Fabrication and characterization of CdS/BiVO4 nanocomposites with efficient visible light driven photocatalytic activities

Novel CdS/BiVO₄ nanocomposites were synthesized by simple solvothermal method. The as-prepared samples were characterized by transmission electron microscopy (TEM), scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), Raman spectroscopy, UV–vis diffuse reflectance spectra (DRS), Fourier transform infrared spectra (FT-IR) and photoluminescence (PL). In the nanocomposites, CdS particles were deposited on the surface of the BiVO₄. The photocatalytic tests showed that the CdS/BiVO₄ nanocomposites possessed a higher rate for degradation of malachite green (MG) than the pure BiVO₄ under visible light irradiation. The 1.5-CdS/BiVO₄ nanocomposite photocatalyst was found to degrade 98.3% of MG under visible light irradiation. Moreover, the photocatalytic mechanism of CdS/BiVO₄ nanocomposites was also discussed. The results showed that the nanocomposite construction between CdS and BiVO₄ played a very important role in their photocatalytic properties, which has the potential application in solving environmental pollution issues utilizing solar energy effectively.     

One-dimensional spindle-like BiVO4/TiO2 nanofibers heterojunction nanocomposites with enhanced visible light photocatalytic activity

One-dimensional spindle-like BiVO₄/TiO₂ nanofibers heterojunction nanocomposites with high visible light photocatalytic activity have been successfully obtained by combining the electrospinning technique and solvothermal method. The as-obtained products were characterized by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV–vis spectra and photoluminescence (PL) spectra. The results revealed that spindle-like BiVO₄ nanostructures were successfully grown on TiO₂ nanofibers. Photocatalytic tests showed that the BiVO₄/TiO₂ nanofibers heterojunction nanocomposites showed enhanced visible light photocatalytic activity than that of pure TiO₂ nanofibers, which might be attributed to the effective photogenerated electrons-holes separation based on the photosynergistic effect of the BiVO₄/TiO₂ heterojunction. Moreover, the BiVO₄/TiO₂ nanofibers heterojunction nanocomposites could be easily recycled without any decrease of the photocatalytic activity.     

Hydrothermal synthesis and visible-light photocatalytic activity of porous peanut-like BiVO4 and BiVO4/Fe3O4 submicron structures

Porous peanut-like BiVO₄ and BiVO₄/Fe₃O₄ submicron structures were synthesized by a template-free hydrothermal process at 160 °C for 24 h. The as-synthesized samples were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), vibrating sample magnetometer (VSM) and UV–vis spectroscopy. The photocatalytic activity of BiVO₄ and BiVO₄/Fe₃O₄ submicron structures were evaluated for the degradation of Rhodamine B (RhB) and methylene blue (MB) under visible light irradiation with and without the assistance of H₂O₂. According to the experimental results obtained, porous peanut-like BiVO₄/Fe₃O₄ composite photocatalyst shows higher photocatalytic activity in the H₂O₂-assisted system under visible light irradiation compared to BiVO₄. Recycling test on the BiVO₄/Fe₃O₄ composite photocatalyst for the degradation of RhB under visible light irradiation indicates that the composite photocatalyst is stable in the H₂O₂-assisted system in five cycles. Therefore, this composite photocatalyst will be beneficial for efficient degradation of organic pollutants present in water and air under solar light.     

Visible light induced photocatalytic activity of MnO2/BiVO4 for the degradation of organic dye and tetracycline

In this work, α-MnO₂/BiVO₄ nanocomposites with varying MnO₂ contents (0–7 wt%) were successfully prepared via the simple chemical method. The structure, morphology, and optical properties of prepared nanocomposites were studied by various analytical techniques including X-ray diffraction (XRD), scanning electron microscopy (SEM), UV–visible absorption spectroscopy, and photoluminescence (PL) spectroscopy. The photocatalytic efficiency of α-MnO₂/BiVO₄ nanocomposites was studied via decomposition of rhodamine B (RhB) and tetracycline (TC) under exposure to visible light (λ ≥ 420 nm). Due to good structure and composite advantages, 5%MnO₂/BiVO₄ (MnBV-5) photocatalyst exhibited superior RhB and TC degradation efficiency to all other samples. In addition, the MnBV-5 photocatalyst showed good stability, and no apparent reduction in photocatalysis efficiency was noted after five testing cycles. Therefore, the MnO₂/BiVO₄ nanocomposite demonstrated a good potential for photocatalytic decomposition of new water contaminants.     

