Oxygen Electrocatalysis at Mn ^III -O _x -C Hybrid Heterojunction: An Electronic Synergy or Cooperative Catalysis?

The interface at the metal oxide-carbon hybrid heterojunction is the source to the well-known "synergistic effect" in catalysis. Understanding the structure-function properties is key for designing more advanced catalyst-support systems. Using a model Mn ^III -O _x single-layer catalyst on carbon, we herein report a full elucidation to the catalytic synergism at the hybrid heterojunction in the oxygen reduction reaction (ORR). The successful fabrication of the single-layer catalyst from bottom-up is fully characterized by the X-ray absorption fine structure and high-resolution transmission electron microscopy. For oxygen electrocatalysis over this model hybrid heterostructure, our results, from both theory and experiment, show that the synergistic ORR truly undergoes a cooperated two-step electrocatalysis with catalytic promotion (ΔE _onset = 60 mV) near the heterojunction and over the single-layer catalyst through an interfacial electronic interplay, rather than an abstruse transition towards a one-step dissociative pathway. Finally, we report a superior peroxide-reducing activity of 432.5 mA cm ^-2 mg _(M) ^-1 over the Mn ^III -O _x single-layer.