Selective Ion Transport Regulation Enables High Current Density CO₂-to-C₂₊ Conversion in Acid

Electrochemical carbon dioxide reduction reaction (CO₂RR) under acidic condition offers great promise to achieve carbon-efficient CO₂ electrolysis. However, acidic CO₂RR has been hindered by the severe competing hydrogen evolution reaction (HER) and sluggish carbon–carbon coupling efficiency. Herein, an ion-transport regulation strategy has been developed to customize the microenvironment near cathode surface during high current density electrolysis in acidic electrolyte. A hybrid adlayer composed of (010) planes-enclosed ZrO₂ nanosheets and Nafion preferentially allows K⁺ transport toward cathode through proton trapping and Donnan effect, thus simultaneously enriching K⁺ and raising pH near cathode surface during CO₂RR. Such K⁺-rich and alkaline microenvironment suppresses HER and favors C₂₊ products formation. Particularly, a remarkable C₂₊ Faraday efficiency (FE) of nearly 81% has been achieved with a partial current density of 484 mA cm⁻² for C₂₊ products on modified Cu electrode. This work demonstrates an effective strategy to boost the CO₂RR performance in acidic electrolyzers for efficient and sustainable CO₂ conversion.