One-pot synthesis of CdS sensitized TiO2 decorated reduced graphene oxide nanosheets for the hydrolysis of ammonia-borane and the effective removal of organic pollutant from water

A hybrid material of reduced graphene oxide (RGO) sheets decorated with CdS-TiO₂ NPs was prepared through a facile one-pot hydrothermal method. The assembly of CdS-TiO₂ nanoparticles (NPs) on RGO sheets was in-situ produced. As-synthesized nanocomposites were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), energy disperse X-ray spectrum (EDS), fourier transform infrared spectroscopy (FTIR), and photoluminescence spectroscopy (PL). The obtained nanocomposites exhibited a good photocatalytic activity for the visible-light-induced decomposition of methylene blue (MB) dye and hydrolysis of ammonia borane. The results showed that by incorporation of CdS and TiO₂ NPs on graphene oxide sheets the photocatalytic efficiency was enhanced. The significant enhancement in the photocatalytic activity of CdS-TiO₂/RGO nanocomposites under visible light irradiation can be ascribed to the effect of CdS by acting as electron traps in TiO₂ band gap. Reduced graphene oxide worked as the adsorbent, electron acceptor and a photo-sensitizer to efficiently enhance the dye photo decomposition. Such nanocomposite photocatalyst might find potential application in a wide range of fields, including hydrogen energy generation, air purification, and wastewater treatment.     

Ag nanoparticles loaded TiO2/MWCNT ternary nanocomposite: A visible-light-driven photocatalyst with enhanced photocatalytic performance and stability

A visible light active photocatalyst, Ag/TiO₂/MWCNT was synthesized by loading of Ag nanoparticles onto TiO₂/MWCNT nanocomposite. The photocatalytic activity of Ag/TiO₂/MWCNT ternary nanocomposite was evaluated for the degradation of methylene blue dye under UV and visible light irradiation. Ag/TiO₂/MWCNT ternary nanocomposite exhibits (~9 times) higher photocatalytic activity than TiO₂/MWCNT and (~2 times) higher than Ag/TiO₂ binary nanocomposites under visible light irradiation. The enhancement in the photocatalytic activity is attributed to the synergistic effect between Ag nanoparticles and MWCNT, which enhance the charge separation efficiency by Schottky barrier formation at Ag/TiO₂ interface and role of MWCNT as an electron reservoir. Effect of different scavengers on the degradation of methylene blue dye in the presence of catalyst has been investigated to find the role of photogenerated electrons and holes. Simultaneously, the Ag/TiO₂/MWCNT shows excellent photocatalytic stability. This work highlights the importance of Ag/TiO₂/MWCNT ternary nanocomposite as highly efficient and stable visible-light-driven photocatalyst for the degradation of organic dyes.     

Photoactive behavior of polyacrylonitrile fibers based on silver and zirconium co‐doped titania nanocomposites: Synthesis,characterization, and comparative study of solid‐phase photocatalytic self‐cleaning

