Electrocatalytic reduction of low concentration CO₂

Area of Science:

• Electrochemistry
• Catalysis
• Environmental Chemistry

Background:

• Global warming and fossil resource depletion necessitate efficient carbon dioxide (CO2) utilization technologies.
• Directly utilizing low-concentration CO2 from industrial exhaust without energy-intensive concentration is highly desirable.
• Rhenium (Re) complexes show promise as catalysts for CO2 reduction.

Purpose of the Study:

• To develop a catalyst for direct electrocatalytic reduction of low-concentration CO2.
• To investigate the catalytic activity and selectivity of a Re(i)-complex with CO2-capturing ability.
• To understand the mechanism of CO2 insertion into the Re(i)-O bond.

Main Methods:

• Electrocatalytic reduction of CO2 using a Re(i)-complex catalyst in the presence of triethanolamine.
• Testing with varying CO2 concentrations (pure CO2, 10% CO2, 1% CO2) in argon gas.
• Analysis of reaction rate, faradaic efficiency, and selectivity of CO formation.
• Mechanistic investigation of CO2 insertion into the Re(i)-O bond.

Main Results:

• The Re(i)-complex catalyst demonstrated high selectivity (98%) for CO formation even at 10% CO2 concentration.
• Effective catalysis was observed at a low CO2 concentration of 1%, achieving 94% selectivity and 85% faradaic efficiency.
• The catalytic rate at 1% CO2 was 67% of that with pure CO2, indicating efficient CO2 capture and reduction.
• Electrocatalysis proceeds via CO2 insertion into the Re(i)-O bond within the complex.

Conclusions:

• The developed Re(i)-complex is an effective electrocatalyst for direct reduction of low-concentration CO2.
• This technology offers a promising pathway for CO2 utilization from industrial exhaust, mitigating global warming.
• The catalyst's ability to function efficiently at low CO2 concentrations bypasses the need for energy-intensive concentration steps.