Nickel iron oxide electrodes

The nickel-based systems include the flowing systems nickel—iron (Ni/Fe), nickel—cadmium (NiCd), nickel—metal hydrides (NiMH), nickel—hydrogen (Ni/ H2), and nickel—zinc (Ni/Zn). All nickel systems are based on the use of a nickel oxide active material (undergoing one valence change from charge to discharge or vice versa). The electrodes can be pocket type, sintered type, fibrous type, foam type, pasted type, or plastic roll-bonded type. All systems use an alkaline electrolyte, KOH. 

Electrochemical detection of carbohydrates at nickel-copper and nickel-chromium-iron alloy electrodes has been reported for sorbitol, and has been used as a detector for HPLC analysis [36]. Oxidation of various carbohydrates at the electrodes was used for detection, and baseline separation was achieved for mixtures of sorbitol, rhamnose, glucose, arabinose, and lactose. 

In alkaline solution nickel(ll) hydroxide can be oxidized to a hydrated nickel(IV) oxide, Ni02vvH20. This reaction is used in the Edison storage cell. The electrodes of this cell are plates coated with Ni02-A H20 and metallic iron, which are converted on discharge of the cell into nickel(Il) hydroxide and ferrous hydroxide, respectively. The electrolyte in this cell is a solution of sodium hydroxide. 

Nickel-based positive electrode made of 3 to 95 wt% NiOH balance consists of either nickel powder, cobalt powder, or carbon powder, possibly in combination. Carbon-based negative electrode made of 10 to 95 wt% carbon, with balance consisting of at least one metal oxide from group of bismuth oxide, iridium oxide, cobalt oxide, iron oxide, and iron hydroxide, and hydride from Groups IIIA, IIIB, IVA, IVB, VB, VIB, VIIB,andVIIIB. 

The active materials of the nickel-iron battery are metallic iron for the negative electrode, nickel oxide for the positive, and a potassium hydroxide solution with lithium hydroxide for the electrolyte. The nickel-iron battery is unique in many respects. The overall electrode reactions result in the transfer of oxygen from one electrode to the other. The exact details of the reaction can be very complex and include many species of transitory existence.The electrolyte apparently plays no part in the overall reaction, as noted in the following reactions ... 

The stainless steels (types 303, 316, and 316LVM) as well as the cobalt-nickel-chromium-molybdenum alloy MP35N are protected from corrosion by a thin passivation layer that develops when exposed to atmospheric oxygen and which forms a barrier to further reaction. In the case of stainless steel, this layer consists of iron oxides, iron hydroxides, and chromium oxides. These metals inject charge by reversible oxidation and reduction of the passivation layers. A possible problem with these metals is that if the electrode potential becomes too positive... 

We have investigated copper preparations (Raney s and others), Raney nickel, zinc oxide, iron oxide, vanadium quin-toxide (VjOg), silica gel (SiOj) and some varieties of silicon dioxide applied as carriers, zinc ferrocyanide pure, and with Fe + and Cu + ions, a cobalt-thorium contact for Fischer and Tropsch s s5mthesis, zinc hydroxide with Co + ions, and silica gel with nickel sulphate (II) fixed on it. We have investigated contact fixed on a carrier and without a carrier, with additions of an activator, etc. For example, Co + ions on Zn(0H)2 could be clearly detected potentiometrically and still in the quantity of 3.10 g Co + to a powder electrode. 

Welding is the joining of metal to metal by use of heat and/or pressure. The main fume generated by consumable electrodes is iron oxide. Cadmium, chromium, beryllium, aluminum, titanium, and nickel may also be present. Exposure to welding fumes is known to be a risk factor for chronic respiratory disorders - such as pneumoconiosis, chronic bronchitis, and lung cancer (Sferlazza and Beckett 1991). 

Porous anodes of nickel, stainless steel, stainless steel with iron-iron oxide mixtures, lithiated manganous oxide, and silverized catalysts (Rh, Co, Zn, ZnO, Mn02, C02O3, lithiated NiO) have been tested. The difference in the reactivity of these electrodes for the H2 oxidation is not large at temperatures between 500 °C and 700 °C. The presence of oxides improves the performance of the anode for hydrogen gas containing some carbon monoxide. Stainless steel, nickel, silver, lithiated nickel... 

However, reliable information about dependence of the functional properties of complex nickelates on their chemical composition and structure is still absent, while any straightforward and accelerated design of cathode materials is to be based upon reliable (and independent upon their interaction with electrolyte) characterization of the ability of then-surface sites to catalyze the oxygen reduction as well as of oxygen mobility in the bulk. Several lanthanum-nickel-iron mixed oxides with perovskite structure have demonstrated promising performance as cathodes for IT SOFC with traditional YSZ and GDC electrolytes [111-112]. However, studies of the behavior of electrode materials in contact with ATLS electrolytes or that of ATLS-based composites are veiy scarce [113]. 

The metal oxides used to make positive electrode materials for lithium-ion batteries commonly include lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, vanadium oxide, and various others, such as iron oxides. Positive electrode materials of 5 V and polyanion-type positive electrode materials (so far mainly referring to lithium iron phosphate, LiFeP04) have also been investigated. Among the primary materials for these positive electrode materials, cobalt is the most expensive, followed by nickel and then manganese and vanadium. As a result, the prices of positive electrode materials are basically in line with the market prices of the primary materials. The structures of these positive electrode materials are mainly layered, spinel, and oliven. 

Passivity has been attributed, since the time of Faraday, to an oxide film. In a few cases the presence of this has been directly demonstrated, and the response of a passive electrode to pH changes is very much that of a metal-metal oxide electrode. Uncertainties still exist, however, as to the nature and thickness of the surface film. On platinum, nickel and iron the onset of passivation may only require a monolayer of oxide, or of adsorbed oxygen atoms, although a layer several Angstroms thick may be produced in time. Evidence for these very thin layers, which are quite undetectable visibly, comes from the very small cathodic pulse of electricity that is sufficient to remove them. In other cases, e.g. lead, quite thick films are needed to preserve the passive state. Partial protection is obtained for many metals in a variety of electrolytes so long as conditions favour the precipitation of a film of insoluble hydroxide or salt (see Anodising),... 

The investigations [40], using model fuel cells (Figure 2.5a), were started with iron oxides, magnesium ferrite (following Biefeld [41]) and composites of iron and alumina as electrodes and were continued mainly with thin porous layers of platinum, nickel and iron. Very soon it was seen that completely gastight solid electrolyte discs of highly pure substances had to be produced if the... 

The discharge-charge reaction of this electrode will be done in two steps but only the first step (Fe <-> Fe2+ + 2e ) is of practical use. For the iron/nickel oxide-hydroxide system these steps (or voltage plateaus) may be written as ... 

In acidic electrolytes only lead, because it forms passive layers on the active surfaces, has proven sufficiently chemically stable to produce durable storage batteries. In contrast, in alkaline medium there are several substances basically suitable as electrode materials nickel hydroxide, silver oxide, and manganese dioxide as positive active materials may be combined with zinc, cadmium, iron, or metal hydrides. In each case potassium hydroxide is the electrolyte, at a concentration — depending on battery systems and application — in the range of 1.15 - 1,45 gem"3. Several elec-... 

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