Reduction of metal ions in dilute solutions using a GBC-reactor - Part II:Theoretical model for the hydrogen oxidation in a gas diffusion electrode at relatively low current densities

The GBC-reactor is based on the combination of a gas diffusion anode and a porous cathode. A theoretical model for gas diffusion electrode, valid at r elatively low current densities, is derived. This is based on the pseudohom ogeneous film model including an approximation of the Volmer-Tafel mechanis m for the hydrogen oxidation kinetics. Results show a severe mass transfer limitation of the hydrogen oxidation reaction inside the active layer of th e gas diffusion electrode, even at low current densities. Empirical formula e are given to estimate whether leakage of dissolved hydrogen gas into the bulk electrolyte occurs at specific process conditions. A simplified versio n of the model, the reactive plane approximation, is presented.