Pt-Au Alloying at the Nanoscale

The formation of nanosized alloys between a pair of elements, which are largely immiscible in bulk, is examined in the archetypical case of Pt and Au. Element specific resonant high-energy X-ray diffraction experiments coupled to atomic pair distribution functions analysis and computer simulations prove the formation of Pt Au alloys in particles less than 10 nm in size. In the alloys, Au Au and Pt Pt bond lengths differing in 0.1 angstrom are present leading to extra structural distortions as compared to pure Pt and Au particles. The alloys are found to be stable over a wide range of Pt Au compositions and temperatures contrary to what current theory predicts. The alloy-type structure of Pt Au nanoparticles comes along with a high catalytic activity for electrooxidation of methanol making an excellent example of the synergistic effect of alloying at the nanoscale on functional properties.