Pd nanoparticle loaded TiO<Subscript>2</Subscript> semiconductor for photocatalytic degradation of Paraoxon pesticide under visible-light irradiation

Overuse of the organophosphorus pesticides such as Paraoxon in agriculture industry has raised significant threats to the environment by contamination of soils and groundwaters. Therefore, extensive studies have been carried out to develop an effective method for removing of these poisonous pollutants from contaminated resources. In the current study, Pd nanoparticle loaded TiO₂ nanocomposites with different weight percentages of Pd were prepared via a facile photoreduction method and for the first time, were used for photocatalytic degradation of Paraoxon under visible-light irradiation. The prepared samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, and photoluminescence spectroscopy techniques. In these nanocomposites, the presence of Pd nanoparticles enhances the photocatalytic activity of TiO₂ by their surface plasmon resonance effect and also by narrowing the band gap energy of TiO₂. The results of photocatalytic activity measurements indicate that the nanocomposite with 0.8 wt% content of Pd (PT0.8) has the best photocatalytic activity. The result of total organic carbon test shows that Paraoxon was completely mineralized by PT0.8 photocatalyst after 120 min, under visible-light irradiation.     

TiO<Subscript>2</Subscript> nanotube arrays: hydrothermal fabrication and photocatalytic activities

Titanium dioxide nanotube arrays (TiO₂ NTAs) with rutile phase have been fabricated successfully via a two-step hydrothermal method. TiO₂ nanorod arrays (TiO₂ NRAs) are first hydrothermally grown on FTO substrate. Then the TiO₂ NTAs can be obtained by controlling the HCl concentration of the hydrothermal etching process. The TiO₂ NTAs have been characterized by X-ray diffractometer, scanning electron microscope, transmission electron microscopy, X-ray photoelectron spectroscopy, and ultraviolet–visible spectroscope. Evolution of TiO₂ nanoarrays are accompanied by enhanced of the surface area and optical properties. Compared with TiO₂ NRAs, the prepared TiO₂ NTAs is more efficient in the photodegradation of methyl orange. These results reveal that the hydrothermal chemical etching provide a flexible and straightforward route for design and preparation of TiO₂ NTAs, promising for new opportunities in photocatalysts and other fields.     

Study on carbon quantum dots/BiFeO<Subscript>3</Subscript> heterostructures and their enhanced photocatalytic activities under visible light irradiation

Carbon quantum dots/Bismuth ferrite (CQDs/BiFeO₃) composite materials were successfully synthesized by a facile hydrothermal treatment of Fe(NO₃)₃·9H₂O, Bi(NO₃)₃·5H₂O and CQDs solutions. The structural and optical characteristics of the composite materials were characterized by X-ray diffraction, Fourier transform infra-red spectroscopy, transmission electron microscopy and ultraviolet–visible absorption, respectively. The photocatalytic activities of pure BiFeO₃, CQDs and CQDs/BiFeO₃ composite materials had also been carried out by using Rhodamine B as test stuff. The experimental results indicated that for QDs/BiFeO₃ composite materials, the CQDs were attached to the surfaces of BiFeO₃ materials, CQDs and BiFeO₃ belong to different phase. Owing to the heterojunction formed at the interface between CQDs and BiFeO₃ materials together with CQDs as an electron reservoir, the photocatalytic activities of CQDs/BiFeO₃ composite materials were significantly improved. Especially, the CQDs/BiFeO₃ composite sample with 3.3 wt% CQDs has the highest degradation rate, which was about 7.3, 3.7 times higher than those of pure BiFeO₃ and CQDs, respectively. Moreover, the mechanism of RhB degradation catalyzed by CQDs/BiFeO₃ composite materials was also thoroughly explained.     

