Photocatalytic N2 reduction utilizing the upconverted hot electron

利用上转换热电子进行光催化 N2 还原

• 批准号: 2308807
• 负责人: Dong Son
• 金额: $ 45万
• 依托单位: Texas A&M University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-09-01 至 2026-08-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2308807&HistoricalAwards=false
• 关键词: Photocatalytic; N2; reduction; utilizing; upconverted

Ammonia (NH3) is among the most important molecules produced at an industrial scale due to its critical role for agriculture and other chemical industries. The well-known Haber-Bosch process currently used to manufacture NH3 requires high pressure and operating temperatures leaving a very large carbon footprint consuming over 1% of the total energy produced globally. The project explores a photocatalytic alternative to the fossil fuel driven thermal Haber-Bosch process, potentially achieving drastic reductions in the carbon footprint and energy consumption. Although the photocatalytic approach derives energy from the sun, the solar utilization efficiency at the current level of technology is too low for commercial application. The project thus investigates a novel catalyst design that potentially can boost the photocatalytic NH3 manufacturing efficiency significantly beyond the current state-of-the-art. The project is bolstered by educational and outreach activities targeting K-12 students, teachers, and undergraduate students.Photocatalytic and electrocatalytic approaches are being explored for the conversion of N2 into NH3 to resolve the issues of the Harbor-Bosch process. However, because of the high reduction potential of N2, its highly stable triple bond, and weak surface adsorption affinity, the reduction of N2 to NH3 remains one of the most challenging photocatalytic reactions. The project will develop a new photocatalytic approach to convert N2 to NH3 by utilizing hot electrons that are produced via an exciton-to-hot electron upconversion process in Mn-doped semiconductor quantum dots (QDs). This allows for the use of visible light to generate hot electrons that possess very high excess energy above the conduction band and exhibit long-range transfer capability. These hot electrons have recently been shown to enhance photocatalytic H2 production as well as CO2 reduction, and are expected to (i) be of sufficiently high reduction potential for N2 to NH3 conversion and (ii) produce solvated electrons that can additionally participate in N2 to NH3 conversion. Specifically, the research will explore three different approaches with the goal of increasing the overall quantum efficiency of N2 to NH3 reduction significantly beyond the current state-of-the-art (~1%). The first approach aims at enhancing the kinetics of the reduction of N2 and intermediate species by hot electrons and solvated electrons. This will be accomplished by employing binary solvent systems that greatly increase the concentration and stability of N2 and intermediate species. The second approach uses QD/molecular catalyst hybrid systems in which the long-range hot electron sensitization will be exploited to enable the use of molecular N2 reduction catalysts without requiring covalent attachments to the QDs. The third approach aims at enhancing the rate of hot electron generation and the redox balance simultaneously by using indium tin oxide photonic crystals imbedded with QD photocatalysts leading to dual functionality of enhancing light absorption as well as hole transfer. In sum, the project aims to establish hot electron-driven visible light photocatalytic N2 reduction as a new approach that can bring much needed improvement in the photocatalytic N2 reduction efficiency. Beyond the research focus, the project will integrate undergraduate education with research via the Texas A&M Innovation [X] program designed to foster interdisciplinary education through research activities solving real-world problems. In addition, the investigators will continue to be involved in the university-wide Chemistry Open House and nation-wide US Crystal Growing Competition outreach activities that bring K-12 students, teachers and the general public to lectures, tours and hands-on activities on STEM subjects.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.

由于其在农业和其他化学工业中的关键作用，氨（NH3）是工业规模最重要的分子之一。目前用于生产NH3的著名Haber-Bosch工艺需要高压和工作温度，使碳足迹非常大，占全球总能源的1％以上。该项目探索了化石燃料驱动的热式Haber-Bosch工艺的光催化替代品，可能会实现碳足迹和能源消耗的急剧减少。尽管光催化方法从太阳中得出能量，但目前技术水平的太阳能利用效率对于商业应用来说太低。 因此，该项目研究了一种新型的催化剂设计，该设计可能会显着提高光催化NH3的生产效率，从而显着超出当前的最新面积。 该项目受到针对K-12学生，老师和本科生的教育和外展活动的支持。正在探索将N2转换为NH3以解决Harbour-Bosch过程的问题，并正在探索用于催化和电催化方法。但是，由于N2的高还原电位，其高度稳定的三键和弱表面吸附亲和力，N2对NH3的降低仍然是最具挑战性的光催化反应之一。该项目将开发一种新的光催化方法，通过利用通过MN掺杂的半导体量子点（QDS）中的激子到热电子上转换过程（QDS）中生产的热电子将N2转换为NH3。这允许使用可见光来产生在传导带上方具有很高多余能量并具有长距离传输能力的热电子。最近已显示这些热电子可增强光催化H2的产生和二氧化碳的降低，并有望（i）对N2至NH3转换具有足够高的降低潜力，并且（ii）产生溶剂化的电子，这些电子可以另外参与N2至NH3转换。 具体而言，该研究将探索三种不同的方法，目的是将N2的整体量子效率提高至NH3降低，从而显着超过当前最新的量子（〜1％）。第一种方法旨在通过热电子和溶剂化电子来增强N2和中间物种还原的动力学。这将通过采用二元溶剂系统大大提高N2和中间物种的浓度和稳定性来实现。第二种方法使用QD/分子催化剂混合系统，其中将利用远程热电子敏化来实现分子N2还原催化剂，而无需与QD的共价附着。第三种方法旨在通过使用用氧化锡光子光子晶体同时提高热电子产生的速率和氧化还原平衡的速率，并用QD光催化剂嵌入，从而导致双重功能增强光吸收以及孔传递。 总而言之，该项目旨在建立热电子驱动的可见光光催化N2减少作为一种新方法，可以在光催化N2降低效率方面带来急需的改善。除了研究重点之外，该项目还将通过德克萨斯A＆M创新[X]计划将本科教育与旨在通过解决现实世界中问题的研究活动促进跨学科教育的研究融为一体。此外，调查人员将继续参与大学范围的化学开放日和全国性的水晶发展竞争外展活动，这使K-12学生，教师和公众参加STEM主题的讲座，旅行和动手活动。这一奖项反映了NSF的法规任务，并被认为是通过基金会的智力优点和广泛的评估来进行评估，这是值得通过评估来进行评估的。