Oxygen functionalization of carbon quantum dots enables efficient acidic hydrogen peroxide electrosynthesis

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• Electrocatalytic synthesis of hydrogen peroxide (H2O2) is limited by low activity in acidic media.
• Understanding active sites in carbon-based electrocatalysts for H2O2 production is crucial but lacking.

Purpose of the Study:

• To elucidate the role of sp3-hybridized carbon active sites and oxygen functional groups (aldehyde, hydroxyl, carboxyl) in acidic O2-to-H2O2 conversion.
• To achieve industrially relevant H2O2 production rates using engineered carbon quantum dots (CQDs).

Main Methods:

• Utilized well-defined zero-dimensional carbon quantum dots (CQDs) with engineered edge-site oxygen functional groups.
• Integrated CQDs into a solid-state electrolyte electrolyzer.
• Employed theoretical modeling and calculations to analyze reaction mechanisms.

Main Results:

• Achieved Ampere-level current densities for H2O2 electrosynthesis.
• Obtained up to 99.03% Faradaic efficiency and 3.0 μmol s-1 cm-2 production rate with CQDs-CHO.
• Demonstrated that functionalization reconfigures carbon edge sites, influencing oxygenated intermediate adsorption.

Conclusions:

• Engineered CQDs with specific functional groups significantly enhance acidic O2-to-H2O2 conversion.
• Electron-withdrawing functional groups are critical for improving charge transfer kinetics and H2O2 electrosynthesis efficiency.
• Provides atomic-level insights into active sites for efficient H2O2 production.