Enhanced electrocatalytic CO₂ reduction performance of Co-porphyrin derivatives supported on CNTs with methylation of the hydroxyl and carboxyl groups

Metal-porphyrin complexes with a well-defined M-N4 structure are a class of electrocatalyst materials that can be reasonably designed to exhibit high electrochemical carbon dioxide reduction (CO2RR) performance. The substituent effect of metal-porphyrin complexes plays an important role in CO2RR. Herein, Co-porphyrins with different substituents of -COOCH3, -OCH3, -COOH, and -OH (denoted as CoTCMePP, CoTOMePP, CoTCPP, and CoTOPP) were prepared and uniformly anchored on carbon nanotubes. CoTCMePP/CNTs exhibited a higher FE (CO) of 94.5% with a current density of 12.9 mA cm(-2) and a TOF of 705 h(-1) at -0.77 V versus RHE in 0.5 M KHCO3 than that of CoTCPP/CNTs. Meanwhile, the performance of CoTOMePP/CNTs was superior to CoTOPP/CNTs in FE (CO) and stability. The methylated derivatives exhibited enhanced electrocatalytic CO2 reduction performance, for the methylation of the hydroxyl and carboxyl might increase the solubility and suppress the aggregation of metal-porphyrin, helping Co-porphyrins disperse on the carbon nanotubes better.