Abstract
The composition and processing of the catalyst-ionomer ink used to fabricate electrochemical energy conversion device electrodes can impact the final electrode microstructure and performance. Parameters influencing the microstructure and performance are, for example, solvent ratio, ink processing method and time, ionomer chemistry, and carbon morphology/porosity. Polymer electrolyte fuel cell (PEFC) cathodes are typically prepared by first dispersing a catalyst powder, comprised of platinum or platinum alloy nanoparticles supported on carbon blacks, with ionomer in solvents, followed by extensive mixing using a variety of methods. The electrode properties are controlled by the interactions of the ionomer with the catalyst particles and the support in the catalyst-ionomer ink, by the effect of ink solvent composition on those interactions, and by the ink mixing and coating procedures. This presentation will describe the in-situ/ex-situ ultra-small angle X-ray scattering (USAXS) combined with SAXS studies of the evolution of the cathode catalyst layer to determine the effect of ink processing variables and ink composition on the ink properties, especially on the carbon agglomerate break-up for efficient coating of catalyst layers while optimizing fuel cell performance and durability. The effect of ink formulation is examined for Pt-supported Vulcan carbon (Pt/Vu) and Pt and PtCo-supported on high surface area carbon (Pt and PtCo/HSC) with different ionomers. The results provide the fundamental understanding enabling improved membrane-electrode assembly (MEA) performance and durability. Moreover, the results of the evolution of the catalyst layer during the ink drying process as a function of solvent removal rate and solvent identity will be discussed. Acknowledgments This work was supported by the U.S. Department of Energy, Energy Efficiency and Renewable Energy, Hydrogen and Fuel Cell Technologies Office under the M2FCT Consortium. This work was authored in Argonne National Laboratory, a U.S. Department of Energy (DOE) Office of Science laboratory operated for DOE by UChicago Argonne, LLC under contract no. DE-AC02-06CH11357. This research used the resources of the Advanced Photon Source (APS), a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357.
Published Version
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