A DFT study of Rh clusters on defective SWCNT and graphene

AMBRUSI, R.E.; CARLA R. LUNA; M. SANDOVAL; PABLO BECHTHOLD; PRONSATO M.E.; ALFREDO JUAN

Conferencia; ICASS 2017 : 2nd International Conference on Applied Surface Science; 2017

Transition metal adsorption on carbon nanotubes and on graphene improves hydrogen adsorption and electrical contact, being Rh one possible candidate. In the present work, a study of Rhn (n=1..4) clusters adsorption on SWCNT with a single vacancy (SV) was realized. Rh monomers results on SWCNT and on graphene with and without vacancy defects were compared. First-principles calculations were performed using DFT, implemented in the Vienna Ab initio Simulation Package (VASP) code. Bader method was used for charge distribution calculation. Electronic structure was analyzed by the total density of states (TDOS) and partial density of states (PDOS).SWCNT and graphene with SV tends to form a similar reconstruction of the surface around the vacancy, forming five-member and nine-member rings (Figure 1). A non magnetic SWCNT with SV turns magnetic when Rh adsorbs, but the opposite occur on graphene with SV (Table 1).Rh monomer adsorbed on SWCNT or on graphene with SV locates on the center of the defect (Figure 2). Binding energy of Rh increase 4.89 eV on SWCNT and 6.41 eV on graphene relative to the structures without defects. From TDOS and PDOS curves of Rh adatom on SWCNT with SV, spin up and spin down states have a conductor and n-type semiconductor behavior respectively. A metallic behavior is observed for Rh decorated graphene with SV.When Rhn (n = 2 to 4) adsorb, Rh cluster geometry and C-C, Rh-C, Rh-Rh bond lengths remain practically unchanged (Figure 3 and Table 2). Adsorbed Rh3 and Rh4 clusters, have asymmetrical states around the Fermi level, working like magnetic metal systems. Rh atoms are electron donors, but for adsorbed Rh2 and Rh4 charge polarization occur. From these results, Rh attachment on defective SWCNT induces a considerable magnetic moment with metal behavior for Rh3 and Rh4 clusters, being candidates for nanotube contact. Based on its binding energy, a suitable Rh dispersion can be achieved on graphene with SV, which can be applied for hydrogen storage.