Silver and zirconium co‐doped and mono‐doped titania nanocomposites were synthesized and deposited onto polyacrylonitrile fibers via sol–gel dip‐coating method. The resulted coated‐fibers were characterized by X‐ray diffraction (XRD), scanning electron microscopy, energy dispersive spectroscopy, transmission electron microscopy, diffuse reflectance spectroscopy, thermogravimetric analysis, and BET surface area measurement. Photocatalytic activity of the TiO₂‐coated and TiO₂‐doped coated fibers were determined by photomineralization of methylene blue and Eosin Y under UV–vis light. The progress of photodegradation of dyes was monitored by diffuse reflectance spectroscopy. The XRD results of samples indicate that the TiO₂, Ag‐TiO₂, Zr‐TiO₂, and Ag‐Zr‐TiO₂ consist of anatase phase. All samples demonstrated photo‐assisted self‐cleaning properties when exposed to UV–vis irradiation. Evaluated by decomposing dyes, photocatalytic activity of Ag–Zr co‐doped TiO₂ coated fiber was obviously higher than that of pure TiO₂ and mono‐doped TiO₂. Our results showed that the synergistic action between the silver and zirconium species in the Ag‐Zr TiO₂ nanocomposite is due to both the structural and electronic properties of the photoactive anatase phase. These results clearly indicate that modification of semiconductor photocatalyst by co‐doping process is an effective method for increasing the photocatalytic activity. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

One-pot solvothermal synthesis of carbon dots/Ag nanoparticles/TiO2 nanocomposites with enhanced photocatalytic performance

In this paper, we reported a “green” and facile method for one-pot solvothermal synthesis of carbon dots (CDs)/Ag nanoparticles (AgNPs)/titanium dioxide (TiO₂, commercial Degussa P25) ternary nanocomposites with enhanced photocatalytic performance. The characterizations of this ternary photocatalyst were studied at length and our results revealed that the crystalline phase of TiO₂ component remained unchanged after the reaction. While the newborn AgNPs and CDs were tightly attached onto the surface of TiO₂ nanoparticles. The photocatalytic activities of photocatalysts were tested by measurements of photo-degradation on methylene blue (MB) under ultraviolet (UV) and visible light. It was showed that the photocatalytic performance of the ternary photocatalyst was superior to that of single TiO₂ or CDs/TiO₂ binary photocatalyst. It was probably attributed to the synergistic effect of the photoelectrical properties of CDs and the surface plasmon resonance (SPR) effect of AgNPs, which could both enhance the absorption of visible light and hinder the recombination of photogenerated electron-hole pairs.     

Construction of BiVO4 microspheres sensitized TiO2 NTAs for the enhanced photocatalytic mineralization of organic dyes

In the present work, BiVO₄ microspheres were deposited on TiO₂ NTAs via the solvothermal method using urea as the mineralizer. The binary heterojunction formation significantly enhanced the solar response region and intensity, and the electron transfer path was built at the interface of two semiconductors, which was the main reason for the enhanced photoelectrochemical and photocatalytic performances. The S-2 electrode prepared with urea concentration of 2 mol/L displayed the high visible light photocurrent of 73.76 μA/cm² and photovoltage of −0.30 V. Furthermore, the S-2 photocatalyst also showed excellent photocatalytic decoloration ability of MO, RhB and MB dyes, and the corresponding decomposition efficiencies were 55.82%, 41.62% and 89.90% under solar irradiation. Except for the organic dyes, Cr(VI) ions also could be reduced into Cr(III), and the photocatalytic efficiency achieved 74.05% after 3 h solar irradiation. The active group and photocatalytic mechanism were proposed to illuminate the essential reason. The experimental results indicated that the novel BiVO₄/TiO₂ NTAs with binary heterojunction are attractive photocatalysts for the dyeing and printing water treatment.     

Preparation and photocatalysis of TiO2-fluoropolymer electrospun fiber nanocomposites

The preparation and photocatalytic properties of titanium dioxide (TiO₂)-fluoropolymer fiber nanocomposites were studied. The fluoropolymer nanofibers with carboxyl group were prepared by electrospinning. The complex was formed between carboxyl on fluoropolymer electrospun fiber surface and titanium ion, and then the TiO₂ nanoparticles were immobilized on the surface of fluoropolymer electrospun fibers through hydrothermal complex-precipitation. By controlling the reaction conditions, different sizes and numbers of TiO₂ nanocrystals can be obtained. The Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) results reveal that an interaction exists between TiO₂ and fluoropolymer fibers. The degradation of methylene blue solution is performed by TiO₂-fluoropolymer fiber nanocomposites under UV irradiation. There may be an adsorption-migration-photodegradation process during the degradation of methylene blue by using TiO₂-fluoropolymer fiber nanocomposites as photocatalyst. The experimental results show that the TiO₂-fluoropolymer fiber nanocomposites have good photocatalytic ability, recycling and stability for the potential applicability in an environmental remediation.     

