Chronoamperometry

Chronoamperometry is an electrochemical technique in which a potential is applied to a working electrode at time zero and the resulting current is recorded as a function of time. The method is used to study redox processes by observing transient currents after a potential step, providing information about diffusion, kinetics, and concentrations.

Typically, chronoamperometry uses a three-electrode cell with a working electrode, a reference electrode, and a counter electrode. The potential is stepped from a baseline value to a value that drives the desired oxidation or reduction. The recorded current initially contains a capacitive (double-layer) component, which decays rapidly, after which the faradaic current due to species diffusion to the electrode dominates. The resulting chronoamperogram can be analyzed to extract transport and kinetic parameters.

In diffusion-controlled cases, the current decay follows a Cottrell-type behavior, described by i(t) = n F A C / sqrt(pi D t), where n is the number of electrons transferred, F is Faraday’s constant, A is electrode area, C is bulk concentration, D is the diffusion coefficient, and t is time. In systems with slower kinetics or reversible couples, electrode kinetics modify the transient shape and the surface concentration dynamics, enabling estimation of rate constants and transfer coefficients through fitting to appropriate models.

Instrumentation and setup for chronoamperometry typically involve a stable potentiostat, a glassy carbon, platinum, or gold working electrode, a reference electrode such as Ag/AgCl, a counter electrode, and a supporting electrolyte. Microelectrodes can reduce i and enhance steady-state control. Data analysis may use analytical expressions for simple regimes or numerical simulations for complex kinetics.

Applications include determination of diffusion coefficients, kinetic parameters of electron transfer, sensor development, and characterization of battery and corrosion processes.