Membrane electrode assembly (MEA) CO₂ electrolyzers are a promising approach toward producing carbon-neutral chemicals; however, they often have stability issues related to flooding of the gas diffusion electrode (GDE). Thus, there is an urgent need to comprehend water management in these devices and to engineer electrodes that allow both stable and efficient electrocatalytic performance. Here, we investigated the possible causes of suppression in the CO₂ reduction reaction (CO₂RR) selectivity on Cu via in operando X-ray diffraction (XRD) analysis. The in operando XRD allowed us to monitor electrolyte evolution and bicarbonate formation in the GDE, while in-line gas chromatograph and mass spectrometer allowed us to correlate those changes to the cathode and anode product distribution during CO₂ electrolysis (CO₂E). We found direct evidence for salt precipitation in the cathode GDEs, which causes electrolyte build-up and an increase in hydrogen evolution reaction (HER). We also observed that the increase in HER is related to a drop in cell potential, at least partially caused by a shift in ion transport through the membrane from carbonates to more conductive hydroxide ions. Thus, this work suggests that proper ion management is an important key to enhanced durability throughout the device.

膜电极组件 (MEA) CO ₂电解槽是生产碳中性化学品的一种很有前途的方法；然而，它们通常存在与气体扩散电极 (GDE) 的溢流相关的稳定性问题。因此，迫切需要了解这些设备中的水管理，并设计出具有稳定和高效电催化性能的电极。在这里，我们通过原位X 射线衍射 (XRD) 分析研究了抑制 CO ₂还原反应 (CO ₂ RR) 对 Cu 的选择性的可能原因。实战中XRD 使我们能够监测 GDE 中的电解质演变和碳酸氢盐形成，而在线气相色谱仪和质谱仪使我们能够将这些变化与 CO 2 电解 (CO 2 E) 期间的阴极和阳极产物_分布相关_联。我们发现了阴极 GDE 中盐沉淀的直接证据，这会导致电解质积聚和析氢反应 (HER) 增加。我们还观察到 HER 的增加与细胞电位的下降有关，至少部分是由于通过膜的离子传输从碳酸盐转变为更具导电性的氢氧根离子。因此，这项工作表明，适当的离子管理是提高整个设备耐用性的重要关键。