Rethinking the Reactivity of Nanoscale Metal Oxides

重新思考纳米级金属氧化物的反应性

• 批准号: 1904813
• 负责人: James Mayer
• 金额: $ 46.5万
• 依托单位: Yale University
• 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: 2019-09-01 至 2024-02-29
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1904813&HistoricalAwards=false
• 关键词: Rethinking; Reactivity; Nanoscale; Metal; Oxides

Metal-oxide materials are widespread, from rocks in the environment, to components of fuel cells, to ingredients in sunscreens. These materials are increasingly used as very small particles (nanoparticles - particles that are a billionth of a meter in diameter). The behavior and use of nanoparticles often change after adding or removing just a few atoms. In this research project, Professor Mayer's group at Yale University is studying how and why hydrogen (H) and oxygen (O) atoms move onto and out of metal oxide nanoparticles. Hydrogen and oxygen are ubiquitous, as they are in water (H2O), in air (O2) and in hydrocarbon fuels like gasoline. Understanding how metal oxides use or provide H and O could lead to new ideas and perhaps the development of new technologies. The development of young scientists and the engagement of the broader community are intertwined goals of this project. Public lectures are planned and a short classroom program is being developed. Professor Mayer and his team also prepare week-long workshops and month-long internships are being offered. These activities emphasize hands-on and discovery-based activities to engage a diverse group of high school students, especially those from groups currently under-represented in STEM fields. Redox (oxidation/reduction) reactions of metal oxide nanocrystals (MOx NCs) are typically described as outer-sphere electron transfer processes. However, there is increasing evidence that many, if not most, of these interfacial reactions are actually inner-sphere processes, involving the making and breaking of O-H and M-O chemical bonds. Reactions involving O-H bonds of oxide materials can be described as proton-coupled electron transfer or hydrogen atom transfer. Proton-coupled electron transfer to a MOx NC involves protonation of an oxide to a hydroxide and addition of an electron to a band state or trap state. The inner-sphere redox reactivity of a variety of MOx NCs is being studied, including the n-type semiconductors TiO2 and CeO2-x, p-type NiO and metallic RuO2. Oxygen atom transfer reactions are also being explored. These reactions are not yet well established for NC/solution interfaces. The experiments take a molecular approach, utilizing tools from both solution chemistry and materials research. For example, the nanocrystals are reacted with molecular substrates known to undergo hydrogen atom transfer and oxygen atom transfer. The hydrogen atom transfer reactions are providing thermochemical information, which is assembled into a novel hydrogen-atom affinity scale for nanocrystals. The kinetics of the reactions are correlated with the thermochemical driving forces to examine rate vs. driving force scaling relationships. Parallel studies of hydrogen atom transfer and oxygen atom transfer reactions show the connections between these basic reaction types. These fundamental studies of individual reaction steps build a potentially transformative new paradigm for nanomaterial reactivity, rooted in thermochemistry and kinetics.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.

金属氧化物材料广泛存在，从环境中的岩石到燃料电池的成分，再到防晒霜的成分。这些材料越来越多地被用作非常小的颗粒（纳米颗粒-直径为十亿分之一米的颗粒）。添加或删除几个原子后，纳米粒子的行为和用途往往会发生变化。在这个研究项目中，耶鲁大学梅尔教授的团队正在研究氢(H)和氧(O)原子如何以及为什么进入和离开金属氧化物纳米粒子。氢和氧无处不在，它们存在于水（H2O）、空气（O2）和碳氢化合物燃料（如汽油）中。了解金属氧化物是如何利用或提供氢和氧的，可能会带来新的想法，也许还会带来新技术的发展。青年科学家的发展和更广泛的社会参与是这个项目相互交织的目标。计划进行公开讲座，并正在制定一个短期课堂方案。梅尔教授和他的团队还准备了为期一周的研讨会，并提供了为期一个月的实习机会。这些活动强调实践和基于发现的活动，以吸引不同群体的高中生，特别是那些目前在STEM领域代表性不足的群体。金属氧化物纳米晶体（moxncs）的氧化还原（氧化/还原）反应通常被描述为外球电子转移过程。然而，越来越多的证据表明，这些界面反应中的许多（如果不是大多数的话）实际上是球体内部过程，涉及O-H和M-O化学键的形成和断裂。涉及氧化材料O-H键的反应可以描述为质子耦合电子转移或氢原子转移。质子耦合电子向MOx NC的转移包括氧化物质子化成氢氧化物和电子加入带态或陷阱态。研究了n型半导体TiO2和CeO2-x、p型NiO和金属RuO2等多种MOx纳米材料的球内氧化还原活性。氧原子转移反应也在探索中。这些反应还没有很好地建立在NC/溶液界面上。实验采用分子方法，利用溶液化学和材料研究的工具。例如，纳米晶体与已知经历氢原子转移和氧原子转移的分子底物反应。氢原子转移反应提供了热化学信息，这些信息被组装成纳米晶体的新型氢原子亲和尺度。反应动力学与热化学驱动力相关联，以检验速率与驱动力的标度关系。对氢原子转移和氧原子转移反应的平行研究表明了这些基本反应类型之间的联系。这些对单个反应步骤的基础研究为纳米材料的反应性建立了一个潜在的变革性的新范式，植根于热化学和动力学。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。

项目成果

Coverage-Dependent Rate-Driving Force Relationships: Hydrogen Transfer from Cerium Oxide Nanoparticle Colloids

• DOI: 10.1021/jacs.2c07988
• 发表时间: 2022-11-02
• 期刊: JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
• 影响因子: 15
• 作者: Agarwal, Rishi G.;Mayer, James M.
• 通讯作者: Mayer, James M.

Cooperation of cerium oxide nanoparticles and soluble molecular catalysts for alcohol oxidation

• DOI: 10.1039/c9qi01640f
• 发表时间: 2020-03-21
• 期刊: INORGANIC CHEMISTRY FRONTIERS
• 影响因子: 7
• 作者: Laga, Stephanie M.;Townsend, Tanya M.;Mayer, James M.
• 通讯作者: Mayer, James M.