Experimental Study on the Balance between Microscopic Water Production and Temperature Rise during Cold Startup in PEFC

In the startup of a polymer electrolyte fuel cell below subzero temperature, one problem is freezing of the produced water, inducing operation shutdown and various kinds of degradation of the cell performance. To evaluate the freezing behavior during rising temperature, this study conducted measurement of cold start characteristics under simulated adiabatic conditions and observation of ice distribution in the cell by a cryo-SEM. The results suggested different ice distributions depending on the timing of supercooling release, and a large influence of the ice layer formed at the interface between the catalyst layer and the MPL on the cold stat characteristics. A hydrophilic MPL was applied to improve the startup ability, and compared with the conventional hydrophobic MPL. It was shown that the hydrophilic MPL suppresses the formation of ice layer at the interface and successfully improves the startup ability, indicating a suitable structure for cold startup.