Electrochemical Devices and Applications

There is an extended special literature on applications of soUd state electrochemistry and even more on electrochemical devices. According to our objective, in this section appUcations will be emphasized in which migration and diffusion in the solid state are decisive processes (as discussed in Part 1 ). We intend to subsume such applications under the headlines composition sensors, composition actors, and energy storage or conversion devices. 

Electrochemical devices allow for the conversion of chemical energy or information into electrical energy or information, or vice versa. One characteristic feature of the solid state in this respect is the thermal and mechanical stability which allows performance at 

We will begin with a description of electrochemical sensors or more specifically composition sensors based on electrochemical principles (i.e., we refer to an electrochemical detection of composition). Another group of applications refers to devices in which the transference of mass and charge is used primarily to change composition or produce chemicals (electrochemical pumps and electrochemical reactors, or electrochemical filters) we will term such devices composition actors. At the end we will discuss energy conversion and storage devices (which we do not subsume under the term composition actors as here the energy aspect is to the fore). 

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Electrolytes are ubiquitous and indispensable in all electrochemical devices, and their basic function is independent of the much diversified chemistries and applications of these devices. In this sense, the role of electrolytes in electrolytic cells, capacitors, fuel cells, or batteries would remain the same to serve as the medium for the transfer of charges, which are in the form of ions, between a pair of electrodes. The vast majority of the electrolytes are electrolytic solution-types that consist of salts (also called electrolyte solutes ) dissolved in solvents, either water (aqueous) or organic molecules (nonaqueous), and are in a liquid state in the service-temperature range. [Although nonaqueous has been used overwhelmingly in the literature, aprotic would be a more precise term. Either anhydrous ammonia or ethanol qualifies as a nonaqueous solvent but is unstable with lithium because of the active protons. Nevertheless, this review will conform to the convention and use nonaqueous in place of aprotic .]... 

Yang, Z., Coyle, C.A., Baskaran, S., and Chick, L.A. (2005) Gas-tight metal/ceramic or metal/metal seals for applications in high temperature electrochemical devices and method of making. US Patent 6,843,406. 

Redox Reactions. For many electrochemists the paramount concern of their discipline is the reduction and oxidation (redox) reaction that occurs in electrochemical cells, batteries, and many other devices and applications. Reduction takes place when an element or radical (an ionic group) gains electrons, such as when a double positive copper ion in solution gains two electrons to form metallic copper. Oxidation takes place when an element or radical loses electrons, such as when a zinc electrode loses two electrons to form a doubly positive zinc ion in solution. In electrochemical research and applications the sites of oxidation and reduction are spatially separated. The electrons produced by chemical processes can be forced to flow through a wire, and this... 

Today, the behavior of ions in bulk systems and near surfaces is widely understood. This is not so for confined media, such as ion channels, where much work remains to be done, especially as far as transport properties of ions in confinement is concerned. Solid electrolytes will continue to play an important role for electrochemical devices and polyelectrolytes are already ubiquitous in industrial applications. By contrast, the fumre of Ionic Liquids is not easy to predict. These systems have still to prove that their undisputed advantages weigh more heavily than their disadvantages. 

Overall, this chapter will feature about the preparation, most important electrochemical characterization, and application of advanced carbon materials used in SPE electrochemical devices [e.g., graphite, boron-doped diamond, graphene, carbon nanotubes, carbon black. 

Further, the first electrochemical devices based on oxide ion-conducting solid electrolytes, i.e., solid oxide fuel cells, water vapor electrolyzers, and oxygen concentrators, were also developed in the Institute of High-Temperature Electrochemistry. In 1978 the Laboratory of Physical and Chemical Properties of Solid Electrolytes has been renamed to the Solid Electrolytes Laboratory. Different cation-conductive solid electrolytes were investigated in the laboratory. Oxide semiconductor materials with fast ion and electron transport have been studied for different electrode applications in high-temperature electrochemical devices and MHD generators. 

Some perovskite-type oxides show protonic conduction and are useful for hydrogen-related electrochemical devices, including application to solid oxide fuel cells (SOFCs). Iwahara et al. reported protonic conductivity of strontium-cerate-based perovskite-type oxides in 1981 [1], Since that time, various perovskite-type proton-conducting oxides have been found. For use of the proton-conducting perovskite oxides, we should understand not only their merits but also their weak points. This chapter concerns the protonconducting properties of typical cerium- and zirconium-containing perovskite oxides from the points of view of conductivity, stability, electrode affinity, and dopant effect. Mixed conduction occurring in a special composition of the perovskite oxide is also introduced. 

PFSA membranes have excellent chemical inertness and mechanical integrity in a corrosive and oxidative environment, and their superior properties allowed for broad application in electrochemical devices and other fields such as superacid catalysis, gas drying or humidification, sensors, and metal-ion recovery. Here, we refer their important applications in electrochemical devices for energy storage and conversion including PEMFC, chlor-alkali production, water electrolysis, vanadium redox flow batteries, lithium-ion batteries (LIBs), and solar cells. 

The creation of this cover design has gone through many versions of artwork by Elise Weinger. The cover design was adapted from the Tai CM symbol. It is not our intention to advocate or to discredit Taoism. Similarities are drawn between Yin-Yang and the polarity in electrochemical conversion. Dynamic interactions of polarity and ions leads to devices and applications. Connotations of recycle, regeneration, conversion, and harmony build the vision of sustainability. 

There are various ways in which CMEs can benefit analytical applications. These include acceleration of electron-transfer reactions, preferential accumulation, or selective membrane permeation. Such steps can impart higher selectivity, sensitivity, or stability to electrochemical devices. These analytical applications and improvements have been extensively reviewed (35-37). Many other important applications, including electrochromic display devices, controlled release of drugs, electrosynthesis, and corrosion protection, should also benefit from the rational design of electrode surfaces. 

The presence of polymer, solvent, and ionic components in conducting polymers reminds one of the composition of the materials chosen by nature to produce muscles, neurons, and skin in living creatures. We will describe here some devices ready for commercial applications, such as artificial muscles, smart windows, or smart membranes other industrial products such as polymeric batteries or smart mirrors and processes and devices under development, such as biocompatible nervous system interfaces, smart membranes, and electron-ion transducers, all of them based on the electrochemical behavior of electrodes that are three dimensional at the molecular level. During the discussion we will emphasize the analogies between these electrochemical systems and analogous biological systems. Our aim is to introduce an electrochemistry for conducting polymers, and by extension, for any electrodic process where the structure of the electrode is taken into account. 

At present, intercalation compounds are used widely in various electrochemical devices (batteries, fuel cells, electrochromic devices, etc.). At the same time, many fundamental problems in this field do not yet have an explanation (e.g., the influence of ion solvation, the influence of defects in the host structure and/or in the host stoichiometry on the kinetic and thermodynamic properties of intercalation compounds). Optimization of the host stoichiometry of high-voltage intercalation compounds into oxide host materials is of prime importance for their practical application. Intercalation processes into organic polymer host materials are discussed in Chapter 26. 

Modem electrochemistry has vast applications. Electrochemical processes form the basis of large-scale chemical and metaUnrgical production of a number of materials. Electrochemical phenomena are responsible for metallic corrosion, which causes untold losses in the economy. Modem electrochemical power sources (primary and secondary batteries) are used in many helds of engineering, and their production figures are measured in billions of units. Other electrochemical processes and devices are also used widely. 

Walker, J. L. Single Cell Measurement with Ion-Selective Electrodes, in Medical and Biological Applications of Electrochemical Devices (Koryta, J., ed.) New York, Wiley, 1980, p. 109... 

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