Tailoring catalyst morphology towards high performance for low Pt loaded PEMFC cathodes

The effect of the catalyst synthesismethod on the location of platinum nanoparticles on a high surface area Ketjenblack is investigated with respect to the high current density performance in low loaded proton exchange membrane fuel cells (PEMFC). Catalysts were prepared using various synthetic methods to deposit platinum nanoparticles at different locations on the carbon surface, e.g. inside or outside the pores of the primary particle. Transmission electron microscopy (TEM) suggested, that the Pt-particle deposition can be controlled to be preferentially on the outer carbon surface or within the pores. Electrochemical characterization was performed in thin-film rotating disk electrode (RDE) setup as well as in 5 cm² single cell MEA tests. Although the carbon support was identical for all catalysts, the one with more Pt particles deposited on the outer carbon surface performed superior at high current which was attributed to a lower oxygen mass transport resistance. From the presented data, it can be concluded that not only the type or the surface area of the carbon black support affects the fuel cell performance, but that the synthesis approach is an additional parameter to tune the fuel cell performance at high current density.