Redox catalysis of absorption from reactive bubbles near electrodes

Electrolyzing sparingly soluble gases as they are absorbed from bubbles can be significantly facilitated by addition of a soluble redox couple which serves to increase both mass and charge transfer rates. A diffusion layer model is used to calculate reaction‐catalyzed mass transfer rates in regions of boundary layer penetration by reactive bubbles for the case of (m, n)‐order irreversible homogeneous reaction. The dissolved redox catalyst is continuously regenerated at the solid electrode surface. Approximate solutions, which relate surface flux to concentration driving force, are in excellent agreement with the numerical solutions under conditions of fast homogeneous reaction and concentrated catalyst (modified Damköhler number and dimensionless catalyst concentration greater than 3). Diffusion layer thickness is calculated from the mass transfer coefficient k_p in penetrated regions. A model based on spherical penetrating bubbles is used to determine k_p and specific surface area a_p of penetrated regions from k_pa_p values that have been measured in gas‐liquid flow through a packed bed. The mass transfer behavior provides useful insight into why the penetration process is so effective in increasing overall reaction rates.