Samples of Pt-black reduced in aqueous medium by HCHO and subjected to sintering in hydrogen at different temperatures were studied by XPS. Most of the platinum surface is covered by oxygen and carbon. The presence of small amounts of Si has been confirmed. The ratio of Pt 4f7/2 to 4f5/2 peak intensities indicates that a considerable fraction of the surface Pt atoms is in an oxidized state, bound to oxygen and, presumably, also to surface CO. The double O ls peak confirms the presence of two types of oxygen (Pt-O and CO, respectively). In situ hydrogenation removes oxygen from Pt-O as well as carbon from PtCx species, leaving most of the surface CO intact.
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