Graphdiyne-hybridized N-doped TiO<Subscript>2</Subscript> nanosheets for enhanced visible light photocatalytic activity

In this study, graphdiyne (GD)-hybridized nitrogen-doped TiO₂ nanosheets with exposed (001) facets (GD-NTNS) have been prepared via a hydrothermal reaction and utilized as photocatalyst for the photodegradation of rhodamine B (RhB) under visible light illumination. The resultant GD-NTNS composites exhibit superior visible light photocatalytic activity than that of the bare TiO₂ nanosheets (TNS) and nitrogen-doped TiO₂ nanosheets (NTNS). The enhanced photoactivity can be attributed to the synergistic effects of GD and nitrogen doping with efficient electron transfer and strong visible light absorption. It has been revealed that ^·O^2? and h⁺ are the major species for the enhanced photoactivity under visible light. Our work will facilitate the potential for future design of hybrid materials for practical applications beyond photocatalysts.     

Visible-light activities of Gd<Subscript>2</Subscript>O<Subscript>3</Subscript>/BiVO<Subscript>4</Subscript> composite photocatalysts

Gd₂O₃/BiVO₄ composite photocatalysts were hydrothermal synthesized and characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, and UV–vis diffusion reflectance spectra; all the composite photocatalysts exhibited enhanced photocatalytic activities than the pure BiVO₄ for degradation of methyl orange under visible-light irradiation. The improved activity of composites was discussed and ascribed to the electron-scavenging effect of dopants.     

TiO<Subscript>2</Subscript>/g-C<Subscript>3</Subscript>N<Subscript>4</Subscript> heterojunctions: <Emphasis Type="Italic">In situ</Emphasis> fabrication mechanism and enhanced photocatalytic activity

In situ fabrication of TiO₂/g-C₃N₄ (TCN) heterojunctions was achieved by a modified sol-gel method. TG analysis was employed to determine the content of TiO₂ in TCN composites. XRD, FTIR, TEM and HRTEM were used to analyze the phase composition, functional groups, morphology and microstructure of as-obtained products, respectively. Based on the measurement of surface Zeta potential of g-C₃N₄, a possible mechanism on in situ fabrication of TCN heterojunctions was concluded. The control experiments indicated that TCN heterojunctions exhibited better photocatalytic performance than either TiO₂ or g-C₃N₄, suggesting that the enchanced photocatalytic activity could be realized by TCN heterojunctions. Then, the evaluation of parameters affecting the photocatalytic performance of TCN heterojunctions was investigated. Even after five cycles, TCN heterojunctions still maintained high photocatalytic activity, exhibiting the good photocatalytic stability. UV-vis absorption spectra showed that almost all MB molecules were decomposed in the photocatalytic process. Finally, the possible mechanism on enhanced photocatalytic performance of TCN heterojunctions was discussed.     

Well-organized 3D urchin-like hierarchical TiO<Subscript>2</Subscript> microspheres with high photocatalytic activity

This article reported a well-organized 3D urchin-like hierarchical TiO₂ which was synthesized by a simple solvothermal method without using any template or surfactant. The results of scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, and powder X-ray diffraction showed that the hierarchical morphology and size of TiO₂ could be effectively controlled by adjusting the precursor ratio of tetrabutyl titanate to TiCl₄ solution, the concentration of TiCl₄ solution, the solvothermal temperature, and the reaction time. It is believed that the formation of the urchin-like hierarchical TiO₂ followed a ‘nucleation–self-assembly–dissolution-recrystallization’ growth mechanism. In addition, the excellent photocatalytic activity of the urchin-like hierarchical TiO₂ was confirmed by photodegradation of methyl blue in water.     

Flexible electrospun MWCNTs/Ag<Subscript>3</Subscript>PO<Subscript>4</Subscript>/PAN ternary composite fiber membranes with enhanced photocatalytic activity and stability under visible-light irradiation

