Synergistic Chalcogenate and Fluorine Engineering on Metal Oxyhydroxides Breaks the OER Scaling Relationship.

The oxygen evolution reaction (OER), a bottleneck in electrochemical water splitting, is fundamentally limited by a scaling relationship between the binding energies of key intermediates (OH* and OOH*), imposing a minimum theoretical overpotential of 0.37 eV. Breaking this scaling relationship is crucial for enhancing OER activity, yet effective strategies remain scarce. We demonstrate that the introduction of high-electronegativity fluorion on chalcogenate-adsorbed nickel-iron oxyhydroxide (NiFeOOH) significantly shortens hydrogen bonds between the chalcogenate and OER intermediates (*OH and *OOH). This shortening promotes proton transfer kinetics and lowers the theoretical overpotential to 0.27 eV. Guided by these calculations, the co-adsorption of chalcogenate and fluorion on metal oxyhydroxide (NiFeSF-R) catalyst is synthesized, and it achieves 1.0 A cm at an ultralow overpotential of 304 mV in 1.0 M KOH, a substantial improvement of 106 and 182 mV compared to NiFeS-R and NiFe, respectively. Notably, NiFeSF-R exhibits exceptional stability, sustaining 1.0 A cm for over 500 h with negligible degradation. In an anion exchange membrane water electrolyzer, the NiFeSF-R anode stably achieves 1.0 A cm at 1.73 V for 700 h at 50 °C. This work highlights the potential of local coordination environment tuning to break scaling relationships for high-performance OER catalysts.