单氯代苯酚在惰性和催化电极上的电还原脱氯机理研究  

Study on the Mechanism for Electroreductive Dechlorination of Mono-chlorophenols on Inert and Catalytic Electrodes

作　　者：黄彬彬 曹兴凯 李晶 HUANG Binbin;CAO Xingkai;LI Jing(College of Environmental Science and Engineering,Hunan University,Changsha 410082,China;Key Laboratory of Environmental Biology and Pollution Control(Hunan University),Ministry of Education,Changsha 410082,China)

机构地区：[1]湖南大学环境科学与工程学院,湖南长沙410082 [2]环境生物与控制教育部重点实验室(湖南大学),湖南长沙410082

出　　处：《湖南大学学报（自然科学版）》2021年第2期125-131,共7页Journal of Hunan University:Natural Sciences

基　　金：国家自然科学基金资助项目(5177091149)。

摘　　要：选取邻氯苯酚、间氯苯酚和对氯苯酚为目标污染物,采用循环伏安法(CV)考察其在惰性(玻碳,GC)及催化(Ag和Pd)电极上的电还原脱氯活性及机理,探讨污染物的分子结构对电化学还原脱氯过程的影响.结果显示,三种单氯代苯酚在GC电极上的电子转移系数(k值)均大于0.5,表明单氯代苯酚在GC电极上的C-Cl键断裂过程遵循分步离解电子转移机理.而在Ag和Pd电极上,单氯代苯酚的还原峰电位出现显著正移,显示出其对单氯代苯酚具有极强的电催化脱氯活性.同时,催化(Ag和Pd)电极上的k值远远小于0.5,表明C-Cl键的还原裂解遵循同步离解电子转移机理.研究进一步显示,三种单氯代苯酚的电催化脱氯活性遵循对氯苯酚>间氯苯酚>邻氯苯酚的顺序,这主要归因于空间位阻效应,致使处于邻位的氯原子最难与电极表面结合;三种单氯代苯酚的最低未占分子轨道能(ELUMO)的大小为:邻氯苯酚>间氯苯酚>对氯苯酚,表明其还原脱氯的难易程度遵循相反的顺序.最后,基于单氯代苯酚的分子结构特性,选取ELUMO作为结构参数,成功建立了其与电还原脱氯活性间的良好线性自由能关系(LFERs).In this study,o-CP,m-CP and p-CP were selected as the target pollutants,and then the performance and mechanism of electroreductive dechlorination of mono-chlorophenols on inert(GC)and catalytic(Ag and Pd)electrodes were studied by cyclic voltammetry(CV).In addition,this study also explored the impact of molecular structure on the process of electrochemical reduction of mono-chlorophenols.The results showed that all the obtained values of k of these three types of mono-chlorophenols from GC electrode were all greater than 0.5,indicating that reductive cleavage of C-Cl bond on GC electrode followed a stepwise mechanism.Nevertheless,a noticeable positive shift of the reduction peak potential of mono-chlorophenols on Ag and Pd electrodes was observed.Pd exhibited excellent electrocatalytic properties towards dechlorination of mono-chlorophenols.Moreover,the involved values of k on catalytic electrodes(Ag and Pd)were far less than 0.5,which indicated that reductive cleavage of C-Cl bond followed a concerted mechanism.This research further showed that the electrocatalytic dechlorination reactivity of these three types of mono-chlorophenols followed a descending trend as p-CP>m-CP>o-CP.This phenomenon was mainly due to the existence of steric hindrance,which made it the most difficult for chlorine atom at ortho-position to combine with the electrode surface.In addition,the values of the lowest unoccupied molecule orbital energy(ELUMO)of these three types of mono-chlorophenols followed a descending order as:o-CP>m-CP>p-CP,indicating that the reductive dechlorination of mono-chlorophenols followed the opposite order.Finally,based on the molecular structure characteristics of mono-chlorophenols,the parameter ELUMO was selected and successfully developed a good linear free energy relationships(LFERs)with the electroreductive dechlorination reactivity in this research.

关 键 词：电还原脱氯 单氯代苯酚 离解电子转移机理 分子结构 线性自由能关系 

分 类 号：X592[环境科学与工程—环境工程]