Quantum Tunneling Enhanced Hydrogen Desorption from Graphene Surface: Atomic versus Molecular Mechanism

TL;DR

This study investigates hydrogen desorption from graphene, highlighting quantum tunneling's role at low temperatures and comparing atomic versus molecular mechanisms for monomers and dimers.

Contribution

It provides first-principles analysis of hydrogen desorption mechanisms, emphasizing the impact of quantum tunneling and identifying temperature-dependent dominant pathways.

Findings

Quantum tunneling dominates at low temperatures.

Desorption mechanism switches from molecular to atomic above certain temperatures.

Different critical temperatures for H and D desorption mechanisms.

Abstract

We study the desorption mechanism of hydrogen isotopes from graphene surface using first-principles calculations, with focus on the effects of quantum tunneling. At low temperatures, quantum tunneling plays a dominant role in the desorption process of both hydrogen monomers and dimers. In the case of dimer desorption, two types of mechanisms, namely the traditional one-step desorption in the form of molecules (molecular mechanism), and the two-step desorption in the form of individual atoms (atomic mechanism) are studied and compared. For the ortho-dimers, the dominant desorption mechanism is found to switch from the molecular mechanism to the atomic mechanism above a critical temperature, which is respectively ~ 300 K and 200 K for H and D.