Solvothermal Synthesis of M-doped TiO2 Nanoparticles for Sonocatalysis of Methylene Blue and Methyl Orange (M = Cd, Ag, Fe, Ce, and Cu)

Photocatalytic Degradation of Gaseous Benzene Using Cu/Fe-Doped TiO2 Nanocatalysts under Visible Light

Visible-light-enhanced TiO2 nanocatalysts doped with Cu and Fe were synthesized using the sol-gel method to investigate their performance in degrading gaseous benzene. The structure and morphology of mono- and co-doped TiO2 (i.e., Cu/Fe-TiO2, Cu-Fe-TiO2) were characterized using SEM, EDS, XRD, BET, Raman, UV-vis-DRS, and XPS techniques. The results indicated that the presence of Cu/Fe mono- and co-doped TiO2 leads to the formation of an anatase phase similar to pure TiO2. Furthermore, the introduction of Cu/Fe enhanced the presence of lattice defects and increased the specific surface area of TiO2. This enhancement can be attributed to the increase in oxygen vacancies, especially in the case of Cu-Fe-TiO2. Additionally, Cu-Fe-TiO2 showed a higher concentration of surface-bound hydroxyl groups/chemically adsorbed oxygen and a narrower bandgap than pure TiO2. Consequently, Cu-Fe-TiO2 exhibited the highest photocatalytic performance of 658.33 μgC6H6/(g·h), achieving a benzene degradation rate of 88.87%, surpassing that of pure TiO2 (5.09%), Cu-TiO2 (66.92%), and Fe-TiO2 (59.99%). Reusability tests demonstrated that Cu-Fe-TiO2 maintained a high benzene degradation efficiency of 71.4%, even after five experimental cycles, highlighting its exceptional stability and reusability. In summary, the addition of Cu/Fe to TiO2 enhances its ability to degrade gaseous benzene by prolonging the catalyst's lifespan and expanding its photoresponse range to include visible light.

Photocatalytic hydrogen evolution over cyanine-sensitized Ag/TiO2

Sensitization of TiO2 by dyes such as cyanine and their derivatives is used as a technique to improve potency for the production of hydrogen gas as an alternative green fuel. These dyes shift the spectrum of TiO2 from the UV region to the visible region, enabling it to harvest as much sunlight as possible. Herein, four different derivatives of cyanine (labelled C1, C2, C3, and C4) were prepared and doped in Ag/TiO2 via the impregnation method. The properties of the prepared photocatalysts were studied by XRD, SEM-EDS, FTIR, and UV-visible spectroscopy. The sensitized photocatalysts exhibited a similar morphology, nanoscale particle size, and good absorbance in the visible region. The rate constant for the photocatalytic activity of Ag/TiO2 showed a great enhancement for hydrogen evolution after sensitization from 0.088 to 0.33 μmol min-1. Doping of the C2 derivative in Ag/TiO2 promoted the photocatalytic and sonophotocatalytic rates of H2 production by 7.5 and 9 times, respectively. Also, the amount of photocatalyst had a significant effect on the photocatalytic activity of the sensitized Ag/TiO2, where 0.14 g was the optimum dose, giving the maximum yield at both the initial rate and 300 min. One of the important factors causing the efficiency to reach high levels is the inhibition of photogenerated electron/hole recombination. This was achieved by adding a small quantity of methanol, which increased the rate by 9 times. The stability of the prepared photocatalysts was tested, which gave good results even after their 5th use. All the results confirmed that the sensitization of metal oxides is a promising solution in industry to produce clean energy (H2) in high quantities over highly stable photocatalysts.

