Cathodes silver oxide

The anode is Zn metal, the cathode silver oxide (most coimnonly as Ag20) and the electrolyte an alkaline solution (20-45% KOH or NaOH). The overall reaction is ... 

Fig. 1. Schematic representation of a battery system also known as an electrochemical transducer where the anode, also known as electron state 1, may be comprised of lithium, magnesium, zinc, cadmium, lead, or hydrogen, and the cathode, or electron state 11, depending on the composition of the anode, may be lead dioxide, manganese dioxide, nickel oxide, iron disulfide, oxygen, silver oxide, or iodine.

Zinc—Silver Oxide Batteries. Miniature 2inc—silver oxide batteries have a 2inc anode, and a cathode containing silver oxide [20667-12-3] Ag20. The cathode reaction... 

The cathode reaction involves reduction of silver oxide to metallic silver [7440-22-4J. The reaction is a two-phase, heterogeneous reaction producing a substantially constant voltage during discharge. Some manganese dioxide may be added to the cathode, as in the case of mercury oxide cells. 

Since the reaction between hydrogen and oxygen is very slow at room temperature, catalysts are incorporated in the carbon electrodes. At the anode, suitable catalysts are finely divided into platinum or palladium at the cathode, cobaltous oxide, or silver. The two halfreactions shown above yield the overall result as ... 

Two common types of button batteries both use a zinc container, which acts as the anode, and an inert stainless steel cathode, as shown in Figure 11.11 on the next page. In the mercury button battery, the alkaline electrolyte paste contains mercury(II) oxide, HgO. In the silver button battery, the electrolyte paste contains silver oxide, Ag20. The batteries have similar voltages about 1.3 V for the mercury cell, and about 1.6 V for the silver cell. 

Chromium tetraphenyl iodide in methyl alcohol or moist chloroform is treated with silver oxide, or the iodide is subjected to electrolysis, using an alcohol solution with a platinum or mercury cathode and a rotating silver anode. One molecule of wTater is removed by drying over calcium chloride. The base forms orange-coloured plates, M.pt. 104° to 105° C. when placed in a bath previously heated to 95° C. It dissolves readily in water or alcohols, is sparingly soluble in chloroform, insoluble in benzene or ether. Measurements of its conductivity in aqueous solution show that it is comparable in strength with the alkali hydroxides, whilst comparative tests in methyl alcohol solution show that it is a stronger base than chromium pentaphenyl hydroxide. It may readily be converted into the chloride, bromide and iodide. 

Nowadays, the most commonly used DO electrode is the polarographic that employs an electrochemical method, through the reduction of molecular oxygen at the platinum electrode (cathode) generating electrons for the silver oxidation at the silver/silver chloride electrode (anode). In this type of sensor, it is necessary to impose an external voltage and the resulting current is measured and converted into dissolved oxygen concen-... 

Dissolved oxygen polarographic electrode (InPro 6050, Mettler-Toledo, 2006) The cathode, where the half-reaction with 02 (02 + 2H20 + 4e —> 40H ) takes place, is in contact with a membrane, that allows the transport of the dissolved oxygen from the external medium. At the anode, the silver oxidation (Ag + Cl- —> AgCI + e ) takes place. 

The absence of silver oxidation and/or reduction peaks is evidence for the electrochemical inactivity of the silver deposited on this carbon (in the form of metallic crystallites). The cyclic voltammogram recorded for the D—Ox carbon (Fig. 50, curve 2) exhibits two anodic peaks (fp., = +0.27 V, p,a = +0.77 V) due to the oxidation of adsorbed silver and surface hydroquinone-like groups, respectively. A single cathodic peak (Ep,) = +0.16 V) is due to the reduction of quinone-like surface groups according to Scheme 19. The large cathodic reduction wave confirms the presence of adsorbed silver cations and their reduction... 

The cyclic voltammograms of all the carbons carrying preadsorbed silver, recorded in dilute nitric acid solution (Fig. 51), exhibit a Ag"/Ag" couple (cathodic wave < +0.4 V and an anodic response in the +0.40-0.60 V potential range), as well as the electroactive quinone/hydroquinone-like surface system ( p, s +0.50 V p.a2 = +0.90 V). The presence of distinctly shaped anodic silver oxidation peaks indicates the partial solution of sorbed (deposited) metal. An almost sixfold higher anodic peak for D—Ox carbon confirms the partially ionic form of the adsorbed silver. 

Electroplating Objects can be electroplated with a metal such as silver in a method similar to that used to refine copper. The object to be silver plated is the cathode of an electrolytic cell that has a silver anode, as shown in Figure 21-21. At the cathode, silver ions present in the electrolyte solution are reduced to silver metal by electrons from an external power source. The silver forms a thin coating over the object being plated. The anode consists of a silver bar or sheet, which is oxidized to silver ions as electrons are removed by the power source. Current passing through the cell must be carefully controlled in order to get a smooth, even metal coating. 

Silver oxide cells were developed in the 1960s. These cells use silver oxide mixed with carbon (to increase the electronic conductivity of the material) as cathode, amalgamated pellet zinc powder as anode, and a solution of potassium hydroxide or sodium hydroxide with dissolved zin-cates in water as electrolyte. Permion (a radiation graft of methacrylic acid onto a polyethylene membrane) is used as separator. The cell reactions are... 

Several molecules were investigated because of the applicability in a system of interest. Silver oxide was investigated by Kotz and Yeager" for the significance of the silver/silver oxide electrode as a cathode in batteries and as a catalyst for oxygen reduction. Mercaptobenzothiazole was studied" " for its role as a corrosion inhibitor for several metals. Von Raben et could follow... 

Unlike some other cathode materials, such as manganese dioxide, which are quite insoluble, silver oxide has a fair degree of solubility in alkaline electrolyte. If the soluble silver species were allowed to be transported to the zinc anode it would react directly with the zinc, and as a result the cell would self-discharge. In order to prevent this from happening, zinc—silver oxide cells use special separator materials such as cellophane [9005-81-6], that are designed to inhibit migration of soluble silver to the anode. 

Batteries. Primary, ie, nonrechargeable, batteries containing silver compounds have gained in popularity through use in miniaturized electronic devices. The silver oxide—zinc cell has a cathode of Ag-O or AgO. These cells are characterized by a high eneigy output per unit weight and a fairly... 

Although it looks different, the silver battery is much like the alkaline battery. The silver battery uses silver oxide (Ag20) in the cathode instead of manganese(IV) oxide (Mn02). 

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