Analysis of Ice Distribution in Cathode Catalyst Layer and Shutdown Mechanism at PEFC Cold Start

Abstract

In polymer electrolyte fuel cells, the freezing of produced water deteriorates the cell performance below zero. In this study, we investigated the freezing phenomena in the cathode catalyst layer (CL) by the experiments, and identified the effects of current density, cathode gas pressure, and oxygen concentration. It was shown that the ice distribution and the estimated amount of ice produced in the CL till the shutdown depends on the current density, while they are independent of the cathode gas pressure and the oxygen concentration. To clarify the main cause dominating these tendencies, we introduced the effect of ice formation on an increase in the through-plane electrical resistance of the CL into the three phase boundary and the CL models, and examined the mechanism in the CL. The calculation results correspond to the experimental current density dependency, and the ice distribution is independent of the gas pressure and the oxygen concentration.