Behavior of Water below the Freezing Point in PEFCs

Abstract

This study investigates the phenomenon of water freezing below the freezing point in polymer electrolyte fuel cells (PEFCs). To perform in-situ observation of the fuel cell, a system capable of simultaneously observing inside the fuel cell with visible and infrared images was developed. Liquid water transportation was confirmed at -10 ºC when remaining water was dried enough inside the fuel cell before cold starting. The water generated on the gas diffusion layer expanded inside the gas flow channel with the water temperature at approximately - 10 ºC. Upon freezing, the water temperature rose significantly. This result indicates that the water is in a super-cooled state. Based on these results, it is confirmed that it is possible to generate a fuel cell maintaining water in a super- cooled state and fuel cell performance was dramatically improved by keeping the super-cooled state of water.