CAREER: Investigating the Molecular Corking Effect for Potential Hydrogen Storage

该奖项全部或部分由2021年美国救援计划法案（公法117-2）资助。氢是一种多用途、能量密集的气体，可以在许多应用中作为化石燃料的替代品，包括运输和发电。然而，氢燃料的广泛采用受到限制，部分原因是无法在精心控制的工业环境之外安全地储存和运输氢气。这个项目将研究一种有趣的化学现象，称为“分子软木塞效应”，它可能被证明是一种有用的氢气储存机制。当氢气（双原子氢或H2）与一类称为单原子合金的材料相互作用时，已经观察到分子软木塞效应。单原子合金由相对惰性的贵金属表面点缀有催化活性金属（如铂和钯）的单原子组成。当双原子氢气接触单原子合金时，两个氢原子之间的键被催化活性金属打破。单个的氢原子随后溢出到惰性金属表面。可以添加一种优先与催化活性金属结合的“软木”分子，以防止氢原子重整气态氢。氢气可以以这种方式安全地储存，直到温度升高，去除软木塞分子并从表面释放氢气。为了充分实现单原子合金储氢的潜力，必须发展对整个分子软木塞过程的基本见解。该项目的研究目标是研究分子软木塞如何与单原子合金相互作用，并描述有效分子软木塞的化学特性。该项目还包括一项教育计划，重点是培养学生在追求化学和物理知识的过程中整合计算化学和实验研究。独立的教育材料将被开发出来，这样任何化学教师，不管是否熟悉计算方法，都可以将计算化学模块整合到他们的课程中。这些材料，以及在当地高中开展的拓展活动，将鼓励主要来自本科院校和其他资源有限环境的学生参与计算化学驱动的研究。这个项目由St. Bonaventure大学的Scott Simpson博士领导，目的是探索“分子软木塞效应”的极限，以控制氢在单原子合金上的溢出。引入到钯/铜或铂/铜单原子合金中的双原子氢将吸附在表面，在那里氢键将被催化活性金属劈裂。解离的氢原子溢出在贵金属表面。随后中毒配体对催化活性金属的选择性吸附阻止解离氢解吸和重整双原子氢。因此，这种配体起到了“分子软木塞”的作用，直到加热使配体分离，从表面释放出氢气。这种现象可以潜在地用于储氢应用。然而，单原子合金是一类相对较新的材料，控制分子软木塞效应的许多因素尚不清楚。因此，该研究计划旨在(1)了解分子软木塞与表面相互作用的基本知识，(2)探索各种分子软木塞储氢的可行性，以及(3)检查分子软木塞吸附对单原子合金聚集的影响。最先进的计算方法，包括密度泛函理论计算和动力学蒙特卡罗模拟，将被用来揭示单原子合金氢溢出和解吸的分子水平现象。实验验证通过扫描隧道显微镜和温度程序解吸研究将通过合作进行。该项目的成果有可能推动储氢技术的发展，并将与界面工程和多相催化研究界广泛相关。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。

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2)Hydrogen is a versatile, energy-dense gas that can be used as an alternative to fossil fuels in many applications, including transportation and power generation. However, widespread adoption of hydrogen fuels is limited, in part, by the inability to safely store and transport hydrogen gas outside of carefully controlled industrial environments. This project will study an intriguing chemical phenomenon called the "molecular corking effect," which may prove useful as a hydrogen gas storage mechanism. The molecular corking effect has been observed when hydrogen gas (diatomic hydrogen or H2) interacts with a class of materials called single-atom alloys. Single-atom alloys consist of a relatively inert noble metal surface interspersed with single atoms of catalytically-active metals such as platinum and palladium. When diatomic hydrogen gas contacts the single-atom alloy, the bond between the two hydrogen atoms is broken by the catalytically-active metal. The individual hydrogen atoms then spill over on the inert metal surface. A "cork" molecule that preferentially binds to the catalytically-active metal can be added to prevent the hydrogen atoms from reforming gaseous hydrogen. Hydrogen can be safely stored in this manner until the temperature is increased to remove the cork molecule and release the hydrogen gas from the surface. Fundamental insights into the entire molecular corking process must be developed to fully realize the potential of single-atom alloy hydrogen storage. The research objectives of this project will examine how molecular corks interact with single-atom alloys and describe the chemical characteristics of effective molecular corks. The project also includes an education plan focused on preparing students to integrate computational chemistry and experimental research in their pursuit of chemical and physical knowledge. Self-contained educational materials will be developed such that any chemistry instructor, regardless of comfort with computational methods, can integrate computational chemistry modules into their curriculum. These materials, along with outreach activities at local high schools, will encourage the participation of students from primarily undergraduate institutions and other resource-limited environments in computational chemistry-driven research.The goal of this project, led by Dr. Scott Simpson at St. Bonaventure University, is to explore the limits of the "molecular corking effect" to control hydrogen spillover on single-atom alloys. Diatomic hydrogen introduced to a palladium/copper or platinum/copper single-atom alloy will adsorb at the surface, where the hydrogen-hydrogen bond will be cleaved by the catalytically-active metal. The dissociated atomic hydrogen spills over on the noble metal surface. Subsequent selective adsorption of a poisoning ligand to the catalytically-active metal prevents the dissociated hydrogen from desorbing and reforming diatomic hydrogen. This ligand, thus, serves as a "molecular cork" until heat is applied to dissociate the ligand, liberating hydrogen gas from the surface. This phenomenon can potentially be leveraged in hydrogen storage applications. However, single-atom alloys are a relatively new class of materials, and the many factors governing the molecular corking effect are unknown. Accordingly, the research plan is designed to (1) generate fundamental knowledge of how molecular corks interact with surfaces, (2) explore the viability of various molecular corks for hydrogen storage, and (3) examine the impacts of molecular cork adsorption on single-atom alloys aggregation. State-of-the-art computational methods, including density functional theory calculations and kinetic Monte Carlo simulations, will be employed to reveal the molecular-level phenomena underlying hydrogen spillover and desorption from single-atom alloys. Experimental validation via scanning tunneling microscopy and temperature-programed desorption studies will be conducted through collaborations. The outcomes of this project have the potential to advance hydrogen storage technologies and will be broadly relevant to the interfacial engineering and heterogenous catalysis research communities.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.