ECLIPSE: Mechanistic understanding and control of nitrogen activation in an atmospheric-pressure plasma-liquid process

为了减少我们对化石燃料的依赖，需要可持续的方法来激活和化学转化容易获得的原料，如来自空气和水的氮气。等离子体允许化学反应在常压和接近室温的情况下进行，而不需要任何催化剂，使用可再生电力。与液体接触的等离子体是最近出现的一种促进电化学反应的新方法。然而，发生在等离子体-液体界面上的化学反应是极其复杂的，需要探索化学和获得机理洞察力的方法。这项研究计划将开发尖端的光谱方法来研究运行条件下等离子体-液体界面的化学反应和物种组成。虽然这些方法是通用的，但研究小组将专注于氮和水的反应来产生氨，氨是所有氮基农业肥料的前体。目前，氨的工业生产是由一种具有百年历史的工艺生产的，该工艺的碳足迹很大，需要大型的集中式加工厂。该项目通过开发一种可持续和地理分布的合成氨工艺，有可能促进国家健康、繁荣和福利。学生将通过访问当地农场获得体验式学习，这将为他们提供社会经济背景，以激励他们的研究。该项目将开发原位光谱技术来表征大气压等离子体和液态水之间的界面化学。氮气的气相活化将用光学发射光谱和激光诊断法进行表征。该项目的一个主要重点将是实施原位表面增强拉曼散射光谱，通过气相物种的解离和随后的液相反应来检测在等离子体-液体界面附近形成的中间体。气相和液态测量产生的等离子体诱导化学反应的基本知识将与两种提高产品产量和能源效率的工程策略相结合：等离子体的脉冲操作以保持较低的气相温度，以及引入水滴或水蒸气以增加等离子体/水界面区域的大小。这项拟议工作的成果将是更深入地了解等离子体在液体表面诱导的反应路径，阐明相对于其他氮素激活替代方法的独特方面，以及优化等离子体-液体过程的前进道路。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

To reduce our reliance on fossil fuels, sustainable approaches are needed for activating and chemically transforming readily available feedstocks such as nitrogen from the air and water. Plasmas allow chemical reactions to be performed at atmospheric pressure and near room temperature without any catalyst using renewable electricity. Plasmas in contact with liquids have recently emerged as a new approach to promoting electrochemical reactions. However, chemical reactions taking place at a plasma-liquid interface are extremely complex and methods of probing the chemistry and gaining mechanistic insights are needed. This research program will develop cutting edge spectroscopic methods to study chemical reactions and species composition at the plasma-liquid interface under operating conditions. While the methods are general, the research team will focus on the reaction of nitrogen and water to produce ammonia, the precursor to all nitrogen-based agricultural fertilizers. Ammonia is currently industrially produced by a century-old process which has a large carbon footprint and requires large, centralized processing plants. This project has the potential to advance national health, prosperity, and welfare, by developing a sustainable and geographically distributed process for ammonia synthesis. Students will receive experiential learning through visits to local farms, which will provide them with the socioeconomic context to motivate their research. This project will develop in-situ spectroscopic techniques to characterize the interfacial chemistry between an atmospheric-pressure plasma and liquid water. Gas-phase activation of dinitrogen will be characterized by optical emission spectroscopy and laser diagnostics. A major focus of the project will be to implement in-situ surface-enhanced Raman scattering spectroscopy to detect intermediates formed near the plasma-liquid interface by dissociation of gas-phase species and subsequent reaction in the liquid phase. The fundamental knowledge of plasma-induced chemical reactions generated by the gas and liquid phase measurements will be combined with two engineering strategies to improve product yields and energy efficiency: pulsed operation of the plasma to maintain low gas-phase temperatures and the introduction of water droplets or water vapor to increase the size of the plasma/water interfacial area. The outcomes of the proposed work will be a deeper understanding of reaction pathways induced by a plasma at the surface of a liquid, elucidation of unique aspects relative to other alternative methods of dinitrogen activation, and a path forward for optimization of plasma–liquid processes.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.