Poster Presentation 24th Australian Conference on Microscopy and Microanalysis 2016

Binary and ternary platinum-based nanostructures as ORR electrocatalysts (#238)

Gerard G.M. Leteba 1 2 , David D.R.G Mitchell 3 , Pieter P.B.J. Levecque 1 , Candace C.I. Lang 2
  1. University of Cape Town, Rondebosch, CAPE TOWN, South Africa
  2. Department of Engineering, 2109, Australia., Macquarie University, Sydney, NSW, Australia
  3. UOW Electron Microscopy Centre, University of Wollongong, Sydney, New South Wales,, Australia

Metallic nanocatalysts with high-index surfaces are expected to exhibit high catalytic activity.  We have synthesized monodisperse, faceted Pt-based nanoalloys, characterized their structure and tested their surface functionality.

Although unalloyed platinum (Pt) is the standard electrocatalyst for Hydrogen Fuel Cells, its widespread use is limited by high cost and finite supply1.  The formulation of Pt-based nanoalloys, in which the Pt is partially substituted by more cost-effective 3-d transition metals, can minimize Pt loading; optimal design and synthesis of the nanoalloys could improve catalytic efficiency.   The pursuit of alloyed nanostructures with controllable surface morphology and composition, however, still remains a challenge.

We report on a novel co-reduction strategy for the synthesis of Pt-based nanostructures: Pt-based bimetallic nanoalloys were successfully synthesized by the co-reduction of Pt and M (M = alloying elements, Ni and Co) precursors in a homogeneous mixture of surfactants (oleylamine, OAm and hexadecylamine, HDA) and a high-boiling point solvent (benzyl ether), using molybdenum hexacarbonyl as the reductant. Good control over alloy morphology and composition were achieved by manipulating the experimental parameters.

The resulting well-defined nanostructures with facet-directed surfaces were revealed by transmission electron microscopy (TEM). High-resolution HAADF-STEM and HR-TEM show lattice fringes; STEM-EDX shows the coexistence of Pt and M; XRD shows the particles to have an fcc structure. The nanostructures are accordingly Pt-based alloys and highly crystalline.  The nanostructures were probed electrochemically to investigate their functionality and were observed to display exceptional catalytic activity compared to the commercially available state-of-the-art Pt-C electrocatalysts.

Ourfindings demonstrate a synthesis protocol which produces high-quality nanoalloys with high-index surfaces, exhibiting superior catalytic activity. This offers great synthesis potential for highly functional electrocatalysts with controllable composition and unique surface structures to substitute pure Pt nanostructures in fuel cell applications.

  1. 1. Wu, J., Gross, A., Yang, H. Nano Lett. 11 (2011) 798 – 802.
  2. 2. Zhang, J., Fang, J. J. Am. Chem. Soc. 131 (2009) 18543 – 18547.