Analysis of Ice Formation Process in Cathode Catalyst Layer of PEFC at Cold Start

Ice distribution in a cathode catalyst layer of a polymer electrolyte membrane fuel cell is investigated during the process of cold start operation using a cryo-SEM. The observation results show that at higher startup current densities, ice grows from the membrane side to the gas diffusion layer side and that this becomes more pronounced when increasing the current density, while the ice distribution in the cell is nearly uniform at a lower current density. The ice formation processes observed by the cryo-SEM are analyzed using three-phase boundary and catalyst layer models, and the freezing mechanism at cold starting is discussed.