H2 hitting on graphene supported palladium cluster: molecular dynamics simulations

Dissociative adsorption of impinging gas-phase molecular hydrogen (H 2 ) on a palladium cluster (Pd 4 ) supported on defective graphene (C 47 ) was studied by periodic density functional theory molecular dynamics simulations. The H 2 on Pd 4 /C 47 collision dynamics were investigated without any particular constraint, except for the Born–Oppenheimer approximation. The study, which had mostly method-testing aims, provided, anyway, valuable information about the collision kinetics of gas-phase molecular hydrogen. This was treated as an impacting projectile having different kinetic energy values. At lower kinetic energies, sticking was ruled by steering effects imputable to the Pd cluster that easily reoriented the incoming hydrogen molecule to the metallic surface sites, favoring fragmentation hence adsorption. Sticking decreased at higher kinetic energies for which the very fast corresponding projectile acquired a kind of elusiveness toward the metallic surface that for this was not able to steer and adsorb the gas-phase hydrogen molecule. Interestingly, altered steering effects, in this case, ruled by already adsorbed surface hydrogen, seemed to play a decisive role in refocusing both H 2 hitting and sticking on the supported palladium surface, irrespective of the energy characterizing the impinging gas-phase molecules.