Semiconductor photocatalysis is a promising technology for removing contaminants from water. Particularly, visible-light photocatalysis has attracted much attention because of its potential to utilize solar energy. However, nano-sized visible-light-driven photocatalysts easily aggregate during water treatment. Besides, it is difficult to recycle them from treated systems. Therefore, it is of great importance to develop visible-light-responsive immobilized photocatalysts with high activity. In this work, MWCNTs/Ag₃PO₄/polyacrylonitrile (PAN) ternary composite fiber membranes (TCFMs) with good photocatalytic performance were fabricated by electrospinning technique combined with in situ Ag₃PO₄ forming reaction. Due to the addition of MWCNTs, the band gap of MWCNTs/Ag₃PO₄/PAN TCFMs became narrower than that of Ag₃PO₄/PAN binary composite fiber membranes (BCFMs), which made MWCNTs/Ag₃PO₄/PAN TCFMs be able to use light at longer wavelengths. Compared with Ag₃PO₄/PAN BCFMs, the as-prepared MWCNTs/Ag₃PO₄/PAN TCFMs showed enhanced photocatalytic activity and stability for degrading rhodamine B (RhB) in batch processing systems, which mainly ascribed to fast electron transfer from Ag₃PO₄ to MWCNTs and the resulting high electron–hole (e^?–h⁺) separation efficiency. Radical trapping experiments revealed that holes (h⁺) and superoxide radicals (^·O₂^?) played primary roles in RhB degradation. In addition, the flexible MWCNTs/Ag₃PO₄/PAN TCFMs also showed potential practical application in the continuous wastewater treatment by a suitable photocatalytic membrane reactor. This work provides a facile approach to prepare flexible supported photocatalytic membrane with visible-light response, high activity and good stability.     

Self-assembly synthesis of LaPO<Subscript>4</Subscript> hierarchical hollow spheres with enhanced photocatalytic CO<Subscript>2</Subscript>-reduction performance

Urchin-like LaPO4 hollow spheres were successfully synthesized by a facile solution route using citric acid (CA) as a structure-directing agent.The size of the three-dimensional (3D) hollow spheres was tuned by changing the concentration of CA.The formation mechanism of the 3D LaPO4 hollow spheres was revealed by studying the time-dependent morphology evolution process.Importantly,compared with monodispersed one-dimensional (1D) LaPO4 nanorods,the 3D LaPO4 hollow spheres self-assembled from nanorods showed a 6.8-fold enhancement in photocatalytic activity for CO2 reduction,which is attributed to the synergistic effect of their hierarchical hollow structure,higher light-harvesting capacity,and faster electron transfer.Our findings provide not only a simple,facile method for the synthesis of hierarchical hollow micro/nanoarchitectures but also an efficient route for enhancing the photocatalytic performance.     

Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>-nanoparticle-decorated TiO<Subscript>2</Subscript> nanofiber hierarchical heterostructures with improved lithium-ion battery performance over wide temperature range

A facile strategy was designed for the fabrication of Fe₃O₄-nanoparticle-decorated TiO₂ nanofiber hierarchical heterostructures (FTHs) by combining the versatility of the electrospinning technique and the hydrothermal growth method. The hierarchical architecture of Fe₃O₄ nanoparticles decorated on TiO₂ nanofibers enables the successful integration of the binary composite into batteries to address structural stability and low capacity. In the resulting unique architecture of FTHs, the 1D heterostructures relieve the strain caused by severe volume changes of Fe₃O₄ during numerous charge-discharge cycles, and thus suppress the degradation of the electrode material. As a result, FTHs show excellent performance including higher reversible capacity, excellent cycle life, and good rate performance over a wide temperature range owing to the synergistic effect of the binary composition of TiO₂ and Fe₃O₄ and the unique features of the hierarchical nanofibers.

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Photoelectrochemical properties of TiO<Subscript>2</Subscript>/CdS heterostructures

The photoelectrochemical properties of TiO₂, CdS, and TiO₂/CdS anodes have been studied. The results demonstrate that, under illumination, CdS anodes are subject to photocorrosion, and Cd²⁺ ions pass into solution. Corrosion-resistant films of TiO₂ prevent CdS photocorrosion, and the CdS/TiO₂ system exhibits good photosensitivity in the visible range.     

