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Two-Theta Degrees

Fig. 1. X-ray diffraction patterns of carbon supported catalysts.

Two-Theta Degrees

Fig. 1. X-ray diffraction patterns of carbon supported catalysts.

XPS analysis. — The nature of surfacc spccies of Pt/C and Pt-Ru/C catalysts was investigated by XPS analysis. The Ru 3pjc line in the Pt-Ru/C catalyst (Fig. 2a) derives from the contributions of two components with B.E. of 463.37 and 466.90 eV. These peaks could be attributed to RuO; and Ru03 spccics. Yet. the width of ca. 4 eV of the main peak suggests that this component could derive from the contributions of more than one spccies with similar B.E. In order to understand the nature of the electronic effects that Ru could cause on the Pt in the present catalyst, wc have investigated the Pt 4f region (Fig. 2b). To achieve a consistent fit of the spectral data three components were needed for the Pt 4f7/2 at B.E. 71.78 (Pt°), 73.20 (Pt2+) and 74.65 (Pt41). It is noteworthy that the peak position of zerovalent Pt in the Pt-Ru/C sample shifts by 0.23 eV to higher B. E. with respect to the Pt/C sample.

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