Enhanced Electrochemical Reduction of CO2 to CO upon Immobilization onto Carbon Nanotubes Using an Iron‐Porphyrin Dimer

Electrochemical reduction of carbon dioxide (CO2) is a viable solution for conversion of atmospheric CO2 to value‐added materials such as carbon monoxide (CO). In this project, a new urea iron‐tetraphenylporphyrin‐dimer (Fe‐TPP‐Dimer) was synthesized and applied for electrocatalytic CO2 reduction under both homogeneous and heterogeneous conditions to selectively reduce CO2 to CO. Immobilization of the catalyst onto carbon nanotubes (CNTs) in aqueous solution resulted in remarkable enhancement of its electrocatalytic abilities, with exceptional turnover frequencies (10 s−1), high faradic efficiency (FE) of ∼90%, and a current density of 16 mA/cm2 at −0.88 V vs. RHE. This project exhibits the importance of molecular design in accessing heterogeneous applications with CNTs. A systematic electrocatalytic activity of iron‐urea‐porphyrin (Fe‐TPP‐Dimer) as both homogeneous and heterogeneous catalysts were developed and investigated. The Fe‐TPP‐Dimer was found to yield optimal electrocatalytic activity towards selectively reducing CO2 to CO with the faradic efficiency (FE) of 90% upon immobilization onto carbon nanotubes (CNTs). We conclude that introduction of an additional porphyrin ring enhances its catalytic efficiency via a dual active site approach.