Flow-through and flow-by porous electrodes of nickel foam Part IV: experimental electrode potential distributions in the flow-through and in the flow-by configurations

Experimental distributions of the solution potential in flow-through and flow-by porous electrodes of nickel foam operating in limiting current conditions are presented. These are in good agreement with the corresponding theoretical distributions. In the case of a flow-by configuration used in a two-compartment cell, the experiments confirm the validity of the models, presented in Part III, which take into account the presence of a separator (ceramic porous diaphragm or ion exchange membrane).Nomenclature a_e specific surface area per unit volume of electrode - C₀ entrance ferricyanide concentration (y=0) - D molecular diffusion coefficient of ferricyanide - E_e cathode potential - F Faraday number - mean (and local) mass transfer coefficient - L electrode thickness - L_s-L separator thickness - m number of sheets of foam in a stack - n number of terms in Fourier series - Q volumetric flow-rate - r_s ohmic specific resistance of the separator - mean flow velocity based on empty channel - V constant potential - X conversion - x coordinate for the electrode thickness - y coordinate for the electrode length - y₀ length of the porous electrode - z number of electrons in the electrochemical reactionGreek symbols parameter - parameter - ionic electrolyte conductivity - _sc solution potential in the pores of the cathode - _M matrix potential (_sc = constant) - parameter [=n/y₀] - electrolyte density - mean porosity - kinematic viscosity - E_c potential drop in the porous cathode - potential drop defined in Fig. 5Indices c cathodic - o electrolyte alone - s separator