Elucidation of the selectivity of proton-dependent electrocatalytic CO ₂ reduction by fac -Re(bpy)(CO)₃Cl

A complete mechanism for the proton-dependent electrocatalytic reduction of CO₂ to CO by fac-Re(bpy)(CO)₃Cl that is consistent with experimental observations has been developed using first principles quantum chemistry. Calculated one-electron reduction potentials, nonaqueous pK _a's, reaction free energies, and reaction barrier heights provide deep insight into the complex mechanism for CO₂ reduction as well as the origin of selectivity for this catalyst. Protonation and then reduction of a metastable Re-CO₂ intermediate anion precedes Brønsted-acid- catalyzed C-O cleavage and then rapid release of CO at negative applied potentials. Conceptually understanding the mechanism of this rapid catalytic process provides a useful blueprint for future work in artificial photosynthesis.