黄彬彬 曹兴凯 李晶

摘   要：选取邻氯苯酚、間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）.

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

Abstract：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.

Key words：electroreductive dechlorination;mono-chlorophenols;dissociative electron transfer mechanism;molecular structure;linear free energy relationships

氯苯酚类化合物作为一种重要的化工原料，被广泛地用于生产杀菌剂、药物、农药、染料等化学制品[1-2]. 氯苯酚类物质很容易进入到环境中，并且由于其不可生物降解性而造成环境污染[3]. 同时，由于该类物质在……