Kazuhiro Teranishi

Magnetic Resonance Imaging of the Water Distribution within a Polymer Electrolyte Membrane in Fuel Cells

Magnetic resonance imaging (MRI) to measure the spatial distribution of the water content within a polymer electrolyte membrane (PEM) under fuel cell operation is described. By designing and building a fuel cell that can operate in an MRI system and making measurements during the cell operation, the water concentration gradient in the PEM and the overall water content decreased with an increase of the cell current. Furthermore, the water content in the anode side of the PEM decreased significantly within 200 s of the cell start-up, and this caused a similarly rapid decrease of the cell voltage.

Degradation Mechanism of PEMFC under Open Circuit Operation

We present a durability test of polymer electrolyte membrane fuel cell (PEMFC) in open circuit condition. Such a condition enhances the deterioration of the membrane electrode assembly. ac impedance spectroscopy measurements and scanning electron microscopy observation suggest that the degradation occurred at the cathode. Direct gas mass spectroscopy of the cathode outlet gas indicated the formation of HF, H 2 O 2 , CO 2 , SO, SO 2 , H 2 SO 2 , and H 2 SO 3 . A kinetic model is presented assuming that the H 2 gas cross leakage from the anode caused the cathode degradation. The model determines the rate of degradation using the permeability across the electrolyte membrane measured for crossover H 2 gas.

Analysis of Water Transport in PEFCs by Magnetic Resonance Imaging Measurement

Management of water is one of the most important issues that limits the operation of polymer electrolyte fuel cells (PEFCs). To better understand water transport in polymer electrolyte membranes (PEMs), a one-dimensional model has been analyzed for water transport in a PEM. To increase the model accuracy, magnetic resonance imaging (MRI) experiments were done to determine the optimum parameters for the model. Using the resulting parameters, we programmed the measured number of maximum water content of the membrane in a fuel cell and water transfer coefficient of the membrane surface. The resulting water distribution of the PEM under various operation conditions was consistent with previous MRI measurements.

Nitrogen Oxide Sensors Based on Yttria-Stabilized Zirconia Electrolyte and Oxide Electrodes

Mixed potential sensors for the detection of hydrocarbons and carbon-monoxide have been previously studied at Los Alamos National Laboratory (LANL). The LANL sensors have a unique design incorporating dense ceramic-pellet/metal-wire electrodes and porous electrolytes. When these sensors are exposed to various gases, in addition to their mixed-potential response, their resistance changes. This change in resistance is probably associated with the oxygen reduction reaction at the electrode/electrolyte interface and can be used to yield a total NO, response. The NO x sensors are operated in a current bias mode where the voltage response is related to the total NO, concentration.