Comparison of modeling and experimental results of modified Pt-based PEMFC cathode-catalysts

Abstract

Pt-based binary and ternary alloy catalysts were investigated by modeling methods and experimentally. The lattice parameters of Pt, Pt3Cr, Pt3Co, Pt3Ir, Pt3CoCr, Pt2CoIr, Pt2Cr2 and Pt2Co2 were determined by molecular modeling methods. According to the optimized structures, the most typical crystal faces were generated. In order to get a good description of sterical and electrostatic factors of material surfaces, reconstruction of surface atoms was taken into account. It was shown that the alloying of Pt with base metals affect surface charge densities, which enables steering of surface reactions into desired positions on the catalyst surface. Both commercial (E-TEK) and laboratory-made catalyst powders and inks based on Pt:Co/C and Pt:Co:Cr/C were characterized voltammetrically. The active Pt surface area increased after activating the catalyst. This can most likely be attributed to the dissolving of Co and Cr from the alloys. All laboratory-made catalysts were also characterized by XRD, TEM and STEM/EDS.