Porous Metallic Membranes As High-Performance Gas Diffusion Electrodes for CO2 Reduction in Zero-Gap Electrolyzers

Combining the electrochemical reduction of CO₂ (eCO₂RR) with carbon-neutral energy sources creates groundbreaking possibilities for using CO₂ as a raw material for the sustainable production of fuels and chemicals. In this context, recent technoeconomic analyses have emphasized the importance of achieving high current densities (i.e., hundreds of mA cm^‒2) for the eCO₂RR to be practically viable.^[1]

Cell designs that integrate selective eCO₂RR catalysts into a membrane electrode assembly (MEA) are a promising approach to reduce ohmic losses and achieve high energy efficiency at elevated current densities.^[2,3] In this contribution, we show that silver membranes—commonly used as porous filtration media in biotechnological applications—sustain high rates of CO₂ reduction to CO (> 200 mA cm^‒2) when used as GDEs in a zero-gap configuration.^[4] These metallic electrodes are simple, highly stable, and cost-competitive vis-à-vis carbon-based GDEs. However, CO₂ crossover across the anion-exchange membrane (AEM) results in poor reactant utilization and in the early onset of mass transfer limitations, highlighting the importance of carrying out a full mass balance to adequately characterize eCO₂RR devices.^[4] Furthermore, we will discuss how these porous silver membranes can be used as templates for the synthesis of freestanding copper GDEs, and how different electrode morphologies and compositions can be targeted via the synthesis procedure. In tandem with a judicious selection of anolyte and AEM, these GDEs show promising performance for the conversion of CO₂ into multi-carbon products at high current densities.

[1] M. Jouny, W. Luc, F. Jiao, Ind. Eng. Chem. Res. 2018, 57, 2165-2177

[2] T. Burdyny, W.A. Smith, Energy Environ Sci. 2019, 12, 1442-1453

[3] D. Higgins, C. Hahn, C. Xiang, T.F. Jaramillo, A.Z. Weber, ACS Energy Lett. 2019, 4, 317-324

[4] G.O. Larrazábal, P. Strøm-Hansen, J.P. Heli, K. Zeiter, K.T. Therkildsen, I. Chorkendorff, B. Seger, ACS Appl. Mater. Interfaces 2019, 11, 41281-41288