Molecular design of O3 and NO2 sensor devices based on a novel heterostructured N-doped TiO2/ZnO nanocomposite: a van der Waals corrected DFT study

We have presented a density functional theory study of the adsorption properties of NO2 and O3 molecules on heterostructured TiO2/ZnO nanocomposites. The most stable adsorption configurations, adsorption energies and charge transfers were calculated. The electronic properties of the complex TiO2/ZnO heterostructures were described using the density of states and molecular orbital analyses. For NO2 adsorption, it was found that the oxygen atoms preferentially move towards the fivefold coordinated titanium atoms, whereas the nitrogen atom binds to the zinc atom. In the case of O3 adsorption, the side oxygen atoms bind to the fivefold coordinated titanium sites, and the central oxygen atom does not contribute to the adsorption any longer. Thus, the interaction of NO2 and O3 molecules with TiO2 side of nanocomposite is strongly favored. On the N-doped TiO2/ZnO nanocomposites, the adsorption process is more energetically favorable than that on the pristine ones. The N-doped nanocomposites are far more sensitive to gas detection than the undoped ones. In TiO2/ ZnO nanocomposites, the interactions of gas molecule and TiO2 are stronger than those between gas molecule and bare TiO2 nanoparticles, which reveals that ZnO is conducive to the interaction of NO2 and O3 molecules with TiO2 nanoparticles. Our theoretical results suggest multicomponent TiO2/ZnO nanocomposite as a potential material for gas sensing application.