A Method for Measuring Ohmic Resistance of Solution Layers at Gas-Evolving Electrodes

A method for measuring ohmic resistance of solution layers at gas-evolving electrodes was developed and tested. The method was applied to hydrogen and oxygen-evolving electrodes, and the resistance of their adjacent solution layers (for a 9 mm electrode separator gap) causes a negligible IR drop. For 3 mm gaps at a current density of 300 mA/cm 2, the IR drop of the solution layer increases to 25 mV. Contact resistances at the various electrode connections are shown to have a measurable contribution which increases with electrolysis time. Electrolytic gas evolution represents a significant and complicated problem in many electrochemical processes. During alkaline water electrolysis, energy losses take place owing to the presence of gas bubbles in the electro-lytic cell. The gas bubble contributions to an increase in potential include the following factors: (i) At the electrode surface the bubbles are dlosely packed in a thin layer form-ing a "bubble curtain. " The crowded bubbles effectively screen the electrode, raise the effective current density