| In this paper, three kinds of electrode materials refered to Ni0.7Co0.30(NC30), PrBaFe2O5+δ(PBFO), PrBaFe1.6Ni0.4O5+δ(PBFNO) and electrolyte material Sm0.2Ce0.8O1.9(SDC) were synthesized by the citric acid-nitrates self-propagating combustion method. The phase, microstructure of materials, thermal expansion coefficient(TEC), electrical conductivity, the output performance of cell and interfical Interfacial polarization resistance were respectively characterized by X-ray diffraction(XRD), scanning electron microscope (SEM), thermal analyzer, direct current four-probe technique and electrochemical workstation.In the second chapter, the reagents, instruments and characterization methods applied in related experimental were introduced.The electrochemical properties of novel cathode material Nio.7Co0.3O-Sm0.2Ce0.8O`.9 (NC3O-SDC) were systematically investigated in the third chapter. XRD results confirmed that pure cubic phase NC30 powders were obtained at 800℃ and also shown excellently chemical compatibility with SDC electrolyte at 1300℃. Different composite cathode powders were made by mixed NC3O with SDC at various ratio(NC30-xSDC, x=0,10,20,30,40,50,60 wt-%), a well ball-milled was needed. NC3O sample gained the maximum conductivity value as high as 0.432 S.cm-1 at 800℃.The thermal expansion curves shown that the SDC additions dramatically reduced the TEC values of cobalt-containing NC31 cathode material. Symmetric cells NC3O-xSDC|SDC|NC3O-xSDC impedance spectrum results demonstrated that 70%NC3O mixed with 30%SDC (NC3O-SDC30) composite cathode had a minimum polarization resistance of 0.071 Ω·cm2 at 800℃ in air. To prepare a anode-supported single cell with NC3O-SDC30 as the cathode (NiO-SDC|SDC| NC3O-SDC30) with humidified (～3%H2O), a maximum power density of 200 mW·cm-2 at 600℃ was obtained.A novel quasi-symmetric solid oxide fuel cell (Q-SSOFC) was proposed based on the design concept of symmetric solid oxide fuel cell (SSOFC) and verified through a series of performance testing and characterization in the fourth chapter of this paper. PrBaFe2O5+δ (PBFO) and PrBaFe1.6Ni0.4O5+δ(PBFNO, Fe is partially substituted by Ni) electrode material powders were prepared, To prepare SSOFC of PBFO| SDC| PBFO and PBFNO| SDC| PBFNO and the as-designed Q-SSOFC of PBFNO(anode)| SDC| PBFO(cathode) with SDC as the electrolyte. XRD results shown that PBFO and PBFNO were well crystalled at 900℃ and 1000℃, respectively, the excellently chemical stability of two kind of electrodes with SDC electrolyte was received after 1000℃ calcined. Compared to PBFO, the Ni-doped PBFNO sintering ceramic gained higher electrical conductivities in both air and H2, the TEC values also decreased from 19.5×0-6 K-1 to 16.6×10-6 K-1. electrochemical impedance spectra showed that both PBFO and PBFNO shown the lower polarization resistance in H2 than in air, but PBFO exhibited higher oxygen reduction reaction(ORR) activity than PBFNO and inversely in hydrogen oxidation reaction(HOR) activity. The results shown that the performance of a single cell Q-SSOFC obtained the highest power density of 120 mW·cm-2 and the lowest Ea of 105.6 kJ·mol-1 by comparison with other two SSOFC. SEM images confirmed that SDC electrolyte shown good thermal-mechanical matching with two kinds of electrode materials PBFO and PBFNO during the process of preparation and operation, suggesting that the process of heat treatment and cell preparation employed in this experiment was sucessful.The newly developed Q-SSOFC not have common SSOFC’s advantages, but further improve the electrochemical performance of SSOFC, which hold more promise for development of intermediate-low temperature. |
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