Silver film catalyst

Most electroless silver appHcations are for silvering glass or metallizing record masters. Mirror production is the principal usage for electroless silver. The glass support is cleaned, catalyzed using a two-step catalyst, and coated on one side with an opaque silver film (46). Silver-plated nylon cloth is used as a bacteriostatic wound dressing. A tiny current appHed to the cloth causes slow silver dissolution. The silver acts as a bactericide (47). 

Occurrence. Nearly all the silver ores are compounds of silver with sulphur and the neighbours in the Periodic Table arsenic, antimony and bismuth (argentite Ag2S, the most common silver compound, pyrargyrite Ag3SbS3, proustite Ag3AsS3). Other silver minerals include the halides. Silver is found sometimes as the free metal. Secondary silver (from catalysts, scraps, photographic films, etc.) is an important source. 

A simple dynamic model is discussed as a first attempt to explain the experimentally observed oscillations in the rate of propylene oxide oxidation on porous silver films in a CSTR. The model assumes that the periodic phenomena originate from formation and fast combustion of surface polymeric structures of propylene oxide. The numerical simulations are generally in qualitative agreement with the experimental results. However, this is a zeroth order model and further experimental and theoretical work is required to improve the understanding of this complex system. The in situ use of IR Spectroscopy could elucidate some of the underlying chemistry on the catalyst surface and provide useful information about surface coverages. This information could then be used to either extract some of the surface kinetic parameters of... 

Use Photographic film, catalyst for ethylene oxide, indelible inks, silver plating, silver salts, silvering mirrors, germicide (as a wall spray), hair dyeing, antiseptic, fused form to cauterize wounds, lab reagent. 

In this work, a cermet electrode structure is developed for the anode structure using a porous borosilicate structure as the mechanical base for the anode structure coated with a thin silver film from the reduction of Ag resinate film to provide a conductive base. The electrode catalysts were added by the reduction of a mixture of platinum/ruthenium resinate. 

Another novel system is presented in Figure 5.9 . This is a crystalline cubic phase formed with monoolein and Myverol . This structure was used to host [Ni (cyclam)] + or the derivative l-hexadecyl-1,4,8,111 tetraaza-cyclotetradecane. After obtaining a mixture of the lipids and the catalyst, the mixture was spread over a glassy carbon electrode or a thin mercury silver film. The best catalyst for the reaction was the substituted complex because the hydrophilic [Ni(cyclam)] + is easily removed from the cubic phase. The voltam-metric results indicate that the best response is obtained on the thin mercury film with formation of CO and regeneration of the catalyst. A further reaction of [Ni(cyclam)] + in the presence of CO generates [Ni(cyclam)CO]. 

Barhieri et al. developed a membrane reactor for water-gas shift 544]. A palladium/ silver film containing 23 wt.% silver, which was between 1- and 1.5-pm thick was produced hy sputtering. This film was coated onto a porous stainless steel support. This patented production method allowed a much higher ratio of pore size to film thickness compared with conventional methods. Tubular membranes of 13-mm outer diameter, 10-20-mm length and 1.1-1.5-pm thickness, respectively, were prepared. A commercial Cu based catalyst supplied by Haldor-Topsoe was used for the water-gas shift reaction. At 210 °C a permeating flux of 4.5 L (m s) was determined for pure hydrogen at 0.2-bar pressure drop. At a reaction temperature of 260-300 °C, and 2085 h gas hourly space velocity, the thermodynamic equilibrium conversion could be exceeded by 5-10% with this new technology. 

Electroless reactions must be autocatalytic. Some metals are autocatalytic, such as iron, in electroless nickel. The initial deposition site on other surfaces serves as a catalyst, usually palladium on noncatalytic metals or a palladium—tin mixture on dielectrics, which is a good hydrogenation catalyst (20,21). The catalyst is quickly covered by a monolayer of electroless metal film which as a fresh, continuously renewed clean metal surface continues to function as a dehydrogenation catalyst. Silver is a borderline material, being so weakly catalytic that only very thin films form unless the surface is repeatedly cataly2ed newly developed baths are truly autocatalytic (22). In contrast, electroless copper is relatively easy to maintain in an active state commercial film thicknesses vary from <0.25 to 35 p.m or more. 

Chemical reduction is used extensively nowadays for the deposition of nickel or copper as the first stage in the electroplating of plastics. The most widely used plastic as a basis for electroplating is acrylonitrile-butadiene-styrene co-polymer (ABS). Immersion of the plastic in a chromic acid-sulphuric acid mixture causes the butadiene particles to be attacked and oxidised, whilst making the material hydrophilic at the same time. The activation process which follows is necessary to enable the subsequent electroless nickel or copper to be deposited, since this will only take place in the presence of certain catalytic metals (especially silver and palladium), which are adsorbed on to the surface of the plastic. The adsorbed metallic film is produced by a prior immersion in a stannous chloride solution, which reduces the palladium or silver ions to the metallic state. The solutions mostly employed are acid palladium chloride or ammoniacal silver nitrate. The etched plastic can also be immersed first in acidified palladium chloride and then in an alkylamine borane, which likewise form metallic palladium catalytic nuclei. Colloidal copper catalysts are of some interest, as they are cheaper and are also claimed to promote better coverage of electroless copper. 

Methanol oxidation on Ag polycrystalline films interfaced with YSZ at 500°C has been in investigated by Hong et al.52 The kinetic data in open and closed circuit conditions showed significant enhancement in the rate of C02 production under cathodic polarization of the silver catalyst-electrode. Similarly to CH3OH oxidation on Pt,50 the reaction exhibits electrophilic behavior for negative potentials. However, no enhancement of HCHO production rate was observed (Figure 8.48). The rate enhancement ratio of C02 production was up to 2.1, while the faradaic efficiencies for the reaction products defined from... 

The experimental apparatus has been described in detail elsewhere (11,12,22). In previous communications we have also described the porous silver catalyst film deposition and characterization procedure (11,12). Ten different reactor-cells were used in the present investigation. The cells differed in the silver catalyst surface area as shown in Table I. Catalysts 2 through 5 had been also used in a previous study (17). The reactor-cells also differed in the zirconia electrolyte thickness which could not be measured accurately. The electrolyte thickness varies roughly between 150 and 300 ym. 

Silver is especially attractive among all metals. As we all know, the composite silver nanomaterials are used in many application fields, such as photoelectricity science, film separation, catalysis, and so on. Composite silver catalyst is usually applied in selective oxidation reaction. ... 

Silver nitrate is probably the most important silver salt. It is used to make most silver salts. It is used in photographic film, indelible ink, and hair dyeing. Other uses are in making silver mirrors, etching ivory, and as a catalyst... 

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