Harnessing Active Protons through Parasitic Oxygen Evolution Reaction for Selective Electrochemical CO ₂ Reduction in Aprotic Media

Electrochemical reduction of CO 2 is highly sensitive to the local microenvironment around the catalytic active sites. Despite substantial progress in the development of efficient catalysts for CO 2 conversion to value-added products, achieving hydrogenated CO 2 reduced products in aprotic electrolytes is challenging due to the limited availability and controlled delivery of proton sources. Herein, we present a strategy for the electrochemical reduction of CO 2 to formate through electrochemical environment engineering, which facilitates hydrogenated product formation without the addition of any protic solvent. A decoupled proton generation protocol enables controlled ex situ proton transport from the anodic to the cathodic compartment. Aprotic and aqueous solvents used as catholytes and anolytes, respectively (TBA–H + ), show a high Faradaic efficiency of 93.2% toward formate, accompanied by significant suppression of the competing hydrogen evolution reaction (HER). This enhanced performance is attributed to the continuous and regulated proton flux originating from the anodic compartment via acidic oxygen evolution reaction (OER).