Mechanistic insight into electrocatalytic CO2 reduction using Lewis acid-base pairs

[Display omitted] •Zn(cyclam)]2+ co-catalyst increases the activity of ReI(bpy) catalyst for CO2 reduction.•Zn(cyclam)]2+ significantly decreased the required overpotential for CO2 reduction.•The CO2 binding energy to the ReI(bpy) catalyst is stabilized by Zn(cyclam)]2+. In this study, fac-[Re(bpy)(CO)3Cl] (bpy = 2,2′-bipyridine) is used as a Lewis base catalyst and [Zn(cyclam)]2+(cyclam = 1,4,8,11-tetraazacyclotetradecane) is used as a Lewis acid co-catalyst. The thermodynamic effect of the [Zn(cyclam)]2+ on the redox activity of the ReI(bpy) catalyst for CO2 reduction has been investigated experimentally using cyclic voltammetry and computationally using density functional theory (DFT). Both experimental and computational results reveal that [Zn(cyclam)]2+ facilitates the Cl− ion dissociation by forming an inner-sphere interaction. As a result, the addition of [Zn(cyclam)]2+ shifts the ReI(bpy) first reduction to less negative potential, enabling the catalyst to be activated with less energy input. Moreover, we are proposing that [Zn(cyclam)]2+ decreases the CO2 reduction overpotential by the ReI(bpy) complex by stabilizing the CO2 binding energy.