WO3 Photocatalyst Research Articles

Preparation of 2D WO3 nanomaterials and their catalytic performance during the synthesis of imines under visible light irradiation

Abstract In this work, 2D WO3 photocatalysts were successfully prepared by a hydrothermal method with different methods, different pH values and different calcination temperatures. The morphology, crystal structure, composition, and chemical properties of the as-prepared samples were systematically investigated by multiple techniques (XRD, XPS, SEM, TEM, UV–vis DRS, BET, and PL). Imines were synthesized from aniline and benzyl alcohol over WO3 under visible light irradiation. The catalysts and reaction conditions were optimized. The results showed that the catalytic performance of WO3 (hydrochloric acid method, pH=1, and calcination temperature=400 °C) was the best. The conversion reached 75.9 %. After five cycles, the catalyst performance was stable and the morphology did not change. Analysis of the active species showed that the amination reaction was mainly realized by the synergistic action between h+ and OH. Visible light irradiation can lower the activation energy of the amination reaction. A possible reaction mechanism was proposed.

Ionic liquid-assisted synthesis of a novel PANI/ZnWO4/WO3 ternary nanocomposite: a facile double electron transfer photocatalyst for efficient degradation of a herbicide

A ternary PANI–ZnWO4–WO3 photocatalyst was synthesized via IL-assisted in situ polymerization method exhibiting double Z-scheme channelization towards photodegradation of glyphosate with superior minimization of toxicity of degraded products.

Tuning the redox potential of Ag@Ag2O/WO3 and Ag@Ag2S/WO3 photocatalysts toward diclofenac oxidation and nitrophenol reduction

WO3 nanoplates modified with either Ag2O or Ag2S nano-architectures were synthesized by a deposition-hydrothermal route (180 °C for 5 h). They were characterized using X-ray powder diffraction, N2 sorptiometry, Transmission electron microscopy, UV–vis diffuse reflectance spectroscopy, Photoluminescence spectroscopy, and X-ray photoelectron spectroscopy. The photo-catalytic (λ > 420 nm, 160 W) degradation of Diclofenac (DCF; 60 mg/l), was achieved using H2O2 (1 × 10−4 M) with either Ag@Ag2O/WO3 (K = 32.0 × 10-3 min-1) or Ag@Ag2S/WO3 (K = 7.3 × 10-3 min-1) catalysts. In the case of DCF degradation using radical scavengers, O2− played a key role in the degradation process whilst OH and holes acted moderately minor roles. The possible DCF degradation paths and intermediates were assessed by LC–MS. Both Ag@Ag2O/WO3 and Ag@Ag2S/WO3 catalysts were used in the photo-reduction of 4-nitrophenol (4-NP; 1.8 × 10−4 M) to 4-aminophenol (4-AP) with rate constants equal 8.3 x 10−3 min-1 and 1.6 x 10−3 min−1, respectively.

Reduced graphene oxide as a solid-state mediator in TiO2/In0.5WO3 S-scheme photocatalyst for hydrogen production

Photocatalytic H2 evolution has been proven to be one of the promising methods for tackling global energy and environmental issues. In this work, rGO supported TiO2/In0.5WO3 S-scheme heterojunction photocatalyst was prepared by using the hydrothermal and wet impregnation methods. The crystallinity and morphology of synthesized photocatalysts were ascertained by XRD, FESEM, and TEM. The results showed high crystallinity and distribution of TiO2/In0.5WO3 on rGO sheets. The photocatalytic activity of synthesized photocatalyst was evaluated towards photocatalytic H2 production. It was noted that compared to bare TiO2 (24.15 ± 1.8 μmol/h/g), TiO2/In0.5WO3 (132.6 ± 5.1 μmol/h/g) and rGO supported TiO2/In0.5WO3 (309.98 ± 11.4 μmol/h/g) photocatalysts showed ~ 5 and ~ 12 folds enhanced photocatalytic H2 production activity. Further, 5.2, 11.3 and 15.6% AQE was achieved at 365 nm for TiO2, TiO2/In0.5WO3 and rGO supported TiO2/In0.5WO3. This was mainly attributed to improved light absorption by TiO2/In0.5WO3 and rapid charge carrier separation characteristics of rGO as revealed by UV–vis DRS, Photoluminescence spectroscopy and Photocurrent studies. Based on photoelectrochemical results, a direct S-scheme heterojunction charge transfer mechanism was proposed to explain the significantly enhanced photocatalytic performance of rGO supported TiO2/In0.5WO3 photocatalyst. This work stipulates new comprehensions into the construction of S-scheme heterostructure through rGO as a solid-state mediator.

