Development of Novel Cathode Materials (RexLa0.6-xSr0.4Co0.8Fe0.2O3) for Intermediate Temperature Solid Oxide Fuel Cells (Re=Rare earth element series

Solid oxide fuel cells (SOFCs) can be considered as an alternative to traditional power generation sources such as coal, gas and biomass. In a SOFC, renewable fuel sources such as hydrogen is converted to electricity in a high to intermediate temperature solid-state electrochemical cell operating typically between 500 to 900 C. The fuel cell technology addresses an important issue of greenhouse gas emissions such as CO2 and CH4 which leads to global warming. SOFCs, in generating energy, could potentially meet not only the needs of the growing world population but would also be a cleaner, environmentally friendly source of energy. SOFC technology could address the future issue of the energy trilemma (energy security, sustainability and affordability) that the next generation could face if left unaddressed and neglected in the current times. SOFCs have the benefit of operating at a high efficiency of over 70%. Leeds research group has already developed new fast oxide-ion conducting solid electrolyte in a currently ongoing PhD research project. Since the porous Ni-based composite anode is well established, we intend to focus on the development of novel cathode materials to couple with the already developed solid electrolyte and established anode for the development of IT-SOFC operating between 600 - 800 C. The high surface area nanopowders of rare-earth (Re) co-doped LSCF (RexLa0.6-xSr0.4Co0.8Fe0.2O3) will be used for the development of a novel cathode. The development of cathode materials will be carried out systematically through RexLa0.6-xSr0.4Co0.8Fe0.2O3 nanopowders synthesis by the Leeds Alginate Process (LAP) originally developed by the research group at Leeds University in three previous PhD projects. This is an alginate mediated cation-exchange method developed by researchers at Leeds that has potential of yielding consistently high purity single phase complex oxide nanopowders with relative ease at low cost. A range of experimental techniques will be employed to determine the chemical, physical, thermal, magnetic, structural, catalytic, electrochemical and electrical properties of the high surface area nanopowders of Re-co-doped LSCF cathode materials by the alginate mediated ion-exchange process. The resulting cathode nanopowder and the cathode/electrolyte composite will then be pressed uniaxially to form discs and sintered at a range of different temperatures in order to study the chemical compatibility of materials in the selected temperature range. We will then evaluate the thermal, physical and chemical properties by differential scanning calorimetry, dilatometry and thermogravimetric analysis (DSC-TGA), Brunauer-Emmett-Teller (BET), X-ray fluorescence (XRF); magnetic and structural properties by X-ray Diffraction (XRD), High temperature-XRD, Scanning electron microscope, Transmission electron microscope and Laser
Raman spectroscopy. Electrical properties will be evaluated by ac-impedance spectroscopy, half-cell manufacture by coating of solid electrolyte on porous cathode by spin coating or pulsed laser deposition (PLD), half-cell potentials by measuring open circuit potentials, area specific resistance of half-cell by ac-impedance spectroscopy. To consider the oxygen reduction capability of the cathode material, we will evaluate BET surface area of nanopowders, oxygen adsorption studies on nanopowders of cathode materials, oxygen reduction kinetics of cathode nanopowders by thermogravimetric analysis and mass spectroscopy (TGA-MS). Finally we will fabricate single cell SOFC and test it in the laboratory environment to assess the materials compatibility and power efficiency over the range of temperature of operation of an IT-SOFC for different compositions of the cathode material. This systematic study will enable us to identify and recommend a few of the compositions with optimum physico-chemical and electrochemical properties for further investigation.