Study On A Novel Oxygen Electrode Material Of Solid Oxide Cell For CO₂-H₂O Co-electrolysis

Perovskite oxides(ABO3-?) are commonly used as oxygen electrode materials on solid oxide full cells/electrolysis cells(SOFC/SOEC), due to their mixed ion-electron conducting characteristics and low cost compared with precious metals. However, SrCoFeO(SCFO)-type materials with high oxygen permeability are limited due to their instability. To enhance the stability, SrCo0.8Fe0.1Ga0.1O3-?(SCFG) formed by the doped Ga into B site of SCFO.is proposed as potential oxygen electrode materials of SOFC/SOEC.SrCo0.8Fe0.1Ga0.1O3-?(SCFG) powder was successfully synthesized through an improved sol-gel method. The crystal structure and thermogravimetric characteristic were investigated by X-ray diffraction(XRD) and TG-DTA, respectively. The porosities and electronic conductivities were measured using Archimedes and DC four terminal methods. Area specific resistances(ASR) of SCFG at 500-750? have been investigated through electrochemical impedance spectroscopy(EIS). The cells with the configuration of SCFG/GDC/YSZ/Ni-YSZ were prepared by screen-printing technique, and tested with hydrogen as fuel and air as oxidant under SOFC mode. Meanwhile, the steam was electrolyzed to produce fuel hydrogen, and the syngas is obtained through H2O-CO2 co-electrolysis under SOEC mode.The results show that the electrical conductivity reaches up to 319.5S·cm-1 at 600?, which is higher than that of other traditional SOFC materials. The ASR of SCFG/GDC/SCFG symmetric cell is only 0.28 ?·cm2 at 750?, reaching the requirement of oxygen electrode on SOFC/SOEC. As the cathode material,the maximum power density is up to 945mW·cm-2 at 850? and the output keep a good stability during the operated 130 h at SOFC mode, indicating that SCFG has good performance as SOFC oxygen electrode, which is also the potential material of reversible SOFC/SOEC cells. The hydrogen production rate is 15.57 mL·min-1·cm-2 at 1.5V and 850?. H2 and CO were successfully produced via CO2-H2 O co-electrolysis method. The production rate of CO and conversion rate of CO2 was 8.6 m L·min-1·cm-2 and 4.6%, respectively, at the operating conditions of 30 vol.%CO2, 50 vol.%H2O, 10 vol.%H2, 10 vol.%N2 under 850? and 1.5V. The SOEC keeps stable without any degradation for 50 hours testing. These indicate that SCFG is a promising oxygen electrode material.