Electrolysis Regimes Research Articles

Product distribution in preparative scale electrolysis: Part IV. EC reaction schemes followed by competition between first-order chemical reaction and further electron transfer. Electrocatalytic systems

The dependence of product distribution on the intrinsic and operational parameters of the system is established for electrochemically catalyzed processes, in which catalysis is in competition with electrode or solution electron transfer leading to an overall two-electron reduction or oxidation of the starting material. The main interest of such relationships is the prediction of the yield and the selection of the best experimental conditions for optimizing the production of the desired product. The extent of the competition between catalysis and electron transfer is also reflected by the apparent number of electrons, which varies between zero and two. Two different potentiostatic electrolysis regimes are considered, in which the substrate is either kept in constant concentration or exhaustively electrolyzed. Two limiting situations are of particular interest, corresponding to an easy characterization of the system. They involve the predominance of one of the modes of electron transfer, either heterogeneous or homogeneous. The operational parameters have no influence on the course of the competition in the first case, while electrocatalysis is favored by low concentrations and large diffusion layer thickness in the second. The electrochemically catalyzed substitution of 2-chloroquinoline by benzenethioalate in liquid ammonia is discussed as an example of the application of the theoretical relationships.

Theoretical analysis of catalytic current—potential curves Part I. First-order regeneration mechanisms at different electrolysis regimes

Theoretical analysis of catalytic current—potential curves Part I. First-order regeneration mechanisms at different electrolysis regimes

Theoretical analysis of catalytic current-potential curves: Part I. First-order regeneration mechanisms at different electrolysis regimes

The article describes a general treatment of the catalytic reaction mechanism at an electrode expanding in accord with any power law, the stationary electrode and the dropping mercury electrode being special cases. Reversible, irreversible and quasi-reversible electrode reactions are embraced by the treatment. A general expression for the current-voltage characteristic was derived, which was applied to different electrolysis regimes. The cases when the regeneration reaction will influence the catalytic wave characteristics are also discussed.

Hydrodynamic Transition in Electrolysis

The gas removal process during electrolysis is studied with the aim of identifying hydrodynamic transitions, analogous to those which occur in boiling. The local peak in the electrolysis gas flux is observed during electrolysis from a horizontal cylindrical cathode. This transition point is shown to correspond with Moissis and Berenson’s “first transition” in nucleate pool boiling. A prediction of the transition, applicable to either boiling or electrolysis, is developed for the cylindrical heater (or cathode) arrangement. It is compared with 12 experimental data for boiling and electrolysis, and its limitations are discussed. Finally, some attributes of the regime of film electrolysis are identified and discussed.