Tuning Metal/Oxygen Redox Sequence through Constructing [Eu‐O‐Co] Unit for Enhancing Oxygen Evolution

Abstract Triggering the lattice oxygen mechanism (LOM) is a promising approach to overcome the sluggish kinetics of the oxygen evolution reaction (OER), yet effectively enhancing the lattice oxygen participation remains a significant challenge. Herein, we aim to enhance the lattice oxygen participation of spinel Co ₃ O ₄ in OER through introducing rare‐earth europium (Eu) and constructing the [Eu‐O‐Co] unit. The constructed [Eu‐O‐Co] unit facilitates electron donation from Eu to surrounding Co‐O sites, thereby altering the redox sequence of transition metal and lattice oxygen. This structural innovation enables Eu‐Co ₃ O ₄ to present outstanding OER performance including a low overpotential of 305 mV at 10 mA cm ⁻² , robust long‐term stability, and high efficiency in rechargeable Zn‐air batteries. In situ Raman spectroscopy and theoretical calculations reveal that the [Eu‐O‐Co] unit enhances lattice oxygen redox dynamics and enables direct O─O bond formation. The occupied Eu‐4f spin‐up orbitals near the Fermi level play a crucial role in activating highly labile lattice oxygen at Eu‐neighboring oxygen sites, promoting lattice oxygen participation in the non‐concerted proton‐electron transfer process, and lowing the thermodynamically limiting potential of LOM pathway. These findings underscore the importance of rare‐earth elements in modulating lattice oxygen redox dynamics, offering valuable insights for advancing the design of OER catalysts.