Direct Measurement of Electrochemical Selectivity Gradients over a 25 cm² Copper Gas Diffusion Electrode

Electrochemical CO reduction (COR) systems have increasedby ordersof magnitude in their accessible activities in the past decade, particularlyby the implementation of the gas diffusion electrode (GDE) architecture.As GDEs are upscaled by active geometric area (cm(2) to m(2)), reactor performance can change due to physical and chemicalspatial variations which are complicated by the chemical complexityof multiphase and multiproduct electrochemical systems. This workmeasures and evaluates COR performance metrics by a multiport samplingreactor to measure reactant and product concentration down-the-channelof a COR GDE. It is found that the faradaic efficiency (FE) towardthe hydrogen evolution reaction (HER) increases down-the-channel,largely driven by a decrease in the partial pressure of CO, whilethe selectivity for ethylene remains relatively constant down-the-channel.This work highlights the inhomogeneities in performance as electrochemicalreactors are physically upscaled and has significant implicationsfor future scaling of COR and CO2R systems.