A van der Waals DFT study of PtH2 systems absorbed on pristine and defective graphene

IGNACIO LÓPEZ CORRAL; SEBASTIÁN PIRIZ; RICARDO FACCIO; ALFREDO JUAN; MARCELO AVENA

APPLIED SURFACE SCIENCE

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2016 vol. 382 p. 80 - 87

0169-4332

Weused a density functional that incorporates the van der Waals interactions tostudy hydrogen adsorption onto Pt atoms attached to carbon-vacancies ongraphene layers, considering molecular and dissociated hydrogen-platinumcoordination structures. PtH2 complexes adsorbed on several sites ofpristine graphene were also studied for comparison. Our results indicate that botha Kubas-type dihydrogen complex and a classic hydride without H-H bond are the preferential PtH2systems on the vacancy site of graphene, with a binding energy of about -0.34 eV. In contrast, the Kubas complex isunstable onto pristine graphene and the hydride is obtained at all adsorptionsites. Our simulations suggest that the C-vacancy decreases the reactivity ofthe metal decoration, leading to non-dissociative hydrogen adsorption. The H2molecule is oriented almost perpendicular to the outermost C-Pt bond, interacting also with the graphene surfacethrough sigma-H and  pi-C states. This stabilization of the Kubas-typecomplex could play a very important role for hydrogen storage in Pt-decorated carbonadsorbents with vacancies.