Novel Front Contacts for Hydrophobic Gas Diffusion Layers Enable High Energy Efficiency and Durability for Electrochemical CO2 Reduction to C₂₊ Products

Electrochemical CO₂ reduction (eCO2R) is an attractive route to mitigate the rise in the global CO₂ concentration while producing value-added chemicals. Ethylene (C₂H₄) is one such product of eCO2R which is an essential industrial precursor with a prominent global market of $230 billion. The large-scale implementation of C₂H₄-selective CO₂ electrolyzers is still challenge due to the low energy efficiencies causes by high ohmic resistances when either employing a hydrophobic gas diffusion layer such as expanded polytetrafluoroethylene (ePTFE), or employing a near neutral catholyte in a single-gap electrolyzer. In this work, we have developed a novel front contact for a CO₂ electrolyzer in a zero-gap architecture for electrically insulating gas diffusion layers. This front contact layer allows for incorporating an ePTFE gas diffusion layer while achieving similar full cell voltages as carbon-based gas diffusion electrodes; this configuration also has the added benefits of increased cell stability and selectivity for ethylene. By tailoring the catalyst layer, gas diffusion medium, and operating conditions for a zero-gap ePTFE gas diffusion layer, we were able to achieve a full cell voltage of 2.5 V, with faradaic efficiencies of 48% for ethylene and over 90% faradaic efficiency for reduced carbon species at 200 mA cm^-2 and 25 cm² geometric area cell. This work points towards strategies for developing a scalable, stable, and high energy efficiency eCO2R for C₂₊ products.
This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

LLNL-ABS-860657