Direct synthesis of hydrogen fluoride-free multilayered Ti3C2/TiO2 composite and its applications in photocatalysis

Ti3C2/TiO2 hybrids are environment-friendly and exhibit excellent photocatalytic and hydrogen-generating power characteristics. Herein, a novel single-step method is proposed for fabricating multilayer structures in which TiO2, generated from (NH4)2TiF6, wraps the Ti3C2 MXene by etching Ti3AlC2 with (NH4)2TiF6. The optimal reaction conditions for the etching of Ti3AlC2 with (NH4)2TiF6 were systematically studied. The phase composition, morphology, and photophysical properties of the Ti3C2/TiO2 hybrids were investigated using X-ray diffraction, field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, and UV-vis spectrophotometry. The thermal stability of the hybrids was investigated using thermogravimetric and differential thermal analyses. Along with the formation of Ti3C2 MXene, Ti3AlC2 reacted with (NH4)2TiF6 at 60 °C for 24 h to form hybrids surrounded by NH4TiOF3 crystals. Subsequent reactions of these hybrids with H3BO3 resulted in the conversion of NH4TiOF3 crystals into TiO2 and eventually into Ti3C2/TiO2 hybrids. Furthermore, the photocatalytic activity of the Ti3C2/TiO2 hybrids was measured by monitoring the photodegradation of methylene blue under ultraviolet light, which showed that the photocatalytic activity of the Ti3C2/TiO2 hybrids was higher than that of the commercial anatase TiO2 nanoparticles.

Synthesis and Application of Innovative and Environmentally Friendly Photocatalysts: A Review

Modern society faces two major challenges: removing pollutants from water and producing energy from renewable sources. To do this, science proposes innovative, low-cost, and environmentally friendly methods. The heterogeneous photocatalysis process fits perfectly in this scenario. In fact, with photocatalysis, it is possible both to mineralize contaminants that are not easily biodegradable and to produce hydrogen from the water splitting reaction or from the conversion of organic substances present in water. However, the main challenge in the field of heterogeneous photocatalysis is to produce low-cost and efficient photocatalysts active under visible light or sunlight. The objective of this review is to compare the new proposals for the synthesis of innovative photocatalysts that reflect the requirements of green chemistry, applied both in the removal of organic contaminants and in hydrogen production. From this comparison, we want to bring out the strengths and weaknesses of the proposals in the literature, but above all, new ideas to improve the efficiency of heterogeneous photocatalysis guaranteeing the principles of environmental and economic sustainability.

The fabrication of TiO2-supported clinoptilolite via F- contained hydrothermal etching and a resultant highly energetic {001} facet for the enhancement of its photocatalytic activity

TiO2-supported clinoptilolite (TiO2/CP) was synthesized in the presence of F- ions. Various characterizations demonstrated that the particle size of loaded TiO2 increased linearly with an increase in the temperature and concentration of F- ions. In particular, the additive F- ions were favored to produce the mutually independent co-exposed {001} and {101} facets of loaded TiO2, while TiO2/CPs synthesized in the absence of F- ions were dominated by the thermodynamically stable {101} facet. As photocatalysts for the removal of crystal violet or methyl orange dyes under UV-irradiation in aqueous solutions, TiO2/CPs (ACP6) synthesized in the presence of F- ions significantly improved the degradation efficiency, as compared to ACP3 obtained in the absence of F- ions. These results elucidated that the highly energetic {001} exposed facet, large particle size and fine dispersion of loaded TiO2 in TiO2/CP accounts for its best photocatalytic performance. The effected mechanism of operational parameters on the degradation performances is proposed.

Green Synthesis and Applications of ZnO and TiO2 Nanostructures

Over the last two decades, oxide nanostructures have been continuously evaluated and used in many technological applications. The advancement of the controlled synthesis approach to design desired morphology is a fundamental key to the discipline of material science and nanotechnology. These nanostructures can be prepared via different physical and chemical methods; however, a green and ecofriendly synthesis approach is a promising way to produce these nanostructures with desired properties with less risk of hazardous chemicals. In this regard, ZnO and TiO2 nanostructures are prominent candidates for various applications. Moreover, they are more efficient, non-toxic, and cost-effective. This review mainly focuses on the recent state-of-the-art advancements in the green synthesis approach for ZnO and TiO2 nanostructures and their applications. The first section summarizes the green synthesis approach to synthesize ZnO and TiO2 nanostructures via different routes such as solvothermal, hydrothermal, co-precipitation, and sol-gel using biological systems that are based on the principles of green chemistry. The second section demonstrates the application of ZnO and TiO2 nanostructures. The review also discusses the problems and future perspectives of green synthesis methods and the related issues posed and overlooked by the scientific community on the green approach to nanostructure oxides.

Zirconium-Doped Chromium IV Oxide Nanocomposites: Synthesis, Characterization, and Photocatalysis towards the Degradation of Organic Dyes

Degradation of organic dyes and their byproducts by heterogeneous photocatalysts is an essential process, as these dyes can be potentially discharged in wastewater and threaten aquatic and xerophyte life. Therefore, their complete mineralization into nontoxic components (water and salt) is necessary through the process of heterogeneous photocatalysis. In this study, Zr/CrO2 (Zirconium-doped chromium IV oxide) nanocomposite-based photocatalysts with different compositions (1, 3, 5, 7 & 9 wt.%) were prepared by an environmentally friendly, solid-state reaction at room temperature. The as-prepared samples were calcined under air at 450 °C in a furnace for a specific period of time. The synthesis of Zr/CrO2 photocatalysts was confirmed by various techniques, including XRD, SEM, EDX, FT-IR, UV-Vis, and BET. The photocatalytic properties of all samples were tested towards the degradation of methylene blue and methyl orange organic dyes under UV light. The results revealed a concentration-dependent photocatalytic activity of photocatalysts, which increased the amount of dopant (up to 5 wt.%). However, the degradation efficiency of the catalysts decreased upon further increasing the amount of dopant due to the recombination of holes and photoexcited electrons.

