La1.85Sr1.15Cu2−xCoxO6+δ intergrowth oxides as cathodes for intermediate temperature solid oxide fuel cells

• Published in: Electrochimica acta Vol. 70; pp. 375 - 381
• Main Authors: Kim, Y.N., Manthiram, A.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 30.05.2012; Elsevier
• Subjects: Applied sciences; Cathodes; Composite cathodes; Crystal chemistry; Electrolytic cells; Energy; Energy. Thermal use of fuels; Equipments for energy generation and conversion: thermal, electrical, mechanical energy, etc; Exact sciences and technology; Fuel cells; Oxides; Oxygen reduction reaction; Phase boundaries; Polarization; Reduction; Solid oxide fuel cells; Thermal expansion; Solid oxide fuel cells; Composite cathodes; Oxygen reduction reaction; Crystal chemistry; Voltage current curve; Cobalt Oxides; Chemical stability; Lanthanum Oxides; Electrode material; Solid oxide fuel cell; Temperature range 400-1000 K; Surface structure; Chemical reduction; Electrocatalysis; Composite electrode; Electrochemical reaction; Modified material; Scanning electron microscopy; Oxygen; Cathode; Lattice parameters; X ray diffraction; Multi-element compound; Copper Oxides; Morphology; Thermal analysis; Strontium Oxides; Electrochemical impedance spectroscopy
• ISSN: 0013-4686; 1873-3859
• DOI: 10.1016/j.electacta.2012.03.087

► La1.85Sr1.15Cu2−xCoxO6+δ have been investigated as cathodes for solid oxide fuel cells. ► La1.85Sr1.15Cu2−xCoxO6+δ offer compatible TEC with that of GDC electrolyte. ► Co-substituted samples show enhanced electrical conductivity below 700°C. ► La1.85Sr1.15Cu1.8Co0.2O6.26+GDC composites show the lowest Rp value. The effect of the substitution of Co for Cu in the intergrowth oxide La1.85Sr1.15Cu2−xCoxO6+δ on the crystal chemistry, thermal and electrical properties, and catalytic activity for oxygen reduction reaction (ORR) has been investigated to determine its viability as a cathode material for intermediate temperature solid oxide fuel cells (SOFCs). The larger size and preference for higher oxygen-coordination number of the La3+/Sr2+ ions allow intercalation of excess oxygen between the two CuO2 layers, and vacancies are introduced into the O(1) sites of the CuO2 planes. The La1.85Sr1.15Cu2−xCoxO6+δ oxides show thermal expansion coefficients (TEC) of ∼15×10−6°C−1 that are compatible with that of the Gd0.2Ce0.8O1.9 (GDC) electrolyte in SOFC. Fuel cell data collected with electrolyte-supported and anode-supported single cells reveal that the La1.85Sr1.15Cu2−xCoxO6+δ+GDC (50:50vol.%) composite cathodes exhibit lower polarization resistance compared to the pure La1.85Sr1.15Cu2−xCoxO6+δ cathodes due to the extended triple phase boundary (TPB) where the ORR occurs. Among the various cathode compositions investigated in this study, the La1.85Sr1.15Cu1.8Co0.2O6.26+GDC composite was found to be optimal with the lowest polarization loss.