Fabrication of Hierarchical V2 O5 Nanorods on TiO2 Nanofibers and Their Enhanced Photocatalytic Activity under Visible Light

Facile Cu-MOF-derived Co3O4 mesoporous-structure as a cooperative catalyst for the reduction nitroarenes and dyes

The present study describes the environmentally friendly and cost-effective synthesis of magnetic, mesoporous structure-Co3O4 nanoparticles (m-Co3O4) utilizing almond peel as a biotemplate. This straightforward method yields a material with high surface area, as confirmed by various characterization techniques. Subsequently, the utilization of m-Co3O4, graphene oxide (GO), Cu(II)acetate (Cu), and asparagine enabled the successful synthesis of a novel magnetic MOF, namely GO-Cu-ASP-m-Co3O4 MOF. This catalyst revealed remarkable stability that could be easily recovered using a magnet for consecutive use without any significant decline in activity for eight cycles in nitro compound reduction and organic dye degradation reactions. Consequently, GO-Cu-ASP-m-Co3O4 MOF holds immense potential as a catalyst for reduction reactions, particularly in the production of valuable amines with high industrial value, as well as for the elimination of toxic-water pollutants such as organic dyes.

Photocatalytic Carbon Dioxide Conversion by Structurally and Materially Modified Titanium Dioxide Nanostructures

TiO₂ has aroused considerable attentions as a promising photocatalytic material for decades due to its superior material properties in several fields such as energy and environment. However, the main dilemmas are its wide bandgap (3–3.2 eV), that restricts the light absorption in limited light wavelength region, and the comparatively high charge carrier recombination rate of TiO₂, is a hurdle for efficient photocatalytic CO₂ conversion. To tackle these problems, lots of researches have been implemented relating to structural and material modification to improve their material, optical, and electrical properties for more efficient photocatalytic CO₂ conversion. Recent studies illustrate that crystal facet engineering could broaden the performance of the photocatalysts. As same as for nanostructures which have advantages such as improved light absorption, high surface area, directional charge transport, and efficient charge separation. Moreover, strategies such as doping, junction formation, and hydrogenation have resulted in a promoted photocatalytic performance. Such strategies can markedly change the electronic structure that lies behind the enhancement of the solar spectrum harnessing. In this review, we summarize the works that have been carried out for the enhancement of photocatalytic CO₂ conversion by material and structural modification of TiO₂ and TiO₂-based photocatalytic system. Moreover, we discuss several strategies for synthesis and design of TiO₂ photocatalysts for efficient CO₂ conversion by nanostructure, structure design of photocatalysts, and material modification.

Metal Oxide-Based Photocatalytic Paper: A Green Alternative for Environmental Remediation

The interest in advanced photocatalytic technologies with metal oxide-based nanomaterials has been growing exponentially over the years due to their green and sustainable characteristics. Photocatalysis has been employed in several applications ranging from the degradation of pollutants to water splitting, CO2 and N2 reductions, and microorganism inactivation. However, to maintain its eco-friendly aspect, new solutions must be identified to ensure sustainability. One alternative is creating an enhanced photocatalytic paper by introducing cellulose-based materials to the process. Paper can participate as a substrate for the metal oxides, but it can also form composites or membranes, and it adds a valuable contribution as it is environmentally friendly, low-cost, flexible, recyclable, lightweight, and earth abundant. In term of photocatalysts, the use of metal oxides is widely spread, mostly since these materials display enhanced photocatalytic activities, allied to their chemical stability, non-toxicity, and earth abundance, despite being inexpensive and compatible with low-cost wet-chemical synthesis routes. This manuscript extensively reviews the recent developments of using photocatalytic papers with nanostructured metal oxides for environmental remediation. It focuses on titanium dioxide (TiO2) and zinc oxide (ZnO) in the form of nanostructures or thin films. It discusses the main characteristics of metal oxides and correlates them to their photocatalytic activity. The role of cellulose-based materials on the systems’ photocatalytic performance is extensively discussed, and the future perspective for photocatalytic papers is highlighted.

TiO2 and TiO2-Carbon Hybrid Photocatalysts for Diuron Removal from Water

TiO2 and TiO2-activated carbon (AC) photocatalysts have been prepared (by sol-gel synthesis), characterized, and tested in the removal of diuron from water under simulated solar light. The preparation variables of the two series of catalysts are: (i) heat-treatment temperature of bare TiO2 (350, 400, 450 and 500 °C) and (ii) activated carbon content (0.5, 1, 5, and 10 wt.%) in TiO2-AC samples heat-treated at 350 °C. The activated carbon was previously prepared by hydrothermal carbonization of saccharose and has spherical shape. The heat-treatment temperature does not determine the efficiency of TiO2 for diuron photocatalytic degradation, but clearly influences the diuron adsorption capacity. The capacity of TiO2-AC samples for diuron removal increases with the carbon content and it is the result of combined diuron adsorption and photodegradation. Thus, the sample with highest carbon content (10 wt.% nominal) leads to the highest diuron removal. The TiO2-AC photocatalysts have proved to be capable of degrading diuron previously adsorbed in dark conditions, which allows their regeneration.

