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Electrocatalytic conversion of CO2 is a promising process to produce renewable chemical feedstocks, such as CO, formic acid, ethylene, and ethanol. To overcome mass transfer limitations imposed by the low solubility of CO2 in the liquid phase, gas diffusion electrodes (GDEs) are used to ensure an adequate supply of CO2. The gas–liquid interface within the GDEs is crucial for achieving high selectivity and stability of CO2 reduction reaction (CO2RR), but it is prone to flooding, which can terminate the reactions. Here, we built electrochemical models of silver-based and copper-based GDEs for studying intrinsic factors related to flooding. Our results reveal that there is a narrow "pressure window" for CO2RR, which has a negative correlation with current density. We further define three regions based on the "pressure window": the bubbling zone, the normal working condition zone, and the permeable zone. Our research shows that the bubbling zone offers better selectivity for gaseous products, while the permeable zone favors the competitive hydrogen evolution reaction. Furthermore, electrochemical characterization testing investigated the characteristics of each zone and its impact on CO2RR.
Chen et al. (Sat,) studied this question.