Papers by Keyword: Anatase TiO₂

Abstract: Nanocrystal TiO₂ has been synthesized from TiCl₃ as a precursor using the co-precipitation method. Synthesis parameters are chosen to produce the anatase phase of TiO₂ nanomaterials. Polymer-TiO₂ composite was made from a mixture of TiO₂ nanomaterials and poly(vinyl alcohol) (PVA) and ethyl cellulose polymer materials. PVA solvents were used by water (H₂O) while for ethyl cellulose used terpineol solvents. Composite fiber was made using electrospinning method with sedimentation parameters: between the syringe and Al foil collector applied the voltage at 10 kV, between the needle tip and the collector, the distance was 10 cm, the syringe pump was set at a constant flow rate of 1 ml/h, the collector rotation speed was 100 rpm , and humidity inside electrospinning machine was 40%. Samples were characterized using scanning electron microscopy (SEM) and x-ray diffraction (XRD). XRD results showed TiO₂ crystal diffraction peaks when the composition of TiO₂ was quite large, whereas for only a small TiO₂ composition, the diffraction peaks did not appear and were only dominated by amorphous PVA. Deposition results showed that composite fibers have been formed for PVA polymers whereas fiber ethyl cellulose was not formed.

Abstract: Vertically aligned anatase TiO2 nanotubes (NTs) were fabricated by anodization of a pureTi foil in ethylene glycol solutions containing different concentrations of deionized (DI) water. Themorphology, elemental composition, and crystallization of TiO2 nanostructures were analyzed byfield emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), Ramanspectroscopy, and X-ray spectroscopy (XPS), respectively. The diameter and length of TiO2 NTswere controlled by varying concentrations of DI water. Furthermore, we found that TiO2 NTs in DIwater 12 wt. % was suitable for further applications in UV photodetector due to it has a high volumeto surface area ratio and long tube. TiO2 NTs have a high potential in various applications such as UVphotodetectors, gas sensor, dye sensitized solar cells, and photocatalysts.

Abstract: The vertically aligned TiO₂ Nanotubes (TiNTs) extracts electrons from an absorber and also helps in its transport in perovskite and dye sensitized solar cells (DSSCs) solar cells. Thus electron transporting layer plays a very important role in photon to electron conversion. Electrochemical anodization is been used widely to grow TiNTs for solar cell applications; due to its low cost, flexibility to vary pore diameter and tube length. We observed that, TiNTs maintained its tubular array only for a set time period. On increasing the growth time they begin to take the form of nanocrystals with {001} facets. Formation of these titanium nanocrystals (TiNcs) was clearly observed through field emission scanning electron microscope (FESEM) and Transmission electron microscopy (TEM). Thus TiO₂ nanostructures can be tuned by varying anodization time. More importantly, optimization of the reaction process led to the growth of more orderly, crystalline anatase TiNTs/TiNcs over Ti metal foil substrate. The crystal structure and surface morphology of the prepared thin film samples were studied using X-ray diffraction (XRD) technique and scanning and transmission electron microscopes (TEM). XRD confirmed the anatase phase of as grown TiO₂ with (101) as major intensity preferred orientation. Lattice parameters calculated were found to be a= 3.77-to-3.82 and c= 9.42-to-9.58 for grown TiO₂.

Abstract: Anatase TiO₂ nanotubes (ATNT) was synthesised by hydrothermal method using anatase TiO₂ nanoparticles (AT) as precursor and calcined at two different temperatures (250 & 450 °C) for 2 h. The AT and synthesized ATNT photocatalysts were characterized by X-ray diffraction, transmission electron microscopy, N₂ adsorption-desorption measurements, UV-vis diffuse reflectance and Fourier Transform Infra-red spectroscopy techniques for their structural, textural and electronic properties. The photocatalytic degradation of Indigo carmine (IC) dye aqueous solution has carried out using ATNT-250 and ATNT-450 photocatalysts under UVLED irradiation. The kinetic analysis has also revealed that the degradation of IC dye solution follows first order kinetic model. The overall study demonstrates the appropriate band gap of the photocatalysts used and the suitable irradiation source which could accelerate the rate of photocatalytic degradation. The band gap of the synthesised ATNT is not much affected due to the change in morphology from nanoparticle to nanotube. The results demonstrated that the irradiation of UV-LED could be utilised for the degradation of organic dyes

Abstract: Cu-modified graphitic ordered mesoporous carbon supported TiO₂ catalyst was synthesized based on a hard template method. X-ray diffraction, nitrogen adsorption-desorption, scanning electron microscopy and transmission electron microscopy analysis techinques were used to characterize the sample. It was observed that copper and anatase TiO₂ nanoparticles were well dispersed in the Cu-modified mesoporous graphitic carbon, and the resulting composite with ordered mesostructure and high specific surface area exhibited an exceptionally high activity in the photocatalytic reduction of CO₂ with H₂O under simulated solar irradiation.

