(648c) Investigation of Degradation of Membrane Electrode Assembly Cell Via Operando X-Ray Tomography Measurement

The electrochemical CO₂ reduction reaction (eCO₂R) to produce value-added chemicals and fuels offers a promising pathway toward carbon neutralization. Gas diffusion electrodes facilitate the CO₂ mass transport to the cathode catalysts, which enable the operation at elevated current densities by reducing the diffusion length of CO₂ to reach the catalyst surface and overcoming the low solubility of CO₂ in aqueous electrolytes. However, performing CO₂ electrolysis at high current density generates significant hydroxide ions at the cathode and promotes the reaction to form carbonate ions with hydroxide ions. There is a consensus that salt precipitation hampers CO₂ mass transport and causes flooding, confirmed by ex-situ analysis after device operation. Operando X-ray tomography, which is a nondestructive technique for 3D imaging and investigating morphological changes, is an ideal method for studying features of interest in an electrochemical reaction environment. In this work, we focus on investigating the possible degradation of eCO2R selectivity on Cu GDE via operando X-ray tomography. The salt precipitation and flooding in the GDE are monitored during in-line gas chromatography, which allows us to correlate changes in the product distribution during eCO₂R. We find that the distinctive degradation of the MEA cell can be explained by the extent of precipitation and flooding. The morphological changes resulting from precipitation growth, dissolution, and regrowth from the Cu surface to the gas diffusion layer are observed using micro-CT imaging during transient oscillatory voltage profile and selectivity change in Cu GDE. This work can provide insight into the degradation mechanism of MEA cells and the strategies to enhance the durability of devices.