Polymerization of Cobalt Porphyrin on Carbon Nanotubes for Efficient CO₂ Electrochemical Reduction

Cobalt porphyrin-based catalysts have drawn wide attention for their applications in the CO2 electrochemical reduction reaction (CO2RR) as they are robust, efficient, and noble-metal free. Herein, an innovative approach was employed for immobilization of cobalt tetra(4-ethynylphenyl)porphyrin (CoTEP) onto carbon nanotubes (CNTs) based on the formation of a covalent porphyrin framework by chemical polymerization via the Hay coupling reaction. The polymerized material (CoTEP@CNTs) exhibits an enhanced activity toward CO2-to-CO electroreduction with a specific Faradaic efficiency (FE) of 90% and turnover frequency (TOF) of 2.1 s–1 at the overpotential of 570 mV. To the best of our knowledge, this is one of the best polymerized porphyrins for CO2RR. Characterization results reveal that the polymerization of CoTEP on CNTs led to a more uniform layer of porphyrin molecules on the sidewalls of CNTs, thus leading to enhanced efficiency.