One-step synthesis of mulberry-shaped TiO2-Au nanocomposite and its H2 evolution property under visible light

Facile Synthesis of Anatase–Rutile Diphase N-doped TiO2 Nanoparticles with Excellent Visible Light Photocatalytic Activity

To further boost the charge separation and photocatalytic activity of TiO2 under visible light, the anatase–rutile mixed-phase nitrogen-doped (N-doped) TiO2 nanoparticles were successfully synthesized through a facile one-step calcining procedure using TiN as raw materials. The crystal phases, morphologies, chemical compositions, textural structures, and optical properties of as-obtained N-doped TiO2 were characterized by the corresponding analytical techniques. The photocatalytic activities of as-fabricated samples were evaluated by degrading 4-chlorophenol (4-CP) and methylene blue (MB) aqueous solution under visible light irradiation. The results revealed that the ratio of rutile to anatase increased with the improvement of sintering temperature, and the sample prepared at 500 °C had the best photocatalytic activity. This might be because it possessed the most appropriate rutile/anatase proportion as well as the nitrogen doping. The transient photocurrent responses, photoluminescence spectra (PL) measurements, and active species trapping experiments were implemented to disclose the photocatalytic mechanism. This work will provide a further insight into the synthesis of highly efficient N-doped TiO2 photocatalysts for organic contaminant removal.

Synthesis of Micro- and Nanoparticles in Sub- and Supercritical Water: From the Laboratory to Larger Scales

The use of micro- and nanoparticles is gaining more and more importance because of their wide range of uses and benefits based on their unique mechanical, physical, electrical, optical, electronic, and magnetic properties. In recent decades, supercritical fluid technologies have strongly emerged as an effective alternative to other numerous particle generation processes, mainly thanks to the peculiar properties exhibited by supercritical fluids. Carbon dioxide and water have so far been two of the most commonly used fluids for particle generation, the former being the fluid par excellence in this field, mainly, because it offers the possibility of precipitating thermolabile particles. Nevertheless, the use of high-pressure and -temperature water opens an innovative and very interesting field of study, especially with regards to the precipitation of particles that could hardly be precipitated when CO2 is used, such as metal particles with a considerable value in the market. This review describes an innovative method to obtain micro- and nanoparticles: hydrothermal synthesis by means of near and supercritical water. It also describes the differences between this method and other conventional procedures, the most currently active research centers, the types of particles synthesized, the techniques to evaluate the products obtained, the main operating parameters, the types of reactors, and amongst them, the most significant and the most frequently used, the scaling-up studies under progress, and the milestones to be reached in the coming years.

Highly Crystalline Ordered Cu-dopedTiO2Nanostructure by Paper Templated Method: Hydrogen Production and Dye Degradation under Natural Sunlight

A highly crystalline ordered Cu-TiO2 nanostructure was synthesized using a simple paper template method using cupric nitrate and titanium isopropoxide as precursors. The structural study by XRD confirmed the formation of highly crystalline anatase phase of Cu-TiO2. The broad diffraction peaks of Cu-TiO2 exhibit the nanocrystalline nature of the product. The optical study by UV-DRS indicated the red shift in absorption wavelength with an increase in Cu doping, i.e., towards the visible region. The FE-SEM and FE-TEM study validated the formation of spherical shaped nanoparticles of Cu-TiO2 having sizes in the range of 20–30 nm. Considering the absorption in the visible region, the photocatalytic study was performed for water splitting and rhodamine-B (RhB) dye degradation under natural sunlight. The 2% Cu-doped TiO2 showed the highest photocatalytic hydrogen evolution, i.e., 1400 µmol·g−1·h−1 from water, among the prepared compositions. The photocatalytic performance of Cu-TiO2 conferred complete degradation of RhB dye within 40 min. The higher activity in both cases was attributed to the formation of highly crystalline ordered nanostructure of Cu-doped TiO2. This synthesis approach has potential to prepare other highly crystalline ordered nanostructured semiconductors for different applications.