Abstract:

The cathode with high performance is a key factor to improve the electrochemical properties of SOFC. In order to increase the electrochemical properties and reduce the polarization impedance of the cathode, LSCF (La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ)-GDC(10GDC) porous cathode was dipped by the LSM(La_0.85Sr_0.15MnO₃) sol which was prepared via Pechini method, and then the LSM-LSCF-GDC three-phase composite cathode was constituted after calcinations. To improve the efficiency of impregnation, LSM sol with different pH was used to impregnate. The pH of LSM sol was the most important factor which affected impregnated effect and amount of impregnation. The complex colloid particles was negatively charged when LSM sol appeared weak alkaline. Meanwhile, a large number of negative charges was existing on LSCF-GDC hole inner wall, indicaing the repelling force was the main force between the colloid particles and hole wall, helpful to the LSM colloid particles impregnate into the inside hole of the cathode. The results showed that the generated LSM nano particles could be evenly distributed on the inner wall of the cathode skeleton when the pH of LSM sol was equal to 8.0. Cathode polarization impedance increased firstly and then reduced with the increase of impregnation times. The composite cathode impregnated in LSM sol for 3 times attained the minimum polarization impedance of 0.16 Ω•cm² (700℃in the air). The maximum power densities of impregnated and un-impregnated cells were 0.645 W/cm² and 0.503 W/cm², respectively, at the working temperature of 700℃, using 3% H₂+H₂O as fuel and air as oxidizing gas.

Key words: sol impregnated method, solid oxide fuel cell, three-phase composite cathode, pH