Programmed current chronopotentiometry

Chronopotentiometry is a transient constant-current technique in which the potential of the electrode is followed, as a function of time, in a quiet solution (Figure 6). Double-step applications [30], as well as programmed current experiments [31] have been described. 

In general, chronopotentiometry consists of the application of a programmed current function to an electrode, the potential of which is measured as a function of time [13]. Thus the current program may be any function that is electronically feasible. Examples of potentially useful current functions (in addition to those described in preceding sections) are ramp current chronopotentiometry for the elucidation of adsorption mechanisms, and square-root-of-time current chronopotentiometry for which concentration is directly proportional to the transition time ... 

Galvanodynamic measurements — also referred to as programmed current - chronopotentiometry [i], are the controlled current analogues of potential sweep... 

Mueller, Th.R., C. L. Olson and R.N. Adams Voltammetry at Boron Carbide and Carbon Paste Electrodes. Adv. in Polarography I, 198, ed. J. S. Longmuir. Oxford-London-NewYork-Paris Pergamon Press I960. 247- Murray, R.W., and Ch. N. Reilley Chronopotentiometry with Current Programmed as a Function of Time. I. Constant Power Functions of Time. J. Electranal. Chem. 3, 3 (1962). 

Since dEjdt is a function of time, and if also vary with time, even when i is constant. This situation can be treated as a case of programmed current chronopotentiometry if an explicit form of dEldt or drjidt is known. 

Show that if one uses programmed current chronopotentiometry with i(t) = then the stepwise reduction of a substance with n = U2 gives = T2. 

This last general equation is implemented in the function COFUNC, described in Appendix C. The formula is applied in the seven-point form in the example program CHR0N0EX described in Appendix C, simulating chronopotentiometry. It must be applied before every new iteration, in order for the Co value to be in line with the other C values. In this program, the current is constant and it is the value of Co which is displayed and this should go to zero at T = 1 (Sect. 2.4.2). A more appropriate display might be the electrode potential, which is always the measured quantity, but this will be dealt with together with the more detailed discussion of boundary conditions in Chap. 6. 

Figure 29. Current-reversal chronopotentiometry current-time program and potential-time curve.

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