From Flue Gas to Syngas: Composite Electrode Based on Ionic Liquid and Microporous Polymer for MEA‐Based CO 2 Electrolysis

Abstract The electrochemical CO 2 reduction reaction (ECO 2 R) offers a promising pathway to convert CO 2 into value‐added products. While catalyst advances remain crucial, gas‐diffusion electrodes (GDEs) architecture is equally vital in CO 2 electrolyzer design. Most ECO 2 R studies use pure CO 2 feeds, whereas industrial sources like flue gas contain ∼15% CO 2 , requiring costly purification. Eliminating this step demands electrolyzers that directly process impure streams via in situ separation. Here, we introduce a composite GDE (CGDE) featuring a thin CO 2 ‐selective interlayer of intrinsically microporous polymer (PIM‐1) reinforced with the CO 2 ‐philic ionic liquid [Emim][BF 4 ]. This layer selectively adsorbs CO 2 and suppresses N 2 /O 2 existence at the catalyst interface. In simulated flue gas (15% CO 2 , 5% O 2 in N 2 ), the CGDE with 20 wt% [Emim][BF 4 ]/PIM‐1 achieved >70% CO Faradaic efficiency (FE) at 100 mA cm − 2 , versus ∼20% FE for a pristine GDE. Multiphysics simulations confirmed effective CO 2 delivery through the selective layer, with minimal O 2 permeation. Cost estimation analysis indicates around 25% reduction in CO's minimum selling price using the integrated design and >50% under ideal performance metrics by eliminating compression/transport. These results demonstrate that advanced electrode design with CO 2 ‐selective interlayer enables direct mixed‐gas ECO 2 R, establishes key design criteria for selective layers, and significantly improves process economics.