Highly enhanced photocatalytic degradation of dye rhodamine B on the biogenic hierarchical porous TiO<Subscript>2</Subscript>/SiO<Subscript>2</Subscript> with 1D/3D-chain

A hybrid photocatalyst consisting of TiO₂ and nonporous SiO₂ (TiO₂/CS-RH) is prepared by loading TiO₂ sol on one-dimensional/three-dimensional chain (1D/3D-chain) which is synthesized from rice husk. The products are characterized by X-ray diffraction, N₂-adsorption–desorption analysis and scanning electron microscopy. Meanwhile, the corresponding photocatalytic activity is evaluated by measuring the photocatalytic oxidation of rhodamine B (RhB). The results reveal that TiO₂/CS-RH displays a hierarchical porous structure from micrometer to nanometer scale with high BET surface area (574.7–719.4 cm²/g). Meanwhile, the activity of TiO₂/CS-RH for the photocatalytic degradation of RhB in aqueous slurry is significantly higher than that of the unsupported TiO₂. The optimal TiO₂ loaded on the support was two times and then treated at 600 °C for 120 min to complete the conversion of RhB. In contrast, the unsupported TiO₂ photocatalyst could convert only 20% of RhB in the same irradiation time and condition.     

Fabrication of TiO<Subscript>2</Subscript>/ZnO composite nanofibers with enhanced photocatalytic activity

TiO₂/ZnO composite nanofibers have been successfully prepared by electrospinning technique. X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, Raman spectrum, X-ray photoelectron spectroscopy and UV–Vis diffuse reflectance spectroscopy, were used to characterize the as-synthesized nanofibers. The photocatalytic studies revealed that the TiO₂/ZnO nanofibers exhibited enhanced photocatalytic efficiency of photodegradation. Additionally, the recycling experiment of TiO₂/ZnO nanofibers had been done, demonstrating that TiO₂/ZnO nanofibers have high efficiency and stability.     

Synthesis of graphene oxide/Ag<Subscript>3</Subscript>PO<Subscript>4</Subscript> composite with enhanced visible-light photocatalytic activity

The nano-scale Ag₃PO₄ was successfully synthesized by the silver ammonia complexing precipitation method at room temperature. And the Graphene oxide (GO)/Ag₃PO₄ nanocomposites with different contents of GO were successfully synthesized using the electrostatic driving method. The as-prepared GO/Ag₃PO₄ nanocomposites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and UV–visible diffuse reflectance spectroscopy (UV–Vis DRS), confirming that Ag₃PO₄ were highly dispersed to GO sheet. The photocatalytic properties of GO/Ag₃PO₄ were evaluated by the degradation of Methyl Orange (MO) under visible light irradiation and solar irradiation respectively. The results showed that the photocatalytic efficiencies of GO/Ag₃PO₄ nanocomposites had enhanced largely and the kinetics reaction models were followed first-order. Furthermore, 5% GO/Ag₃PO₄ exhibited the highest photocatalytic activity on degradation of MO under visible-light irradiation. The improved photocatalytic performances of the GO/Ag₃PO₄ nanocomposites mainly attributed to the introducing of GO, which benefit for electron transfer and inhibit the recombination of electron–hole pairs, promoting the practical application of Ag₃PO₄ in water purification.     

Fabrication of Ag<Subscript>3</Subscript>PO<Subscript>4</Subscript>-AgBr-PTh composite loaded on Na<Subscript>2</Subscript>SiO<Subscript>3</Subscript> with enhanced visible-light photocatalytic activity

A novel Ag₃PO₄-AgBr-PTh composite loaded on Na₂SiO₃ was synthesized for enhanced visible-light photocatalytic activity. The photocatalytic activity of the samples was evaluated by photodegrading rhodamine B (RhB) under visible light irradiation. The main reactive species and possible photocatalytic mechanism were also discussed. As a result, the Ag₃PO₄-AgBr-PTh composite loaded on Na₂SiO₃ exhibited enhanced photocatalytic activity for RhB compared with Ag₃PO₄ under visible-light irradiation. Additionally, it was demonstrated that the hole (h⁺) and superoxide radical (?O ₂ ^? ) were the major reactive species involving in the RhB degradation. PTh played vital role for the enhanced photocatalytic activity of Ag₃PO₄-AgBr-PTh-Na₂SiO₃ composite, which offered an electron transfer expressway and accelerated the transfer of the electrons from the CB of AgBr into Ag₃PO₄. This work could provide a new perspective for the synthesis of Ag₃PO₄-based composites and the improvement of photocatalytic activity of Ag₃PO₄.     

