CO 2 Adsorption over 3 d Transition-Metal Nanoclusters Supported on Pyridinic N 3 -Doped Graphene: A DFT Investigation.

CO 2 adsorption on bare 3 d transition-metal nanoclusters and 3 d transition-metal nanoclusters supported on pyridinic N 3 -doped graphene (PNG) was investigated by employing the density functional theory. First, the interaction of Co 13 and Cu 13 with PNG was analyzed by spin densities, interaction energies, charge transfers, and HUMO-LUMO gaps. According to the interaction energies, the Co 13 nanocluster was adsorbed more efficiently than Cu 13 on the PNG. The charge transfer indicated that the Co 13 nanocluster donated more charges to the PNG nanoflake than the Cu 13 nanocluster. The HUMO-LUMO gap calculations showed that the PNG improved the chemical reactivity of both Co 13 and Cu 13 nanoclusters. When the CO 2 was adsorbed on the bare 3 d transition-metal nanoclusters and 3 d transition-metal nanoclusters supported on the PNG, it experienced a bond elongation and angle bending in both systems. In addition, the charge transfer from the nanoclusters to the CO 2 molecule was observed. This study proved that Co 13 /PNG and Cu 13 /PNG composites are adequate candidates for CO 2 adsorption and activation.