CAREER: Investigating the Molecular Corking Effect for Potential Hydrogen Storage

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.