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

当今应用的金属催化剂必须能够在进料成分和温度的极端条件下稳定运行。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。所提出的工作将创造分散在碳催化剂载体上的双金属催化剂颗粒，与单独的活性金属成分相比，在反应条件下具有更好的抗颗粒粗化能力。粒子稳定是通过将活性（金，金）催化剂的表面壳层沉积在表面自由能更高的核心材料（铂（Pt）或各种地球上丰富的过渡金属）的核心上来实现的。该概念将在金催化的乙炔气相盐酸选择性氯化氢反应中进行测试，以生产氯乙烯（散装化学品生产中的重要中间体）。初步研究表明，通过原子层沉积法制备的小铂团簇上沉积金，金粒子具有显著的稳定性。在本研究中，将进一步优化Pt（芯）-Au（壳）双金属颗粒，并评估低成本的地球富集铜（Cu），镍（Ni）和钴（Co）作为稳定芯材料。这是一个假设驱动的提议，基于一个简单的想法，即小核壳粒子中的高表面自由能的核心材料可以稳定低表面能的壳材料，否则在反应条件下会迅速烧结。pi已经获得的数据表明，该概念适用于两纳米Pt（核心）颗粒（通过强静电吸附制备）表面涂有Au（通过原子层沉积制备）。进一步的工作将比较均质合金与相同标称成分的核-壳催化剂，并将研究壳厚度和核粒径对乙炔氢氯化活性和耐久性的影响。纳米级多金属颗粒在改善催化性能和选择性方面的潜力，以及对这种催化剂的工作成分和结构的理解，是催化领域中一个日益增长的兴趣领域。这一提议在优化反应条件下双金属催化剂颗粒结构方面迈出了重要的一步，着眼于确保催化剂在现实高温反应环境中的长期稳定性。尽管许多人都在关注创造含有活性金属纳米团簇的负载催化剂的新方法，但很少有研究超越了最初的合成和测试，以检查反应条件下的长期稳定性。因此，目前的建议是对该领域研究的一个受欢迎的补充，预期的结果可能会影响广泛的催化剂系统，而不仅仅是这里所讨论的特定系统。此外，该提案还提供了一种低成本催化剂的途径，通过使用低成本的核心成分（如Cu， Ni和Co），节省使用昂贵的贵重或高贵的活性金属成分。该研究将为研究生和本科生提供机会，参与利用先进合成技术的工业应用研究，这些技术可以潜在地增强广泛的催化过程。

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.