Selective Hydrogen Adsoprtion in Graphene Rotated Bilayers

TL;DR

This study investigates how atomic hydrogen selectively adsorbs on rotated graphene bilayers, revealing that surface corrugation, electronic density perturbations, and doping significantly influence adsorption energies and behaviors.

Contribution

It provides new insights into the preferential adsorption sites and energy variations in rotated graphene bilayers, considering electronic effects and layer rotation angles.

Findings

Atoms with near AA stacking are most favorable for hydrogen chemisorption.

Adsorption energy varies up to 80 meV between different sites.

Doping and rotation angle significantly affect adsorption energies.

Abstract

The absorption energy of atomic hydrogen at rotated graphene bilayers is studied using ab initio methods based on the density functional theory including van der Waals interactions. We find that, due to the surface corrugation induced by the underneath rotated layer and the perturbation of the electronic density of states near the Fermi energy, the atoms with an almost AA stacking are the preferential ones for hydrogen chemisorption. The adsorption energy difference between different atoms can be as large as 80 meV. In addition, we find that, due to the logarithmic van Hove singularities in the electronic density of states at energies close to the Dirac point, the adsorption energy of either electron or hole doped samples is substantially increased. We also find that the adsorption energy increases with the decrease of the rotated angle between the layers. Finally, the large zero point energy of the C-H bond (${\sim 0.3 eV}$) suggests adsorption and desorption of atomic hydrogen and deuterium should behave differently.