Selective Boron Occupation at Tetrahedral Cation Sites in Co ₃ O ₄ Enables Self-Adaptive Electron Transfer for Enhanced Water Oxidation

The uncontrollable reconstruction of electrocatalysts, such as the detrimental overoxidation of Co₃O₄ during alkaline water oxidation, severely impedes the synergistic enhancement of activity and stability. Therefore, achieving adaptive electron transfer during reactions to maintain an active and stable state is critical, yet it remains largely unexplored. Herein, a novel catalyst in which metalloid boron selectively occupies the tetrahedral cobalt sites in Co₃O₄ is designed to overcome this dilemma, and its atomic structure is unequivocally confirmed by ¹¹B-enriched neutron powder diffraction. The activity of octahedral cobalt is enhanced as boron suppresses covalent competition, while the operational stability is maintained through the adaptive electronic tuning of [BO₄] units, which possess electrons delocalized over extended spatial dimensions. Specifically, electrons transfer from cobalt to boron at lower potentials to activate cobalt but reverse at higher potentials to sustain Co³⁺ states by suppressing overoxidation, as demonstrated by operando Raman spectroscopy, X-ray absorption spectroscopy, and quasi-in situ X-ray photoelectron spectroscopy. Consequently, (Co_0.86B_0.14)Co₂O₄ achieves superior activity and stability in both three-electrode and electrolytic cell systems, outperforming the vast majority of Co₃O₄-based catalysts. This study pioneers an adaptive regulation strategy by precisely anchoring [BO₄] units, providing a general design principle for next-generation adaptive electrocatalysts that combine high activity with robust stability.