Novel Bi<Subscript>12</Subscript>TiO<Subscript>20</Subscript>/g-C<Subscript>3</Subscript>N<Subscript>4</Subscript> composite with enhanced photocatalytic performance through Z-scheme mechanism

Novel Bi₁₂TiO₂₀/g-C₃N₄ composite was successfully prepared with Bi₁₂TiO₂₀ nanoparticles embedded within the fluffy crumpled g-C₃N₄ nanosheets. Bi₁₂TiO₂₀/g-C₃N₄ composites exhibit superior photoactivity and stability. As compared with g-C₃N₄ and Bi₁₂TiO₂₀, the photocatalytic efficiency of Bi₁₂TiO₂₀/g-C₃N₄ is effectively enhanced about 1.8- and 4.9-fold, respectively. Based on the trapping experiment, ^·OH and ^·O₂^? radicals are the dominant reactive oxygen species involved in the photocatalytic process. The proposed Z-scheme mechanism of charge transfer markedly promotes the carriers’ migration and separation, leading to the enhanced photocatalytic performance.     

Solar photocatalytic generation of hydrogen under ultraviolet-visible light irradiation on (CdS/ZnS)/Ag<Subscript>2</Subscript>S + (RuO<Subscript>2</Subscript>/TiO<Subscript>2</Subscript>) photocatalysts

In order to efficiently use the UV-vis light in the photocatalytic reaction, a novel (CdS/ZnS)/Ag₂S + RuO₂/TiO₂ was synthesized by chemical coprecipitation and metal ion implantation. The composition and structure of this composite were characterized by BET, UV-vis spectroscopy, SEM, XRD and EDX. This composite exhibited much higher photocatalytic activity for the generation of hydrogen (H₂).     

Ferroin adsorption on TiO<Subscript>2</Subscript>-based photocatalytic materials

We have studied ferroin adsorption on photocatalytically active nanocomposites based on TiO₂ doped with Fe³⁺, Nb⁵⁺, or W⁶⁺. The results demonstrate that the mass of an adsorbed organic substance correlates with the photocatalytic activity of the photocatalysts. High-temperature heat treatment of the nanocomposites increases manyfold the mass of an organic substance adsorbed from an aqueous solution for unit free surface area of the photocatalyst.     

Preparation of TiO<Subscript>2</Subscript>/Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>/CF composites for enhanced microwave absorbing performance

To meet the demand of electromagnetic absorption, cheap and easily available microwave absorbents are urgently required. As an important functional material, carbon fibers (CFs) have been widely reported, however, too high conductivity easily leads to the impedance mismatch, which is not favorable to the microwave absorbing performance (MAP). To address this challenge, in this study, novel TiO₂/Fe₃O₄/CF composites with tunable magnetic were synthesized by hydrothermal method and characterized by SEM, XRD, XPS and VSM. As absorbents, the minimum reflection loss (R_L) value is ??41.52 dB at a thickness of 2.1 mm, and the corresponding bandwidth with effective attenuation (R_L?<???10 dB) is up to 5.65 GHz (4.54–10.19 GHz). More importantly, the plausible mechanisms for the enhanced MAP are explored.     

Efficient visible-light driven photocatalysts: coupling TiO<Subscript>2</Subscript>(AB) nanotubes with g-C<Subscript>3</Subscript>N<Subscript>4</Subscript> nanoflakes

The wide application of the titanium dioxide (TiO₂) as the photocatalysts is greatly hindered by its intrinsic large band gap and usually fast electron–hole recombination. Here, we reported the exploration of coupling g-C₃N₄ nanoflakes to TiO₂ nanotubes with the anatase and TiO₂(B) mixed phases (TiO₂(AB)) toward the efficient visible-light-driven hybrid photocatalyst. It is found that coupling TiO₂(AB) nanotubes with g-C₃N₄ nanoflakes could bring a profoundly extension the visible light adsorption capacity and enhanced photogenerated carrier separation. Accordingly, they exhibit much higher efficient photocatalytic activities toward the degradation of sulforhodamine B under the visible light irradiation, which is enhanced for nearly 15 times to those of the TiO₂(AB) and g-C₃N₄, suggesting their promising practical applications as novel and efficient semiconductor photocatalysts for the water purification.