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

固体氧化物燃料电池(SOFC)可以被认为是煤、天然气和生物质等传统发电能源的替代能源。在SOFC中，氢等可再生燃料在高温至中温固态电化学电池中转换为电能，电池运行温度通常在500至900摄氏度之间。燃料电池技术解决了导致全球变暖的重要温室气体排放问题，如二氧化碳和甲烷。在生产能源方面，SOFC不仅可能满足不断增长的世界人口的需求，而且还将是一种更清洁、环境友好的能源来源。SOFC技术可以解决未来的能源三难问题(能源安全、可持续性和可负担性)，如果在当前时代不加以解决和忽视，下一代可能会面临这些问题。SOFC的好处是以70%以上的高效率运行。利兹研究小组已经在目前正在进行的一项博士研究项目中开发了新的快速氧化物离子导电固体电解质。鉴于多孔镍基复合阳极已经成熟，我们打算致力于开发新的阴极材料，将其与已经开发的固体电解液和已建立的阳极相结合，用于在600-800℃之间运行的IT-SOFC。高比表面积的稀土(Re)共掺LSCF纳米粉末(RexLa0.6-xSr0.4Co0.8Fe0.203)将用于开发新型阴极。正极材料的开发将通过由利兹大学研究小组在之前的三个博士项目中开发的利兹海藻酸盐法(LAP)通过RexLa0.6-xSr0.4Co0.8Fe0.2O3纳米粉末合成来系统地进行。这是一种由利兹大学的研究人员开发的藻酸盐介导的阳离子交换方法，有可能以相对容易和低成本的方式生产出持续的高纯度单相复合氧化物纳米粉末。通过海藻酸盐介导离子交换过程，将采用一系列实验技术来测定高比表面积再掺杂LSCF正极材料的化学、物理、热、磁、结构、催化、电化学和电学性质。然后，将得到的阴极纳米粉末和阴极/电解质复合材料单轴压制成圆盘，并在不同的温度范围内烧结，以研究选定温度范围内材料的化学兼容性。通过差示扫描量热仪(DSC-TGA)、热膨胀热重分析(DSC-TGA)、Brunauer-Emmett-Teller(BET)、X-射线荧光(XRF)等测试手段对其热性能、物化性能进行表征；通过X射线衍射仪(X射线衍射仪)、高温X射线衍射仪、扫描电子显微镜、透射电子显微镜和激光拉曼光谱等测试手段对材料的磁性和结构性能进行表征。电学性能的评估方法包括交流阻抗谱，通过旋涂或脉冲激光沉积(PLD)在多孔阴极上涂覆固体电解质制成的半电池，通过测量开路电位来评估半电池的电位，通过交流阻抗谱来评估半电池的面积比电阻。为了考虑阴极材料的氧还原能力，我们将评估纳米粉末的BET比表面积，研究阴极材料纳米粉末的吸氧性能，并通过热重分析和质谱分析(TGA-MS)来研究阴极纳米粉末的氧还原动力学。最后，我们将制作单电池SOFC并在实验室环境中进行测试，以评估IT-SOFC在不同阴极材料组成的工作温度范围内的材料兼容性和功率效率。这一系统的研究将使我们能够确定并推荐几个具有最佳物理化学和电化学性能的组合物用于进一步的研究。

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 LaserRaman 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.