Abstract: The crystal structures, band structures, density of states, charge density, overlap population and optical properties of pure anatase TiO2 and Pr-doped anatase TiO2 were studied by using the plane-wave pseudopotential method based on the first-principles. After Pr doping, the valence band and the conduction band moved down and became dense, energy gap became narrow and a impurity band which consists of Pr 4f states appeared. And the dipole moment got improved, which is good for the separate of the electron-hole pairs. These effectively overcome two huge shortcomings of TiO2. Besides, Pr-doped anatase TiO2 produced more carriers which have good transport properties and the absorption spectra of Pr-O bond appear in the region that the wavelength is longer. The calculation results of optical properties show that the absorption edge occured red shift, which means the photocatalytic activity of anatase TiO2 got remarkable improved during visible-light region. This conforms to the previous analysis. So the photocatalytic activity of anatase TiO2 got remarkable improved after Pr doping.

Abstract: Anatase nanocrystalline TiO₂ is of specific interest for many applications such as Dye sensitized solar cells (DSSCs), lithium ion batteries, sensors and photocatalysis. In the present work, we have studied the electrochemical properties of TiO₂ nanoparticles using Impedance Spectroscopy (IS) to evaluate bulk and grain boundary effects which affects the transport properties of DSSCs. We also report and discuss here the results of XRD and TEM of this compound.

Abstract: Photocatalytic hydrogen generation holds promise as the future source of environmentally friendly and economically feasible energy source. In order to conduct more efficient photocatalytic reaction, anatase TiO₂ doped with transition metals is proposed as catalyst. Investigation was conducted by using density functional theory (DFT) augmented with Hubbard U treatment to correct the band gap of TiO₂. Emergence of new states inside the band gap of doped anatase TiO₂ can lead to a material with a better photocatalytic property, i.e., able to work at visible light than that of pristine TiO₂ which is sensitive to UV light only. The investigated materials comply with standard hydrogen electrode (SHE), thus can be used as photocatalyst in water splitting reaction. Out of the two options tested, TiO₂ doped with Fe produces a material with the better photocatalytic properties.Keywords: DFT + U, anatase TiO₂, photocatalytic, water splitting, band gap

Abstract: Different concentrations of Ni-doped anatase TiO₂ nanoparticles were prepared by ice-bath co-precipitation method to examine the effects of various Ni²⁺ concentrations on the power exchange mechanism in photovoltaic performances of dye-sensitized solar cells (DSSC). X-ray powder diffraction (XRD) revealed a single anatase phase present in all samples together with three times reduction of particle size with the addition of Ni²⁺. Nanoparticle size exhibited better uniformity under scanning electron microscopy (SEM) with an increase of Ni²⁺ ions. Fourier Transform Infrared Spectroscopy (FTIR) confirmed the formation of Ti-O-Ni bonding due to sharpened and enhanced intensity of the bands in the range of 500-1000 cm^-1 and 910-1030 cm^-1. Ni²⁺ concentrations also increased both open-circuit voltage (Voc) and short-circuit current (I_sc). The optimum concentration of Ni-doping obtained was at 0.075M of Ni which shows a maximum DSSC efficiency of 0.38%.

Abstract: Anatase TiO₂ enrichment from Bangka ilmenite (FeTiO₃) has been conducted. First, ilmenite was mechanically activated using a planetary ballmill to obtain sub-micron sized particle followd by magnetic separation. Chemical treatment, dissolution of iron using hydrochloric solution, was performed to obtain titania rich residue. EDX data shows that the iron content was reduced in the titania residue. Ammonium hydroxide (NH₄OH) solution was added to the washed precipitate, before adding H₂O₂ solution (10%) that acted as a coordination agent to leach titanium from the the residue in the form of ammonium peroxo titanate solution. The peroxo titanate powder was obtained by evaporating the ammonium peroxo titanate solution. XRD data show that TiO₂ anatase was formed after peroxo titanate powder was calcined at the temperature of 600°C. EDX data also shows that the obtained anatase TiO₂ still has impurities, such as silicon (0.98%) and iron (2.75%). Its photocatalytic activity was studied on photodegradation of Congo Red and compared with the photocatalytic activity of commercial TiO₂, Degussa P-25. The photoreactivity test on degradation of Congo Red solution with the as-prepared Anatase gave 20% degradation which is still inferior compared to the results given by Degussa P25 (92%). This indicates that the impurities in as-prepared Anatase may cover the titania surface hindering the contact between Congo Red as well as UV-light and the active titania species.