First–Principle Investigation of Functionalized Graphene Oxides as Advanced Adsorbents for Hazardous Gases: Insights Into H 2 S, NO 2 , and SO 2 Capture

ABSTRACT Graphene oxide (GO) is a promising carbon‐based adsorbent due to its active oxygen functional groups and tunable electronic properties. This study employs density functional theory (DFT) at the B3LYP/6‐31G* level to investigate the adsorption of H 2 S, NO 2 , and SO 2 on four functionalized GO models: surface hydroxyl‐functionalized GO (SOH‐GO), surface epoxy‐functionalized GO (SO‐GO), edge hydroxyl‐functionalized GO (EOH‐GO), and edge epoxy‐functionalized GO (EO‐GO). The strongest adsorption energies were obtained for SOH‐GO‐H 2 S (−2.68 kcal/mol), EOH‐GO‐NO 2 (−5.08 kcal/mol), and EO‐GO‐SO 2 (−4.87 kcal/mol). Frontier Molecular Orbital (FMO) analysis showed notable band‐gap reduction, with EO‐GO‐SO 2 decreasing to 1.08 eV, indicating enhanced charge transfer. Density of States (DOS) profiles revealed increased peak intensities, such as SOH‐GO‐H 2 S rising from 2, 1, and 5 eV −1 to 3, 2, and 6 eV −1 . Chemical hardness values were the highest for SOH‐GO‐H 2 S ( η = 1.04 eV) and EOH‐GO‐NO 2 ( η = 0.83 eV), while EO‐GO‐SO 2 exhibited maximum softness ( β = 5.71 eV). The UV–visible bathochromic shifts up to 651 nm validated the adsorption mechanism. These findings provide strong computational insight for designing selective GO‐based gas sensors.