Composite electrolyte based on nanostructured Ce_0.8Sm_0.2O_1.9 (SDC) for low-temperature solid oxide fuel cells

Nanostructured Ce_0.8Sm_0.2O_1.9 (SDC) is investigated for low-temperature solid oxide fuel cells based on SDC- 30wt% (53 mol% Li₂CO₃:47 mol% Na₂CO₃) composite electrolyte in this work. SDC is prepared by the combined citrate and EDTA complexing method. X-ray powder diffraction shows that it forms a well-cubic fluorite structure after being sintered at 700°C for 2 h. The particle is about 12nm detected by the transmission electron microscopy. Conductivity for the composite is much higher than the pure SDC at comparable temperatures. A transition of ionic conductivity occurs at 450°C for the composite electrolyte. The single cells are fabricated by a simple dry-pressing process and tested at 450-600°C. A maximum power density of 900mWcm^-2 and the open-circuit voltage of 0.92V are achieved at 600°C. The conduction mechanism has been discussed by comparing the conductivity of composite electrolyte under different conditions. AC impedance for single cell indicates that the electrochemical process involving cathode and anode reactions is the rate-limiting step.