From Flue Gas to Syngas: Composite Electrode Based on Ionic Liquid and Microporous Polymer for MEA-Based CO2 Electrolysis.

The electrochemical CO2 reduction reaction (ECO2R) offers a promising pathway to convert CO2 into value-added products. While catalyst advances remain crucial, gas-diffusion electrodes (GDEs) architecture is equally vital in CO2 electrolyzer design. Most ECO2R studies use pure CO2 feeds, whereas industrial sources like flue gas contain ∼15% CO2, 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 CO2-selective interlayer of intrinsically microporous polymer (PIM-1) reinforced with the CO2-philic ionic liquid [Emim][BF4]. This layer selectively adsorbs CO2 and suppresses N2/O2 existence at the catalyst interface. In simulated flue gas (15% CO2, 5% O2 in N2), the CGDE with 20 wt% [Emim][BF4]/PIM-1 achieved >70% CO Faradaic efficiency (FE) at 100 mA cm- 2, versus ∼20% FE for a pristine GDE. Multiphysics simulations confirmed effective CO2 delivery through the selective layer, with minimal O2 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 CO2-selective interlayer enables direct mixed-gas ECO2R, establishes key design criteria for selective layers, and significantly improves process economics.