Investigation On Property And Performance Of Materials For Electrolyte-supported Solid Oxide Fuel Cell

Solid oxide fuel cell?SOFC?,as an efficient and clean technology,converts the chemial energy of fuel directly into electricity via electrochemical pathways without the limit of the Carnot cycle.In general,there are three supported types of SOFC:anode-supported,cathode-supportedandelectrolyte-supported.The electrolyte-supported SOFCs has the advantage that use a calcined dense electrolyte layer as the main part.Hence they have good performance in terms of heat resistance,mechanical strength and etc.In addition,the cell which has a clear structure is easily preapred,and the selection of electrode material is more extensive and flexible.Therefore,this paper based on the electrolyte-supported system to analyse and explore the properties and performance of materials of SOFCs from different aspects,and the attempts and progresses in this thesis are as follows:An approach combining electromotive force and electrochemical impedance spectroscopy techniques is established to measure the anodic and cathodic polarization resistances separately of an oxygen concentration cell with a mixed ionic-electronic conductor?MIEC?as the electrolyte.The influence of oxygen partial pressure on the electronic conductivity of the MIEC is considered.The electrode polarization resistances of an oxygen concentration cell with Pt as the electrode and samarium doped ceria as the electrolyte are measured with this approach in 600-750oC.Both the anodic and the cathodic polarization resistances increase with the decrease of oxygen partial pressure and temperature.The activation energies for oxygen reduction and evolution reactions are about 2.05 and 1.55 eV,respectively.The approach is effective when the conduction of either electrons or holes dominates in the MIEC.The effects of Mo doping into La_0.3Sr_0.7TiO_3-?perovskite on its ionic conductivity and catalytic activity as an anode material of solid oxide fuel cells have been investigated.The partial substitution of Ti by Mo reduces the bond energy between metal and oxygen ions in the perovskite.The concentration of Mo⁵⁺/Mo⁶⁺redox couples increases with the rise of the content of Mo,while the oxygen ionic conductivity decreases simultaneously.The doping of Mo significantly reduces the anodic polarization resistance and improves the performance of the single cell.The cell with La_0.3Sr_0.7Ti_0.97Mo_0.03O_3-?anode and La_0.9Sr_0.1Ga_0.8Mg_0.2O_3-?electrolyte exhibits a maximum power density of 135 mW cm^-2 at 850 ^oC with hydrogen as fuel.