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) 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.