Ab-initio investigation of adsorption of CO and CO2 molecules on graphene: Role of intrinsic defects on gas sensing

We determine the chemical activity of (a) carbon site of pristine graphene (pG), (b) Stone-Wales (SW) defect site, and (c) Single-vacancy of graphene (vG) site towards the adsorption of CO and CO2 molecules, through comparative analysis based on first-principles density-functional calculations incorporating van der Waals (vdW) interactions, but excluding the heat effects (i.e., at T = 0 degrees K). The results show that the chemisorption of both latter molecules to possibly occur only on vG. The response (sensitivity) of vG towards detecting CO molecule was confirmed by the rise of conductance with the increasing CO gas dose. The selectivity was investigated by testing the response of vG towards detecting eight different gases (i.e., CO, CO2, N-2, O-2, H2O, H2S, H-2, and NH3). Three gases are found to exhibit physisorption (namely: N-2, H2O, and H2S) and the other five gases alter chemisorption (namely: CO, CO2, O-2, H-2, and NH3). The chemisorption of CO molecule is distinct by being direct and not involving dissociation. This fact made defected graphene have the highest sensitivity and selectivity towards the detection of CO molecules. (C) 2016 Elsevier B.V. All rights reserved.