Photoactive Tungsten-Oxide Nanomaterials for Water-Splitting.

This review focuses on tungsten oxide (WO3) and its nanocomposites as photoactive nanomaterials for photoelectrochemical cell (PEC) applications since it possesses exceptional properties such as photostability, high electron mobility (~12 cm2 V−1 s−1) and a long hole-diffusion length (~150 nm). Although WO3 has demonstrated oxygen-evolution capability in PEC, further increase of its PEC efficiency is limited by high recombination rate of photogenerated electron/hole carriers and slow charge transfer at the liquid–solid interface. To further increase the PEC efficiency of the WO3 photocatalyst, designing WO3 nanocomposites via surface–interface engineering and doping would be a great strategy to enhance the PEC performance via improving charge separation. This review starts with the basic principle of water-splitting and physical chemistry properties of WO3, that extends to various strategies to produce binary/ternary nanocomposites for PEC, particulate photocatalysts, Z-schemes and tandem-cell applications. The effect of PEC crystalline structure and nanomorphologies on efficiency are included. For both binary and ternary WO3 nanocomposite systems, the PEC performance under different conditions—including synthesis approaches, various electrolytes, morphologies and applied bias—are summarized. At the end of the review, a conclusion and outlook section concluded the WO3 photocatalyst-based system with an overview of WO3 and their nanocomposites for photocatalytic applications and provided the readers with potential research directions.

Palm oil mill effluent treatment using tungsten trioxide: Adsorption and photocatalytic degradation

Abstract Today, some of the major disadvantages of conventional palm oil mill effluent (POME) treatment are that the process is time consuming, as well as space consuming. Besides, most of the recent photocatalyst still have a limitation that able to demonstrate their good performances only under sources of light. The visible-light-driven energy storage photocatalyst, which is tungsten trioxide (WO3), has been developed to overcome the limitations mentioned. Therefore, the present study aims to investigate the comparative calcination temperature and the degradation of POME using WO3 as a photocatalyst in adsorption and photocatalytic processes under visible light irradiation. An eco-friendly WO3 photocatalyst was synthesized by coprecipitation method. Subsequently, the resulting WO3 was characterized by Fourier-transform infrared spectroscopy (FTIR) to evaluate the significance of calcination temperature towards WO3. Furthermore, the adsorption activity of WO3 towards POME was investigated at different sources of ponds (cooling, anaerobic and aeration) throughout 300 min. This study reports on the efficiency of adsorption activity of WO3-400 °C towards pond aeration pollution, which showed that it was better than that in anaerobic and cooling ponds based on the chosen study criteria of color and suspended solid removal for the investigation of photocatalytic activity. Moreover, WO3 was proven to be able to conserve energy, where it was demonstrated that POME can still degrade consistently in darkness, with the highest color removal of approximately 48% was obtained. An extraordinary photocatalytic treatment with WO3 functioning simultaneously as the light harvesting and energy storage material is deemed as an efficient photocatalyst for POME in terms of decolorization and removal of suspended solid.

Photocatalytic degradation of ciprofloxacin and sulfamethoxazole on a carbon nanodot doped tungsten trioxide: degradation product study

This work is focused on the photocatalytic degradation of antibiotics ciprofloxacin and sulfamethoxazole in wastewater using a nanocomposite of tungsten trioxide (WO3) and carbon nanodots (CNDs). This material was prepared by doping tungsten trioxide (WO3) with carbon nanodots (CNDs) by hydrothermal technique. The structural, optical, morphological and photocatalytic properties of the CNDs-doped WO3 nanocomposite as well as an undoped WO3 nanorod were successfully characterized by TEM, XRD, Raman, FTIR, BET and UV–Vis DRS. The photocatalytic degradation performance, degradation kinetics and degradation patterns were followed by UV–Visible spectroscopy and ultra performance liquid chromatography coupled with mass spectrometry (UPLC-MS). The percentage removal of ciprofloxacin and sulfamethoxazole were higher with the WO3-CNDs than the pristine WO3 photocatalyst denoting the positive effect of doping. The percentage removal of the antibiotics when monitored by UPLC-MS was found to be higher than that of UV–Visible spectroscopy. The intermediate products and pathway were different with the doped and the undoped WO3 photocatalysts.

