Highly dispersed oxide materials

The SEA approach can be applied to a novel system in three steps (1) measure the PZC of the oxide (or carbon) and choose a metal cation for low-PZC materials and an anion for high-PZC materials, (2) perform an uptake-pH survey to determine the pH of the strongest interaction in the appropriate pH regime (high pH for low PZC and vice versa), and (3) tune the calcination/reduction steps to maintain high dispersion. Highly dispersed Pt materials have been prepared in this way over silica, alumina, and carbon. Other oxides can be employed similarly. For bimetallics, the idea is to first adsorb a well-dispersed metal that forms an oxide intermediate with a PZC very different to the support. In this way the second metal can be directed onto the first metal oxide by SEA. Reduction may then result in relatively homogeneous bimetallic particles. 

In recent years, there has been a growing interest in the electrochemical synthesis of composite materials consisting of metal matrix with embedded particles of oxides, carbides, borides, etc. Metal-matrix composites offer new possibilities in fabrication of ftmctional coatings with radically improved durability and performance [1], However, in spite of the efforts of many researches, the overall picture of the processes occurring during co-deposition of metal with dispersed phase and mechanism of particle-induced modification of mechanical and chemical properties still remain unclear. In this study, we focused on the kinetics and mechanism of the electrochemical co-deposition of nickel with highly dispersed oxide phases of different nature and morphology. 

The spraying method involves a chemical reduction or a hydrolysis reaction between the organic or the inorganic highly dispersed starting material and the mixture of carrier gas and reactive gas at the heated substrate surface where the expected metal or oxide film is formed. 

Vanadium oxides, same as oxides of yet another metal with variable valence and also with intercalation ability in respect to lithium cations, have lately been widely studied for their application as an active material for positive electrodes in ECSCs (Chen and Wen, 2003). V2O5 is applied on highly dispersed carbon materials as supports, as specific electron conductivity of V2O5 is rather low. 

CatalyticaHy Active Species. The most common catalyticaHy active materials are metals, metal oxides, and metal sulfides. OccasionaHy, these are used in pure form examples are Raney nickel, used for fat hydrogenation, and y-Al O, used for ethanol dehydration. More often the catalyticaHy active component is highly dispersed on the surface of a support and may constitute no more than about 1% of the total catalyst. The main reason for dispersing the catalytic species is the expense. The expensive material must be accessible to reactants, and this requires that most of the catalytic material be present at a surface. This is possible only if the material is dispersed as minute particles, as smaH as 1 nm in diameter and even less. It is not practical to use minute... 

Mesoporous carbon materials were prepared using ordered silica templates. The Pt catalysts supported on mesoporous carbons were prepared by an impregnation method for use in the methanol electro-oxidation. The Pt/MC catalysts retained highly dispersed Pt particles on the supports. In the methanol electro-oxidation, the Pt/MC catalysts exhibited better catalytic performance than the Pt/Vulcan catalyst. The enhanced catalytic performance of Pt/MC catalysts resulted from large active metal surface areas. The catalytic performance was in the following order Pt/CMK-1 > Pt/CMK-3 > Pt/Vulcan. It was also revealed that CMK-1 with 3-dimensional pore structure was more favorable for metal dispersion than CMK-3 with 2-dimensional pore arrangement. It is eoncluded that the metal dispersion was a critical factor determining the catalytic performance in the methanol electro-oxidation. 

Sintered Electrodes In these electrodes the active materials are present in pores of a sintered nickel support plate. This plate is manufactured by sintering of highly disperse nickel powder produced by thermal decomposition of nickel pentacarbonyl Ni(CO)5. The plates are filled by impregnating them in alternation with concentrated solutions of salts of the corresponding metals (Ni or Cd) and with an alkali solution serving to precipitate insoluble oxides or hydroxides. 

In this paper we will focus on two materials magnesium oxide and molybdenum highly dispersed on silica. The formation of oxygen anions requires electrons at a high potential. On magnesium oxide these electrons are present as Fs centers, which are formed by irradiation ( X = 254 nm) of a degassed sample in the presence of H2 (5). On Mo/Si02 the electrons are derived by the oxidation of Mo(V) to Mo(VI) (6,7). 

Yang, J., et ah, An effective strategy for small-sized and highly-dispersed palladium nanoparticles supported on graphene with excellent performance for formic acid oxidation. Journal of Materials Chemistry, 2011. 21(10) p. 3384-3390. 

The six sections following the overview chapter deal with aspects of selective oxidation that range from theories and concepts to state-of-the-art engineering applications. Several chapters describe the synthesis, characterization, and performance of potentially attractive new catalytic materials. These catalysts range from single crystals with well-defined crystal faces to highly dispersed or amorphous solids. Most of the actual catalytic reactions studied involve the oxidation of hydrocarbons in the range from to C. ... 

An NSR catalyst consists of precious metal as active site, basic material as NOx storage site, and support for highly dispersing these sites. As active site, Pt and Rh are much effective elements for NSR catalysts. One important role of the active site is to oxidize NO under oxidizing condition. Our early catalyst test showed that, precious metals and Mn oxide loaded on alumina are indicated a high NO oxidation activity. Particularly, Pt showed the highest turn over... 

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