Electrochemical Oxidation of Hydrogen on Partially Immersed Platinum Electrodes: I . Experiments and Interpretation

Abstract

The mechanism of the ionization of molecular hydrogen has been studied on partially immersed platinum electrodes in acidic solutions, serving as an idealized model for a gas diffusion electrode. The formation of the electrolyte meniscus is observed microscopically and compared to the large current increase which occurs when the electrode is partly raised above the liquid level. Potentiostatic current‐voltage curves obtained with partially immersed electrodes differ drastically from those obtained with completely submerged electrodes. The temperature dependence of the current is the same for partially and completely immersed electrodes. The findings suggest that the diffusion of molecular hydrogen through the upper edge of the meniscus and a thin liquid film above the intrinsic meniscus is the rate‐determining step. The contribution of surface diffusion of hydrogen atoms and of the diffusion of hydrogen through the bulk electrolyte to the current is negligible.