Influence of the electrolyte film thickness and NaCl concentration on the oxygen reduction current on platinum

Measurements of oxygen reduction current are performed on a platinum electrode submerged under NaCl electrolyte films of different thickness. The chloride concentration is kept constant or increases due to evaporation. Measurements are supported by the numerical Multi-Ion Transport and Reaction Model (MITReM). In case of constant salt concentration, oxygen reduction current is proportional to the reciprocal of the electrolyte film thicknesses down to 50-75 μm; for lower thicknesses deviation from the Fick's law takes place. For evaporating films, oxygen current is the result of two counteracting phenomena: reducing film thickness and increasing salt concentration leading to decrease of oxygen solubility.