Triple-Doped Monolayer Graphene with Boron, Nitrogen, Aluminum, Silicon, Phosphorus, and Sulfur.

The structure, stability, electronic properties and chemical reactivity of X/B/N triple-doped graphene (TDG) systems (X=Al, Si, P, S) are investigated by means of periodic density functional calculations. In the studied TDGs the dopant atoms prefer to be bonded to one another instead of separated. In general, the XNB pattern is preferred, with the exception of sulfur, which favors the SBN motif. The introduction of a third dopant results in a negligible decrease of the cohesive energies with respect to the dual-doped graphene (DDG) counterparts. Thus, it is expect that these systems can be prepared soon. For SiNB TDG, the introduction of the B dopant reduces the gap opening at the K point and restores the Dirac cones that are destroyed in SiN DDG. On the contrary, for PNB TDG, the bandgap is increased with respect to PN DDG, probably because the introduction of B weakens the PN bonding, and thus the electronic structure is rather similar to that of P-doped graphene. Finally, with regard to the reactivity of the TDGs, for AlNB, PNB, and SNB the carbon atoms are more reactive than in their AlN, PN, and SN DDG counterparts. On the contrary, the reactivity of SiNB is lower than that of SiN DDG. Therefore, to increase the reactivity of graphene, Al, P, and S should be combined with BN motifs.