Preparation of CdS/TiO2 nanotube arrays and the enhanced photocatalytic property

In this paper, a series of CdS/TiO₂ NTs have been synthesized by SILAR method. The as-prepared CdS/TiO₂ NTs have been analyzed by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive spectrometer (EDS), and ultraviolet–visible (UV–vis). And their photocatalytic activities have been investigated on the degradation of methylene blue under simulated solar light irradiation. XRD results indicate that TiO₂ NTs were anatase phase, CdS nanoparticles were hexagonal phase. FESEM results indicate that low deposition concentration can keep the nanotubular structures. UV–vis results indicate that CdS can be used to improve the absorbing capability of TiO₂ NTs for visible light, and the content of CdS affects the band gap. Photocatalytic results indicate that CdS nanoparticles are conducive to improve the photocatalytic efficiency of TiO₂ NTs, and the highest degradation rate can reach 93.8%. And the photocatalytic mechanism of CdS/TiO₂ NTs to methylene blue is also described.     

Photocatalytic activity enhancement by composition control of mechano-thermally synthesized BiVO4-Cu2O nanocomposite

In this paper, BiVO₄-Cu₂O nanocomposites have been synthesized by a mechano-thermal method with a controlled composition of Bi₂O₃, V₂O₅ and Cu₂O contents. The effects of milling time, heat treatment temperature and composition on the structure and microstructure of the prepared samples were studied. The optical properties and photocatalytic performance of the samples under visible light irradiation were studied by Diffuse reflectance spectroscopy (DRS), photoluminescence (PL) and dye degradation. The BiVO₄ and Cu₂O contents in the nanocomposite were changed and the effects on the structural stability and photocatalytic performance were studied. X-ray diffraction (XRD) patterns showed that both BiVO₄ and Cu₂O contents were effective on the synthesis and stability of the monoclinic phase of BiVO₄. Field emission scanning electron microscopy (FESEM) micrographs indicated semi-spherical nanocomposite particles with an average particle size of 100 nm. The heterostructure at the interface between Cu₂O and BiVO₄ was shown by Transmission electron microscopy (TEM) and proved by X-ray photoelectron spectroscopy (XPS) spectra. DRS results indicated the minimum band gap energy of 2.12 eV for BiVO₄-10 wt% of Cu₂O with a 10 wt% excessive V₂O₅ content. The PL result has shown the lowest rate of the recombination of electron-holes for this sample. Also, the maximum degradation of 97% has been obtained for methylene blue (MB) by this sample after 240 min of being irradiated in visible light region. The photocatalytic mechanism was determined using scavengers. The kinetics of MB and methyl orange (MO) degradations was compared to study the effect of pH on the photocatalytic performance.     

Study on properties and synthesis of sulfonated coal supported nanostructure TiO2 photocatalysts

Nano-TiO₂ was synthesized with titanium sulfate by a simple economical microwave-assisted-hydrolysis method, and it was successfully coated on semi-organic-matter sulfonated coal (SC). SC as a semi-organic matter was first chosen as the substrate of nano-TiO₂. Their surface morphology and structure were investigated by scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD). The hybrid nano-composite photocatalyst exhibited a good photocatalytic activity in degrading methylene blue (MB). Results revealed that under the assistance of microwave-process, the anatase TiO₂ can be synthesized at low temperature (around 100 °C), presents a strong crystalline and has a good photocatalytic performance.     

