WO3 Loading Research Articles

Rational construction of surface doping of Cu in WO3 nano platelets with Fe rich layer oxyhydroxide on the porous BiVO4 catalyst: A solar driven heterostructure photoanode for efficient water oxidation

The (Cu:WO3/BiVO4/FeOOH) photoanode heterostructure is a significant semiconductor for solar water splitting owing to its wide absorption of visible light photons. The bulk particles are experiencing charge recombination, which limits the PEC performance of the WO3 and BiVO4. Wherein, the heterostructure Cu:WO3/BiVO4/FeOOH catalysts have a staggered connection of band edges and morphological variation that outperforms the photoelectrochemical properties. The FeOOH layer on the surface of the PEC catalyst efficiently boosts water oxidation and quickens water splitting under light illumination. As anticipated, the doping in the WO3 and BiVO4 loading on the WO3 plates attains an outstanding increase in the water splitting performance. The 2% copper doping in the WO3 exhibits 1.2 mA/cm2, which is increasing by 40 cycles of coated BiVO4 to 2.0 mA/cm2. The FeOOH-grown heterostructure photoanode results in a higher overall photocurrent density (2.8 mA/cm2) at water oxidation potential. Moreover, the photoanode exhibits good stability and low resistance (385.7 Ohm/cm2). The photon-to-electron conversion efficiency has been attained at 1.2% at the applied potential of 0.4 V vs. RHE. These results from the photoanode could be a good candidate for high-performance PEC applications.

Synthesis of a novel biomass waste-based photocatalyst for degradation of high concentration organic pollutants under visible light: Optimization of synthesis condition and operational parameters via RSM-CCD

Reducing electron-hole pair recombination rate under visible light and preventing α-Fe2O3/WO3 nanoparticle aggregation enhances the photocatalytic efficiency. Herein, a novel heterojunction-activated carbon-based photocatalyst (α-Fe2O3/WO3/AC) was successfully synthesized from Rosa Canina seeds and characterized by PL, EIS, Photocurrent, ESR, XPS, LC-MS, FTIR, XRD, SEM, EDS-map, TEM, and BET analyses. Investigating the influence of significant parameters, including impregnation ratio (1–5), activation temperature (400–600 °C), and α-Fe2O3/WO3 loading (10–90 wt.%) by RSM method resulted in optimal photocatalyst synthesis (50 wt.%: FeW/AC3–500) evidenced by its capability for doxycycline degradation. The maximum doxycycline degradation (98.01 %) was achieved under optimal conditions with a degradation rate constant of 0.03 min−1. Trapping experiments revealed that •OH and •O2− played crucial roles in photocatalysis. The possible doxycycline degradation pathway of (50 wt.%: FeW/AC3–500) photocatalyst is proposed. Based on the transient photocurrent measurements and EIS results, the 50 wt.% FeW/AC3–500 composite exhibited a significant enhancement in photocatalytic activity, which can be attributed to the efficient speed of electron-hole separation. Overall, an innovative approach was introduced to design an efficient AC-based photocatalytic process, which enhances the performance of wastewater treatment and environmental remediation.

Effect of vanadium and tungsten loading order on the denitration performance of F-doped V2O5-WO3/TiO2 catalysts.

F-doped V2O5-WO3/TiO2 catalyst has been confirmed to have excellent denitration activity at low temperatures. Since the V2O5-WO3/TiO2 catalyst is a structure-sensitive catalyst, the loading order of V2O5 and WO3 may affect its denitration performance. In this paper, a series of F-doped V2O5-WO3/TiO2 catalysts with different V2O5 and WO3 loading orders were synthesized to investigate the effect of denitration performance at low temperatures. It was found that the loading orders led to significant gaps in denitration performance in the range of 120-240 °C. The results indicated loading WO3 first better utilized the oxygen vacancies on the TiF carrier promoting the generation of reduced vanadium species. In addition, loading WO3 first facilitated the dispersion of V2O5 thus enhanced the NH3 adsorption capacity of VWTiF. In situ DRIFT verified the rapid reaction between NO2, nitrate, and nitrite species and adsorbed NH3 over the VWTiF, confirming that the NH3 selective catalytic reduction (NH3-SCR) reaction over VWTiF at 240 °C proceeded by the Langmuir-Hinshelwood (L-H) mechanism. This research established the constitutive relationship between the loading order of V2O5 and WO3 and the denitration performance of the F-doped VWTi catalyst providing insights into the catalyst design process.

