文摘
Experiments and density functional theory (DFT) calculations were combined in an attempt to investigate the origin of the differences in nitrogen concentration incorporated by N-doped TiO2. X-ray photoelectron spectroscopy (XPS), UV−vis diffusive reflectance spectra (UV−vis), and photodegradation experiments were conducted to set some premises for DFT calculations. Fourier transform infrared (FT-IR) spectroscopy was applied to investigate the NHx-containing species in the dried precipitate from the hydrolysis. [Ti(H2O)a(NH3)b(OH)cCld](4−c−d) (a + b + c + d = 6) is defined as the Ti complex produced by the hydrolysis process, and its pH-dependent character was further determined by Gibbs energy calculations for the reaction based on those of related equations. Adsorption energies of NO on TiO2 surfaces were calculated to study the ability of NOx to be incorporated into the TiO2 matrix under different pH conditions. Finally, we propose three processes as being responsible for the dependence of the nitrogen concentration on the pH value.