Morphological analysis of iridium oxide anode catalyst layers for proton exchange membrane water electrolysis using high-resolution imaging.

This work demonstrates the application of high-resolution, 3D imaging to characterize micro- and nano-scale features of iridium oxide (IrO 2) anode catalyst layers (CLs) in proton exchange membrane water electrolysis (PEMWE). Scanning electron microscopy (SEM) and nanoscale X-ray computed tomography (nano-CT) reveal differences in micro-scale features between spray-coated and blade-coated CLs, and in blade-coated CLs along the fabrication and testing timeline. The electrode thickness distribution of the tested blade-coated CL suggests increased thinning of regions compressed by titanium fibers of the porous transport layer (PTL). Ultra-high-resolution imaging of Xe-plasma focused ion beam with SEM (pFIB-SEM) with the development of a segmentation method is used to investigate nano-scale features between these regions of the tested blade-coated CL, showing variations in porosity and pore sizes. The findings provide insights and modeling inputs for the morphology of PEMWE anode CLs towards a better understanding of the relationship between fabrication, operation, and transport behavior. [Display omitted] • High-resolution, 3D, multi-scale imaging used to characterize PEMWE anode CLs. • SEM and nano-CT show increased thinning of tested CL regions due to PTL fibers. • 6 nm voxel size achieved with pFIB-SEM and in-house segmentation method developed. • "PTL-fiber-compressed" region in tested CL has lower porosity and smaller PSD. [ABSTRACT FROM AUTHOR]