Study On The Performance Of Iron, Cobalt And Nickel Oxide Nano Powder As Anode Catalysts For S/O₂SOFC

Sulfur-oxygen solid oxide fuel cell (SOFC) is a new kind of fuel cell using sulfur vapor orSO2as fuel gas, SO3as oxidation product. In this paper, high temperature (HT)-SOFC wasassembled by Na2SO4(25wt%)-YSZ as composite electrolyte and α-Fe2O3、Fe3O4、Co3O4andNiO those four kinds of iron, cobalt and nickel oxide nano powder as anode materials. Theopen-circuit voltage variation with temperature by using sulfur vapor and SO2as the fuel gasrespectively were studied and finally determined the optimum working temperature of cell inadopting different anode catalysts. Then, under the optimum working temperature, we accessedthe variable resistance to assemble the circuit and tested the output voltage and output current asthe change of external resistance and analyzed the test result.The powder of La0.7Sr0.3MnO3was prepared by sol-gel method. The powder which hasbeen used as SOFC cathode material was characterized by the techniques of X-ray diffraction(XRD) and Transmission electron microscope (TEM). And the result of XRD analysis showedthat the diffraction peak distribution of powder was narrow, with strong intensity and highpurity without any abnormal peak; meanwhile the result of TEM image demonstrated that theaverage particle size of the prepared LSM powder was about200nm with homogenousdistribution.The high temperature composite electrolyte substrate Na2SO4(25wt%)-YSZ was preparedby dry-press method. Then put the dried composite electrolyte substrate into the box-typeresistance furnace and roasted in the optimized sintering temperatures heating up to1350℃. Byadopting the coating method, coated the two sides of sintered electrolyte substrate withelectrode coating. Thereinto, to assemble a sulfur-oxygen SOFC, one side of the electrolytesubstrate was coated with the iron, cobalt and nickel oxide nano powder as anode and the otherside was coated with La0.7Sr0.3MnO3as cathode. After sintering, the electrolyte substrate wasassembled with Al2O3-tube (acted as support) to obtain sulfur-oxygen SOFC power generationsystem. The variation tendency of open-circuit voltage (OCV) was as follows: Co3O4＞NiO＞Fe3O4＞α-Fe2O3. when using iron, cobalt and nickel oxide nano powder as anode material inthe sulfur vapor single cell. The maximum OCV of815mV was generated at the best workingtemperature of780℃when Co3O4was used as anode material in the sulfur vapor single cell.Current density of146.53mA·cm-2was generated when resistance was turned to0. Themaximum output power density of37.76mW·cm-2and the output current density of90.14mA·cm-2were generated when the resistance was turned to90. The maximum OCV of372mV were generated at the best working temperature690℃when Co3O4was used as anode material in the SO2single cell and the variation tendency of open-circuit voltage (OCV) was still as follows:Co3O4>NiO>Fe3O4>a-Fe2O3. The current density of44.11mA·cm-2was generated when the resistance was turned to0Ω. The maximum output power density of7.87mW·cm-2and the output current density of18.81mA·cm-2were generated when the resistance was turned to100Ω. Experiments proved that CO3O4was the best anode material among all the anode materials mentioned above whether to use the sulfur vapor or SO2as fuel.