One-Dimensional Functional Nanocrystals with Non-Precious-Metal Cores and Precious-Metal Shells

摘要：发展高效、绿色的能源转换技术对美国能源和环境的可持续发展具有战略意义。与传统的化石燃料燃烧装置相比，质子交换膜燃料电池（pemfc）在运输和固定电网应用方面都具有巨大的潜力，因为它们更清洁、更便宜、更可靠；它们使用可再生氢燃料；它们在碳排放最小化的情况下表现出高效率。该项目旨在开发一种具有一维结构和核/壳结构的新兴纳米结构材料，以最大限度地发挥pemfc的效益。这种纳米材料的合理设计和精确制备可以显著地促进材料设计和合成的理解，以实现高效和低成本的pemfc和许多其他应用，包括电池，电解槽和电化学传感器。该项目的成果可以加速pemfc的大规模应用，有可能改变美国的能源组合，并建立一个生态良性的能源社会。教育计划旨在与研究活动相结合，以促进几个层次的教学，培训和学习，涵盖K-12，本科生和研究生。部分活动包括涉及代表性不足的少数民族的教育外展活动。该项目可以在催化、能源技术和其他科学、技术、工程和数学（STEM）领域吸引、培养和留住高素质的下一代劳动力。技术摘要：基于可再生氢能源的质子交换膜燃料电池（pemfc）在建立可持续的清洁氢能源经济，减少社会对传统化石燃料及相关燃烧技术的依赖方面发挥着至关重要的作用。适用于大规模运输和固定电网的先进pemfc需要一种纳米结构材料，可以在足够长的时间内以高活性加速阴极氧还原反应（ORR），并将铂族金属的使用量降至最低。本课题的目标是通过精确控制其核壳材料组成和物理参数（如一维纳米棒的长度、核壳界面和壳型），设计和合成具有非贵金属核心的一维核壳纳米晶体，从根本上了解原子级纳米晶体结构与良好电催化性能的关系。利用纳米材料合成、结构表征、电化学和理论计算等方面的专业知识，主要研究四个方面的工作：(1)合理设计和合成具有可控长度和壳型的磷化钴-铂核壳纳米棒；(2)调整核壳界面和结构布置；(3)利用过渡金属掺杂磷化钴纳米棒芯优化纳米晶效率；(4)通过电化学、光谱和计算方法的结合，了解优化ORR转换的设计规则。所产生的知识通过在原子水平上利用机制控制合成加速了新形式纳米材料的发展，并揭示了如何关联和控制它们的功能活性和结构稳定性。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Non-Technical Abstract:Developing efficient and green energy conversion technologies is of strategic importance for the United States energy and environmental sustainability. Compared with conventional fossil fuel combustion devices, proton exchange membrane fuel cells (PEMFCs) hold great potentials for both transportation and stationary grid applications since they are cleaner, more affordable, and more reliable; they run with renewable hydrogen fuel; and they demonstrate high efficiency with minimized carbon emission. This project aims to develop an emerging class of nanostructured materials with one-dimensional architecture and core/shell structure which can maximize the benefit of PEMFCs. The rational design and precise preparation of such nanomaterials can significantly advance the understanding of both materials design and synthesis for efficient and cost-effective PEMFCs and many other applications, including batteries, electrolyzers, and electrochemical sensors. The outcome of this project can accelerate the large-scale application of PEMFCs, potentially transform the United States energy portfolio, and establish an eco-benign energy society. An education plan is designed to be integrated with research activities to promote teaching, training and learning at several levels, covering K-12, undergraduate and graduate students. Parts of the activities include educational outreach involving underrepresented minorities. The project can attract, build and retain a high-quality next-generation workforce in catalysis, energy technology and other science, technology, engineering, and math (STEM) fields.Technical Abstract: Proton exchange membrane fuel cells (PEMFCs), based on renewable hydrogen sources, play a critical role in establishing a sustainable and clean hydrogen energy economy to reduce our society's dependency on conventional fossil fuels and the related combustion technologies. Advanced PEMFCs suitable for large-scale transportation and stationary grid powers demand a nanostructured material that can be used to accelerate the cathodic oxygen reduction reaction (ORR) with a high activity over a sufficiently long period of time and with minimized platinum group metal usage. The objective of this project is to design and synthesize one-dimensional core-shell nanocrystals with non-precious-metal cores, by precisely controlling their core-shell material compositions and physical parameters (e.g. lengths of one-dimensional nanorods, core-shell interfaces, and shell profiles), to fundamentally understand the correlation of atomic level nanocrystal architecture to the favorable electrocatalytic properties. The Principle Investigator leverages the expertise in nanomaterials synthesis, structural characterization, electrochemistry and theoretical calculation, to primarily focus on four tasks: (1) Rationally designing and synthesizing cobalt phosphide-platinum core-shell nanorods with controlled lengths and shell profiles; (2) Tuning the core-shell interface and structural arrangements; (3) Optimizing the efficiency of nanocrystals by using transition metal doped cobalt phosphide nanorod cores; and (4) Understanding the design rules for optimized ORR conversion through a combination of electrochemical, spectroscopic, and computational approaches. The generated knowledge accelerates the development of new forms of nanomaterials by exploiting the mechanism controls of synthesis at the atomic level and uncovers how to correlate and control their functional activity and structural stability.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.