Tailoring interfacial proton-coupled electron transfer via electrolyte engineering for high-selectivity H₂O₂...

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• Electrolyte design is crucial for controlling electrochemical reactions, particularly the oxygen reduction reaction (ORR).
• Understanding electrolyte-mediated regulation of interfacial microenvironments at the atomic scale is essential for optimizing ORR pathways.
• Selective electrosynthesis of hydrogen peroxide (H$_{2}$O$_{2}$) via ORR is a key goal for sustainable chemical production.

Purpose of the Study:

• To elucidate the atomic-scale mechanisms by which acetonitrile (ACN) additive tailors the alkaline ORR pathway.
• To demonstrate how ACN promotes selective H$_{2}$O$_{2}$ electrosynthesis on carbon catalysts.
• To establish the structure-activity relationship between electrolyte composition and interfacial microenvironment for H$_{2}$O$_{2}$ production.

Main Methods:

• Integrated molecular dynamics simulations.
• In situ spectroscopy.
• Electrochemical impedance analysis.

Main Results:

• ACN additive optimizes the three-phase interface, enhancing ORR activity.
• ACN restructures interfacial water by displacing water in cationic solvation shells and disrupting hydrogen bonding.
• ACN mitigates interfacial proton/electron flooding and enhances proton-coupled electron transfer kinetics, achieving 90% H$_{2}$O$_{2}$ selectivity (vs. 60% for KOH alone).

Conclusions:

• ACN additive provides a novel strategy for sustainable H$_{2}$O$_{2}$ electrosynthesis by precisely controlling the interfacial microenvironment.
• The study establishes a clear link between electrolyte composition, interfacial water structure, and ORR pathway selectivity.
• This work offers a pathway for designing advanced electrolytes for targeted electrochemical synthesis.