Bifunctionality of Intermetallic Pd-In/Indium-Oxide Catalysts for CO2 Hydrogenation to Methanol

开发将二氧化碳有效转化为化学品和燃料的催化过程对于减少二氧化碳排放和实现利用可再生能源的技术至关重要。直接将二氧化碳转化为甲醇是特别有吸引力的，因为甲醇可以作为现有发电系统的燃料，并被用作商业规模合成各种重要化学品的原料。然而，目前，直接将二氧化碳氢化成甲醇的催化过程不适合商业用途。主要的困难是，大多数催化材料缺乏在二氧化碳基甲醇合成所需的低温下运行的稳定性和活性。在这个项目中，研究人员正在对使用双功能金属/金属氧化物催化剂将二氧化碳选择性加氢成甲醇进行基本的了解。利用这些催化剂的金属和氧化物成分的独特化学功能是有效和有选择性地将二氧化碳转化为甲醇的必要条件。调查人员正在为高中生和本科生提供参与他们研究的机会，并专注于从代表性不足的群体中招募学生参与这些活动。这些外展活动旨在促进科学、技术、工程和数学（STEM）学科的发展。该项目旨在对钯促进的In2O3（氧化铟）催化剂有一个基本的了解，并确定如何利用这些表面的化学双功能来增强二氧化碳选择性加氢制甲醇。关键思想是共存的In2O3和金属间相PdxIny将通过交换反应中间体和提供具有独特化学性质的界面表面位点来协同作用，从而促进CO2加氢成甲醇，并且PdxIny的结构和化学计量可以改变催化行为。本研究主要研究了钯修饰In2O3的结构和化学性质，制备了平面晶体表面和纳米晶体粉末。这些材料采用实验和理论相结合的方法进行研究，包括超高真空表面科学和催化剂表征，反应器研究和operando表面光谱，以及密度泛函理论和微动力学建模。该项目的主要目的是建立基本的结构-功能关系，以指导Pd-In2O3催化剂的设计，以选择性地将二氧化碳加氢成甲醇。该项目将第一性原理建模的结果与平面晶体表面和更复杂的纳米颗粒的实验结果进行严格比较，以对二氧化碳直接加氢制甲醇的过程有更深入的了解。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。

Developing catalytic processes to efficiently convert carbon dioxide (CO2) to chemicals and fuels is essential for mitigating CO2 emissions and enabling technologies that utilize renewable energy. The direct conversion of CO2 to methanol is particularly attractive because methanol can serve as a fuel in existing power generation systems and is used as a feedstock in the commercial-scale synthesis of a wide-range of important chemicals. Currently, however, catalytic processes to directly hydrogenate CO2 to methanol are unsuitable for commercial use. The major difficulty is that most catalytic materials lack the stability and activity to operate at the low temperatures needed for CO2-based methanol synthesis. In this project, the investigators are developing a fundamental understanding of the selective hydrogenation of CO2 to methanol using bifunctional metal/metal-oxide catalysts. Exploiting the distinct chemical functionality of the metallic and oxide components of these catalysts is necessary for efficiently and selectively converting CO2 to methanol. The investigators are providing opportunities for high school and undergraduate students to participate in their research and are focused on recruiting students from underrepresented groups to engage in these activities. These outreach activities seek to promote the science, technology, engineering and math (STEM) disciplines. The project aims to develop a fundamental understanding of Pd-promoted In2O3 (indium oxide) catalysts and determine how the chemical bifunctionality of these surfaces can be exploited to enhance the selective hydrogenation of CO2 to methanol. The key idea is that coexisting In2O3 and intermetallic PdxIny phases will act cooperatively to enhance the hydrogenation of CO2 to methanol by exchanging reaction intermediates and providing interfacial surface sites with unique chemical properties, and that the catalytic behavior can be modified by the PdxIny structure and stoichiometry. This research involves investigations of the structural and chemical properties of Pd-modified In2O3 prepared as planar crystalline surfaces as well as nanocrystalline powders. These materials are investigated using a combination of experimental and theoretical methods including ultrahigh vacuum surface science and catalyst characterization, reactor studies and operando surface spectroscopy, as well as density functional theory and microkinetic modeling. A primary aim of the project is to establish fundamental structure-function relationships to guide the design of Pd-In2O3 catalysts for the selective hydrogenation of CO2 to methanol. The project involves stringent comparisons of the results of first-principles modeling with experimental results obtained from planar crystalline surfaces and more complex nanoparticles to develop a robust understanding of the direct hydrogenation of CO2 to methanol.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.