The Synthesis And Characterization Of The Composite PrSrFe_xCo_1-xO₄-Pr_0.4Sr_0.6Fe_xCo_1-xO₃ Cathode In SOFC

Currently,the Intermediate Temperature Solid Oxide Fuel Cell?IT-SOFC?,which not only has the clean and efficient advantage,but also alleviate the performance degradation caused by high operation temperature,and improves the stability of the fuel cell,has attracted significant attention.However,as the operating temperature of the SOFC decreases,a series of adverse effects,such as the increased impedance of the electrode reaction and the reduced rate of cathodic oxygen reduction reaction,would occur.The development of cathode materials with higher electrocatalytic activity at lower temperature is the key to solve the above problems.And the composite cathode materials have attracted much attention because of their excellent comprehensive properties.In this paper,the PrSrFe_0.5Co_0.5O₄-PrSrFe_0.5Co_0.5O₃(PSFC_214-113)composite was prepared by the sol-gel method with F127 as the chelating agent and applied to the cathode of IT-SOFC.The PSFC_214-113 composite cathode is composed of the pervoskite Pr_0.4Sr_0.6Fe_0.5Co_0.5O₃(PSFC₁₁₃)material and PrSrFe_0.5Co_0.5O₄(PSFC₂₁₄)Ruddlesden-Popper?RP?phase material.The composites cathode were sintered at different temperat-ures,which structure and properties were studied.Through the XRD examination and its Rietveld refinement analysis of the PSFC_214-113 composite cathode,it's found that the PSFC₂₁₄ component has a tetragonal crystal structure with the space group I4/mmm and the PSFC₁₁₃ component has an orthorhombic crystal structure with the space group Pbnm.The results show that the conductivity of PSFC_214-113 sintered at 1000?can reach 330 S cm^-1 at350?.The PSFC_214-113 composite cathode has similar EIS value as the prepared PSFC₁₁₃cathode of 0.119?cm² at test temperature of 800?,but it avoids the disadvantage of that the EIS value increase rapidly as the temperature decrease,suggesting the better structure stability.The discharge power of the La_0.9Sr_0.1Ga_0.8Mg_0.2O_2.85?LSGM?supported cell and the anode-supported cell were 0.683 W cm^-2 and 0.864 W cm^-2,respectively.The polarization stability test and full cell durability test shows that the composite have good long-term stability.In this paper,a series of PrSrFe_xCo_1-xO₄–Pr_0.4Sr_0.6Fe_xCo_1-xO₃?x=0,0.25,0.5,0.75,1?composite cathode material with different Fe/Co ratios were successfully prepared by the sol-gel method.The effect of the x value on the phase structure and electrochemical properties was investigated.The results show that the five composites have higher pore structure and smaller particle size.The thermal expansion coefficient?TEC?and the conductivity increase with the increase of the Co content.The electrochemical impedance value decreases with the increase of the Co content.However,when the x value increases to0.75,the impedance will increase due to the increase of the thermal expansion coefficient.The composite cathode exhibits the best electrochemical performance at x=0.5,and its impedance is 0.119?cm² at 800?.As a result,the PSFC_214-113 is a potential IT-SOFC cathode material because of its high electrical conductivity,moderate thermal expansion coefficient and excellent electrochemical properties.