Computational insights into electrocatalytic CO2 reduction facilitated by Mn(I) half sandwich-based catalysts: Role of substitution and solvent

Using the density functional theory (DFT) calculations, we have considered a series of Mn(I) half sandwich-based catalysts and explored the electrochemical CO₂ reduction to CO. Various substituents (NH₂, CMe₃, CH₃, OH and COOH) and solvent effects (acetonitrile, water and DMSO) have been studied to understand their roles in the CO₂ reduction reactions. For active catalyst formation, the substituent effect is found to be very significant for the second reduction potentials compared to the first reduction potentials. However, the solvent effect is significant for both the reduction potentials. The detailed investigations of our calculated results show that the formation of the active catalyst, CO₂ vs. proton binding, and formation/breaking of C–OH bond are the most important steps. The COOH substitution in the Mn(I) half sandwich-based catalyst is found to be more promising for the efficient formation/breaking of C–OH bond during CO₂ reduction reaction. The calculated results show that the reduction step is more favourable in DMSO followed by water and acetonitrile solvent whereas protonation step is more favourable in acetonitrile followed by water and DMSO solvent. As the electrochemical CO₂ reduction reaction contain both protonation and reduction steps the perfect solvent will be water.