Non-Mean Field Treatments of Surface Chemistry: Incorporating Adsorbate-Adsorbate Interactions into Deterministic Kinetic Theories

表面化学的非平均场处理：将吸附质-吸附质相互作用纳入确定性动力学理论

• 批准号: 2102614
• 负责人: Jeffrey Greeley
• 金额: $ 29.98万
• 依托单位: Purdue University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-01-01 至 2024-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2102614&HistoricalAwards=false
• 关键词: Non; Mean; Field; Treatments; Surface; Non; Mean; Field; Treatments; Surface

Jeffrey Greeley of Purdue University is supported by an award from the Chemical Catalysis program in the Division of Chemistry to study heterogeneous catalysts with new theoretical methods. Heterogeneous catalysts accelerate the conversion of chemical species to valuable products, and they underpin a host of technologically important chemical processes, ranging from production of plastics to generation of electricity in fuel cells. These catalysts are often composed of metal nanoparticles, the surfaces of which break and form chemical bonds in molecules to produce valuable products. Fundamental models of how these molecular transformations occur have been developed for many chemical reactions and have greatly enhanced both the understanding of these transformations and the design of new catalytic materials. However, these models often make significant approximations in their descriptions of the relevant molecular processes, including the assumption that reacting molecules and products are randomly distributed across the catalyst surfaces and do not interact with one another. The development of improved theoretical descriptions that correct these approximations and explicitly describe how the reactions change when molecules interact strongly with one another, is, in turn, the central focus of this project. The improved models will lead to more accurate descriptions of heterogeneous catalytic processes and may ultimately facilitate the design of improved catalysts. For broader impacts, the new capability and software will be made available to the catalysis community. Outreach and education efforts will focus on high school students at a very early stage in their academic path, to encourage the pursuit of STEM studies. PI will make a focused effort to engage students from diverse and under-represented groups. This activity will be a continuation of a successful effort by the PI, whereby the students are paired with the PI and graduate students to pursue tailored research projects.Mean field theories of surface kinetics permit crucial information about heterogeneous catalytic processes, including the overall reaction rates, effective activation barriers, and reaction orders, to be predicted from a combined knowledge of the elementary reaction steps occurring on a catalyst surface and the rate constants of these elementary steps. In spite of the power of these theories, however, the mean field approximation begins to break down under conditions of strong interactions between surface adsorbates, and there is a need to develop surface kinetic modeling techniques that directly incorporate non-mean field effects while, at the same time, preserving the powerful physical and mechanistic insights that emerge naturally from deterministic mean field descriptions. In this work, analytical or semi-analytical corrections to mean field expressions for equilibrium constants and rate constants of elementary reactions will be developed on square planar and hexagonal catalyst surfaces. These expressions, which will be based on the Bethe-Peierls approximation to the Cluster Variation Method, will be used to identify mathematical and conceptual principles that describe when non-mean field effects will significantly impact surface catalysis. The resulting formalisms, which will deterministically treat non-mean field effects while preserving the powerful mechanistic insights that can be obtained from mean field microkinetic analyses, will be benchmarked on two classic surface reaction chemistries, the direct and H2-assisted decomposition of NO and the synthesis or decomposition of ammonia from N2 and H2.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.

普渡大学的杰弗里·格里利（Jeffrey Greeley）得到了化学催化计划的奖项，以使用新的理论方法研究异质催化剂。 异质催化剂加速了化学物种向有价值的产品的转化，并且它们基于一系列具有技术重要的化学过程，从塑料的产生到燃料电池的发电。 这些催化剂通常由金属纳米颗粒组成，金属纳米颗粒的表面断裂并在分子中形成化学键以产生有价值的产物。 这些分子转化如何发生的基本模型是针对许多化学反应开发的，并且大大增强了对这些转化的理解和新催化材料的设计。 但是，这些模型通常在相关分子过程的描述中具有显着的近似值，包括假设反应分子和产物是随机分布在整个催化剂表面上并且不相互作用的假设。 改进的理论描述纠正这些近似值的理论描述，并明确描述当分子彼此之间强烈相互作用时这些反应如何变化，反过来又是该项目的中心重点。 改进的模型将导致对异质催化过程的更准确描述，并最终促进改进的催化剂的设计。对于更广泛的影响，新功能和软件将提供给催化社区。宣传和教育工作将在他们的学术道路上的早期阶段集中于高中生，以鼓励对STEM研究进行。 PI将集中精力吸引来自不同和代表性不足的群体的学生。 This activity will be a continuation of a successful effort by the PI, whereby the students are paired with the PI and graduate students to pursue tailored research projects.Mean field theories of surface kinetics permit crucial information about heterogeneous catalytic processes, including the overall reaction rates, effective activation barriers, and reaction orders, to be predicted from a combined knowledge of the elementary reaction steps occurring on a catalyst surface and the rate constants of these elementary steps.然而，尽管这些理论的力量具有强大的力量，但在表面吸附物之间发生较强相互作用的条件下，平均场近似开始崩溃，并且有必要开发表面动力学建模技术，这些技术直接直接融合了非均值的场效应，同时，可以自然地从确定性的均值降低的均值中出现出强大的物理和机械洞察力。 在这项工作中，将在方形平面和六边形催化剂表面上开发基本反应的平衡常数和基本反应速率常数的平均场表达式的分析或半分析校正。 这些表达式将基于伯特·佩尔斯（Bethe-Peierls）与聚类变化方法的近似，将用于识别数学和概念性原理，这些数学和概念原理描述了何时非均值野外效应会显着影响表面催化。 由此产生的形式主义将在确定性上对非均值的现场影响，同时保留可以从平均野外微动分析中获得的强大机械见解，它将基于两个经典的表面反应化学，即直接和H2辅助的NO和H2辅助分解，并通过N2和H. a n2 and ns n. n. and N. nosef and N. nots and N.使用基金会的智力优点和更广泛的影响评估标准进行评估。