Highly Efficient Low-Temperature N-Doped TiO2 Catalysts for Visible Light Photocatalytic Applications

Abstract

In this paper, TiO2 prepared with an aqueous sol-gel synthesis by peptization process is doped with nitrogen precursor to extend its activity towards the visible region. Three N-precursors are used: urea, ethylenediamine and triethylamine. Different molar N/Ti ratios are tested and the synthesis is adapted for each dopant. For urea- and trimethylamine-doped samples, anatase-brookite TiO2 nanoparticles of 6–8 nm are formed, with a specific surface area between 200 and 275 m2·g−1. In ethylenediamine-doped samples, the formation of rutile phase is observed, and TiO2 nanoparticles of 6–8 nm with a specific surface area between 185 and 240 m2·g−1 are obtained. X-ray photoelectron spectroscopy (XPS) and diffuse reflectance measurements show the incorporation of nitrogen in TiO2 materials through Ti–O–N bonds allowing light absorption in the visible region. Photocatalytic tests on the remediation of water polluted with p-nitrophenol show a marked improvement for all doped catalysts under visible light. The optimum doping, taking into account cost, activity and ease of synthesis, is up-scaled to a volume of 5 L and compared to commercial Degussa P25 material. This up-scaled sample shows similar properties compared to the lab-scale sample, i.e., a photoactivity 4 times higher than commercial P25.

Modified Titanium Dioxide for Photocatalytic Applications

“…This can be ascribed to the impurity states which are near the valence band edge, however, they do not act as charge carriers, and their role as recombination centres might be minimized [53]. As shown in Figure 2, the mixing of the p states of [71]. N-TiO 2 photocatalyst reduces the oxygen energy vacancies from 4.2 to 0.6 eV, suggesting that N favors the formation of oxygen vacancies [72].…”

Visible Light Sensitive SnO2/ZnCo2O4 Material for the Photocatalytic Removal of Organic Pollutants in Water

“…A comparison with commercial Evonik P25 shows that the ZnCo2O4 based catalysts are more active under visible light with a PNP degradation rate three to six times higher than P25 for all samples (Figure 9). The PNP degradations can be compared to previous modified-TiO2 materials under similar photocatalytic conditions [53,54]: In these works, visible activated TiO2 doped with Fe and N reached 42 and 69% of PNP degradation respectively with the best materials after 24 h of visible illumination. In this work, the highest PNP degradation was obtained with ZnCo2O4/SnO2-20% reaching 67% after 24 h of illumination.…”

“…The absorbance spectra were transformed using the Kubelka-Munk function [10,64,65] to produce a signal, normalized for comparison between samples, and so to calculated the band gaps (Eg,direct and Eg,indirect). The details of this treatment method have been widely described elsewhere [53,54,66].…”

Generating oxygen vacancies in Cu 2+ ‐doped TiO 2 hollow spheres for enhanced photocatalytic activity and antimicrobial activity

“…Recently, in order to make TiO 2 better use of the solar spectrum, several approaches, such us precious metal deposition, non-metallic or metallic elements doping, and semiconductor coupling, have been developed to deal with the insufficient of TiO 2 material [13][14][15][16][17]. Among them, element doping with metals and non-metals is considered as the simplest and inexpensive way.…”

“…Among them, element doping with metals and non-metals is considered as the simplest and inexpensive way. For example, Julien G. Mahy et al [16] investigated the degradation activity of N-doped TiO 2 catalysts on p-nitrophenol, and the results showed that N-doped catalysts had a significantly improved degradation capability under visible light. Shafei and Sheibani [18] reported the preparation of Cu-doped TiO 2 -CNT nanocomposite powder and found that the catalyst exhibited great efficiency in the degradation rate of methylene blue under visible-light irradiation.…”