sites,and the BiO_2-x material contains abundant oxygen vacancies,which are conducive to the adsorption and activation of carbon dioxide.Under simulated sunlight,when the precipitation mass ratio of BiO_2-xis 30%,the generation rates of CH₃OH and CH₄ reach the highest of 8.2?mol·g^-1·h^-1 and 4.5?mol·g^-1·h^-1,respectively.Under near-infrared light(>780 nm),the sample still has excellent CH₃OH generating activity with a generation rate of 4.5?mol·g^-1·h^-1.An S-type heterojunction is formed between Bi₁₂SiO₂₀ and BiO_2-x,which can effectively separate photo-generated electrons and holes,thereby improving the utilization of sunlight and the efficiency of photocatalytic reduction of carbon dioxide.