Dual channel construction of WO3 photocatalysts by solution plasma for the persulfate-enhanced photodegradation of bisphenol A

A facile solution plasma method was used to activate the surface reactivity of photocatalysts. Take WO3 as an example, we found that reductive hydrogen radicals from electrical discharge were highly energetic and favored the formation of oxygen vacancies, whereas synergistic effect between these defects and plasma-activated water created abundant bridging hydroxyls via surface hydroxylation. When used for the removal of BPA pollutants, synergistic oxidation exhibited 6 and 12 times higher reaction rates than the individual persulfate oxidation and photodegradation, respectively. Surface activation of WO3 photocatalysts contributed to the 4-fold increase of the catalytic activity. Mechanism study demonstrated that oxygen vacancies and hydrated bridging hydroxyls provided unique channels for electron and hole extraction. The enhanced generation of oxidative species was responsible for the significantly increased photoactivity for bisphenol A (BPA) degradation. This work provides a versatile and universal strategy for the active site engineering of catalysts.

Eu2+- and Nd3+-Doped CaAl2O4/WO3/polyester nanocomposite as a sunlight-activated photocatalyst for fast removal of dyes from industrial wastes

In this work, a reusable, sunlight-activated and environmentally friendly photocatalyst for fast removal of dye pollutants from industrial wastes was developed based on the synergistic effect among phosphorescent CaAl2O4:Eu2+:Nd3+ nanoparticles, WO3 photocatalyst and polyester resin. The emitted light by the phosphorescent CaAl2O4:Eu2+: Nd3+ nanoparticles is absorbed by the WO3 photocatalyst, and hence, the population of the excited WO3 particles is increased and their photocatalytic activity is significantly enhanced. The role of the polyester resin is to keep the CaAl2O4:Eu2+:Nd3+ nanoparticles and WO3 particles in the vicinity of each other and stabilize them on the surface of the glass plate via formation the transparent and robust polymer layer. Stabilization of the particles overcomes the recovering problems of the dispersed photocatalyst particles used in the traditional batch and continues systems. Thus, the proposed strategy has the potential to be applied for removal of dye pollutants from industrial wastes in the large scale. The chemical structure and dispersion quality of the synthesized nanocomposite photocatalyst were studied using FT-IR spectroscopy, XRD analysis, FE-SEM imaging and EDX analysis. The affecting variables on the photocatalytic activity of the proposed system were optimized. The rate constant of the photocatalysis degradation of methylene blue was calculated to be 0.113 min−1. Under sunlight, the synthesized nanocomposite photocatalyst is able to completely remove methylene blue from industrial wastes in less than 30 min.

Mechanistic Insights into Visible Light-Induced Direct Hydroxylation of Benzene to Phenol with Air and Water over Pt-Modified WO3 Photocatalyst

Activation of C(sp2)-H in aromatic molecules such as benzene is one of the challenging reactions. The tungsten trioxide supported Pt nanoparticles (Pt-WO3) exhibited hydroxylation of benzene in the presence of air and H2O under visible-light (420 < λ < 540 nm) irradiation. The photocatalytic activities (yields and selectivity of phenol) were studied under several experimental conditions. Furthermore, investigations of mechanistic insight into hydroxylation of benzene have been carried out by analyses with apparent quantum yields (AQY), an H218O isotope-labeling experiment, kinetic isotope effects (KIE), electrochemical measurements and density functional theory (DFT) calculations. It was proposed that dissociation of the O–H bond in H2O is the rate-determining step. Furthermore, the substitution of the OH derived from H2O with H abstracted from benzene by photo-formed H2O2 indicated a mechanism involving a push-pull process for the hydroxylation of benzene into phenol.

