【作者】 李浩；

【导师】 王拓；

【作者基本信息】 天津大学 ， 化学工艺， 2018， 硕士

【摘要】 表界面催化在化学工业、电化学、光化学反应中扮演了重要的角色。优化化学反应过程和理解化学反应机理是现代催化需要应对的重要挑战。上世纪六十年代,表面科学分析系统的建立已经允许在原子/分子尺度研究表界面现象。为此我们开展了超高真空STM系统,以及集成有XPS表面分析系统的调试和升级。并立足于表界面科学的视角,开展了RuO₂/TiO₂界面性质的研究。这些研究为进一步从原子/分子角度理解催化过程和构建复合氧化物界面相互作用理论打下了基础。本工作首先升级改造了STM系统和XPS系统。其次,针对载体晶型影响的RuO₂/TiO₂结构展开了研究。通过对比两种TiO₂晶相,优化RuO₂/TiO₂焙烧温度揭示了TiO₂晶相对于RuO₂分散的关键作用。并使用XPS系统表征了一系列不同Ru负载量的RuO₂/r-TiO₂,确定了RuO₂在r-TiO₂表面高效分散的负载量阈值。基于TiO₂表面上高效分散的超薄RuO₂与载体形成的有序界面结构,本文研究了CO氧化反应动力学性质和RuO₂与TiO₂间界面电子转移的关系。结合谱学表征和密度泛函理论计算得出,在低Ru负载量时,RuO₂在TiO₂台阶或者氧空位上落位,会得到这些缺陷位点富余的电子,表现高的CO氧化表观活化能。中等Ru负载量时,RuO₂扩展至r-TiO₂的平台位点,会转移电子给r-TiO₂平台位,表现低CO反应表观活化能。在含有0.75 wt%中等Ru负载量的RuO₂/r-TiO₂上,实现了最低的CO氧化表观活化能。更高Ru负载量时,厚的RuO₂覆盖层会掩盖住RuO₂和TiO₂间界面电子转移造成的影响,而表现出和负载于惰性载体一致的表观活化能。更多还原

【Abstract】 The surface and interfacial catalysis plays important role in chemical industry,electrocatalysis and photocatalysis.Optimizing chemical processes and understanding reaction mechanism are critical challenges for modern catalysis.Since¹960s,the foundation of surface science systems has allowed the study of surface and interfacial phenomena on atomic/molecular level.Therefore,we have updated the STM system and calibrated the XPS system of surface analysis.Furthermore,standing on insight of surface science,we have studied the interfacial properties of RuO₂/TiO₂.These researches have built base work to further research catalytic process and is helpful to construct theory of interfacial interaction between mixed oxides.Firstly,this work updated STM and XPS system.Then we studied the structure of RuO₂/TiO₂ depended on crystalline phase of suports.By optimizing the calcined temperature,and using related characterization,the critical role of TiO₂ crystalline phase on dispersity of RuO₂ is revealed.By further XPS characterization,we have identified the critical Ru loading for high dispersity of RuO₂ on r-TiO₂.Based on the ordered interfacial structure between ulthin RuO₂ and TiO₂ surface,the thesis also investigates the relationship between kinetic of CO oxidation and interfacial electrons transfer between RuO₂ and TiO₂.By combing spectroscopic studies and density functional calculation,we have acquired that at very low loadings,the majority of RuO₂ catalysts can be anchored at the defective sites of TiO₂ substrates.The electron transfers from defective sites of substrates to RuO₂ causes an increase in the apparent reaction barrier of CO oxidation.As the loading of Ru increases,RuO₂starts to appear on the terrace of TiO₂,and the apparent reaction barrier of CO oxidation decreases.At the medium loading of⁰.75 wt%,the lowest apparent reaction barrier is achieved.The phenomenon can be attributed to the electron transfer from RuO₂ to the terrace of TiO₂.Further increasing the loading of Ru,the apparent reaction barrier rises again.When the loading of Ru is more than 2 wt%,the apparent reaction barrier is found to be very comparable to that over RuO₂ catalysts supported on inert substrate,indicating that the electronic effect of TiO₂ is isolated underneath thick RuO₂ overlayers.更多还原