Fluorine Mediates the Deprotonation Pathway over Ruthenium Oxide for Stable Water Electrolysis

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Ruthenium oxide (RuO2) is a potential anode catalyst for proton exchange membrane water electrolysis (PEMWE), but suffers from poor stability and slow oxygen evolution reaction (OER) kinetics.
• Existing RuO2 catalysts face an activity-stability paradox, limiting their practical application in PEMWE.

Purpose of the Study:

• To develop a fluorine-tuned RuO2 catalyst that addresses the activity-stability paradox for OER in PEMWE.
• To elucidate the mechanism of fluorine's role in enhancing catalyst performance and stability.

Main Methods:

• Synthesis of fluorine-tuned RuO2 with terminal (Fter) and bridging (Fbri) fluorine sites.
• Comprehensive experimental characterization and theoretical calculations.
• Electrochemical testing in PEMWE, including overpotential measurements and long-term stability tests.

Main Results:

• The fluorine-tuned RuO2 exhibited an unconventional fluorine-assisted deprotonation mechanism, decoupling proton and electron transfer during OER.
• Fter sites acted as proton relays, accelerating intermediate deprotonation, while Fbri sites suppressed lattice oxygen oxidation.
• The catalyst achieved a low overpotential (191 mV at 10 mA/cm²) and maintained stability over 2000 hours.
• A PEMWE device using this catalyst reached 1000 mA/cm² at 1.72 V and operated stably for over 300 hours.

Conclusions:

• Fluorine tuning of RuO2 effectively resolves the activity-stability trade-off for OER catalysts in PEMWE.
• The identified fluorine-assisted mechanism offers a new strategy for designing advanced electrocatalysts.
• The developed catalyst demonstrates significant potential for efficient and durable hydrogen production via water electrolysis.