Synthesis of Magnetic α-Fe2O3/Rutile TiO2 Hollow Spheres for Visible-Light Photocatalytic Activity

The high recombination rate of the electron-hole pair on the surface of rutile TiO2 (RT) reduces its photocatalytic performance, although it has high thermodynamic stability and few internal grain defects. Therefore, it is necessary for RT to develop effective methods to reduce electron-hole pair recombination. In this study, magnetic α-Fe2O3/Rutile TiO2 self-assembled hollow spheres were fabricated via a facile hydrothermal reaction and template-free method. Based on the experimental result, phosphate concentration was found to play a crucial role in controlling the shape of these hollow α-Fe2O3/RT nanospheres, and the optimal concentration is 0.025 mM. Due to a heterojunction between α-Fe2O3 and RT, the electron-hole pair recombination rate was reduced, the as-synthesized hollow α-Fe2O3/RT nanospheres exhibited excellent photocatalysis in rhodamine B (RhB) photodegradation compared to α-Fe2O3 and RT under visible-light irradiation, and the degradation rate was about 16% (RT), 60% (α-Fe2O3), and 93% (α-Fe2O3/RT) after 100 min. Moreover, α-Fe2O3/RT showed paramagnetism and can be recycled to avoid secondary environmental pollution.

Gold Nanoparticle-Decorated Bi2S3 Nanorods and Nanoflowers for Photocatalytic Wastewater Treatment

Colloidal synthesis of photocatalysts with potential to overcome the drawback of low photocatalytic efficiency brought by charge recombination and narrow photo-response has been a challenge. Herein, a general and facile colloidal approach to synthesize orthorhombic phase Bi2S3 particles with rod and flower-like morphology is reported. We elucidate the formation and growth process mechanisms of these synthesized nanocrystals in detail and cooperate these Bi2S3 particles with metallic gold nanoparticles (AuNPs) to construct heterostructured photocatalysts. The unique properties of AuNPs featuring tunable surface plasmon resonance and large field enhancement are used to sensitize the photocatalytic activity of the Bi2S3 semiconductor particles. The morphology, structure, elemental composition, and light absorption ability of the prepared catalysts are characterized by (high-resolution) transmission electron microscopy, scanning electron microscopy, X-ray diffraction spectroscopy, X-ray photoelectron spectroscopy, and UV–vis absorption spectroscopy. The catalysts exhibit high and stable photocatalytic activity for the degradation of organic pollutants demonstrated using rhodamine B and methyl orange dyes under solar light irradiation. We show that the incorporation of the AuNPs with the Bi2S3 particles increases the photocatalytic activity 1.2 to 3-fold. Radical trapping analysis indicates that the production of hydroxyl and superoxide radicals are the dominant active species responsible for the photodegradation activity. The photocatalysts exhibit good stability and recyclability.

TiO2-Graphene Quantum Dots Nanocomposites for Photocatalysis in Energy and Biomedical Applications

The focus of current research in material science has shifted from “less efficient” single-component nanomaterials to the superior-performance, next-generation, multifunctional nanocomposites. TiO2 is a widely used benchmark photocatalyst with unique physicochemical properties. However, the large bandgap and massive recombination of photogenerated charge carriers limit its overall photocatalytic efficiency. When TiO2 nanoparticles are modified with graphene quantum dots (GQDs), some significant improvements can be achieved in terms of (i) broadening the light absorption wavelengths, (ii) design of active reaction sites, and (iii) control of the electron-hole (e−-h+) recombination. Accordingly, TiO2-GQDs nanocomposites exhibit promising multifunctionalities in a wide range of fields including, but not limited to, energy, biomedical aids, electronics, and flexible wearable sensors. This review presents some important aspects of TiO2-GQDs nanocomposites as photocatalysts in energy and biomedical applications. These include: (1) structural formulations and synthesis methods of TiO2-GQDs nanocomposites; (2) discourse about the mechanism behind the overall higher photoactivities of these nanocomposites; (3) various characterization techniques which can be used to judge the photocatalytic performance of these nanocomposites, and (4) the application of these nanocomposites in biomedical and energy conversion devices. Although some objectives have been achieved, new challenges still exist and hinder the widespread application of these nanocomposites. These challenges are briefly discussed in the Future Scope section of this review.

Photoactive Heterostructures: How They Are Made and Explored

In our review we consider the results on the development and exploration of heterostructured photoactive materials with major attention focused on what are the better ways to form this type of materials and how to explore them correctly. Regardless of what type of heterostructure, metal–semiconductor or semiconductor–semiconductor, is formed, its functionality strongly depends on the quality of heterojunction. In turn, it depends on the selection of the heterostructure components (their chemical and physical properties) and on the proper choice of the synthesis method. Several examples of the different approaches such as in situ and ex situ, bottom-up and top-down, are reviewed. At the same time, even if the synthesis of heterostructured photoactive materials seems to be successful, strong experimental physical evidence demonstrating true heterojunction formation are required. A possibility for obtaining such evidence using different physical techniques is discussed. Particularly, it is demonstrated that the ability of optical spectroscopy to study heterostructured materials is in fact very limited. At the same time, such experimental techniques as high-resolution transmission electron microscopy (HRTEM) and electrophysical methods (work function measurements and impedance spectroscopy) present a true signature of heterojunction formation. Therefore, whatever the purpose of heterostructure formation and studies is, the application of HRTEM and electrophysical methods is necessary to confirm that formation of the heterojunction was successful.

