The role of organic cations in the electrochemical reduction of CO2 in aprotic solvents

The electrochemical reduction of CO2 is sensitive to the microenvironment surrounding catalytic active sites. Although the impact of changing electrolyte composition on CO2 reduction kinetics in aqueous electrolytes has been studied intensively, less is known about the influence of the electrochemical environment in non-aqueous solvents. Here, we present data demonstrating that organic alkyl ammonium cations influence catalytic performance in non-aqueous media and describe a physical model that rationalizes these observations. Using results from a combination of kinetic, spectroscopic, and computational techniques, we argue that the interfacial electric field present at the catalyst surface is sensitive to the molecular identity of the organic cation in the aprotic electrolyte. This is true irrespective of solvent, electrolyte ionic strength, or the supporting electrolyte counter anion. Our results suggest that changes in the interfacial field can be attributed to differences in the cation-electrode distance. Changes in the electric field strength are consequential to CO2R to CO as they modify the energetics of the kinetically relevant CO2 activation step.