Advanced Impedance Analysis for Performance Degradation during Low-Temperature CO2 Electroreduction

Electrochemical impedance spectroscopy (EIS) is a powerful tool commonly used to study electrochemical systems. Nevertheless, its application in CO₂ electroreduction has been so far limited due to its complex reaction mechanism and environment. Although initial findings have demonstrated the viability of applying EIS analysis in CO₂ electrolyzers, the assignment of individual processes in the impedance spectra remains ambiguous. Therefore, a more detailed investigation, especially focused on its application in evaluating degradation mechanisms, is essential. In this study, a stable gas diffusion electrode (GDE) system was developed for a comprehensive EIS and distribution of relaxation time (DRT) evaluation to assess key degradation mechanisms under accelerated stress conditions such as high current density and low operating temperature. Validated by post-mortem analysis and complementary methods, we demonstrate the viability of this approach for operando monitoring of CO₂ electroreduction by assigning individual mechanistic processes in the GDE and linking them to performance degradation over time.