Homogeneous Electrochemical Reduction of CO₂ to CO by a Cobalt Pyridine Thiolate Complex

The chemical and electrochemical reduction of CO₂ to value added chemicals entails the development of efficient and selective catalysts. Synthesis, characterization and electrochemical CO₂ reduction activity of a air-stable cobalt(III) diphenylphosphenethano-bis(2-pyridinethiolate)chloride [{Co(dppe)(2-PyS)₂}Cl, 1-Cl] complex is divulged. The complex reduces CO₂ under homogeneous electrocatalytic conditions to produce CO with high Faradaic efficiency (FE > 92%) and selectivity in the presence of water. Through detailed electrochemical investigations, product analysis, and mechanistic investigations supported by theoretical calculations, it is established that complex 1-Cl reduces CO₂ in its Co(I) state. A reductive cleavage leads to a dangling protonated pyridine arm which enables facile CO₂ binding through a H-bond donation and facilitates the C-O bond cleavage via a directed protonation. A systematic benchmarking of this catalyst indicates that it has a modest overpotential (∼180 mV) and a TOF of ∼20 s^-1 for selective reduction of CO₂ to CO with H₂O as a proton source.