Oxidation noble metal

Metal oxides. Noble metals are covered with a surface oxide film in a broad range of potentials. This is still more accentuated for common metals, and other materials of interest for electrode preparation, such as semiconductors and carbon. Since the electrochemical charge transfer reactions mostly occur at the surface oxide rather than at the pure surface, the study of electrical and electrochemical properties of oxides deserves special attention. 

Again, in aqueous solution, the reaction proceeds on oxidized noble metal surfaces and, at the potentials at which it takes place, the reactant anion, RCOO , is strongly adsorbed. The R must be aliphatic at the a carbon as the Kolbe reaction does not proceed if, for example, benzoic acid is the reactant however, fi-, or y-aryl alkyl carboxylic acids, for example, phenylacetic acid, will undergo the Kolbe coupling reaction but with rather poor efficiency. The reaction will also proceed on nonoxidized noble metal surfaces, for example, Pt in anhydrous CH3COOH or CF3COOH, gettered with acetic anhydride... 

In the study of electrochemical reactions, the experimental examination of reaction orders has played a dominant role in reaction mechanism determinations, especially for the cases of the cathodic evolution reaction, the process of anodic Clj formation, and the Oj evolution reaction at oxidized noble metals and at oxide electrode (e.g., RuOj) surfaces (Sections XVI and XVII). 

The DSA-type anodes are inert , coated anodes made of a valve metal (titanium, niobium, or tantalum) base coated with an electrochemically active coating. The active coating is made either of noble metals or of mixed metal oxides. Noble metals in active coatings are usually platinum or platinum alloys. Mixed metal-oxide coatings contain active oxides and inert oxides the active components are usually ruthenium dioxide (R.UO2) and iridium dioxide (IrC>2) and the inert components are mostly titanium dioxide (TiC>2) and other oxides such as tantalum... 

C.S. Chen, H.J.M. Bouwmeester, H. Verweij and A.J. Burggraaf, Oxygen permeation through stabilized bismuth oxide-noble metal composites. Solid State Ionics, accepted. 

The ceria surface area of a commercial Pt-Rh three-way catalyst was determined after laboratory hydrothermal aging at 1173-1373 K and after 200 h on engine bench. It was measured by X-ray diffraction (XRD) line broadening analysis and by a method based on the exploitation of the hydrogen temperature programmed reduction (TPR) profiles. In this case, the hydrogen uptakes below about 900 K include the ceria surface reduction and that of the oxidized noble metals. They are analyzed and discussed, assuming two possiblities for the metals oxidation state. 

Several electrochemically important reactions occur on the surface of oxidized noble metal electrodes without reaction with the surface oxide. The oxide film then behaves as a new type of electrocatalyst surface on which the reaction proceeds, in distinction to the underlying metal. The oxide films are normally only one to three oxygen layers in thickness. The following inorganic reactions are of this class (a) O2 evolution, (b) CI2, (c) Br2 (to a small extent, since adsorbed Br blocks surface oxidation) and N2 evolution (from N3 ) while, in the case of organic reactions, (a) the Kolbe and Crum-Brown/Walker syntheses, as well as (b) the Hofer-Moest reaction, are of this type. ... 

Metal oxide-noble metals Chemiresistors (sensing Metal oxide—gas-sensing matrix... 

A large number of studies have been performed for the development of active and coke-resistant catalysts for the dry reforming of methane. The common catalysts are composed of a metal from group VIII to X supported over an oxide. Noble metals are well known for their high catalytic activities in reforming reactions, but nickel-based catalysts are widely used due to its lower cost... 

Heterogeneous catalytic oxidation of hydrocarbons has been extensively studied for the last century, since a large fraction of high value chemical feed stocks, such as organic aldehydes, acids, ketones, alcohols, etc., are produced by the catalytic partial oxidation of light alkanes and alkenes. Historically, oxidation reactions have always been carried out over either noble metals or transition metal oxides. Noble metals have been almost exclusively applied to complete oxidations, whereas transition metal oxides have been used for both selective and complete oxidations. 

The decomposition of the peroxide to hydroxide and oxygen is a key rate-limiting step in the reaction sequence. To accelerate the reduction of the peroxide species and the overall reaction rate, the air cathode is formulated using catalytic compounds which promote the reaction in step 2. These catalysts are typically metal compounds or complexes such as elemental silver, cobalt oxide, noble metals and their compounds, mixed metal compounds including rare earth metals, and transition metal macrocyclics, spinels, manganese tUoxide, phtalocyanines or perovskites." - ... 

Less Ru permeable membranes Other catalyst (favors either NH oxidation, noble metals less affected by NH3) Improved mixing homogeneity of alloy components... 

Zhao HT, Lu BG, Xu J, Xie EQ, Wang TH, Xu Z (2013) Flectrospinning-thermed treatment synthesis a general strategy to decorate highly porous nanotubes on both interned and extemed side-walls with metal oxide/noble metal nanoparticles. Nanoscale 5 2835-2839... 

Chen, C. S., Kruidhof, H., Bouwmeester, H. J. M., Verweij, H, and Burggraaf, A. J. (1996). Oxygen permeation through oxygen ion-conducting oxide-noble metal dual phase composites. Solid State Ionics 86/88(1), 569. 

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