Changing Mechanisms for CO₂ Reduction to Formate Via Protonation of the Catalyst

Electrochemical reduction reaction of CO 2 (CO 2 RR) is a promising method to transform CO 2 to useful products for consumption such as formic acid, carbon monoxide, or methane. Simply increasing the driving force of a catalytic process to speed up the rate of CO 2 reduction is unviable because of the competing Hydrogen Evolution Reaction (HER) pathway and of increased energy cost. Controlling the reactivity of active intermediates is of substantial importance for such processes. [Fe 4 N(CO) 12 ] − is a formate selective electrocatalyst previously studied by our group and was modified through protonation and replacement of several CO ligands with triethylphosphines (PEt 3 ) to synthesize [HFe 4 N(PEt 3 ) 4 (CO) 8 ] . This PEt 3 substituted, pre-protonated analog of [Fe 4 N(CO) 12 ] − exhibits altered rates compared to a non-protonated analog which we attribute to a switch in mechanism. We further explore explanations for different rates despite similar “active intermediates” and similar driving force using Cyclic Voltammetry (CV).