Mathematical modeling of gas evolution from flowing electrolytes on stable porous anodes of finite matrix phase conductivity

A mathematical model was developed to simulate the effects of the matrix phase conductivity on the behavior of flow-through porous anode operating for gas evolution reaction. The anode material was assumed to be stable and has a finite conductivity. The model accounts for the conductivities of the solution and the matrix phases, the electrode kinetics, hydrodynamics and gas bubble formation. The different ratios and values of the matrix conductivity group, K_σ (a measure of the matrix conductivity) and the electrolyte conductivity group, K_κ (a measure of the electrolyte conductivity) were found to have significant effects on the distributions of current, potential and gas void fraction. When K_σ was a finite value the reaction was pushed towards the back of the electrode and when K_κ was finite the reaction was pushed towards the front face. The effects of the bubble group, χ on the potential and current distributions were investigated under different impacts of K_σ and K_κ. When K_σ was limited the gas bubbles formed at the back of the electrode were forced to travel within the whole bed with the electrolyte streams, causing larger accumulation of the bubbles and hence higher polarization within the bed. The gas bubble formation limited the conductivity of the pore electrolyte resulting in potential and current distributions similar to the case of finite electrolyte conductivity.