【作者】 王毓娟；

【导师】 林维明；

【作者基本信息】 华南理工大学 ， 工业催化， 2001， 博士

【摘要】 本论文通过对甲烷直接转化型SOFC电极的设计、制备、活性测试、表征以及单电池组装、电池性能评价等一系列工作，对甲烷在SOFC中的直接应用进行了较深入的研究。 参照多相催化剂的设计原则以及SOFC电极的特定要求提出电催化剂设计主要基于以下几个原则：（1）甲烷氧化活性；（2）材料的离子-电子双重电导性能：（3）适当结构的选择。提出适宜甲烷直接转化型SOFC阳极电催化剂组成——La等稀土元素修饰的Cu-Ce-Zr体系。在催化剂设计过程中对各组分之间的相互作用也进行了详细评述。 采用浸渍法、共沉淀法、溶胶-凝胶法、溶胶-凝胶法&浸渍法等四种方法制备了催化剂，发现溶胶-凝胶法和共沉淀法在活性和选择性最高，这是因为这两种方法制备的催化剂中立方、四方晶相比重高于浸渍法，Cu分散度更高，颗粒更微细。 对催化剂中CeO₂含量的影响进行了研究，催化剂活性随CeO₂含量增大而升高，TPR和XPS分析发现，催化剂中CeO₂含量增大，有利于增大Cu在载体表面的分散度，添加CeO₂之后催化剂表面出现Cu⁺，Cu的多价态特性增强了Ce的Redox能力；同时氧物种由O^2-转变为O^2-和活性更强的O₂^2-（或O^-）物种的混合。在组装电池之后，考察了加入CeO₂对电池性能的影响，发现CeO₂可以显著提高电池功率密度，改善电池极化特性；将催化剂活性、选择性以及表征结果综合起来分析认为Ce⁴⁺／Ce³⁺对的Redox性能是影响催化剂催化氧化活性的重要因素。 对Cu含量改变对催化剂性能的影响进行了研究，结果表明Cu进入Ce-Zr-O晶格有助于提高催化剂活性，但Cu自身活化甲烷的能力很弱；CuO中的O作为强结合氧对甲烷完全氧化有利，反应后CuO被还原为Cu₂O和Cu，完全氧化选择性降低；所以，催化剂中各价态的Cu物种分布存在一个对反应有利的最佳值，这可以通过制备方法、Cu含量以及添加助剂等方法进行调节。 升高焙烧温度强化了催化剂结晶度，各晶型比重也发生改变，主要表现为：更多还原

【Abstract】 The electrocatalyst for SOFC with direct oxidation of methane at anode was designed, prepared, characterized and its activity was evaluated. The solid oxide fuel cell was set up and its performance was tested with the aim of achieving more deep understanding on direct application of methane on SOFC.Based on both theories of heterogeneous catalysis and the special requirements of electrode for SOFC, electrocatalyst design principles were proposed as follows: first, the activity of total oxidaton of methane, second, the ion-electron mixed conductivity and third, the propriate microstructure. The catalyst system designed based on above principles was rare earth element as La doped Cu-Ce-Zr catalyst. The interaction among components was discussed in detail as well.Four methods were applied to prepared eletrocatalyst, as impregnation, coprecipitation, sol-gel and sol-gel &impregnation. Sol-gel and coprecipitation was prior to the other two method as to catalyst activity and selectivity due to the fact the content of cubic and tetragonal structure in catalyst were higher than that of impregnation.The effect of CeO₂ in catalyst was studied. The activity of catalyst was improved with increasing CeO₂ content. The addition of CeO₂ was benefit to Cu dispersion and influence the distribution of Cu species on catalyst surface. Cu⁺ could be stabilized in Ce-Zr-O lattice. And the multi-valance of copper increased redox ability of Ce. CeO₂ also affected surface oxygen species which changed from O^2- to the mixture of O^2- and more active O₂^2-. The effect of CeO₂ on performance of SOFC was investigated. Ceria could greatly improved power density of SOFC, low-down polarization. The redox activity of Ce⁴⁺/Ce³⁺ pair was proposed to be one of the most important factor which influence catalyst activity based on result of activity evaluation and catalyst characterization.The effect of Cu content on catalyst activity was studied . Although Cu is a weak catalyst to active C-H bond, dispersion of copper in Ce-Zr-O matrix could improve更多还原