Selective CO2 capture and conversion is an important tool in the fight against climate change. Industrially, CO2 is captured using a variety of aprotic solvents due to their high CO2 solubility and good thermal stability. Therefore, the electrochemical upgrade of CO2 to high value-added products in an aprotic medium could then boost the overall CO2 capture effectiveness. However, the effect of ion solvation and solvent selection in the CO2 reduction selectivity and current density within nonaqueous electrolytes remains unclear. Here, we show that bulk solvation behavior controls the CO2 reduction reaction and product distribution occurring at the catalyst-electrolyte interface. We investigate the ion solvation behavior and its effect on the CO2 reduction performance in glyme ethers and dimethyl sulfoxide (DMSO), which present relatively low and high dielectric constants respectively. Using spectroscopic techniques, we show that ion pair formation is prevalent in a low dielectric medium and is dependent on anion type. More importantly, we show as ion pair formation decreases within the electrolyte, CO2 current densities increases, and a higher CO Faradaic efficiency is observed at low overpotentials. Meanwhile, electrolytes dissolved in a high dielectric constant medium show small population of ion pairs and similar electrochemical behavior. By directly coupling bulk solvation to interfacial reactions and product distribution, we showcase the importance and utility of controlling the reaction microenvironment intuning electrocatalytic reaction pathways. This combined approach could enable novel electrolyte design for efficient and selective CO2 capture and conversion.

Probing electrolyte influence on CO2 reduction in aprotic solvents

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