Gold-Palladium or Platinum

Many classical heterogeneous catalysts, e.g., oxides and related compounds with incorporated ruthenium, gold, palladium, or platinum were found to be effective for the aerobic oxidation of alcohols. Silver and cobalt were also included in this catalytic family and have raised expectations regarding the availabifity of the catalysts. 

A metallic electrode consisting of a pure metal in contact with an analyte solution develops an electric potential in response to a redox reaction occurring at its metal surface. Common metal electrodes such as platinum, gold, palladium or carbon are known as inert metal electrodes whose sole function is to transfer electrons to or from species in solution. Metal electrodes corresponding to the first kind are pure metal electrodes such as Ag, Hg and others that respond directly to a change in activity of the metal cation in the solution. For example, for the reaction... 

Hydration and Hydroalkoxylation of Alkynes Gold compounds were first applied to catalyze these types of reactions by Utimoto et al. in 1991, when they studied the use of Au(III) catalysts for the effective activation of alkynes. Previously, these reactions were only catalyzed by palladium or platinum(II) salts or mercury(II) salts under strongly acidic conditions. Utimoto et al. reported the use of Na[AuCI41 in aqueous methanol for the hydration of alkynes to ketones [13]. 

The conductor materials may be noble metals, such as gold, silver, palladium, or platinum, or nonnoble metals, such as copper, nickel, or aluminum. Copper is a desirable material for its low cost and low resistivity (3 X 10"6-5 X 10-6 fl-cm, or two to three times the resistivity of elemental copper) however, it requires an oxygen-free atmosphere for firing. 

Bimetallic colloids containing gold and palladium or platinum have been deposited onto carbon or graphite for use as catalysts for the selective oxidation of organic compounds52 (Section 8.3), in the same way as for pure gold colloids (Section 4.6). 

Klecirodcs fashioned from platinum, gold, palladium, or other inert nicials often bcrve as Indicator electrodes foi oxidation-reduction systems. In Iheso applications. the inert electrode acts as a source or sink for electrons transferred from a redov system in the solution. For example, the potential of a platinum electrode in a solution containing Ce( 111 and Ce(fV) ions is given hy... 

Colloidal Au and Au/C catalysts can be used to oxidize d-glucose to d-gluconic acid [1,77], In fact, Au/C catalyst is a valid alternative to most of the investigated multimetallic catalysts based on palladium or platinum. Moreover, gold has the unique property of operating without the external control of pH, thus ensuring total conversion at all pH values and total selectivity to gluconic... 

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