Intermediate Temperature Solid Oxide Fuel Cell Preparation And Performance Optimization Of BaCo_0.7Fe_0.3O_3-?-base Cathode Materials

The solid oxide fuel cell?SOFC?is widely used as a third-generation fuel cell because of its high efficiency and environmental friendliness.In order to expand the selectivity of battery materials and reduce costs,it is necessary to lower the operating temperature.However,lowering the operating temperature will cause the increase in the ohmic resistance of the electrolyte and the polarization resistance of the electrode.Therefore,it is very important for SOFC to find a material with strong catalytic activity at low and medium temperatures.In this paper,the scandium doped BaCo_0.7Fe_0.3-xSc_xO_3-??x=0,0.04,0.08,0.1,0.12??BCFSc_x?cathode material was prepared by solid-phase method.Their properties were characterized by the X-ray diffractometer,AC impedance tester,scanning electron microscope,electrochemical workstation and other test instruments.The results show that the BCFSc cathode material exhibits a cubic perovskite phase structure when BCFSc_0.1.1 cathode material with a Sc doping ratio of 0.1 is sintered at1000?for 10 hours.The polarization resistance value is the smallest,and the minimum value is 0.2801?·cm² when its symmetrical half-cell is sintered at 950?for 3 hours,suggesting that the BCFSc cathode material has excellent electrochemical performance.Using BCFSc as the cathode,Ni_0.9Cu_0.1O_x-SDC as the anode,the maximum output power density of the Ni_0.9Cu_0.1O_x-SDC/SDC/BCFSc single cell supported by the SDC electrolyte at 800?test temperature is 305.96mW/cm².The polarization impedance of the single cell is 0.1328?·cm².The SEM results show that the cathode particles are loose and porous,and the porosity is too large,resulting in a smaller three-phase interface with the SDC electrolyte,which reduces the electrochemical performance of the single cell.In order to obtain a higher performance cathode material,we prepared the BCFSc-SDC composite cathode material by mechanical mixing method.The experimental results show the smallest polarization resistance value when the doping ratio of BCFSc to SDC is 7:3 and the BCFSc-30%SDC composite cathode is sintered at 900?for 3 hours.The minimum value is 0.11895?·cm².With BCFSc-SDC as the cathode,Ni_0.9Cu_0.1 O_x-SDC as the anode,the maximum output power density of the Ni_0.9Cu_0.1O_x-SDC/SDC/BaCo_0.7Fe_0.2Sc_0.1O_3-?-SDC composite single cell supported by SDC electrolyte at 800?test temperature is 521.28 mW/cm²,which is higher than the uncombined single cell,and the overall increase is 70.38%.The polarization resistance value is 0.0855?·cm²,which is also far below the impedance of the cathode of the non-composite SDC?0.1328?·cm²?.This suggests that the mechanical mixing method can improve the performance of the cathode material.In addition,a praseodymium ion-impregnated BaCo_0.7Fe_0.2Sc_0.1O_3-?-Pr?BCFSc-Pr?composite cathode was prepared by ion impregnation.The results show that the symmetric half-cell made of BCFSc-Pr composite cathode impregnated three times has the smallest polarization resistance value after sintering at 800?for 3hours.The minimum value is 0.0886?·cm²,which is far lower than the impedance value of the half-cell made of single-phase BCFSc cathode.The maximum output power density of BCFSc-Pr as cathode,Ni_0.9Cu_0.1O_x-SDC as anode,SDC electrolyte supported Ni_0.9Cu_0.1O_x-SDC/SDC/BCFSc-Pr impregnated single cell at 750?test temperature is 364.08 mW/cm².The polarization impedance value is 0.1149?·cm².SEM results showed that after the impregnation,the surface of the cathode was found to be broken,therefore the contact area between the cathode and the SDC electrolyte becomes smaller,the three-phase interface between oxygen and cathode becomes smaller,which results in the lower output power of single battery.