双钙钛矿Sr_(2)CoFeO_(5+δ)阴极材料的制备及其中温固体氧化物燃料电池性能研究

Double Perovskite Sr_(2)CoFeO_(5+δ):Preparation and Performance as Cathode Material for Intermediate-temperature Solid Oxide Fuel Cells

随着操作温度降低,中温固体氧化物燃料电池(IT-SOFCs)需要更高催化活性的阴极材料来提升电池性能。为此,本研究采用溶胶-凝胶法合成了双钙钛矿Sr_(2)CoFeO_(5+δ)(SCF)阴极材料,并探讨了SCF阴极与摩尔分数20%Sm_(2)O_(3)掺杂的CeO_(2)(SDC)进行不同比例的复合对电极性能的影响,优化了电极的化学膨胀和面积比电阻(ASR),进而提升了SOFC单电池的电化学性能。结果表明,SCF作为SOFC阴极,经950℃退火10 h后与普通电解质具有良好的化学相容性;其中,SCF与SDC按照质量比1:1复合的样品可以将纯SCF样品的平均热膨胀系数(TEC)从2.44×10^(−5)K^(−1)显著降到15.4×10^(−5)K^(−1)。此外,SCF-xSDC(x=20,30,40,50,x为SDC的质量分数)复合阴极的ASR在800℃下分别低至0.036、0.034、0.028和0.092Ω·cm^(2),SCF-40SDC在所有温度范围内都表现出更小的ASR。复合SDC可以优化SCF的三相界面且进一步提高SCF阴极的催化活性,以0.3mm厚La_(0.9)Sr_(0.1)Ga_(0.8)Mg_(0.2)O_(3-δ)(LSGM)为电解质的SCF-40SDC单电池(757 mW·cm^(−2))比SCF单电池(684 mW·cm^(−2))的最大功率密度更优,且超过目前大部分的文献报道。本研究制备的SCF−40SDC是一种性能优异的复合阴极材料,有望应用于中温固体氧化物燃料电池。

Intermediate-temperature solid oxide fuel cells(IT-SOFCs),as the operating temperature decreases,require cathode materials with high catalytic activity.In this study,double perovskite Sr_(2)CoFeO_(5+δ)(SCF)was synthesized by Sol-Gel method,and effect of SCF cathode compounded with 20%(molar fraction)Sm_(2)O_(3) doped CeO_(2)(SDC) at different ratios on the electrode performance was elucidated.The SOFC single-cell performance was improved by optimized chemical expansion and area-specific resistance(ASR)from composite electrodes.Results show that,SCF cathode after annealing at 950℃ for 10 h exhibits good chemical compatibility with common electrolytes.For the composite of SCF and SDC at a mass ratio of 1:1,the average thermal expansion coefficient(TEC)can be significantly reduced from 2.44×10^(−5)K^(-1)of pure SCF to 1.54×10^(−5)K^(-1).ASR of SCF−xSDC(x=20,30,40,50,x:mass percentage)composite cathodes are as low as 0.036,0.034,0.028 and 0.092Ω·cm^(2)at 800℃,respectively.The SCF−40SDC composite cathode displays the lowest ASR value among SCF−xSDC in the whole temperature range.Based on the 0.3 mm-thick La_(0.9)Sr_(0.1)Ga_(0.8)Mg_(0.2)O_(3-δ)(LSGM)electrolyte,the maximum power density of SOFC using SCF−40SDC(757 mW·cm^(−2))as a cathode is higher than that of pure SCF(684 mW·cm^(−2)).These results demonstrate that the SCF−40SDC composite cathode is a promising candidate for application in IT-SOFCs.