Imaging the dynamics of individual hydrogen atom intercalated between two graphene sheets

TL;DR

This study directly images and analyzes the behavior of individual hydrogen atoms confined between graphene sheets, revealing significantly altered dynamics and reduced dissociation energy compared to hydrogen on external surfaces.

Contribution

It provides the first direct imaging and detailed analysis of hydrogen atom dynamics confined between graphene layers, combining STM measurements with first-principles calculations.

Findings

Intercalated hydrogen exhibits different properties from chemisorbed hydrogen.

Reduced potential barriers facilitate atomic migration.

Dissociation energy is significantly lower at the interface.

Abstract

The interlayer gallery between two adjacent sheets of van der Waals materials is expected to modify properties of atoms and molecules confined at the atomic interfaces. Here, we directly image individual hydrogen atom intercalated between two graphene sheets and investigate its dynamics by scanning tunnelling microscope (STM). The intercalated hydrogen atom is found to be remarkably different from atomic hydrogen chemisorbed on external surface of graphene. Our STM measurements, complemented by first-principles calculations, show that the hydrogen atom intercalated between two graphene sheets has dramatically reduced potential barriers for elementary migration steps. Especially, the confined atomic hydrogen dissociation energy from graphene is reduced to 0.34 eV, which is only about a third of a hydrogen atom chemisorbed on graphene. This offers a unique platform for direct imaging of the atomic dynamics of confined atoms. Our results suggest that the atomic interfaces of van der Waals materials may provide a confined environment to tune the interfacial chemical reactions.