薄层循环伏安法研究硝基苯/水界面上离子诱导的电子转移反应

应用薄层循环伏安法研究了硝基苯/水两相界面间,且有共同离子四丁基铵TBA+存在于两相中,在有机相中的四氰化二甲基苯醌(TCNQ)与水相中的K4Fe(CN)6之间发生的反向电子转移反应。在直径为0.64cm的裂解石墨电极上用2μL硝基苯溶液使之自然扩散在电极表面形成薄层的有机相,并以此作为工作电极。对电极为铂丝(0.5mm),参比电极为Ag/AgCl电极,均置于总体积为2mL的水相中。由于共同离子TBA+的诱导,在硝基苯/水界面间,在已氧化的TCNQ+阳离子(在有机相中)与Fe(CN)6]4-阴离子(在水相中)之间发生了反向电子转移反应。试验证明:在一定条件下,通过改变两相中共同离子的浓度,可使一些不能发生的两相界面的电子转移反应得以发生;这类电子转移反应系受界面电位差所控制。此外,还测得了在恒定的共同离子浓度比值的条件下,此两相界面电子转移反应的表观速率常数(k)为0.135cm.s-1.mol-1。

Thin Layer Cyclic Voltammetric Study on the Ion-induced Electron Transfer at the Interface of Nitrobenzene and Water

The reverse electron transfer reaction between tetracyano dimethylbenzoquinone(TCNQ) in the organic phase and K4Fe(CN)6 in the water phase with TBA+ as the common ion in the 2 phases was studied by thin layer cyclic voltammetry(TLCV).Pyrolytic graphite electrode( 0.64 cm) was used as working electrode with a thin layer of nitrobenzene solution(2 μL) spread upon the electrode as the organic phase.Platinum wire(0.5 mm) and Ag/AgCl electrode were used as the counter electrode and reference electrode respectively,which were placed in the water phase having its total volume of 2 mL.Reverse electron transfer reaction between the oxidized TCNQ+ ion and Fe(CN)6]4-ion induced by the common ion TBA+ was observed at the C6H5NO2/H2O interface.It was proved that under definite conditions,by varying the concentration of the common ion in the 2 phases,happening of some impossible electron transfer reaction at the O/W interface was realized,and that such reactions were controlled by the interfacial potential difference.At a constant concentration ratio of the common ion in the two phases,the apparent reaction rate constant(k) was found to be 0.135 cm·s-1·mol-1.