For the removal of pollutants, a modified TiO₂ photocatalyst is attracting attention. Fe-doped TiO₂ nanofibers were prepared through a combination of electrospinning and calcination. Morphological characterization of the sample was conducted using field-emission scanning electron and transmission electron microscopy. The crystal structure of each sample was analyzed using high-resolution transmission electron microscopy, selected area electron diffraction, and Fast Fourier Transform imaging. The average diameter of the Fe-doped TiO₂ nanofibers was measured to be 161.5 nm and that of the pure TiO₂ nanofibers was 181.5 nm. The crystal phase when heat treated at 350 °C was anatase for TiO₂ nanofibers and rutile for Fe-doped TiO₂ nanofibers. The crystal phase of the TiO₂ matrix was easily transitioned to rutile by Fe-doping. The photocatalytic performance of each sample was compared via the photodegradation of methylene blue and acid orange 7 under ultraviolet and visible light irradiation. In the Fe-doped TiO₂ nanofibers, photodegradation rates of 38.3% and 27.9% were measured under UV irradiation and visible light, respectively. Although other catalysts were not activated, the photodegradation rate in the Fe-doped TiO₂ nanofibers was 9.6% using acid orange 7 and visible light. For improved photocatalytic activity, it is necessary to study the concentration control of the Fe dopant.

Titanium dioxide (TiO₂) is a widely studied material with many attractive properties such as its photocatalytic features. However, its commercial use is limited due to issues such as deactivation in the visible spectrum caused by its wide bandgap and the short lifetime of photo-excited charge carriers. To overcome these challenges, various modifications could be considered. In this study, we investigated copper doping and electron beam treatment. As-spun TiO₂ nanofibers were fabricated by electrospinning a TiO₂ sol, which obtained viscosity through a polyvinylpyrrolidone (PVP) matrix. Cu-doped TiO₂ nanofibers with varying dopant concentrations were synthesized by adding copper salts. Then, the as-spun nanofibers were calcined for crystallization. To evaluate photocatalytic performance, a photodegradation test of methylene blue aqueous solution was performed for 6 h. Methylene blue concentration was measured over time using UV-Vis spectroscopy. The results showed that Cu doping at an appropriate concentration and electron-beam irradiation showed improved photocatalytic efficiency compared to bare TiO₂ nanofibers. When the molar ratio of Cu/Ti was 0.05%, photodegradation rate was highest, which was 10.39% higher than that of bare TiO₂. As a result of additional electron-beam treatment of this sample, photocatalytic efficiency improved up to 8.93% compared to samples without electron-beam treatment.

The superior chemical and electrical properties of TiO₂ are considered to be suitable material for various applications, such as photoelectrodes, photocatalysts, and semiconductor gas sensors; however, it is difficult to commercialize the applications due to their low photoelectric conversion efficiency. Various solutions have been suggested and among them, the increase of active sites through surface modification is one of the most studied methods. A porous nanostructure with a large specific surface area is an attractive solution to increasing active sites, and in the electrospinning process, mesoporous nanofibers can be obtained by controlling the composition of the precursor solution. This study successfully carried out surface modification of TiO₂ nanofibers by mixing polyvinylpyrrolidone with different molecular weights and using diisopropyl azodicarboxylate (DIPA). The morphology and crystallographic properties of the TiO₂ samples were analyzed using a field emission electron microscope and X-ray diffraction method. The specific surface area and pore properties of the nanofiber samples were compared using the Brunauer-Emmett-Teller method. The TiO₂ nanofibers fabricated by the precursor with K-30 polyvinyl pyrrolidone and diisopropyl azodicarboxylate were more porous than the TiO₂ nanofibers without them. The modified nanofibers with K-30 and DIPA had a photocatalytic efficiency of 150% compared to TiO₂ nanofibers. Their X-ray diffraction patterns revealed anatase peaks. The average crystallite size of the modified nanofibers was calculated to be 6.27–9.27 nm, and the specific surface area was 23.5–27.4 m²/g, which was more than 150% larger than the 17.2 m²/g of ordinary TiO₂ nanofibers.