Potential step and pulse techniques

The potential step provides the theoretical background for any potentiostatic regulation experiment and a basic understanding is necessary for the mathematical solution of any controlled potential, nonsteady-state voltammetric response, such as LSV, pulse or a.c. experiments. At a stationary electrode, the current response to a potential step is described by the Cottrell equation [eqn. (83)] but at hydro-dynamic electrodes, it needs to be modified to take account of forced convection. 

At the RDE, various approximate analytical treatments have been presented by dropping the highest order convective term [237], neglecting convection completely [238], and by assuming a linear concentration profile within a time-dependent mass transfer boundary layer [239]. The last of these gives 

At a double electrode, such as the rotating ring—disc electrode, a potential step at the disc will produce a ring current transient, the form of which is affected only by Faradaic current components at the disc. This fact can be very useful in separating Faradaic and non-Faradaic processes. 

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