SusChEM: Sustainable Synthesis of Bismuth-Based Core-Shell Nanoparticles for Alternative Energy Applications

非技术总结：尽管几十年来在可再生、环境安全和高效发电方面做出了承诺，但氢和酒精燃料电池的实际实现仍然遥不可及。今天上路的为数不多的燃料电池动力汽车得到制造商的巨额补贴的主要原因是，还没有找到合适的替代昂贵的金属铂大宗催化剂。这项研究试图通过将铂限制在实际需要的最顶层原子层来最大限度地减少铂的使用。为了实现这一点；将了解物质如何从由单个金属原子簇组成的初始状态转变为组成催化活性金属的最终纳米晶态。在这种小尺寸范围内表现出的新的物理特性不仅可以用于燃料电池的电催化，还可以用于氧化还原液流电池(RFB)和热电发电(TPG)等新兴技术。该项目的教育方面旨在：(I)通过与当地高中的倡议，加强大学前教育和少数群体的宣传。(2)用新的实验室单元更新化学工程课程，结合可持续能源技术的最新进展。(Iii)在专业学会(AICHE，ACS)中引入本科生跨学科活动。技术摘要：这项研究的主要目标是开发安全、可持续和可扩展的化学合成，以生产以铋为核心成分的金属纳米颗粒(NPs)。铋是一种富含稀土的元素，具有低毒和水稳定性，在清洁、高效的发电中尚未被开发来提高材料的耐用性。铋的高贵特性使其成为氧还原反应(ORR)和燃料氧化(氢、醇等)所需的贵金属电催化剂的有吸引力的载体。质子交换膜燃料电池(PEMFC)。贵金属在催化中的最有效利用是通过它们在分散的贱金属NP核上的表面偏析来实现的，从而使它们的表面积与体积比最大化。以前在该领域使用除铋以外的金属(例如，镍、钴和铁)来实施这一策略的尝试由于它们在燃料电池环境中的溶解而失败。此外，由于使用有毒的有机溶剂、难以合成的有机前体以及危险的联氨或锂还原剂，已证明难以形成BiNP。与该领域以前的研究结果形成直接对比的是，本研究将考察在SnCl2同时用作表面活性剂和还原剂的情况下，用于纳米颗粒生长的全水、全无机合成工艺。众所周知，铋在形成SnCl3表面活性剂所需的高盐、低pH环境中不稳定，因此，这些胶体合成路线是意想不到的。以前，SnCl3-配体结合到铋上的可能性还没有被认识到。因此，我们使用这种独特的无机配体方法合成铋铂纳米粒子的初步成功是非常令人惊讶的。为了更全面地了解这些现象，我们将利用时间分辨、原位X射线和119SnMössbauer谱对纳米粒子进行详细的实验表征，以研究纯铋和铋合金纳米粒子的形成动力学和SnCl3-配体壳层从初始络合物的演化。

NON-TECHNICAL SUMMARY: Despite decades of promise regarding renewable, environmentally safe, and highly efficient power generation, the practical realization of hydrogen and alcohol-powered fuel cells remains elusive. The main reason that the few fuel cell powered vehicles on the road today are heavily subsidized by manufacturers is that a suitable replacement for expensive metal Pt bulk catalyst has yet to be identified. The research effort seeks to minimize the use of Pt by confining it to only the topmost atomic layers where it is actually needed. To achieve this; understanding of how matter transitions from an initial state consisting of clusters of individual metal atoms to the final nanocrystalline state of which catalytically active metals are composed will be developed. New physical properties manifested at this small size range can be harnessed not only for fuel cell electrocatalysis, but for emergent technologies such as redox flow batteries (RFBs) and thermoelectric power generation (TPGs). The educational aspect of this project aims to: (i) Enhance pre-college education and minority outreach via initiatives with local high schools. (ii) Upgrade chemical engineering curriculum with new laboratory modules that integrate recent progress in sustainable energy technology. (iii) Introduce undergraduate cross-disciplinary activities within professional societies (AIChE, ACS).TECHNICAL SUMMARY:The primary objective of this research is to develop safe, sustainable, and scalable chemical syntheses that produce metal nanoparticles (NPs) having bismuth as their core component. Bi is an earth-abundant element with low toxicity and water-stability that has yet to be exploited to enhance material durability in clean, efficient power generation. The noble character of Bi makes it an attractive support for precious metal electrocatalysts required for both the oxygen reduction reaction (ORR) and fuel oxidation (hydrogen, alcohol, etc.) in proton exchange membrane fuel cells (PEMFCs). The most efficient use of precious metals in catalysis is achieved by their surface segregation on dispersed NP cores of base metals so as to maximize their surface to volume ratio. Prior attempts in the field to implement this strategy with metals other than Bi (e.g., Ni, Co, and Fe) have failed due to their dissolution in the fuel cell environment. In addition, Bi NP formation has proven difficult due to the use of toxic organic solvents, difficult-to-synthesize organic precursors, and dangerous hydrazine or lithium reducing agents. In direct contrast to prior results in the field; this research will examine all-aqueous, all-inorganic synthesis processes for the growth of NPs in which SnCl2 is used as a simultaneous surfactant and reducing agent. Bi is well known to be unstable in the high salt, low pH environment required for SnCl3- surfactant formation and therefore, these colloidal synthesis routes are unexpected. Previously, the potential for SnCl3- ligand attachment to Bi has not been recognized. Consequently, our initial successes with Bi-Pt NP synthesis using this unique inorganic ligand approach were very surprising. To more fully understand these phenomena, detailed experimental characterization of the NPs will be conducted using time-resolved, in-situ X-ray and 119Sn Mössbauer spectroscopies to study the kinetics of pure Bi and Bi-alloy NP formation and SnCl3- ligand shell evolution from the initial complex.