Construction Of High Selective Oxygen Reduction Catalysts And Study On Photosynthesis Of Hydrogen Peroxide

H₂O₂ is a clean and environmentally friendly oxidant and fuel,which is widely used in pulp bleaching,sewage treatment and other fields.In recent years,the synthesis of H₂O₂ by photoreduction of oxygen has attracted widespread attention due to its advantages of low energy consumption,cleanness and environmental protection.However,there are currently issues with low activity and selectivity in this process,which limit its practical application.Among many catalyst materials,g-C₃N₄ and Zn_0.5Cd_0.5S show excellent visible-light response ability and suitable band structure,which have received extensive focus of researchers.However,the serious recombination of photogenerated carriers and the low selectivity of two electrons result in low photocatalytic performance for hydrogen peroxide.This paper introduces oxygen reducing active centers to improve the selectivity of the two-electron oxygen reduction reaction,promote electron and hole separation efficiency,and enhance the activity and selectivity of photosynthetic hydrogen peroxide.The specific research contents are as follows:（1）The Sc atoms decorated g-C₃N₄（Sc/H-CN）was synthesized through the impregnation-calcination method and the excellent photocatalytic H₂O₂ production was achieved 55μmol h^-1,which is about 6.2 times of g-C₃N₄.The experimental results show that Sc is mainly dispersed in the form of single atom in g-C₃N₄ catalyst,and the valence state of Sc is+3,which has the property of Lewis acid.The improved photocatalytic performance is ascribed to the enhancement of O₂electron-accepting ability through the binding of Sc Lewis acid sites with·O₂^-.Moreover,Sc atoms can also regulate the O₂ adsorption configuration and reduce the broken of O-O bond,leading to a high selectivity to H₂O₂.In addition,the introduction of Sc atoms can improve electron and hole separation efficiency and enhance the performance of photosynthetic hydrogen peroxide.（2）The CDs modified Zn_0.5Cd_0.5S（CDs/ZnCdS）was synthesized by hydrothermal method and the best photocatalytic H₂O₂ activity was exhibited 252μmol h^-1,which are about 33 times that of CDs and 4.5 times that of Zn_0.5Cd_0.5S.Meanwhile,its apparent quantum yield reaches up to 30.5%.The research results indicated that the CDs formed amide bonds with ethylenediamine on the surface of Zn_0.5Cd_0.5S,and the formation of amide bonds facilitates the transfer of photogenerated electrons from Zn_0.5Cd_0.5S to the surface of CDs.At the same time,CDs with oxygen-containing functional groups as active site can improve the selectivity of the two-electron oxygen reduction reaction and the activity of photosynthetic hydrogen peroxide.This paper proposes new ideas for the design and construction of highly selective photosynthetic hydrogen peroxide catalysts by constructing oxygen reduction active centers,improving the selectivity of oxygen reduction,promoting the oxygen reduction reaction,and enhancing the activity of hydrogen peroxide.