Characterization platinum oxide

M. Peuckert, and H.P. Bonzel, Characterization of oxidized platinum surfaces by X-ray photoelectron spectroscopy, Surf. Sci. 145, 239-259 (1984). 

The distances found between platinum centers in these molecules have been correlated with the resonating valence bond theory of metals introduced by Pauling. The experimentally characterized partially oxidized one-dimensional platinum complexes fit a correlation of bond number vs. metal-metal distances, and evidence is presented that Pt—Pt bond formation in the one-dimensional chains is resonance stabilized to produce equivalent Pt—Pt distances.297 The band structure of the Pt(CN)2- chain has also been studied by the extended Huckel method. From the band structure and the density of states it is possible to derive an expression for the total energy per unit cell as a function of partial oxidation of the polymer. The equilibrium Pt-Pt separation estimated from this calculation decreases to less than 3 A for a loss of 0.3 electrons per platinum.298... 

An a-dihydrodesoxycodeine , amorphous, alkali-insoluble, and poorly characterized, was reported by Freund [4] to result from the reduction of a-chlorocodide using a colloidal palladium catalyst. A reinvestigation of this reduction, however, showed that under the conditions prescribed by Freund the product consists of 95 per cent. dihydrodesoxycodeine-D with palladized barium sulphate the results are substantially the same, but an amorphous product is obtained in 40 per cent, yield if the amount of catalyst used is large, and this can bo increased to 96-100 per cent, using palladized calcium carbonate and 100 per cent, using platinum oxide as catalyst [29]. The product appears to bo bis- 6 0 -dihydrodosoxycodeino-D [xlvj] and is probably formed... 

Another degree of modification of the catalysts can be achieved by introduction of components which on one hand affect the dispersion of the noble metal similarly to the ceria discussed earlier, but also possess catalytic activities of their own. One example of such an additive explored in depth at Ford Research is molybdenum oxide. Molybdena, similar to ceria, forms a two-dimensional phase on 7-AI2O3 and thereby also affects the Pt dispersion and its catalytic properties. Platinum, in turn, affects strongly the reducibility of molybdena, as shown in Fig. 4, using ESCA to characterize the oxidation state after reduction in the absence and presence of Pt [7]. 

Gasteiger, H.A., et al. 1994. Carbon monoxide electro-oxidation on well-characterized platinum-ruthenium alloys. /. Phys. Chem. 98 617-625. 

The XPS data of platinum particles for both catalysts are shown in Table 1. The decomposition of difference Pt4f spectra shows that spectra of both catalysts consist of three main doublets characterizing platinum atoms in different oxidation state. The content of different platinum species strongly depends on the eatalyst microstracture. 

The platinum-group metals (PGMs), which consist of six elements in Groups 8— 10 (VIII) of the Periodic Table, are often found collectively in nature. They are mthenium, Ru rhodium, Rh and palladium, Pd, atomic numbers 44 to 46, and osmium. Os indium, Ir and platinum, Pt, atomic numbers 76 to 78. Corresponding members of each triad have similar properties, eg, palladium and platinum are both ductile metals and form active catalysts. Rhodium and iridium are both characterized by resistance to oxidation and chemical attack (see Platinum-GROUP metals, compounds). 

A few isocyanides of palladium and platinum are known in the zerovalent oxidation state. The best characterized compounds involve triangular M3 clusters with M-M bonds. 

Mononuclear complexes of palladium and platinum in the +3 oxidation state have only recently been unequivocally characterized [157]. The major advance has come in complexes with macrocyclic ligands such as 1,4,7-trithiacyclononane (ttcn) and 1,4,7-triazacyclononane (tacn) (Figure 3.96). 

The existence of materials now included among the conducting polymers has long been known. The first electrochemical syntheses and their characterization as insoluble systems took place well over a century ago. In 1862 Letheby reported the anodic oxidation of aniline in a solution of diluted sulphuric acid, and that the blue-black, shiny powder deposited on a platinum electrode was insoluble in HjO, alcohol, and other organic solvents. Further experiments, including analytical studies, led Goppelsroeder to postulate in 1876 that oligomers were formed by the oxidation of aniline. 

Recently, it is reported that Xi02 particles with metal deposition on the surface is more active than pure Ti02 for photocatalytic reactions in aqueous solution because the deposited metal provides reduction sites which in turn increase the efficiency of the transport of photogenerated electrons (e ) in the conduction band to the external sjistem, and decrease the recombination with positive hole (h ) in the balance band of Xi02, i.e., less defects acting as the recombination center[l,2,3]. Xhe catalytic converter contains precious metals, mainly platinum less than 1 wt%, partially, Pd, Re, Rh, etc. on cordierite supporter. Xhus, in this study, solutions leached out from wasted catalytic converter of automobile were used for precious metallization source of the catalyst. Xhe XiOa were prepared with two different methods i.e., hydrothermal method and a sol-gel method. Xhe prepared titanium oxide and commercial P-25 catalyst (Deagussa) were metallized with leached solution from wasted catalytic converter or pure H2PtCl6 solution for modification of photocatalysts. Xhey were characterized by UV-DRS, BEX surface area analyzer, and XRD[4]. 

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