Modeling the effect of dissolved gas on the bubble layer along a vertical gasevolving electrode

Abstract

During water electrolysis for the production of hydrogen and oxygen, many bubbles are formed at the electrodes. The presence of these bubbles causes a number of side effects such as a significant increase in the total cell resistance (e.g., electrical circuit resistances, transport related resistances, and electrochemical reaction resistances). The efficiency of water electrolysis is therefore closely related to the presence of bubbles in the electrolyte.
In this work, the focus is on the numerical modeling of the evolution of the bubble layer in a vertical channel with gasevolving electrodes on either side of the channel. One of the problems is the growth of rising bubbles along the electrode, which affects the shape and thickness of the bubble layer. This bubble growth depends on four main phenomena, e.g., bubble coalescence, change in hydrostatic pressure, presence of water vapor, and mass transfer of dissolved gas. Of these, the mass transfer of
dissolved gas contributes the most to bubble growth. Accounting for this growth can be crucial to the
computational effort to accurately simulate the bubble plume shape and thickness.
By coupling a multiphase flow model to the transport of dilute species, the bubble layer could be simulated. The simulation results were compared with experimental data, which showed that including mass transfer in the simulations could accurately simulate the bubble layer (in shape and thickness) over a wide range of different operating conditions.