SCANNING ELECTROCHEMICAL MICROSCOPY .31. APPLICATION OF SECM TO THE STUDY OF CHARGE-TRANSFER PROCESSES AT THE LIQUID-LIQUID INTERFACE

The kinetics of the electron transfer and ion transfer at the interface between two immiscible electrolyte solutions (ITIES) were probed directly by scanning electrochemical microscopy (SECM). The liquid/liquid (i.e., water/nitrobenzene) interface appeared to be sharp and wave-free on the submicrometer scale. The use of SECM allowed the electron transfer between ferrocene species in nitrobenzene and other redox species in the aqueous phase to be quantitatively separated from the ion transfer processes. The rate constants were extracted from the dependence of the steady-state current at a micrometer-sized tip electrode on the distance between the tip and the phase boundary by comparison to theoretical working curves. In some experiments, the ultramicroelectrode tip penetrating the ITIES trapped a micrometer-thick layer of water inside the nitrobenzene, forming a thin-layer cell.