DFT Study of the Hydrogen Spillover Mechanism on Pt-Doped Graphite

Abstract

The mechanism of hydrogen storage by atomic hydrogen spillover on a Pt-doped graphite (0001) surface was studied by means of density functional theory. The coronene molecule and a Pt 4 cluster were used as primary models for the carbon surface and the metal nanoparticles, respectively. It was found that H 2 dissociates spontaneously on a Pt cluster, but the dissociated H atoms have to overcome excessively large energy barriers (>60 kcal/mol) to migrate from Pt to the graphite surface. H atoms on a graphite (0001) surface can be either chemisorbed or physisorbed. The transition from the chemisorbed to the physisorbed state happens at sufficiently high rates. In the physisorbed state, H atom diffusion is essentially free of energy barriers. Physisorbed H atoms readsorb selectively adjacent to other chemisorbed H atoms. Our results indicate that H atom migration from a transition metal to the graphite surface is rate-limiting in the overall spillover process. The implications of the findings are discussed.

On the performance of van der Waals corrected-density functional theory in describing the atomic hydrogen physisorption on graphite

“…To our knowledge, the only reported DFT + vdW study devoted to the H physisorption on graphite was performed by Psofogiannakis and Froudakis [3]. They used the BP86-GGA functional and the dispersion correction proposed by Grimme [23,24].…”

“…Atomic hydrogen can interact with graphite surface either physically or chemically with adsorption energies of about 0.04 and 0.8 eV, respectively [1][2][3][4]. While the physisorption process is essentially site-independent, the chemisorption takes place exclusively on top with a substantial pull out of the carbon atom involved in the chemical bond.…”

Hydrogen Storage in Pristine and d10-Block Metal-Anchored Activated Carbon Made from Local Wastes

“…Besides, these metallic centers facilitate the dissociation of hydrogen molecules and eventually increase the hydrogen content over the carbon receptor by a spillover mechanism [13].…”

Adsorption and diffusion of atomic hydrogen on a curved surface of microporous carbon: A theoretical study

“…Despite several theoretical studies related to the process of hydrogen spillover [21][22][23][24][25][26][27], only flat surfaces have mostly been considered.…”