Open AccessThe kinetics of the electro-deposition of hydrogen and oxygen
Author(s) -
F. P. Bowden
Publication year - 1929
Publication title -
proceedings of the royal society of london. series a, containing papers of a mathematical and physical character
Language(s) - English
Resource type - Journals
eISSN - 2053-9150
pISSN - 0950-1207
DOI - 10.1098/rspa.1929.0207
Subject(s) - electrolyte , electromotive force , electrode potential , electrode , nernst equation , chemistry , kinetics , reactions on surfaces , reversible hydrogen electrode , standard hydrogen electrode , thermodynamics , chemical physics , working electrode , adsorption , physics , quantum mechanics
Although the thermodynamic argument laid down by Gibbs and by Nernst has proved invaluable in specifying the conditions of equilibrium at an electrode / electrolyte interface, relatively little progress has been made in our knowledge of the kinetics of electrode reactions and the mechanism of the potential changes involved. A theoretical expression for the electromotive force of a cell from kinetic considerations has been developed by Butler. Electrode reactions resemble other surface reactions in that small amounts of foreign materials on the surface or slight changes in the structure of the surface greatly affect the velocity of the reactions. Under the conditions obtaining in an electrolytic cell, the electrode surfaces are particularly liable to contamination or to change, and it is partly this which makes an experimental study of the kinetics of these reactions difficult. It is only by the selection of a suitable surface and a rigorous exclusion of impurities and dissolved gas that reproducible results can be obtained. In addition to the state of the electrode surface there are many other varying factors which control the course of these reactions, and all these must be determined. Using the method which has been described, it is possible to make a quantitative study of the processes occurring on an electrode surface. The true area of the surface, the electrical potential across the interface, the quantity of reactant on the surface and its rate of decay can all be measured and controlled. Since these quantities are determined electrically the method is a sensitive one; the potential changes caused by the passage of sufficient electricity to deposit only a few thousandths of an atomic layer can be measured, and surface reaction velocities of the order of 10-13 gm. ions per cm.2 per second can be followed conveniently.