Hybrid TiO2–Polyaniline Photocatalysts and their Application in Building Gypsum Plasters

Abstract

Hybrid materials of conjugated polymer and titanium(IV) oxide have attracted considerable attention concerning their potential benefits, including (i) efficient exploitation of visible light, (ii) a high adsorption capacity for organic contaminants, (iii) and effective charge carriers separation. The new class of the photocatalysts is promising for the removal of environmental pollutants in both aqueous and gaseous phases. For the first time, in this study, the polyaniline (PANI)–TiO2 hybrid composite was used for the degradation of phenol in water and toluene in the gas phase. Polyaniline–TiO2 was prepared by the in situ polymerization of aniline on the TiO2 surface. The obtained hybrid material was characterized by diffuse reflectance spectroscopy (DR/UV-Vis), X-ray diffraction (XRD), fast-Fourier transformation spectroscopy (FTIR), photoluminescence (PL) spectroscopy, microscopy analysis (SEM/TEM), and thermogravimetric analysis (TGA). An insight into the mechanism was shown based on the photodegradation analysis of charge carrier scavengers. Polyaniline is an efficient TiO2 photosensitizer for photodegradation in visible light (λ > 420 nm). The trapping experiments revealed that mainly h+ and ˙OH were the reactive oxygen species that were responsible for phenol degradation. Furthermore, the PANI–TiO2 hybrid nanocomposite was used in gypsum plaster to study the self-cleaning properties of the obtained building material. The effect of PANI–TiO2 content on the hydrophilic/hydrophobic properties and crystallographic structure of gypsum was studied. The obtained PANI–TiO2-modified gypsum plaster had improved photocatalytic activity in the reaction of toluene degradation under Vis light.

An Aqueous Exfoliation of WO3 as a Route for Counterions Fabrication—Improved Photocatalytic and Capacitive Properties of Polyaniline/WO3Composite

“…Thus, it is very likely that the degradation of MB was strictly related to direct photooxidation of dye adsorbed on the photocatalyst via holes from the valence band. PANI/Cl was not able to decompose MB directly using holes due to the location of the valence band [48]. It can be concluded, that the presence of n-type WO 3 facilitated the degradation of the organic dye via direct oxidation using holes from the valence band of WO 3 .…”

“…The energy band alignment enables the transfer of the photogenerated electrons. According to previous reports about PANI photocatalytic properties, holes rather do not participate in the direct oxidation of organic pollutants adsorbed on the photocatalyst, however, the photoexcitation may lead to the formation of hydroxyl radicals [48]. In the case of WO 3 , holes from the valence band are mostly consumed for direct oxidation of the adsorbed dye.…”

Surface modifications of TiO2 nanostructured materials induced by 120 MeV Ag ions

“…43 The peak at 449 nm (2.76 eV) results from the trap levels caused by O 2 vacancies. 44 As the process of photoluminescence is a surface phenomenon, a change in the surface environment induced by irradiation has a significant effect on it. One of the effects of irradiation in the present study is the suppression of the PL intensity of TiO 2 nanoparticles with increasing 120 MeV Ag ion fluence (Figure 7).…”

Preparation and Characterization of Defective TiO2. The Effect of the Reaction Environment on Titanium Vacancies Formation

“…Furthermore, for the TBT-TiO 2 sample, a slight increase in photoactivity was noted after adding to the system scavenger of holes or hydroxyl radicals. It could result from the additional in-situ formation of the reactive species on the photocatalysts' surface [36]. Based on the study, a schematic mechanism of phenol degradation in the presence of defective TiO 2 (sample TBT-HIO 3 ) was proposed and illustrated in Figure 6.…”