First-principles study of nitrogen and carbon monoxide adsorptions on silicene

Atomic adsorptions of N, C and 0 on silicene and molecular adsorptions of N-2 and CO on silicene have been investigated using the density functional theory (DFT) calculations. For the atomic adsorptions, we find that the N atom has the most stable adsorption with a higher adsorption energy of 8.207 eV. For the molecular adsorptions, we find that the N-2 molecule undergoes physisorption while the CO molecule undergoes chemisorption, the corresponding adsorption energies for N-2 and CO are 0.085 and 0.255 eV, respectively. Therefore, silicene exhibits more reactivity towards the CO adsorption than the N-2 adsorption. The differences of charge density and the integrated charge calculations suggest that the charge transfer for CO adsorption (similar to 0.015e) is larger than that for N-2 adsorption (similar to 0.005e). This again supports that CO molecule is more active than N-2 molecule when they are adsorbed onto silicene.