基于金属氢氧化物负载的纳米金催化剂的制备及构效关系研究

Supported gold nanocatalysts exhibit distinctive catalytic properties in many catalytic reactions, among which, CO oxidation is always used as probe reaction to investigate the catalytic mechanism of gold catalysis. Currently,the surface hydroxyl group effect to enhance the activity of gold catalysts in CO oxidation has attracted great attention, however the the relevant fundamental understanding is still ambiguous. Metal hydroxides supported gold catalysts (Au/M(OH)x) could be ideal target system in which the surface hydroxyl group effect can be more crucial to the resulted catalytic properties due to the large amount of strongly bounded hydroxyl groups in the surface of the support. However, research work related to Au/M(OH)x catalyst is rarely reported. This project aims to synthesize a series of low dimentional metal hydroxides materials, which will then be used as supports to prepare supported gold catalysts. We will further explore the structure-property relationship by combining the experimental investigation and theory calculations, among which the surface hydroxyl group effect to the metal-support interaction and molecular oxygen activation in CO oxidation will be specially investigated. Based on the experimental results and theoretical modulations, the mechanism of surface hydroxy group effect will be elucidated. This project can provide important experimental evidence and theoretical guidance on the applications of stable metal hydroxides materials in catalysis.

作为纳米催化领域考察催化材料结构和活性依赖关系的标杆催化剂，负载型纳米金催化剂独特的催化性质和广阔的应用前景使其备受关注。研究表明，负载型金催化剂表面羟基对低温催化CO氧化有着直接的促进作用，但其机理尚不明确。而金属氢氧化物材料表面富含羟基，其相应的负载型金催化剂可以为表面羟基对催化剂催化CO氧化活性的影响机理研究提供理想的体系。本项目拟设计合成系列尺寸、形貌与表面可控的低维碱土金属和稀土氢氧化物材料，以其作为载体，通过金纳米颗粒的负载，制备相应的负载型金催化剂；研究此类催化剂低温催化CO氧化的催化行为，并结合理论计算，从实验和理论两方面重点考察载体表面羟基对催化剂结构以及氧分子活化的影响；揭示碱土金属与稀土氢氧化物为载体的负载型金催化剂的结构/微结构特点与其催化性能的内在联系，探索金属氢氧化物材料在多相催化领域的应用前景。

本项目针对基础催化问题，研究纳米催化剂在反应过程中的本征活性位点及其构效关系，主要研究成果有：基于氢氧化铁/氧化铁基负载的纳米Au催化剂体系，通过对比不同处理条件催化剂，发现铁基催化剂表面羟基对催化一氧化碳氧化反应有重要促进作用；基于氧化铈负载的三种不同聚集程度的金物种，利用原位技术追踪反应过程中金物种的状态，证明了金属态的金物种在二氧化铈负载金催化室温一氧化碳氧化反应中做出的活性贡献更大；在铜铈催化剂体系，通过系统的对比试验，借助原位X射线近边吸收技术，充分验证了弱相互作用的CuOx簇对于PROX反应的活性贡献更大，进一步通过不同晶面取向的纳米晶的催化差异和结构区别之间进行关联，发现CeO2-{111}晶面对于催化反应高活性的重要贡献。本项目对于深入理解纳米催化剂在异相催化反应中的催化行为具有重要的意义，也为合理地构建高效催化剂提供了有价值的理论依据。