Oxygen reduction with tetrathiafulvalene at liquid/liquid interfaces catalyzed by 5,10,15,20-tetraphenylporphyrin

• O2 reduction by TTF can be catalyzed by H2TPP.
• TTF can reduce O2 to H2O alone and to H2O2 in the presence of H2TPP.
• Polarization activation of O2 by H4TPP2+ is further proved.

In this work we report the catalytic effect of 5,10,15,20-tetraphenylporphyrin (H2TPP) on the reduction of oxygen (O2) by a weak electron donor, namely tetrathiafulvalene (TTF), at the polarized water/1,2-dichloroethane (DCE) interface. TTF alone, as reported previously, can reduce O2 slowly via a four-electron transfer pathway to produce water. Herein we show that H2TPP can catalyze the reduction of O2 by TTF to form hydrogen peroxide (H2O2) at the water/DCE interface, which was investigated by voltammetry and biphasic shake-flask experiments. The overall process was found to be essentially a proton-coupled electron transfer reaction. And the results also proved that the catalytic activity of H2TPP toward O2 reduction under acid condition arises from the polarization activation of O2 by H2TPP diacid, namely H4TPP2+.