The Green Preparation of Mesoporous WO3/SiO2 and Its Application in Oxidative Desulfurization

Recently, supported WO3-based catalysts have been widely used in oxidative desulfurization (ODS) due to their advantages of easy separation, high activity, and being environment-friendly. In this work, supported mesoporous WO3/SiO2 catalysts have been prepared using an incipient-wetness impregnation method with agricultural waste rice husks as both a silicon source and mesoporous template, and phosphotungstic acid as a tungsten source. The effects of different calcination temperatures and WO3 loadings on the ODS performance of samples are studied, and the appropriate calcination temperature and WO3 loading are 923 K and 15.0 wt.%, respectively. The relevant characterization results show that, compared with pure WO3, the specific surface area and mesopore volume of WO3/SiO2 samples are greatly increased. Due to (a) high WO3 loading, (b) high specific surface area, and (c) nanoscale WO3 grains uniformly dispersed on the surface of the mesoporous SiO2 carrier, active sites of WO3/SiO2 catalysts are greatly increased, and their catalytic activities are improved. After the sixth and eighth runs in the ODS of dibenzothiophene and 4,6-dimethyldibenzothiophene, respectively, the WO3/SiO2 catalyst still maintains high catalytic activity (>99.0%) despite the presence of a partial loss of WO3. In addition, with the aid of the UV-Vis technique, the tungsten-peroxo species, the active intermediates in the ODS reaction catalyzed by the WO3/SiO2 catalyst, are captured. Finally, a possible mechanism for the ODS of bulky organic sulfides using the WO3/SiO2 catalyst is proposed.

Effects of WO3 and MoO3 loadings on vanadia-based catalysts for NH3-SCR: Revealed by in situ infrared and two-dimensional correlation spectroscopy

Vanadia-based catalysts have been widely applied in NOx reduction, while the promoting effects of WO3 and MoO3 are still under debate. Herein, we prepared V2O5/TiO2, V2O5-WO3/TiO2, and V2O5-MoO3/TiO2 catalysts and revealed that WO3 and MoO3 enhanced the activity of V2O5/TiO2, especially under wet conditions. In situ DRIFTS, two-dimensional correlation spectroscopy (2D COS), and DFT calculations demonstrated that NH3 adsorbed on Lewis acid sites of V2O5/TiO2, resulting in the formation of NH3ads-L1 (1284 cm−1, Ti sites of O=V–O–Ti) and NH3ads-L2 (1604 cm−1, V=O sites). By using 2D COS, we found that the NH3ads-L1 exhibited higher reactivity towards NO to produce NH2NO* via NH2*, which was promoted by WO3. Moreover, WO3 and MoO3 doping inhibited H2O adsorption, and promoted its desorption by increasing temperature, thus protecting the V=O sites on V2O5/TiO2. Also, 2D COS provided a new perspective for in-depth understanding of the active sites and intermediates in the NH3-SCR reaction.

ZnO-based heterojunction catalysts for the photocatalytic degradation of methyl orange dye