Copper(ІІ)-doped WO3 nanoparticles with visible light photocatalytic antibacterial activity against gram-positive and gram-negative bacteria

Simple impregnation technique was used to modify the surface of tungsten (VI) oxide (WO3) with Cu(II) nanoclusters at molar fraction 1, 3, and 5% mol. Cu(ІІ)–WO3 photo catalysts were studied by, UV-visible light spectra, and FTIR measurements were carried out, respectively. UV–vis reflectance method of Cu(ІІ)–WO3 nanoparticles display that the optical absorption was in the visible region of approximately 2.7 eV; this also assure the combination of Cu ions in the lattice of WO3 crystal. AFM images showed homogeneous distribution of copper in the matrix of WO3. Two bacterial pathogens, gram-positive Staphylococcus aureus and gram-negative Escherichia coli, were lighted for 180 and 240 min with Cu(ІІ)–WO3 nanoparticles for photocatalytic inactivation. This displays a fundamental diminution in number of bacteria. The survival number of all bacteria species is not influenced in dark with nanoparticles and in light condition without nanoparticles.

Porous g-C3N4/WO3 photocatalyst prepared by simple calcination for efficient hydrogen generation under visible light

A novel porous g-C3N4/WO3 photocatalyst was successfully obtained by adopting urea and WO3⋅0.33H2O as precursor by a simple hydrothermal and calcination method. The structural characteristics, photoelectric properties, and hydrogen generation efficiency of g-C3N4/WO3 were studied. The results shows that best photocatalytic hydrogen generation efficiency of the g-C3N4/WO3 was 963 μmol−1 h−1, it was about 3 times than pure g-C3N4. Hydrated tungsten oxide promotes the formation of porous structure after removing crystal water, and the increased pore volume and pore size provide more reactive activity sites, which contribute to increase the efficiency of hydrogen generation. The mechanism of photocatalytic hydrogen generation was proposed.

Water-Dispersible Triplet-Triplet Annihilation Photon Upconversion Particle: Molecules Integrated in Hydrophobized Two-Dimensional Interlayer Space of Montmorillonite and Their Application for Photocatalysis in the Aqueous Phase.

Green incident light (λ = ∼500 nm) is converted to blue light (λ = 400-450 nm) in air using bulky alkylammonium (DMDOA+), 9,10-diphenylanthracene (DPA), and Ru(dmb)32+ (dmb = 4,4'-dimethyl-2,2'-bipyridine) intercalated in a layered clay compound called "montmorillonite" [MMT-DMDOA+-DPA-Ru(dmb)32+]. The two-dimensional interstitial space has an interlayer spacing of a few nanometers. Emitter DPA is present in this interlayer spacing, having an intermolecular distance of approximately 3.0 nm at a high concentration. Sensitizer Ru(dmb)32+ is relatively dilute, having an intermolecular distance of 47 nm. The emission decay measurements and quantitative evaluation of the emission intensity demonstrate that blue light emission is induced by sequential processes, which consist of a triplet-triplet (T-T) energy transfer reaction from Ru(dmb)32+ to DPA and T-T annihilation of DPA molecules. From thermogravimetry and Fourier transform infrared spectra measurements, we observe that the cointercalated alkylammonium acts as a waterproof agent to prevent quenching of the molecules in the excited triplet states by H2O. Finally, we demonstrate a photocatalytic decomposition of Rhodamine B dissolved in H2O-containing MMT-DMDOA+-DPA-Ru(dmb)32+ and Pt-deposited WO3 photocatalyst, where wavelength of incident light (λ > 440 nm) is longer than the absorption edge of WO3 photocatalyst. The mechanism of photocatalytic decomposition is the following: (i) the incident long wavelength light is upconverted to 400-450 nm light by MMT-DMDOA+-DPA-Ru(dmb)32+, and then, (ii) WO3 photocatalyst is excited by the generated 400-450 nm light, and finally, (iii) Rhodamine B is decomposed on the Pt cocatalyst induced by the holes in a valence band of WO3.

