Life study of a PBI-PEM fuel cell by current distribution measurement

Abstract

PBI-based polymer electrolyte membrane (PEM) fuel cells have short durability comparing with Nafion ones. It is known that the presence of phosphoric acid accelerates catalyst sintering, and the polymer is susceptible to getting degraded via oxidative degradation. However, the influence of the current distribution on the degradation process has not been investigated. In this work, current distribution was measured continuously during a steady state life test that was performed in a 50-cm2 PBI-PEM fuel cell. The membrane-electrode assembly was prepared using techniques that are supposed to ensure satisfactory reproducibility at global level. Two different stages, i.e., activation and degradation, were identified. They show disparities in both global and local performance. It was found that the current distribution map is very heterogeneous, with variations around ±50 % with respect to the average value during the whole lifetime of the cell. The non-uniformity of the current profile increases during the degradation, but it cannot be concluded that the current density distribution contributes to the short lifetime.