Nanoscale topography of GC/Pt-C and GC/Pt-Ru-C electrodes studied by means of STM, AFM and XRD methods

Abstract

Electrodes, assigned as GC/Pt-C and GC/Pt-Ru-C, were formed by deposition of Pt-based catalysts (47.5 wt % Pt + high surface area carbon) and (54 wt. % Pt-Ru alloy + high surface area carbon) on glassy carbon (GC) discs. X-ray diffraction measurements were used for the determination of the average crystallite size and phase composition of both catalysts. Crystallite size for Pt-C catalyst was 2.9 nm for Pt-fcc. In the diffraction pattern of the Pt-Ru-C catalyst two phases, e.g. Pt-Ru-fcc and Ru-hcp were refined using the Rietveld method. Crystallite sizes were 3.9 nm for Pt-Ru-fcc and 2.8 nm for Ru-hcp. STM observations of the surface of GC/Pt-C and GC/Pt-Ru-C electrodes revealed the presence of metal particles of the size in the range 2-6 nm and Pt-C or PtRu-C agglomerates in the range of several tenth of nm. The thickness of the Nafion covering layer determined by AFM is ca. 100 nm. A simplified scheme of the investigated electrodes was created.