Imaging covalent bond formation by H atom scattering from graphene

Abstract

Viewing the atomic-scale motion and energy dissipation pathways involved in forming a covalent bond is a longstanding challenge for chemistry. We performed scattering experiments of H atoms from graphene and observed a bimodal translational energy loss distribution. Using accurate first-principles dynamics simulations, we show that the quasi-elastic channel involves scattering through the physisorption well where collision sites are near the centers of the six-membered C-rings. The second channel results from transient C–H bond formation, where H atoms lose 1 to 2 electron volts of energy within a 10-femtosecond interaction time. This remarkably rapid form of intramolecular vibrational relaxation results from the C atom’s rehybridization during bond formation and is responsible for an unexpectedly high sticking probability of H on graphene.

Ring Polymer Molecular Dynamics in Gas–Surface Reactions: Inclusion of Quantum Effects Made Simple

“…Next, we discuss a possible reason for the less satisfactory performance of RPMD at Ei =0.6~1.0 eV. Indeed, similar phenomenon has been observed in recent NE-RPMD calculations for H scattering on graphene 29 , where the RPMD calculated sticking probabilities at high incidence energies are also generally lower than classical ones (note that there is no internal state and ZPE for hydrogen atom). These authors offered no explanation for this difference in that work.…”

“…This procedure not only correctly samples the Boltzmann weight in the correlation function, but also ensures that each new NVE trajectory explores a different region of microcanonical phase space 11 . Although originally proposed for calculating correlation functions, this procedure has been successfully used in recent direct dynamics simulations 15,29 , giving rise to the proper initial conditions for NVE dynamics calculations. To check this ability, we plot in Fig.…”

“…gas phase reactions [27][28] and hydrogen diffusion on metal surfaces 29 . More recently, Miller and coworkers showed that RMPD could be also used in non-equilibrium conditions 30 , for example, in the H atom scattering on graphene 31 .…”

“…Taking the internal excitation at a given temperature into account, albeit approximately, RPMD results agree rather well with QD ones. Although the NE-RPMD method is validated here within BOSS approximation, it is scalable to include lattice motion given its trajectory-based nature 29 , when combined with recently developed molecule-surface PESs explicitly involving the surface DOFs 51 . Incorporating the ZPE of the surface will be another advantage of RPMD superior to QCT.…”

High on-off ratio graphene switch via electrical double layer gating

“…In other work, it was shown that weak molecular bonds can form at the EDL interface, and nominal activation and deactivation energies can be used to control the molecular bonding between the ions and the substrate [23]. Furthermore, scattering experiments with hydrogen and graphene showed that hydrogen atoms possess a high sticking probability with graphene: C-H bonds formed within 10fs of interaction time [24]. Both of these studies support the notion of electrochemically generating ions within the liquid dielectric, providing an activation energy via electric field to form weak molecular bonds with graphene, and providing a deactivation energy to remove those molecular bonds.…”