Cadmium redox reactions

The relatively simple chemistry of this redox reaction is one reason why nickel-cadmium batteries are rechargeable. As we show later in this chapter, applying an external voltage can reverse this reaction. 

To estimate the thermodynamic feasibility of interfacial redox reactions at a hitherto unknown semiconductor surface, it is therefore of basic importance to know the position of the quasi-Fermi level. The quasi-Fermi level of electrons of powders or thin films of modified titania photocatalysts can be easily obtained by the suspension method developed by Bard et al. (9,10) and modified by Roy et al. (11) for titania and cadmium sulfide. It is based on the pH-dependence of the flat-band potential of Ti02-... 

When cadmiiun atoms are sorbed into Cd2+-containing zeolites, redox reaction occurs to give cadmium ions in the 1+ oxidation state. These are found both as discrete Cdl" " cations and dimers. In addition, neutral atoms may be sorbed without oxidation, in one... 

In the redox reaction that takes place during discharge, nickel oxide Is reduced at the cathode, and cadmium Is oxidized at the anode. 

Leclanche cells are not rechargeable once the reactants are depleted, the battery must be discarded and replaced. Batteries that are not rechargeable are called primary batteries. A rechargeable battery is called a secondary battery or a storage battery. The nickel-cadmium (NiCd) battery is a popular rechargeable battery that uses the following redox reaction ... 

The nickel-cadmium (nicad) battery uses the following redox reaction to generate electricity ... 

SECTION 20.7 A battery is a self-contained electrochemical power source that contains one or more voltaic cells. Batteries are based on a variety of different redox reactions. Several common batteries were discussed. The lead-acid battery, the nickel-cadmium battery, the nickel-metal-hydride battery, and the lithium-ion battery are examples of rechargeable batteries. The common alkaline dry cell is not rechargeable. Fuel cells are voltaic cells that utilize redox reactions in which reactants such as H2 have to be continuously supplied to the cell to generate voltage. 

All these galvanic cells produce electricity until they run out of a reactant. Then they must be discarded. However, there are cells (batteries) that can be recharged, as the redox reaction can be reversed to regenerate the original reactants. Nickel-cadmium (Ni-Cad) and lithium batteries fall into this category. The most familiar type of rechargeable battery is probably the automobile battery. 

If this thermal decomposition occurs in the presence of excess chloride, chlorine is produced by the action of nascent oxygen at its point of origin. Accordingly, in a mixture of alkali perchlorate and cadmium chloride, which melts without decomposition at 568 C, there occurs in addition to (1) the redox reaction... 

Additionally, in 1901, the Swedish engineer Waldemar Jungner and Thomas Edison invented the rechargeable nickel-cadmium battery, whose redox reaction during the charge and discharge processes is shown in Equation 1.2, and its open-circuit voltage is about 1.35 V. 

Especially transition metal icMis play an important role in the induction of oxidative DNA damage. While neither superoxide anions nor hydrogen peroxide are able to react with DNA directly, in the presence of transition metals like iron, copper, cobalt, or nickel they are converted into highly reactive hydroxyl radicals by Fenton-type reactions. In contrast, cadmium ions are not able to participate in redox reactions under physiological conditions, yet, oxidative stress and the interference with cellular redox regulation may be of high relevance in cadmium-induced carcinogenicity. Increased levels of ROS due to cadmium exposure have been observed both in vitro and in vivo [31]. Different cadmium compounds have been shown to induce DNA strand breaks and oxidative DNA base modifications in... 

Zinc-carbon, alkaline, and mercury cells are primary batteries, which are not rechargeable. Batteries that are rechargeable are called secondary batteries, or storage batteries. A storage battery produces energy from a reversible redox reaction, which occurs in the opposite direction when the battery is recharged. A nickel-cadmium rechargeable battery is an example of a secondary battery. 

Write a balanced redox equation for the reaction of cadmium with aqua regia, assuming the products include CdCl42 and NO(g). 

A redox half-reaction at an active electrode also may convert one metal salt into another. For example, the cathode In a nickel-cadmium battery is NiO(OH), which is reduced to nickel(II) hydroxide. The half-reaction reduces... 

Metallothioneins (MT) are unique 7-kDa proteins containing 20 cysteine molecules bounded to seven zinc atoms, which form two clusters with bridging or terminal cysteine thiolates. A main function of MT is to serve as a source for the distribution of zinc in cells, and this function is connected with the MT redox activity, which is responsible for the regulation of binding and release of zinc. It has been shown that the release of zinc is stimulated by MT oxidation in the reaction with glutathione disulfide or other biological disulfides [334]. MT redox properties led to a suggestion that MT may possesses antioxidant activity. The mechanism of MT antioxidant activity is of a special interest in connection with the possible antioxidant effects of zinc. (Zinc can be substituted in MT by some other metals such as copper or cadmium, but Ca MT and Cu MT exhibit manly prooxidant activity.)... 

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