Surface Composition and Chemical Behavior of Supported Single-Atom Alloy (SAA) Nanoparticles under Catalytic Conditions

催化条件下负载型单原子合金 (SAA) 纳米颗粒的表面组成和化学行为

• 批准号: 2244925
• 负责人: Francisco Zaera
• 金额: $ 59.44万
• 依托单位: University of California-Riverside
• 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: 2023-07-01 至 2026-06-30
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2244925&HistoricalAwards=false
• 关键词: Surface; Composition; Chemical; Behavior; Supported

With the support of the Chemical Catalysis program in the Division of Chemistry, Professor Francisco Zaera of the University of California, Riverside is studying the chemical behavior of so-called single atom alloy (SAA) catalysts. Catalysis is used extensively in industry to manufacture chemicals, and transition metals are in many instances the key components of the catalysts used. To tune the properties of metal catalysts to optimize catalytic performance, alloys of two or more metals are sometimes used. In recent years, much interest has developed in using a particular version of metal alloys, SAAs, as catalysts where a small amount of one metal, e.g. platinum (Pt) in the Zaera lab, is dispersed on nanoparticles (NPs) of a second (Cu) to add specific new functionality. In the case of hydrocarbon hydrogenations, a family of important catalytic processes where hydrogen atoms (H) are added to carbon-carbon or carbon-oxygen multiple bonds, research using model systems has suggested that the Pt atoms are needed to dissociate H2 to provide the required H atoms. However, preliminary studies under realistic catalytic conditions have indicated that the behavior of the single atoms may be more nuanced. This project focuses on characterizing the nature of the surfaces of SAA catalysts under catalytic conditions to better understand the behavior of the minority (Pt) and majority (Cu) metals and their contributions to hydrogenation catalysis to improve catalytic performance. The knowledge derived from this work is aimed to help tune the selectivity of processes for the industrial production of fine chemicals. The knowledge derivied from this work will also be useful for educational purposes, by providing data to illustrate basic principles in kinetics, catalysis, and NP synthesis in undergraduate and graduate classes. Collaborations with Latin American research groups are being forged, and student participation from groups underrepresented in research is being pursued.In these studies, Professor Francisco Zaera of the University of California, Riverside is studying the surface composition and chemical behavior of supported SAA nanoparticles (NPs) under catalytic conditions. The main objective of this project is to characterize SAA catalysts in situ or under operando conditions (while carrying out catalytic processes) to bridge the pressure and materials gaps and better understand their working surface chemistry. Two hypotheses underpin this proposal: (1) that the minority metal (Pt) may diffuse into the bulk under reaction conditions and influence catalysis in a remote way (a direct consequence of the pressure gap); and (2) that such environment-induced metal diffusion may occur under different conditions in supported NPs vs. in bulk materials (a direct manifestation of the materials gap). Three parallel experimental approaches are being followed to test the key hypotheses. First, kinetic measurements under catalytic conditions are being performed on model systems by using a so-called "high-pressure cell" and complemented and correlated with results from in situ characterization of the surface using reflection-absorption infrared spectroscopy (RAIRS). Second, synthetic methods are being developed to make well mixed diluted alloys and core-shell bimetallic NPs to investigate the possible diffusion and intermixing of the metals under reaction conditions. Third, catalysts are being characterized under catalytic conditions in situ and under operando conditions by X-ray absorption spectroscopy (XAS) to evaluate changes in the coordination sphere around the minority atoms, one way to determine their presence on the surface vs. inside the bulk, and by infrared absorption spectroscopy (IR), to extract information about the adsorption mode of the reactants and to titrate the minority atoms available at the surface under catalytic conditions. The proposal combines studies with model systems, new catalyst synthesis methodology, in situ spectroscopic studies of catalysts, and quantum mechanics calculations to answer a critical question; namely, the effect of the pressure and materials gaps on SAA performance, with wide-ranging implications to the field of catalysis.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，加州大学河滨分校的Francisco Zaera教授正在研究所谓的单原子合金（SAA）催化剂的化学行为。催化作用广泛用于工业生产化学品，过渡金属在许多情况下是所用催化剂的关键成分。为了调整金属催化剂的性质以优化催化性能，有时使用两种或两种以上金属的合金。近年来，人们对使用一种特殊版本的金属合金（SAAs）作为催化剂产生了浓厚的兴趣，在这种催化剂中，少量的一种金属，例如Zaera实验室的铂（Pt），分散在另一种金属（Cu）的纳米颗粒（NPs）上，以增加特定的新功能。碳氢化合物氢化反应是一系列重要的催化过程，其中氢原子(H)被添加到碳-碳或碳-氧多键中，使用模型系统的研究表明，Pt原子需要解离H2以提供所需的H原子。然而，在现实催化条件下的初步研究表明，单原子的行为可能更加微妙。本项目重点研究SAA催化剂在催化条件下的表面性质，以更好地了解少数金属（Pt）和多数金属（Cu）的行为及其对加氢催化的贡献，从而提高催化性能。从这项工作中获得的知识旨在帮助调整精细化学品工业生产过程的选择性。从这项工作中获得的知识也将有助于教育目的，通过提供数据来说明动力学，催化和NP合成在本科和研究生课程中的基本原理。正在与拉丁美洲研究小组建立合作关系，并且正在争取来自在研究中代表性不足的群体的学生参与。在这些研究中，加州大学河滨分校的Francisco Zaera教授正在研究催化条件下负载SAA纳米颗粒（NPs）的表面组成和化学行为。该项目的主要目标是在原位或操作条件下（在进行催化过程时）表征SAA催化剂，以弥合压力和材料的差距，并更好地了解其工作表面化学性质。有两个假设支持这一建议：(1)在反应条件下，少数金属（Pt）可能扩散到体中，并以一种遥远的方式影响催化（压力间隙的直接后果）；(2)在不同的条件下，这种环境诱导的金属扩散可能发生在负载的NPs和块状材料中（材料间隙的直接表现）。研究人员采用了三种平行的实验方法来验证关键假设。首先，使用所谓的“高压电池”对模型系统进行催化条件下的动力学测量，并与使用反射-吸收红外光谱（RAIRS）对表面进行原位表征的结果进行补充和关联。其次，开发了制备混合良好的稀释合金和核壳双金属NPs的合成方法，以研究金属在反应条件下可能的扩散和混合。第三，通过x射线吸收光谱（XAS）在原位催化条件和操作氧条件下对催化剂进行表征，以评估少数原子周围配位球的变化，这是确定它们在表面和内部存在的一种方法；通过红外吸收光谱（IR），提取有关反应物吸附模式的信息，并滴定催化条件下表面可用的少数原子。该提案结合了模型系统的研究，新的催化剂合成方法，催化剂的原位光谱研究和量子力学计算来回答一个关键问题；即压力和材料间隙对SAA性能的影响，对催化领域具有广泛的影响。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

Acrolein Hydrogenation Catalyzed by Pt(111): Effect of Carbonaceous Deposits on Kinetics

• DOI: 10.1021/acscatal.3c03870
• 发表时间: 2023-10
• 期刊: ACS Catalysis
• 影响因子: 12.9
• 作者: Mindika Tilan Nayakasinghe;Yang Xu;F. Zaera