Laying the Foundation for Digital Material Design of Porous Transport Electrodes for PEM Water Electrolysis With Multiscale Tomography

ABSTRACT We present the first multiscale identical location tomography of a porous transport electrode (PTE) of a proton exchange membrane water electrolyzer. The tomogram encompasses length scales between micrometer‐thick fibers to nanopores in the catalyst layer (CL) with nanometer‐thin binder coatings on the iridium‐oxide particles. It was recorded using micro‐computed tomography, focused ion beam scanning electron microscopy tomography, scanning transmission electron microscopy and spectroscopy, nitrogen adsorption, and supplemented by a modeling approach. The reconstruction of the PTE reveals a porosity of around 51% of the porous transport layer (PTL) and 61% of the CL. A thorough analysis of the CL allows a comparison with the pristine catalyst powder and a realistic prediction of the transport parameters by modeling the binder thickness to a mean of 7 to 10.5 nm. Further, the overall transport parameters of the PTE are determined. The PTL has a higher permeability in the through‐plane direction, whereas the CL shows isotropic transport properties. This study offers a comprehensive picture of the multiscale structure and properties of a PTE, which allows for a comparison with catalyst‐coated membranes and computer‐aided optimization of future PTEs.