In an effort to reduce the world's dependence on fossil fuels as well as lower green house gas emissions, proton exchange membrane fuel cells (PEMFC) have been considered by many as a prime candidate for both mobile and stationary alternative energy sources. The principal limiting factor for efficiency in fuel cells is the oxygen reduction reaction (ORR) which is driven by platinum based catalyst materials.  Numerous methods have been developed to synthesize particles that make more efficient use of the active surfaces by tuning shapes, sizes and facets.  For example, it was recently demonstrated that selectivity can be tuned by controlling particle shape in the case of promoting trans olefin isomerization to their cis counterparts using close-packed Pt (111), Pt (557) and Pt (100) surfaces as opposed to a more open Pt (110), which favored the trans-counterparts.  Furthermore, it has been reported that certain facets exhibit improved ORR activity while others may decrease activity at the bulk phase single crystal level.  Here, we will present a study of various wet chemical reduction methods targeting specific morphologies and the resulting electrochemical activity.  Determining the effects of synthetic parameters on the final product via transmission electron microscopy (TEM), small angle x-ray scattering (SAXS) and wide angle x-ray scattering (WAXS) provides mechanistic insight on growth kinetics, while electrochemical studies correlate physical properties to performance.  Understanding structure and activity relationships will allow us to intuitively design next generation materials with enhanced properties.

Faceting of nanoscale Pt and Au particles for applications in catalysis

244th National Meeting (2012)

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