Chronopotentiometry

Electroanalytical techniques mainly involve three quantities: current $i$ , the potential $E$ and time $t$ , or a function derived from it, such as electrochemical impedance. Etymologically, chronopotentiometry is a measurement of potential. $E$ depending on the weather $t$ However, according to the recommendations of the IUPAC (International Union of Pure and Applied Chemistry), it is limited to techniques for which:

• on the one hand, the excitation signal $i$ is constant or variable over time $t$ (at least during the first pulse in the case of pulse trains) and not zero (which implies at least one electrochemical reaction);

• and on the other hand, the transfer of matter is ensured by diffusion alone.

This excludes potentiometric techniques and potentiometric titrations with zero current and constant current in the case of forced diffusion (stirring of the solution).

Excitation signals (current as a function of time) can be constant, progressive, stepped, cyclic, alternating, or pulse train signals. In the case of fast periodic signals, the chronopotentiometry technique is similar to that of impedance spectroscopy with imposed alternating current.

Based on the processing of chronopotentiograms, numerous applications are discussed in this article:

• determination of the diffusion coefficient of a redox analyte;

• determining the concentration of an adsorbed reagent;

• monitoring the kinetics of oxide or sulfide film formation;

• monitoring the kinetics of alloy formation;

• the determination of the equilibrium constants of the complexes formed, as well as the constants of the chemical reactions that precede or follow an electrochemical reaction.