Composite Electrolyte And Novel Cathode Material For Low Temperature Solid Oxide Fuel Cells

The energy crisis and environmental pollution become hot topics all over the world. New energy sources and high efficiency energy systems are urgently demanded. The new energy sources exploration is very favor to our next generation. But for a short-term view, the development of the high efficiency energy system based on the current energy sources would be more vital for our daily life. Solid oxide fuel cell (SOFC) has attracted much attention because of the high efficiency, fuel flexible and environmentally benign. While the flexibility of material choice, fuel cell fabrication cost and relative stability, compared with the high temperature SOFC, have made the intermediate temperature or low temperature SOFC the hottest fields in energy domain.This work aims to investigate the properties of the SDC-carbonate composite (SCC) electrolyte with various morphologies and the novel cathode material for LT-SOFC:1. Preparation of SCC precursor—SDC powders by three methods: citric-nitrate combustion, co-precipitation with salvolatile and solid state reaction. Some characterization was carried out to determine the affect of the physicochemical properties of the SDC to the performance of the SCCs.2. Fuel cell pellets were made by dry-pressing and co-firing process with SCC electrolyte and Ni-based electrode. The thermal,chemical compatibility between of the cell components and the short-term of discharge operation of the cell was researched. Electrochemical performance was measured and ion conduction mechanism of the electrolyte in fuel-cell condition was analyzed based on the electrochemical impendence spectroscopy (EIS).3. Novel material Pr2Ni0.76Cu0.24O4+δ(PNCO), with K2NiF4 structure, was selected for the first time as cathode material for low temperature SOFC with SCC composite electrolyte.Several aims were achieved as follows:The physicochemical feature of precursor SDC play an important rule on the electrochemical performance of the SCC composite materials and the SCC prepared by citric-nitrate combustion process shows the highest ion conductivity at the range of the operating temperature for the special microstructure and unique interface between SDC and Carbonate. The maximum power density of the cell reached 916.4mWcm-2 at 550°C. SCC show thermal and chemical compatibility with Ni-based and novel PNCO electrode. The low polarization of the electrolyte and electrode co-ensure the high performance and the short-term operation show high stability of the fuel cell. The ion conducting manner of the SCC composite electrolyte is different from that of conventional single phase electrolyte with the aid of EIS and the SCC shows hybrid H+/O2- conduction in fuel-cell condition. The interfacial ion conduction was briefly discussed by introduction of the space charge model. Fuel cell with SCC electrolyte and PNCO cathode show the maximum power density of 647.0mWcm-2 at 600°C.