Effects of property variation and ideal solution assumption on the calculation of the limiting current density condition of alkaline fuel cells

A computational study of the electrochemical hydrodynamic process in an alkaline fuel cell was conducted. The computation relaxed the ideal solution assumption, accounted for thermodynamic solubility of the reactants, and allowed for property variations due to temperature and concentration effects. The results showed that the ideal solution assumption is not adequate for calculation of the transport process of the concentrated electrolyte considered, 7 M. The ideal solution formulation resulted in a lower limiting current density condition by about 50% than that predicted by the non-ideal solution formulation. The study also showed that the thermal condition is important to the calculation of the limiting current density condition. The calculated limiting current density increased by about 30% when the boundary condition was changed from isothermal to adiabatic. The computational results suggest that maintaining a uniform KOH concentration in the electrolyte (for example, at design point of 7 M) be an effective measure to increase the limiting current density condition.

Research highlights
► The ideal solution assumption was relaxed and effects of boundary condition examined.
► The ideal solution assumption underestimates the limiting current density condition.
► Isothermal BC yields a higher limiting current density than an adiabatic BC.
► Uniform electrolyte can increase the limiting current density condition.