Synthesis of Mesoporous TiO2-B Nanobelts with Highly Crystalized Walls toward Efficient H2 Evolution

Synthesis of TiO2-(B) Nanobelts for Acetone Sensing

Titanium dioxide nanobelts were prepared via the alkali-hydrothermal method for application in chemical gas sensing. The formation process of TiO2-(B) nanobelts and their sensing properties were investigated in detail. FE-SEM was used to study the surface of the obtained structures. The TEM and XRD analyses show that the prepared TiO2 nanobelts are in the monoclinic phase. Furthermore, TEM shows the formation of porous-like morphology due to crystal defects in the TiO2-(B) nanobelts. The gas-sensing performance of the structure toward various concentrations of hydrogen, ethanol, acetone, nitrogen dioxide, and methane gases was studied at a temperature range between 100 and 500 °C. The fabricated sensor shows a high response toward acetone at a relatively low working temperature (150 °C), which is important for the development of low-power-consumption functional devices. Moreover, the obtained results indicate that monoclinic TiO2-B is a promising material for applications in chemo-resistive gas detectors.

Heavy Metal Removal from Aqueous Effluents by TiO2 and ZnO Nanomaterials

The presence of heavy metals in wastewater, such as Ni, Pb, Cd, V, Cr, and Cu, is a serious environmental problem. This kind of inorganic pollutant is not biodegradable for several years, and its harmful effect is cumulative. Recently, semiconductor nanomaterials based on metal oxides have gained interest due to their efficiency in the removal of heavy metals from contaminated water, by inducing photocatalytic ion reduction when they absorb light of the appropriate wavelength. The most commonly applied semiconductor oxides for these purposes are titanium oxide (TiO2), zinc oxide (ZnO), and binary nanomaterials composed of both types of oxides. The main purpose of this work is to critically analyse the existent literature concerning this topic focusing specially in the most important factors affecting the adsorption or photocatalytic capacities of this type of nanomaterials. In particular, photocatalytic activity is altered by various factors, such as proportion of polymorphs, synthesis method, surface area, concentration of defects and particle size, among others. After a survey of the actual literature, it was found that, although these metal oxides have low absorption capacity for visible light, it is possible to obtain an acceptable heavy metal reduction performance by sensitization with dyes, doping with metallic or nonmetallic atoms, introduction of defects, or the coupling of two or more semiconductors.

Black titania an emerging photocatalyst: review highlighting the synthesis techniques and photocatalytic activity for hydrogen generation

The TiO₂ semiconductor photocatalyst is in the limelight of sustainable energy research in recent years because of its beneficial properties. However, its wide band-gap and rapid exciton recombination rate makes it a lame horse, and reduces its photocatalytic efficiency. Recently, researchers have developed facile methods for lowering the band-gap, so that it captures a wide range of solar spectrum, but the efficiency is still way behind the target value. After the discovery of black titania (B-TiO₂), the associated drawbacks of white TiO₂ and its modified forms were addressed to a large extent because it not only absorbs photons in a broad spectral range (UV to IR region), but also modifies the structural and morphological features, along with the electronic properties of the material, significantly boosting the catalytic performance. Hence, B-TiO₂ effectively converts solar energy into renewable chemical energy i.e. green fuel H₂ that can ultimately satisfy the energy crisis and environmental pollution. However, the synthesis techniques involved are quite tedious and challenging. Hence, this review summarizes various preparation methods of B-TiO₂ and the involved characterization techniques. It also discusses the different modification strategies adopted to improve the H₂ evolution activity, and hopes that this review acts as a guiding tool for researchers working in this field.

Silver-Decorated TiO2 Inverse Opal Structure for Visible Light-Induced Photocatalytic Degradation of Organic Pollutants and Hydrogen Evolution

TiO₂ inverse opal (TIO) structures were prepared by the conventional wet chemical method, resulting in well-formed structures for photocatalytic activity. The obtained structures were functionalized with liquid flame spray-deposited silver nanoparticles (AgNPs). The nanocomposites of TIO and AgNPs were extensively characterized by various spectroscopies such as UV, Raman, X-ray diffraction, energy-dispersive spectroscopy, and X-ray photoelectron spectroscopy combined with microscopic methods such as scanning electron microscopy, transmission electron microscopy (TEM), and high-resolution TEM. The characterization confirmed that high-quality heterostructures had been fabricated with evenly and uniformly distributed AgNPs. Fabrication of anatase TiO₂ was confirmed, and formation of AgNPs was verified with surface plasmon resonant properties. The photocatalytic activity results measured in the gas phase showed that deposition of AgNPs increases photocatalytic activity both under UVA and visible light excitation; moreover, enhanced hydrogen evolution was demonstrated under visible light.