Probing the Structure-property Relationship of Core/Shell Bimetal Nanoparticles as a Model Catalyst

摘要技术影响将两种金属结合制成双金属催化剂通常会产生比任何一种组成金属更具有催化活性的材料。除了较高的活性外，双金属催化剂还具有更好的选择性和更强的抗失活能力。解释双金属增强如何产生的催化化学还没有得到很好的解释。根据化学反应的不同，这种增强可以归因于几何效应、电子效应或混合金属位效应。确定催化增强的来源有很多困难：增强可能是由于这些效应的组合；双金属纳米结构在合成水平上没有得到很好的控制；可能存在金属-支撑相互作用；或者所研究的双金属纳米结构可以在化学反应中重新配置。因此，如何加深对双金属催化剂的认识，使其得到合理的利用是一个重要的问题。休斯敦威廉·马什·莱斯大学（William Marsh Rice University）的迈克尔·黄（Michael Wong）教授提出了一种方法，可以进一步加深这种理解。Wong打算将重点放在双金属催化剂的模型上，其中一种金属的金属纳米颗粒是第二种活性金属的支撑。这种相互作用是内在的、可控的，适合在接近反应条件下用光谱方法分析双金属纳米结构；最终在不改变纳米结构的反应条件下量化了它们的催化性能。该模型体系是在前人研究的基础上，利用金纳米颗粒负载钯金属，模型试验反应是在水相中催化三氯乙烯加氢脱氯。催化技术的持续创新依赖于新材料的发展和催化剂纳米结构对反应性的严格阐明。PdAu双金属催化作为一种新型的水相加氢脱氯技术，具有广阔的应用前景。这项技术对控制地下水污染很重要，美国50%的饮用水都来自地下水。本提案描述了一个为期三年的研究和教学计划，包括对研究生和本科生在材料化学、多相催化、化学工程基础和胶体科学方面的多学科培训。提出了三项新的教育和社区推广活动：每年在休斯顿儿童博物馆举办的“纳米日”演示，与美国国家科学基金会赞助的赖斯大学RET项目合作的地方高中教师发展项目，以及将实验室模块设计项目纳入研究生水平的动力学/反应堆工程课程。该奖项由CBET催化与生物催化项目和CHE催化项目共同资助。

AbstractTechnical ImpactThe combination of two metals to make a bimetallic catalyst frequently leads to a more catalytically active material than either constituent metal. Besides higher activities, bimetallic catalysts can have improved selectivities and greater deactivation resistance. The catalytic chemistry that explains how bimetallic enhancement arises is not well explained. Depending on the chemical reaction, the enhancement can be attributed to a geometric effect, an electronic effect, or a mixed metal site effect. The difficulties in determining the source of catalytic enhancement are numerous: enhancement could be due to a combination of these effects; the bimetallic nanostructure is not well-controlled at the synthesis level; there may be a metal-support interaction; or the studied bimetallic nanostructure can reconfigure during the chemical reaction.So, how to develop a greater understanding of bimetallic catalysts so that they may be exploited appropriately is a significant question. Professor Michael Wong at William Marsh Rice University in Houston has an approach to developing more of this understanding. Wong intends to focus on a model of a bimetallic catalyst in which metallic nanoparticles of one metal are the support for the second active metal. The interaction is built-in and controllable, and amenable to the analysis of the bimetallic nanostructure using spectroscopic methods near reaction conditions; and culminating in the quantification of their catalytic properties under reaction conditions that do not modify the nanostructure. The model system is based on previous studies using palladium metal supported on gold nanoparticles, and the model test reaction is the catalysis in the water phase of trichloroethene hydrodechlorination. Continued innovations in catalysis technology rely on the development of novel materials and the rigorous elucidation of reactivity dependence on catalyst nanostructure.PdAu bimetallic catalysis has shown some promise as a new technology for water-phase hydrodechlorination. This technology is important for pollution control in groundwater, a source for 50% of US drinking water.Broader ImpactThis proposal describes a three-year research and teaching plan consisting of multidisciplinary training of graduate and undergraduate students in materials chemistry, heterogeneous catalysis, chemical engineering fundamentals, and colloid science. Three new educational and community outreach activities are proposed: a yearly NanoDays demonstration at the Children's Museum of Houston, a local-area high school teachers development program in coordination with the NSF-sponsored RET program at Rice, and a lab module design project incorporated into the graduate-level kinetics/reactor engineering course. This award is being funded jointly by the CBET Catalysis and Biocatalysis Program and the CHE Catalysis Program.