Nishorting in relation to acid‐base equilibrium of molten carbonate for molten cabonate fuel cell (MCFC) application

Abstract

One of the important methods to improve the endurance of the molten carbonate fuel cell is to reduce the nickel precipitate that forms the shorting. The nickel precipitate shorting consists of three processes: the dissolution of the NiO cathode, the flux of the nickel ion to the anode side, and the reduction to metal by hydrogen from the anode side. The NiO solubility affects all processes of the shorting. The dissolution of the NiO in the molten carbonate is an acidic dissolution mechanism in the range of the practical operating conditions of the molten carbonate fuel cells. Therefore, to reduce the solubility of NiO, a basic molten carbonate must be selected. These behaviors are explained by the fact that the solubility of the NiO in the molten carbonate is a function of the Coulomb force parameter that indicates charge density of the molten salts. The time function of the nickel shorting can be described by experimental equations. On the basis of an interpretation of the experimental equations and the simple model of the nickel shorting based on the diffusion of the nickel ion, it is seen that the reduction in the solubility improves the durability of the molten carbonate fuel cells.