Dynamic Relocation of Copper Catalysts in Gas Diffusion Electrodes during CO2 Electroreduction

High Resolution Image Download MS PowerPoint Slide Developing technologies that convert CO 2 into valuable carbon products using renewable energy is of growing significance. Copper (Cu) is a unique electrocatalyst capable of reducing CO 2 to value-added multicarbon (C 2+ ) compounds. While recent in situ studies have elucidated the dynamic evolution of Cu catalysts during electrochemical CO 2 reduction reactions (CO 2 RR), the relationship between catalyst behavior in gas diffusion electrodes (GDEs) and C 2+ product selectivity at industrially relevant current densities remains insufficiently understood. In this study, we examined the correlation between the structure, chemical state, and C 2+ selectivity of Cu catalysts in Cu-GDEs during CO 2 RR operation at current densities exceeding 200 mA/cm 2 . Ex situ and in situ scanning X-ray fluorescence microscopy revealed significant relocation of Cu within the GDE after CO 2 RR. In situ X-ray absorption spectroscopy identified the presence of Cu 1+ species during operation, indicating that Cu relocation proceeds via a dissolution-redeposition. The dissolution-redeposition behavior was found to be pH-dependent and more pronounced at high pH. Online gas chromatography demonstrated that the decrease in C 2+ selectivity over time was primarily due to flooding, overshadowing the impact of Cu relocation on C 2+ selectivity. These findings provide important insights for designing stable and highly selective Cu-based GDEs for practical CO 2 electrolyzers.