Fluoride-Mediated Synthesis of Co(OH)F and Electronic Structure Optimization for Enhanced Water Oxidation Performance

This study deciphers the anionic modulation mechanism of halide ions (F−/Cl−) in cobalt-based hydroxides for oxygen evolution reaction (OER). Phase-pure Co(OH)2, Co(OH)F, and Co2(OH)3Cl were fabricated via substrate-independent hydrothermal synthesis to eliminate conductive support interference. Electrocatalytic evaluation on glassy carbon electrodes demonstrates fluoride’s superior regulatory capability over chloride. X-ray photoelectron spectroscopy (XPS) analyses revealed that F− incorporation induces charge redistribution through Co → F electron transfer, optimizing the electronic configuration via ligand effects. F− incorporation simultaneously guided the anisotropic growth of 1D nanorods and reduced surface energy, thereby enhancing the wettability of Co(OH)F. The engineered Co(OH)F catalyst delivers exceptional OER performance: 318 mV overpotential at 10 mA/cm2 in 1 M KOH with 94% current retention over 20 h operation. This study provides a synthetic strategy for preparing pure-phase Co(OH)F and compares halide ions’ effects on enhancing OER activity through electronic structure modulation and morphological control of basic cobalt salts.