Density Functional Theory Study of the Interactions between Triatomic Gas Molecules and Faceted TiO2 Anatase Nanostructures

Using the density functional theory calculations, we investigate the adsorption behaviors ofNO2 and O3 molecules on the pristine and N-doped TiO2 anatase nanocrystals based on theenergetics, structural parameters, charge transfer and electronic structure. We determine the moststable adsorption positions of NO2 and O3 molecules on TiO2 nanocrystals and the styles ofmolecule binding to the surface, and examine the interaction between gas molecules and TiO2.The results suggest that the sensing performance of nitrogen modified TiO2 nanocrystal issuperior to the pristine one, indicating the strong interaction and charge transfer between gasmolecules and N-doped TiO2. Mulliken charge analysis indicates that both NO2 and O3molecules serve as charge acceptors from the TiO2 nanocrystal. The adsorption on the N-dopednanocrystal is more favorable in energy than that on the pristine one, which indicates thatnitrogen doping plays a critical role in the process of adsorption. We further examine thevariation of the electronic structure for gas molecules adsorption on the considered nanocrystals.The charge density difference calculations show that the electronic density increases at themiddle of the newly formed bonds. We also analyzed the molecular orbitals for the studiedsystems, which indicate that the electronic density in the LUMOs is high on the adsorbedmolecules, whereas the HOMOs are mainly localized over the TiO2 nanocrystal. The nontrivialsensitivity and high adsorption ability of N-doped TiO2 nanocrystal represent that it has apotential application in the field of highly efficient gas sensors and high performance catalysts.

Keywords:

TiO2 Nanocrystal , DFT , NO2 , O3 , Adsorption , Charge Density Difference