Tuning of size and shape of Au-Pt nanocatalysts for direct methanol fuel cells

In this article, we report the precise control of the size, shape, and surface morphology of Au-Pt nanocatalysts (cubes, blocks, octahedrons, and dogbones) synthesized via a seed-mediated approach. Gold "seeds" of different aspect ratios (1-4.2), grown by a silver-assisted approach, were used as templates for high-yield production of novel Au-Pt nanocatalysts at a low temperature (40 °C). Characterization by electron microscopy (SEM, TEM, HRTEM), energy dispersive X-ray analysis, UV-Vis spectroscopy, zetapotential (surface charge), atomic force microscopy, X-ray photoelectron spectroscopy, and inductively coupled plasma mass spectrometry were used to better understand their physico-chemical properties, preferred reactivities and underlying nanoparticle growth mechanism. A rotating disk electrode was employed to evaluate the Au-Pt nanocatalysts electrochemical performance in the oxygen reduction reaction (ORR) and the methanol oxidation reaction of direct methanol fuel cells. The results indicate the Au-Pt dogbones are partially and in some cases completely unaffected by methanol poisoning during the evaluation of the ORR. The ORR performance of the octahedron particles in the absence of MeOH is superior to that of the Au-Pt dogbones and Pt-black; however, its performance is affected by the presence of MeOH.