Sensitivity of SnO2 nanoparticles/reduced graphene oxide hybrid to NO2 gas: a DFT study

The sensitivity of SnO 2 nanoparticles/reduced graphene oxide hybrid to NO 2 gas is discussed in the present work using density functional theory (DFT). The SnO 2 nanoparticle shapes are taken as pyramids, as proved by experiments. The reduced graphene oxide (rGO) edges have oxygen or oxygen-containing functional groups. However, the upper and lower surfaces of rGO are clean, as expected from the oxide reduction procedure. Results show that SnO 2 particles are connected at the edges of rGO, making a p-n heterojunction with a reduced agglomeration of SnO2 particles and high gas sensitivity. The DFT results are in good agreement with the experimental characterization of both SnO 2 and rGO using energy gap and X-ray photoelectron spectroscopy (XPS) values. Gibbs free energy, enthalpy, and entropy of the various considered reactions are calculated. Results show that the sensitivity of the rGO/SnO 2 hybrid to NO 2 gas is the result of the interplay of the dissociation and oxidation reactions of NO 2 gas. The sensitivity of the rGO/SnO 2 hybrid to NO 2 increases with temperature until the NO 2 dissociation in the air reduces the concentration of NO 2 .