Fixed Z-scheme TiO2|Ti|WO3 composite film as recyclable and reusable photocatalyst for highly effective hydrogen production

The recycling and reusing of photocatalysts are vital to large-scale hydrogen production. In this work, for this purpose, a novel fixed Z-scheme TiO2|Ti|WO3 photocatalyst composite film is prepared. TiO2 and WO3 films are supported on both sides of a Ti foil by corrosion-calcination and sol-gel spin coating methods, respectively. To evaluate the activity of fixed Z-scheme TiO2|Ti|WO3 photocatalyst composite film, the photocatalytic hydrogen production is carried out in aqueous solution containing methanol. Some influence factors such as Ti foil corrosion times, WO3 layer number and Ti foil thickness are considered. The results show that the fixed Z-scheme TiO2|Ti|WO3 photocatalyst composite film has a superior photocatalytic performance toward hydrogen production. Under solar light irradiation for 4.0 h, the fixed Z-scheme TiO2|Ti|WO3 photocatalyst composite film gives a 473.2 μmol hydrogen evolution amount, which is much higher than 232.1 μmol of TiO2|Ti film and 25.8 μmol of WO3|Ti film. It is attributed to that Ti foil as conductive channel accelerates e− transfer and restrains e− and h+ recombination. At the same time, Ti foil as carrier can fix TiO2 and WO3 films on its two sides, providing a cyclic utilization way and large-scale hydrogen production possibility. Perhaps, the fixed TiO2|Ti|WO3 composite film will be a promising Z-scheme photocatalyst utilizing solar energy for large-scale hydrogen production.

SrAl2O4:Eu2+: Dy3+/ WO3/ polyester nanocomposite as a highly efficient and environmentally friendly photocatalyst for removal of dyes from industrial wastes

The novel, reusable and highly efficient nanocomposite photocatalyst was synthesized from WO3 particles, SrAl2O4:Eu2+: Dy3+ nanoparticles and polyester resin. The structure of the synthesized nanocomposite and the distribution of the ingredients were investigated by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) analysis, field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), thermal gravimetric analysis (TGA) and energy dispersive X-ray (EDX) analysis. The long lasting phosphorescent SrAl2O4:Eu2+:Dy3+ nanoparticles act as nano-lamps for excitation of WO3 particles. Thus, this synergistic effect can significantly enhance the photocatalytic activity of the WO3 photocatalyst. In fact, 5 min illumination by three 1-Watt LED emitters at wavelength of 400 nm produces sufficient energy for 12 h phosphorescence emission by the SrAl2O4:Eu2+: Dy3+ nanoparticles, and hence, excitation of WO3 photocatalyst. Reusability, low energy consumption, stability, simple recovery from solution, high catalytic efficiency an environmentally friendly ingredients are the most important advantages of the proposed SrAl2O4:Eu2+: Dy3+/ WO3/ polyester nanocomposite luminescent photocatalyst. The proposed nanocomposite was able to photocataliticaly remove up to 99 % of methylene blue from industrial wastes in less than 90 min.

Enhanced photocatalytic performance of m-WO3 and m-Fe-doped WO3 cuboids synthesized via sol-gel approach using egg albumen as a solvent

The monoclinic-WO3 and Fe-doped WO3 powders were successfully obtained at 800 °C synthesized via sol-gel approach using fresh egg albumen as one solvent to provide a matrix for entrapment of W(VI) ions to acquire gel form. The obtained nano-particles were characterized via powder x-ray diffractometry (XRD), x-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HR-TEM), brunauer-emmett teller (BET), uv–vis spectroscopy (UV), photoluminescence spectroscopy (PL) and fourier transform infrared spectroscopy (FTIR). The efficiencies of catalysts for de-colorization of organic pollutants were investigated on methylene blue (MB) dye. The results reveal that 5% Fe-doped WO3 photo-catalyst shows best photocatalytic performance under visible light irradiation (~95% in 120 min) with a rate constant(~0.0227 min−1). The enhanced photocatalytic activity of 5% Fe-doped WO3 is due to its high crystallinity, large BET surface area (~30.26 m2/g), nano-porous architecture (pore diameter ~ 1.76 nm), low PL emission intensity, visible light absorbing band gap (~2.39 eV), high rate of electron-hole pairs generation and suppressed recombination of photo-generated charges.

