Structural Characterization of Ru-Modified Carbon-Supported Pt Nanoparticles Using Spontaneous Deposition with CO Oxidation Activity

The modification of carbon-supported Pt nanoparticles, high performance (HP) 20% Pt on Vulcan XC-72 carbon black (Pt/C electrocatalyst), by spontaneous deposition of Ru species is examined employing electrochemical and structural techniques. Thin-layer electrodes were prepared by applying aqueous catalyst inks of Pt/C on glassy carbon (GC) disks. Ru deposition was carried out by immersion of the prepared electrode in deaerated RuCl3/HClO4 solutions. The subsequent cyclic voltammetry experiments of the modified electrocatalysts (Ru(Pt)/C) were performed in 03 M H2SO4 to determine the Ru coverage and the electroactive surface. CO stripping voltammetry showed the promotional effect of Ru(Pt)/C for the CO oxidation compared to Pt/C. The structural characterization of the modified electrocatalysts was performed by transmission electron microscopy (TEM), energy dispersive X-ray (EDX) analyses, fast Fourier transform (FFT), selected-area electron diffraction (SAED), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). TEM observations revealed no appreciable signals of Ru agglomerates, and EDX confirmed the regular incorporation of Ru species to the nanoparticles. XRD analyses showed the characteristic profile of the Pt face-centered cubic (FCC) structure and the absence of crystalline Ru or Ru oxides. The application of the Williamson-Hall models indicated that Ru incorporation did not significantly affect the internal strain of the Pt nanoparticles, the increase of the crystallite size being attributed to an epitaxial growth of the Ru deposit. XPS measurements reported the presence of nonreducible RuO2 and hydrous RuO2 (RuOxHy),) as the main Ru species in Ru(Pt)/C, the hydrous species justifying the promotional effect for the CO oxidation.