Oxide cathodes

Molten Carbonate Fuel Cell. The electrolyte ia the MCFC is usually a combiaation of alkah (Li, Na, K) carbonates retaiaed ia a ceramic matrix of LiA102 particles. The fuel cell operates at 600 to 700°C where the alkah carbonates form a highly conductive molten salt and carbonate ions provide ionic conduction. At the operating temperatures ia MCFCs, Ni-based materials containing chromium (anode) and nickel oxide (cathode) can function as electrode materials, and noble metals are not required. 

Other Specialty Chemicals. In fuel-ceU technology, nickel oxide cathodes have been demonstrated for the conversion of synthesis gas and the generation of electricity (199) (see Fuel cells). Nickel salts have been proposed as additions to water-flood tertiary cmde-oil recovery systems (see Petroleum, ENHANCED oil recovery). The salt forms nickel sulfide, which is an oxidation catalyst for H2S, and provides corrosion protection for downweU equipment. Sulfur-containing nickel complexes have been used to limit the oxidative deterioration of solvent-refined mineral oils (200). 

However, even at room temperature, the shelf-life of batteries with nickel oxide cathodes (Ni-Cd, Ni-MeHy, and Ni-Zn batteries) is a source of difficulties for the consumer who relies on the state of charge of his power source when he needs it-without charging time available. Figure 7 compares the self-discharge of RAM cells with Ni-Cd and Ni-MeHy cells at 20 °C. 

It is so universally applied that it may be found in combination with metal oxide cathodes (e.g., HgO, AgO, NiOOH, Mn02), with catalytically active oxygen electrodes, and with inert cathodes using aqueous halide or ferricyanide solutions as active materials ("zinc-flow" or "redox" batteries). The cell (battery) sizes vary from small button cells for hearing aids or watches up to kilowatt-hour modules for electric vehicles (electrotraction). Primary and storage batteries exist in all categories except that of flow-batteries, where only storage types are found. Acidic, neutral, and alkaline electrolytes are used as well. The (simplified) half-cell reaction for the zinc electrode is the same in all electrolytes ... 

Some battery-producing companies prefer purchasing pure, nonamalgamated zinc powder to apply their own proprietary corrosion protection system. The general trend is to keep the anodes of all the consumer cells mercury-free (usually indicated by a "green label) and to make them disposable with the regular household trash. The exceptions to this rule are those cells where this makes no sense, such as cells with a mercuric oxide cathode. 

Another group of important battery characteristics are the lifetime parameters. For primary batteries and charged storage batteries, a factor of paramount importance is the rate of self-discharge. Self-discharge may be the result of processes occurring at one of the electrodes (e.g., corrosion of zinc in batteries with zinc anodes or the decomposition of higher metal oxides in batteries with oxide cathodes), or it... 

B.Ya. Moizhes, Physical Processes in Oxide Cathode, Nauka Publ., Moscow, 1968... 

The air gas-diffusion electrode possesses two advantages over the metal-oxide cathode in the conventional primary batteries infinite charge... 

Im, D., Manthiram, A., Amorphous Manganese Oxide Cathodes for Rechargeable Lithium Batteries, Ceramic Trans., 127, 205 (2002). 

The cells shown in Figs. 28 and 29 all operate according to the same principles, which have been developed by Arup. The interior of the cell acts as the anode chamber, and a metal oxide cathode placed inside the cell in an alkaline electrolyte acts as the counter electrode. The hydrogen flux across the integrated membrane (coated with palladium on the internal surface) can be measured as the potential drop across a resistor placed between the membrane and the counter electrode. 

Fig. 9-16. Polarization curves of anodic oxidative dissolution and cathodic reductive dissolution of semiconductor electrodes of an ionic compound MX iiixcp) (iMxh )== anodic oxidative (cathodic reductive) dissolution current solid curve = band edge level pinning at the electrode interface, dashed curve = Fermi level pinning.

Although not yet optimized for C-C bond formation, these reactions demonstrated the potential for using mixed anodic oxidation - cathodic reduction sequences for initiating transformations that would be difficult to accomplish using more conventional chemical routes. It is hard to imagine putting a strong... 

Figure 1. Schematic description of a (lithium ion) rocking-chair cell that employs graphitic carbon as anode and transition metal oxide as cathode. The undergoing electrochemical process is lithium ion deintercalation from the graphene structure of the anode and simultaneous intercalation into the layered structure of the metal oxide cathode. For the cell, this process is discharge, since the reaction is spontaneous.

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