Mechanism Of Heterogeneous Fenton Reaction On The Surface Of Zinc And Copper Compound

Due to the ignificant biological toxicity,environmental persistence,and bioaccumulation,refractory organic pollutants cause continuous damage to the ecological environment and pose a serious threat to human life and health.As an advanced oxidation process,Fenton reaction can produce strong oxidizing free radicals,which can effectively remove the refractory organic pollutants in water without secondary pollution.However,Fenton reaction has been greatly hindered in practical application and promotion because of the narrow p H response range（2.5-3.5）,large iron sludge production,and large metal ion dissolution.The developed heterogeneous Fenton like catalytic system based on the traditional Fenton mechanism has advantages such as wide p H response range,no iron sludge generation,easy solid-liquid separation,and recyclability.It is considered an ideal technology for removing organic pollutants from water.Zinc and copper based compounds exhibit excellent heterogeneous Fenton catalytic activity,but the detailed mechanism of the heterogeneous Fenton reactions is still unclear.In this work,based on density functional theory,the detailed process of heterogeneous Fenton catalytic reaction and the thermal/dynamic characteristics of the reaction were studied from the perspective of atoms and electrons.This work revealed the microscopic mechanism of heterogeneous Fenton catalytic reaction,clarified the reaction active site,and revealed the intrinsic relationship between the catalyst microstructure and catalytic activity.This work can provide a theoretical basis for the design and preparation of highly active and stable heterogeneous Fenton catalysts.The specific research content is as follows:Firstly,the mechanism and activity of in-situ generation and decomposition of H₂O₂on the surface of zinc based compounds（Zn X,where X is O,S,Se,Te）were studied.It was found that the catalytic activity of Zn X is closely related to surface structure and hetero-atom doping.H₂O₂can be easily decomposed to form hydroxyl radical on Zn O（110）,Zn Se（100）,Zn Te（110）and Zn Te（100）surfaces,but only Zn O（110）surface can generate H₂O₂through oxygen evolution reaction.Further research has found that Cu doping can improve the decomposition efficiency of H₂O₂on the surface of Zn O（110）,while Ag doping can improve the selectivity of H₂O₂in the oxygen evolution reaction to generate H₂O₂on the surface of Zn O（110）.Through the analysis of the atomic and electronic structures of the active site,we found that the selectivity of the oxygen evolution reaction on the surface of Zn X to form H₂O₂is closely related to the element composition and electronegativity of the active site.A simple descriptor can be used to correlate the relationship between the catalyst microstructure and catalytic selectivity.Secondly,the mechanism and activity of H₂O₂decomposition and formation on the surface of Cu₂O were studied.Research has found that the decomposition and formation of H₂O₂on Cu₂O surfaces exhibit structural selectivity.On the surface of Cu₂O（111）,H₂O₂tends to decompose into two OH*,while H₂O₂will decompose into OOH*and H*on the surface of Cu₂O（110）.Due to the weaker adsorption energy of H₂O₂on the surface of Cu₂O（110）compared to Cu₂O（111）,the energy barrier for H₂O₂decomposition on the surface of Cu₂O（110）is higher.When oxygen vacancies existing on the surface of Cu₂O,the energy barrier for H₂O₂decomposition will decrease and it will promote the decomposition of H₂O₂into two OH*on the surface of Cu₂O（110）.Since the elementary reaction involved in the reaction of O₂and H₂O to generate H₂O₂are endothermic,it is difficult to generate H₂O₂in situ on Cu₂O（110）and（111）surfaces through the reaction of O₂and H₂O.Understanding the mechanism of catalytic reactions from an atomic perspective is an eternal pursuit of catalytic scientists.This work provides a theoretical basis for the preparation and regulation of catalysts,and provides direction for the development of new multiphase Fenton catalysts.