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

非技术总结：尽管几十年来人们一直对可再生、环保、高效的发电方式充满希望，但氢和酒精燃料电池的实际实现仍然难以捉摸。目前道路上为数不多的燃料电池汽车得到制造商的大量补贴，主要原因是尚未找到一种合适的替代品来替代昂贵的金属Pt散装催化剂。这项研究旨在通过将其限制在实际需要的最顶层原子层来最大限度地减少Pt的使用。为了达到这个目的;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由催化活性金属组成的最终纳米晶体状态将得到发展。在如此小的尺寸范围内表现出的新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（TPGs）等新兴技术。这个项目的教育方面的目的是：(i)通过与当地高中的倡议加强大学前教育和少数民族外联。改进化学工程课程，采用新的实验室单元，结合可持续能源技术的最新进展。（三）在专业学会（AIChE， ACS）内开展本科生跨学科活动。技术概述：本研究的主要目标是开发安全、可持续和可扩展的化学合成方法，以生产以铋为核心成分的金属纳米颗粒（NPs）。铋是一种富含地球的元素，具有低毒和水稳定性，尚未被用于提高材料在清洁、高效发电中的耐久性。铋的高贵特性使其成为质子交换膜燃料电池（pemfc）中氧还原反应（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。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核上的表面分离来实现的，从而最大化它们的表面体积比。在此之前，对Bi以外的金属（如Ni、Co和Fe）实施这一策略的尝试失败了，因为它们在燃料电池环境中会溶解。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肼或锂还原剂，Bi NP的形成已被证明是困难的。与该领域先前的结果直接相反；本研究将考察SnCl2同时作为表面活性剂和还原剂的全水、全无机NPs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环境中是不稳定的，因此，这些胶体合成途径是意想不到的。以前，SnCl3-配体附着于Bi的潜力尚未被认识到。因此，我们使用这种独特的无机配体方法合成Bi-Pt NP的初步成功是非常令人惊讶的。为了更充分地理解这些现象，将使用时间分辨、原位x射线和119Sn Mössbauer光谱对NPs进行详细的实验表征，以研究纯Bi和Bi合金NP形成和SnCl3-配体壳从初始配合物演化的动力学。

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.