Characterization of the Cathode-Electrolyte Interface of VPS SOFC

摘要

In this study the electrochemical behavior of different VPS cathode-electrolyte interfaces with that of a screen printed cathode on a plasma sprayed electrolyte is compared. The measurements were carried out at temperatures from 850℃ to 600℃ in steps of 50 K. The activation energy of the different LSM and LSF VPS cathodes is about 1.6 eV; the activation energy for the screen printed cathode is about 1.9 eV. The polarization resistance Rp obtained at 800℃ from impedance measurements in air and OCV condition of the LSM VPS cathodes is significantly higher (approximately 3 Ωcm~2) than the R_P of the LSF VPS cathodes (0.35 Ωcm~2). Measurements on SOFCs based on metallic substrates show that the influence of the VPS parameters is not as high as the influence of the choice of materials. Using LSF cathodes, the power density is increased by approximately 30% (at a fixed current density) compared to LSM cathodes. The screen printed LSM cathode used as a reference allows higher power densities than LSM VPS cathode. Microstructural analysis using SEM demonstrates the feasibility of very porous vacuum plasma sprayed cathodes.