掺硼金刚石电极电催化氧化酚类有机物的取代基效应

本文主要以当前水环境中存在酚类有机污染物为研究对象,探讨酚类有机污染物在掺硼金刚石(BDD)电极上的取代基效应,具体研究具有不同位置及种类官能团的取代酚类有机污染物在BDD电极上的电催化氧化过程,通过化学需氧量和浓度变化考察有机污染物在电催化降解过程中的降解趋势,深入分析电极种类、官能团位置与种类与电催化氧化活性之间的联系的同时,研究阳极材料电催化氧化有机污染物的机理及动力学。结果表明,有机物在电极表面的电催化过程以电产生羟基自由基为媒介,对苯二酚在不同电极上的电催化活性与电极析氧电位及表面产生羟基自由基量有着重要的联系,BDD电极拥有最强的电催化氧化活性;不同取代基团的对位取代酚在BDD电极上的电化学降解实验显示电催化反应速率受取代官能团自身的电子效应制约,有机物矿化过程中羟基自由基首先进攻苯环的对位发生取代反应,同时取代基脱离苯环过程成为整个取代酚类电化学降解过程的决速步骤,且有机物的电催化反应速率与取代基特征Hammett常数σ呈近似线性关系。

Electrochemical Oxidation of Substituted Phenols on a Boron Doped Diamond Electrode

In this work, the effect of different phenolic substituents on the electrochemical oxidation of phenols on a boron doped diamond (BDD) electrode was investigated. The specific relationship between the position and type of substituent and the electrochemical oxidation activity on the BDD electrode was systematically studied by employing Chemical Oxygen Demand and concentration variation. Electrochemical mineralization of hydroquinone was conducted on electrodes with different oxygen evolution potentials. It was found that there exists an important relationship between the electrochemical activity and the ability to generate hydroxyl radicals. A high activity was achieved on the BDD electrode owing to its higher electro-generation ability for hydroxyl radicals. The mineralization of substituted phenols is indirectly conducted by the hydroxyl radicals and the divorce of the substituent group is the rate determining step for the mineralization process. Meanwhile, the electrochemical mineralization rate towards substituted phenol contaminants is limited by the electronic effects of the substituents. The mineralization rate increases with increasing electron donating ability of the substituent. A linear relationship is found to exist between the reaction rate and the Hammett constant during degradation of substituted phenols.