Noble-metal single atom with non-metal co-doped graphene: First-principles investigation of structures, electronic and magnetic properties

The geometric, electronic, and magnetic properties of noble-metal single atom (M = Rh, Pd, Ag, Ir, Pt, and Au) with non-metal (X = B, C, N, and O) co-doped graphene (referred to as MX ₄-G) were thoroughly investigated by using first-principle calculations. Our results demonstrate that Rh, Pd, Ir, Pt, and Au individual atoms cannot be strongly bonded with O ₄-G substrate to form MO ₄-G, and Ag atom cannot be stably anchored on all X ₄-G substrates. The stable MX ₄-G structures in which the lost charges of M atom change with the electronegativity of X atom may exhibit different catalytic activity and selectivity. The ferromagnetic couplings are observed in RhC ₄-G, RhN ₄-G, IrC ₄-G, and IrN ₄-G through spin density analysis, and five different up- and down-spin d orbitals of Rh and Ir atoms should be responsible for the local magnetic moments. The MX ₄-Gs can exhibit metallic, half-metallic, or semiconductor behaviors because their band gaps are sensitively dependent on the atomic types of M and X. Our work provides fundamental insights into the applications of MX ₄-G nanomaterials in various catalytic reactions and novel spintronic devices.