新型双功能Ce-La复合氧化物的形貌可控合成及其负载金颗粒的催化性能研究

The change of chemical bond and ligand environment not only improves the amount of oxygen species and diffusion rate of metal ions, but also generates a large number of defects in the surface of oxide when a foreign metal ion is induced into the matrix oxide lattice. Hence the composite oxide usually exhibits more excellent catalytic performance than single component oxide. The concentration of oxygen vacancy depends on the oxidation state of doped ions, and the activity of oxygen vacancy/oxide ions depends on the binding energy of doped ions and oxygen vacancies. Traditional Ce-based catalyst, focused on the Ce-Zr, Ce-Mn composite oxide and the introduction of the new components of Zr and Mn, generally only increases the defects of the CeO2 and oxygen mobility and strengthens redox ability, and then improving the catalytic activity. However, the system function is relative single, and its catalytic performance is limited. In this proposal, we try to change the surface redox environment of CeO2 and construct novel bifunctional Ce-La composite oxide through the utilization of basic property of La2O3. Combining with morphology effect of support, we can adjust morphology and composition of Ce-La composite oxide, which can expose different crystal plane and selectively deposit Au nanoparticles of different sizes. The microcosmic mechanism of Ce-La composite oxide support and synergy effects between the metal and support will be clarified in the catalytic reactions (e.g., CO oxidation and cinnamaldehyde hydrogention). A breakthrough in the novel catalyst construction and the catalytic performance manipulation will be expected. The research results will provide scientific guidance to the development of novel bifunctional composite oxide catalysts.

当第二种金属离子进入母体氧化物的晶格中, 化学键和配位环境的改变不仅提高了氧物种和金属离子的扩散速率, 而且还在氧化物表面产生大量的缺陷位，因此复合氧化物通常比单一的氧化物具有更优异的催化性能。氧空位的浓度依赖于掺杂离子的氧化态，而氧空位/氧化物离子的活动性依赖于掺杂离子和氧空位的结合能。传统的Ce基催化剂体系可能集中在Ce-Zr、Ce-Mn等组分间，新组分Zr和Mn等的引入一般只是为了增加CeO2载体本身的缺陷位以及氧的移动性，增强其氧化还原能力，从而提高催化活性，该体系功能单一，并且其催化性能的提高也受到限制。本项目利用La2O3独特的表面碱性位结构，引入CeO2晶格结构中，改变CeO2本身的表面环境，构建Ce-La的酸碱性双功能作用机制特性，结合形貌效应，调控Ce-La复合氧化物载体的晶面，选择性沉积不同尺寸的Au纳米粒子，阐明载体的双功能微观作用机制和金属载体之间的表界面协同机制。

本项目通过创新纳米催化材料合成科学和技术，可控构建出具有不同金属组成、结构、担载量、尺寸、酸碱性、酸性分布、比表面积、孔径分布的氧化物负载纳米尺寸贵金属以及建立复合氧化物可控合成方法；阐明催化材料组成、结构和性质与 CO 氧化以及肉桂醛加氢反应催化活性和产物选择性之间的构效关系；为揭示 CO 氧化以及肉桂醛加氢反应活性和产物选择性协同调控机制、构建具有 CO 氧化以及肉桂醛加氢反应的多中心协同的纳米催化材料提供可靠的实验证据和理论依据。我们基本完成了纳米催化材料合成的创新设计以及多中心协同思路，开发合成了形貌控制、方法控制以及择形设计等多种多功能协同催化剂，选择不同催化反应对多功能协同催化剂进行了测试，推测了可能的多功能协同机理，为构建催化构效关系提供了可靠的实验依据，并为日后的工业应用提供了新的思路