Modulating Core Polarity in Metal-free Covalent Organic Frameworks for Selective Electrocatalytic Hydrogen Peroxide...

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Optimizing the two-electron oxygen reduction reaction (ORR) for hydrogen peroxide (H2O2) production requires precise control of active site charge density.
• Covalent organic frameworks (COFs) offer tunable electronic properties for catalytic applications.

Purpose of the Study:

• To investigate the impact of intermolecular polarity within COFs on the efficiency and selectivity of electrochemical H2O2 production.
• To correlate the electronic properties of COF building blocks with their catalytic performance in ORR.

Main Methods:

• Synthesis of C3 symmetric COFs with varying core structures (benzene vs. triazine) to modulate polarity.
• Electrochemical evaluation of H2O2 production selectivity and efficiency.
• In-situ electrochemical Raman spectroscopy and scanning electrochemical microscopy (SECM) for mechanistic insights.

Main Results:

• Benzene-cored COFs, with reduced polarity, demonstrated superior performance compared to triazine-cored COFs.
• Achieved 93.1% H2O2 selectivity at 0.4 V with 90.5% faradaic efficiency, indicating a near two-electron transfer process.
• SECM and in-situ Raman spectroscopy confirmed localized H2O2 generation and highlighted the role of core polarity.

Conclusions:

• Intermolecular polarity in COFs is a critical factor in tuning catalytic activity for selective H2O2 production.
• The benzene-cored COF serves as an effective electrocatalyst for efficient and selective H2O2 synthesis via the two-electron ORR.
• Understanding and controlling core polarity in COFs opens new avenues for designing advanced electrocatalysts.