Environmental Materials Beyond and Below Nanoscale: Palladium Single Atom

在过去的几十年里，纳米技术一直是催化材料和工艺科学进步的主要驱动力。随着材料在纳米尺度上进行工程设计，独特的物理化学和电子性能应运而生。这个项目探索了如果同样的材料在亚纳米尺度上被设计得更小，甚至到“单个原子”会发生什么。单原子催化剂是材料小型化的理论极限，代表了当今材料研究的前沿。单原子催化剂是通过将单个贵金属或过渡金属原子紧密地锚定在载体材料上而合成的。这种结构允许每个原子都可用于催化反应，而不像纳米粒子那样，原子不可避免地被埋在一簇原子中。单原子催化剂对于昂贵的贵金属催化剂特别有吸引力，例如钯，这些催化剂经常被用于环境修复的还原污染物降解过程中。这项研究项目旨在研究如何在原子尺度上控制钯，以最好地利用该材料在与水处理相关的应用中的催化性能。该项目的成功完成将使环境补救解决方案更具成本效益和更可持续。该项目将利用调查员建立的一个外联计划，让当地高中生参与STEM研究。调查员还将为高中教师提供课程。该项目的首要目标是评估钯催化剂在从纳米颗粒缩小到单原子限制时的不同表现。采用各种先进的表征技术，如高能X射线吸收和扫描电子显微镜，可以将钯单原子催化剂材料的性能与合成参数相关联。其他性质，包括原子分散性、局部配位环境和活性金属位置的氧化状态，将进一步与对环境和人类健康构成重大关切的有毒卤代有机化合物和硝酸盐(以及可能存在的其他含氧阴离子，如亚硝酸盐、溴酸盐、铬酸盐和高氯酸盐)的还原去除的催化性能相关。此外，PI将研究钯单原子催化剂在长期使用和复杂的水基质下与纳米颗粒催化剂的不同表现，以评估它们在环境中的命运。参加这个项目的研究生和本科生将获得跨学科的知识，特别是在材料科学、高级光谱学和环境工程的界面上。该项目将利用PI建立的一个外联计划，让当地高中生参与STEM研究。PI还将为高中教师提供课程。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Nanotechnology has been the main driver of scientific advances in catalytic materials and processes over the past few decades. Unique physicochemical and electronic properties emerge as materials are engineered at the nanoscale. This project explores what would happen if the same material were engineered to be even smaller at the sub-nanoscale, even down to the ‘single atom'. Single-atom catalysts are the theoretical limit of material downsizing and represent a frontier of materials research today. Single-atom catalysts are synthesized by tightly anchoring individual noble metal or transition metal atoms onto a support material. This configuration allows every atom to be available for catalytic reaction, unlike nanoparticles in which atoms are inevitably buried inside a cluster of atoms. Single-atom catalysts are is particularly attractive for costly noble metal catalysts, such as palladium, that are often sought in reductive pollutant degradation processes for environmental remediation. This research project seeks to examine how palladium can be controlled at the atomic scale to best exploit the material’s catalytic properties in an application relevant to water treatment. Successful completion of this project will enable more cost-effective and more sustainable environmental remediation solutions. The project will leverage an outreach program that the investigator has established to engage local high school students in STEM research. The investigator will also offer classes to high school teachers. The overarching goal of the project is to evaluate how palladium catalysts behave differently when downsized from nanoparticles to the single atom limit. Palladium single-atom catalyst material properties will be correlated with synthetic parameters by employing various advanced characterization techniques such as high energy X-ray absorption and scanning transmission electron microscopy. Other properties, including atomic dispersion, local coordination environment, and oxidation state of the active metal site, will be further correlated to catalytic performance for the reductive removal of toxic halogenated organic compounds and nitrate (and potentially other oxyanions, such as nitrite, bromate, chromate, and perchlorate) that pose significant environmental and human health concerns. In addition, the PI will investigate how palladium single-atom catalysts behave differently from their nanoparticle counterparts over long-term use and under a complex water matrix to evaluate their environmental fate. Graduate and undergraduate students participating in this project will gain interdisciplinary knowledge, particularly at the interface of materials science, advanced spectroscopy, and environmental engineering. The project will leverage an outreach program that the PI has established to engage local high school students in STEM research. The PI will also offer classes to high school teachers.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.