ABSTRACT
The evolution of hydrogen and oxygen are well-known phenomena during electrolysis of dilute aqueous solutions of acids and bases between inert metal electrodes. In considering electron-exchange reactions at electrodes, the layer of solution very close to the electrode surface comes under scrutiny. When conditions exist or are imposed such that the electronic levels in the electrode material and an electroactive solute material are compatible, electron transfer may take place. The cell overvoltage observed when using bright platinum electrodes is thus of the order of 0.5 V. An experimental decomposition voltage has no theoretical significance of its own, since a moment's consideration will show that it consists of two individual electrode potentials and the IR drop between them. The most common form of resistance overvoltage arises from the passage of electric through an electrolyte solution surrounding the electrode. The Luggin capillary, brought as close to the electrode surfaces as possible, largely removes the IR contribution to the measured overpotential.
