Preparation and characterization of SOFC cathodes made of SSC nanofibers

Abstract

Sm0.5Sr0.5CoO3−δ (SSC) nanowires with 20–100nm diameters were prepared by electrospinning. Subsequent calcination and fragmentation by ultrasonic vibration rendered short nanofibers with 10–40nm diameters and tens to hundreds nm lengths. Slurry containing SSC nanofibers was screen-printed on CGO (Ce0.9Gd0.1O1.95) disks to prepare SSC/CGO/SSC symmetrical cells. Similar symmetrical cells were also prepared using SSC powder derived from the glycine-nitrate combustion method for comparison. AC impedance measurement of the symmetrical cells under open circuit condition revealed that the electrolyte/nanofiber-electrode interfacial area specific resistances (ASR) were 0.533, 0.187, 0.061, 0.026 and 0.010Ωcm2 at 500, 550, 600, 650 and 700°C, respectively. These values were several to more than ten times smaller than the corresponding values of the powder cathodes. The large surface area of the nanofibers provide a large number of reaction sites for oxygen reduction and hence low ASRs. A NiO–CGO/CGO/SSC (nanofiber) single cell was also prepared and tested using humidified H2 as fuel and air as oxidant, the peak power output at 700°C is 1.09Wcm−2.