【作者】 赵凯；

【导师】 徐庆；

【作者基本信息】 武汉理工大学 ， 材料学， 2011， 硕士

【摘要】 La2NiO4+δ体系层状化合物具有电子-离子混合导电性能,是中温固体氧化物燃料电池(SOFC)阴极材料新的研究热点。本论文采用氨基多羧酸配合物法合成La2NiO4+6超细微粉体,采用丝网印刷工艺在致密的Ce0.8Sm0.2O1.9电解质基体上制备La2NiO4+δ多孔电极,研究La2NiO4+δ多孔电极的制备工艺条件对多孔电极显微结构和电化学性能的影响,探索La2NiO4+δ多孔电极合适的制备工艺条件,研制具有高电化学催化活性的La2NiO4+δ多孔电极。制备了La2NiO4+δ/Ce0.8Sm0.2O1.9/Pt三电极结构的电化学电池,采用电化学阻抗谱、计时电压法、塔菲尔曲线分析等手段研究了各个电极过程和总的电极电化学反应的极化电阻、不同电流密度下的过电势、交换电流密度等电化学性能。研究结果表明,电极的阻抗响应来自电极/电解质界面的电荷传递过程和电极表面的氧交换过程。其中,电极表面的氧交换过程是产生电极极化的主要原因。研究了电极浆料组成和烧结温度对La2NiO4+δ多孔电极显微结构的影响。研究结果表明,通过调整制备工艺条件,可以调控多孔电极与电解质之间的接触状态、孔隙率、多孔电极的晶粒粒径、晶粒之间的连接程度等显微结构特征。本论文还研究了多孔电极的显微结构对电化学性能的影响。研究结果表明,多孔电极与电解质基体之间的接触状态主要影响电极/电解质之间的电荷传递过程,多孔电极的晶粒粒径和晶粒之间的连接程度主要影响电极表面的氧交换过程,采用超微细粉体制备La2NiO4+δ多孔电极有利于优化多孔电极的显微结构和提高其电化学催化活性。确定合适的多孔电极制备工艺条件是：采用超微细La2NiO4+δ粉体(平均粒度-90nm)为起始粉体、浆料固含量为70%、烧结温度为950℃,在该条件下制备的La2NiO4+δ多孔电极具有理想的显微结构和优良的电化学性能。在800℃下该多孔电极的极化电阻为0.38Ω·cm2,在200mA·cm2的电流密度下的过电势为103mV,在平衡状态下其交换电流密度为102mA·cm-2。更多还原

【Abstract】 La2NiO4+δ-based layer-structured compounds have attracted increasing attention as a novel candidate material for the cathode of intermediate temperature solid oxide fuel cells (SOFCs) because of their electronic-ionic mixed conducting characteristics. Superfine La2NiO4+δpowder has been derived from a ployaminocarboxylate complex precursor with diethylenetriaminepentaacetic acid (H5DTPA) as ligand. Electrochemical cells with a three-electrode configuration of La2Ni04+δ/Ce0.8Sm0.2O1.9/Pt have been fabricated by the screen-printing technique using the superfine La2NiO4+δpowder as the starting powder of the slurry. The electrochemical properties of porous La2NiO4+δelectrodes on dense substrates of the electrolyte have been investigated based on the electrochemical cells with respect to preparation conditions and the resulting microstructures.Electrochemical impedance spectroscopy, Chronopotentiometry and Tafel plot analysis were employed to investigate the electrochemical properties of La2Ni04+δelectrodes. The electrochemical parameters, such as polarization resistance, cathodic overpotential and exchange current density, were analyzed with respect to the composition of the slurry and sintering temperature of the electrodes. It was found that the electrode polarization mainly originated from the charge transfer process at the electrode/electrolyte interface and the oxygen exchange process on the surface of the porous electrodes, with the latter process dominating the overall electrode reaction.The electrocatalytic activity of the porous La2NiO4+δelectrodes has been evaluated in relation to their microstructural features, including the grain size, connection between the grains, the porosity of the electrode and the adhesion of the electrode to the electrolyte. A close dependence of the electrocatalytic activity on the microstructure was confirmed. It was found that a tight adhesion between the electrode and the electrolyte favored the interfacial charge transfer process, while fine grain size together with reasonable connectivity between the grains benefited the surface oxygen exchange process. From a microstructural viewpoint, the grain size and connectivity between the grains acted as the key contributing factors to the electrocatalytic activity of the porous electrodes. Adopting the superfine powder to fabricate the electrode was suggested to be favorable to modifying the microstructure and improving the electrocatalytic activity.Employing the powder clacined at 900℃as the starting powder, adopting the slurry with a solid content of 70% for screen printing and sintering the electrode at 950℃was determined to be the optimum preparation conditions based on comparative research. At 800℃, the electrode prepared under the conditions exhibited satisfactory electrochemical properties compared with literal results, showing a polarization resistance of 0.38Q·cm2, an overpotential of 103mV at a current density of 200mA·cm-2 and an exchange current density of 102mA·cm-2.更多还原