Sulfur-Doped TiO2: Structure and Surface Properties

Abstract

A comprehensive study on the sulfur doping of TiO 2 , by means of H 2 S treatment at 673 K, has been performed in order to highlight the role of sulfur in affecting the properties of the system, as compared to the native TiO 2 . The focus of this study is to find a relationship among the surface, structure, and morphology properties, by means of a detailed chemical and physical characterization of the samples. In particular, transmission electron microscopy images provide a simple tool to have a direct and immediate evidence of the effects of H 2 S action on the TiO 2 particles structure and surface defects. Furthermore, from spectroscopy analyses, the peculiar surface, optical properties, and methylene blue photodegradation test of S-doped TiO 2 samples, as compared to pure TiO 2 , have been investigated and explained by the effects caused by the exchange of S species with O species and by the surface defects induced by the strong H 2 S treatment.

Few-Layer MoS2 Nanodomains Decorating TiO2 Nanoparticles: A Case Study for the Photodegradation of Carbamazepine

“…Concerning the spectrum of pure TiO 2 in the 750–350-cm −1 range (Figure 2, black curve), the bands at 144 cm −1 , 396 cm −1 , 514 cm −1 and 636 cm −1 are assigned, respectively, to the typical E g , B 1g , A 1g and E g Raman active modes, respectively, of the anatase phase, as well described in literature, while the shoulder at 608 cm −1 and the very small peak at 444 cm −1 (highlighted by asterisks) are ascribed to the A 1g and E g modes of the rutile phase [8,25,27]. …”

“…From the comparison of the spectra of TiO 2 before and after the sulfidation treatment (black and blue curves, respectively), a clear band gap shift of the sulfided TiO 2 sample, well shown by a Tauc plot in [25], together with an additional broad absorption in the 390–600-nm range are detectable. As well described in the literature [47] and in our previous work [25], these phenomena can be ascribed to a change in TiO 2 electronic structure.…”

“…From the comparison of the spectra of TiO 2 before and after the sulfidation treatment (black and blue curves, respectively), a clear band gap shift of the sulfided TiO 2 sample, well shown by a Tauc plot in [25], together with an additional broad absorption in the 390–600-nm range are detectable. As well described in the literature [47] and in our previous work [25], these phenomena can be ascribed to a change in TiO 2 electronic structure. In fact, the mixing of 3p atomic orbitals of S species, due to a S → O exchange at the surface of TiO 2 during the sulfidation step, as well discussed in the following paragraphs, leads to the formation, above the valence band, of new electronic states [3,25,47].…”

“…Different from other heteroatomic counterparts, sulfur is for a fact isoelectronic to oxygen and can replace it without altering the electroneutrality of the solid [3]. It has been proven that the treatment of a TiO 2 surface under H 2 S atmosphere can induce a modification of the titania electronic structure, causing a red shift of its absorption edge [25]. Some articles [26,27,28] suggest that MoS 2 /TiO 2 composites are good photocatalysts, thanks to the efficient charge-carrier separation [29].…”

Preparation, Physicochemical Properties, and Long-Term Performance of Photocatalytic Ceramsite Sand in Cementitious Materials

“…It can be seen that the main components of CS were SiO2 and Mg0.7Fe0.23Al1.97O4. Comparing with the XRD pattern of TiO2, the characteristic peaks of 1PCS-1.25~2.35-UA occurred at about 2θ = 27° and 44.3° can be assigned to the Rutile [23]. The characteristic peaks at 2θ = 25.3° can be assigned to the Anatase.…”