固体氧化物燃料电池阳极材料La_xSr_(2–x)MgMoO_(6–δ)的结构与电化学性能

Structure and Electrochemical Performance of La-doped Sr_2MgMoO_(6–δ) as an Anode Material for Solid Oxide Fuel Cell

通过柠檬酸络合法合成了La_xSr_(2–x)MgMoO_(6–δ)(LSMM)阳极材料。利用X射线衍射和扫描电子显微镜分析样品的物相结构、微观形貌及与电解质的化学相容性,采用四端引线法测试材料的电导率,利用电化学工作站测试其阳极阻抗特性,并以La_(0.8)Sr_(0.2)Ga_(0.8)Mg_(0.2)O_3(LSGM)为电解质、PrBaCo_2O_(5+δ)为阴极制备了单电池,测试功率密度。结果表明:空气中La的掺杂量小于0.2(摩尔分数)时,还原后La的掺杂量可以达到0.6,La的掺杂导致晶胞体积增大。La掺杂的Sr_2MgMoO_6(SMMO)与电解质LSGM、Ce_(0.8)Gd_(0.2)O_(2–δ)(GDC)在1 250℃煅烧10 h,均没有杂质相生成,具有良好的化学相容性。La掺杂显著提高了SMMO的电导率,800℃、5%H2/Ar气氛中,La_(0.6)Sr_(1.4)MgMoO_(6–δ)的电导率为40 S/cm。La的掺杂降低了阳极材料的极化电阻,提高了电池功率密度。

LaxSr2-xMgMoO6-δ （LSMM） anode material was synthesized via a citrate acid complexing method. The phase composition was determined by X-ray diffraction, and the microstructure of the sintered samples was determined by scanning electron microscopy. The electrical conductivity of all samples was measured by a standard four-terminal de method, and the AC electrochemical impedance spectra were detected in a symmetrical cell. Single fuel cells were prepared using an electrolyte-supported technique with La0.8Sr0.EGa0.8Mg0.2O3（LSGM） as an electrolyte, LSMM as an anode and PrBaCo2O5＋δ as a cathode. The results demonstrate that the doping limit of La is less than 0.2 in air, which is 0.6 after reducing in 5%Ha/Ar. The doping leads to the increase of cell volume of LSMM. The LSMM anode material has a good chemical compatibility with GDC and LSGM electrolytes after calcining at 1 250℃ for 10 h. The La doping increases the electronic conductivity of La0.6Sr1.4MgMoO6-δ, which is 40 S/cm at 800 ℃ in 5%H2/Ar, and decreases the polarization resistance, resulting in the improvement of power density for single cells.