2,4-二氯苯酚的电化学氧化降解反应研究

Studies on Electrochemical Oxidation Reaction of 2,4-Dichlorophenol on Pt Electrode

采用循环伏安法和原位红外光谱技术研究了2,4-二氯苯酚在Pt电极上的电化学氧化降解反应,结合Fukui函数值预测了2,4-二氯苯酚在电化学氧化过程中的反应位点.结果表明,Pt电极对2,4-二氯苯酚有良好的电催化活性,2,4-二氯苯酚在电极表面反应主要有3个途径:直接通过电化学反应脱去氯离子,生成苯酚;在·OH的进攻下,C—Cl键断裂,4位Cl较2位Cl先脱去,生成苯二酚,并可进一步氧化生成苯醌以及不饱和羧酸;在·OH的进攻下发生苯环开环反应,生成含氯不饱和羧酸.在1700 mV左右,2,4-二氯苯酚可经电化学氧化生成CO2.

Cyclic vohammetry（CV） and in situ FTIR spectrometry were employed to study the electrochemical oxidation mechanism of 2,4-dichlorophenol （2,4-DCP） in NaOH solution. Density functional theory （DFT） was used to calculate the Fukui function for 2,4-DCP and gave the information on possible reactive sites of 2,4-DCP during electrochemical oxidation. CV results show that the Pt electrode exhibits a high electrochemi- cal activity for the electrochemical oxidation reaction of 2,4-DCP. On the basis of in situ FTIR data, the elec- trochemical oxidation reaction of 2,4-DCP is as follows ： （ 1 ） C--C1 band of 2,4-DCP is broken to form phenol directly; （2） C--C1 band of2,4-DCP is broken and C--O band is formed with ~ OH radicals, and the Fukui function results show that chlorine atom at 4 position is easier to be replaced with the hydrogen or ~ OH radi- cals. Then hydroxylation reaction happens on the C4-position of phenol leading to form hydroquinone which is subsequently electrochemically oxidized to benzoquinone. With the potential increasing, aliphatic carboxylic acids are formed after the ring cleavage ; （ 3 ） part of 2,4-DCP is electrochemically oxidized to chloromaleic acid directly. At about 1700 mV, CO2 could be formed during electrochemical oxidation reaction of 2,4-DCP on Pt electrode.