Nitrogen doped carbon quantum dots and GO modified WO3 nanosheets combination as an effective visible photo catalyst

Nitrogen doped carbon quantum dots (NCQDs) based highly efficient ternary photocatalyst are fabricated by modifying surface of GO incorporated WO3 nano-sheets. XRD confirmed the formation of monoclinicWO3 nano-sheets. All the characteristic peaks of WO3, GO and NCQDs are obvious in XRD patterns of WO3/GO/NCQDs ternary photocatalysts confirming successful fabrication of the photocatalysts. SEM images showed that WO3 host matrix is distorted after incorporation of GO and NCQDs owing to lower interfacial tension. The surface of WO3 nano-sheets is modified with morphological defects making more active sites available. UV–vis spectra exhibited extended visible light absorption and remarkable reduction of WO3 band gap energy. The photoluminescence spectra confirmed the efficient charge separation in NCQDs modified ternary photocatalyst. The synthesized composites were applied for the photocatalytic degradation of harmful organic dye i.e. methyl orange (MO). The ternary composites represented the excellent photocatalytic activity as compared to binary and pure WO3 photocatalysts. This enhanced photocatalytic activity is attributed to the availability of active sites, extended light absorption in visible region and enhanced charge separation efficiency.

Engineering the performance of heterogeneous WO3/fullerene@Ni3B/Ni(OH)2 Photocatalysts for Hydrogen Generation

The hydrogen production through solar water splitting could be eco-friendly, environmental-benign and sustainable, alternative to fossil fuels energy carriers. In this work, the novel heterojunction WO3/fullerene/Ni3B/Ni(OH)2 composites were successfully fabricated through different methods. The Ni3B/Ni(OH)2 as a needle like nanostructures were integrated into the interfaces between WO3 and fullerene. The structural phase and morphology of prepared nanomaterials were significantly modified by incorporating the Ni3B/Ni(OH)2 as a co-catalyst. The results demonstrated that dopant element serves as the conductive electron bridges, rather than general cocatalyst, to accumulate electrons and inspire the H2 generation kinetics over pure WO3 photocatalyst. The significantly improved hydrogen rate of evolution up to 1578 μmol h−1 g−1 was found for hybrid photocatalyst [WO3/fullerene@ 1.5% Ni3B/Ni(OH)2] which was 9.6 times higher as compared to pure photocatalyst. The interfacial contact between co-catalyst and composite could play substantial role in effective separation and transference of charge-carriers for improved hydrogen evolution rate. Under the visible light illumination, the heterojunction nanostructures inspire rapid transfer of electrons from WO3 towards Ni3B/Ni(OH)2 to inhibit the fast recombination rate and prolong the WO3 charge-carrier's lifetime, thereby releasing more electrons with greater reducing power for hydrogen production. This work may open an avenue for the strategy and green preparation of robust photocatalysts for scalable applications in solar H2 evolution and sustainable environment.

The self-assembly and formation mechanism of regenerated cellulose films for photocatalytic degradation of C.I. Reactive Blue 19

In this paper, a simple method has been developed to fabricate flexible fiber materials with excellent visible light response. Firstly, polydopamine (PDA) layer was deposited on the cotton fibers to functionize cotton fibers. Then, a uniformly dense layer of silver and tungsten trioxide nanoparticles was obtained on cotton fabric by reduction of PDA. The deposition of PDA provided a media for the Ag–WO3 photocatalyst to be loaded with good adhension. The results showed that the prepared cotton (C)-PDA–Ag–WO3(c) composite photocatalytic material exhibited excellent photocatalytic performance with 98% degradation efficiency of RB-19 dye solution within 180 min under visible light irradiation. Moreover, the degradation rate constants were 52.43 ×, 35.73 ×, 12.01 × and 3.77 × higher than those of raw cotton, C-PDA, C-PDA-Ag and C-PDA-Ag–WO3(a), respectively. The free radical trapping experiments showed that h+, ·OH and ·O2− were important active species in the photocatalytic process. Based on the characterizations of the system, the possible photocatalytic reaction mechanism of the C-PDA-Ag–WO3(c) composite photocatalytic material was proposed. This paper provided a new perspective for the preparation of high catalytic performance visible light responsive flexible fiber materials applied in the degradation of dye wastewater.

Investigation of the kinetics and mechanism of Z-scheme Ag3PO4/WO3 p–n junction photocatalysts with enhanced removal efficiency for RhB

The activity of an Ag3PO4/polyhedron-like WO3 photocatalyst could be enhanced 27 times compared to P25 in the visible light-driven region towards RhB.