Volta potential difference

If two metals with different work functions are placed m contact there will be a flow of electrons from the metal with the lower work function to that with the higher work fimction. This will continue until the electrochemical potentials of the electrons in the two phases are equal. This change gives rise to a measurable potential difference between the two metals, temied the contact potential or Volta potential difference. Clearly... 

Time interval, characteristic T, T Volta potential difference ... 

Figure 23. Plot of the experimental contact (Volta) potential difference atmetal/solventinterfaces ( r=0)vs. the values calculated by Jaworski898 as a function of solvent donor (DN) and acceptor (AN) numbers using the equation = 0.007 AN - 0.011 DN - 0.485. (Reproduced from...

Instead of cpy, lUPAC recommends A / = — /i and uses die term Volta potential difference. 

In contrast to differences in the inner potentials (the Galvani potential difference), the difference in the outer potentials A pip (the Volta potential difference or the contact potential) and the real potential or, can be measured. The real potential <, is defined as... 

Fig. 3.5 The significance of the contact potential (Volta potential difference) Apijj between two metals in contact. (According to S. Trasatti and R. Parsons)... 

Some information about the metal-solvent interaction can be obtained from measurements of the contact (Volta) potential difference at the metal/solvent interface... 

Figure 3. Comparison of the Volta potential differences at the Hg/solvent interface vs. (a) donor number and (b) donor and acceptor numbers. Jt=0.007 AN-0.011DN-0.485 ...

The inner potential difference between two contacting phases is cafied in electrochemistry the Galvani potential difference, and the outer potential difference is called the Volta potential difference. The outer potential difference corresponds to what is called the contact potential between the two phases. We call, in this test, the inner potential difference across an interface the interfacial potential. 

For correct function of the ISFET, a sufficiently large gate voltage, Vq, must be applied between the leads to the reference electrode and to the substrate, so that a sufficiently large potential difference is formed between the surface and the interior of the substrate for formation of the n-type conductive channel at the insulator/substrate interface. This channel conductively connects drain 1 and source 2, which are connected with the substrate by a p-n transition. On application of voltage Vj between the drain and the source, drain current /p begins to pass. Under certain conditions the drain current is a linear function of the difference between Vq and the Volta potential difference between the substrate and the membrane. 

Vii ial equation of state in two dimensions, 931 Virial isotherm, 936 Visible radiation, 797 Volcanoes, in electrocatalysis, 1284 Volmcr, Max, 1048,1474 Volmer. Weber, electrodeposition. 1303. 1306 Volta, 1423, 1455 Volta potential difference, 822 Voltammetry. 1432 1434 cyclic, 1422 1423 diffusion control reactions, 1426 electron transfer reaction, 1424... 

At this stage, let the two conceptually separated pails of the double layer be brought together again. The interface has been reassembled. One can now refer to the outer potential difference, sometimes called the Volta potential difference, between the metal and solution. This outer potential difference is written... 

The Volta potential difference is a quantity that can be measured experimentally (see Appendix 6.1). Further, if one chooses a plausible model of the arrangement of charges at the interface, the Volta potential difference can be calculated by simple electrostatic reasoning [see Eq. (6.118)]. It is for these reasons that the outer potential is an important aspect of the study of the electrified interface. 

APPENDIX 6.1. MEASUREMENT OF THE ELECTRODE-SOLUTION VOLTA POTENTIAL DIFFERENCE... 

The value of the Volta potential difference between a metal a and a solution can be obtained by performing two measurements, in one of which the electrode a is in contact with the solution (Fig. A6.1), whereas, in the second, it is separated from the latter by a space filled with ionized unreactive gas at a low pressure (Fig. A6.2). Electrode a and another electrode of a metal y, reversible to ions Mz+ in solution, are connected to a potentiometer P by wires P and P made of the same metal. 

Fig. 1. The definition of the Volta-potential difference in the system electrode-electrolyte solution.

We can use the relations derived in (30) and (31) unchanged, if Sif/ is to represent the Volta potential difference between a free surface and a similar one occupied by a concentration of chemisorbed gas equal to... 

The main effect of crystal orientation is caused by different barrier heights on different crystal faces. It is well known that Volta-potential differences are dependent on crystal orientation because the surface dipole differs for different faces. In the case of a semiconductor electrode this means that the flat band potential which can be determined experimentally depends... 

In the second step the charge arrives at the internal phase passing through the interface. The associated potential is known as the surface potential jump (also called surface potential, surface electrical potential, etc.). It is determined by dipoles aligned at the interface and by surface charges. It is not identical with the Volta potential difference (also sometimes called the surface potential) that has so far been used for the description of the electrical double layer. For the treatment of the electrical double layer, dipoles did not play a role. In particular in water, however, the aligned water molecules contribute substantially to the surface potential jump x- The Galvani potential, Volta potential, and surface potential jump are related by... 

The Volta potentials of individual phases and Volta potential differences Af between two phases can be measured. In contrast, the Galvani potential and accordingly the surface potential of a single phase cannot be measured. Explanation If we bring a test charge (an ion or an... 

Concerning the potential differences, that corresponding to the outer potentials between two phases a and /> is known as the Volta potential difference defined as... 

The electrostatic potential of a phase is defined as the potential of the space just outside it, for a phase a let this be Fa. The Volta potential difference between two phases is the difference in electrostatic potential between two points just outside the phases. The electrostatic potentials, and therefore the Volta potential, are determined by the amount of charge on the phase and its electrostatic capacity. 

The Volta potential difference between two phases a and j3 is Fa— F it is sometimes called the external contact potential, more commonly simply the contact potential. 

---