Electrochemical Performance of Ni1-xCox-GDC Cermet Anodes for SOFCs

Electrochemical performance of Ni1-xCox-GDC (Gd0.1Ce0.9O1.95) cermet was studied for the use as a novel anode for solid oxide fuel cells (SOFCs). Ni1-xCoxO (x=0.25, 0.5, 0.75) was prepared from NiO and Co3O4 compounds via a solid state calcination at 1000 °C for 10 h in air. A progressive increase in lattice parameters of the Ni1-xCoxO as x was increased suggested the extent of solid solution between NiO and Co3O4. The trace of free Co3O4 was found only in the Ni0.25Co0.75O calcined powder indicating incomplete dissolution between NiO and Co3O4 at this condition. After reduction at 800 °C for 2 h in H2, the interfacial polarization resistance and current-voltage (I-V) of the Ni1-xCox- GDC//YSZ//LSM-YSZ cells were measured at the temperatures between 650 and 800 °C. Grain growth and coarsening of the Ni1-xCox-GDC cermet was generally observed when the amount of Co atomic fraction was increased especially at x = 0.75. The Ni0.75Co0.25-GDC anode exhibited the better uniform microstructure, as compared to other composite anodes, resulting in enhanced electrochemical performance of the cells. When the grain coarsening occurred, suppression of the overall electrochemical performance of the cells was obtained.