A current produced due to the redox reactions of the analyte at the working and auxiliary electrodes is called a faradaic current. The reaction can be divided into two types. The current generated due to the reduction of the analyte is called cathodic current, and it carries a positive charge. In contrast, the current produced by analyte oxidation is known as an anodic current, and it has a negative charge. The applied potential at the working electrode determines the faradaic current flow, and the magnitude of faradic current depends on the rate of the resulting oxidation or reduction reaction at the electrode surface.
In addition, various mass transport reaction processes like diffusion, migration, and convection affect the faradaic current by facilitating the movement of ions or molecules from the electrode surface to the bulk solution and vice versa. During diffusion, ions or molecules are transported from a region of high concentration to a region of low concentration, and the effect of diffusion on the mass transport rate is time-dependent. It is known as convection if a mechanical means is used to carry reactants toward the electrode and remove products from the electrode. It is called migration if the charged analyte particles are attracted or repelled by electrodes.
The rate of mass transport also influences the current. If the rate of electron transport kinetics is fast, the redox reaction is at equilibrium, and the system is electrochemically reversible. In contrast, when the rate of electron transport kinetics is slow, the system is treated as electrochemically irreversible. Finally, the Nonfaradaic charging current produced by the changes in electrode potential must be accounted for before measuring the Faradaic component.
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