Physisorption and Diffusion of Hydrogen Atoms on Graphite from Correlated Calculations on the H−Coronene Model System

Abstract

Correlated, counterpoise corrected wave function calculations on the hydrogen-coronene system are used to investigate the energy landscape and the dynamic behavior of hydrogen atoms physisorbed on graphite. The adopted MP2 correlation level, employing the aug-cc-pVDZ basis set augmented with bond functions, has been selected after extensive investigation on the smaller hydrogen-benzene system. The computed physisorption energy (39.7 meV) is in excellent agreement with the existing experimental value of (39.2 ( 0.5) meV for a graphite single layer (Ghio, E.; Mattera, L.; Salvo, C.; Tommasini, F.; Valbusa, U. J. Chem. Phys. 1980, 73, 557) and makes one confident of the computed barriers to diffusion. A simple, analytical expression of the corrugated potential energy surface fitted to the calculated energy values is then used in 3D quantum dynamical calculations of the tunneling contribution to the diffusion coefficient. Results show that hydrogen atoms physisorbed on graphite are highly mobile on the surface even at T ) 0 K. This suggests that hydrogen formation in cold, interstellar clouds can indeed occur down to very low temperatures through recombination of hydrogen atoms previously physisorbed on the surface of dust grains.

Stability of hydrogenation states of graphene and conditions for hydrogen spillover

“…25,26 An additional energy component comes from the strain in the C-C bond. The carbon atoms to which hydrogen adatoms are bonded have sp 3 states, thereby inducing strain in neighboring C-C bonds. The energy difference between ortho(uu) and ortho(ud) suggests the strain effect: two C atoms in the ortho(ud) configuration better fit the carbon sp 3 bonds and are less strained.…”

“…1,2 The predominance of molecular hydrogen in interstellar media has been explained by the interplay between chemisorption and physisorption modes of hydrogen atoms onto graphene. 3,4 Hydrogen-induced defects in graphene have been investigated with respect to metal-free magnetism and band-gap engineering. 5,6 Even greater interest comes from the field of hydrogen storage.…”

Quantum dynamics of hydrogen atoms on graphene. I. System-bath modeling

“…[3][4][5] The energetics of hydrogen adsorption has been extensively studied, mostly at the Density Functional Theory (DFT) level with the periodic supercell approach [6][7][8][9][10] and more lately with some accurate wavefunction calculations on cluster models. [11][12][13][14] Many different aspects of hydrogen adsorption have been addressed, including adsorption and diffusion in the a) Electronic mail: matteo.bonfanti@unimi.it b) Electronic mail: rocco.martinazzo@unimi.it shallow physisorption well, 11 single and multiple adsorption in the chemisorption well, 9,15-17 carbon vacancy hydrogenation, 18 and binding to edges. 13,19 All these possibilities determine a vast variety of cases which can be well interpreted and rationalized in terms of electronic and structural effects.…”

“…While the energetics of hydrogen adsorption has been well understood and the dynamics of sticking and diffusing hydrogen in the ∼40 meV physisorption state have been accurately described, 11,[20][21][22] there are still unsettled issues concerning chemisorption that need further investigations. First, the accurate value of the barrier height is still not clear.…”

Cooperative Interplay of van der Waals Forces and Quantum Nuclear Effects on Adsorption: H at Graphene and at Coronene

“…Hydrogen adsorption on carbon based materials such as graphite and graphene is relevant to hydrogen storage, 9 band gap engineering, [10][11][12][13] and potentially as the first step in H 2 formation in the interstellar medium. [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30] Although there is enormous interest in H adsorption on carbonaceous surfaces, with graphene, graphite and polycyclic aromatic hydrocarbons (PAHs) being the most widely studied model systems, we still don't fully understand the seemingly simple process of how a single H atom adsorbs on the surface.…”