(Digital Presentation) Correlative Evaluation Between Water Concentration and Voltage Fluctuation of PEFC Under Low-Humidity and Load-Change Operations Based on Laser Spectroscopy

To investigate the voltage undershoot behavior in polymer electrolyte fuel cells (PEFCs) operated under low-humidity and load-change conditions, it is necessary to precisely grasp the transient water transport within the cell. This study has developed a single-ended fiber-optic sensor to quantify the water vapor concentration in flow channels of PEFCs based on laser spectroscopy and investigated the correlation between the water behavior in the anode and the voltage fluctuation during low-humidity and current-cycle operations. The effects of inlet humidification, load current range and compression pressure on the voltage undershoot were also examined. The results revealed that the large undershoot and the temporal drop of anode water concentration occurs due to the strong electro-osmotic effect when the current density increases steeply at the low humidifications of Anode/Cathode=30/0, 0/30, 30/30 %RH. It was also found that the high load current of 1.0 A/cm2 and the strong cell compression of 2.0 MPa reduces the undershoot after several current cycles because of the water accumulation on the anode side.