Effects of metal doping on La2NiO4 as cathode for solid oxide fuel cell

Abstract

The properties of La₀.₈Sr₀.₂)₂₋ₓCaₓNiO₄ (LSN-Caₓ), (La₀.₈Sr₀.₂)₂₋ₓCaₓNi₀.₉Co₀.₁O₄ (LSNC-Caₓ and La₂₋ₓ Caₓ Ni₀.₉₋ᵧ Co₀.₁(Fe,Zn)ᵧ O₄ (LNCF-Caₓ and LNCZ-Caₓ) as cathode materials for solid oxide fuel cell were investigated. All compounds prepared by modified citrate method exhibited K₂NiF₄-type with tetragonal structure using calcination and sintering temperature of 900℃ and 1350℃ for 10 hours, respectively. LSN-Caₓ and LSNC -Caₓ (x=0-0.5) substituted with Ca²⁺ on the A-site in composition of x=0.2 showed the single phase of K₂NiF₄-type structure and the highest electrical conductivity of 176.9 and 166.9 S/cm at 800℃, respectively. To improve oxygen permeation of La₂ Ni₀.₉ Co₀.₁O₄ (LNC), Ni-Site was firstly substituted with Fe³⁺ or Zn²⁺ to obtain LNC-Feᵧ and LNC-Znᵧ (y=0-0.2). Then Ca²⁺ was incorporated into La-site of LNC -Fe₀.₀₅ and LNC-Zn₀.₀₅ which had the highest oxygen permeation rate, to improve the electrical conductivity. The highest electrical conductivity was achieved for LNCF-Ca₀.₅ and LNCZ-Ca₀.₅ and the values were 98.4 and 84.9 S/cm at 800℃. Additionally, the single cell performance of LNCF-Ca₀.₅ and LNCZ-Ca₀.₅ with LSGM electrolyte was measured and maximum power densities were 322 and 312 mW/cm² at 800℃, respectively. This indicated that LNCF- Ca₀.₅ and LNCZ-Ca₀.₅ could be potential cathode materials for IT-SOFC.