Kinetics of heterogeneous electron transfer at liquid/liquid interfaces asstudied by SECM

Scanning electrochemical microscopy (SECM) was used to investigate the kine tics of heterogeneous electron transfer (ET) as a function of driving force at the interface between two immiscible electrolyte solutions. At high dri ving force, experimental rate constants decreased with increasing overpoten tial, deviating from predictions based on Butler-Volmer kinetics. This decr ease in ET rate with increasing driving force is consistent with Marcus the ory inverted region behavior. Ar low driving force, the potential dependenc e of the forward and reverse ET rate constants followed Butler-Volmer theor y. SECM is also demonstrated to be a useful means of studying the effect of high ionic strength on the kinetics of heterogeneous ET.