新型中温固体氧化物燃料电池阴极材料Fe掺杂Sm_(0.5)Sr_(0.5)CoO_3性能研究

A Novel Cathode Material of Iron-doping Sm_(0.5)Sr_(0.5)CoO_3 for Solid Oxide Fuel Cell

本文系统研究了新型中温固体氧化物燃料电池(IT-SOFC)阴极材料Sm0.5Sr0.5Co1-xFexO3-δ(SSCF)的晶体结构、热膨胀系数、导电率及电化学性能。固相合成的Sm0.5Sr0.5Co1-xFexO3-δ化合物均为单相材料,随着掺Fe量的不同,SSCF的晶体结构发生变化,在0≤x≤0.4时,SSCF为正交晶系钙钛矿结构,在0.5≤x≤0.9时,SSCF为立方晶系钙钛矿结构。Fe掺杂可以显著的改善Sm0.5Sr0.5CoO3的热膨胀系数,随着Fe含量的增加,热膨胀系数减小。在800℃下,SSCF导电率均大于100S·cm-1。随着Fe含量的增加,极化电阻增大;含量x=0.4时,极化电阻达到最大值;之后,随Fe含量的增加,极化电阻减小,在700～800℃时,Sm0.5Sr0.5Co0.2Fe0.8O3-δ表现出了良好的氧催化活性。

Crystal structure, thermal expansion coefficient, electrical conductivity and cathodic polarization of compositions in the system Sm0.5Sr0.5Co1-xFexO3-δ with 0 ≤x≤0.9 were studied as a function of Co/Fe ratio and temperature in air. Two phases, an orthorhombic symmetry for 0 ≤x ≤ 0.4 and a cubic symmetry for 0.5 ≤x≤0.9, were observed in samples of Sm0.5Sr0.5Co1-xFexO3-δ at room temperature. The adjustment of thermal expansion coefficient （TEC） to electrolyte, which is one of the main problems of SSC, could be achieved to lower TEC values with more Fe substitution. High electrical conductivity above 100 S ·cm^-1 at 800 %： was obtained for all specimens, so they could be good conductors as cathodes of IT-SOFC. The polarization behavior of SSCF as a function of Fe content was evaluated by means of AC impedance using LSGM electrolyte. It is found that the Area Specific Resistance （ASR） of SSCF increases as the amount of substitution of Fe for Co increases. When the amount of Fe reaches to 0.4, the highest ASR is obtained and then the resistance starts decreasing. The electrode with a composition of Sm0.5Sr0.5Co0.2Fe0.8O3-δ shows high catalytic activity for oxygen reduction operating at temperature ranging from 700 to 800℃.