Chelated Nitrogen-Sulphur-Codoped TiO₂: Synthesis, Characterization, Mechanistic, and UV/Visible Photocatalytic Studies

Abstract

This study presents in detail the physicochemical, photoluminescent, and photocatalytic properties of carboxylic acid chelated nitrogen-sulphur-codoped TiO 2 . From the Fourier transform infrared spectroscopic study, it was revealed that the formate group formed bidentate bridging linkage while the acetate group coordinated in a bidentate chelating mode with a titanium precursor. In compliance with X-ray diffraction data, the anatase to rutile transformation temperature was extended due to carboxylic acid chelation and NS codoping. Raman analysis indicated four Raman peaks at 146, 392, 512, and 632 cm −1 for the precalcined chelated TiO 2 ; on incorporation with NS dopants, an increase in Raman intensity for these peaks was recorded, indicating the structure stability of the anatase phase. Furthermore, X-ray photoelectron spectroscopic study revealed the presence of anionic doping of nitrogen and cationic doping of sulphur in the lattice of TiO 2 . When evaluating the UV-visible photodegradation rate of 4-chlorophenol, the modified TiO 2 (NS 0.06 -TFA) showed the highest photocatalytic activity. In connection with the activity tests, several scavenger agents were employed to elucidate the significance of the different reactive oxidizing species during the photocatalytic process. Moreover, the transfer pathways of photogenerated carriers and the photocatalytic reaction mechanism of modified TiO 2 were also explained in detail.

Conscientious Design of Zn-S/Ti-N Layer by Transformation of ZnTiO3 on Electrospun ZnTiO3@TiO2 Nanofibers: Stability and Reusable Photocatalytic Performance under Visible Irradiation

“…The production rate of the ROS and effective separation of charge carriers determined the catalytic performance of the NF. On the surface, sulfur and nitrogen based defect level density favors the carrier separation rate by standing in as photogenerated hole trappers, 42 which leads to improvised carrier response for effective catalytic performance under UV and visible irradiation. Trends of the exhibited catalytic performance under UV and visible irradiation were similar.…”

Enhancement of TiO2 activity under visible light by N,S codoping for Pb(II) removal from water

“…Among the existing semiconductor materials, titanium dioxide (TiO 2 ) is a very active, low cost, and nontoxic photocatalyst. TiO 2 with a wide gap assigned by Eg 3.20 eV can only be activated under UV light [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16], and consequently, it is less active under visible light exposure. This deficiency restricts the application of TiO 2 photocatalyst under low cost sunlight, which is mostly composed of visible light [2,8,11].…”

“…This deficiency restricts the application of TiO 2 photocatalyst under low cost sunlight, which is mostly composed of visible light [2,8,11]. The enhancement of TiO 2 activity under visible light by mono-doping [2-6, 9, 10] and co-doping [7,8,[11][12][13][14][15][16] has been proven to be the most successful strategy. By doping process, the gap can be narrowed and thus decreasing the Eg of TiO 2 [2-8, 10, 11, 13-15], emerging in the visible radiation.…”

“…Thereby, the visible response and the activity of organic pollutant degradation of the doped TiO 2 under visible light exposure are considerably enhanced [2,3,5,[9][10][11]13]. Besides, the improvement of the photodegradation of various organic pollutants underdoped TiO 2 is also contributed by the ability of the dopant in suppressing the recombination of electrons (e -) and holes (h + ) photogenerated by TiO 2 during UV irradiation [5,9,15], as presented as Eqs. ( 1) and (2).…”

“…Compared to metal elemental dopants, the non-metals are more interesting due to their smaller size allowing them to be inserted into the TiO 2 crystal lattice facilely [2,4,[9][10][11]. Furthermore, among the non-metal dopants, nitrogen has attracted extensive interest as it can be easily introduced into the TiO 2 structure, due to its atomic size, which is comparable with that of oxygen, its low ionization energy, and high stability [2][3][4]15]. In accordance, N-doped TiO 2 demonstrates significant photocatalytic activity under visible light irradiation [2][3][4].…”