We have studied the adsorption of SO2 molecule on the pristine and nitrogen-doped Au decorated TiO2 nanoparticles using density functional theory (DFT) calculations, taking into attention van der Waals (vdW) interactions. Theoretically, it was found that SO2 molecule adsorbs on the Au decorated TiO2 in a bridge geometry. The adsorption of SO2 molecule on both the Au and TiO2 sides were considered. On the TiO2 side, the fivefold coordinated titanium sites were found to be the most stable binding sites, providing double contacting point between the nanoparticle and SO2. The results suggest that the adsorption of SO2 on the N-doped Au decorated TiO2 is more energetically favorable than the adsorption on the pristine one. Thus, nitrogen doping is dominant during the adsorption of SO2. The changes in the electronic structure of the system and the net charge transfer upon adsorption of SO2 molecule were studied in detail. Also, HOMO-LUMO isosurfaces of the adsorption systems were presented for discussion of results. By considering large overlaps in the projected density of states (PDOSs) of the interacting atoms, we found that the molecule is bound most strongly to the Au and fivefold coordinated titanium positions. The inclusion of vdW interactions is important for obtaining final equilibrium adsorption configurations of SO2 on Au decorated TiO2 nanoparticles. Our results thus suggest that N-doped Au decorated TiO2 would be an efficient sensor for SO2 gas detection in the environment.
