Preparation And The Electrochemical Performance Of Perovskite Based Oxide Material

Solid oxide fuel cell?SOFC?is a power generation device,which can convert the chemical fuels into electrical energy directly.In order to improve the electrochemical properties of SOFC,searching for cathode material with superior performance at intermediate-low temperature is an important direction of research.Perovskite oxide material becomes the focus of research because of its excellent conductivity and stability.In this paper,perovskite oxide material GdBaCo₂O_5+??GBCO?,SrFeO₃-??SFO?and different element doped oxide material were prepared by sol-gel process,and the electrochemical performances were analyzed.The details are as follows:Double perovskite cathode material GdBaCo₂O_5+??GBCO?and Sr-doped GdBa0.7Sr0.3Co₂O_5+??GBSCO?were synthesized by sol-gel method,and Ce0.9Gd0.1O2?GDC?was used as the electrolyte material.In order to optimize the electrochemical performance,GDC framework/GDC electrolyte and GBSCO-GDC composite carhode were prepared,and the weight ratio of GBSCO and GDC was 7:3.The cathode powders were painted on the electrolytes to make half-cells with different systems: GBCO/GDC,GBSCO/GDC,GBSCO-GDC/GDC,GBSCO/GDC framework/ GDC,and the electrochemical properties of half-cells were studied by 3-electrode method.The prepared powders,electrolyte pills and half-cells were characterized by thermogravimetric analysis?TG?,X-ray diffraction?XRD?and scanning electron microscope?SEM?techniques.After sintere at 950 ? for 2 h,GBCO and GBSCO cathode powders formed good cryatal structure.The XRD results exhibited that there were no reaction between the cathode material GBSCO and the electrolyte material GDC after sintered at 950 ? for 1 h.According to SEM images,GDC framework showed homogeneous porous structure and rougher surface compared to dense GDC pills.GBSCO cathode got better connection with GDC framework/GDC electrolyte,there were no widespread cracks and obvious holes between the junction of cathode and electrolyte.The electrochemical performances of half-cells at different temperatures were tested by electrochemical impedance spectroscopy?EIS?and liner sweep voltammetry?LSV?method.Results showed that Sr-doped cathode performed better electrochemical properties compared to GBCO cathode.According to the results at 700 ?,the area-specific interface resistance?RP?of GBSCO/GDC half-cell was 0.547 ?·cm²,much lower than that of GBCO/GDC.The current density of GBSCO/GDC half-cell was 0.219 A·cm-2 when the voltage was 0.8 V at 700 ?.The RP of GBSCO/GDC,GBSCO-GDC/GDC and GBSCO/GDC framework/GDC at 700 ? was 0.547 ?·cm²,0.166 ?·cm²,0.118 ?·cm²,and the current density was 0.209 A·cm-2,0.458 A·cm-2,0.763 A·cm-2,when the voltage was 0.8 V,respectively.The results showed that the electrochemical performances of half-cells were improved by the utilization of composite cathode and electrolyte framework.By comparison,GBSCO cathode material had the least influence of polarization on the surface of GDC framework,showed the best electrochemical properties.Co-based material possesses superior conductivity,but Co is nocuous and expensive,which restricts its development of commercial application in SOFC.Co-free based perovskite oxide becomes a kind of noteworthy cathode material because of high ionic-electronic conductivity,good stability and suitable price.In this paper,perovskite oxide material: SrFeO₃-??SFO?and Cu,Mo-doped SrFe_0.7Cu_0.2Mo_0.1O_3-??SFCM?were prepared as cathode materials,and the influence of the sintering temperature on phase structure,microstructure and electrochemical properties were studied.XRD results showed that SFO and SFCM cathode formed cubic perovskite structure after sintered at 800 ? for 2 h.After sintered at 800 ? for 1 h,there were no reaction between the cathode material SFCM and the electrolyte material GDC from the XRD results,and possessed excellent chemical compatibility at high temperature.The electrochemical properties of SFO/GDC,SFCM/GDC,SFCM-GDC/GDC and SFCM/GDC framework/GDC half-cells were tested under the same condition.The testing results showed that RP of SFO/GDC at 750 ? was 1.19 ?·cm²,much higher than that of SFCM/GDC,which was 0.492 ?·cm².The RP of SFCM/GDC at 700 ? was 1.06 ?·cm²,which were 0.7 ?·cm² and 0.77 ?·cm² higher than that of SFCM-GDC/GDC and SFCM/GDC framework/GDC half-cells,respectively.On the surface of GDC framework/GDC electrolyte,the current density of SFCM cathode reached 0.641 A·cm-2.The above results indicated that Cu,Mo-doped perovskite oxide optimized the electrochemical performances of cathode,and the electrochemical performances of half-cells were improved by the utilization of composite cathode and electrolyte frameworkThin film of SFCM cathode powders was prepared as working-electrode,the catalytic performance of SFCM toward the oxygen reduction reaction?ORR?were studied with 0.1 M KOH solution as electrolyte using the rotating disk electrode technique at room temperature.The oxygen reduction reaction?ORR?polarization curves and cyclic voltammetry?CV?curves were studied by 3-electrode method.The tested results showed that the limiting current density of ORR was increasing with the raise of rotation rate of SFCM working-electrode,and reached 4.42 mA/cm² at 2400 rpm.In the CV curves,there was a strong peak in the reduction process from positive potential to negative potential.The results showed that perovskite oxide material SFCM possessed favourable catalytic performance toward ORR.