Platinum oxide diffraction

After 2 hours of electrolysis10 at 1.5 V, the product, having filled the bottom of the beaker, is filtered in a plastic funnel. The crystals are then washed with two 6-mL portions of cold water and allowed to air dry. The yield of 1.4-1.5 g (3.2-3.4mmole) represents 88-94% based on original K2[Pt(CN)4] 3H20. Using X-ray diffraction powder patterns, it is established that the products of both syntheses given above are identical.8 The platinum oxidation state of 2.29(1) is established by iodine-thiosulfate titrations.8... 

Platinum—Iridium. There are two distinct forms of 70/30 wt % platinum—iridium coatings. The first, prepared as prescribed in British patents (3—5), consists of platinum and iridium metal. X-ray diffraction shows shifted Pt peaks and no oxide species. The iridium [7439-88-5] is thus present in its metallic form, either as a separate phase or as a platinum—iridium intermetallic. The surface morphology of a platinum—iridium metal coating shown in Figure 2 is cracked, but not in the regular networked pattern typical of the DSA oxide materials. 

Elemental composition Pt 85.91%, O 14.09%. The oxide may be characterized by its physical properties and by x-ray diffraction. The compound may be thermally decomposed at elevated temperatures or reduced by hydrogen to form platinum metal which may be digested with aqua regia and HCl, diluted, and analyzed by flame AA, ICP/AES or ICP/MS. 

Diffraction patterns can be used to identify the various phases in a catalyst. An example is given in Fig. 10.3b, where XRD is used to follow the reduction of alumina-supported iron oxide at 675 K as a function of time. The initially present oc-Fe2C>3 (haematite) is partially reduced to metallic iron, with Fe3C>4 (magnetite) as the intermediate. The diffraction lines from platinum are due to the sample holder [10]. 

The powder XRD profiles of the Co Pt NPs are shown in Figure 2. All the peaks correspond to the metallic platinum diffraction. The peaks of the cobalt are hidden under the peaks of platinum due to the overlapping of their diffraction peaks. No diffraction patterns of cobalt oxides are detected. The evidence of the presence of the... 

A variety of model catalysts have been employed we start with the simplest. Single-crystal surfaces of noble metals (platinum, rhodium, palladium, etc.) or oxides are structurally the best defined and the most homogeneous substrates, and the structural definition is beneficial both to experimentalists and theorists. Low-energy electron diffraction (LEED) facilitated the discovery of the relaxation and reconstruction of clean surfaces and the formation of ordered overlayers of adsorbed molecules (3,28-32). The combined application of LEED, Auger electron spectroscopy (AES), temperature-programmed desorption (TPD), field emission microscopy (FEM), X-ray and UV-photoelectron spectroscopy (XPS, UPS), IR reflection... 

Figures 4.30(c) and 4.31(c) show HREM images representative of the catalysts reduced at 1173 K and further oxidised in pure O2 at 1173 K. The structure of both catalysts is clearly different from that observed after re-oxidation at 773 K. Notice that in this case both materials seem to be formed by small, crystalline, metal particles dispersed over the ceria surface. Fringe analysis confirms that these crystallites consist of metallic rhodium and platinum, respectively. Thus, the DDPs of the larger particles observed in the image of the Pt catalyst show 0.8 nm Moire-type fringes aligned with the (111 )-Ce02 reflections. These spots arise from double diffraction in the (lll)-Pt and (Ill)-Ce02 planes under a parallel orientation relationship. Therefore this result, in addition to confirm the presence of metallic Pt particles in the sample oxidised at 1173 K, suggest that these particles are epitaxially grown on the support. A detailed inspection also reveals that the exposed surfaces of these particles are clean, i.e. free from support overlayers.

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