A DFT-D2 study on adsorption of iodonitromethane on doped (B, N & Fe) and Fe-functionalized monovacancy graphene...

INM is a toxic halogen nitromethane and disinfection by-product that is very dangerous to the environment and human beings since it is highly cytotoxic and mutagenic. Here, we examine the adsorption of INM on pristine graphene (PG), monovacancy graphene (MVG), nitrogen-doped vacuity graphene (NVG), and boron-doped vacuity graphene (BVG) and their Fe-functionalized analogs (FeG, FNG, and FBG) using density functional theory (DFT). To explain the adsorption mechanism, adsorption energy calculations, Hirshfeld charge transfer analysis, and electronic structure evaluations, such as band gap, density of states (DOS), and partial DOS (PDOS), were used. INM shows poor physisorption on PG, MVG, and NVG, whereas BVG shows stronger chemisorption by direct bonding. Fe adsorption is very important in increasing the strength of adsorption and redistribution of charges which results in strong electronic structure alterations. Then Fe-doped vacancy graphene is explored with respect to band gap, DOS, and PDOS plots. INM is then adsorbed on the surface. Fe-doped vacancy graphene (FVG) exhibits the highest adsorption energy and the largest electronic modification which validates the fact that it is strongly chemisorptively interacting. These findings emphasize FVG as a promising and efficient material to remove toxic INM in the contaminated environment and to develop graphene-based adsorbents to clean up the environment.

All calculations were done in the DMol³ package of Materials Studio with a doubled numerical plus polarization (DNP) basis set and DFT semicore pseudopotentials (DSPP). The GGA-PBE functional was used with the DFT-D correction by Grimme which considered the effects of exchange-correlation and dispersion. Spin-unrestricted geometry optimizations were driven to strict energy (2.0 × 10^-5 Ha) and force (4 × 10^-3 Ha Å^-1) convergence factors, on a grid of 6 × 6 × 1 Monkhorst Pack k-points. To assess charge transfer and bonding properties, Hirshfeld charge and Mayer bond order analyses were used.