Molecular oxygen and hydrogen peroxide reduction by 1,2-diferrocenylethane (DFcE) was investigated at a polarized water/1,2-dichloroethane (W/DCE) interface. The overall reaction points to a proton-coupled electron transfer (PCET) mechanism, where the first step consists of the protonation of DFcE to form the DFcE-H+ in DCE phase, either by DFcE facilitated proton transfer across the liquid-liquid interface or by the homogeneous protonation of DFcE in the presence of protons extracted in the oil phase by tetrakis(pentafluorophenyl)borate. The formation of DFcE-H+ is followed up by the O-2 reduction to hydrogen peroxide and further reduction to water. The final products of DFcE oxidation, namely DFcE(+) or DFcE(2+), were investigated by ion transfer voltammetry, ultramicroelectrode voltammetry and UV/visible spectroscopy. These results show that mostly DFcE(+) is produced, although DFcE(+) can also reduce oxygen at longer time scales. Hydrogen peroxide reduction is actually faster than oxygen reduction, but both reactions are slow due to relatively low thermodynamic driving force. (C) 2012 Elsevier B.V. All rights reserved.