RESUMEN
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.
RESUMEN
Electrospun NiZn ferrite nanofibers have great potential due to their one-dimensional structure and electrical properties, but they have a low reproducibility resulting from many process confounders, so much research effort is needed to achieve optimized process control. For structure control, the viscosity of the precursor solution is a likely parameter. One solution is to use polyvinyl pyrrolidone (PVP) and metal nitrate to obtain the desired viscosity by increasing the nitrate content, even if the polymer content is decreased. Ni0.5Zn0.5Fe2O4 ferrite nanofiber was electrospun with various precursor conditions. Fifteen different precursor solutions, with a content of five polymers and three metal nitrates, were prepared, with precursor solutions composed of Fe(NO3)2·9H2O, Ni(NO3)2·6H2O, Zn(NO3)2·6H2O, polyvinyl pyrrolidone (PVP), and N,N-dimethylmethanamide. The fiber diameter changed from the lowest, of 62.41 nm, to 417.54 nm. This study shows that the average diameter can be controlled using the metal nitrate concentration without a difference in crystal structure when PVP is used. In a 24.0 mmol metal nitrate precursor solution, the process yield was improved to 140% after heat treatment. There was also no significant difference in the crystal structure and morphology. This system reduces the cost of raw materials for electrospinning and increases the process yield of NiZn ferrite nanofibers.
RESUMEN
TiO2 is a significant n-type semiconducting material because of its superior electric and photocatalytic properties. Although this material has been extensively studied as a semiconductor electrode for dye-sensitized solar cells for its inherent bandgap and its excellent electrical and chemical properties, the photoelectric efficiency is nevertheless lower than that of the Si-based solar cells, which is generally reported as 13-27%. On the other hand, various carbon structures have been studied to increase the overall charge transport efficiency by reducing the charge transport resistance in the cell while having high electric conductivity. These results are expected to improve the photoelectric conversion efficiency when applied to dye-sensitized solar cells. We fabricated a TiO2/multi-wall carbon nanotube (MWCNT) core-shell structure by a hydrothermal method. The TiO2 anatase phase in the TiO2/MWCNT core-shell structure was confirmed by X-ray diffraction (XRD). The core-shell nanostructure with a diameter of 127 nm to 211 nm was observed by field emission scanning electron microscope (FE-SEM). The morphology of the TiO2/MWCNT core-shell nanocomposite was also analyzed by transmission electron microscope (TEM). The Fourier-Transform Infrared Spectrometer (FT-IR) and Brunauer Emmett and Teller (BET) method were used to observe the chemical bonding and specific surface area of the TiO2/MWCNT core-shell nanocomposite, respectively. The TiO2/MWCNT core-shell composites had a larger specific surface area of 92.00 m²/g, a larger pore volume of 0.33 cm³/g, and a larger pore size of 65.21 nm than commercial TiO2 nanoparticles (P25). The TiO2/MWCNT core-shell structure may provide a high-speed path for photoelectrons to pass quickly and will be useful for various applications, such as solar cells and photocatalysts.