Rational Design of Polymers for Selective CO₂ Reduction Catalysis

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Developing efficient molecular catalysts for carbon dioxide (CO₂) reduction is crucial for sustainable energy solutions.
• Immobilizing molecular catalysts onto electrode surfaces is key for practical applications in electrocatalysis and photoelectrocatalysis.
• Controlling the microenvironment around a catalyst's active site can significantly influence its selectivity and activity.

Purpose of the Study:

• To synthesize and immobilize cobalt-terpyridine copolymers as molecular catalysts for CO₂ reduction.
• To engineer the outer coordination sphere of the cobalt catalyst within a polymer matrix to enhance CO₂ reduction selectivity.
• To evaluate the performance of these polymer-immobilized catalysts in electrochemical and photoelectrochemical CO₂ reduction.

Main Methods:

• Synthesis of terpyridine-containing copolymers with phosphonate anchoring groups.
• Immobilization of the synthesized copolymers onto porous metal oxide electrodes.
• Electrochemical and photoelectrochemical characterization of CO₂ reduction performance.
• Analysis of product selectivity (CO:H₂ ratio) using gas chromatography.

Main Results:

• Successful immobilization of cobalt-coordinated polymers onto electrode surfaces via phosphonate groups.
• Demonstrated electrochemical and photoelectrochemical CO₂ reduction using the hybrid cathodes.
• Achieved a CO:H₂ product ratio of up to 6:1 with the polymer-immobilized catalyst, significantly higher than the 2:1 ratio for the monomeric catalyst.
• Engineered hydrophobic functional moieties within the polymer matrix improved CO₂ reduction selectivity in aqueous media.

Conclusions:

• The developed polymer platform provides a versatile method for immobilizing and tuning molecular catalysts.
• Engineering the catalyst's outer coordination sphere within a polymer matrix is an effective strategy to enhance CO₂ reduction selectivity.
• This approach shows promise for creating efficient and selective artificial CO₂ reductases.