CAREER: Simulation of Metal Nanoparticle Interactions with Doped Carbon Supports

职业：模拟金属纳米粒子与掺杂碳载体的相互作用

• 批准号: 0747690
• 负责人: Christoffer Turner
• 金额: $ 40万
• 依托单位: University of Alabama Tuscaloosa
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-05-15 至 2014-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0747690&HistoricalAwards=false
• 关键词: CAREER; Simulation; Metal; Nanoparticle; Interactions

0747690TurnerScientific Merit: Many electronic, chemical, and physical properties are known to depend upon system size, especially when the length scale approaches nanometer or sub-nanometer dimensions. This revelation has driven a significant amount of the scientific and engineering research over the past few decades, especially with regards to electronic materials, biological processes, and catalysis. With regards to catalysis, it is recognized that the activity of a catalyst is not a pure function of its surface area. In fact, as the size of the catalyst shrinks, the catalyst behaves less like a bulk metal, and characteristics such as the morphology of the particles and the nature of the support begin to play a significant role.The primary goal of a catalyst search is to identify materials with specific chemical activity. However, a secondary goal is for the catalyst to maintain its activity during reacting conditions, which may include high temperatures, high or low pH, interactions with adsorbates, or the presence of an electrical current in electrochemical applications. Harsh reacting conditions may quickly result in a loss of chemical activity, due to catalyst poisoning, sintering, or dissolution of the catalyst or its support material. In order to maintain activity, these detrimental processes must be mitigated, either by tightly controlling the reaction conditions or by altering the intrinsic properties of the catalyst/support material. As such, a computational investigation will be performed to understand how the interactions between metal clusters and carbon support materials might be manipulated in order to preserve or enhance catalyst function.This project is built upon the premise that catalyst sintering is (in part) related to the interaction of the catalyst with its support material. There are two primary mechanisms that are used to describe the sintering process: coalescence and Ostwald ripening. Since both processes involve the diffusion of the catalyst particles on the support (either as single atoms or as clusters), the catalyst stability should be significantly improved by reducing the inherent mobility of the catalysts. In other words, if the particles are somehow pinned or anchored to the support, sintering should decrease. This is the route that will be explored here. Attention will be focused on the interactions of Pt, Pd, Ru, Rh, and Au metal atoms and clusters with (doped) carbon supports. These metal/support combinations can be found in a wide range of catalytic and electrochemical applications in industry, including fuel cell catalysis, decarbonylation reactions, reductive amination, alcohol synthesis, etc. Due to the high price (and limited quantities) of these precious metals, it is particularly important to maintain their original activity under reacting conditions for extended periods of time. This is one of the central challenges of catalysis.The modeling will be primarily performed using electronic structure calculations to predict a variety of physical and chemical properties of the metal/support systems. In particular, characterization of the structure and activity of Pt, Pd, Ru, Rh, and Au catalyst particles on pristine and doped carbon supports will be performed. Various dopant schemes will be investigated, and these will be compared with typical carbon support chemistry (carboxyl groups, hydroxyl groups, Stone-Wales defects, etc.). Along with this, the propensity of the catalyst particles for sintering, as a function of temperature and as a function of electric field strength (pertinent to electrochemical applications) will be investigated with ab initio MD simulations. Finally, the metal particles will be analyzed with respect to their catalytic activity by calculating the reaction mechanisms of standard probe reactions, such as CO oxidation.Broader Impacts: The education and outreach plan has been given significant attention, and a high impact strategy has been developed for disseminating the science outcomes. The outreach activities involve K-12 students by partnering with the McWane Science Center in Birmingham, AL to create a new science exhibit. Also, undergraduate students will participate in this project through the UA Computer Based Honors Program. Finally, faculty at HBCU programs will be included in summer workshops, as well as other audiences through the more traditional avenues (graduate courses, conference presentations, and journal publications).

0747690 Turner科学优点：许多电子，化学和物理特性都取决于系统的大小，特别是当长度尺度接近纳米或亚纳米尺寸。在过去的几十年里，这一发现推动了大量的科学和工程研究，特别是在电子材料、生物过程和催化方面。关于催化，人们认识到催化剂的活性不是其表面积的纯函数。事实上，随着催化剂尺寸的缩小，催化剂的行为就不像块体金属，而颗粒的形态和载体的性质等特征开始起着重要的作用。催化剂搜索的主要目标是识别具有特定化学活性的材料。然而，第二目标是催化剂在反应条件期间保持其活性，所述反应条件可包括高温、高或低pH、与吸附物的相互作用或电化学应用中电流的存在。由于催化剂中毒、烧结或催化剂或其载体材料的溶解，苛刻的反应条件可能迅速导致化学活性的损失。为了保持活性，必须通过严格控制反应条件或通过改变催化剂/载体材料的固有性质来减轻这些有害过程。因此，将进行计算研究，以了解金属簇和碳载体材料之间的相互作用可能被操纵，以保持或增强催化剂的功能。该项目是建立在催化剂烧结（部分）与催化剂与其载体材料的相互作用有关的前提下。有两种主要机制用于描述烧结过程：聚结和奥斯特瓦尔德熟化。由于这两种方法都涉及催化剂颗粒在载体上的扩散（作为单个原子或作为簇），因此催化剂稳定性应通过降低催化剂的固有流动性来显著改善。换句话说，如果颗粒以某种方式固定或锚定在支撑物上，则烧结应该减少。这就是我们将要探索的道路。注意力将集中在Pt，Pd，Ru，Rh和Au金属原子和簇与（掺杂）碳载体的相互作用。这些金属/载体组合可以在工业中广泛的催化和电化学应用中找到，包括燃料电池催化、脱羰基反应、还原胺化、醇合成等。由于这些贵金属的高价格（和有限的数量），在反应条件下长时间保持其原始活性特别重要。这是催化的核心挑战之一。建模将主要使用电子结构计算来预测金属/载体系统的各种物理和化学性质。特别地，将进行Pt、Pd、Ru、Rh和Au催化剂颗粒在原始和掺杂的碳载体上的结构和活性的表征。将研究各种掺杂剂方案，并将其与典型的碳载体化学（羧基、羟基、斯通-威尔士缺陷等）进行比较。沿着，催化剂颗粒的烧结倾向，作为温度的函数和作为电场强度的函数（与电化学应用有关），将用从头算MD模拟研究。最后，通过计算CO氧化等标准探针反应的反应机理，对金属粒子的催化活性进行分析。更广泛的影响：教育和推广计划受到了高度重视，并制定了一项高影响战略，以传播科学成果。外展活动涉及K-12学生与麦克韦恩科学中心在伯明翰，AL合作，创造一个新的科学展览。此外，本科生将通过UA基于计算机的荣誉计划参与该项目。最后，HBCU课程的教师将参加夏季研讨会，以及其他观众通过更传统的途径（研究生课程，会议演示和期刊出版物）。