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 in 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 it 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 have crystalline defects with a mean size of 2.8-2.9 nm. Cyclic voltammetry in 0.5 M H2SO4 was employed to determine the effect of the variation of the anodic limit scan and the potential range for the formation of hydroxylated species and metal oxides. The nanoparticles surface was active regardless of the metal oxides detected by structural analysis, which were stable under cycling and not protective.