Recent Developments in the Use of Heterogeneous Semiconductor Photocatalyst Based Materials for a Visible-Light-Induced Water-Splitting System—A Brief Review

Visible-light-driven photoelectrochemical (PEC) and photocatalytic water splitting systems featuring heterogeneous semiconductor photocatalysts (oxynitrides, oxysulfides, organophotocatalysts) signify an environmentally friendly and promising approach for the manufacturing of renewable hydrogen fuel. Semiconducting electrode materials as the main constituents in the PEC water splitting system have substantial effects on the device’s solar-to-hydrogen (STH) conversion efficiency. Given the complication of the photocatalysis and photoelectrolysis methods, it is indispensable to include the different electrocatalytic materials for advancing visible-light-driven water splitting, considered a difficult challenge. Heterogeneous semiconductor-based materials with narrower bandgaps (2.5 to 1.9 eV), equivalent to the theoretical STH efficiencies ranging from 9.3% to 20.9%, are recognized as new types of photoabsorbents to engage as photoelectrodes for PEC water oxidation and have fascinated much consideration. Herein, we spotlight mainly on heterogenous semiconductor-based photoanode materials for PEC water splitting. Different heterogeneous photocatalysts based materials are emphasized in different groups, such as oxynitrides, oxysulfides, and organic solids. Lastly, the design approach and future developments regarding heterogeneous photocatalysts oxide electrodes for PEC applications and photocatalytic applications are also discussed.

Using a Modified Polyamidoamine Fluorescent Dendrimer for Capturing Environment Polluting Metal Ions Zn2+, Cd2+, and Hg2+: Synthesis and Characterizations

One of the most pressing global concerns is how to provide a clean environment for future generations given the exacerbation of urban, agricultural, industrial, and economic activities due to the escalating size of the global population. A polyamidoamine (PAMAM) dendrimer peripherally modified with 4-N,N′-dimethylethylenediamine-1,8-naphthalmide as a chromophore was synthesized and utilized to capture hazardous heavy metal ions. This modified fluorescent dendrimer (FCD) was complexed with Group 12 metal ions (Zn2+, Cd2+, and Hg2+) at a 2:1 (metal: FCD) ratio. Electronic absorption, fluorescence emission, Infra-red (IR), and nuclear magnetic resonance (1H NMR) spectroscopies, conductivity, CHN elemental, thermogravimetry, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) analyses were used to characterize the resulting metal complexes. These assays revealed that the synthesized complexes were yellow-colored, thermally stable, nanoscale-sized, and composed of [M2FCD]·4Cl2. Considerable spectral shifts were observed in the emission and absorption spectra of the FCD molecule after binding the Zn2+ ions, which can be used to differentiate the Zn2+ complex from the other two complexes. This work provides basic data to facilitate the detection, quantification, and removal of environmentally hazardous heavy metal ions through complexation with a fluorescent dendrimer.

Influence of sulfur amount in Ni-incorporated ZnIn2(O,S)4 on phase formation and the visible light photocatalytic hydrogen evolution reaction

In the present work, we propose Ni-doped ZnIn₂(O,S)₄/In(OH)₃ composite particles for visible-light photocatalytic HER. By adjusting the sulfur concentration while keeping the amounts of zinc, indium and nickel constant during the hydrothermal process.

Efficient solid-state synthesis of biomineralized vaterite-derived pure CaMnO3 perovskite for effective photocatalysis

Biomineralized vaterite-based synthesis of the perovskite CaMnO₃ for effective photocatalytic dye degradation.

Electrospun nanofibrous membranes of cellulose acetate containing hydroxyapatite co-doped with Ag/Fe: morphological features, antibacterial activity and degradation of methylene blue in aqueous solution

Cellulose acetate nanofiber membranes containing hydroxyapatite co-doped with Ag/Fe are effective towards the degradation of MB dye in aqueous solutions.

Preparation and photocatalytic performance of silver-modified and nitrogen-doped TiO2 nanomaterials with oxygen vacancies

A modified hydrothermal method for the synthesis of TiO₂ material to achieve a more efficient visible light response.

