Electrocatalytic Properties of meso- Perfluorinated Metallo Corroles for the Reduction of CO2

Abstract

Tetrapyrrolic containing metal complexes are among the most efficient molecular catalysts for the CO₂ reduction. Metalloporphyrins and phthalocyanines are currently under investigations and their catalytic properties are among the best molecular catalysts. Corrole, a contracted tetrapyrrolic macrocycle has been also used to design molecular for the CO₂ reduction. The electrochemical activity towards CO₂ reduction can rival those of their porphyrin analogues. However, the catalytic activity of the metallocorrole is initiated at the corresponding M^II/I couple. Accordingly, a catalytic current in presence of CO₂ with cobalt corrole appears when the Co^I species is generated. We have designed an electron deficient A₂B corrole holding two −CF₃ groups and a benzonitrile in the meso positions and its cobalt complex (1). We reasoned that these groups could shuffle the redox potentials to reach the M(I) oxidation states at more positive values thereby lowering the overpotential for the catalytic CO₂ reduction. Our results clearly show that catalyst 1 when adsorbed on a carbon electrode, shows the most favourable catalytic performance for CO production, achieving an efficiency of 85 % with a current density of −1.5 mA cm⁻² at −1.0 V vs NHE. The current densities of controlled potential electrolysis with increasing amount of KHCO₃, were found to increase more than one order of magnitude with the formation of MeOH.