Rare‐Earth Terbium Frustrates Deep Reconstruction of Cobalt Sulfide for Long‑Lived Anion Exchange Membrane Water Electrolysis

ABSTRACT The practical application of metal sulfides in anion‐exchange membrane water electrolysis (AEMWE) is fundamentally hindered by the uncontrolled deep reconstruction under anodic conditions, which leads to rapid catalyst deactivation. Herein, with cobalt sulfide (Co 9 S 8 ) as a model, we introduce terbium (Tb) sites to frustrate deep reconstruction and relieve catalyst deactivation toward the oxygen evolution reaction (OER). The Tb‐Co 9 S 8 exhibits a low overpotential of 239 and 308 mV to reach 10 and 100 mA cm −2 , respectively toward OER. As an AEMWE anode, the Tb‐Co 9 S 8 achieves 1.0 A cm −2 at only 1.80 V and sustains continuous operation for 4200 h with a degradation rate of only 0.018 mV h −1 . The enhanced OER activity of Tb‐Co 9 S 8 originates from Tb incorporation, which inhibits deep bulk S‐O exchange and induces breathing‐like Co‐O coordination dynamics on the CoOOH active surface to curb over‐reconstruction and alleviate catalyst deactivation. Furthermore, asymmetric Tb atomic sites increase occupancy of spin‐state Co 3+ and optimize the local hydrogen‐bond network, which enhances lattice‐oxygen activation and renders *OH backfilling more spontaneous, thereby mitigating the activity‐stability trade‐off in the lattice oxygen mechanism. This work establishes a new rare‐earth‐mediated strategy to frustrate deep reconstruction and stabilize a real active surface for efficient and stable hydrogen production.