Ionic liquids molten salts, extension

Recently, room-temperature ionic liquids (molten salts) have been extensively studied in order to replace volatile organic solvents by them in electrochemical devices such as batteries. Interest in these materials is stimulated by their properties (e.g., high ionic conductivity, good electrochemical stability, and low volatility). Among these properties, the low volatility is the most critical for ensuring the long-term stability of electrochemical devices. Room-temperature ionic liq-... 

The early history of ionic liquid research was dominated by their application as electrochemical solvents. One of the first recognized uses of ionic liquids was as a solvent system for the room-temperature electrodeposition of aluminium [1]. In addition, much of the initial development of ionic liquids was focused on their use as electrolytes for battery and capacitor applications. Electrochemical studies in the ionic liquids have until recently been dominated by work in the room-temperature haloaluminate molten salts. This work has been extensively reviewed [2-9]. Development of non-haloaluminate ionic liquids over the past ten years has resulted in an explosion of research in these systems. However, recent reviews have provided only a cursory look at the application of these new ionic liquids as electrochemical solvents [10, 11]. 

Eutectic mixtures have been used extensively for applications of molten salts to reduce the operating temperature and this is where the significant area of ionic liquids developed from i.e. the quest to find aluminum-based salt mixtures. While the development of aluminum-containing ionic liquids is technologically very important for the field of metal deposition it is clear that there are many other issues that also need to be addressed and hence methods need to be developed to incorporate a wide range of other metals into ionic liquid formulations. 

Teachers need to be aware of two different uses of the term electrolyte . In the strict sense, an electrolyte is a liquid that cm undergo electrolysis. This can be a single substance, as in the case of a molten salt, or a solution. The most typical electrolytes are the aqueous solutions of salts (in general of ionic compounds), of acids, and of bases. By extension, we also call electrolytes the pure substances (solid, liquid, or gaseous) that, when dissolved in water, provide liquid electrolytes. Some biological substances (such as DNA or polypeptides) and synthetic polymers (such as polystyrene sulfonate) contain multiple charged functional groups and their dissolution leads to electrolyte solutions these are termed polyelectrolytes. 

In conclusion, it appears that few metal-molten salt systems behave in the ideally polarizable sense generally associated with the mercury/aqueous solution interface at 298 K. Possible exceptions include some noble liquid metal/melt systems such as mercury/molten nitrates and lead/molten halides at low temperatures (<773 K), but only when the molten electrolyte is extensively purified. Otherwise, systems need to be analyzed as complex impedances, using ac or pulse techniques, to determine whether the minimum interfacial capacitance is affected by extensive factors, leading to parallel pseudocapacitances and Faradaic components. The range of potentials and measuring frequencies for which the interface approaches ideally polarizable behavior also needs to be established. It now seems clear that the multilayer ionic model of charge distribution at the metal/melt interface is more pertinent to molten media than the familiar double layer associated with aqueous solutions. However, the quantitative theories derived for the former model will have to be revised if it is confirmed that the interfacial capacitance is, indeed, independent of temperature in the ideally polarizable region. 

Atomic molten salts such as the alkali halides have been studied extensively using experimental methods such as neutron diffraction and extended X-ray absorption fine structure, enabling their structures in the liquid melt to be quantified. Investigations were pioneered by Enderby and co-workers, who began with molten NaCl [2], perhaps now the best known exanple of such structural research. Their work demonstrated clearly the charge ordering within the system and has become the standard tenplate for the liquid structure of purely ionic binary melts. The radial distribution functions (RDFs) obtained from the study for all pairs of ions in molten NaCl are shown in Figure 4.1. in which the prominent feature is the maximum in... 

In 1983, the first report on the conversion of fructose to 5-HMF in the presence of pyridinium chloride with 70% yield under mild reaction conditions (30 min, 120 °C) was published [30]. This sparked an interest in investigating the dehydration of fructose over molten salts. Twenty years later, in 2003, Lansalot-matras et al. revisited the field and investigated the acid-catalyzed dehydration of fructose in commercially available ionic liquids, ([BMIM][BF4]) and ([BMIM][PF6]) with DMSO as co-solvent in the presence of Amberlyst-15 [31]. They demonstrated the advantages of using ILs as solvents and reported a yield of 80% for 5-HMF in 24 h and at a relatively low temperature of 80°C compared to that employed in the previous method. However, conventional methods require much higher temperatures of 100 to 300°C [31]. In an effort to further improve the dehydration reaction, the following reaction p>arameters were studied extensively with promising results ... 

Reiss and Mayer and Mayer - have also made extensive computations of values of the surface tension of molten ionic salts, liquid metals, and simple nonpolar and polar liquids using Eq. (97) or simple modifications thereof, obtaining results in remarkable agreement with experimental values. 

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