INVESTIGADORES
AMBRUSI Ruben Eduardo
congresos y reuniones científicas
Título:
Ab-initio study of Rh decoration graphene with and without defects for hydrogen adsorption.
Autor/es:
RUBÉN E. AMBRUSI; ROMINA C. LUNA; ALFREDO JUAN; MARÍA E. PRONSATO
Lugar:
Paris
Reunión:
Congreso; European Graphene Forum- EGF 2017; 2017
Resumen:
The application of carbon-based materials in hydrogen storage technology is interesting due to their chemical stability, low weight, high surface area and structure possible to be modified. Among them, graphene became an attractive carbon-based adsorbent since its experimental synthesis in 2004 by Novoselov. Unfortunately, at room temperature, hydrogen molecules adsorb physically on the carbon surface. A way to over-come this situation is by adding transition metal (TM) atoms. However, because the TM?TM interaction is much stronger than the TM-graphene, TM atoms tend to form clusters on the sheet surface decreasing dramatically the hydro-gen storage capacity. To avoid it, a number of methods were attempted to enhance the metal binding, including modification of carbon surfac-es by B and N doping or forming vacancies. In this work we perform first-principles calculations using DFT to evaluate the stability of Rh on graphene with B dopants and various vacancy defects including single vacancy graphene (SVG), 585 and 555-777 types double vacancy graphene (585 DVG and 555-777 DVG), in or-der to prevent Rh aggregation and favored the hydrogen adsorption (Figure 1). Results were compared with those obtained for Rh decorated pristine graphene. Changes in the highest occu-pied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO), were analyzed before and after the Rh adsorption. In addition charge distribution in the adsorption region was obtained by the charge density differ-ence isosurfaces determining the accumulation and depletion charge regions between the Rh and C atoms, reflecting the bonding between Rh and the substrate. Also, the hydrogen adsorption ca-pacity for the different Rh decorated graphene structures was evaluated. Dispersion force con-tribution to the hydrogen adsorption energy was determined quantitatively in order to know whether H2 molecules adsorbed chemically or are controlled by van der Waals forces. Partial den-sity of states (PDOS) for the different systems, were obtained to understand the Rh?C, H2?Rh (adsorbed) and H?H interactions and magnetic effects, before and after Rh and H2 adsorption. When H2 molecules bind to Rh adatoms, an elec-trostatic interaction occurs due to a charge trans-fer from the metal to the graphene surfaces after adsorption. Bonding and Bader charge analysis are also included.