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化学学报
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化学学报 ›› 2009, Vol. 67 ›› Issue (7): 623-628. 上一篇    下一篇

研究论文

La 0.9 M 0.1 Ga 0.8 Mg 0.2 O 3 -α的中温质子导电性及其在常压合成氨中的应用

陈 成 王文宝 马桂林*

  

  1. (苏州大学材料与化学化工学部 江苏省有机合成重点实验室 苏州 215123)

  • 投稿日期:2008-08-16 修回日期:2008-10-31 发布日期:2009-04-14
  • 通讯作者: 马桂林

Proton Conduction in La0.9M0.1Ga0.8Mg0.2O3－α at Intermediate Temperature and Its Application to Synthesis of Ammonia at Atmospheric Pressure

Chen, Cheng Wang, Wenbao Ma, Guilin*   

  1. (Key Laboratory of Organic Synthesis of Jiangsu Province, College of Chemistry, Chemical Engineering and
    Materials Science, Suzhou University, Suzhou 215123)
  • Received:2008-08-16 Revised:2008-10-31 Published:2009-04-14
  • Contact: Ma, Guilin

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采用水热沉淀法制备了La0.9M0.1Ga0.8Mg0.2O3-α (M＝Ca2＋, Sr2＋, Ba2＋)陶瓷样品的前驱体, 沉淀剂来自尿素在水热条件下的水解产物. 前驱体经煅烧和烧结后得到陶瓷样品. XRD显示样品具有单一的斜方晶LaGaO3钙钛矿结构. 同位素效应和氢的电化学透过(氢泵)实验证明陶瓷样品具有质子导电性. 用AC阻抗谱法测定了样品在300～600 ℃、氢气气氛中的质子电导率, 其大小取决于La位掺杂的碱土金属离子: σ(M＝Sr2＋)＞σ(M＝Ba2＋)＞σ(M＝Ca2＋). 以La0.9M0.1Ga0.8Mg0.2O3-α为固体电解质进行了常压合成氨, 最佳合成温度为520 ℃. 当施加的电流密度为1 mA•cm－2、合成温度为520 ℃时, 氨产率分别为: 1.63×10–9 mol•s－1•cm－2 (M＝Ca2＋), 2.53×10－9 mol•s－1•cm－2 (M＝Sr2＋)和2.04× 10－9 mol•s－1•cm－2 (M＝Ba2＋).

关键词: LaGaO3, 水热沉淀法, 质子导电性, 常压合成氨

The precursors of La0.9M0.1Ga0.8Mg0.2O3–α (M＝Ca2＋, Sr2＋, Ba2＋) were prepared by a hydrothermal precipitation method in which the precipitant was from hydrolysis of urea (CO(NH2)2) in water solution under hydrothermal conditions. The ceramic samples were obtained by calcining and sintering the precursors. XRD showed the ceramic samples to be of a single orthorhombic phase of LaGaO3 perovskite structure. The proton conduction in La0.9M0.1Ga0.8Mg0.2O3－α was confirmed by an isotope effect and a hydrogen pumping experiment. Protonic conductivity was measured by an AC impedance spectroscopy method from 300 to 600 ℃ in a hydrogen atmosphere, which depended on the alkaline earth cations doped for the La site and increased in the following order: σ(M＝Sr2＋)＞σ(M＝Ba2＋)＞σ(M＝Ca2＋). Ammonia synthesis at atmospheric pressure was carried out using La0.9M0.1Ga0.8Mg0.2O3–α as electrolyte, and it was found that the optimum temperature for ammonia synthesis in this study was 520 ℃. The rate of NH3 formation was 1.63×10–9 mol•s－1•cm－2 (M＝Ca2＋), 2.53×10–9 mol•s－1•cm－2 (M＝Sr2＋) and 2.04×10–9 mol•s－1•cm－2 (M＝Ba2＋) at 520 ℃ when a current density of 1 mA•cm–2 was imposed on the cell, respectively.

Key words: LaGaO3, hydrothermal precipitation, proton conduction, ammonia synthesis