Photocatalytic Degradation of Remazol Brilliant Blue R and Remazol Yellow FG using TiO2 doped Cd, Co, Mn

TiO2 and TiO2 doped Cd, Co, Mn (TiO2-M) were synthesized with a sol-gel method, and the photocatalytic activity of Remazol Brilliant Blue R and Remazol Yellow FG has been conducted. TiO2-M (Cd, Co, Mn) was synthesized with the mol Ti:M ratio of 3:1, and the materials were calcined at 300, 400, and 500 °C. The materials were characterized by X-ray Diffraction (XRD), Scanning Electron Microscopy-Energy Dispersive X-ray (SEM-EDX), and UV-Vis Reflectance. The XRD result shows that at the temperature of 300 °C TiO2 and TiO2-M formed tend to be amorphous. At 400 °C the anatase phase is formed, while at 500 °C the rutile phase begins to form. And overall, the crystallinity of TiO2 is higher than metal-doped TiO2. The UV-Vis Reflectance result showed that the bandgap energy of all doping materials (TiO2-M) decreased. The larger the metal ion radius of dopant, the larger the crystal size obtained  and then the higher the bandgap obtained. The results of SEM-EDX showed that the morphology of TiO2 was spherical and regular, whereas the morphology of TiO2-M had a smoother surface due to the influence of metal doping. Photocatalytic activity of TiO2-M on Remazol Brilliant Blue R and Remazol Yellow FG was greater than TiO2. The optimum pH of the solution was obtained at pH 5 and the optimum catalyst phase was obtained at the anatase phase. The percentages degradation for 30 min of Remazol Brilliant Blue R were 67.34% (TiO2), 92.12% (TiO2-Co), 85.47% (TiO2-Mn), and 83.91% (TiO2-Cd), while for Remazol Yellow FG they were 58.84% (TiO2), 74.61% (TiO2-Co), 67.93% (TiO2-Mn) and 64.19% (TiO2-Cd), respectively. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0). 

A Review on Metal Ions Modified TiO2 for Photocatalytic Degradation of Organic Pollutants

TiO2 is a semiconductor material with high chemical stability and low toxicity. It is widely used in the fields of catalysis, sensing, hydrogen production, optics and optoelectronics. However, TiO2 photocatalyst is sensitive to ultraviolet (UV) light; this is why its photocatalytic activity and quantum efficiency are reduced. To enhance the photocatalytic efficiency in the visible light range as well as to increase the number of the active sites on the crystal surface or inhibit the recombination rate of photogenerated electron–hole pairs electrons, various metal ions were used to modify TiO2. This review paper comprehensively summarizes the latest progress on the modification of TiO2 photocatalyst by a variety of metal ions. Lastly, the future prospects of the modification of TiO2 as a photocatalyst are proposed.

Synthesis of Silver Nanoparticles Loaded onto Polymer-Inorganic Composite Materials and Their Regulated Catalytic Activity

We present a novel approach for the preparation of polymer-TiO₂ composite microgels. These microgels were prepared by the in situ hydrolysis and condensation of titanium tetrabutoxide (TBOT) in a mixed ethanol/acetonitrile solvent system, using poly(styrene-co-N-isopropylacrylamide)/poly(N-isopropylacrylamide-co-methacrylic acid) (P(St-NIPAM/P(NIPAM-co-MAA)) as the core component. Silver nanoparticles (AgNPs) were controllably loaded onto the polymer-TiO₂ composite microgels through the reduction of an ammoniacal silver solution in ethanol catalyzed by NaOH. The results showed that the P(St-NIPAM)/P(NIPAM-co-MAA)-TiO₂ (polymer-TiO₂) organic-inorganic composite microgels were less thermally sensitive than the polymer gels themselves, owing to rigid O–Ti–O chains introduced into the three-dimensional framework of the polymer microgels. The sizes of the AgNPs and their loading amount were controlled by adjusting the initial concentration of [Ag(NH₃)₂]⁺. The surface plasmon resonance (SPR) band of the P(St-NIPAM)/P(NIPAM-co-MAA)-TiO₂/Ag (polymer-TiO₂/Ag) composite microgels can be tuned by changing the temperature of the environment. The catalytic activities of the polymer-TiO₂/Ag composite microgels were investigated in the NaBH₄ reduction of 4-nitrophenol. It was demonstrated that the organic-inorganic network chains of the polymer microgels not only favor the mass transfer of the reactant but can also modulate the catalytic activities of the AgNPs by tuning the temperature.