EFFECT OF ELECTROLYTIC GAS EVOLUTION ON MASS-TRANSFER AT ELECTRODES

A theoretical description of a hydrodynamic model for mass transfer at gas evolving electrodes where no coalescence of gas bubbles occurs is given. To elucidate the mechanism of mass transfer, the thickness of the Nernst diffusion layer, δ, has been determined as a function of the volumetric rate of the gas evolution, v, for both a gas evolving disc electrode and non-gas evolving ring electrodes placed concentrically around the gas evolving disc electrode. These experiments are performed for both hydrogen and oxygen evolution in alkaline solution. It is found that for the hydrogen evolving electrode, where no coalescence occurs, the slope of the log δ/log v curve agrees with the theoretical slope. For the oxygen evolving electrode, where coalescence occurs frequently, the experimental and the theoretical slope differ markedly. © 1979.