Unified ORR mechanism criteria via charge–spin–coordination of Fe functional units

Abstract

For oxygen reduction reaction (ORR) consisting of complex multi-electron and proton-coupled elementary steps, it has been always a core issue to address controlling the adsorption properties of oxygen-containing species (OCs) on the surface and interface of catalysts. Since the unique 3d orbital electronic configuration of Fe functional units (Fe-FUs) enables strong interactions with OCs, sufficient power is provided for the ORR. Inspired by the separation of the three powers, initialized from fingerprinting “charge–spin–coordination” of the catalytic system, we explored and summarized electronic and geometric structures via the descriptors for electronic configuration. Next, the specific catalytic mechanism of Fe-FUs in multiple forms was analyzed, perfectly interpreting the structure–activity relationship in Fe-based catalysts. Finally, the corresponding solutions were put forward by summarizing the bottleneck issues in the deactivation and degradation. This review aims to fully gain high utilization of active components, thereby achieving the win–win goal of combining activity and stability for Fe-based catalysts.