Performance of chromium-poisoning resistance of Gd_0.2Ce_0.8O₂-impregnated LaNi_0.6Fe_0.4O_3-δ cathode materials

The symmetric cell LaNi_0.6Fe_0.4O_3-δ (LNF)/Sc_0.1Zr_0.9O_1.95 (ScSZ)/LaNi_0.6Fe_0.4O_3-δ (LNF) was fabricated with screen printing and co-sintering methods. Using cerium nitrate and gadolinium nitrate as raw materials, citric acid as fuel, LNF cathode modified by impregnating with 21.3% mass fraction of Gd_0.2Ce_0.8O₂ (GDC) was prepared using combustion method. Electrochemical impedance spectra (EIS) show that, specific polarization resistance is 0.70 Ω·cm²and 0.13 Ω·cm² for LNF and 21.3% mass fraction of GDC-impregnated LNF cathode at 750 ℃, respectively. Specific polarization resistance of LNF cathode in absence of Cr-base alloy at 750 ℃ after holding of 500 h attains to 2.36 Ω·cm² while that of the 21.3% mass fraction of GDC-impregnated LNF in the same conditions after holding of 1 200 h attains to 0.40 Ω·cm². The impregnation of GDC speeds up the diffusion process of triple-phase boundary reaction area at gas/cathode/electrolyte and reduces cathode polarization resistance. In presence of Cr-base alloy, compared with 21.3% mass fraction of GDC-impregnated LNF, there is strong Cr₂O₃ deposition at LNF/ScSZ interface, which slows down the diffusion of active particles at triple-phase boundary. LNF exhibits far greater specific polarization resistance than that of 21.3% mass fraction of GDC-impregnated LNF. 21.3% mass fraction of GDC-impregnated LNF cathode has high tolerance towards Cr poisoning.