Chemical functionalization of pyridine-like and porphyrin-like nitrogen-doped carbon (CNx) nanotubes with transition metal (TM) atoms: a theoretical study

It is well known that chemical functionalization of carbon nanotubes (CNTs) can offer an effective route to modify their properties, thus significantly widening their application areas. In the present work, through spin-polarized density functional theory (DFT) calculations, we have systemically studied the chemical functionalization of pyridine-like and porphyrin-like nitrogen-doped carbon (CNx) nanotubes with 13 different transition metals (TMs = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Pt, Pd, and Au). Particular attention is paid to searching for the most stable configurations, calculating the corresponding binding energies, and exploring the effects of the chemical functionalization of TMs on the electronic properties of the two CNx nanotubes. We find that (1) due to the strong interaction between the d orbitals of TMs and the p orbitals of N atoms, the binding strengths of TMs with the two CNx nanotubes are significantly enhanced when compared to the pure CNTs; (2) the electronic properties of CNx nanotubes can be effectively modified in various ways, which are strongly dependent on the adsorbed TMs.