Manufacturing of carbon-supported platinum cathodes for proton exchange membrane fuel cell using the doctor blade process: Microstructure and performance

Abstract

Catalyst layers (CL, the anode and cathode) properties do influence the performance of proton exchange membrane fuel cells (PEMFC). CLs are prepared by depositing an ink made from a catalyst (carbon-supported Pt-based nanoparticles, NPs) and an ionomer in appropriate solvents on a substrate, followed by post-treatment (solvent evaporation, calendaring, hot-pressing). The literature rarely provides details and characterizations about CLs fabrication. This contribution investigates a way to prepare Pt/VC (Pt NPs supported on Vulcan XC72 carbon-black) and Pt/GC (Pt NPs supported on graphitized-carbon-black) PEMFC CLs. The ink formulation, mixing and deposition methods are evaluated and the areal homogeneity/texture of the formed CLs thoroughly characterized by scanning electron microscopy and X-Ray fluorescence. Light-ball-milling mixing enables to prepare homogeneous and agglomerate-free inks without degrading the Pt/C catalysts. The optimal ionomer-to-carbon ratio differs for Pt/GC and Pt/VC CLs; it not only depends on the BET surface area of the carbon substrate and its outer apparent surface (apparent carbon particles diameter), but should also be adapted to physicochemical surface properties of the Pt/C sample. Optimized I/C = 1–1.2 enables to improve the performance of Pt/GC cathodes by ca. 300 % versus I/C = 0.5 (at 80 °C, 80%RH), owing to hugely-depreciated proton-transport-resistance in the CL.