Atomic Layer-by-Layer Deposition of Pt on Pd Nanocrystals with Well-Controlled Facets

晶面可控的 Pd 纳米晶体上 Pt 原子层沉积

基本信息

批准号：
1505441
负责人：
Younan Xia
金额：
$ 30万
依托单位：
Georgia Tech Research Corporation
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2015
资助国家：
美国
起止时间：
2015-09-01 至 2018-08-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1505441&HistoricalAwards=false
关键词：
Atomic Layer Deposition Pt Pd

项目摘要

In this research project, Dr. Xia of the Georgia Institute of Technology and Dr. Mavrikakis of the University of Wisconsin-Madison are supported by the Macromolecular, Supramolecular and Nanochemistry (MSN) Program to develop platinum-based catalysts with significantly enhanced mass activity toward the oxygen reduction reaction (ORR) critical to the operation of a polymer electrolyte fuel cell. As a clean-energy technology, polymer electrolyte fuel cells are attractive for applications that include on-site power generation and use as a portable power source for transportation vehicles and electronic devices. However, it has been challenging to market this technology on a large scale due to the high cost associated with the platinum catalysts deposited on the cathodes for mitigating the sluggish kinetics of the oxygen reduction reaction (ORR). A reduction of roughly four-fold in platinum loading is needed in order to meet the cost requirement for the large-scale commercialization of this technology. Drs. Xia and Mavrikakis are investigating a new strategy that integrates chemical synthesis and computational modeling for maximizing the mass specific activity of a platinum-based catalyst toward ORR. They are particularly interested in depositing platinum as ultrathin skins of only a few atomic layers thick on palladium nanocrystals. They develop ORR catalysts with enhanced activity by controlling the type of facet (and thus, the arrangement of atoms on the surface) on the palladium (Pd) templates, optimizing the thickness of the platinum (Pt) skin, and maximizing the electronic coupling between the palladium atoms in the core and the platinum atoms in the shell. In addition to the scientific and technological merits, this work helps forge links between different disciplines that include materials chemistry, catalysis, surface science, computational chemistry, colloidal science, and energy technology. It also impacts on our society because it develops novel materials for both fuel cells and catalysis that play a role in energy conversion and environmental protection. The researchers promote diversity in higher education by engaging women, minorities, and other underrepresented groups into this project. By substantially reducing Pt and Pd loadings in catalytic devices, this work helps society achieve a sustainable use for platinum, one of the rarest precious metals that exists in the Earth's crust.In the new catalysts for polymer electrolyte fuel cells, platinum atoms are deposited as conformal shells on the surfaces of palladium nanocrystals pre-synthesized with a uniform size and well-controlled facets. The shell thickness is precisely tuned from one to five atomic layers. Four types of palladium nanocrystals are investigated, including cubes, octahedra, rhombic dodecahedra, and concave cubes, with each one of their surfaces covered by a single type of facet: {100}, {111}, {110}, and high-index ones, respectively. This research involves a unique combination of three approaches: modification of the electronic structure of the platinum surface (and thus, the binding energies of oxygen-containing species) by coupling with the palladium core; development of the most active surface structure by controlling the facet on the palladium core; and replacement of the platinum atoms in the bulk with palladium, a much less expensive metal relative to platinum, to save the materials cost. The outcomes of this research may include enhancement of both graduate and undergraduate education through multidisciplinary and collaborative research; a deep understanding of the heterogeneous nucleation and growth mechanisms involved in the formation of metal nanocrystals; and the development of a novel class of ORR catalysts with an improved performance (activity and durability) to cost ratio when benchmarked against the current commercial catalyst.

在该研究项目中，佐治亚州技术研究所的Xia和威斯康星大学麦迪逊分校的Mavrikakis博士得到了大分子，超分子和纳米化学（MSN）计划，以开发基于铂金的催化剂，具有对牛根降低反应（Orr）的批量生产（Orr）的批量生产（Orr）批量生产的基于铂金的催化作用。作为一种清洁能源技术，聚合物电解质燃料电池对包括现场发电和用作运输车辆和电子设备的便携式电源的应用有吸引力。但是，由于与沉积在阴极上沉积的铂催化剂相关的高成本来减轻氧气减少反应（ORR）的动力学，因此，大规模推销这项技术一直具有挑战性。为了满足该技术大规模商业化的成本要求，需要减少铂金载荷大约四倍。博士。 Xia和Mavrikakis正在研究一种新策略，该策略整合了化学合成和计算建模，以最大化基于铂的催化剂对ORR的质量特异性活性。他们特别有兴趣沉积铂金在钯纳米晶体上仅少量原子层的超薄皮肤。他们通过控制钯（PD）模板上的面部（以及表面上原子的排列）的类型（因此，将原子在表面上的排列）形成增强的活性发展，从而优化铂（PT）皮肤的厚度，并最大程度地提高核心和壳壳壳壳壳中钯原子之间的电子耦合。除了科学和技术优点外，这项工作还有助于不同学科之间建立联系，包括材料化学，催化，表面科学，计算化学，胶体科学和能源技术。它也会影响我们的社会，因为它为燃料电池和催化而开发了新颖的材料，这些材料在能量转化和环境保护中起着作用。研究人员通过使妇女，少数民族和其他代表性不足的群体参与该项目来促进高等教育的多样性。通过实质上减少催化装置中的PT和PD载荷，这项工作有助于社会实现可持续用途的铂，这是地壳中存在的最稀有的贵金属之一。在聚合物电解质燃料电池的新催化剂中，铂原子是在palladium nanocysty nanocysys sys-sys-sys-sys-sys-sys-sys-sys-sys-sys-sys-sys-sys-sys-sys-sys-sys-sys-sys-sys-sys-sys-sys-sys-sys-nanocsons上沉积的。控制良好的方面。壳厚度精确地调整了一个到五个原子层。研究了四种类型的钯纳米晶体，包括立方体，八面体，菱形十二叶胶和凹形立方体，每种表面都被单一类型的刻面覆盖：{100}，{111}，{111}，{110}，{110}和High-Index。这项研究涉及三种方法的独特组合：通过与钯核的耦合，通过铂表面的电子结构（因此，含氧物种的结合能）的修饰；通过控制钯芯上的刻面来发展最活跃的表面结构；并用钯（Palladium）代替铂原子（相对于铂金较便宜得多的金属），以节省材料成本。这项研究的结果可能包括通过多学科和协作研究增强研究生和本科教育；对金属纳米晶体形成涉及的异质成核和生长机制的深入了解；当与当前的商业催化剂基准测试时，开发具有提高性能（活动和耐用性）与成本比的新型ORR催化剂的开发。