Synthesis and photocatalytic behavior of BiVO4 with decahedral structure

Decahedral BiVO₄ was successfully synthesized with Tween-80 as a template by the microwave hydrothermal method. The effects of hydrothermal temperature and Tween-80 on crystal phase and morphology of the obtained BiVO₄ were investigated. The crystal phase and morphology were characterized by X-ray diffraction, field emission scanning electron microscopy and UV–vis diffuse reflectance spectroscopy. The results indicated that the as-prepared decahedral BiVO₄ was monoclinic. The photocatalytic behavior for methylene blue (MB) degradation was enhanced with the assistance of an appropriate amount of hydrogen peroxide (H₂O₂) under visible light irradiation. The photocatalytic tests indicated that the photocatalytic efficiency of decahedral BiVO₄ synthesized at 180 °C was 63.5%. However, BiVO₄ sample synthesized at 160 °C showed the highest photocatalytic degradation rate, up to 81.6%, due to its small size and crystal defects.     

Microwave hydrothermal synthesis and photocatalytic properties of TiO2/BiVO4 composite photocatalysts

TiO₂/BiVO₄ composite photocatalysts with heterojunction structures were synthesized by the one-step microwave hydrothermal method. The physical and photophysical properties of the as-prepared photocatalysts were fully characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), UV–vis diffuse reflectance spectra, photoluminescence (PL) and BET surface area analysis. The photocatalytic activities were evaluated by the decolorization of rhodamine B under UV and simulated sun-light irradiation. The results reveal that the as-prepared TiO₂/BiVO₄ composites exhibit higher photocatalytic activities than pure BiVO₄. The 20% TiO₂/BiVO₄ sample shows the best photocatalytic activity. The enhancement of photocatalytic activity is mainly attributed to the increasing separation rate of photogenerated charge carriers. The possible photocatalytic mechanism is discussed on the basis of the calculated energy band positions.     

Efficient solar photocatalyst based on cobalt oxide/iron oxide composite nanofibers for the detoxification of organic pollutants

A Co₃O₄/Fe₂O₃ composite nanofiber-based solar photocatalyst has been prepared, and its catalytic performance was evaluated by degrading acridine orange (AO) and brilliant cresyl blue (BCB) beneath solar light. The morphological and physiochemical structure of the synthesized solar photocatalyst was characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FTIR). FESEM indicates that the Co₃O₄/Fe₂O₃ composite has fiber-like nanostructures with an average diameter of approximately 20 nm. These nanofibers are made of aggregated nanoparticles having approximately 8.0 nm of average diameter. The optical properties were examined by UV-visible spectrophotometry, and the band gap of the solar photocatalyst was found to be 2.12 eV. The as-grown solar photocatalyst exhibited high catalytic degradation in a short time by applying to degrade AO and BCB. The pH had an effect on the catalytic performance of the as-grown solar photocatalyst, and it was found that the synthesized solar photocatalyst is more efficient at high pH. The kinetics study of both AO and BCB degradation indicates that the as-grown nanocatalyst would be a talented and efficient solar photocatalyst for the removal of hazardous and toxic organic materials.     

Ceramic tiles coated with Zr-Ag co-doped TiO2 thin film for indoor air purifying and antimicrobial applications

In this study, Zr-Ag co-doped TiO₂ (ZAT) photocatalyst films having varied numbers of layers (1, 2, 3, and 4) have been developed to coat on ceramic tile substrates by sol-gel spin coating technique. The specimens were tested to determine antibacterial activity against Escherichia coli and the capability to degrade gaseous formaldehyde under visible light. X-ray diffraction, ultraviolet and visible absorption spectroscopy, water contact angle, and scanning electron microscopy were applied to characterize the structural and morphological properties of the samples. The photocatalytic reactivity of the nanocomposite films was investigated by the decolorization of methylene blue (MB) dye under visible light irradiation. The results showed that the two-layer ZAT photocatalyst film on ceramic tile exhibited the highest photocatalytic decolorization of MB, with 60.36% efficiency. The ZAT tile had formaldehyde degradation efficiency up to 32.74% within only 6 h under visible light irradiation, higher than that of the bare ceramic tile (4.90%). Additionally, the ZAT thin films could enhance anti-E. coli activity and could be capable of degrading air pollution.     

