Ultraefficient homogeneous catalyst for the CO 2 -to-CO electrochemical conversion

Abstract

A very efficient electrogenerated Fe⁰ porphyrin catalyst was obtained by substituting in tetraphenylporphyrin two of the opposite phenyl rings by ortho-, ortho'-phenol groups while the other two are perfluorinated. It proves to be an excellent catalyst of the CO₂-to-CO conversion as to selectivity (the CO faradaic yield is nearly quantitative), overpotential, and turnover frequency. Benchmarking with other catalysts, through catalytic Tafel plots, shows that it is the most efficient, to the best of our knowledge, homogeneous molecular catalyst of the CO₂-to-CO conversion at present. Comparison with another Fe⁰ tetraphenylporphyrin bearing eight ortho-, ortho'-phenol functionalities launches a general strategy where changes in substituents will be designed so as to optimize the operational combination of all catalyst elements of merit.