Covalently Grafting Cobalt Porphyrin onto Carbon Nanotubes for Efficient CO₂ Electroreduction

Molecular complexes with inexpensive transition metal center have drawn extensive attention as they exhibit high selectivity for electrochemical CO₂ to CO conversion. In this work, we propose a new strategy to covalently graft cobalt porphyrin onto the surface of carbon nanotube through a substitution reaction at metal centers. Material characterization and electrochemical studies revealed that porphyrin molecules were well dispersed at a high loading of 10 wt. As a result, the turnover frequency for CO formation was improved by a factor of three than a traditional physically mixed catalyst at 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.