High Potential Excursions during PEM Fuel Cell Operation with Dead-Ended Anode

Abstract

Operating a proton exchange membrane (PEM) fuel cell with a dead-ended anode may lead to local fuel starvation due to the excessive accumulation of liquid water and possibly nitrogen (because of membrane crossover) in the anode compartment. In this paper, we present experimental results obtained with a segmented, linear cell with reference electrodes along the gas channels, used to record local anode and cathode potentials. By simultaneously monitoring the local potentials and current densities during operation, we assessed the impact of fuel starvation on local fuel cell performance during aging protocols consisting of repeated dead-ended anode operation sequences (with anode outlet closed longer than in real use conditions). During the aging protocols, we observed strong local cathode potential excursions close to the anode outlet. The cathode showed non-uniform ElectroChemical Surface Area (ECSA) losses and performance degradation along the cell area. The damage was more severe in the regions suffering the longest from fuel starvation. Similar experiments performed in different operating conditions and with different membrane thickness showed that water management impacts significantly the cathode potential variations and thus the MEA degradation. Most of the MEA degradation is attributed to local cathode potential excursions above 1.2 V although potential cycling between 0.5 V and 0.7 V also had an impact in the regions well supplied with hydrogen (hydrogen purges were triggered when the fuel cell voltage dropped from about 0.7 V to 0.5 V). According to our results, localized and transient hydrogen starvation events may be difficult to detect by considering only the overall fuel cell performance.