The rate of gas evolution of electrodes—I. An estimate of the efficiency of gas evolution from the supersaturation of electrolyte adjacent to a gas-evolving electrode

The rate of gas evolution immediately at the electrode has a great effect on heat and mass transfer (of any substance) at gas-evolving electrodes. The question of how much of the gas generated in dissolved form is transformed into the gaseous phase of bubbles adhering to the electrode is studied on the basis of calculations of mass transfer of dissolved gas. Contrary to the established view of the matter it is found that only a fraction of the dissolved gas is transformed into bubbles at the electrode. This fraction, expressed as the efficiency of gas evolution, increases as the current density increases but is far smaller than unity in usual industrial current density values and remains different from unity in the whole range of nucleate gas evolution.