Galvanostatic transient technique

Galvanostatic Transient Technique. In the galvanostatic method a constant-current pulse is applied to the cell at equilibrium state and the resulting variation of the potential with time is recorded. The total galvanostatic current ig is accounted for (1) by the double-layer charging, /ji, and (2) by the electrode reaction (charge transfer), i. ... 

The plot V = f(t), in the microseconds range, is a straight line with slope dVIdt. Thus, the double-layer capacitance Qj may be calculated by means of Eq. (4.17) using the slope (dV/dt) provided by the experimental data. One example of such calculations is presented in Problem 4.2. Galvanostatic transient technique is discussed in detail in Section 6.9. 

Galvanostatic Transient Technique, In the galvanostatic technique the current between the test electrode and the auxiliary (counter-) electrode is held constant with a current source (galvanostat), and the potential between the test electrode and the reference electrode is determined as a function of time. The potential is the dependent variable, which is recorded with suitable recording systems, such as recorders or oscilloscopes (Fig. 6.17). 

For example, if Qi = 50 tF/cm and R = 2 fi, t = 4.6 X 10 " s (0.46 ms). Thus, in the galvanostatic transient technique, the duration of the input current density pulse is on the order of milliseconds. From a series of measurements of for a set of i values, one can construct the current-potential relationship for an electrochemical process. For example. Figure 6.20 shows the current-potential relationship for the electrodeposition of copper from acid CUSO4 solution. 

Galvanostatic Transient Technique Double-Layer Capacitance Measurements. The value of the fractional surface coverage 9 may be inferred by means of doublelayer capacitance data. As discussed in Section 6.9, the double-layer capacitance C may, in turn, be determined by means of a transient technique. In the galvanostatic transient technique (as in Fig. 6.18), the duration of the constant-current (density) pulse is on the order of microseconds. In the microsecond time range the only process taking place at the electrode is charging of the double layer. Flence, in this case, Eq. (6.96) reduces to... 

Galvanostatic Transient Technique. Breiter (4) measured the adsorption of formic acid (HCOOH) on platinum in the solution of perchloric acid (HC104) using... 

The study of the charge-transfer processes, free from the effects of mass transport, is possible by the use of transient techniques. In the simplest transient techniques, the interface at equilibrium is abruptly changed from an equilibrium state to a steady state characterized by a new potential difference Aconstant current, galvanostatic transient technique or (2) the constant potential, potentiostatic transient technique. The study of transient processes utilizes the three-electrode cell design (Fig. 10). 

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