Investigation On Stability Of Lanthanum Ferrite Fuel Electrode For Solid Oxide Cells

The increasing demand for energy and the gradual depletion of fossil energy drive the rapid development of renewable energy sources and technologies.Solid oxide cell（SOC）is an efficient and environmentally friendly energy conversion and storage technology,which can realize the conversion and storage of renewable and clean energy.SOC has broad commercial application prospects.More and more research and industrial development feedback have proved that the degradation of fuel electrode significantly impacts the long-term life operation of SOC.Therefore,it is very important to develop stable fuel electrode materials,among which perovskite materials have gained wide attention.This paper aims to improve the stability of lanthanum ferrate perovskite oxide as the fuel electrode material for SOC.The first part briefly introduces the importance of SOC,especially in the current situation of energy development in China.Then,the basic working principle,structure composition,and key materials are described for SOC.And the crystal structure,physical and chemical properties of lanthanum ferrate perovskite materials,as well as the current research status of lanthanum ferrated based materials as SOC fuel electrodes are introduced in detail.And finally,the purpose and subject of this paper are breifly summurized.The second part introduces the synthesis and characteristic methods of the powders and cells.In the third part,based on the perovskite structured La_0.6Sr_0.4FeO_3-δ ceramic,W and Zr are doped to the B-site using a combustion fabrication process,resulting in various components of La_0.6Sr_0.4Fe_1-xN_xO_3-δ（N=W,Zr;x=0,0.05,0.1）.The parent phase La_0.6Sr_0.4FeO_3-δ is not stable,partially changing to RP-structureand forming metal Fe.XRD results show that doping W or Zr at the B-site can improve the stability of phase structure.La_0.6Sr_0.4Fe_0.9W_0.1O_3-δ、La_0.6Sr_0.4Fe_0.9W_0.1O_3-δ stay provskite structure after the treatment at 800℃ for 5 hour under humudied hydrogen atmosphere.at In single cell tests,La_0.6Sr_0.4Fe_0.9W_0.1O_3-δ、La_0.6Sr_0.4Fe_0.9W_0.1O_3-δ materials are evaluated as the fuel electrode of solid oxide fuel cell,The peak power densities at 800℃ are 0.70 and 0.69 W cm^-2,respectively.For comparison,the cell with La_0.6Sr_0.4FeO_3-δ fuel electrode shows a density with 0.76 W cm^-2.However,its performance decreases to 0.33 W cm^-2 after 40 hours.The short-term operation results show that the stability of La_0.6Sr_0.4Fe_0.9W_0.1O_3-δ phase is significantly improved compared with La_0.6Sr_0.4FeO_3-δphase.In the last part,Ca is introduced to its A-site to stabilize the perovskite structure.While doping Ca is demonstrated to be achievable in the full compositional range,only La_0.6Sr_0.4Fe_0.8Mn_0.2O_3-δ is stable in hydrogen atmosphere at 800℃.The doping improves the thermal expansion compatibility with electrolyte,and increases the oxygen vacancy concentration and content of adsorbed oxygen species,but reduces the electronic conductivity.Meanwhile,the doping increases the electrochemical performance as the fuel electrode,such as reducing the interfacial polarization resistance by 38%to 0.13Ω cm² at 800℃,increases the peak power density by 17%to 1.05 W cm^-2 at 800℃ when operated in fuel cell mode with humidified hydrogen as the fuel,In addition,much stable output is observed in the short-term durability test。A high current density of 1.89 A cm^-2 was shown at 800℃ when evaluated in electrolysis cell mode to electrolyze pure CO2.