Publication date: 15th December 2025
Understanding the stability limitations of oxygen evolution catalysts under practical operating conditions remains a central challenge for advancing proton exchange membrane (PEM) water electrolysis. Here, we employ operando small- and wide-angle X-ray scattering (SAXS/WAXS) in combination with electrochemical measurements to monitor structural transformations of iridium nanoparticles dispersed on TiO₂, TiC, and TiN supports within complete membrane electrode assemblies exposed to accelerated degradation protocols.
Operando SAXS measurements indicate pronounced Ostwald ripening of Ir particles for Ir/TiO₂, with mean particle diameters increasing from ~1.5 to ~2.2 nm, consistent with significant loss of electrochemically active surface area. In contrast, Ir supported on TiC maintains particle morphology during operation; however, the TiC matrix undergoes severe structural deterioration, evidenced by an ~80% reduction in crystallinity and migration of titanium species through the membrane. The TiN-supported system exhibits intermediate stability, showing partial support oxidation, moderate nanoparticle growth, and comparatively limited Ti crossover.
Ex situ characterization by transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS) corroborates the operando observations. These results emphasize the interplay between nanoparticle Ostwald ripening and support degradation as key determinants of catalyst durability and underscore critical design considerations for catalyst–support architectures. Overall, this work highlights the capability of operando SAXS/WAXS applied to full MEAs to disentangle degradation pathways and to inform the development of more resilient anode materials for PEM electrolysis.
The authors acknowledge the CERIC-ERIC Consortium for access to experimental facilities and financial support (proposal 20232198 at the SAXS beamline, ELETTRA Synchrotron, Trieste, Italy). The authors also acknowledge financial support from the project "The Energy Conversion and Storage" (CZ.02.01.01/00/22_008/0004617), funded by the Programme Johannes Amos Comenius.
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