Catalyst Aggregation Matters for Immobilized Molecular CO₂RR Electrocatalysts

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• Immobilized molecular electrocatalysts are key for carbon dioxide reduction reaction (CO2RR).
• Catalyst aggregation can significantly alter the observed performance and mechanistic understanding of CO2RR.

Purpose of the Study:

• To investigate the effect of catalyst aggregation on the behavior of immobilized cobalt phthalocyanine (CoPc) during CO2RR.
• To develop strategies for engineering improved molecular electrocatalysts for CO2RR in flow cells.

Main Methods:

• Utilized *operando* Raman spectroscopy to study CO2RR on immobilized CoPc in an electrochemical flow reactor.
• Analyzed the influence of catalyst aggregation on CoPc oxidation state and catalytic activity.

Main Results:

• Demonstrated that CoPc oxidation state during electrolysis depends on aggregation.
• Showed that dispersed catalysts on conductive supports are essential for reliable CO2RR performance data.
• Engineered an improved catalyst, EtO8-CoPc, achieving high selectivity (≥95% FE_CO), current density (≥300 mA/cm2), and durability.

Conclusions:

• Accurate identification of active species in molecular catalysts requires *operando* spectroscopy and consideration of aggregation.
• Dispersed molecular catalysts are vital for efficient CO2RR in flow cells.
• The metal center of CoPc is the active site for CO2RR catalysis in flow cells.