Inner electric potentials Galvani

The macroscopic electric potential on the right side of Eq. s2.7 is known as an inner electric potential, and the potential difference on the right side of Eq. s2.9 is an example of a Galvani potential difference39... 

The effects of the crystallographic face and the difference between metals are evidence of the incorrectness of the classical representations of the interface with all the potential decay within the solution (Fig. 3.13a). In fact a discontinuity is physically improbable and experimental evidence mentioned above confirms that it is incorrect, the schematic representation of Fig. 3.136 being more correct. This corresponds to the chemical models (Section 3.3) and reflects the fact that the electrons from the solid penetrate a tiny distance into the solution (due to wave properties of the electron). In this treatment the Galvani (or inner electric) potential, (p, (associated with EF) and the Volta (or outer electric) potential, ip, that is the potential outside the electrode s electronic distribution (approximately at the IHP, 10 5cm from the surface) are distinguished from each other. The difference between these potentials is the surface potential x (see Fig. 3.14 and Section 4.6). 

Galvani potential difference — A

electrostatic component of the work term corresponding to the transfer of charge across the - interface between the phases a and f whose - inner electric potentials are (/>" and R, respectively, i.e., the Galvani potential difference is the difference of inner electric potentials of the contacting phases. The electrical potential drop can be measured only between the points which find themselves in the phases of one and the same chem-ical composition [i,ii]. Indeed, in this case p ( = p and... 

Whereas a direct measurement of the inner electric potential of a single phase is impossible, the difference, i.e., the Galvani potential difference of two phases A

common interface, is accessible when a proper reference electrode is used, i.e., a metal/electfolyte system, which should guarantee that the chemical potential of the species i is the same in both electrolytes, i.e., the two electrolytes contacting the metal phases I and 11. In addition, the absence of a junction potential between the two electrolytes is required. Under such circumstances it is possible to measure a potential difference, AE, that is related to A(p however, it always includes the A4> of the reference electrode. The latter is set to zero for the Standard Hydrogen Electrode (see below). In fact, the standard chemical potential of the formation of solvated protons is zero by convention. 

The electric potential (p in the interior of a phase is called the inner electric potential, or Galvani potential. It is defined as the work needed to reversibly move an infinitesimal test charge into the phase from a position infinitely far from other charges, divided hy the value of the test charge. The electrical potential energy of a charge in the phase is the product of 4> and the charge. 

We are concerned with the electric potential within a phase— the inner electric potential, or Galvani potential. We can measure the difference between the values of this electric potential in the two terminals of a galvanic cell, provided the terminals have the same chemical composition. If the terminals were of different metals, at least one of them would have an unknown metal-metal contact potential in its connection to the external measuring circuit. 

The Galvani potential difference (GPD) is defined as the difference of the inner electric potentials within the Helmholtz part of the double layer. " However, in solutions with ionic strengths above approximately 0.1 mol/(im, the difference of the inner electric potentials between the outer plane of the Helmholtz layer and the bulk of the solution is close to zero. In such cases, the GPD may be approximated by the difference of the inner electric potentials of the electrode material and the solution, with the inner electric potential of the solution as the relative zero point in the evaluation of... 

The presence of an electrical potential drop, i.e., interfacial potential, across the boundary between two dissimilar phases, as well as at their surfaces exposed to a neutral gas phase, is the most characteristic feature of every interface and surface electrified due to the ion separation and dipole orientation. This charge separation is usually described as the formation of the ionic and dipolar double layers. The main interfacial potential is the Galvani potential (termed also by Trasatti the operative potential), which is the difference of inner potentials (p and of both phases. It is a function only of the chemical... 

Fig. 5.38. A. (a) An electrical double layer and (b) an electrical triple layer. B. Potential distribution at the interface. OHP = Outer Helmholtz Plane, IHP = Inner HP, <1> = Galvani potential.

The electrochemical interface can also be viewed using a different framework [11, 13-18]. The electrical potential of the interior of an electrode with respect to a point at infinity in a charge-free vacuum is referred to as inner potential. An energy of etp is required to transport an electron from infinity to the interior of the electrode. This potential can be considered to be composed of the sum two other potentials,

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An electrochemical potential, A. can be expressed in terms of a chemical potential, p, and the inner (Galvani) electrical potential rp. 

The analysis of elementary steps that involve charge transfer, whether of electrons or of ions, require a detailed discussion of the inner (Galvani) electrical potential, (p. 

The electrostatic potential within a phase, that is, l/e times the electrical work of bringing unit charge from vacuum at infinity into the phase, is called the Galvani, or inner, potential Similarly, the electrostatic potential difference... 

The description of the ion transfer process is closely related to the structure of the electrical double layer at the ITIES [50]. The most widely used approach is the combination of the BV equation and the modified Verwey-Niessen (MVN) model. In the MVN model, the electrical double layer at the ITIES is composed of two diffuse layers and one ion-free or inner layer (Fig. 8). The positions delimiting the inner layer are denoted by X2 and X2, and represent the positions of closest approach of the transferring ion to the ITIES from the organic and aqueous side, respectively. The total Galvani potential drop across the interfacial region, AgCp = cj) — [Pg.545]

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