In this study, a variety of ZnO-based heterojunctions with disparate wt.% doping of WO3 and BiOI have been prepared for the photodestruction of methyl orange (MO) dye in aqueous solution. The composites were analysed by scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, optical studies, and nitrogen adsorption-desorption isotherms. The SEM images revealed non-uniform surfaces of the ZnO–BiOI based composites while mostly nodular morphology was observed for all three samples of ZnO-WO3. As the WO3 loading increased, more clustering was detected. The analysed samples exhibited characteristic peaks representative of the triclinic phase of WO3 and the hexagonal wurtzite structure of ZnO, while the diffractogram observed from the materials displayed distinct peaks corresponding to the crystalline phases of both BiOI and ZnO in their pure forms. Further evidence of the samples' characteristics includes the presence of distinct crystalline patterns without any impurity peaks, a red shift in the absorption spectra of the heterostructure, the detection of only the reference elements, and mostly Type IV isotherm adsorption. This study identified the ZnO-[10%]BiOI and ZnO-[10%]WO3 heterojunctions as the best performing photocatalysts, as MO was completely destroyed in 120 and 90 min, respectively. Thus, confirming 10% wt. as the optimal doping concentration for the best photo-activity in this study. The impact of varying process parameters demonstrates that at an elevated photocatalyst mass of 40 mg, both heterojunctions effectively degraded MO. The photodegradation efficiency of MO was more pronounced in strong acidic conditions (pH 2) when compared to high alkaline conditions (pH 11) for the ZnO-[10%]BiOI heterostructure. However, a decrease in performance was observed for both strong acidic and high alkaline pH values when the ZnO-[10%]WO3 heterostructure was applied. The kinetic analysis of the photodegradation study reveals that all the photodegradation experiments can be represented by the pseudo-first-order kinetic model. The findings from this investigation propose that the ZnO-[10%]BiOI heterojunction photocatalyst holds significant potential for the effective treatment of dye-contaminated wastewater.

Structural, mechanical, and thermal features of PVA/starch/graphene oxide nanocomposite enriched with WO3 as gamma–ray radiation shielding materials for medical applications

AbstractPolyvinyl alcohol (PVA)/starch/graphene oxide nanocomposites containing different ratios of tungsten oxide (WO3) were prepared for use in the medical field as low‐cost, facile, eco‐friendly, and biodegradable low‐energy γ‐ray shielding materials. The effect of different WO3 loading (0, 2, 4, 8, and 12 wt%) on nanocomposites' structural, mechanical, and gamma attenuation properties was studied. X‐ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscope verified the incorporation of WO3 into the nanocomposite matrix. The thermal stability and activation energy of the decomposition of nanocomposites showed continuous improvement with increasing WO3. The maximum tensile strength and elongation of nanocomposites were achieved by incorporating 4 wt% WO3 compared to the lowest tensile strength and elongation at 8 and 12 wt% of WO3, respectively. The good filler distribution inside the polymeric matrix at lower filler loading compared to the creation of voids and agglomeration at higher filler levels explains this behavior. It was found that nanocomposites' calculated mass attenuation coefficient μm (cm2/g) increased with increasing WO3 at different photon energies. Half‐value layer (HVL) and tenth‐value layer (TVL) values fall as WO3 concentration rises. The sample with 12 wt% of WO3 exhibits lower HVL and TVL values and higher μm, demonstrating a more remarkable gamma attenuation ability. Such results endorsed the prepared nanocomposites as low energy γ‐rays attenuation materials in medical fields.Highlights PVA/starch/graphene oxide nanocomposites with different WO3s were fabricated as shielding materials. The impact of WO3 on nanocomposites' mechanical and shielding characteristics was studied Thermal stability of nanocomposites showed continuous improvement with increasing WO3 μm increased with continuously increasing WO3 at different photon energies.

Tungsten trioxide-modified zeolite-based catalysts in the esterification of lactic acid: the effect of Si/Al ratio and WO3 loadings

Tungsten trioxide-modified zeolite-based catalysts in the esterification of lactic acid: the effect of Si/Al ratio and WO3 loadings

Chemical Looping Dry Reforming of Methane over Ni-Modified WO3/ZrO2: Cooperative Work of Dispersed Tungstate Species and Ni over the ZrO2 Surface