Effect of Particle Size and Crystal Surface of CeO2 on the Catalytic Combustion of Benzene

In this study, three kinds of CeO₂ were synthesized, and supported PdO_x (x = 0,1) catalysts were prepared for benzene catalytic combustion. The samples were characterized by XRD, N₂ adsorption/desorption, HRTEM, XPS and H₂-TPR. The results show that three kinds of CeO₂ with different structures can be formed by different preparation methods. This is mainly reflected in the differences in pore structure, particle size and crystal plane. CeO₂-DC obtained from directly calcined Ce(NO₃)₃·6H₂O had the largest pore volume and pore diameter and smallest particle size. CeO₂-DC was mainly exposed to the (200) plane. Combined with the results of the ability test, it could be concluded that when Pd²⁺ and Pd⁰ exist at the same time, the activity increases with an increase in the proportion of Pd²⁺. Meanwhile, the structure of CeO₂ affects the formation of oxygen vacancies, thereby affecting the adsorption and degradation of benzene. This article reveals that the particle size, crystal planes, oxygen vacancies and proportion of Pd²⁺ have a great impact on the catalytic combustion of benzene and allow a more comprehensive understanding of the structure–activity relationship, which can guide us to design high-efficiency catalysts targeted to obtain suitable CeO₂-based catalysts for the catalytic combustion of benzene.

Synthesis, Characterization and Photocatalytic Activity of MoS2/ZnSe Heterostructures for the Degradation of Levofloxacin

Antibiotics have been extensively used over the last few decades. Due to their extensive usage and persistence in the environment, they are considered as emergent pollutants. It is, therefore, important to synthesize new materials for efficient antibiotic degradation. Herein, we report the MoS2/ZnSe heterostructures prepared by a simple ultrasonication method. Heterostructures were prepared with different ratios of MoS2 and ZnSe, i.e., 1:3, 1:1 and 3:1. Characterization of the heterostructures was done by UV-vis diffused reflectance spectroscopy (UV-vis-DRS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and photoluminescence (PL) techniques to understand the morphology and surface chemistry. The results show that an efficient interface was formed to harness the visible light and degrade levofloxacin, which was monitored by gradual decreases in the UV-vis absorbance signal of levofloxacin. Among the prepared heterostructures and their pure counter parts, MoS2/ZnSe 3:1 (3:1 MZ) showed a better degradation activity of 73.2% as compared to pure MoS2 (29%) and ZnSe (17.1%) in the presence of visible light in a time span of two hours. The reusability studies showed that the catalytic performance of 3:1 MZ did not decrease significantly after three cycles. Moreover, the morphology and the crystal structure also remained unchanged.

Vis-Responsive Copper-Modified Titania for Decomposition of Organic Compounds and Microorganisms

Seven commercial titania (titanium(IV) oxide; TiO2) powders with different structural properties and crystalline compositions (anatase/rutile) were modified with copper by two variants of a photodeposition method, i.e., methanol dehydrogenation and water oxidation. The samples were characterized by diffuse reflectance spectroscopy (DRS), X-ray powder diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). Although zero-valent copper was deposited on the surface of titania, oxidized forms of copper, post-formed in ambient conditions, were also detected in dried samples. All samples could absorb visible light (vis), due to localized surface plasmon resonance (LSPR) of zero-valent copper and by other copper species, including Cu2O, CuO and CuxO (x:1-2). The photocatalytic activities of samples were investigated under both ultraviolet (UV) and visible light irradiation (>450 nm) for oxidative decomposition of acetic acid. It was found that titania modification with copper significantly enhanced the photocatalytic activity, especially for anatase samples. The prolonged irradiation (from 1 to 5 h) during samples’ preparation resulted in aggregation of copper deposits, thus being detrimental for vis activity. It is proposed that oxidized forms of copper are more active under vis irradiation than plasmonic one. Antimicrobial properties against bacteria (Escherichia coli) and fungi (Aspergillus niger) under vis irradiation and in the dark confirmed that Cu/TiO2 exhibits a high antibacterial effect, mainly due to the intrinsic activity of copper species.

Facile One-Pot Biogenic Synthesis of Cu-Co-Ni Trimetallic Nanoparticles for Enhanced Photocatalytic Dye Degradation

Biomolecules from plant extracts have gained significant interest in the synthesis of nanoparticles owing to their sustainable properties, cost efficiency, and environmental wellbeing. An eco-friendly and facile method has been developed to prepare Cu-Co-Ni trimetallic nanoparticles with simultaneous bio-reduction of Cu-Co-Ni metal precursors by aqueous extract of oregano (Origanum vulgare) leaves. Dramatic changes in physicochemical properties of trimetallic nanoparticles occur due to synergistic interactions between individual metal precursors, which in turn outclass the properties of corresponding monometallic nanoparticles in various aspects. The as biosynthesized Cu-Co-Ni trimetallic nanoparticles were initially analyzed using ultraviolet (UV)–visible spectroscopy. The morphology, structure, shape, and size of biosynthesized trimetallic nanoparticles were confirmed by transmission electron microscopy (TEM), scanning electron microscopy (SEM), and X-ray diffraction (XRD) spectroscopy. The elemental analysis was carried out by energy-dispersive X-ray (EDX) spectroscopy. Fourier transform infrared (FTIR) microscopy was carried out to explain the critical role of the biomolecules in the Origanum vulgare leaf extract as capping and stabilizing agents in the nanoparticle formation. Additionally, simultaneous thermogravimetric analysis (TGA) and differential thermogravimetry (DTG) analysis was also performed to estimate the mass evaluation and rate of the material weight changes. The photocatalytic activity of as biosynthesized trimetallic nanoparticles was investigated towards methylene blue (MB) dye degradation and was found to be an efficient photocatalyst for dye degradation. Kinetic experiments have shown that photocatalytic degradation of MB dye followed pseudo-first-order kinetics. The mechanism of the photodegradation process of biogenic Cu-Co-Ni trimetallic nanoparticles was also addressed.

