Iron Oxide Nanoclusters Incorporated into Iron Phthalocyanine as Highly Active Electrocatalysts for the Oxygen Reduction Reaction

Abstract

AbstractIron‐nitrogen‐carbon (Fe‐N‐C) composites have emerged as active and non‐precious‐metal electrocatalysts for the oxygen reduction reaction (ORR). Here, we developed a simple process to synthesize FeOx nanoclusters (NCs) incorporated with iron phthalocyanine (FePc) supported on graphene (FeOx/FePc) as highly active electrocatalysts for the ORR by a self‐assembly method. The electrochemical activity of FeOx/FePc depends on the loading or size of the FeOx NCs. The best results are obtained on FeOx/FePc with 10 wt % FeOx NCs of a size of approximately 2 nm and a thickness of approximately 0.6 nm, which achieves a half‐wave potential of 0.888 V and current density of 37.6 Ag−1 at 0.9 V (vs. the reversible hydrogen electrode). This is 50 mV higher than that of FePc supported on graphene and 64 mV higher than that of Pt/C in 0.1 m KOH solution at a catalyst loading of 0.1 mg cm−2. X‐ray absorption spectroscopy and electrochemical cyclic voltammetry results indicate that the incorporated FeOx NCs interact with the active center of FePc, Fe−N4, to enhance the electron transition and reversibility of the FeIII/FeII redox couple and promote the kinetics of the ORR. We demonstrate that the nature of the active center of FePc (i.e., Fe−N4) is related closely to the activity of the FeIII/FeII redox couple.