Document Type

Article

Subject Area(s)

Chemical Engineering

Abstract

A mathematical model of a hydrogen/oxygen alkaline fuel cell is presented that can be used to predict polarization behavior under various potential loads. The model describes the phenomena occurring in the solid, liquid, and gaseous phases of the anode, separator, and cathode regions, assuming a macrohomogeneous, three-phase porous electrode structure. The model calculates the spatial variation of the partial pressures of oxygen, hydrogen, and water vapor, dissolved oxygen and hydrogen concentrations, electrolyte concentration, and the solid- and solution-phase potential drops. By developing a complete model of the alkaline fuel cell, the interaction of the various transport and kinetic resistances can be more accurately investigated under conditions that simulate actual fuel cells. The model predicts that the solution-phase diffusional resistance of dissolved oxygen is a major limitation to achieving high performance at low cell potentials, while the ohmic drop in the solid electrodes contributes the most resistance at high cell potentials. Other limitations to achieving high power densities are indicated, and methods to increase the maximum attainable power density are suggested. These performance indications can help future research and the design of alkaline fuel cells.

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