In cyclic voltammetry, what does the peak current indicate?

In cyclic voltammetry, the peak current is directly related to the rate of electron transfer between the electrode and the redox species in solution. During the potential sweep, as the voltage is changed, the electrochemical reaction proceeds, leading to the generation of a current that corresponds to the number of electrons transferred per unit time at the electrode surface. The height of the peak current reflects how quickly the electron transfer occurs under the conditions set by the voltammetric experiment.

At the peak, the concentration of the oxidized or reduced species at the electrode surface has achieved a state where it is optimal for the electron transfer, indicating that the kinetic processes governing the reaction are at their most efficient. This relationship between peak current and electron transfer rate is further supported by the Randles-Sevcik equation, which describes how peak current can be influenced by factors like scan rate and concentration, tying it directly to the kinetics of the redox process under study.

The other options relate to aspects of the cyclic voltammetry experiment but do not capture the fundamental meaning behind the peak current as accurately as the correlation to the rate of electron transfer.