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 interfac e between two immiscible electrolyte solutions (ITIES) were probed dir ectly by scanning electrochemical microscopy (SECM). The liquid/liquid (i.e., water/nitrobenzene) interface appeared to be sharp and wave-fr ee on the submicrometer scale. The use of SECM allowed the electron tr ansfer between ferrocene species in nitrobenzene and other redox speci es in the aqueous phase to be quantitatively separated from the ion tr ansfer processes. The rate constants were extracted from the dependenc e of the steady-state current at a micrometer-sized tip electrode on t he distance between the tip and the phase boundary by comparison to th eoretical working curves. In some experiments, the ultramicroelectrode tip penetrating the ITIES trapped a micrometer-thick layer of water i nside the nitrobenzene, forming a thin-layer cell.