Preparation And Structure Activity Relationship Of The Electrode Materials For Symmetrical Solid Oxide Fuel Cells

In the context of hydrogen and dual-carbon strategies,Solid oxide fuel cell（SOFC）is favored by researchers because of its fuel adaptability,high energy conversion efficiency and clean and pollution-free characteristics.The development and utilization of new anode materials are of practical significance because the traditional solid oxide fuel cells use nickel-based materials as anodes,which have higher cost and energy consumption.In this paper,a symmetrical solid oxide fuel cell（SSOFC）with the same electrode-electrolyte interface was investigated to simplify the cell preparation process and reduce the incompatibility of electrodes and electrolytes.The main content is to select Sr Fe-based perovskite material with stable structure in redox atmosphere and good ionic-electron mixed conductance as the research substrate,to evaluate the electrochemical performance as electrode materials for SSOFC.Gd_0.6Sr_0.4Fe O₃（GSF）and Pr_1-xSr_xFe O₃（PSF）composite electrode materials were prepared by A-site doping of La series elements,the effects of different composition and proportion of A-site doping on the performance of the cell are discussed and analyzed,Pr_0.6Sr_0.4Fe_0.8Cu_0.2O₃（PSFCu）and GSF-Co₃O₄composite electrode materials were prepared.The doping methods and electrode properties were analyzed by testing the structure and electrochemical properties.Finally,the relationship between composition,structure and electrochemical properties of Sr Fe-based electrode materials was discussed.The main conclusions are as follows:The layer oxide Sr₃Fe₂O₇（SFO）has high oxygen exchange coefficient.The optimal sintering condition is 1300℃-4 h by studying the effect of different sintering temperature on the electrochemical properties of the slurry.The SFO|GDC|YSZ|GDC|SFO symmetric cell was constructed.After 50 h long-term stability test with hydrogen as fuel,the cell voltage was stable and showed good catalytic long-term stability,which was suitable for SSOFC electrode material.In order to make full use of the advantages of the perovskite material Gd_0.6Sr_0.4Fe O_3-δ（GSF）,the Gd_0.6Sr_0.4Fe O_3-δ-Co₃O₄（GSF-Co₃O₄）composite electrode was prepared by using Co₃O₄modifier.Experimentally,the structure-activity relationship of different mass ratios was evaluated,and the results showed that the minimal polarization of 70%GSF and 30%Co₃O₄.The maximum power density of SSOFC with Co₃O₄was increased from 244.6 m W/cm²to 301.8 m W/cm²,and the associated polarization resistance was reduced from 0.62Ω·cm²to 0.49Ω·cm²at800℃.In addition,the SSOFC of the GSF-Co₃O₄composite electrode exhibited excellent stable performance after 100 h operation.The results showed that GSF-Co₃O₄is a promising SSOFC symmetrical electrode material.In order to improve the oxygen ion transport performance of the electrode material,Pr_1-xSr_xFe O₃（PSF）electrode with interstitial oxygen conductivity was prepared by in-situ forming method.And it was assembled into SSOFC electrode to test its electrochemical properties.The results showed that the in-situ dissolution process of various Sr content is different.And the formation of RP-type layered structure in the reducing atmosphere can accelerate the oxygen ion transfer rate,resulting in the polarization resistance（Rp）value increasing from 0.36Ω·cm²to 0.16Ω·cm²at 800℃,and the power density increasing from 418 m W/cm²to 502 m W/cm².Therefore,introducing a quasi-symmetrical oxide fuel cell by introducing an interstitial oxygen conduction mechanism is a potential method of changing the structure and improving performance.In order to increase the concentration of oxygen vacancies at the electrode and to form more surface-active sites to promote the catalytic dissociation of hydrogen,copper（Cu）is used to dope the perovskite-type Pr_0.6Sr_0.4Fe O₃oxide material at the B-site,and evaluate as the electrode material for SSOFC.The results show that PSFCu has good structural stability under the reducing atmosphere.Its maximum conductivity is 253 S·cm^-1.The polarization resistance under air and hydrogen atmospheres is 0.21Ω·cm²and 0.48Ω·cm².And the maximum power density of single cell is 378 m W/cm²,which can meet the basic requirements of SSOFC electrode materials.Comprehensively comparing the four Sr Fe based perovskite electrode materials prepared above,the electrochemical performance of the symmetrical cell prepared has been improved.The results indicate that a series of doping modifications or composites of Sr Fe based perovskite materials can improve the catalytic performance of the electrode,thereby improving the electrochemical performance of the cell.Often the doping of low-valent metal ions with high-valent metal ions creates a large number of oxygen vacancies,providing an additional pathway for oxygen transport.High valence metal ions doped with low valence metal ions will interact with the surrounding lattice,promote the adsorption and dissociation process of fuel,and ultimately improve the electrochemical performance of the cell.For composite,it can broaden the three-phase interface,increase electrochemical reaction sites,and improve electrochemical performance.Figure[76]Table[6]Reference[185]...