Fluorine‐Modulated Hierarchical NiFeCo‐LDHs for Efficient and Stable Bifunctional Water Splitting in Alkaline and Seawater Media

This work synthesized a hierarchical-structured nickel-iron-cobalt layered double hydroxide (NiFeCo-LDHs) with heterointerfaces via a controllable hydrothermal method. The ternary metal system optimized the charge transport pathways through atomic-level synergy specifically the multivalent synergy. Furthermore, the high electronegativity of fluorine modulated the electronic conduction kinetics of NiFeCo-LDHs. Electrochemical testing demonstrated that, Owing to Ni²⁺ doping and fluorine atom modulation of LDH interlayer spacing, the NiFeCo-LDHs exhibited significantly enhanced hydrogen evolution reaction (HER) performance in 1.0 M KOH electrolyte. The HER overpotential is 74.3 mV at a current density of -10 mA cm^-2. As a bifunctional electrode, it required an OER overpotential of only 204.3 mV to achieve 10 mA cm^-2, and its stability remains robust even after 12 h of cycling. Notably, the catalyst maintains impressive performance for both HER and OER in seawater environments.