Structural and electronic properties of nitrogen-doped TiO2 nanocrystals and their effects on the adsorption of CH2O and SO2 molecules investigated by DFT

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The interaction of CH2O and SO2 molecules with TiO2 anatase nanocrystals were studied using the density functional theory calculations. Several adsorption positions of CH2O and SO2 molecules on the TiO2 surface were examined in detail. The results include the calculations of the adsorption energies, electronic structures and structural parameters of the adsorption systems. We found that both oxygen and carbon atoms of the CH2O molecule interact with TiO2 surface, while the hydrogen atoms does not contribute to the adsorption process. Besides, the oxygen atom of SO2 molecule strongly interacts with the TiO2. The adsorption of CH2O and SO2 on the N-doped surface is more favorable in energy than the adsorption on the pristine surface, suggesting that the N-doped nanocrystal acts as an appropriate sensing material. The substantial changes in the electronic structure near the fermi level reveal that the nitrogen modified TiO2 would be a promising sensing material for CH2O and SO2 detection. The charge density difference calculations reveal that the electronic density increases at the middle of the newly formed bonds, as evidenced by the significant overlaps of the projected density of states between the interacting atoms. Besides, the distribution of spin densities reveals that the magnetization was mainly located on the adsorbed CH2O molecule, being useful for the design and characterization of highly efficient gas sensors.