Molecular electrocatalysis of oxygen reduction by iron(II) phthalocyanine at the liquid/liquid interface

Liquid/liquid interface electrochemistry has manifested itself as a good approach to study oxygen reduction reaction (ORR) and ORR catalyzed by various catalysts. In this work, we investigated the ORR catalyzed by iron(II) phthalocyanine (FePc), which has a structure similarity to the heme group of O 2 -binding proteins and reducing enzymes, at the polarized water/1,2-dichloroethane interface. Using the four-electrode cyclic voltammetry and the shake-flask biphasic reaction under chemically controlled polarization, it was demonstrated that FePc could catalyze the molecular oxygen reduction by lipophilic electron donors , such as 1,1′-dimethylferrocene (DFc) or tetrathiafulvalene (TTF), at the heterogeneous phase boundary . The overall process essentially can be equivalent to an interfacial proton transfer coupled ORR, which proceeds preferentially via a four electron reduction pathway to produce mainly H 2 O with only minority of H 2 O 2 (less than 5%). The catalytic activity of FePc was compared with all previously studied porphyrins and phthalocyanines. The reaction mechanism was also analyzed, in which a hydroperoxo intermediate was probably involved.