Failure Mechanism of PEM Fuel Cell after a Durability Testing of 1000 h Under High Back Pressures

Abstract

Proton exchange membrane fuel cells (PEMFCs) are expected to service under relative higher back pressures due to the target of higher outpower. In this condition, the durability of fuel cells will be a huge challenge for commercialization. In our study, we performed a 1000-hour durability experiment on a PEMFC in order to investigate the durability under high back pressures. A semi-empirical fuel cell polarization curve model was used to separate the activation losses and concentration losses and study their changes with testing time at different current densities. In addition, we investigated the charge transfer resistance (Rct) related to the oxygen reduction reaction (ORR) in the catalyst layer, and the mass transfer resistance (Zd) though Electrochemical Impedance Spectroscopy (EIS). Moreover, the contact angle and Energy-Dispersive X-Ray spectrum (EDX) of carbon paper surface were characterized. The result indicated that the rise of mass transfer resistance was the biggest contribution to the loss of cell voltage with testing time. The decrease of the contact angle of carbon paper surface implied that the weakening of hydrophobicity contributed to the increase of mass transfer resistance, which comes from the PTFE loss observed from EDX. This may result from the aggravating corrosion of PTFE or physical erosion induced by the flooding in fuel cell under high back-pressure. More stable GDL should be developed to meet the needs of PEM fuel cells with high performance and long lifetime. Figure 1