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.