Controlled Current Techniques

trode configuration, in which a current is applied between the auxiliary and working electrodes and the potential of the working electrode (measured with respect to the reference electrode) is monitored. The basis of controlled current experiments is that a redox (electron transfer) reaction must occur at the surface of the working electrode in order to support the applied current. For example, if ferricyanide is present in the solution, then a reducing current will lead to the reduction of ferricyanide to ferrocyanide at the working electrode (note that a balancing oxidation must also occur at the auxiliary electrode). Common applications of the galvanostat include constant current stripping potentiometry and constant current electrolysis (including applications where a constant rate of electrolysis is important, such as electrodeposition and battery studies). One advantage of all constant current techniques is that the ohmic drop due to solution resistance is also constant, as it is equal to the product of the current and the solution resistance. The ohmic distortion can therefore be simply corrected by a constant potential offset. In contrast, in potentiostatic experiments (e.g., cyclic voltammetry), the current, and hence the ohmic drop, varies with potential, and correction is more complicated.