nonfaradaic

NonFaradaic refers to processes in electrochemical systems that do not involve the transfer of electrons between the electrode and species in the electrolyte. In contrast, Faradaic processes involve redox reactions at the electrode interface and produce current through electron transfer. NonFaradaic currents arise mainly from charging and discharging of the electrical double layer, dielectric polarization of the electrolyte near the electrode, and adsorption-desorption steps that do not involve electron transfer. They may also stem from stray capacitances in the measurement setup.

A typical manifestation is the double-layer charging current, which is approximately proportional to the rate of change of the electrode potential (I ≈ C_dl dV/dt), where C_dl is the double-layer capacitance. Because these currents do not reflect chemical changes, they contribute background signals in electrochemical measurements such as cyclic voltammetry and chronoamperometry. They can be particularly prominent at high scan rates or with highly capacitive electrodes, potentially masking or distorting Faradaic responses.

In impedance spectroscopy, nonFaradaic contributions are treated as part of the passive interface behavior, often modeled as a capacitor (the double-layer capacitance) in parallel or in series with solution resistance. While nonFaradaic processes are typically non-destructive and reversible, they can complicate data interpretation when distinguishing them from Faradaic processes.

NonFaradaic currents can also be exploited in capacitive sensing and surface studies, where changes in double-layer properties or surface adsorption alter the measured capacitance without invoking redox chemistry. Distinguishing nonFaradaic from Faradaic signals relies on potential-dependent features, control experiments, and appropriate impedance analysis.