Covalently Grafting Cobalt Porphyrin onto Carbon Nanotubes for Efficient CO2 Electroreduction

Highly dispersed: The covalent attachment of cobalt porphyrin onto carbon nanotubes is achieved by a substitution reaction at the metal center. This leads to large improvements in the efficiency of electrochemical CO₂ reduction compared to systems where the compounds are physically mixed.

Abstract

Molecular complexes with inexpensive transition‐metal centers have drawn extensive attention, as they show a high selectivity in the electrochemical conversion of CO₂ to CO. In this work, we propose a new strategy to covalently graft cobalt porphyrin onto the surface of a carbon nanotube by a substitution reaction at the metal center. Material characterization and electrochemical studies reveal that the porphyrin molecules are well dispersed at a high loading of 10 wt. %. As a result, the turnover frequency for CO formation is improved by a factor of three compared to traditional physically‐mixed catalysts with the same cobalt content. This leads to an outstanding overall current density of 25.1 mA cm⁻² and a Faradaic efficiency of 98.3 % at 490 mV overpotential with excellent long‐term stability. This work provides an effective pathway for the improvement of the performance of electrocatalysts that could inspire rational design of molecular catalysts in the future.

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