Adsorption performance of SO2 gases over the transition metal/P-codoped graphitic carbon nitride: A DFT investigation

The adsorption performance of SO2 on the P-doped and transition metal (TM)/P-codoped graphitic carbon nitride (gCN) systems (TM = Co, Rh, and Ir elements) were studied by DFT methods. The adsorption energy (E-ads) results demonstrated that the interaction energy between SO2 and TM/P-codoped gCN systems are stronger than that of the pristine gCN. Furthermore, it was found that SO2 molecule prefers to adsorbed on the Ir/P-codoped gCN with superior E-ads of -3.52 eV. Hence, the Ir/P-codoped gCN is a suitable candidate for removing and detecting SO2 molecules from the atmosphere, in comparison with that of the other adsorbents. Besides, the results revealed that the presence of SO2 molecules over surface of doped and codoped gCN systems led to considerable changes in the magnetic, and structural characteristics of these systems. Furthermore, the Lowdin charges analysis demonstrated that with adsorption of SO2 over the TM/P-codoped gCN systems, electrons remarkable transfer from the TM/P-codoped systems to SO2 gas molecules owing to the strong adsorption of this gas. The results of electronic band structure displayed that with adsorption of SO2 gas and also codoping of TM/P elements, the electrical conductivity of gCN systems significantly decreased owing to the induced new impurity energy states near the Fermi energy level (E-f). The results of partial density of states (PDOS) plots for the P-doped, TM/P-codoped, and SO2-adsorbed gCN systems revealed that the sharp peak are localized near the E-f in SO2-adsorbed Ir/P-codoped system, which confirmed the strong interaction between SO(2)gas molecules and this system. Thus, it can be deduced that the Ir/P-codoped system with the highest E-ads be efficiently used for the removing and sensing of SO2 gas from the environment.