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

开发催化过程以有效地将二氧化碳(CO2)转化为化学品和燃料，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。二氧化碳直接转化为甲醇特别有吸引力，因为甲醇可以在现有发电系统中用作燃料，并在各种重要化学品的商业规模合成中用作原料。然而，目前二氧化碳直接加氢制甲醇的催化过程并不适合商业使用。主要的困难是大多数催化材料缺乏在基于二氧化碳的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，研究人员正在发展对使用双功能金属/金属氧化物催化剂将二氧化碳选择性加氢为甲醇的基本理解。开发这些催化剂的金属和氧化物成分的独特化学功能对于高效和选择性地将二氧化碳转化为甲醇是必要的。调查人员为高中生和本科生提供参与研究的机会，并专注于从代表性不足的群体中招募学生参与这些活动。这些外联活动旨在促进科学、技术、工程和数学(STEM)学科的发展。该项目旨在加深对Pd促进的In_2O_3(氧化铟)催化剂的基本了解，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合成甲醇的能力。其核心思想是，共存的In_2O_3和金属间化合物Pd_xIn_y将通过交换反应中间产物和提供具有独特化学性质的界面位来协同作用，促进CO_2加氢制甲醇，并且Pd_xIn_y的结构和化学计量比可以改变催化剂的催化行为。本研究包括Pd修饰的平面晶面In2O3和纳米晶粉末的结构和化学性质的研究。采用实验和理论相结合的方法对这些材料进行了研究，包括超高真空表面科学和催化剂表征、反应器研究和操纵面光谱，以及密度泛函理论和微观动力学模型。该项目的一个主要目标是建立基本的结构-功能关系，以指导二氧化碳选择性加氢合成甲醇的Pd-In_2O_3催化剂的设计。该项目涉及将第一性原理建模的结果与从平面晶体表面和更复杂的纳米颗粒获得的实验结果进行严格的比较，以发展对二氧化碳直接加氢生成甲醇的可靠理解。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。

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.