Fabrication of Hollow and Porous Tin-Doped Indium Oxide Nanofibers and Microtubes via a Gas Jet Fiber Spinning Process

We report the morphologies of tin-doped indium oxide (ITO) hollow microtubes and porous nanofibers produced from precursor solutions of polyvinylpyrrolidone (PVP), indium chloride (InCl3), and stannic chloride (SnCl4). The polymer precursor fibers are produced via a facile gas jet fiber (GJF) spinning process and subsequently calcined to produce ITO materials. The morphology shows strong dependence on heating rate in calcination step. Solid porous ITO nanofibers result from slow heating rates while hollow tubular ITO microfibers with porous shells are produced at high heating rates when calcined at a peak temperature of 700 °C. The mechanisms of formation of different morphological forms are proposed. The ITO fibers are characterized using several microscopy tools and thermogravimetric analysis. The concentration of inorganic salts in precursor solution is identified as a key factor in determining the porosity of the shell in hollow fibers. The data presented in this paper show that GJF method may be suitable for fabrication of hollow and multi-tubular metal oxide nanofibers from other inorganic precursor materials.

In-situ DRIFT investigation of photocatalytic reduction and oxidation properties of SiO2@α-Fe2O3 core-shell decorated RGO nanocomposite

In this work, SiO₂@α-Fe₂O₃ core-shell decorated RGO nanocomposites were prepared via a simple sol-gel method. The nanocomposites were prepared with different weight percentages (10, 30, and 50 wt %) of the SiO₂@α-Fe₂O₃ core-shell on RGO, and the effects on the structural and optical properties were identified. The photocatalytic reduction and oxidation properties of the nanocomposites in the gas phase were assessed through the reduction of CO₂ and oxidation of ethanol using in-situ diffuse-reflectance infrared fourier transform spectroscopy (DRIFT). The prepared nanocomposite with (30 wt %) of SiO₂@α-Fe₂O₃ showed superior photocatalytic activity for the gas phase reduction of CO₂ and oxidation of ethanol. Enhancement in the activity was also perceived when the light irradiation was coupled with thermal treatment. The DRIFT results for the nanocomposites indicate the active chemical conversion kinetics of the redox catalytic effect in the reduction of CO₂ and oxidation of ethanol. Further, the evaluation of photoelectrochemical CO₂ reduction performance of nanocomposites was acquired by linear sweep voltammetry (LSV), and the results showed a significant improvement in the onset-potential (–0.58 V) for the RGO (30 wt %)-SiO₂@α-Fe₂O₃ nanocomposite.

A new synthesis methodology for SiO2 gel-based nanostructures and their application for elimination of dye pollutants

A new procedure for preparation of a high specific surface area silica-based nanostructure and its copper-containing active photocatalyst is described.

Dual adsorbent-photocatalytic keratin–TiO2 nanocomposite for trimethoprim removal from wastewater

A keratin hydrogel with immersed TiO₂ nanoparticles was developed for the adsorption-photocatalytic degradation of the emerging pollutant trimethoprim.

g-C3N4/TiO2 composite microspheres: in situ growth and high visible light catalytic activity

The g-C₃N₄/TiO₂ heterojunction, possessing a 3D flower-like self-assembled morphology, realizing excellent visible-light photocatalytic properties, is a photocatalyst for wastewater treatment or a photoanode for photoelectrochemical water splitting.

Bandgap engineering of TiO2nanotube photonic crystals for enhancement of photocatalytic capability

TiO₂nanotube photonic crystals with a tunable photonic band gap were constructed by the anodization technique and used as efficient photocatalytic devices.

Recent progress in the design and synthesis of nanofibers with diverse synthetic methodologies: characterization and potential applications

The advancements of nanotechnology, particularly nanomaterials science, have produced a broad range of nanomaterials including nanofibers, nanorods, nanowires and etc., which have been technically and practically examined over various applications.

Synergistic effect of band edge potentials on BiFeO3/V2O5 composite: Enhanced photo catalytic activity

