Metal reduction at the interface between two immiscible electrolyte solutions (ITIES) has been studied with scanning electrochemical microscopy (SECM). Metal cations in the aqueous phase are reduced by 7,7,8,8-tetracyanoquinodimethane anion (TCNQ −) residing in the oil phase, methyl isobutyl ketone (MIBK). TCNQ − is formed at the SECM tip by reducing TCNQ, which results in a positive feedback loop between the tip and the ITIES when an electron is donated to a metal cation. The effect of the Galvani potential difference on the rate of the interfacial electron transfer was investigated, establishing the potential difference either by an additional substrate electrode in the aqueous phase or by an a common ion in both phases. It is shown that the Galvani potential difference as a driving force does enable TCNQ − mediated Cu 2+ reduction. Finite element method (FEM) simulations were run to provide information on the reaction kinetics and stoichiometry.