Ampere-level CO<sub>2</sub> electroreduction to multi-carbon oxygenates in acidic electrolyte through surface microenvironment reconstruction.

Abstract

Efficient CO₂ electroreduction to multi-carbon (C₂₊) oxygenates in acidic electrolytes remains a great challenge, especially under high current density conditions. In this study, we prepare an ionic liquid (IL)-modified Cu electrode (IL@Cu), which achieve a Faradaic efficiency (FE) of 82.7% toward C₂₊ products at a current density of 2.0 A cm^-2 in 0.5 M K₂SO₄ (pH = 1, adjusted with H₂SO₄), with a single-pass carbon efficiency reaching 78.5%. Under the same conditions, the partial current density for C₂₊ oxygenates and ethanol exceed 1.2 A cm^-2 and 1.0 A cm^-2, respectively, over IL@Cu. Mechanism study has shown that K⁺ cations are repelled by the IL cations during the reaction, allowing water molecules to access the electrode surface. The displacement of K⁺ enhances C-C coupling, while the proximity of water to the electrode surface facilitates the incorporation of oxygen-containing intermediates into the hydrogen bond network, thereby promoting the formation of C₂₊ oxygenates.