Solid Oxide Cells With Ultra-thin CGO Barrier Layer And Nanostructured Electrodes

Solid oxide cell(SOC)is a third-generation fuel cell that combines solid oxide fuel cell(SOFC)and solid oxide electrolysis cell(SOEC).The operation temperature is 600～800℃,which can not only realize efficient,clean and large-scale preparation of hydrogen,but also effectively absorb surplus electricity from renewable energy sources such as wind power,photoelectric power,hydropower,etc.,to meet the future large-scale energy storage demand of power system containing a high proportion of renewable energy.Because the cells operating temperature is too high,the material selection cost of the reactor connector is high,the thermal expansion coefficient of each component material of the cells is difficult to match,and the long-term operation degradation is serious.Therefore,SOC is developing towards moderate and low temperature.Firstly,the preparation of a symmetric cells LSC-CGO-YSZ | YSZ | YSZ-CGOLSC,the cells electrodes complete prepared by infiltrated method,based on the cell morphology characterization and performance test,verify the infiltrated method for electrode has the characteristics of highly active,low polarization resistance,and in the low temperature has a better performance compared with the same type cells.On the basis of the symmetric cells developed a based on the traditional Ni/YSZ fuel electrode support type cells:Ni/YSZ | YSZ | YSZ-CGO-LSC.Innovatively,the oxygen electrode was based on YSZ porous skeleton,on which CGO nanoparticles were grown in situ by hydrothermal method as the barrier layer.The thickness of the barrier layer was only 10100nm,and then LSC nanoparticles were prepared on the barrier layer by infiltrated method as the oxygen electrode catalyst.The cells has higher electrode activity than traditional Ni/YSZ cells,so the Area specific resistance(ASR)is low.The performance and stability of the Ni/YSZ |YSZ| YSZ-CGO-LSC cell were studied through the following experiments:the fuel electrode of the cell was supplied with 97%H2-3%H2O,while the oxygen electrode was supplied with air.The cell was tested in SOFC mode electrochemically,and at 550 ℃ the power density reached 0.2W/cm2,which exceeded most of the reported cells of the same type.Under an applied current of 1 A/cm2,the stability test was conducted at 600℃ for 238h,with a degradation rate of 0.32 V/kh.Analysis of the DRT and Nyquist plots showed that the degradation mainly occurred due to gas transport barriers on the electrode surface,while the charge transfer and ion conductivity of the oxygen electrode were not affected,which supported the notion that the CGO blocking layer provided sufficient protection to YSZ from adverse reactions with LSC.Furthermore,the cell was tested in SOEC mode electrochemically under an atmosphere of 80%H2-20%H2O and air.At 550℃,the current density corresponding to 1.5V was-0.14 A/cm2.Under an applied current of-0.4A/cm2,the stability test was conducted at 650℃ for 311h,with a degradation rate of 0.64 V/kh.By comparing the SEM images of the fuel electrode before and after the stability test,it was observed that Ni underwent coarsening and migration during the stability test,and analysis of the DRT and Nyquist plots showed that the degradation mainly concentrated on the fuel electrode.Through these experiments,it was demonstrated that the ultra-thin CGO blocking layer and the nano-electrode significantly improved the performance and stability of the cell,providing a new approach for low-temperature conversion in traditional Ni/YSZ cells.