Abstract:
Using density functional theory (DFT), we have explored the structural, electronic, magnetic and optical properties of two-dimensional 3d-transition metal (TM)-embedded graphitic carbon nitride (g-C3N4) sheets. g-C3N4 sheets are structurally modified in different ways depending upon the radius of embedded-TM atoms and the crystal field stabilization energy gained by the corresponding geometry. Bare g-C3N4, which is a wide-gap semiconductor, becomes metallic upon TM inclusion. The d-orbitals of TMs hybridize with the p(pi)-orbitals of the g-C3N4 framework and close the band gap in TM-embedded g-C3N4 (TM-g-C3N4). Interestingly, for V, Cr and Fe embedded g-C3N4, the TM atoms interact ferromagnetically to each other and result in a ferromagnetic ground state. However, Mn couples antiferromagnetically and Cu and Zn are nonmagnetic in the ground state of their corresponding TM-g-C3N4 sheets. Because of structural distortion, Co- and Ni-g-C3N4 do not have a well-ordered magnetic orientation. Performing Heisenberg-model-based Monte Carlo simulations, we predict that V-, Cr- and Fe-g-C3N4 would possess Curie temperatures (T-c) of 205 K, 170.5 K, and 115 K, respectively. Furthermore, these modified g-C3N4 sheets also show prominent absorption at low energy, which evidently confirms their efficient photoabsorption capacity. The present study demonstrates the multifunctional behavior of TM-g-C3N4, which shows significant promise for application in various fields such as in memory devices or for photocatalysis.
