(544hg) Effects of Electrolyte Composition on Electrochemical CO2 Reduction

The composition of the electrolyte in which electrocatalysts are tested is known to influence the electrochemical reduction of CO₂; however, detailed understanding of these effects is still lacking. Here we present a combination of experimental and theoretical studies of the effects of electrolyte cation and anion identity on the activity and selectivity of metal catalysts for the reduction of CO₂. Effects of electrolyte composition on the intrinsic kinetic of the reaction are distinguished from mass transport effects. Density functional theory calculations show that the effect of the presence of alkali metal cations can be understood in terms of electrostatic interactions between solvated cations and adsorbed species with large dipole moments, while trends in activity with cation size arise from additional chemical interactions for larger cations. The effect of anions on CO₂ reduction rates can be understood in terms of the hydrogen donation ability of the most willing donor in solution.