Atomically Dispersed Fe Confined into MnO Nanoclusters Enhances Alkaline Oxygen Reduction Activity and Stability

Transition metal oxide electrocatalysts are promising alternatives to expensive noble metals for the oxygen reduction reaction (ORR). Here, we present a simple metal-atom localization strategy to confine the atomically dispersed Fe into MnO nanoclusters, which are dispersed and immobilized on high-conductivity carbon support (MF/CN). The experimental and theoretical calculation results reveal that the trace Fe(III) ions doped into MnO nanoclusters can induce charge transfer and spin state transition to trigger a butterfly effect, obtaining abundant active Mn(III) with single-electron e_g configuration and strengthened built-in electric field (BIEF), which is greatly helpful to balance the adsorption and desorption of ORR O-containing intermediates, facilitate the interfacial electron transfer, and improve the electrical conductivity. As a result, the optimized MF_0.04/CN exhibits compelling alkaline ORR activity (half-wave potential 0.79 V vs. RHE) and stability (nearly 100% current retention rate for 30 h). Finally, the MF_0.04/CN realizes a remarkable power density (138 mW cm^-2) and durability (>666 h at 10 mA cm^-2) in Zn-air batteries. This finding not only helps to design high-performance metal oxide heterointerfaces by tuning e_g orbital occupancy and BIEF strength, but also deepens the understanding of the reaction mechanism.