Synthesis and characterization of NiO-YSZ for SOFCs

Nickel oxide and yttria-stabilized zirconia ceramic materials were prepared by three methods: physical mixture, a modified Pechini route, and impregnation with Ni(NO3)2·6H2O. Temperature-programmed reduction (TPR) analysis showed the presence of different reduction peaks for each sample and that the reduction temperature was influenced by the employed preparation procedure. Nickel oxide species are completely reduced at temperatures up to 1000 °C and their temperature-programmed reduction profiles indicated that a higher temperature reduction corresponds to a higher calcination temperature. Furthermore, the composites synthesized through impregnation presented nickel oxide species more easily reducible than those prepared by the two other methods. Scanning electron microscopy and X-ray photoelectron spectroscopy (XPS) evidenced a larger nickel oxide coating on yttria-stabilized zirconia for the composite synthesized through the impregnation method. The electrical conductivity of impregnation sample was 117 S cm−1 at 850 °C, a value three times higher than that of the physical mixture.