| The ionic conductivity and stability of cathode and interlayer between electodes and electrolyte play a significant role in in solid state oxide fuel cells(SOFC) operation. One effective way to increase the output power density and energy efficiency of SOFC is to enhance the performance of these materials. In this paper,(1) we prepared nano-composite materials by adding the second phase salt LiNaSO4 to Ce0.8Sm0.2O1.9(SDC). The composites significantly increase the ionic conductivity of SDC by one order of magnitude as well as single cell performance when used as interlayer. The mechanism of the function of the composites is discussed.(2) The perovskite-like Sr & Co free cathode materials Pr2NiO4+δ were modified by Cu and Fe to obtain Pr2Ni1- xMxO4+δ(M=Cu,Fe; x= 0.05,0.1,0.2). The modified materials markedly enhanced the electrochemical prperties and chrome tolerance ablility of Pr2NiO4+δ.Novel nano-composites samarium doped ceria(SDC)-x LiNaSO4(wt%) have been prepared and characterized as high ionic conductive functional layer of ITSOFC. A set of techniques including thermal gravity(TG), X-ray diffraction(XRD), FT-IR, AC conductivity and I-V measurements of single cellshave been employed to characterize the SDC and thecomposites.The influence of mass ratio(x) of SDC and LiNaSO4 on crystal phases, defect concentration and conductivity has been investigated. The optimum mass ratio x=20 wt% exhibits the highest conductivity at testing temperatures, reaching0.22, 0.26, and 0.35 S·cm-1 at 550, 600 and 700 oC, respectively,which are significantly higher than the values of SDC. The peak power density of the single cell us ing SDC-20wt%LiNaSO4as interlayer is227, 390 and 876mW/cm2 at 500, 600, and 700 oC, respectively, which is significantly improved comparing with the performanc e the cell using SDC as the interlayer.Furthermore, both cells display thermal stability within 50 hrs. The results indicate that SDC-20%LiNaSO4is a potential high ionic conductive and thermally stable material as the functional layer of ITSOFC.The A2BO4 type materials Pr2Ni1- xCuxO4+δ(x=0, 0.05,0.1,0.2)and Pr2Ni1- xFexO4+δ( x=0.05,0.1) are successfully synthesized. A set of techniques including thermal gravity(TG), X-ray diffraction(XRD), AC conductivity and I-V measurements of single cells have been employed to characterize these materials.The results show that all samples have formed the single phase at 1200 oC. And the doping of Cu decreases the calcined temperature while the doping of Fe increases the temperature. Moreover, the Cu and Fe doping both enhance the output powerdensity of single cells. Among the Cu doping materials, Pr2Ni0.8Cu0.2O4+δ has the lowest polarization res istance and the highest power density. Set the values at 700 oC as examples, the polarization resisitance of Pr2Ni0.8Cu0.2O4+δ is 0.137Ω cm2 and the peak power sensity is 725mW/cm2 which are half and two times the values of Pr2NiO4+δ, respectively. Pr2Ni0.9Fe0.1O4+δ performs the best among the Fe doping samples with the power density of 1.12W/cm2 and 725mW/cm2 at 800 oC and 700 oC, respectively. The single cell performances are significantly enhanced comparing to that based on Pr2NiO4+δ(184.9 mW/cm2 at 700oC).The 100 h thermodynamic stability tests show that Pr2NiO4+δ and Pr2Ni0.8Cu0.2O4+δexibit the remarkable stability and the stability of Pr2Ni0.9Fe0.1O4+δ needs to be improved. The data of chrome poisoning tolerance show all samples react with chrome oxide and the properties of symmetry cells are decreased. |
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