Collaborative Research: Structure, Dynamics, and Catalysis with Dilute Bimetallic and Single Atom Alloy Nanoparticles

合作研究：稀双金属和单原子合金纳米粒子的结构、动力学和催化作用

• 批准号: 2300021
• 负责人: Ayman Karim
• 金额: $ 18.26万
• 依托单位: Virginia Polytechnic Institute and State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-06-01 至 2026-05-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2300021&HistoricalAwards=false
• 关键词: Collaborative; Research; Structure; Dynamics; Catalysis

With support from the Chemical Catalysis program in the Division of Chemistry, David Flaherty (Georgia Institute of Technology), David HIbbitts (University of Florida), and Ayman Karim (Virginia Polytechnical Institute) will examine the connections among the structure, dynamics, and catalysis of reactions with oxygen on bimetallic nanoparticles. The team will create, characterize, simulate, and test how atoms of distinct metals move and facilitate reactions upon the surfaces of nanoparticles comprised primarily of gold with small amounts (1-5%) of a second element such as palladium or platinum. These materials are commonly described as single atom alloy (SAA) catalysts. These materials offer high rates and selectivities for numerous reactions important for domestic production of energy carriers and platform chemicals (e.g., valorization of biomass, shale gas, operation of fuel cells and electrolyzers). SAA currently suffer from a distressingly low number of active sites per gram of precious metal used. The collaborative team aims to develop methods to create SAA nanoparticles with smaller diameters ( 2 nm) to remedy this problem, and then test if the emergent and beneficial catalytic properties of these SAA are preserved as the size of the nanoparticles decreases. Here, the team will combine cutting-edge methods in quantum chemical simulations and multiscale modeling, characterization of operating catalysts using synchrotron methods, and catalyst testing and spectroscopy to learn how the nanoparticles restructure in different combinations of reactive gases relevant for catalysis (e.g., oxygen, hydrogen, carbon monoxide). Subsequently, the team will assess how rates and selectivities for a testbed reaction (reduction of oxygen with hydrogen) depend on the spatial organization of the atoms on the nanoparticle surface. Methods that will be developed will be useful for other dynamic catalyst systems and will be integrated into graduate-level courses. The proposed work involves lab-based education of graduate and undergraduate students and focused efforts to increase participation of women in catalysis science, especially with NSF REU (Research Experiences for Undergraduates) opportunities and cross-training of researchers across the three partnering institutions.Under this award, the collaborative Flaherty/Hibbitts/Karim team aims to learn how the structure, dynamics, and catalytic properties of bimetallic and SAA materials depend upon mean particle diameters, composition, and support identity, all factors that impact the coordinative saturation of surface atoms and the identity of their nearest and next-nearest neighbor atoms. The team will couple precise synthesis, advanced characterization techniques (including n situ, operando X-ray absorption spectroscopy, microcalorimetry, infrared spectroscopy), and computational methods (simulations of full nanoparticles with density functional theory and kinetic Monte Carlo) to address the complexity and dynamics of SAA catalysts. A testbed reaction system with rates and selectivities proven to be structure-sensitive with respect to these materials (H2 + O2 → H2O2) will be used to probe the surface structures of active catalysts, a challenge as the high pressures and complex solvents used often render characterization difficult. First, Au-rich bimetallic alloy nanoparticles (i.e., M1Aux materials, where M = Pd, Pt, Rh) with mean diameters of 1-2, ~6 and ~10 nm will be created, their post-synthesis structures will be characterized, and then the influence of adsorption and reactions on their structures will be examined over extended periods. Second, the thermodynamic relationships among adsorption energies, active site motifs, and nanoparticle structure will be determined. Third, the fundamental connections surrounding elemental identity, mole fraction, and coordination of the reactive metal and reaction rates, selectivities and barriers for H2O2 and H2O formation will be examined.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.

在化学系化学催化项目的支持下，David Flaherty（乔治亚理工学院）、David HIbbitts（佛罗里达大学）和 Ayman Karim（弗吉尼亚理工学院）将研究结构、动力学和催化之间的联系该团队将创建、表征、模拟和测试不同金属的原子如何移动并促进纳米粒子表面上的反应。主要由金和少量 (1-5%) 的第二种元素（如钯或铂）组成。这些材料通常被称为单原子合金 (SAA) 催化剂，这些材料为国内重要的许多反应提供高速率和选择性。能源载体和平台化学品的生产（例如生物质、页岩气的增值、燃料电池和电解槽的运行）目前每克贵金属的活性位点数量极少。该合作团队旨在开发制造更小直径（2 nm）的 SAA 纳米颗粒的方法来解决这个问题，然后测试随着纳米颗粒尺寸的减小，这些 SAA 的新兴和有益的催化特性是否得以保留。该团队将结合量子化学模拟和多尺度建模中的尖端方法、使用同步加速器方法表征操作催化剂以及催化剂测试和光谱学，以了解纳米颗粒如何在不同的组合中重组。随后，该团队将评估试验台反应（用氢还原氧气）的速率和选择性如何取决于纳米颗粒表面原子的空间组织。将开发的方法将适用于其他动态催化剂系统，并将被纳入研究生课程中。拟议的工作涉及研究生和本科生的实验室教育，并重点努力增加女性对催化科学的参与，特别是在催化科学领域。 NSF REU（本科生研究经验）机会以及对三个合作机构的研究人员进行交叉培训。在该奖项下，Flaherty/Hibbitts/Karim 合作团队旨在了解双金属和 SAA 材料的结构、动力学和催化性能取决于平均粒子颗粒、成分和载体特性，所有影响表面原子的配位饱和度以及其最近和次近邻直径原子的特性的因素该团队将精确耦合。合成、先进的表征技术（包括原位、原位 X 射线吸收光谱、微量热法、红外光谱）和计算方法（利用密度泛函理论和动力学蒙特卡罗模拟全纳米粒子）来解决 SAA 催化剂的复杂性和动力学问题。试验台反应系统的速率和选择性被证明对这些材料（H2 + O2 → H2O2）具有结构敏感性，将用于探测活性催化剂的表面结构，这是一个挑战，因为使用的高压和复杂溶剂通常使表征变得困难，首先，平均直径为 1-2、~6 和~的富金双金属合金纳米粒子（即 M1Aux 材料，其中 M = Pd、Pt、Rh）。将创建 10 nm，对其合成后结构进行表征，然后在较长时间内检查吸附和反应对其结构的影响。其次，吸附能之间的热力学关系，第三，将确定反映周围元素特性、摩尔分数和活性金属配位的基本联系，以及 H2O2 和 H2O 形成的反应速率、选择性和障碍。该奖项是 NSF 的法定奖项。使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。