Ambient-temperature molten salts

Osteryoung, R. A., Organic Chloroaluminate Ambient Temperature Molten Salts, in Molten Salt Chemistry-An Introduction and Selected Applications, G. Mamantov and R. Marassi, Editors. 1987, D. Reidel Publishing Company Dordrecht, p. 329. 

Formation of several successive layers of bulk intermetallic compounds has been shown. Also, Lee et al. [480] have detected, during Al UPD, the formation of two alloys on polycrystalline Au electrodes from acidic l-ethyl-3-methylimidazolium chloroaluminate that melt at room temperature. Moreover, in the Al UPD region, fast phase transition between these two intermetallic compounds has been evidenced. Later, the same group of researchers [481] has performed EQCM studies on Al deposition and alloy formation on Au(lll) in ambient temperature molten salts/benzene mixtures. 

Bonhote, P. et al.. Hydrophobic, highly conductive ambient-temperature molten salts, Inorg. Chem., 35, 1168, 1996. 

Between 1980 and about 2000 most of the studies on the electrodeposition in ionic liquids were performed in the first generation of ionic liquids, formerly called room-temperature molten salts or ambient temperature molten salts . These liquids are comparatively easy to synthesize from AICI3 and organic halides such as Tethyl-3-methylimidazolium chloride. Aluminum can be quite easily be electrode-posited in these liquids as well as many relatively noble elements such as silver, copper, palladium and others. Furthermore, technically important alloys such as Al-Mg, Al-Cr and others can be made by electrochemical means. The major disadvantage of these liquids is their extreme sensitivity to moisture which requires handling under a controlled inert gas atmosphere. Furthermore, A1 is relatively noble so that silicon, tantalum, lithium and other reactive elements cannot be deposited without A1 codeposition. Section 4.1 gives an introduction to electrodeposition in these first generation ionic liquids. 

Ambient temperature molten salt can be obtained by several methods. One effective way to obtain a room-temperature molten salt is by the introduction of polyether chains to ions. The term polyether/salt hybrid is used in this chapter as a common name for polyether oligomers having anionic or cationic charge(s) on the chain (Figure 22.1). Polyethers, such as poly-(ethylene oxide) (PEO), are known as representative ion conductive polymers [1]. Polyether/salt hybrids have been studied as a kind of room-temperature molten salt apart from the development of onium-type ionic liquids [2]. The preparation of ionic liquids consisting of metal ions has been one of the important goals in this research field. Polyether/salt hybrid derivatives give one such solution for this task. 

Finally it should be noted that ambient-temperature molten salts such as 1-ethyl-3-methylimidazolium chloride have been studied in connection with the solution of organics such as anthracene [475] or dimethylaniline [476]. Naturally, the classical high-temperature salt melts are prohibitive for organic batteries, which must work near room temperature. 

Papageorgiou N, Athanassov Y, Armand M, et al. The performance and stabihty of ambient temperature molten salts for solar cell applications. J. Electrochem. Soc. 1996. 143, 3099-3108. 

Singh P., Rajeshwar K., Dubow 1. and lob R. (1980a), Photoelectrochemical behavior of n-GaAs electrodes in ambient-temperature molten-salt electrolytes , J. Am. Chem. Soc. 102, 4676-4681. 

KouraN, Matsumoto S, Idemoto Y (1998) Electrodeposition of amorphous Co-Zn alloy from ambient-temperature molten salt electrolytes of EMIC system. J Surf Fin Soc Jpn 49 1215-1220 (in Japanese)... 

Lapkowski s report. These observations suggest that the conductivity and the spin density do not parallel each other as the maximum conductivity is observed between the two oxidation peaks. In other words, the charge carriers must be bipolarons instead of polarons. This question was addressed by Tang et al. [208], who made EPR measurements in an ambient temperature molten salt. They found that a one-to-one relation is observed up to about 25% of full oxidation between the number of spins and the number of electrons removed from the PAn matrix. The number of spins then fell off rapidly in comparison to the number of electrons removed. This observation was interpreted in terms of a comproportionation reaction of neutral and bipolaronic form of PAn, i.e.. 

Pickup, P. G., and Osteryoung, R A (1984). Electrochemical polymerization of pyrrole and electrochemistiy of pofypyrrole films in ambient temperature molten salts. ]. Am Chem Soc, 106, pp. 2294-2299. 

Koura, N., Ejiri, H., and Takeishi, K. (1993). Potyaniline secondaiy cells with ambient temperature molten salt electrolytes. ]. Electrochem Soc., 140, pp. 602-605. 

Janiszewska, L., and Osteiyoung, R. A. [1987]. Electrochemistry of polythiophene and polybithiophene films in ambient temperature molten salts,/ Electrochem. Soc., 134, pp. 2787-2794. 

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