Papers by Keyword: Titanium Dioxide Nanotubes

Abstract: This article focused on investigating the influence of current density on the morphology and structure of silver nanoparticles (n-Ag) electrodeposited on anodized titanium substrates (denoted as TiO₂/Ti) on the surface. The TiO₂/Ti substrate served as the cathodic electrode placed in an electrolyte solution containing ionic [Ag(NH₃)₂]⁺ complex solution. The n-Ag/TiO₂/Ti samples were synthesized at current densities ranging from 0.2 A/dm² to 0.5 A/dm² for 20 seconds at room temperature. The study performed morphological and surface composition analysis of n-Ag/TiO₂/Ti using Field Emission Scanning Electron Microscopy (FESEM) and X-ray Diffraction (XRD) techniques. Additionally, the study assessed the electrochemical properties using the AutoLab system with Nova 2.1 software, based on Tafel curve measurements to compare the corrosion resistance of the samples before and after modification.

Abstract: Photoelectrocatalysis has emerged as a promising technology to degrade recalcitrant pollutants such as textile dyes in wastewater completely. Titanium dioxide is typically used as a photocatalyst, but its wide bandgap constrains its use to the use of ultraviolet light. To extend its use to the visible-light region, we doped titanium dioxide nanotubes with iron and sulfur. We used them as a photoelectrode for the photoelectrocatalytic degradation of a model pollutant – phenol red. Response surface methodology using a Box-Behnken design of experiments was used to investigate the effects of initial dye concentration, applied potential, and dopant loading on phenol red degradation kinetics. Statistical analysis showed that our reduced cubic model adequately correlates these parameters. The fastest dye degradation rate was achieved at the optimized conditions: initial phenol red concentration = 5.0326 mg L^-1, applied voltage = 29.9686 V, and dopant loading = 1.2244 wt.%. Complete degradation of phenol red may be achieved after 11.77 hours of treatment under the optimized conditions in a batch reactor. Our model's robustness enables it to be used for process modeling and a basis for designing scaled-up photoelectrocatalytic reactors.

Abstract: Photoelectrocatalysis is a rapidly developing technology for degrading recalcitrant organic compounds in wastewater due to its ability to overcome electron-hole recombination. Herein, we synthesized Fe/S co-doped TiO₂ nanotubes through an in-situ anodization technique. We developed a simple reduced quadratic model based on response surface modeling which can be used to adequately correlate the operating parameters with the photoelectrocatalytic performance of Fe/S-TiNTs in degrading phenol red. Predicted maximum dye degradation of 54.78% was achieved by the generated model using the optimized parameters: initial phenol red concentration = 5.22 mg L^-1, applied voltage = 27.4 V, and dopant loading = 2.97 wt.%. Upon validation, experimental maximum phenol degradation of 53.24% was obtained, which agrees well with the predicted value within statistical significance. Overall, our model can be potentially used for process optimization within the design space studied.

Abstract: Titanium dioxide is a widely-investigated semiconductor photocatalyst due to its wide availability and low cost. Although it has been successfully used in the photocatalytic treatment of various organics in wastewater, it remains a challenge to modify its structure to achieve enhanced catalytic properties at a wider light spectrum. Doping with transition metals was seen to narrow its optical band gap yet synthesis routes have been largely limited to the use of high-end equipment. Herein we demonstrate the use of a simpler one-pot approach to synthesize nanoporous arrays of silver-doped titanium dioxide nanotubes (Ag-TiNTs) by double anodization of titanium sheets. The synthesized Ag-TiNTs have an average inner diameter of 58.68 nm and a wall thickness of 16.46 nm. ATR-FTIR spectroscopy revealed its characteristic peaks attributed to O-Ti-O bonds. Silver doping increased the lattice volume and crystallite size of anatase with a corresponding decrease in the degree of crystallinity due to the introduction of impurity Ag atoms in its tetragonal structure. Silver was homogeneously distributed across the nanotube surface at an average loading of 1.41 at. %. The synthesized Ag-TiNTs were shown to have a superior photoelectrocatalytic activity in degrading C.I. Basic Blue 9 under UV illumination with a pseudo-first-order kinetic rate of 1.0253 x 10^-2 min^-1. Most importantly, the Ag-TiNTs are photoelectrocatalytically-active even at a low Ag loading.

Abstract: Titanium dioxide (TiO₂) nanotubes with a highly ordered structure were grown by a self-organized anodization process. The photodeposition process was used to improve the visible light response of titanium dioxide (TiO₂) nanotubes. The irradiation was carried out with 500 W halogen lamp for 1, 5, 15, 30 and 60 min in the mixed ethanol solution of antimony trisulfide (Sb₂S₃). The obtained samples were annealed at 250 °C for 30 min. The morphology of the fabricated sample was characterized by a field emission scanning electron microscope (FE-SEM). The phase of samples was determined by X- ray diffractometer (XRD). The weight percentages of a component in the sample were measured by X-ray fluorescence spectrometry (XRF). UV-Vis diffuse reflectance spectra (DRS) of the samples were recorded. All titanium dioxide (TiO₂) nanotube samples prepared by anodization process were anatase phase. All composite titanium dioxide (TiO₂) nanotube /Sb₂S₃ samples were a crystalline phase. The percentage of Sb and S increase with increasing of photodeposition’s time. The increasing photodeposition of antimony trisulfide (Sb₂S₃) on titanium (TiO₂) nanotubes from 1 to 60 min lead to increasing of photoabsorption property of the material in the visible region.

Abstract: In TiO₂ nanoparticle based dye sensitized solar cells (DSSC), the electron injected from the dye has to cross multiple interparticle boundaries in random directions before reaching the electrode. For application in DSSCs, the directional pathway for electron transport through the nanotubes is known to reduce the recombination rate. In the present study, titania nanotubes with nanograss layer have been fabricated by anodization of titanium foil in fluoride containing organic electrolyte. Dye sensitized solar cells with photoanode made of titania nanotubes covered with nanograsswas found to have a higher efficiency than ones made with only titania nanotubes of the same length.This can be attributed to enhanced dye adsorption on nanotubes with nanograss. The efficiency of DSSC using titania nanotubes is also affected by the annealing conditions such as duration, temperature.

Abstract: γ-Fe₂O₃/N-doped TiO₂ nanotubes (N-TiO₂ NTs) photocatalyst was successfully prepared by a wet chemical method. Visible light responses of this novel catalyst for decomposing methyl orange (MO) in air were also evaluated. It was found that the photocatalytic activity of γ-Fe₂O₃/N-TiO₂ NTs was higher than those of N-doped TiO₂ NTs, TiO₂ NTs and P25. The characterizations including TEM, EDX and UV/Vis DRS revealed that iron oxide nanoparticles were decorated in/around N-TiO₂ NTs and the spectral response was enhanced in visible region. Meanwhile, the catalyst recycled by external magnetic field showed that its photocatalytic efficiency did not decrease obviously.