Deciphering the Selectivity of the Electrochemical CO<sub>2</sub> Reduction to CO by a Cobalt Porphyrin Catalyst in Neutral Aqueous Solution: Insights from DFT Calculations
Yu‐Chen Cao, Le‐Le Shi, Man Li, Bo You, Rong‐Zhen Liao
Abstract
Abstract Density functional theory (DFT) calculations were conducted to investigate the cobalt porphyrin‐catalyzed electro‐reduction of CO 2 to CO in an aqueous solution. The results suggest that Co II −porphyrin (Co II −L) undertakes a ligand‐based reduction to generate the active species Co II −L⋅ − , where the Co II center antiferromagnetically interacts with the ligand radical anion. Co II −L⋅ − then performs a nucleophilic attack on CO 2 , followed by protonation and a reduction to give Co II −L−COOH. An intermolecular proton transfer leads to the heterolytic cleavage of the C−O bond, producing intermediate Co II −L−CO. Subsequently, CO is released from Co II −L−CO, and Co II −L is regenerated to catalyze the next cycle. The rate‐determining step of this CO 2 RR is the nucleophilic attack on CO 2 by Co II −L⋅ − , with a total barrier of 20.7 kcal mol −1 . The competing hydrogen evolution reaction is associated with a higher total barrier. A computational investigation regarding the substituent effects of the catalyst indicates that the CoPor−R3 complex is likely to display the highest activity and selectivity as a molecular catalyst.