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Co-free La 0.6 Sr 0.4 FeO 3-δ (LSFNb 0) and La 0.6 Sr 0.4 Fe 0.9 Nb 0.1 O 3-δ (LSFNb 0.1) perovskite oxides were prepared by a standard solid-state reaction method. The structural stability and electrochemical performance of La 0.6 Sr 0.4 Fe 0.9 Nb 0.1 O 3-δ as both cathode and anode were studied. Nb dopant in LSFNb 0 significantly enhances the structural and chemical stability in anode condition. At 800 °C, the polarization resistances (Rp) of LSFNb 0.1 symmetric electrode based on YSZ electrolyte are 0.5 and 0.05 Ω cm2 in H 2 and air, respectively. The peak power densities of LSFNb 0.1 based on LSGM electrolyte-supported SSOFCs are 934 and 707 mW cm−2 at 850 °C in H 2 (3% H 2 O) and dry CO, respectively. Moreover, the symmetric cell exhibits reasonable stability in both H 2 and CO fuel, suggesting that La 0.6 Sr 0.4 Fe 0.9 Nb 0.1 O 3-δ may be a potential symmetric electrode material for hydrogen and carbon monoxide SOFCs. • The substitution of Nb improves the structural stability of La 0.6 Sr 0.4 FeO 3 in H 2. • The polarization resistances of LSFNb symmetric cells are 0.5 and 0.05 Ω cm2 in H 2 and air, respectively. • The peak power densities of LSFNb symmetric cell are 934 and 707 mW cm−2 at 850 °C in H 2 (3% H 2 O) and dry CO, respectively. [ABSTRACT FROM AUTHOR]

La-doped Sr 2-x La x Fe 1.5 Mo 0.5 O 6-δ perovskite oxides are synthesized and used as a symmetric electrode to evaluate the effect of La on the crystal structure, conductivity, and catalytic activity for O 2 reduction and H 2 oxidation reaction. The electronic doping effect dominates the oversize effect in Sr 2-x La x Fe 1.5 Mo 0.5 O 6-δ oxide, resulting in unit cell volume expansion and decreased conductivity in air. In addition, the introduction of La increases the chemical structural stability of Sr 2 Fe 1.5 Mo 0.5 O 6-δ in reducing condition due to the higher La–O bond compared with Sr–O bond, leading to high catalytic activity for the H 2 oxidation reaction. At 800 °C, the R p values of Sr 1.9 La 0.1 Fe 1.5 Mo 0.5 O 6-δ symmetric cell in air and wet H 2 are as low as 0.075 and 0.21 Ω cm2, respectively. Moreover, the peak power densities of 769, 561, 439, and 653 mW cm−2 at 850 °C are obtained when wet H 2 , CO, CH 4, and C 3 H 8 are used as fuels on Sr 1.9 La 0.1 Fe 1.5 Mo 0.5 O 6-δ /LSGM/Sr 1.9 La 0.1 Fe 1.5 Mo 0.5 O 6-δ cell. The symmetric cell also shows excellent stability (>100 h) in wet H 2 /air, implying Sr 1.9 La 0.1 Fe 1.5 Mo 0.5 O 6-δ oxide is a promising symmetric electrode material. [Display omitted] • The substitution of La improves the stability of Sr 2 Fe 1.5 Mo 0.5 O 6-δ in reducing atmosphere. • La enhances the catalytic activity for H 2 oxidization reaction (HOR). • High electrochemical performance is obtained for SLFM symmetric cell under carbon-based fuels. [ABSTRACT FROM AUTHOR]