二氧化碳在银电极上发生电还原反应时的电极失活原因

Deactivation of Ag electrode in the electrochemical reduction of CO_2 in aqueous solution

在KHCO3水溶液中,利用线性扫描、塔菲尔曲线、恒电位电解、电化学阻抗谱方法,研究了CO2在银电极上发生电还原反应的动力学特征,发现当电解反应进行一段时间后,阴极表面生成了一层棕黑色物质附着在电极表面,导致生成CO的平衡电位负移,交换电流密度变小,电荷转移电阻增大,电流效率和电流密度迅速降低。用X射线光电子能谱(XPS)分析了有害物质的主要成分,证明阴极表面附着物主要为石墨碳和微量Zn,这些物质附着在阴极表面,导致电极失活,阻碍CO2电还原反应继续进行。

The electrochemical kinetics characteristics of CO2 reduction on Ag electrode has been studied in KHCO3 aqueous solution using Linear sweep curve,Tafel curve,Potentiostatic electrolysis and electrochemical impedance spectroscopy.It is found that certain black substance was adsorbed on the Ag electrode,which resulted in the increase of equilibrium potential,the derease of exchange current,electron transfer resistance,and the derease of current density and Faradaic efficiency.The main components of the poisonous intermediates and electrode deactivation have been studied by X ray photoelectron spectroscopy （XPS）.The results show that graphite is the main components of the poisonous intermediate with very small amount of Zn.These substances will be deposited at the electrode and subsequently deactivate the electrode,which may poison the subsequent reaction.