Operando insights on stable Cu²⁺ active sites for efficient electrochemical CO₂-to-C₂H₄ conversion

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• Copper catalysts are crucial for electrochemical CO2 conversion to C2+ products.
• Catalyst surface oxidation states dictate product selectivity.
• Conventional copper catalysts often reduce to Cu1+ or Cu0 during CO2 reduction.

Purpose of the Study:

• To develop a strategy for stabilizing Cu2+ ions in copper catalysts.
• To create a metal-organic polymer (CuBBTA) for enhanced CO2 electroreduction.
• To investigate the catalytic performance and mechanism of CuBBTA for CO2-to-ethylene conversion.

Main Methods:

• Synthesis of a copper-benzobistriazole metal-organic polymer (CuBBTA).
• Electrochemical characterization including Faradaic efficiency and power conversion efficiency measurements.
• Operando spectroscopy (X-ray absorption, Raman, ATR-SEIRAS) and DEMS for mechanistic studies.
• Theoretical calculations to understand intermediate formation.

Main Results:

• CuBBTA achieved a high Faradaic efficiency of 62.0% for CO2 to C2H4 conversion.
• The catalyst demonstrated a half-cell power conversion efficiency of 34.4% in a flow cell.
• Stable operation exceeding 50 hours with Faradaic efficiency >55% was observed.
• Operando studies confirmed structural stability and revealed the role of adjacent Cu2+ sites in forming the *COCHO intermediate.

Conclusions:

• Stabilizing Cu2+ ions via coordination with benzobistriazole (H2BBTA) is an effective strategy.
• The CuBBTA catalyst enables efficient and stable electrochemical CO2-to-ethylene conversion.
• The neighboring Cu2+ sites facilitate the formation of a key intermediate, leading to high ethylene selectivity.