Fabrication of core–shell nanocomposites with enhanced photocatalytic efficacy

The current study establishes the unprecedented involvement in the evolution and production of novel core–shell nanocomposites composed of nanosized titanium dioxide and aniline‐o‐phenylenediamine copolymer. TiO₂@copoly(aniline and o‐phenylenediamine) (TiO₂@PANI‐o‐PDA) core–shell nanocomposites were chemically synthesized in a molar ratio of 5:1 of the particular monomers and several weights of nano‐TiO₂ via oxidative copolymerization. The construction of the TiO₂@PANI‐o‐PDA core–shell nanocomposites was ascertained from Fourier transform IR spectroscopy, UV–visible spectroscopy and XRD. A reasonable thermal behavior for the original copolymer and the TiO₂@PANI‐o‐PDA core–shell nanocomposites was investigated. The bare PANI‐o‐PDA copolymer was thermally less stable than the TiO₂@PANI‐o‐PDA nanocomposites. The core–shell feature of the nanocomposites was found to have core and shell sizes of 17 nm and 19–26 nm, respectively. In addition, it was found that the addition of a high ratio of TiO₂ nanoparticles increases the electrical conductivity and consequently lowers the electrical resistivity of the TiO₂@PANI‐o‐PDA core–shell nanocomposites. The hybrid photocatalysts exhibit a dramatic photocatalytic efficacy of methylene blue degradation under solar light irradiation. A plausible interpretation of the photocatalytic degradation results of methylene blue is also demonstrated. Our setup introduces a facile, inexpensive, unique and efficient technique for developing new core–shell nanomaterials with various required functionalities and colloidal stabilities. © 2018 Society of Chemical Industry     

Microwave-Assisted Synthesis of Titania Nanocubes, Nanospheres and Nanorods for Photocatalytic Dye Degradation

TiO₂ nanostructures with fascinating morphologies like cubes, spheres, and rods were synthesized by a simple microwave irradiation technique. Tuning of different morphologies was achieved by changing the pH and the nature of the medium or the precipitating agent. As-synthesized titania nanostructures were characterized by X-ray diffraction (XRD), UV–visible spectroscopy, infrared spectroscopy (IR), BET surface area, photoluminescence (PL), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and atomic force microscopy (AFM) techniques. Photocatalytic dye degradation studies were conducted using methylene blue under ultraviolet light irradiation. Dye degradation ability for nanocubes was found to be superior to the spheres and the rods and can be attributed to the observed high surface area of nanocubes. As-synthesized titania nanostructures have shown higher photocatalytic activity than the commercial photocatalyst Degussa P25 TiO₂.     

Modified microwave method for the synthesis of visible light-responsive TiO2/MWCNTs nanocatalysts

Recently, TiO₂/multi-walled carbon nanotube (MWCNT) hybrid nanocatalysts have been a subject of high interest due to their excellent structures, large surface areas and peculiar optical properties, which enhance their photocatalytic performance. In this work, a modified microwave technique was used to rapidly synthesise a TiO₂/MWCNT nanocatalyst with a large surface area. X-ray powder diffraction, field-emission scanning electron microscopy, transmission electron microscopy and Brunauer-Emmett-Teller measurements were used to characterise the structure, morphology and the surface area of the sample. The photocatalytic activity of the hybrid nanocatalysts was evaluated through a comparison of the degradation of methylene blue dye under irradiation with ultraviolet and visible light. The results showed that the TiO₂/MWCNT hybrid nanocatalysts degraded 34.9% of the methylene blue (MB) under irradiation with ultraviolet light, whereas 96.3% of the MB was degraded under irradiation with visible light.