In this study, we successfully developed nickel (Ni)-modified tungstate zirconia (Ni/WO3/ZrO2) as an effective material for chemical looping dry reforming of methane (CL-DRM) under isothermal conditions (750 °C). The performance of Ni/WO3/ZrO2 strongly depended on the WO3 loading amount. The optimal amount of 10.0 wt% WO3, corresponding to low surface W density (<4 W atoms/nm2), in Ni/WO3(10)/ZrO2 resulted in the exclusive formation of dispersed tungstate species, such as isolated monotungstate and/or oligomeric polytungstate species. Increasing the loading amount to 30.0 wt% (higher surface W density (>4 W atoms/nm2)) resulted in the formation of crystalline WO3 species, diminishing the CL-DRM performance over Ni/WO3/ZrO2. Comprehensive characterization, including in situ/operando W L3-/L1-, Ni K-, and Zr K-edge X-ray absorption spectroscopy studies, revealed that surface dispersed tungstate species were reduced by CH4 to yield CO and H2, and low-valent W species assignable to W0 to W3+. The low-valent W species were reoxidized by CO2 to produce CO and regenerate the original W6+ species. These active tungstate species cooperatively work with Ni over ZrO2 surface to promote partial CH4 oxidation, leading to efficient CL-DRM.

Selective Hydrogenolysis of Biodiesel Waste Bioglycerol Over Titanium Phosphate (TiP) Catalysts: The Effect of Pt & WO3 Loadings

Glycerol is an important by-product (biowaste) from biodiesel production. Transformation of glycerol into value-added compounds is critical in improving the overall efficiency of the biodiesel production. In this work, a sustainable and cleaner production of 1,3-propanediol (1,3-PDO) by vapor phase hydrogenolysis of glycerol was performed over titanium phosphate (TiP) supported catalysts by varying the Pt and WO3 loadings (5–20 wt.%). The WO3 promoted Pt modified TiP catalysts were prepared by a simple wet impregnation method and characterized by various analytical techniques in determining the key properties. Furthermore, the catalyst activity and stability were studied under different reaction conditions. The synergistic effects of Pt and WO3 loadings on the final performance of the catalyst has been significant in improving the hydrogen transfer rate. Both Pt and WO3 promotional effects is envisaged the enhanced catalytic properties in conjunction with TiP support acidity. WO3 incorporation increased Brønsted acidity and formed strong interactions with Pt over TiP support. Both Lewis and Brønsted acid sites presented but BAS played a key role in enhancing the 1,3-PDO selectivity in a bifunctional dehydration-hydrogenation reaction mechanism of glycerol. The effect of reaction temperature, contact times and the weight hour space velocity were evaluated. Overall, under optimized reaction conditions, 2 wt.% Pt-10 wt.% WO3/TiP catalyst displayed superior activity with a maximum glycerol conversion of ~ 85% and ~ 51% of 1,3-PDO selectivity achieved at time on stream of 4 h.Graphical

Synergistic effect of F doping and WO3 loading on electrocatalytic oxygen evolution

Electrochemical oxygen evolution reaction (OER) is an important anodic semi-reaction for energy storage and conversion. In this work, Perfluorooctanoic acid (PFOA), an aqueous pollutant, is degraded into F-containing fragments and captured to prepare ultrasmall WO3 decorated F-doped graphite sheets (WO3@F-GS) via a plasma-induced assembly method. WO3@F0.1-GS achieves a low overpotential of 298 mV and Tafel slope of 77.6 mV dec-1, as low as that of RuO2. Meanwhile, WO3@F0.1-GS exhibits good stability in both OER and overall water splitting in 1 M KOH. The synergistic effect of WO3 and F enhances the electrocatalytic performance. Density functional theory calculations prove W4+ coordinates with F-doping resulting in enhanced adsorption of OH– and decreased energy barrier of OH deprotonation, leading good activity. The steric hindrance of F and WO3 loading hinder the stacking of graphitic layers and improve the stability. This work not only provides a mild synthesis strategy of F-doping, but also provides a novel reutilization approach for fluoride waste.

