Structural Properties of Unsupported Pt−Ru Nanoparticles as Anodic Catalyst for Proton Exchange Membrane Fuel Cells

The structural properties of the nanoparticles of a high-performance commercial unsupported Pt−Ru electrocatalyst with a nominal equiatomic relationship have been studied. They were exhaustively determined by transmission electron microscopy (TEM), high-resolution TEM, fast Fourier transform, electron diffraction, X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD) techniques. TEM and its coupled techniques showed that polyoriented Pt−Ru nanoparticles present an average size of 3.0 ± 0.5 nm with nondetection of metal oxides. XPS spectra, however, indicate the existence of oxidized Pt and Ru species. In particular, the proton- and electron-conducting hydrous Ru oxide involved in the electrocatalytic oxidation of CO and methanol is detected. XRD confirmed that a Pt−Ru solid solution with a 41 at.% Ru is the main crystallographic phase in the electrocatalyst, whereas Pt and Ru oxides appear to be amorphous or very thin. The strain corrected Williamson−Hall models confirmed that nanoparticles ...