Phase-Dependent Reprogramming of Co–O Bonds in Fe-Doped Cobalt Molybdate for Durable Oxygen Evolution Reaction

Abstract Dynamic reconstruction enables active oxyhydroxide formation in alkaline oxygen evolution reaction pre-catalysts but often induces overoxidation and degradation when uncontrolled. Herein, Fe-doped cobalt molybdate microrod arrays (FCMO) are developed as a durable OER pre-catalyst featuring phase-dependent Co–O bond reprogramming mediated by Fe–O–Co motifs. Fe incorporation preserves the parent Co(MoO4)·0.75H2O framework while dual-regulating Co–O interactions, weakening them in the precursor to facilitate controllable reconstruction, then strengthening them in the reconstructed FeCoOOH to suppress Co overoxidation. Density functional theory confirms that Fe optimizes the adsorption energetics of oxygenated intermediates and lowers the barrier for the *O-to-*OOH conversion step. FCMO delivers overpotentials of 192, 246, and 338 mV at 10, 100, and 500 mA cm–2 in 1 M KOH, remains stable for 1000 h at 1000 mA cm–2, and delivers 500 mA cm–2 at 1.72 V in an anion exchange membrane water electrolyzer (60 °C, 200 h). This work establishes phase-dependent Co–O bond switching as a strategy to reconcile activation speed with durability in reconstructive OER electrocatalysts.