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柴油车尾气排放的碳烟颗粒造成了日益严重的环境污染.目前催化燃烧是消除碳烟颗粒污染的有效技术.针对金属氧化物负载体系,20世纪70年代末谢有畅教授等人提出了单层分散理论,是指导设计高效负载催化剂的一个重要思想,已被科研工作者们普遍接受.当负载催化剂体系用于某个特定反应时,通常会表现出单层分散阈值效应,即负载的活性组分含量为单层分散阈值时,催化剂往往具有最好的活性和选择性.为探究金属氧化物在复合氧化物载体上的分散行为,并期望研制出性能优良的碳烟颗粒消除催化剂,本文制备了系列不同负载量的CuO/La2Sn2O7催化剂,并把实验表征技术和DFT计算方法相结合,对其构效关系进行了研究.结果表明,CuO可自发分散在La2Sn2O7烧绿石载体,其单层分散容量为1.90 mmol CuO/100 m2 La2Sn2O7.CuO负载量不高于该容量时,以亚单层或单层分散状态存在.XPS、Raman、Bader电荷和DOS分析证明,亚单层/单层CuO中的Cu2+离子可把其电荷选择性地传递给La2Sn2O7烧绿石载体结构中B位的Sn4+离子,因而与载体产生强相互作用.反之,Cu2+离子与载体结构中A位的La3+离子之间无电荷转移,不产生作用.这表明在含多种金属离子的复合氧化物载体上,被负载的金属氧化物可优先与载体中的一种金属离子产生相互作用.Raman、原位DRIFTS和XPS结果表明,在界面上形成的O2?和O22?亲电氧离子是CuO/La2Sn2O7催化剂表面的活性中心,其含量决定了催化剂碳烟颗粒燃烧的活性.在CuO负载量低于单层分散容量时,这些表面活性亲电氧离子含量随着CuO的负载量升高而增加,直至单层分散容量时达到最大.在CuO负载量高于单层分散容量时,CuO微晶开始形成,并对表面活性亲电氧离子的生成产生负面影响.上述结果表明,CuO/La2Sn2O7催化剂用于碳烟颗粒燃烧具有明显的单层分散阈值效应;并可通过在La2Sn2O7载体表面负载单层分散量的CuO获得活性最佳的催化剂.“,”To understand the dispersion behavior of metal oxides on composite oxide supports and with the expectation of developing more feasible catalysts for soot oxidation, CuO/La2Sn2O7 samples con-taining varied CuO loadings were fabricated and characterized by different techniques and density functional theory calculations. In these catalysts, a spontaneous dispersion of CuO on the La2Sn2O7 pyrochlore support formed, having a monolayer dispersion capacity of 1.90 mmol CuO/100 m2 La2Sn2O7 surface. When loaded below this capacity, CuO exists in a sub-monolayer or monolayer state. X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and Bader charge and density of states analyses indicate that there are strong interactions between the sub-monolayer/monolayer CuO and the La2Sn2O7 support, mainly through the donation of electrons from Cu to Sn at the B-sites of the structure. In contrast, Cu has negligible interactions with La at the A-sites. This suggests that, in composite oxide supports containing multiple metals, the supported metal oxide interacts preferentially with one kind of metal cation in the support. The Raman, in situ diffuse reflectance infrared Fourier transform spectroscopy, and XPS results confirmed the for-mation of both O2-and O22-as the active sites on the surfaces of the CuO/La2Sn2O7 catalysts, and the concentration of these active species determines the soot combustion activity. The number of active oxygen anions increased with increase in CuO loading until the monolayer dispersion capacity was reached. Above the monolayer dispersion capacity, microsized CuO crystallites formed, and these had a negative effect on the generation of active surface oxygen sites. In summary, a highly active catalyst can be prepared by covering the surface of the La2Sn2O7 support with a CuO monolayer.