UNS:High Surface Free Energy Anchoring of Bimetallic Core Shell Particles

用于当今应用的金属催化剂必须能够在进料组成和温度的极端条件下稳定操作。因此，催化剂的设计和合成变得越来越重要，以确保催化剂颗粒有效地使用昂贵的金属如铂族金属，并在高温和非典型进料组成下保持活性表面。所提出的工作将产生分散在碳催化剂载体上的分散的催化剂颗粒，与单独的活性金属组分相比，该催化剂颗粒在反应条件下具有改善的抗颗粒粗化性。 通过将活性（金、Au）催化剂的表面壳沉积在较高表面自由能核材料（铂（Pt）或各种地球上丰富的过渡金属）的核上来实现颗粒稳定化。这一概念将在Au催化的乙炔与气相盐酸的选择性氢氯化反应中进行测试，以生产氯乙烯（大宗化学品生产的重要中间体）。 初步工作表明，通过将Au沉积在由原子层沉积制备的小Pt簇上，Au颗粒显著稳定。 在本研究中，Pt（核）-Au（壳）纳米粒子将进一步优化，并以更低的成本获得地球上丰富的铜（Cu），镍（Ni），和钴（Co）将被评估为稳定的核心材料。这是一个假设驱动的建议，基于一个简单的想法，即在一个小的核心，壳颗粒可以稳定较低表面能壳材料，否则该壳材料在反应条件下会快速烧结。PI已经获得的数据表明，该概念适用于表面涂有Au（通过原子层沉积制备）的两纳米Pt（核心）颗粒（通过强静电吸附制备）。 进一步的工作将比较均匀的合金，以核-壳催化剂相同的名义组成，也将检查壳的厚度和核心的颗粒大小对乙炔氢氯化活性和耐久性的影响。纳米级多金属颗粒用于改善催化性能和选择性的潜力是催化领域越来越感兴趣的领域，这是对这种催化剂的工作组成和结构的理解。该提案朝着优化反应条件下的可固化催化剂颗粒的结构迈出了重要的一步，着眼于确保在实际高温反应环境中的长期催化剂稳定性。虽然人们对制备含有活性金属纳米簇的负载型催化剂的新方法给予了很大的关注，但很少有研究超越了初始合成和测试，以检查反应条件下的长期稳定性。因此，本提案是对这一领域研究的一个受欢迎的补充，其预期结果可能会影响本文所述的特定催化剂体系之外的广泛催化剂体系。此外，该提议提供了一种基于通过利用成本低的核心组分如Cu、Ni该研究将为研究生和本科生提供机会，利用先进的合成技术参与针对工业应用的研究，这些技术可以潜在地增强广泛的一系列催化过程。

Metallic catalysts for today's applications must be capable of stable operation at extreme conditions of feed compositions and temperatures. Thus, catalyst design and synthesis have become increasingly important to ensure catalyst particles which efficiently use expensive metals such as platinum group metals, and maintain an active surface at high temperatures and atypical feed compositions.The proposed work will create bimetallic catalyst particles dispersed on a carbon catalyst support that have improved resistance to particle coarsening under reaction conditions compared to the active metal component alone. The particle stabilization is achieved by depositing a surface shell of the active (gold, Au) catalyst on a core of a higher surface free energy core material (platinum (Pt), or various earth-abundant transition metals). The concept will be tested in the Au-catalyzed selective hydrochlorination of acetylene with gas-phase hydrochloric acid to produce vinyl chloride (an important intermediate in bulk chemical production). Preliminary work has shown dramatic stabilization of Au particles by depositing the Au on small Pt clusters prepared by atomic layer deposition. In this study, the Pt(core)-Au(shell) bimetallic particles will be further optimized and lower-cost earth-abundant copper (Cu), nickel (Ni), and cobalt (Co) will be evaluated as stabilizing core materials.This is a hypothesis driven proposal based on the simple idea that a higher surface free energy core material in a small core-shell particle can stabilize a lower surface energy shell material that otherwise would sinter rapidly under reaction conditions. The PIs have already obtained data indicating the concept works for two-nanometer Pt(core) particles (prepared by strong electrostatic adsorption) surface-coated with Au (prepared by atomic layer deposition). The further work will compare homogeneous alloys to core-shell catalysts of the same nominal composition, and will also examine the effects of shell thickness and core particle size on acetylene hydrochlorination activity and durability. The potential of nano-scale multi-metallic particles for improved catalytic performance and selectivity is a growing area of interest in catalysis, as is understanding of the working composition and structure of such catalysts. This proposal takes important steps toward optimizing the structure of bimetallic catalyst particles under reaction conditions with an eye toward ensuring long-term catalyst stability in realistic high-temperature reaction environments. Although much attention is being directed towards novel ways of creating supported catalysts containing active metal nano-clusters, few studies have gone beyond initial synthesis and testing to examine long-term stability under reaction conditions. Thus, the present proposal is a welcome addition to research in this area, with expected results that could impact a broad range of catalyst systems beyond the specific ones addressed here. In addition, the proposal offers a route to lower-cost catalysts based on sparing utilization of expensive precious, or noble, active metal components by utilizing core components that are low in cost such as Cu, Ni, and Co. The research will provide opportunities for both graduate and undergraduate students to participate in research directed towards industrial applications utilizing advanced synthesis techniques that can potentially enhance a broad range of catalytic processes.