Characteristics of Performance Degradation Caused by Repeated Cold Start below Freezing Point in a Polymer Electrolyte Fuel Cell(Thermal Engineering)

Abstract

This study investigates the characteristics of performance degradation caused by repeated cold starts of an MEA below freezing point in PEFC. It was made clear by this study that significant decay of performance was caused by repeated sequence of 50 cycles of freeze, cold start, operation and thaw under constant environmental temperature of -30deg. C. By applying Tafel analysis, it was made clear that performance degradation is expressed mainly by the increase in activation overpotential and concentration overpotential and the increases are in proportion to repeated cycle number. It was also found that performance decay appeared mainly in the cathode as measured by cyclic voltammetery (CV) and AC impedance spectroscopy (ACIS). New Diagnostic measurement that is application of Transmission Line Model as equivalent circuit revealed that increase of impedance in proton conductivity of ionomer in cathode catalyst layer was dominant.