Design and Synthesis of Metallic Nanoparticle Interfaces for Enhancing Thermal Stability and Catalytic Behavior

纳米材料提供了新的机会来加强技术上重要的过程，如控制污染物，重组先进的燃料来源，以及实现清洁和高效的能源转换。高温应用，然而，可以限制纳米材料的效用，由于高颗粒迁移率和烧结过程。在材料研究部固态和材料化学项目的支持下，该项目通过将金属纳米颗粒与新工程材料固定在陶瓷基板上，解决了高温颗粒不稳定性和纳米颗粒催化活性的不相容问题。这些同样是纳米级的材料，被设计成在单个纳米粒子和底层衬底之间充当“胶水”或锚点。该活动将工程、化学和材料科学联系起来，提供了一个多学科的研究环境，为研究生和本科生解决材料科学、表面化学和催化领域的复杂问题做好准备。技术摘要：高温、非均相催化剂在排放修复、燃料改造、电化学储能转化等方面发挥着重要作用。由于原子迁移和颗粒表面积的减小，高表面积金属纳米颗粒的热力学不稳定性限制了其在高温下的应用。密歇根州立大学的研究小组正在研究增强金属纳米颗粒的新方法，以利用广泛认可的金属催化性能，而不牺牲纳米组件在高温下的稳定性。研究目标是通过设计新的界面相，将纳米颗粒化学结合到陶瓷载体上，在不影响催化活性的情况下实现所需的功能。项目成果包括：1)优化方法，以定制锚定阶段组成和位置；Ii)确定导致锚定化学反应的机制；Iii)评估机制对热、化学和电化学条件的敏感性；iv)确定锚点在高达800摄氏度的高温下保持催化功能的作用。这项研究活动的重点是将镍金属纳米颗粒锚定在离子导电陶瓷衬底上，其中二级前驱体的金属有机溶液被应用并优化用于需要高和低纳米颗粒负载的特定催化剂功能。为了确定促进这种锚定策略的原子尺度机制，正在使用一套非原位和原位技术来解决相组成，材料的空间相关性，材料稳定性以及与二次相形成和颗粒粗化相关的反应动力学。该研究项目强调表面化学，旨在抑制与表面扩散相关的金属运输。此外，研究小组正在利用机理分析将这些策略扩展到其他高温金属催化剂，包括那些需要贵金属的催化剂，在这些催化剂中，提高最低负载性能至关重要。

Non-Technical AbstractNano-materials offer new opportunities to enhance technically important processes such as controlling pollutants, restructuring advanced fuel sources, as well as enabling clean and efficient energy conversion. High temperature applications, however, can limit the utility of nano-materials due to high particle mobility and sintering processes. With support from the Solid State and Materials Chemistry Program in the Division of Materials Resarch, this project addresses the incompatibility of high temperature particle instability and nano-particle catalytic activity by securing metallic nano-particles to ceramic substrates with newly engineered materials. These materials, also nano-scale in size, are designed to serve as "glue" or anchors between individual nano-particles and the underlying substrate. Linking engineering, chemistry, and materials science, this activity provides a multi-disciplinary research environment that is preparing graduate and undergraduate students to tackle complex problems in areas of materials science, surface chemistry, and catalysis. Technical AbstractHigh temperature, heterogeneous catalysts play a vital role in emissions remediation, fuel reformation, and electrochemical energy storage and conversion. The thermodynamic instability of high surface area metal nano-particles limits their use at elevated temperatures due to atom migration and reduction of particle surface area. The research team at MSU is investigating new approaches for enhancing metallic nano-particles to leverage the widely recognized catalytic performance of metals without sacrificing the stability of nano-assemblies at elevated temperatures. Research goals are being accomplished by engineering new interfacial phases to chemically bind nano-particles to ceramic supports to achieve desired functionality without compromising catalytic activity. The project outcomes include i) optimizing methods to tailor anchoring phase composition and location; ii) identifying the mechanisms responsible for enabling the anchoring chemical reactions; iii) evaluating the sensitivity of the mechanisms to thermal, chemical, and electrochemical conditions; and iv) identifying the effects conferred by anchors to preserve catalytic function at high temperature up to 800 Celsius. This research activity focuses on anchoring nickel metal nano-particles to ion conducting ceramic substrates in which metal-organic solutions of secondary phase precursors are being applied and optimized for specific catalyst functionality where both high and low nano-particle loading is required. To identify the atomic scale mechanisms that foster this anchoring strategy, a suite of ex-situ and in-situ techniques are being utilized to resolve phase compositions, spatial correlations of materials, material stability, and reaction kinetics associated with secondary phase formation and particle coarsening. The research project emphasizes surface chemistry designed to inhibit metal transport associated with surface diffusion. Further, the research team is utilizing the mechanistic analysis to expand these strategies to other high temperature metal catalysts including those requiring precious metals where enhancing performance at minimum loading is critical.