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Zinc-based electrochemical cells

The manufacture of secondary batteries based on aqueous electrolytes forms a major part of the world electrochemical industry. Of this sector, the lead-acid system (and in particular SLI power sources), as described in the last chapter, is by far the most important component, but secondary alkaline cells form a significant and distinct commercial market. They are more expensive, but are particularly suited for consumer products which have relatively low capacity requirements. They are also used where good low temperature characteristics, robustness and low maintenance are important, such as in aircraft applications. Until recently the secondary alkaline industry has been dominated by the cadmium-nickel oxide ( nickel-cadmium ) cell, but two new systems are making major inroads, and may eventually displace the cadmium-nickel oxide cell - at least in the sealed cell market. These are the so-called nickel-metal hydride cell and the rechargeable zinc-manganese dioxide cell. There are also a group of important but more specialized alkaline cell systems which are in use or are under further development for traction, submarine and other applications. [Pg.162]

Example 19.7 shows that an electrochemical cell whose cell reaction involves ions can be used to measure [Ft+] or pH. The pH meter described in Section 15.3 is based on this principle, but for practical reasons the electrodes used in a pH meter are quite different from the SHE and zinc electrode in the electrochemical cell (Figure 19.6). [Pg.774]

The aluminum-oxygen system. The high electrochemical potential and low equivalent weight of aluminum combine to produce a theoretical energy density of 2.6 kWh/kg and make it an attractive candidate as an anode material in metal/air electrochemical cells. The development of aluminum-based cells dates back to 1855 when M. Hulot described a voltaic cell containing aluminum with an acid electrolyte. Since then, many attempts to substitute aluminum for zinc in zinc/carbon and zinc/manganese dioxide cells have been reported. Zaromb first proposed its use in combination with air diffusion electrodes in 1962. Three types of AI-O2 cells have been developed to date ... [Pg.1033]

In the systems based on zinc, the latter serves as the reference electrode and the part of both the internal calibration of the thermocouple in the cell, because the measured values E (T) give a clear kink at the melting point of zinc. The kinetic curve of solidification or melting of the metal also exhibits a characteristic jump EMF at the melting point. Such curve is easily obtained by continuous measurement of the EMF of the cell at the phase transition sol liq. The zinc chloride must not be added to electrolyte previously. We found that the ions, forming the potential, appeared in a few hours inside the cell after the experiment began. We used the metals of 99.999% and chlorides of lithium and potassium 99.99% purity. The type of electrochemical cell for EMF measuring has been used ... [Pg.95]

The indirect cyclisation of bromoacetals via cobaloxime(I) complexes was first reported in 1985 [67], At that time the reactions were conducted in a divided cell in the presence of a base (40yo aqeous NaOH) and about 50% of chloropyridine cobaloximeflll) as catalyst precursor. It was recently found that the amount of catalyst can be reduced to 5% (turnover of ca. 50) and that the base is no longer necessary when the reactions are conducted in an undivided cell in the presence of a zinc anode [68, 69]. The method has now been applied with cobaloxime or Co[C2(DOXDOH)p ] to a variety of ethylenic and acetylenic compounds to prepare fused bicyclic derivatives (Table 7, entry 1). The cyclic product can be either saturated or unsaturated depending on the amount of catalyst used, the cathode potential, and the presence of a hydrogen donor, e.g., RSH (Table 7, entry 2). The electrochemical method was found with some model reactions to be more selective and more efficient than the chemical route using Zn as reductant [70]. [Pg.155]

The general electrochemical procedure for the carbon dioxide incorporation was based on the use of one-compartment cells fitted with consumable anodes of magnesium or zinc [12]. Electrocarboxylations were carried out in DMF at constant current density, using tetrabutylammonium tetrafluoroborate (10 2 m) as supporting electrolyte. The catalyst was introduced in a 10% molar ratio with respect to the substrate and carbon dioxide was bubbled through the solution at atmospheric pressure. Electrolyses were generally run at room temperature and reactions were stopped when starting material was consumed or when the faradaic yield attained 30%. [Pg.214]

Elements such as sodium, potassium and chlorine have primarily an electrochemical or physiological function and are concerned with the maintenance of acid-base balance, membrane permeability and the osmotic control of water distribution within the body. Some elements have a structural role, for example calcium and phosphorus are essential components of the skeleton and sulphur is necessary for the synthesis of structural proteins. Finally, certain elements have a regulatory function in controlling cell replication and differentiation zinc acts in this way by influencing the transcription process, in which genetic information in the nucleotide sequence of DNA is transferred to that of an RNA molecule. It is not uncommon for an element to have a number of different roles for example, magnesium functions catalytically, electrochemically and structurally. [Pg.105]

Figure 2 is a typical alkaline cell construction which uses the same electrochemical couple as the carbon zinc cell. However, in this case the zinc is a powder, in the center of the cell, and the container is made of an inactive material, such as steel. Like carbon zinc cells, the cathode is manganese dioxide. The electrolyte is based on potassium hydroxide (or in some coin cells sodium hydroxide), which explains the use of the term alkaline to describe these cells. [Pg.1731]

Seo KD, Lee MJ, Song HM et al (2012) Novel D-a-A system based on zinc porphyrin dyes for dye-sensitized solar cells synthesis, electrochemical, and photovoltaic properties. Dyes Pigm 94(1) 143-149... [Pg.256]

The antibacterial effect of metal ions and especially silver, copper and zinc ions is well known. Silver and silver ions are used in medicinal treatments ranging from severe burns to Legionnaires Diseases. Silver-based products are also applied in water purification processes. Metal ions achieve their antibacterial effect by two mechanisms First the metal ions influence the electrochemical potential between the internal and external parts of the cell, and second, after penetration of ions into the cell, they compete with other essential ions like magnesium, calcium and potassium and they aggregate with thiol groups of enzymes and proteins. [Pg.34]


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