Chemically bonded tungsten-based polymer composite for X-rays shielding applications

Lead-free metal-polymer composite based X-ray shielding apparel has been of great concern in recent years due to its flexibility, less toxicity, lightweight, etc. The conventional metal-polymer composites based apparels suffers from non-uniform attenuation due to the non-uniform distribution of fillers in the polymer matrix. In this work, efforts were made to address this drawback by developing a chemically bonded metal-polymer composite by incorporating tungsten trioxide (WO3) solution in the blend of polyvinyl alcohol and polyvinyl pyrrolidone. Developed composites were characterized and their X-ray attenuation properties were determined using the X-ray tube voltage of 50–140 kV. The XRD and SEM analyses revealed the formation of the sodium tungstate (Na2WO4.2H2O) phase and its uniform distribution in the polymer matrix, respectively. FT-IR and XPS data showed the formation of a coordinate bond between the W and polymer matrix, which is responsible for the uniform distribution of W-based filler. The polymer composite made with 17 % of WO3 loading is found to be optimum. The 2.35 mm thick sample possesses the attenuation equivalent to 0.25 mm lead at 100 kV, which is recommended by IAEA (International Atomic Energy Agency) to fabricate radiation shielding aprons to attenuate scattered X-rays. The developed composite shows a tensile strength of 4.6 MPa, which is suitable for fabricating wearable radiation shields.

The interplay between acid-base properties and Fermi level pinning of a nano dispersed tungsten oxide - titania catalytic system

A series of WO3/TiO2 catalysts were synthesized, characterized, and evaluated for the NO selective catalytic reduction (SCR) with NH3. Based on a wide range of characterization techniques, a detailed model was developed that describes the interfacial electron transfer between WO3 and TiO2 and defines a relationship between the acid-base properties of the catalytic surface and electronic structure modification. The electronic interactions at the WO3/TiO2 interface were quantified using variations in the system's electronic structure. Altering the dispersion and size of the WO3 nanostructures results to drastic changes in titania's surface electron distribution, which are reflected in the pinning of Fermi level through an electron transfer process between WO3 and TiO2. The variations in the Fermi level were further related to changes in the point of zero charge (PZC) values and the activity towards NO SCR with NH3, which was used as a test reaction. Temperature Programmed Surface Reaction (TPSR) was employed to study the catalytic activity at temperatures ranging from 30 °C to 500 °C and was quantitatively correlated to changes in coverage and interfacial charge transfer. We demonstrate that higher WO3 loading on TiO2 results in a stronger electronic interaction and a higher catalytic activity. This is because electron transfer increases the surface electron density, which enhances the surface basicity of TiO2. The concomitant decrease in the adsorption energy of NH3 results in a decrease in the activation energy, which is reflected in the SCR temperature onset.

The effects of WO3 addition to NiO/ZrO2 oxygen carriers for chemical looping combustion of methane

Chemical looping combustion (CLC) is a promising combustion technology with inherent CO2 capture at low energy penalty. The success of CLC relies heavily on the development of an appropriate oxygen carrier. Mixed metal oxide supported oxygen carriers have been widely used to alleviate some of the disadvantages of monometallic based oxygen carriers. In this study, the effects of introducing WO3 into NiO/ZrO2 oxygen carriers were investigated for methane CLC using different synthesis methods and varying oxygen carriers’ compositions. Several characterization techniques such as ICP-OES, N2 adsorption-desorption, XRD, SEM/EDS, H2-TPR, and XPS have been used to understand the effects of preparation method, and oxygen carrier composition on methane CLC. The dual NiO-WO3/ZrO2 oxygen carriers exhibited enhanced oxygen capacity and lower carbon formation compared to their NiO/ZrO2 monometallic counterpart. Introduction of WO3 into NiO/ZrO2 lattice structure led to formation of an intermediate phase (NiWO4) which enhanced oxygen carriers’ reducibility and improved metal dispersion. This was mainly due to the high valence number of W6+ which created oxygen vacancy in the OC lattice structure due to charge balance difference. Coprecipitation and impregnation methods have been used to synthesize dual OCs, and impregnation method exhibited superior performance in terms of cyclic stability and coking resistance. Using impregnation synthesis method, WO3 and NiO loadings were optimized based on oxygen capacity and coke formation under cyclic redox experiments. Amongst the tested samples for methane CLC, NiO(60%)-WO3(25%)/ZrO2 showed the optimum performance with 15.6% oxygen carrying capacity and no carbon formation.

