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

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.