Effect of defective cells on the temperature distribution of a proton exchange membrane fuel cell stack

Proton exchange membrane fuel cell (PEMFC) stacks may encounter performance degradation or even damage during long-term operations, while the influence of defective cells on the stack performance still remains inadequately understood. In this study, the effect of defective cells on the stack temperature distribution was experimentally investigated. Two defective cells of different defect degrees were prepared by controlling hydrogen starvation time and quantitively characterized by the polarization curves, electrochemical impedance spectroscopy (EIS), and galvanostatic charge method (GCM) tests. Results show that the presence of defective cells reduces the stack performance and the temperature distribution uniformity. The increment of stack temperature and decrement of stack temperature uniformity is more prominent (with 0.9 degrees C and 0.31 degrees C at 0.8 A cm(-2), respectively) when the defective cell is located at central stack. The peak sub-cell regional temperature rise can even reach 2.9 degrees C. For defective cells with a relatively low degree of defect, the reverse current density is high, thus leading to an increased heat generation with the average sub-cell regional temperature increment of 0.5 degrees C and causing adjacent normal cells to operate at higher temperature. For defective cells with an excessive degree of defect, polarization reverse occurs at low current densities, resulting in significant voltage losses and reduced performance of the stack. The present results are insightful for developing thermal management strategies for the long-term operation of PEMFC stacks.