Chemical Dynamics of Polyatomic Molecules at Surfaces: New Insights into Complex Systems from State-Selected Studies

在这个由化学学部化学结构动力学和机理（CSDM-A）项目资助的项目中，来自塔夫茨大学的Arthur Utz教授正在使用复杂的激光和分子束技术来研究金属表面分子的反应。金属颗粒通常在商业化学过程中用作催化剂。它们选择性地将反应物转化为所需的产物，减少浪费的副产物的产生，提高反应速率，降低能源需求。了解催化剂的工作原理是提高其性能的关键一步。然而，这个问题是具有挑战性的，因为反应物能量的范围很广，并且在工作催化剂上发现了许多不同的原子结构。为了解开这种复杂性，乌茨教授和他的学生们正在准备具有精确能量的反应物。然后，他们在一系列表面上测量它们的反应性，这些表面具有与工作催化剂相似的明确结构。这项工作提供了对反应物能量和表面结构如何导致催化活性的系统和定量理解。从该项目中获得的见解可以提高我们设计和优化催化剂的能力，这可能对社会有重要的好处。该项目还对学生进行了先进实验方法和界面科学方面的培训，并提供了激发兴趣的推广活动，丰富了当地学校K-12科学和技术课程。该项目侧重于解离化学吸附的能量学和动力学，以建立催化活性的机理图。一个关键的目标是了解增加气相试剂和表面的结构和化学复杂性如何影响反应性。超音速分子束和红外激光分别赋予反应物分子精确定义的动能和内能。选择金属表面系统地介绍了工作催化剂的结构特征。分子束反射率和表面敏感光谱定量反应概率作为试剂的平移，振动和旋转能量的函数，以及表面结构和温度。与合作者的电子结构和反应散射计算相一致，结果描绘了控制气体表面反应性的潜在过程的详细画面，并揭示了反应模式如何随着复杂性的增加而持续或变化。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

In this project funded by the Chemical Structure Dynamics and Mechanism (CSDM-A) program of the Chemistry Division, Professor Arthur Utz from Tufts University is using sophisticated laser and molecular beam techniques to study the reactions of molecules on metal surfaces. Metal particles are commonly used as catalysts in commercial chemical processes. They selectively convert reactants to the desired product, reduce production of wasteful byproducts, increase reaction rate, and lower energy requirements. Understanding how catalysts work is a key step toward improving their performance. The problem is challenging, however, due to the wide range of reactant energies, and the many different atomic structures found on a working catalyst. To unravel this complexity, Professor Utz and his students are preparing reactants with precise quantities of energy. They then measure their reactivity on a series of surfaces containing well-defined structures that resemble the features present on a working catalyst. The work is providing a systematic and quantitative understanding of how reactant energy, and surface structure, lead to catalytic activity. Insights gained from the project could advance our ability to design and optimize catalysts, which could have important benefits to society. The project is also training students in advanced experimental methods and interfacial science, and it is providing outreach activities that stimulate interest, and enrich the K-12 Science and Technology curriculum at local schools. The project focuses on the energetics and dynamics of dissociative chemisorption to build a mechanistic picture of catalytic activity. A key goal is to understand how increasing the structural and chemical complexity of the gas phase reagent and the surface affects reactivity. A supersonic molecular beam and infrared laser, respectively, impart reactant molecules with a precisely defined kinetic and internal energy. Metal surfaces are chosen to systematically introduce structural features characteristic of working catalysts. Molecular beam reflectivity and surface-sensitive spectroscopies quantify reaction probability as a function of reagent's translational, vibrational, and rotational energies, as well as the surface structure and temperature. In concert with collaborators' electronic structure and reactive scattering calculations, the results paint a detailed picture of the underlying processes that govern gas-surface reactivity and reveal how reactivity patterns persist or change as complexity increases.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.