INFEWS N/P/H2O: Photo-thermal ammonia synthesis of plasmonic metal nanoparticles

该项目研究了一种低温低压光催化替代高温高压热催化Haber-Bosch （H-B）商业氨（NH3）生产工艺。氨是化肥生产的主要原料，其通过H-B工艺合成占全球能源消耗的1-2%。该项目将研究一类等离子体金属粒子作为催化剂，利用自然紫外线和可见光，在低温和低压下激活氮（N2）和氢（H2）直接气相合成NH3。因此，NH3的光催化合成有助于实现未来的可持续能源途径，以满足基于从太阳而不是碳氢化合物资源中收集能量的全球粮食需求。该项目建立在等离子体金属纳米粒子可以在低温和低压下激活直接气相氨合成的假设之上，当被太阳强度的紫外-可见光照射时。等离子体金属纳米结构的决定性特征是它们通过局部表面等离子体共振（LSPR）的激发与紫外-可见光的强共振相互作用，从而在纳米颗粒表面形成高速率的高能电子。高能电子可以在金属上引起化学反应，包括在低温下激活强化学键。该项目将寻求通过利用具有等离子体金属核（Au或Ag）和化学活性更强的金属（Ru, Rh, Pt， Pd等）的薄壳（甚至小簇）的核-壳粒子来增强NH3合成的等离子体效应。在提出的双金属系统中，等离子体核心的作用是有效地收集光的能量，并以高能电子的形式将其转移到更活跃的物质上。活性较强的金属的作用是利用高能电子为N2的结合和解离提供催化位点。N和NHx中间体在这些金属上的进一步还原速度很快。除了NH3合成之外，该项目还将解决一些关于等离子体金属和吸附剂上局部光感应电场相互作用的基本问题。这些问题对于控制纳米尺度的热电子流动至关重要，在光化学、光伏和任何光激发和高能电荷收集发挥作用的应用领域都具有重要意义。该项目还将采用一系列教育和推广活动，旨在通过研究成果的涓涓细流，通过课程向研究生、本科生甚至更年轻的学生推广学习，同时也让不同群体的更年轻的学生参与传统的推广项目和不那么传统的策略，旨在提高万维网在学生和公众中的利用率。

The project investigates a low-temperature, low-pressure photocatalytic alternative to the high temperature and pressure thermo-catalytic Haber-Bosch (H-B) commercial process for ammonia (NH3) production. Ammonia is a primary feedstock for fertilizer production, and its synthesis via the H-B process accounts for 1-2% of global energy consumption. The project will investigate a class of plasmonic metal particles as catalysts for activating the direct, gas-phase synthesis of NH3 from nitrogen (N2) and hydrogen (H2) at low temperatures and pressures utilizing natural ultra-violet and visible light. Photocatalytic synthesis of NH3 thus helps enable a future sustainable-energy path to meet global food needs based on harvesting energy from the sun rather than hydrocarbon resources. The project is built on the hypothesis that plasmonic metal nanoparticles can activate direct, gas-phase ammonia synthesis at low temperatures and pressures when illuminated by UV-vis light of solar intensity. The defining characteristic of plasmonic metallic nanostructures is their strong resonant interaction with UV-vis light through the excitation of localized surface plasmon resonance (LSPR) which results in high rates of formation of high-energy electrons at the surface of the nanoparticles. The energetic electrons can induce chemical reactions on metals, including the activation of strong chemical bonds at low temperatures. The project will seek to enhance the plasmonic effect for NH3 synthesis by utilizing core-shell particles with a plasmonic metal core (Au, or Ag) and a thin shell (or even a small cluster) of a chemically more active metal (Ru, Rh, Pt, Pd, etc.). In the proposed bimetallic systems, the role of the plasmonic core is to efficiently harvest the energy of light and transfer it in the form of energetic electrons to the more active material. The role of the more active metal is to provide the catalytic sites for binding and dissociation of N2 using the energetic electrons. Further reduction of the N and NHx intermediates is fast on these metals. Beyond NH3 synthesis, the project will address a number of fundamental questions about the interaction of local light-induced electric fields on plasmonic metals and adsorbates. These questions are critical for controlling the hot-electron flow at nanoscales, which is of importance in the fields of photochemistry, photovoltaics and any application where photo-excitation and energetic charge harvesting play a role. The project will also employ a number of educational and outreach activities designed to promote learning via trickle-down of research findings through the curriculum to graduate, undergraduate, and even younger students while also involving a diverse group of younger students in conventional outreach programs and less conventional strategies aimed at improving the utilization of the World Wide Web in reaching students and the general public.