Mechanism of Nitrogen-Concentration Dependence on pH Value: Experimental and Theoretical Studies on Nitrogen-Doped TiO₂

Abstract

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 TiO 2 . 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 NH x -containing species in the dried precipitate from the hydrolysis.) 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 TiO 2 surfaces were calculated to study the ability of NO x to be incorporated into the TiO 2 matrix under different pH conditions. Finally, we propose three processes as being responsible for the dependence of the nitrogen concentration on the pH value.

Characterization and photoactivity of Pt/N-doped TiO2 synthesized through a sol–gel process at room temperature

“…Here, the doping concentration and visible-light absorption of N-doped TiO 2 varied as a function of the sintering conditions. Sun et al (2008) synthesized N-doped TiO 2 through hydrolysis of TiCl 4 with nitrogen precursors at pH 3.5-9.5; this experiment demonstrated that the N concentration of the samples depends on the pH. The properties and photoactivities of N-doped TiO 2 prepared through the sol-gel method could be affected by the pH, treatment temperature, solvent composition, nitrogen precursors, and calcination temperature.…”

Low temperature hydrothermal synthesis of N-doped TiO2 photocatalyst with high visible-light activity

“…9), there is no obvious difference in their optical absorption properties. However, significant difference of nitrogen concentration in the catalysts can be observed, and it can be regarded as the reason of the effects of pH [38,40,49]. According to elemental analysis, the nitrogen contents were about 0.93, 1.90, 0.15 at% for N-TiO 2 -3, N-TiO 2 -7 and N-TiO 2 -10, respectively.…”

“…It is interesting that the pH value in the preparation process greatly affected the doping nitrogen concentration and consequently on the photocatalytic activity of N-TiO 2 photocatalysts [40,48,49]. In order to investigate the effects of pH value in the process of preparing the photocatalysts on the photocatalytic activity, the pH value of the TiO 2 sol was adjusted by HNO 3 solution Fig.…”

Enhanced performance of g-C3N4/TiO2 photocatalysts for degradation of organic pollutants under visible light

“…Many investigations have been implemented on the development of photocatalyst materials, such as metal oxides, sulfides and nitrides, among which titanium dioxide (TiO 2 ) has demonstrated to be the most popular photocatalyst for potential commercialization [2][3][4][5]. TiO 2 , a n-type semiconductor, has been then widely used owing to the high efficiency, low cost, non-toxicity and long-term stability [6][7][8][9]. However, the large band gap energy of 3.2 eV of TiO 2 (anatase) and the high recombination rate of electron-hole pairs have hindered its A C C E P T E D M A N U S C R I P T ACCEPTED MANUSCRIPT 4 wide applications.…”

“…The peaks of pure TiO 2 at 25.3, 37.8, 48.0, 53.9, 55.1, and 62.7 º correspond to the (101), (004), (200), (105), (211) and (204) crystal planes of anatase TiO 2 (JCPDS 21-1272)[33]. The crystal size of TiO 2 particles was estimated to be 14.2 nm according to Scherrer equation[8]. The g-C 3 N 4 characteristic peaks were found in all g-C 3 N 4 /TiO 2 photocatalysts.…”