Edge‐Sharing Octahedra‐Rich Medium‐Entropy Selenide Enables Robust Seawater Oxidation via Programmable Reconstruction

ABSTRACT Dynamic surface reconstruction is a powerful route to boost oxygen evolution reaction activity, yet its typically uncontrolled nature often leads to rapid structural collapse under harsh conditions of seawater electrolysis. Herein, we introduce a programmable reconstruction strategy driven by the topological transformation of edge‐sharing octahedra‐rich Mn‐(FeCoNi) 3 Se 4 . This approach redirects destructive, abrupt reconstruction into an ordered, cascade phase transition pathway, where Fe sites are preferentially oxidized to α ‐FeOOH, then progressively evolve through β ‐NiOOH into the highly active γ ‐NiFeOOH. Such sequential evolution preserves structural integrity and, critically, activates a synergistic hydroxyl spillover mechanism. Density functional theory calculations reveal that the Fe sites efficiently capture * OH and spill over these species to adjacent Ni sites, facilitating O‐O coupling. Benefiting from this dual synergy, the catalyst delivers a low overpotential of 271 mV at 100 mA cm − 2 and ultra‐robust stability for over 1,000 h at 500 mA cm − 2 in alkaline seawater. This work presents a new paradigm for designing durable catalysts by precisely engineering reconstruction pathways through rational control of topology and reconstruction dynamics.