Exchange current density table

Physically, the lack of methanol in the second half of the channel forces the anodic reaction to run with carbon as a fuel. Owing to the small exchange current density (Table 5.11), the carbon corrosion reaction requires quite a significant overpotential... 

Table 21.13 Exchange current densities for the hydrogen evolution reaction...

Table 21.14 Exchange current densities and transfer coefficients a for evolution of gases at 20-25°C at different anodes...

Table 21.16 Exchange current densities for several noble metals and a platinum-rhodium alloy in the reduction of oxygen from perchloric acid solution ...

Table 5.1. Exchange current densities and rate constants in aqueous systems.

Table 5.3. Exchange current densities in molten salt electrolyte systems.

Extrapolation of the linear portion of the curves to the standard oxygen reduction potential gives the corresponding exchange current density, a measure of the equilibrium rate of the reaction [35]. The results are given in Table I. Within... 

As in Eq. (3.22), F is the Faraday constant, n is the number of electrons taking part in the reaction, but iq is a new quantity called the exchange current density. These rates have units of mol/cm s, so the exchange current density has units of A/cm. Typical values of io for some common oxidation and reduction reactions of various metals are shown in Table 3.4. Like reversible potentials, exchange current densities are influenced by temperature, surface roughness, and such factors as the ratio of oxidized and reduced species present in the system. Therefore, they must be determined experimentally. 

Given that the rates of oxidation and reduction of the half-reactions are controlled by activation polarization only, that = 4-0.07 and = —0.08, and that the exchange current densities for both the oxidation of Fe and reduction of hydrogen in acidic solution are identical, use the data in Tables 3.3 and 3.4 to determine the following quantities. Recall that the potential for each half-cell is the sum of the equilibrium potential and the corresponding overpotential, in this case, r]a-... 

Since different surfaces will catalyze a given reaction to different degrees, it follows that io values are specific for a particular electrode surface. The exchange current densities for the evolution of hydrogen from 1 mol L-1 HC1, for example, range over some 11 powers of 10 (Table 15.1). 

Calculate the exchange current density and the symmetry factor (P) ofacathodic reaction A+ + e —> A from Table E.6. 

The overpotentia] measured at a current density of 10-5 A/cm2 was +0.236 V. The decay of the overpotential with the cut off of the current was observed as listed Table P.l. Calculate the double-layer capacitance, the exchange current density, and the transfer coefficient for the electrochemical reaction. (Kim)... 

Table 6.2 Estimates of Apparent Standard Exchange Current Densities /q Exchange Current Ratios i o, i/o,K and Selectivity Coefficients Obtained by Different Methods ...

TABLE II Approximate Values of Exchange-Current Densities... 

Table 5.5 indicates die range of exchange current densities that have been observed for the hydrogen evolution reaction on various metals. Note that the... 

TABLE 5.5 The Exchange Current Density y0 for the Hydrogen Evolution Reaction in 1 M H2S04... 

Now, to go to the experimental situation, what happens as we insert a metal electrode into an electrolyte solution without connecting it to an external electron source As we have discussed before (p. 22), an El is built up and hence a certain potential is established across the interface region. At this potential, charge transfer between electrode and electroactive species takes place, but, since no net current flows, the rates of electronation and de-electronation are identical. The system has reached the equilibrium potential at which the current density z for electronation is equal to the current density of de-electronation i. This current density is designated i0, the equilibrium exchange current density (cf. Table 6), given by the expression ... 

Table 10 Exchange Current Densities and Coverage (0) for Halogen Electrodes in Molten Salts...

Table 2K The effect of solution resistance on the minimum pulse duration and the maximum value of the exchange current density measurable in a coulostatic experiment.

Table I and Table II show the respective values of the exchange current densities and open circuit potentials for pure iron, 304 S.S. (12l) 316 S.S., and 1080 C.S., near the critical point of water. The values at ambient conditions are also listed. Reproducibility of the exchange current density was found to be +/>...

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