Irradiation-catalysed degradation of methyl orange using BaF2-TiO2 nanocomposite catalysts prepared by a sol-gel method

BaF2-TiO2 nanocomposite material (hereinafter called the composite) was prepared by a sol-gel method. The composite surface area, morphology and structure were characterized by Brunauer-Emmett-Teller method, X-ray diffraction analysis and a scanning electron microscopy. The results showed that BaF2 and TiO2 form a PN-like structure on the surface of the composite. Composites were used to catalyse the degradation of methyl orange by irradiation with ultraviolet light, γ-rays and an electron beam (EB). It was demonstrated that the composite is found to be more efficient than the prepared TiO2 and commercial P25 in the degradation of methyl orange under γ-irradiation. Increasing the composite catalyst concentration within a certain range can effectively improve the decolorization rate of the methyl orange solution. However, when the composite material is used to catalyse the degradation of organic matter in the presence of ultraviolet light or 10 MeV EB irradiation, the catalytic effect is poor or substantially ineffective. In addition, a hybrid mechanism is proposed; BaF2 absorbs γ-rays to generate radioluminescence and further excites TiO2 to generate photo-charges. Due to the heterojunction effect, the resulting photo-charge will produce more active particles. This seems to be a possible mechanism to explain γ-irradiation's catalytic behaviour.

Recent advances and strategies to tailor the energy levels, active sites and electron mobility in titania and its doped/composite analogues for hydrogen evolution in sunlight

Hydrogen production through photocatalytic water reduction, a potential path for future renewable and sustainable energy generation.

High rate capability performance of ordered mesoporous TiNb6O17 microsphere anodes for lithium ion batteries

We report the synthesis and application of ordered mesoporous TiNb₆O₁₇ microspheres (M-TNO) using a one-step solvothermal method for the first time in lithium-ion batteries. The diameters of TiNb₆O₁₇ microspheres are in the range from 2.2 to 2.4 μm with a mesopore size of about 35 nm, which promotes the electron and ion migration in charge/discharge processes. M-TNO shows a high specific capacitance (307.2 mA h g^-1) at a low current density of 0.2 C and a long-term cycle life over 500 cycles as an electrode. The retentive capacity of the batteries is 77% of the initial cycle after 500 cycles. It is worth noting that M-TNO exhibits excellent rate capacity, which decreases slowly from 265.7 to 172.4 mA h g^-1 with the current density increasing from 1 C to 30 C. The retentive capacity at a current density of 30 C is 65% compared to that at 1 C.

Engineering the Surface/Interface Structures of Titanium Dioxide Micro and Nano Architectures towards Environmental and Electrochemical Applications

Titanium dioxide (TiO₂) materials have been intensively studied in the past years because of many varied applications. This mini review article focuses on TiO₂ micro and nano architectures with the prevalent crystal structures (anatase, rutile, brookite, and TiO₂(B)), and summarizes the major advances in the surface and interface engineering and applications in environmental and electrochemical applications. We analyze the advantages of surface/interface engineered TiO₂ micro and nano structures, and present the principles and growth mechanisms of TiO₂ nanostructures via different strategies, with an emphasis on rational control of the surface and interface structures. We further discuss the applications of TiO₂ micro and nano architectures in photocatalysis, lithium/sodium ion batteries, and Li-S batteries. Throughout the discussion, the relationship between the device performance and the surface/interface structures of TiO₂ micro and nano structures will be highlighted. Then, we discuss the phase transitions of TiO₂ nanostructures and possible strategies of improving the phase stability. The review concludes with a perspective on the current challenges and future research directions.

Immobilization of TiO₂ Nanoparticles on Chlorella pyrenoidosa Cells for Enhanced Visible-Light-Driven Photocatalysis

TiO₂ nanoparticles are immobilized on chlorella cells using the hydrothermal method. The morphology, structure, and the visible-light-driven photocatalytic activity of the prepared chlorella/TiO₂ composite are investigated by various methods. The chlorella/TiO₂ composite is found to exhibit larger average sizes and higher visible-light intensities. The sensitization of the photosynthesis pigment originating from chlorella cells provides the anatase TiO₂ with higher photocatalytic activities under the visible-light irradiation. The latter is linked to the highly efficient charge separation of the electron/hole pairs. The results also suggest that the photocatalytic activity of the composite remains substantial after four cycles, suggesting a good stability.

A facile Pechini sol–gel synthesis of TiO2/Zn2TiO2/ZnO/C nanocomposite: an efficient catalyst for the photocatalytic degradation of Orange G textile dye

We have developed an efficient route for the synthesis of TiO₂/Zn₂TiO₂/ZnO/C nanocomposites through a Pechini sol–gel method followed by heat treatment at 550 °C for 30 min.

Theoretical calculation and experiment study on the electronic structure, microstructures and photocatalytic activity of N–Al codoped TiO2

To more accurately demonstrate how the electronic structure was changed and to explain the origin of the enhanced photocatalytic activity by N–Al codoped TiO₂, we investigated N, Al monodoped, and codoped TiO₂by theoretical calculation and experiments.