Flooding-resistant gas diffusion electrode design for MEA-type CO2 electrolyzer

The electrocatalytic CO 2 reduction reaction (CO 2 RR) powered by renewable electricity offers a sustainable pathway for converting CO 2 into valuable products, presenting a promising strategy to mitigate atmospheric CO 2 concentrations. The design of gas diffusion electrodes (GDEs) plays a crucial role in enhancing the CO 2 RR performance and stability in membrane-electrode assembly (MEA)-type electrolyzers. One of the primary challenges in industrializing CO 2 RR technologies is the flooding of GDEs, which significantly reduces the stability of CO 2 RR performance. Here, we design a flooding-resistant GDE by incorporation of macrochannels into GDE employing a nickel (Ni) foam substrate to mitigate GDE flooding and improve CO 2 RR performance and stability. The macrochannels in Ni foam-based GDE ensure sufficient mass transfer of CO 2 to the catalyst layer and the discharge of electrolyte, thereby minimizing the GDE flooding. The Ni foam based-GDE exhibits significantly higher through-plane conductivity and gas permeability compared to conventional carbon paper-based GDEs and retains hydrophobicity even after prolonged operation. This GDE demonstrates higher CO current density ( j CO ) and lower cell voltage, maintaining excellent stability with a high CO Faradaic efficiency (FE CO ) of 88.4 % over 50 h of continuous operation. These findings emphasize the importance of GDE designs with enhanced mass transfer capabilities to effectively address flooding challenges and improve the efficiency of CO 2 RR in MEA-type electrolyzers. A flooding-resistant GDE design, engineered with macrochannels, ensures efficient CO 2 mass transport to the catalyst layer while effectively addressing electrolyte flooding challenges. • A Ni foam-based GDE with macrochannels enhances CO 2 transport and mitigates electrolyte flooding. • The GDE exhibited high conductivity, superior gas permeability, and retained hydrophobicity. • The GDE achieved stable CO 2 RR performance over extended operation, outperforming conventional carbon-based GDEs.