Undoped and Fe-Doped Anatase/Brookite TiO2 Mixed Phases, Obtained by a Simple Template-Free Synthesis Method: Physico-Chemical Characterization and Photocatalytic Activity towards Simazine Degradation

Abstract

For the first time, Fe-doping (0.05, 1.0, and 2.5 wt.% Fe) was performed on a high-surface-area anatase/brookite TiO2 by adopting a simple template-free sol-gel synthesis followed by calcination at a mild temperature. The powders’ textural and surface properties were characterized by following a multi-technique approach. XRD analysis showed that the anatase/brookite ratio slightly varied in the Fe-doped TiO2 (from 76.9/23.1 to 79.3/22.7); Fe doping noticeably affected the cell volume of the brookite phase, which decreased, likely due to Fe3+ ions occupying interstitial positions, and retarded the crystallite growth. N2 sorption at −196 °C showed the occurrence of samples with disordered interparticle mesopores, with an increase in the specific surface area from 236 m2 g−1 (undoped TiO2) to 263 m2 g−1 (2.5 wt.% Fe). Diffuse Reflectance UV-Vis spectroscopy showed a progressive decrease in the bandgap energy from 3.10 eV (undoped TiO2) to 2.85 eV (2.5 wt.% Fe). XPS analysis showed the presence of some surface Fe species only at 2.5 wt.% Fe, and accordingly, the ζ-potential measurements showed small changes in the pH at the isoelectric point. The photocatalytic degradation of simazine (a persistent water contaminant) both under UV and simulated solar light was performed as a probe reaction. Under UV light, Fe-doping improved simazine degradation in the sample at 0.05 wt.% Fe, capable of degrading ca. 77% simazine. Interestingly, the undoped TiO2 was also active both under UV and 1 SUN. This is likely due to the occurrence of anatase/brookite heterojunctions, which help stabilize the photogenerated electrons/holes.

Mesoporous TiO2 and Fe-containing TiO2 prepared by solution combustion synthesis as catalysts for the photodegradation of paracetamol

“…By comparing the samples obtained through the SCS method, the TiO 2 _SCS450 sample extended its absorption towards longer wavelengths, above 400 nm. This region could be associated with the Urbach tail, which is namely an exponential part in the energy spectrum of the absorption coefficient that may appear near the optical band edge in amorphous, disordered, and crystalline materials (Gervasi et al 2023 ). This region could be related to the presence of disorder and physisorbed water (see OH species concentration from XPS results), or was due to the higher temperature adopted during the synthesis procedure, since it was demonstrated that this parameter affects the Urbach tail (Aljishi et al 1990 ; Yap et al 2020 ).…”

“…To enhance the catalytic properties of this oxide toward paracetamol, many studies report the possibility of introducing different heteroatoms, mainly iron (Cifci et al 2017 ; Yap et al 2020 ; de Moura et al 2021 ). This element is earth-abundant and non-toxic (Gervasi et al 2023 ) and its effect is crucial since it can be determinant for an efficient degradation (Trovó et al 2012 ). Indeed, it is well known that the presence of iron, in particular Fe 2+ , and the synergy with H 2 O 2 can enhance the mineralization of the paracetamol, mostly through the (Photo)Fenton process, which is another method belonging to AOPs.…”

Phase Transformation Strategies for the Construction of Heterojunction TiO2 Photocatalysts

“…Nowadays, there are numerous approaches that can be used to control the phase composition of TiO 2 , including typical heat treatment, [66–68] heteroatom doping, [69–71] MOF induction, [72–74] etc. In addition, the phase transformation of TiO 2 is also affected by the reaction conditions such as pH value, reactant ratio and solvent type [75–84] …”

N-Doped TiO2-Nb2O5 Sol–Gel Catalysts: Synthesis, Characterization, Adsorption Capacity, Photocatalytic and Antioxidant Activity

“…The solution was magnetically stirred, the reaction temperature was kept around 20 • C, and atmospheric air was continuously bubbled inside the reactor. The solution pH was adjusted to pH = 3, 5, or 7, using HCl and NaOH solutions, and the catalyst concentration in all tests was equal to 1.0 g L −1 , similar to that reported in other works [77][78][79]. In each experiment, the catalyst used and the pH value of the solution were determined according to the experimental design (see Section 2.4).…”