Highly Selective and Stable Covalent Organic Framework Electrocatalysts for Sustainable Chlorine Evolution

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• The electrochemical chlorine evolution reaction (CER) is vital for the chlor-alkali industry.
• The competing oxygen evolution reaction (OER) and reliance on metal-based catalysts hinder current CER efficiency.
• Dimensionally stable anodes (DSAs) are common but have limitations.

Purpose of the Study:

• To develop and evaluate metal-free covalent organic frameworks (COFs) as efficient electrocatalysts for CER.
• To compare the performance of COFs against traditional catalysts like DSAs.
• To elucidate the active sites and mechanism responsible for the enhanced CER activity.

Main Methods:

• Synthesis of a series of metal-free covalent organic frameworks (Tp-Pa-COFs).
• Electrochemical characterization including overpotential, selectivity, and stability tests at 90 °C.
• Operando characterization and theoretical calculations to identify active sites and reaction mechanisms.

Main Results:

• Tp-Pa-COFs exhibited significantly lower overpotential (102 mV) for CER compared to DSA (182 mV) at 400 mA cm⁻².
• Achieved superior CER selectivity (100 ± 4%) and long-term stability (over 200 h).
• Identified carbonyl and amine groups as active sites, enabling preferential Cl⁻ adsorption and breaking the CER-OER scaling relationship.

Conclusions:

• Metal-free Tp-Pa-COFs show exceptional activity and stability for the electrochemical chlorine evolution reaction.
• These COF-based materials present a sustainable and efficient alternative to metal-based catalysts for industrial chlorine production.
• The findings advance the development of novel metal-free electrocatalysts for critical industrial processes.