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

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• The oxygen evolution reaction (OER) is crucial for renewable energy technologies.
• Cobalt-based hydroxides are promising OER electrocatalysts, but their performance needs improvement.
• Anionic modulation offers a pathway to tune catalyst properties.

Purpose of the Study:

• To investigate the mechanism of halide ion (F-/Cl-) modulation in cobalt-based hydroxides for OER.
• To synthesize phase-pure cobalt hydroxide compounds with controlled halide incorporation.
• To evaluate the impact of fluoride versus chloride on OER performance and catalyst properties.

Main Methods:

• Substrate-independent hydrothermal synthesis of Co(OH)2, Co(OH)F, and Co2(OH)3Cl.
• Electrocatalytic evaluation using glassy carbon electrodes.
• X-ray photoelectron spectroscopy (XPS) for electronic structure analysis.

Main Results:

• Fluoride ions demonstrate superior OER modulation compared to chloride ions.
• F- incorporation optimizes the electronic configuration of cobalt via ligand effects and Co → F electron transfer.
• F- guided anisotropic nanorod growth, reduced surface energy, and enhanced wettability.
• The engineered Co(OH)F catalyst achieved an overpotential of 318 mV at 10 mA/cm2 with excellent stability.

Conclusions:

• Fluoride ion incorporation is an effective strategy for enhancing OER activity in cobalt-based hydroxides.
• Electronic structure modulation and morphological control are key factors for improved catalytic performance.
• This study presents a synthetic approach for pure-phase Co(OH)F and highlights its potential as a high-performance OER catalyst.