Chronoamperometric

Chronoamperometry is an electrochemical technique in which the potential of a working electrode is stepped to a fixed value and the resulting current is recorded as a function of time. The method is widely used to study redox processes, diffusion, and electrode kinetics in solution.

In a typical setup, a three-electrode cell is employed: a working electrode, a reference electrode, and a counter electrode. The potential step is chosen to drive reduction or oxidation of the target species, and the transient current reflects the transport of electroactive species to the electrode surface. For diffusion-controlled processes at a planar electrode with semi-infinite diffusion, the transient current follows the Cottrell equation: i(t) = n F A C sqrt(D / (π t)), where n is the number of electrons transferred, F is Faraday’s constant, A is the electrode area, C is the bulk concentration, and D is the diffusion coefficient. Consequently, the current decays approximately as t^(-1/2) as the diffusion layer expands.

Chronoamperometry provides information on diffusion coefficients, concentrations, and, in some cases, reaction kinetics. Reversible (fast) electron transfer tends to produce diffusion-limited currents, while slower kinetics produce deviations in the early-time transient that reflect charge-transfer rates. Practical considerations include minimizing capacitive (double-layer) charging currents, accounting for convection or stirring that alters diffusion, and interpreting results within appropriate geometries (planar versus microelectrode).

Applications span analytical sensing, determination of kinetic parameters, and basic investigations of redox systems. Chronoamperometry is valued for its simplicity, time resolution, and direct link between current and mass transport.