Utilizing Molybdenum to Tailor the Electronic Structure of Iron Through Electron Complementary Effect for Promoting Oxygen Reduction Activity

Abstract Tailoring the electronic structure of later transition metal‐based electrocatalysts by incorporating early transition metal based on the electronic complementary effect is anticipated to enhance the electrocatalytic activity. Herein, the modulation of the electronic structure of Fe₃C through the utilization of Mo₂C to promote oxygen reduction reaction (ORR) activity is reported. In situ characterizations combined with theoretical calculations reveal that the electron‐donating capability of molybdenum in Mo₂C to the active center of iron in Fe₃C optimizes the adsorption and activation of oxygen. Concurrently, the d‐band center of Fe is much closer to the Fermi level, which reduces the energy barrier for the rate‐determining step (^*OOH → ^*O), thereby enhancing the ORR activity. In alkaline media, the catalyst delivers a half‐wave potential (E_1/2) of 0.89 V and maintains its efficiency with a mere 8 mV decay after 10 000 cycles, surpassing that of Pt/C. Moreover, it can serve as an air cathode in both liquid‐state and all‐solid‐state zinc‐air batteries (ZABs) and shows promising applications in portable devices. This work brings an innovative design concept for highly efficient electrocatalysts suitable for advanced energy devices.