INVESTIGADORES
VERDINELLI Valeria
congresos y reuniones científicas
Título:
Hydrogen adsorption on carbon nanotubes decorated with Pd, Rh and Ru: a DFT study
Autor/es:
ROMINA LUNA, VALERIA VERDINELLI, ESTEFANÍA GERMÁN, IGNACIO LÓPEZ-CORRAL AND CAROLINA PISTONESI
Lugar:
Montevideo
Reunión:
Workshop; V Workshop on Novel Methods for Electronic Structure Calculations; 2013
Institución organizadora:
Facultad de Química, Universidad de la República
Resumen:
In this work we studied the adsorption of hydrogen onto single-walled carbon nanotubes (SWCNTs) decorated with different transition metals: Pd, Rh and Ru. Spin-polarized density functional theory (DFT) simulations were performed using VASP and SIESTA codes. The exchange-correlation term was calculated with the generalized gradient approximation (GGA). We selected a (8,0) zigzag SWCNT modeled by a supercell containing 64 C atoms. Several decoration sites on the nanotube surface were investigated before atomic or molecular hydrogen adsorption. According to previous reports, the most stable location of a single Pd atom on the SWCNT is the regular bridge site above an axial C-C bond, with a binding energy of Eb(Pd)= -1.80 eV. Adsorption of atomic hydrogen on the Pd/SWCNT system is possible, but the classic HPdH hydride is unstable on the nanotube surface. In effect, the preferential carbon-supported PdH2 system is a Kubas-type dihydrogen complex, with a binding energy of Eb(H2)= -0.66 eV. Although in this configuration the H-H bond is elongated due to the Kubas bonding, the H2 molecule is not dissociated. The adsorption of a terminal Pd-H-H coordination structure leads to a much lower Eb(H2). We also found that two donor-acceptor interactions are present in the H2/Pd/SWCNT Kubas-type system: (1) Pd 4d to C 2s donation and C 2p to Pd 5s back-donation; and (2)H2 sigma to Pd 5s donation and Pd 4d to H2 sigma* back-donation. Preliminary results involving Ru/SWCNT and Rh/SWCNT systems, which present magnetic effects, show that hydrogen adsorption is stronger than on Pd/SWCNT.