Methods of this type involve stepping the electrode potential from a value where little or no faradaic current is observed to one sufficient to oxidize or reduce an electroactive species in the vicinity of the electrode. Large amplitude step methods described in this section involve a change in potential capable of instantly converting essentially all of the electroactive material at the electrode surface to its redox partner. In contrast, small amplitude potential methods, described elsewhere in this module, involve small changes in surface redox concentrations as a function of changing potential, with the concentrations of the members of the redox pair described by the Nernst Equation.
We will include here two of the most frequently used large amplitude potential step (potentiometnc) methods, chronoamperometry and chronocoulometry.
Chronoamperometry involves the measurement of current passing in the electrochemical cell at a fixed potential as a function of time (i vs. t).
Chronocoulometry is the measure of total charge (the integrated i-t response, Q), also as a function of time.