Operando X-ray characterization platform to unravel catalyst degradation under accelerated stress testing in CO2 electrolysis.

Membrane-electrode assembly (MEA)-based CO2 electrolysis shows great potential for industrial-scale chemical production, but long-term stability remains a key challenge. The degradation mechanisms of catalysts and electrodes in MEAs are not yet fully understood. Here a customized operando synchrotron X-ray characterization platform was established to track the time- and space-resolved evolution of ions and water movement, crystal structure and catalyst variations in MEAs. Using Au and Ag model catalysts, we show that the crystalline phase catalyst stability and catalyst-substrate adhesion are critical to MEA durability. Small- and wide-angle X-ray scattering analysis reveals that Au catalysts, with their robust crystal structure and stable catalyst-substrate adhesion, maintain stability under accelerated stress tests, whereas Ag catalysts degrade due to particle agglomeration, an undesirable dissolution-recrystallization process and detachment. This study demonstrates the advanced capabilities of operando X-ray techniques in elucidating catalyst and electrode degradation in CO2 electrolysers.