chronopotentiometry

Chronopotentiometry is an electrochemical method in which a constant current is imposed on an electrochemical cell and the resulting electrode potential is recorded as a function of time. The technique relies on mass transport of electroactive species to or from the electrode mainly by diffusion. When a fixed current is applied, the surface concentration of the redox species changes with time, causing the electrode potential to drift. For a reversible or quasi-reversible couple, the potential starts near the formal potential and moves monotonically as the reactant is depleted (or product accumulates). Eventually a diffusion-limited regime is reached in which the current is still fixed by the applied current and the potential adjusts to drive the reaction; a diffusion region and often a linear ramp of potential can be observed until the limiting state is established.

The resulting E-t curve can be analyzed to obtain diffusion coefficients and concentrations, and to study electron-transfer kinetics and reversibility. The technique is commonly implemented with a three-electrode cell (working, reference, auxiliary) and a potentiostat or current source capable of controlled current output. Data interpretation frequently uses Sand’s equation to relate the transition time to i, D, and initial concentration for diffusion-controlled processes, though the exact form depends on geometry and reaction order.

Chronopotentiometry is particularly useful for quantitative analysis of inorganic and organic redox systems, electrode kinetics studies, and evaluation of electrode surfaces or thin films. Limitations include susceptibility to iR drop, double-layer charging, and capacitive currents, which can complicate interpretation for fast or highly reversible systems. In practice, chronopotentiometry is often paired with complementary methods such as cyclic voltammetry to obtain a fuller kinetic and mechanistic picture.