Preparation And Properties Of Symmetrical Solid Oxide Fuel Cell Electrode Materials

Solid oxide fuel cells（SOFCs）are electrochemical devices that convert chemical energy directly into electric energy through electrochemical reactions.SOFCs have some advantages,such as of high energy conversion rate,fuel adaptability and environmental friendliness.Nickel-based ceramics are widely used in anode materials because of their good chemical stability and conductivity in oxidation and reduction atmospheres.However,when hydrocarbons are used as fuel,the nickel-based anode will cause carbon deposition and sulfur poisoning,which will seriously degrade the battery performance.Symmetrical solid oxide fuel cells（SSOFCs）,which use the same material as the cathode and anode,which solve effectively the problem of anode carbon and sulfur poisoning by switching gas paths,and simplifying the preparation process of cell.Due to the stable structure and low cost of perovskite materials,this thesis takes perovskite materials as the research object to explore the electrode materials suitable for use as SSOFCs.The main contents are as follows:1.PrBa_0.5Sr_0.5Fe₂O_5+δ（PBSF）was obtained by doping Pr Ba Fe₂O_5+δ（PBF）with Sr as the electrode layer and La_0.8Sr_0.2Ga_0.83Mg_0.17O_3-δ（LSGM）as the electrolyte.A single cell of PBSF（PBF）/LSGM/PBSF（PBF）was fabricated by screen-printing method.The main results as follow:First,Both PBF and PBSF have cubic perovskite structure in air environment,and PBSF has good phase stability and chemical compatibility with LSGM electrolyte in reducing atmosphere;Second,The electrode has good catalytic activity for oxygen reduction and hydrogen oxidation.At 700℃,the polarization resistance（R_p）in air and hydrogen reaches 0.052 and 1.57Ωcm²,respectively.R_pmaintains good stability in 120h air stability test.PBSF as a cathode has good stability and tolerance to carbon dioxide poisoning.Third,Using PBSF as symmetrical electrode,the maximum power density of hydrogen fuel is 1067m Wcm^-2and that of propane fuel is 535 MWcm^-2at 850℃in SOFCs mode.At 850℃,the current density of pure CO₂electrolysis at 1.3V is 2.02A cm^-2in SOEC mode.2.Sm and Nb doping Ba Fe O_3-δ（BF）to obtain Ba_0.95Sm_0.05Fe_0.9Nb_0.1O_3-δ（SBFN）,BF and SBFN as SSOFCs electrode layer,LSGM as electrolyte,SDC as buffer layer to fabricate the single cell SBFN（BF）/SDC/LSGM/SDC/SBFN（BF）.The main results as follow:First,SBFN has cubic perovskite structure in air environment,and SBFN shows acceptable phase stability in reducing atmosphere,and Fe nanoparticles are formed.Second,the SBFN electrode has good catalytic activity for oxygen reduction and hydrogen oxidation.At 800℃,the polarization resistance（R_p）in air and hydrogen reaches 0.021 and 0.2Ωcm²,respectively.Third,with SBFN as the symmetrical electrode,the maximum power density of hydrogen fuel is 657.2m Wcm^-2and that of propane fuel is 402.1 m Wcm^-2at 850℃in SOFCs mode.At 850℃,the current density of CO₂electrolysis is 0.914A cm^-2at 1.3V in SOEC mode.3.PrFeO_3-δwas doped with Sr and Y to obtain Pr_0.6Sr_0.4Fe_0.8Y_0.2O₃（PSFY）.PSFY was used as electrode layer and Sm_0.2Ce_0.8O_1.9（SDC）as electrolyte to construct a single cell of PSFY/SDC/PSFY.The test results show that:（1）PSFY has orthogonal perovskite structure in air environment,PSFY shows good phase stability in reducing atmosphere,and has good chemical compatibility with SDC electrolyte.（2）The electrode has good catalytic activity for oxygen reduction and hydrogen oxidation.At800℃,the polarization resistance（R_p）in air and hydrogen reaches 0.034 and0.91Ωcm²,respectively.（3）With PSFY as the symmetric electrode,the maximum power density of hydrogen fuel is 245.9m Wcm^-2at 800℃in SOFCs mode.