Kinetics of Charge-Transfer Reactions at Nanoscopic Electrochemical Interfaces

After several decades of intensive studies, the questions about the magnitudes of rate constants of rapid heterogeneous electron transfer (ET) and ion transfer (IT) reactions remain open. The fabrication of nanometer-sized metal electrodes and nanopipets enabled electrochemical studies of rapid charge transfer processes at solid/liquid and liquid/liquid nanointerfaces. The nanoelectrochemical techniques offer numerous advantages such as fast mass-transfer rate and simplified analysis of data obtained under steady-state conditions. At the same time, kinetic data obtamed at nanointerfaces may be affected by double layer effects, deviations from classical electrochemical theory, and other size-related phenomena. Nanoelectrochemical measurements are also plagued by difficulties in characterizing nanometer-sized interfaces and conductor/insulator boundaries. In this review, we discuss the results of fast electron and ion transfer kinetics measurements at nanointerfaces, along with related reliability problems and some approaches to fixing them.