Cathodic Oxygen Reduction in the Sealed Lead‐Acid Cell

Abstract

The steady‐state current observed during the cathodic reduction of O2 at a partially exposed, electrochemically active electrode does not always represent its true recombination capability. This is usually the case when ohmic dissipation of the applied potential, resulting from inclusion of a highly resistive, thin electrolyte film in the current path, limits the passage of an externally supplied current to only a small distance above the free electrolyte level. Chemical reduction of O2 can then occur over the area of substrate in contact with the thin film which is above the level of current penetration. O2 reduction was studied at such electrodes in order to delineate the conditions under which both current penetration and O2 access could be maximized, allowing a closer approximation of the true recombination capabilities of maintenance‐free storage batteries. The magnitude of the difference between the rate of O2 reduction and the steady‐state current was determined by monitoring the current obtained after reimmersing the exposed electrode. The effect on this difference of variables, such as electrolyte concentration, O2 partial pressure, applied potential, separator position, and degree of electrode exposure, are presented for the Pb‐acid system.