NSF-BSF: Surface-Sensitive Spectroscopy and Microscopy on Metal/Oxide Interfaces at Atmospheric Pressures

NSF-BSF：大气压下金属/氧化物界面的表面敏感光谱和显微镜

• 批准号: 1906014
• 负责人: Miquel Salmeron
• 金额: $ 30.51万
• 依托单位: University of California-Berkeley
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-07-01 至 2023-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1906014&HistoricalAwards=false
• 关键词: NSF; BSF; Surface; Sensitive; Spectroscopy

Non-Technical SummarySurface science is the field of elucidating the fundamental aspects of chemistry and physics occurring on the surface of materials with the goal of providing fundamental information to the industrially important fields of catalysis, electrochemistry, corrosion, and lubrication. Classical surface science is carried out in refined conditions of vacuum pressures and very low temperatures; conditions which are almost as empty and cold as outer space. Surface science, as practiced until the end of the 20th century, has provided much of our present understanding of solid surfaces, thanks to an extensive array of surface-sensitive microscopy and spectroscopy techniques, which have revealed the atomic, electronic, and chemical structure of many crystal surfaces. However, real surfaces are always in contact with gases or liquids, and our knowledge of surfaces under such realistic conditions is far less extensive, because only a few experimental techniques can probe surfaces in realistic conditions. This lack of knowledge is referred to as the pressure-temperature gap between surface science and chemical technologies. This project focuses on silver and copper catalysts supported on alumina for ethylene oxidation reaction. This is a commercially important reaction because the annual global demand for ethylene oxide is over twenty five million tons. The merit of this project is not limited to providing an atomic and molecular level understanding of ethylene oxidation reaction, but will also serve as a benchmark, for other fundamental reaction studies. The metal/oxide interface is a highly complex system (multicomponent, multiple interfacial boundaries) and poorly understood, and adds complexity due to presence of environmental reagent gases. The project aims to shift the current paradigm by simultaneously bridging the complexity gap in parallel to the pressure and temperature gaps. Therefore, the project includes developing novel techniques and methods that will be applicable to other metal/oxide systems and other reactant gas admixtures. A measure of its importance is seen in the fact that more than 90% of the catalysts used in the industrial processes are metals supported on oxides. Technical SummaryCatalytic reactions occur typically at high pressures (1 bar) and temperatures (295 K) in most industrial processes compared to the rarefied ultra-high vacuum (UHV) pressures and cryogenic temperatures used in traditional surface science studies. To bridge this pressure gap and temperature gap between science and technology the proposed studies will be performed at 295 K and above, and in the presence of gases in the Torr-bar pressure range, thus approaching the range relevant to industrial production, while avoiding significant sacrifices in terms of measurement resolution and accuracy. This will involve the utilization of microscopy and spectroscopy techniques, namely x-ray photoelectron spectroscopy (XPS), infrared reflection absorption spectroscopy (IRRAS), and scanning tunneling microscopy (STM), that have been specially adapted in the last decades to be performed at ambient pressures. Chemical, atomic, and electronic structure of the Ag/Al2O3 and Cu/Al2O3 metal/oxide surfaces under ethylene epoxidation reaction conditions will be investigated. This commercially important reaction has an annual global volume of 25 billion kg ethylene oxide produced in 2013. Because Al2O3 is a strong dielectric, new tools and methods are introduced in addition to those mentioned above: Freestanding ultra-thin membrane approach, and atomic force microscopy (AFM) imaging and spectroscopy. Combining these four techniques will provide unparalleled mechanistic insights into catalytic reactions occurring on model heterogeneous catalysts, particularly to ethylene epoxidation reaction chosen in this project.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.

表面科学是阐明材料表面化学和物理基本方面的领域，其目标是为催化、电化学、腐蚀和润滑等工业重要领域提供基本信息。经典的表面科学是在真空压力和极低温度的精确条件下进行的;这些条件几乎和外太空一样空旷和寒冷。直到世纪末的表面科学，由于大量的表面敏感显微镜和光谱学技术，揭示了许多晶体表面的原子、电子和化学结构，为我们提供了目前对固体表面的理解。然而，真实的表面总是与气体或液体接触，我们对这种现实条件下的表面的知识远没有那么广泛，因为只有少数实验技术可以探测现实条件下的表面。这种知识的缺乏被称为表面科学和化学技术之间的压力-温度差距。本项目主要研究以氧化铝为载体的银和铜催化剂在乙烯氧化反应中的应用。这是商业上重要的反应，因为环氧乙烷的年全球需求量超过2500万吨。该项目的优点不仅限于提供对乙烯氧化反应的原子和分子水平的理解，而且还将作为其他基础反应研究的基准。 金属/氧化物界面是一个高度复杂的系统（多组分，多个界面边界）和知之甚少，并增加了复杂性，由于环境试剂气体的存在。该项目旨在通过同时弥合压力和温度差距的复杂性差距来改变当前的范式。因此，该项目包括开发适用于其他金属/氧化物系统和其他反应气体混合物的新技术和方法。其重要性的一个衡量标准是，在工业过程中使用的催化剂中，90%以上是负载在氧化物上的金属。在大多数工业过程中，催化反应通常发生在高压（1 bar）和高温（295 K）下，而传统表面科学研究中使用的是稀薄的超高真空（UHV）压力和低温。为了弥合科学和技术之间的压力差距和温度差距，拟议的研究将在295 K及以上的温度下进行，并在Torr-bar压力范围内存在气体，从而接近与工业生产相关的范围，同时避免在测量分辨率和准确性方面的重大牺牲。这将涉及利用显微镜和光谱技术，即X射线光电子能谱（XPS），红外反射吸收光谱（IRRAS）和扫描隧道显微镜（STM），这些技术在过去几十年中已特别适用于在环境压力下进行。将研究在乙烯环氧化反应条件下Ag/Al 2 O3和Cu/Al 2 O3金属/氧化物表面的化学、原子和电子结构。这一具有重要商业意义的反应在2013年全球年产量为250亿kg环氧乙烷。由于Al 2 O3是一种强电介质，因此除了上面提到的那些之外，还引入了新的工具和方法：独立式超薄膜方法，原子力显微镜（AFM）成像和光谱学。结合这四种技术将提供无与伦比的催化反应机理的见解发生在模型多相催化剂，特别是乙烯环氧化反应选择在这个project.This奖项反映了NSF的法定使命，并已被认为是值得的支持，通过评估使用基金会的智力价值和更广泛的影响审查标准。