Engineering 3d–2p–4f Gradient Orbital Coupling to Enhance Electrocatalytic Oxygen Reduction

Abstract The development of highly efficient and economical materials for the oxygen reduction reaction (ORR) plays a key role in practical energy conversion technologies. However, the intrinsic scaling relations exert thermodynamic inhibition on realizing highly active ORR electrocatalysts. Herein, a novel and feasible gradient orbital coupling strategy for tuning the ORR performance through the construction of Co 3d‐O 2p‐Eu 4f unit sites on the Eu 2 O 3 –Co model is proposed. Through the gradient orbital coupling, the pristine ionic property between Eu and O atoms is assigned with increased covalency, which optimizes the e g occupancy of Co sites, and weakens the OO bond, thus ultimately breaking the scaling relation between *OOH and *OH at Co–O–Eu unit sites. The optimized model catalyst displays onset and half‐wave potential of 1.007 and 0.887 V versus reversible hydrogen electrode, respectively, which are higher than those of commercial Pt/C and most Co‐based catalysts ever reported. In addition, the catalyst is found to possess superior selectivity and durability. It also reveals better cell performance than commercial noble‐metal catalysts in Zn–air batteries in terms of high power/energy densities and long cycle life. This study provides a new perspective for electronic modulation strategy by the construction of gradient 3d–2p–4f orbital coupling.