摘要：SummaryThe electrochemical reduction of CO2is promising for mitigating anthropogenic greenhouse gas emissions; however, voltage instabilities currently inhibit reaching high current densities that are prerequisite for commercialization. Here, for the first time, we elucidate that product gaseous bubble accumulation on the electrode/electrolyte interface is the direct cause of the voltage instability in CO2electrolyzers. Although bubble formation in water electrolyzers has been extensively studied, we identified that voltage instability caused by bubble formation is unique to CO2electrolyzers. The appearance of syngas bubbles within the electrolyte at the gas diffusion electrode (GDE)-electrolyte chamber interface (i.e. ∼10% bubble coverage of the GDE surface) was accompanied by voltage oscillations of 60 mV. The presence of syngas in the electrolyte chamber physically inhibited two-phase reaction interfaces, thereby resulting in unstable cell performance. The strategic incorporation of our insights on bubble growth behavior and voltage instability is vital for designing commercially relevant CO2electrolyzers.Graphical AbstractDisplay OmittedHighlights•X-ray imaging was used to characterize the bubble formation in a CO2electrolyzer•Gas formed near the GDE-electrolyte chamber interface and caused voltage instabilities•We hypothesize that gas physically inhibits two-phase reaction interfacesElectrochemical Energy Production; Mechanical Engineering Interfacial Electrochemistry
