Fuel Cell Bi_0.5Sr_0.5FeO_3-?-based Cathode Material Structure Control And Electrocatalytic Performance

At present,solid oxide fuel cells?SOFC?have become new energy storage devices with the advantages of low pollution and high conversion efficiency.Nevertheless,the high operating temperature of traditional solid oxide fuel cells results in many problems,such as the challenges of materials stability,reducing the cycle life of the cell and affecting its commercial value.The cathode materials are the most important part of fuel cell components.Hence,the development of SOFC cathode materials with high catalytic activity and high stability has become a research hotspot for scholars at home and abroad.In this paper,Bi_0.5Sr_0.5Fe_1-xTa_xO_3-??BSFTax,x=0-0.10?,Bi_0.5Sr_0.5Fe_1-xTi_xO_3-??BSFTix,x=0.05-0.20?,Bi_0.5Sr_0.5Fe_1-xZr_xO_3-??BSFZrx,x=0.05-0.15?three B-site doping single perovskite cathode material are perpared by traditional high temperature solid state reaction method.The main research contents and experimental results of this paper are as follows:1.BSFTax oxides are a type of cathode material with a simple cubic perovskite phase.The BSFTax cathode material have good chemical compatibility with electrolyte(Ce_0.9Gd_0.1O_1.95,CGO).At 700°C,the polarization resistance?R_p?of BSFTa0.10 cathode is 0.128?cm²and the output power density of the full cell with BSFTa0.10 as the cathode is as high as 1.36 W cm^-2.The investigation of the oxygen reduction reaction mechanism found that the major rate-determining step for BSFTa0.10electrode is the molecular oxygen adsorption-dissociation process.In addition,the studied found that the average metal bond energy of the material gradually increased with the increase of highly acidic Ta content,suggesting that the BSFTa0.10 material has excellent CO₂resistance.2.The prepared BSFTix material and electrolyte has excellent chemical compatibility.According to the characteristic capacitance and relaxation frequency,it can be analyzed that oxygen adsorption-dissociation process is the major rate control step on the BSFTi0.15 electrode.At 700°C,the symmetrical half-cell with BSFTi0.15as the cathode exhibite a polarization resistance of 0.085?cm²and the output power density of the full cell assembled with BSFTi0.15 as the cathode is as high as 1.41 W cm^-2.When the cathode voltage is 0.422 V,the power density of the cell is stable at around 1.41 W cm^-2over a period of 100 h,indicating that the cathode material has good long-term stability during the test period.The study of CO₂tolerance illustrate that Ti-doped BSFTix materials have higher CO₂tolerance.3.In this chapter,BSFZrx cathode materials are prepared by an introduction of higher valence Zr cation on Fe sites.At 700°C,the R_pof BSFZr0.10 is 0.118?cm²and the power density of the cell with BSFZr0.10 as the cathode reaches 1.17 W cm^-2.The analysis of impedance spectra under different oxygen partial pressures found that the oxygen adsorption-dissociation and charge transport processes are the control steps on the BSFZr0.10 electrode.The doping of highly acidic Zr and a relatively large ABE value improve the CO₂durability and chemical stability of the BSFZr0.10 material.In this experiment,high-valence Ta,Ti and Zr metals doping are used to adjust and control the electrochemical performance of the SOFC cathode.It was found that the doping of high-valence metals at the B-site can not only enhance the electrochemical performance of the material,but improve the chemical stability of the material.Bi_0.5Sr_0.5Fe O_3-?-based perovskite materials are a kind of IT-SOFC cathode materials with promising applications.