Boosting Current Density of Electrocatalytic CO₂ Reduction using Metal-Enzyme Hybrid Cathodes

Area of Science:

• Electrochemistry
• Catalysis
• Environmental Science

Background:

• Electrocatalytic reduction of carbon dioxide (CO2RR) is a promising strategy for mitigating global warming and producing liquid fuels.
• A major hurdle in industrial CO2RR is the mass transfer limitation of CO2, which impedes high current densities.
• Developing efficient catalysts is crucial for advancing CO2RR technologies.

Purpose of the Study:

• To develop a novel enzyme-enhanced electrocatalysis platform to overcome CO2 mass transfer limitations.
• To improve the current density of CO2RR for enhanced liquid fuel production.
• To investigate the synergistic effects of enzymes and metal catalysts in CO2 electroreduction.

Main Methods:

• Integration of bovine carbonic anhydrase (bCA) stabilized on carbon nanotubes (bCA@CNT) with tin (Sn) and bismuth (Bi) metal catalysts.
• Preparation of Metal-bCA (M-bCA) hybrid cathodes.
• Electrochemical characterization using membrane-electrode assembly (MEA)-type and 3-compartment cells.

Main Results:

• The bCA enzyme dynamically enhances local CO2 regeneration from bicarbonate at the cathode surface.
• Sn-bCA cathodes showed a 3.3-fold increase in formate current density compared to bare Sn cathodes.
• Bi-bCA cathodes achieved a 1.5-fold higher current density (442 mA cm-2) for formic acid production.

Conclusions:

• The enzyme-enhanced electrocatalysis platform effectively boosts CO2RR current density by addressing mass transfer limitations.
• The M-bCA hybrid cathodes demonstrate significant potential for efficient and concentrated formic acid production.
• This approach offers a viable pathway for industrial CO2RR applications in sustainable fuel synthesis.