Microenvironment regulation for high-performance acidic CO₂ electroreduction on Poly(ionic liquid)-modified Cu surface

Electrocatalytic reduction of CO₂ (CO₂RR) under acidic conditions provides a feasible way for converting CO₂ to multi-carbon products (C₂₊) with high feedstock conversion and high energetic efficiency (EE). In this work, poly(ionic liquid) (PIL)-Cu hybrids were employed as excellent acidic CO₂RR electrocatalysts. A high faradaic efficiency towards C₂₊ products (FE_C2+) of more than 61.0 % was achieved within a wide pH range from 2 to 14 at –700 mA cm^–2. The optimum FE_C2+ of 83.1 % was obtained at –700 mA cm^–2 and pH = 2, corresponding to an EE_C2+ of 37.6 %. By reducing the inlet CO₂ flow rate to 1.59 mL min^–1, a very high CO₂ single-pass conversion of 98.7 % was achieved at –300 mA cm^–2. The confinement of PIL layer caused by the semi-rigid abundant porous structure and dense cationic-anionic network enables the maintenance of a moderate local alkaline microenvironment and enrichment of K⁺ cations at the active sites. These effects jointly promote the C–C coupling at the Cu-PIL interface under acidic conditions. Remarkably, the CO₂RR pathway can be regulated by functionality and morphology of the PIL layer.