The BiFeO₃/V₂O₅ has been successfully synthesized by simple annealing of BiFeO₃ nanoplates and V₂O₅ nanoflower. The phase, structural, optical properties and chemical state of the BiFeO₃, V₂O₅ and different composition of BiFeO₃/V₂O₅ samples were comparatively characterized by various spectroscopic and microscopic techniques. The prepared catalyst exhibits unique photo catalytic and post-oxidation/reduction ability for removal of various (MB, Phenol, CV, RhB) water organic pollutants. Compared to pure BiFeO₃ and V₂O₅, the different Wt % of BiFeO₃/V₂O₅ composition exhibited higher photo catalytic activity. The fortunate BiFeO₃/V₂O₅ interface hybrid photo catalyst makes a significant impact in the enhancement of photo catalytic reaction. This remarkable efficiency could be ascribed to the synergistic effect between the V₂O₅ petals and BiFeO₃ plates. The exceptional morphology, increased surface area, uniformity, less-agglomerated spreading could increase the ability of visible light response, which lead the improved electron transport ability and the higher charge separation. The enhanced rate of photo generated charge carriers separations were evinced by the EIS and PL spectrum measurements. The allowed radical trapping experiment divulge that the hole (h⁺), and super oxide radical (O₂-) are the minimized effect in degradation, on the other hand hydroxyl radical (OH) is plays the foremost role and act as the active radicals in the catalytic organism. In relations of above investigation, a probable photo degradation mechanism of the as-synthesized photo catalyst is carefully explicated. This effort delivers an effective approach to design and fabricate the efficient photo catalyst through integrating of materials, which has a potential for industrial waste water purification.

Unique CdS@MoS2 Core Shell Heterostructure for Efficient Hydrogen Generation Under Natural Sunlight

The hierarchical nanostructured CdS@MoS2 core shell was architectured using template free facile solvothermal technique. More significantly, the typical hexagonal phase of core CdS and shell MoS2 has been obtained. Optical study clearly shows the two steps absorption in the visible region having band gap of 2.4 eV for CdS and 1.77 eV for MoS2. The FESEM of CdS@MoS2 reveals the formation of CdS microsphere (as a core) assemled with 40-50 nm nanoparticles and covered with ultrathin nanosheets of MoS2 (Shell) having size 200-300 nm and the 10-20 nm in thickness. The overall size of the core shell structure is around 8 µm. Intially, there is a formation of CdS microsphre due to high affinity of Cd ions with sulfur and further growth of MoS2 thin sheets on the surface. Considering band gap ideally in visible region, photocatalytic hydrogen evolution using CdS@MoS2 core shell was investigated under natural sunlight. The utmost hydrogen evolution rate achieved for core shell is 416.4 µmole h-1 with apparent quantum yield 35.04%. The photocatalytic activity suggest that an intimate interface contact, extended visible light absorption and effective photo generated charge carrier separation contributed to the photocatalytic enhancement of the CdS@MoS2 core shell. Additional, the enhanced hole trapping process and effective electrons transfer from CdS to MoS2 in CdS@MoS2 core shell heterostructures can significantly contribute for photocatalytic activity. Such core shell heterostructure will also have potential in thin film solar cell and other microelectronic devices.

Highly Efficient Oxidation of 5-Hydroxymethylfurfural to 2,5-Furandicarboxylic Acid with Heteropoly Acids and Ionic Liquids

2,5-Furandicarboxylic acid (FDCA) is regarded as an important bioderived substitute for petrochemically derived terephthalic acid (PTA), which is widely applied in the polymer industry. This work delineates the base-free oxidation of 5-hydroxymethylfurfural (HMF) to FDCA in an ionic liquid/heteropoly acid (IL-HPA) catalytic system. HPAs displayed high activity for selective oxidation; their active center (Mo/V) was activated by O₂ and transformed from oxygen single and double bonds to epoxy groups, resulting in an FDCA yield of 89 % for HPMV₆ (HPM=H₃ PMo₁₂ O₄₀ ) in the presence of [Bmim]Cl (1-butyl-3-methylimidazolium chloride) under optimized reaction conditions. The high solubility of imidazole ILs for FDCA improved the affinity of HMF and the active centers of the catalyst and protected the furan ring from oxidative cleavage. Furthermore, multiple hydrogen bonds simultaneously formed between the electronegative anions and hydroxy protons of HMF, as well as the hydrogen atoms of the imidazole rings and hydroxy groups, promoting the transformation to aldehyde groups. Various starting materials were studied, and a moderate FDCA yield was obtained from glucose. This work provides an interesting IL-HPA catalytic system for the base-free synthesis of FDCA from accessible monosaccharides and illustrates the great potential of FDCA production from renewable carbohydrates.

Oxygen Vacancy Enhanced Photoreduction Cr(VI) on Few-Layers BiOBr Nanosheets

2D nanomaterials, with unique structural and electronic features, had been demonstrated as excellent photocatalysts, whose catalytic properties could be tunable with surface defect engineering. In this work, few-layer BiOBr nanosheets with oxygen vacancies (BiOBr-Ov) have been fabricated by a simple solvothermal reaction with the help of ethylene glycol. The obtained BiOBr-Ov exhibited the superior photocatalytic performance with a complete reduction of Cr(VI) (20 mg/L) within 12 min by visible light irradiation. Moreover, Cr(VI) with a high concentration (such as 30 mg/L) only requires 2 min to be photoreduced completely under solar light irradiation. The enhanced photocatalytic performance is contributed to the existence of oxygen vacancies. It has been proved by the results of electrochemical impedance and photocurrent that oxygen vacancies can effectively suppress recombination of photogenerated carriers.

