Basic Concepts of Electrochemistry

In an electrochemical converter an overall redox reaction is divided into two semi-reactions which take place on physically separate electrodes, anode, and cathode, for oxidation and reduction semi-reactions, respectively. For a generic redox reaction, involving the species A and B in equilibrium, the overall reaction and two semi-reactions can be schematized as follows  

The electrons transferred during the redox reaction move through an external circuit, exiting from the anode after oxidation, and entering into the cathode for reduction. The two semi-reactions can occur because the two separate spaces are inter-connected by a conductive hquid or solid phase (electrolyte) able to transfer ionic species, thus permitting the closing of the electric circuit. Then the electrolyte has to be ionically conductive, whereas the electrodes have to be electrically conductive and, in the case of gaseous reactants, sufficiently porous to allow the transfer of reactants and products to and from the reaction sites (see Sect. 3.2). 

It is possible to build a scale of potentials for different electrochemical pairs in standard conditions (298 K, 1 atm for gases or unit concentration for solutions) assuming the pair hydrogen/ion-hydrogen as an arbitrary reference semi-reaction, and assigning to it a potential of zero volt  

The potential in standard conditions ( °) of other electrochemical pairs can be obtained with respect to Eq. 3.4, permitting the compilation of a list of semireaction potentials (electrochemical series ). In this list, all the semi-reactions are written in such a way to evaluate the tendency of the oxidized forms to accept electrons and become reduced forms (positive potentials correspond to spontaneous reductions) [2]. These potentials can be correlated to thermodynamic quantities if the electrochemical system behaves in a reversible way from a thermodynamic point of view, i.e., when the electrochemical system is connected against an external cell with the same potential, no chemical reaction occurs, while any inhnitesimal variation of the external potential either to produce or to absorb current is exactly inverted when the opposite variation is applied (reversible or equilibrium potentials, Eeq)- When the equilibrium of the semi-reaction considered is established rapidly, its potential against the reference can be experimentally determined. 

Any redox reaction is accompanied by a change of free energy (AG) at a given temperature and pressure. However, when the reaction is carried out in an electrochemical way, the transport of electric charges due to a total potential difference is associated with an electric work, which is given by  

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A more detailed description of different types of batteries and other electric energy storage systems for electric vehicles can be found in Sect. 5.3, while a description of the main characteristics and properties of fuel cells for automotive application is given here, starting from some basic concepts of electrochemistry and thermodynamic, and focusing the attention on the operative parameters to be regulated to obtain the best performance in the specific application. 

Hydrogen production, onboard storage and distribution technologies are reviewed in Chap. 2, while basic concepts of electrochemistry are recalled in Chap. 3, with an assessment of the state of development of fuel cells for automotive applications, in terms of performance and durability. 

According to the basic concepts of electrochemistry (see also Chap. 1 in Vol. 1), the electrode potential E measured with respect to the constant reference electrode can he expressed as... 

Abstract Corrosion is basically the oxidation of metals, where electrons are transferred between oxidant and reductant. Therefore, corrosion is generally composed of redox reactions and should be analyzed from the viewpoint of electrochemistry. In this chapter, we describe the basic concept of electrochemistry and how various corrosion aspects can be explained by this discipline. We focus particularly on the equilibrium side because it could suggest possibilities that might be useful for corrosion prediction. The close relationship between redox reactions and corrosion are explained and stressed qualitatively and quantitatively. 

Basic Concepts of Electrochemistry used in Electrical Engineering... 

The aim of this chapter is to lay down some basic concepts of electrochemistry which are necessary in order to understand the behavior of the electrochemical components described in this book. For a detailed presentation, the reader eould be helped by referring to specialized books such as piA 96 LEF 09],... 

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