Fabrication and characterization of composite electrolyte for intermediate-temperature SOFC

In this study, a ceria-based composite electrolyte was investigated for intermediate-temperature solid oxide fuel cells (SOFCs) based on SDC-25wt.% K₂CO₃. Sodium carbonate co-precipitation process by which SDC powder was adopted and sound cubic fluorite structure was formed after SDC powders were sintered at 750°C for 3h. The crystallite size of the particle was 21nm in diameter as calculated from data obtained through X-ray diffraction. The conductivity of the composite electrolyte proposed in this study was much higher than that of pure SDC at the comparable temperature of 550-700°C. The transition of the ionic conductivity occurred at 650°C. Based on this type of composite electrolyte, single cell with the electrolyte thickness of 0.3mm were fabricated using dry pressing, with nickel oxide adopted as anode and SSC as cathode. The single cell was then tested at 550-700°C on home-made equipment in this study, using hydrogen/air. The maximum power density and open circuit voltage (OCV) achieved 600mWcm^-2 and 1.05V at 700°C, respectively.