Mitigating Electrode Inactivation during CO 2 Electrocatalysis in Aprotic Solvents with Alkali Cations.

CO 2 electrochemical reduction (CO 2 R) in aprotic media is a promising alternative to aqueous electrocatalysis, as it minimizes the competing hydrogen evolution reaction while enhancing CO 2 solubility. To date, state-of-the-art alkali salts used as electrolytes for selective aqueous CO 2 R are inaccessible in aprotic systems due to the inactivation of the electrode surface from carbonate deposition. In this work, we demonstrate that an acidic nonaqueous environment enables sustained CO 2 electrochemical reduction with common alkali salts in dimethyl sulfoxide. Electrochemical and spectroscopic techniques show that at low pH carbonate buildup can be prevented, allowing CO 2 R to proceed. Product distribution with a copper electrode revealed up to 80% Faradaic efficiency for CO 2 R products, including carbon monoxide, formic acid, and methane. By understanding the mechanism for electrode inactivation in an aprotic medium and addressing that challenge with dilute acid addition, we pave the way toward the development of more efficient and selective electrolytes for CO 2 R.