Local impact of load cycling on degradation in polymer electrolyte fuel cells

Abstract

Degradation mechanisms occurring during proton exchange membrane fuel cells (PEMFC) operation critically depend on the applied electrical load profile. In this work, durability tests were performed using different load cycling ranges. The tests include refresh procedures in order to recover temporary performance losses. Operando current density distribution measurements as well as electrochemical characterization techniques were applied to obtain essential data for understanding degradation behavior of the components of the membrane electrode assembly (MEA). The analysis is supported by scanning electron microscopy (SEM) and energy dispersive x-ray diffraction (EDX) analysis of MEA components. Dynamic load cycling has proven to lead to lower performance losses as compared to constant load operation. Moreover, reversible performance losses were associated with an increased heterogeneity of the current density distribution along the flow field. Thereby, areas with high local current density exhibit particularly strong Pt band formation in the membrane linked with a thinning of the cathode catalyst layer.