Well-Defined Single-Atom Cobalt Catalyst for Electrocatalytic Flue Gas CO₂ Reduction

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• Electrochemical reduction of carbon dioxide (CO2) is a promising route for CO2 utilization and renewable energy storage.
• Developing highly active and selective catalysts is crucial for efficient CO2 electroreduction.
• Single-atom catalysts offer unique electronic properties and high atom utilization for catalytic applications.

Purpose of the Study:

• To synthesize and characterize a single-atom cobalt catalyst (Co-Tpy-C) for electrochemical CO2 reduction.
• To evaluate the catalytic performance of Co-Tpy-C for CO2 reduction to CO in aqueous electrolyte.
• To investigate the catalytic mechanism and the role of single-atom cobalt sites.

Main Methods:

• Synthesis of Co-Tpy-C catalyst via pyrolysis of a cobalt terpyridine (Tpy) organometallic complex.
• Electrochemical characterization including cyclic voltammetry and chronoamperometry.
• Gas chromatography for product analysis and Faradaic efficiency determination.
• Density functional theory (DFT) calculations to elucidate the catalytic mechanism.

Main Results:

• Co-Tpy-C exhibited excellent activity for CO2 reduction, achieving over 95% CO Faradaic efficiency (FE) between -0.7 and -1.0 V vs RHE.
• The catalyst maintained high CO FE (>90%) even when using simulated flue gas (15% CO2).
• Gas phase flow electrolysis demonstrated a high CO partial current density of 86.4 mA cm-2 with >90% CO FE at 3.4 V cell voltage.
• DFT calculations and experimental results indicated that uniform single-atom Co-N4 sites are responsible for the high catalytic activity.

Conclusions:

• Single-atom Co-Tpy-C is a highly active and selective catalyst for electrochemical CO2 reduction to CO.
• The catalyst shows excellent performance under conditions relevant to industrial applications, including the use of flue gas.
• The well-defined single-atom Co-N4 sites are key to the catalyst's superior performance in CO2 electroreduction.