固体酸化物形燃料電池燃料極の酸化還元サイクル下での性能変化メカニズムの解明

抄録

Mechanism of performance change in Ni-YSZ anode of solid oxide fuel cell under redox cycles was investigated by microstructure analysis and electrochemical simulation. Performance enhancement was observed just after the redox treatment, and faster degradation proceeded in the subsequent discharge process. This trend continued throughout the entire redox and discharge cycles. Thin and elongated Ni particles were observed just after the initial redox. Ni became much thinner and smaller as the number of redox and discharge cycles is increased. From the three dimensional microsturucture reconstruction by focused ion beam-electron microscopy, triple phase boundary (TPB) density showed an increase just after the redox treatment and decreased during the subsequent discharge process, which is consistent with the cell performance change. However, after repeating redox and discharge cycles, TPB density gradually increased in spite of the degradation of the cell performance. Electrochemical simulation was conducted using reconstructed microstructures. Degradations of local reaction rate at TPB or ionic conductivity of YSZ are considered as the causes for the degradation mechanism.