Anchoring platinum on graphene using metallic adatoms: A first principles investigation

First principles calculations based on spin-polarized density functional theory were used to identify metallic adatoms that would strengthen the Pt(111)/graphene interface (with a low work of separation of 0.009Jm ²), when the adatom was placed between the Pt(111) and the graphene. It was shown that the strength of the Ptadatom bond, which had a metallic character, increased with the amount of charge transferred from the adatom to the Pt. The carbonadatom bond, on the other hand, had a mixed ionic and covalent character and was weaker than the Ptadatom bond for each of the 25 elements considered. Consequently, the total Pt(111)/graphene interface strength and, hence, the anchoring effect of the adatom were controlled by the carbonadatom bond strength. Metals with unfilled d orbitals increased the Pt/graphene interface strength to above 0.5Jm ². The carbonadatom bond strength was proportional to the ratio between the charge transferred from the adatom to the graphene (ΔZ ^C) and the charge transferred to the Pt surface (ΔZ ^Pt); i.e., the ΔZ ^C/ΔZ ^Pt ratio defined the ability of an adatom to anchor Pt to graphene. For Ir, Os, Ru, Rh and Re, ΔZ ^C/ΔZ ^Pt>1.0, making these elements the most effective adatoms for anchoring Pt to graphene. © 2012 IOP Publishing Ltd.