应用扫描电化学显微镜研究极化液/液界面上的电子转移反应

将含有氧化还原电对的水溶液滴涂在铂盘电极表面, 然后将该电极插入到1,2-二氯乙烷溶液中, 形成稳定的油/水界面. 液滴中的K3Fe(CN)6和K4Fe(CN)6氧化还原电对既可以作为水相中的参比电对参与控制液/液界面上的电势差, 同时又可以作为水相的电子授受体参与界面上的电子转移反应. 结合扫描电化学显微镜电化学系统的特点, 利用其双恒电位仪分别控制界面电势差和现场扫描的优点, 通过扫描电化学显微镜的渐进曲线得到了不同界面电势差控制的电子转移反应速率常数. 实验结果表明, 应用此方法获得的液/液界面可以被外加电位极化, 在一定的电势差范围内, 反应速率常数与界面电势差的关系遵守Butler-Volmer公式.

Investigation of Electron Transfer Reaction Between Ferri/Ferrocyanide and TCNQ on Polarized Water/1,2-Dichloroethane Interface by Scanning Electrochemical Microscopy

A liquid/liquid interface supported on a metallic electrode was used to study the electron transfer(ET) reactions by scanning electrochemical microscopy(SECM). The system is composed of an aqueous droplet adhered on a platinum disc electrode and immersed into an organic electrolyte solution containing 7,7,8,8-tetracyanoquinodimenthane(TCNQ). The droplet with a redox couple of K3Fe(CN)6 and K4Fe(CN)6 was employed, both were used as a reference electrode on the platinum disc, and as an electron donor/acceptor at the polarized liquid/liquid interface. With the present experimental approach, the liquid/liquid interface can be polarized externally. The apparent heterogeneous rate constants for the ET reactions were extracted by fitting the experimental approach curves obtained from SECM experiments to the theoretical values. These rate constants obey the Butler-Volume formula in some ranges, and they are found to be potential dependent. This method enables a fast and convenient method to measure ET and ion transfer(IT) reactions kinetic parameter.