Novel F-doped LSCF As Oxygen Electrode For Reversible Solid Oxide Cell

Oxygen electrodes with high redox activity are one of the prerequisites for the efficient and stable operation of solid oxide cell(solid oxide fuel cell and solid oxide electrolyzer cell).However,at present,the oxygen reduction characteristics of commonly used LSCF oxygen electrode can not meet the practical application.To solve this problem,this paper aims to promote the commercialization of SOFC by increasing the oxygen vacancy concentration and surface reaction kinetics of perovskite materials by doping an appropriate amount of fluorine anions in LSCF.La_0.6Sr_0.4Co_0.2Fe_0.8O_3-?_-xF_x(LSCFF_x)(0<x<0.2)perovskite powders were successfully synthesizd by sol-gel method,and crystal structure of the obtained LSCFFx powders was determined using X-ray diffractormeter(XRD)and Raman spectra after calcined at 800 ^oC.The coefficient of thermal expansion of each electrode materials were tested by thermal dilatometer,and the electric conductivities of the oxygen electrode materials were measured by Keithley 2440 digital sourcemeter,and area specific resistance(ASRs)of the LSCFF_x/GDC/LSCFF_x(0<x<0.1)symmetric cell were measured by the electrochemical workstation(Zahner IM6ex,Germany).The test results show that maximum conductivity of LSCFF_0.05(423 S cm^-1)and LSCFF_0.1(338 S cm^-1)are lower than that of LSCF(475 S cm^-1)at 650 ^oC.The area specific resistances(ASRs)of the symmetric cell LSCFF_0.05/GDC/LSCFF_0.05 is only 0.015?·cm²(ASR_LSCF=0.017?·cm²),while ASRs of LSCFF_0.1/GDC/LSCFF_0.1 is 0.09?·cm².Single cell LSCFF_x(0<x<0.1)/GDC/YSZ/Ni-YSZ were prepared by spray method,which electrochemical performance were tested using hydrogen as the fuel and air as the oxidant.The best output was obtained at 850 ^oC using the LSCFF_0.05 as oxygen electrode,and the maximum power density was 1005 m W·cm^-2(P_LSCF=754 m W·cm^-2).The long-term stability test at a constant voltage of 0.7 V and 750 ^oC up to 110 h for single cell LSCFF_0.05/GDC/YSZ/Ni-YSZ,and the performance was still higher than LSCF.Therefore,LSCFF_0.05 is a potential high performance oxygen electrode material for SOFC.Based on the above research results,the high temperature stem electrolysis(HTSE)experiment of single cell LSCFF_0.05/GDC/YSZ/Ni-YSZ was conducted using water vapor as raw material.The results show that the total resistance of LSCFF_0.05/GDC/YSZ/Ni-YSZ electrolytic cell was only 0.15?·cm² at 850 ^oC and 1.5 V electrolytic voltage,which hydrogen production rate was 15.14 m L·min^-1·cm^-2 and electrolytic efficiency reached 30.65%.It is further proved that F-anion doped LSCF can provide a good oxygen electrode material for SOEC producting hydrogen.