Steady‐State Composition Profiles in Mixed Molten Salt Electrochemical Devices: II . Molten Carbonate Fuel Cell Analogs

Abstract

Steady‐state equations, derived previously for composition gradients in battery analogs with binary mixtures of molten salts as electrolytes, have been modified to apply to molten carbonate fuel cells. Since neither of the two like‐charged cations of the electrolyte reacts at the electrodes, the concentration gradient arises only from the difference in the mobilities of the two cations. Conditions of current density, electrode separation, electrolyte composition, and temperature that favor either steady state or precipitation of a solid phase are presented in parametric form. Numerical solution of the diffusion‐migration equation is used to predict the development with time of the concentration gradient. The computation also simulates the variations with time of emf between anode and cathode both during current flow and during the subsequent decay on open circuit. An electrochemical method for estimation of the interdiffusion coefficient and the ion mobility ratio in a binary electrolyte is outlined.