Multiscale Modeling of Gas Evolving Electrodes

Multiscale Modeling of Gas Evolving Electrodes

Mehmet Moralı¹, Palgat A. Ramachandran¹ and Milorad P. Duduković¹

¹Washington University in St. Louis

Abstract

Gas evolving electrochemical systems are widely used in industry, such as in chlorate, chlor-alkali and hydrolysis of water. These systems might form bubbles on one or both of the electrodes. Once bubbles depart from the electrode surface, they form a bubbly layer. This layer presents resistance to current flown and demands higher cell potential, requiring more energy to preserve fast reaction rates. The thickness of the bubbly layer increases with increasing height, causing lower current densities in the upper section of the electrode. This creates negative feedback, reducing the formation rate of bubbles and affecting bubble layer thickness. We present a multiscale model by which the bubble layer thickness is calculated by a Eularian – Lagrangian scheme for which the effective medium is approximated by a submodel.  The accuracy of the submodel is further investigated by Monte-Carlo simulations.  

Key words

Multiscale modeling, gas evolving electrodes, gas hold-up, effective medium approximation