The Strong-Metal Support Interaction: Insights from Molecular Theories and Experiments

催化剂在现代社会的许多方面都扮演着必不可少的幕后角色。例如，催化剂降低了从原油生产高性能汽油的能量损失。在塑料生产中，催化剂选择性地引导化学反应沿着一定的途径进行，以产生所需的产品。催化反应中潜在途径的数量很多，在反应过程中催化剂本身的结构可能会发生显著的变化。由于这种复杂性，催化中许多现象的分子水平方面还没有完全阐明。尽管在近30年前就被发现，但强金属-载体相互作用(SMSi)是一种在分子水平上仍然知之甚少的现象。SMSi指的是催化金属纳米颗粒和氧化物载体之间的强烈相互作用，金属固定在氧化物载体上。在相对常见的反应条件下，一部分氧化物载体实际上可能形成部分覆盖催化纳米颗粒的膜。这种薄膜可以促进或抑制催化过程，这取决于所涉及的特定催化材料，而了解和控制其性质的一般策略尚不存在。因此，该项目的中心目标是揭示这些催化剂系统的不同成分如何协同工作以提高催化剂性能的分子科学。为了利用SMSi通过利用分子水平的洞察力来促进催化，该项目将结合周期性密度泛函理论计算与表面科学实验和对模型纳米颗粒的测量，来研究过渡金属衬底上超薄(羟基)氧化物薄膜的结构、能学和电子性质的趋势。我们将开发出薄膜结构随环境压力和温度变化的严格模型。这些预测将在单晶衬底模型上进行，并将根据一系列超高真空表面科学实验进行修正。从这些理论和实验相结合的研究中出现的趋势将在纳米粒子模型上得到验证。预计该项目将提供关于超薄(羟基)氧化物/金属界面的丰富信息，并将为控制和开发SMSi提出新的战略。这一基础知识反过来可能导致开发用于能源和健康应用的强大催化剂。这项工作将由两名研究生进行，他们将接受最先进的理论和实验催化技术培训。这些学生将得到来自经济困难背景的高中实习生的帮助，他们也将接触到这些前沿的科学方法。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Catalysts play an essential 'behind-the-scenes' role in many aspects of modern society. For example, catalysts lower the energy loss of producing high performance gasoline from crude oil. In the production of plastics, catalysts selectively lead chemical reactions down a certain pathway to produce desired products. The number of potential pathways in catalytic reactions is large, and the catalyst structure itself may change significantly during the reactions. Due to this complexity, molecular-level aspects of many phenomena in catalysis have not been fully elucidated. Despite being discovered nearly thirty years ago, the strong metal-support interaction (SMSI) is one such phenomenon that remains poorly understood at a molecular level. SMSI refers to the strong interaction between a catalytic metal nanoparticle and an oxide support, to which the metal is anchored. Under reaction conditions that are relatively common, a portion of the oxide support may actually form a film that partially covers the catalytic nanoparticle. This film can either promote or inhibit catalytic processes, depending upon the particular catalytic materials involved, and a general strategy to understand and control its properties does not exist. The central goal of this project is, therefore, to unravel the molecular science of how the different components of these catalyst systems work together to enhance catalyst performance. To use SMSI to promote catalysis by leveraging molecular-level insights, this project will combine periodic Density Functional Theory calculations with surface science experiments and measurements on model nanoparticles to study trends in the structure, energetics, and electronic properties of ultrathin (hydroxy)oxide films on transition metal substrates. Rigorous models of the films' structures as a function of ambient pressures and temperatures will be developed. The predictions will be performed on single crystal substrate models, and will be refined against a series of ultrahigh vacuum surface science experiments. The trends that emerge from these combined theoretical and experimental studies will then be validated on nanoparticle models. It is anticipated the project will provide a wealth of information about ultrathin (hydroxy)oxide/metal interfaces and will suggest new strategies for controlling and exploiting the SMSI. This fundamental knowledge may, in turn, lead to the development of robust catalysts for energy and health applications. The work will be carried out by two graduate students who will be trained in state-of-the-art techniques in theoretical and experimental catalysis. The students will be assisted by high school interns from economically disadvantaged backgrounds who will also be exposed to these forefront scientific methods.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.