UV and Visible Light-Driven Production of Hydroxyl Radicals by Reduced Forms of N, F, and P Codoped Titanium Dioxide

The photocatalytic activities of reduced titanium dioxide (TiO₂) materials have been investigated by measuring their ability to produce hydroxyl radicals under UV and visible light irradiation. Degussa P25 TiO₂ was doped with nitrogen (N), fluorine (F), and/or phosphorus (P) and then subjected to surface modification employing a thermo-physicochemical process in the presence of reducing agent sodium borohydride (NaBH₄). The reduced TiO₂ materials were characterized by a number of X-ray, spectroscopic and imaging methods. Surface doping of TiO₂ was employed to modulate the band gap energies into the visible wavelength region for better overlap with the solar spectrum. Hydroxyl radical generation, central to TiO₂ photocatalytic water purification applications, was quantitated using coumarin as a trap under UV and visible light irradiation of the reduced TiO₂ materials. At 350 nm irradiation, the yield of hydroxyl radicals generated by the reduced forms of TiO₂ was nearly 90% of hydroxyl radicals generated by the Degussa P25 TiO₂. Hydroxyl radical generation by these reduced forms of TiO₂ was also observed under visible light irradiation (419 and 450 nm). These results demonstrated that simple surface modification of doped TiO₂ can lead to visible light activity, which is important for more economical solar-driven applications of TiO₂ photocatalysis.

Exhaustive Photocatalytic Lindane Degradation by Combined Simulated Solar Light-Activated Nanocrystalline TiO2 and Inorganic Oxidants

Organochlorine compounds (OCs) are very toxic, highly persistent, and ubiquitous contaminants in the environment. Degradation of lindane, a selected OC, by simulated solar light-activated TiO2 (SSLA-TiO2) photocatalysis was investigated. The film types of the TiO2 photocatalyst were prepared using a dip-coating method. The physical properties of the films were investigated using X-ray diffraction, transmission electron microscopy, and environmental scanning electron microscopy. The SSLA-TiO2 photocatalysis led to a lindane removal of 23% in 6 h, with 0.042 h−1 of an observed pseudo first-order rate constant (kobs). The SSLA-TiO2 photocatalysis efficiency was greatly enhanced by adding hydrogen peroxide (H2O2), persulfate (S2O82−), or both combined, corresponding to a 64%, 89%, and 99% lindane removal in the presence of 200 µM of H2O2, S2O82−, or equimolar H2O2-S2O82−, respectively. The hydroxyl and sulfate radicals mainly participated in lindane degradation, proven by the results of a radical scavenger study. The degradation kinetics were hindered in the presence of the water constituents, indicated by a 61%, 35%, 50%, 70%, 88%, and 91% degradation of lindane in 6 h, using a SSLA-TiO2/S2O82−/H2O2 photocatalysis system containing 1.0 mg L−1 humic acid (HA), or 1 mM of CO32−, HCO3−, NO3−, SO42−, and Cl−, respectively. The TiO2 film demonstrated high reusability during four runs of lindane decomposition experiments. The SSLA-TiO2/S2O82−/H2O2 photocatalysis is very effective for the elimination of a persistent OC, lindane, from a water environment.

Improvement of the Photoelectrochemical Performance of TiO2 Nanorod Array by PEDOT and Oxygen Vacancy Co-Modification

In this study, oxygen vacancy modified TiO2 nanorod array photoelectrode was prepared by reducing hydrogen atmosphere to increase its free charge carrier density. Subsequently, a p-type conductive poly 3,4-ethylenedioxythiophene (PEDOT) layer was deposited on the surface of oxygen vacancy modified TiO2, to inhibit the surface states. Meanwhile, a p-n heterojunction formed between PEDOT and TiO2 to improve the separation of photo-induced carriers further. The photocurrent of TiO2 nanorod array increased to nearly 0.9 mA/cm2 after the co-modification under standard sunlight illumination, whose value is nearly nine times higher than that of pure TiO2 nanorod array. Thus, this is a promising modification method for TiO2 photoanode photoelectrochemical (PEC) performance improving.

Hierarchically-Structured TiO2/MnO2 Hollow Spheres Exhibiting the Complete Mineralization of Phenol

Although TiO2 or MnO2-based materials have been widely used for the degradation of phenolic compounds, complete mineralization is still a challenge, especially for TiO2-based materials. Here, we devise a hierarchically-structured TiO2/MnO2 (HTM) hollow sphere, in which hollow TiO2 acts as a skeleton for the deposition of MnO2 in order to prevent the aggregation of MnO2 nanoparticles and to maintain its hollow structure. During the oxidation reaction, the as-synthesized HTM can fully exert their respective advantages of the TiO2 and MnO2 species to realize the first stage of the rapid oxidation degradation of phenol and the second stage of the complete photo-mineralization of residual phenol and its intermediates, which efficiently overcomes the incomplete mineralization of phenolic compounds. The degradation mechanism and pathway of phenol are also proposed according to the analysis of Mass Spectrometry (MS). Therefore, this work provides a new insight for exploring hierarchically-structured materials with two or more species.

