Unraveling the Phase-Transfer Catalysis Mechanism of Oxygen Reduction Catalyzed by Iron(III) meso-tetra-(4-N-Methyl-pyridyl) Porphine at the Liquid/Liquid Interface

Graphical Phase-transfer catalysis : Fe III meso -tetra-(4- N -methyl-pyridyl) porphine (Fe III TMPyP) is found to catalyze oxygen reduction at the liquid/liquid interface. Based on the size-selective ion-transfer voltammetry at the nanoscopic liquid/liquid interface, the reaction is rationalized to proceed through the phase-transfer catalysis mechanism. We report an investigation of the oxygen reduction reaction (ORR) catalyzed by Fe III meso -tetra-(4- N -methyl-pyridyl) porphine (Fe III TMPyP) at the polarized water/1,2-dichloroethane (DCE) interface. Fe III TMPyP is a water soluble pentavalent cation, which has a standard Galvani transfer potential of +0.19 V at the water/DCE interface. By four-electrode cyclic voltammetry and shake-flask biphasic reactions controlled by chemical polarization at the macroscale water/DCE interface, we demonstrated that Fe III TMPyP can catalyze the reduction of O 2 by electron donors (e.g., ferrocene and 1,1′-dimethylferrocene). Further, based on voltammetry at the free-standing silica nanochannel membrane (SNM) supported nano-ITIES (interface between two immiscible electrolyte solutions) array where the transfer of Fe III TMPyP is physically blocked owing to the size-exclusion effect, we proved that the overall reaction proceeds through a phase-transfer catalysis (PTC) process, namely the heterogeneous ion transfer of Fe III TMPyP from water to DCE followed by the homogeneous catalyzed ORR in DCE.