  Defect is no longer deemed an adverse aspect of graphene. Contrarily, it can
pave ways of extending applicability of graphene. Here, we discuss the effects
of three types of defects on graphene: carbon deficiency, adatom (single Fe)
dopant and introduction of functional groups (carboxyl, pyran group) on NO2 gas
adsorption via density functional theory method. We have observed that the
unsaturated carbon in defected graphene is highly active to attract NO2
molecules. Our study suggests that introducing Fe on graphene can enhance the
NO2 adsorption process. Adsorption energy calculations suggest the enhancement
in NO2 adsorption is more profound for Fe-doped mono and tetra vacant graphene
than Fe doped bi- and tri-vacant graphene. This study could potentially be
useful in developing adsorption-based applications of graphene.