Enhancement Effect of Ordered Hierarchical Pore Configuration on SO2 Adsorption and Desorption Process

Carbonaceous adsorbents with both high sulfur capacity and easy regeneration are required for flue gas desulfurization. A hierarchical structure is desirable for SO2 removal, since the micropores are beneficial for SO2 adsorption, while the mesopore networks facilitate gas diffusion and end-product H2SO4 storage. Herein, an ordered hierarchical porous carbon was synthesized via a soft-template method and subsequent activation, used in SO2 removal, and compared with coal-based activated carbon, which also had a hierarchical pore configuration. The more detailed, abundant micropores created in CO2 activation, especially the ultramicropores (d < 0.7 nm), are essential in enhancing the SO2 adsorption and the reserves rather than the pore patterns. While O2 and H2O participate in the reaction, the hierarchical porous carbon with ordered mesopores greatly improves SO2 removal dynamics and sulfur capacity, as this interconnecting pore pattern facilitates H2SO4 transport from micropores to mesopores, releasing the SO2 adsorption space. Additionally, the water-washing regeneration performances of the two types of adsorbents were comparatively determined and provide a new insight into the mass-transfer resistance in the pore structure. The ordered hierarchical carbon promoted H2SO4 desorption efficiency and cycled SO2 adsorption–desorption performance, further indicating that interconnecting micro- and mesopores facilitated the diffusion of adsorbates.

Rapid Growth of TiO₂ Nanoflowers via Low-Temperature Solution Process: Photovoltaic and Sensing Applications

This paper reports the rapid synthesis, characterization, and photovoltaic and sensing applications of TiO₂ nanoflowers prepared by a facile low-temperature solution process. The morphological characterizations clearly reveal the high-density growth of a three-dimensional flower-shaped structure composed of small petal-like rods. The detailed properties confirmed that the synthesized nanoflowers exhibited high crystallinity with anatase phase and possessed an energy bandgap of 3.2 eV. The synthesized TiO₂ nanoflowers were utilized as photo-anode and electron-mediating materials to fabricate dye-sensitized solar cell (DSSC) and liquid nitroaniline sensor applications. The fabricated DSSC demonstrated a moderate conversion efficiency of ~3.64% with a maximum incident photon to current efficiency (IPCE) of ~41% at 540 nm. The fabricated liquid nitroaniline sensor demonstrated a good sensitivity of ~268.9 μA mM⁻¹ cm⁻² with a low detection limit of 1.05 mM in a short response time of 10 s.

Photocatalytic Self-Cleaning Cotton Fabrics Coated by Cu₂(OH)PO₄ under VIS/NIR Irradiation

In the present work, a mild strategy was employed to obtain cotton fabrics (CFs) coated with Cu₂(OH)PO₄ (CHP) nanoparticles to achieve self-cleaning property. The phytic acid (IP6) assisted method was employed to synthesize nanoparticles (CHP-IP6). The as-prepared coated cotton fabrics were characterized using the following techniques: Fourier-transform infrared spectroscopy (FTIR), X-ray diffractometry (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) analysis, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA). The CHP-IP6 coated cotton fabrics showed significant photocatalytic activity, excellent photocatalytic stability, and good discoloration of methylene blue (MB) stains when exposed to sunlight, which could have important applications as tablecloths, household apparels, and industrial workwear.

Catalyst-Doped Anodic TiO2 Nanotubes: Binder-Free Electrodes for (Photo)Electrochemical Reactions

Nanotubes of the transition metal oxide, TiO2, prepared by electrochemical anodization have been investigated and utilized in many fields because of their specific physical and chemical properties. However, the usage of bare anodic TiO2 nanotubes in (photo)electrochemical reactions is limited by their higher charge transfer resistance and higher bandgaps than those of semiconductor or metal catalysts. In this review, we describe several techniques for doping TiO2 nanotubes with suitable catalysts or active materials to overcome the insulating properties of TiO2 and enhance its charge transfer reaction, and we suggest anodization parameters for the formation of TiO2 nanotubes. We then focus on the (photo)electrochemistry and photocatalysis-related applications of catalyst-doped anodic TiO2 nanotubes grown on Ti foil, including water electrolysis, photocatalysis, and solar cells. We also discuss key examples of the effects of doping and the resulting improvements in the efficiency of doped TiO2 electrodes for the desired (photo)electrochemical reactions.

Mesoporous Titanium Dioxide: Synthesis and Applications in Photocatalysis, Energy and Biology

Mesoporous materials are materials with high surface area and intrinsic porosity, and therefore have attracted great research interest due to these unique structures. Mesoporous titanium dioxide (TiO₂) is one of the most widely studied mesoporous materials given its special characters and enormous applications. In this article, we highlight the significant work on mesoporous TiO₂ including syntheses and applications, particularly in the field of photocatalysis, energy and biology. Different synthesis methods of mesoporous TiO₂-including sol⁻gel, hydrothermal, solvothermal method, and other template methods-are covered and compared. The applications in photocatalysis, new energy batteries and in biological fields are demonstrated. New research directions and significant challenges of mesoporous TiO₂ are also discussed.