CAREER: Spectrokinetic Studies for Understanding Metal-Support Interactions in Catalytic Oxidation of Ethanol

乙醇是一种由生物可再生资源生产的主要商品化学品，主要用于运输燃料。该项目将专注于改进催化剂，通过将乙醇转化为醋酸等增值衍生物来扩大乙醇市场。具体来说，该项目将研究金纳米颗粒和金属氧化物催化剂载体之间的相互作用，以获得基本的理解，这将用于设计更具活性和选择性的醋酸生产催化剂。在这个项目中获得的基础知识将有助于美国生物乙醇工厂的长期可持续性。机械的见解也将提供更好的理解金属-支撑相互作用，包括贵金属在汽车尾气氧化催化等应用中的作用。该研究与一项教育计划相结合，该计划通过研究和社区参与为不同群体的本科生和研究生提供培训和领导机会。该项目解决了多相催化中电荷转移过程的影响。评估原位电荷转移速率及其与表面催化反应的动力学相关性的实验工具数量有限，这是促进对金属-载体相互作用理解的主要障碍。目前已经开发了三种光谱学技术，以促进1)对金催化剂上吸附氧的原位评价（金表面等离子体共振-紫外可见光谱，即Au-SPR-UV-vis）， 2)识别表面反应中间体（调制激发-相敏探测-弥反射红外傅立叶变换光谱，即ME-PSD-DRIFTS），金属和载体之间的电荷转移（调制激发-相敏检测-紫外可见光谱，即ME-PSD-UV-vis）。本项目将通过对各种催化剂的研究，系统地考察电子和结构金属支撑效应，同时分离金的粒度、支撑性质和催化剂合成方法。据推测，具有n型半导体性质的支持物促进电荷从金纳米颗粒周围转移到金纳米颗粒周围，从而促进活性物质将乙醇氧化成乙酸。总之，结合Au-SPR-UV-vis， ME-PSD-FTIR, ME-PSD-UV-vis，光谱动力学和反应动力学将提供气相乙醇氧化的综合机理观点，以描述观察到的活性和选择性趋势。新的知识和技术将有助于下一代金氧化催化剂的设计。它们也将被转移到其他氧化反应中，从而扩大了它们在广泛的表面催化反应中的适用性。研究和教育项目将培养一批训练有素的多元化学生骨干，进入STEM学科的劳动力市场。一项新的课外科学推广活动——EMPower（能量、物质和力量）俱乐部，也将为本科生提供领导机会，同时为来自弱势群体和低收入背景的小学生充当榜样和导师。该活动将通过动手活动激发孩子们的好奇心，让他们在有趣的活动中欣赏科学，激发他们在STEM领域接受教育的动力。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。

Ethanol is a major commodity chemical produced from biorenewable sources that is primarily used in transportation fuel. The project will focus on improved catalysts for expanding the ethanol market by converting the ethanol to value-added derivatives such as acetic acid. Specifically, the project will study the interactions between gold nanoparticles and metal oxide catalyst supports to gain fundamental understanding that will be used to design more active and selective catalysts for acetic acid production. The fundamental knowledge gained in this project will contribute to the long-term sustainability of U.S. bioethanol plants. Mechanistic insights will also provide better general understanding of metal-support interactions involving noble metals in applications such as automotive exhaust oxidation catalysis. The research is integrated with an educational plan that provides training and leadership opportunities to a diverse group of undergraduate and graduate students through research and community engagement.The project addresses the effects of charge transfer processes in heterogeneous catalysis. The limited number of experimental tools to assess in situ charge transfer rates and their kinetic relevance for surface catalyzed reactions has been a major obstacle for advancing the understanding of metal-support interactions. Three enabling spectroscopic techniques have been developed to facilitate 1) in situ evaluation of adsorbed oxygen on gold catalysts (Gold-Surface Plasmon Resonance-UV-visible spectroscopy, i.e. Au-SPR-UV-vis), 2) identify surface reaction intermediates (Modulation Excitation-Phase Sensitive Detection-Diffuse Reflectance Infrared Fourier Transform Spectroscopy, i.e. ME-PSD-DRIFTS), and charge transfer between metal and support (Modulation Excitation-Phase Sensitive Detection-UV-visible spectroscopy, i.e. ME-PSD-UV-vis). This project will systematically examine electronic and structural metal-support effects by studying a variety of catalysts while isolating gold particle size, support nature, and catalyst synthesis method. It is hypothesized that supports with n-type semiconducting properties facilitate charge transfer from and to the gold nanoparticle periphery, thereby promoting active species that oxidize ethanol to acetic acid. Overall, the combination of Au-SPR-UV-vis, ME-PSD-FTIR, ME-PSD-UV-vis, spectrokinetics, and reaction kinetics will provide a comprehensive mechanistic view of gas phase ethanol oxidation to describe the observed activity and selectivity trends. The new knowledge and techniques will assist in the design of next-generation gold oxidation catalysts. They will also be transferable to other oxidation reactions, thus expanding their applicability to a wide range of surface catalyzed reactions. The research and educational programs will produce a trained cadre of diverse students to enter the workforce in STEM disciplines. A new outreach after-school science initiative, EMPower (Energy, Matter, & Power) club, will also provide undergraduate students with leadership opportunities while serving as role models and mentors for elementary school children from underrepresented groups and low-income backgrounds. The initiative will serve as a catalyst to spark children's curiosity through hands-on activities to let them appreciate science with fun activities and inspire them to pursue education in STEM fields.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.