Optimizing Electron Delocalization in Cobalt Clusters via <i>d‐d</i> Orbital Coupling for Efficient Bifunctional Oxygen Electrocatalysis

Abstract Cobalt atom cluster (Co AC )‐based electrocatalysts usually exhibit high activity for oxygen reduction reaction (ORR), but display limited performance in oxygen evolution reaction (OER). To enhance their bifunctional catalytic efficiency, it is crucial to tailor the d ‐orbital electronic structure of Co AC through orbital coupling effect, optimizing the chemisorption of O‐intermediates. Herein, a 3 d ‐4 d orbital coupling strategy is used to construct a Co AC ‐molybdenum carbide/nanocarbon cake (Co AC ‐Mo x C/CC) catalyst with a hollow structure for ORR/OER in zinc‐air batteries (ZABs). Experimental and theoretical results confirm that the 4 d transition metal Mo, with fewer d electrons and more unfilled orbitals, interacts strongly with Co sites through d ‐ d coupling, promoting electron enrichment and triggering 3 d ‐orbital electron delocalization. This process accelerates the rate‐limiting steps of *OH desorption for ORR and *OOH formation for OER, leading to an ultra‐low potential gap of 0.604 V and improved stability. Notably, the Co AC ‐Mo x C/CC‐based liquid and flexible all‐solid‐state ZABs exhibit excellent performance with high open‐circuit voltages of 1.49 and 1.47 V, and power densities of 146.4 and 103.4 mW cm −2 , respectively, highlighting their potential to replace precious metal catalysts. This study may open new avenues for manipulating the electronic properties of Co AC ‐based electrocatalysts and boosting activity through the d ‐ d orbital coupling strategy.