Redox "Innocence" of Re(I) in Electrochemical CO₂ Reduction Catalyzed by Nanographene-Re Complexes

Improving energy efficiency of electrocatalytic CO₂ conversion to useful chemicals poses a significant scientific challenge. Recently we reported on using a colloidal nanographene as the diimine ligand to form a molecular complex Re(diimine)(CO)₃Cl to tackle this challenge, leading to significantly improved CO₂ reduction potential. In this work, we use theoretical computations to investigate the roles of the nanographene ligand in the reduction and the reaction pathways. Remarkably, our results show that the metal center merely provides a binding site for CO₂ and a conduit for electron transfer between the nanographene ligand and the substrate instead of changing its own oxidation state in the processes. Thus, despite its multiple oxidation states, the Re is redox "innocent" in the CO₂ reduction catalyzed by the nanographene complex.