Transition metal adatoms on graphene: A systematic density functional study

Transition Metal (TM) atoms adsorption on graphene results in a tuning of their electronic, magnetic, storage, sensing, and catalytic properties. Herein we provide a thorough density functional theory study, including dispersion, of the structural, energetic, diffusivity, magnetic, and doping properties for all 3d, 4d, and 5d TM atoms adsorbed on graphene. TMs prefer to sit on hollow sites when chemisorbed, but on bridge or top sites when physisorbed; which is the case of atoms with d5 and d10 configurations. Diffusion energy barriers follow the adsorption energy trends. Dispersive forces simply increase the adsorption strength by ∼0.35 eV. Adatom height seems to be governed by the bond strength. All TMs are found to n-dope graphene, except Au, which p-dopes. The electron transfer decays along the d series due to the electronegativity increase. Early TMs infer noticeable magnetism to graphene, yet for elements with more than five electrons in the d shell the local magnetic moments abruptly decay to low or zero values. Experimental observations on adatom position, height, temperature clustering and Ostwald ripening, p- or n-doping, or the electronic configuration can be rationalized by present calculations, which deliver a solid theoretical ground from which experimental features can be interpreted and discussed.