Photoelectrochemical properties of WO3-modified anatase TiO2 photoanodes and application for dye-sensitized solar cells

TiO2 electrodes were modified with different WO3 loadings and photoelectrochemical characterization revealed an increase in photocurrent density and decrease in interface charge transfer resistance with increasing amount of WO3. A decrease in green PL was observed with WO3 addition indicating more mobility of charges and therefore less probability of recombination. A series of TiO2 photoanodes modified by WO3 were designed with different geometrical configurations for dye-sensitized solar cell (DSSC) applications, WO3 was introduced successively in the screen-printed paste, as an undercoat and in the TiCl4 pretreatment bath. The results indicated a decrease in photovoltaic performance of all devices modified by WO3 compared to TiO2 reference cell. The highest conversion efficiency of the modified cells was observed for the configuration of WO3 introduced into the TiCl4 pretreatment bath. In this case, the optimized contact between the coupled semiconductors improved the charge transfer, also the direct contact of WO3 with the FTO substrate decreased the loss of electrons by confinement and recombination.

A three-dimensional nano-network WO3/F-TiO2-{001} heterojunction constructed with OH-TiOF2 as the precursor and its efficient degradation of methylene blue.

In this study, three-dimensional nested WO3/F-TiO2-{001} photocatalysts with different WO3 loadings were prepared by a hydrothermal process and used to degrade methylene blue (MB). The photocatalysts with various ratios of WO3 to OH-TiOF2 can be transformed into a three-dimensional network WO3/F-TiO2 hetero-structure with {001} surface exposure. The results showed that the composite catalyst with 5% WO3, denoted as FWT5, had the best comprehensive degradation effect. FWT5 has a limited band gap of 2.9 eV, which can be used as an advanced photocatalyst to respond to sunlight and degrade MB. The average pore diameter of the composite catalyst is 10.3 nm, and the multi-point specific surface area is 56 m2 g−1. Compared with pure TiOF2, the average pore size of the composite catalyst decreased by 8.44 nm and the specific surface area increased by 51.2 m2 g−1, which provides a larger contact space for the catalytic components and pollutants. Moreover, TiO2 on the {001} surface has higher photocatalytic activity and methylene blue can be better degraded. Under the irradiation of 0.03 g FWT5 composite catalyst with a simulated solar light source for 2 h, the degradation rate of 10 mg L−1 methylene blue can reach 82.9%. The trapping experiment showed that photo-generated holes were the principal functional component of WO3/F-TiO2-{001} photo-catalysis, which could capture OH− and form hydroxyl radical (˙OH) and improved the photocatalytic degradation performance. Kinetic studies show that the photocatalytic degradation of MB fits with the quasi-first order kinetic model.

WO3–SiO2 nanomaterials synthesized using a novel template-free method in supercritical CO2 as heterogeneous catalysts for epoxidation with H2O2

A series of tungsten oxide-silica (WO3–SiO2) composite nanomaterials were synthesized through a novel, template-free sol-gel method, in which supercritical-CO2 (scCO2) was utilized as synthesis medium. The efficacy of the synthesis method stems from a tailored reactor design that allows the contact of the reactants only in the presence of scCO2. Selected synthetic parameters were screened with the purpose of enhancing the performance of the resulting materials as heterogeneous catalysts in epoxidation reactions with H2O2 as environmentally friendly oxidant. A cyclooctene conversion of 73% with epoxide selectivity of > 99% was achieved over the best WO3–SiO2 catalyst under mild reaction conditions (80 °C), equimolar H2O2 amount (1:1) and low WO3 loading (~2.5 wt%). The turnover number achieved with this catalyst (TON = 328), is significantly higher than that of a WO3–SiO2 prepared via a similar sol-gel route but without supercritical CO2, and that of commercial WO3. A thorough characterization with a combination of techniques (ICP-OES, N2-physisorption, XRD, TEM, STEM-EDX, SEM-EDX, FT-IR and Raman spectroscopy, XPS, TGA and FT-IR analysis of adsorbed pyridine) allowed correlating the physicochemical properties of the WO3–SiO2 nanomaterials with their catalytic performance. The high catalytic activity was attributed to: (i) the very high surface area (892 m2/g) and (ii) good dispersion of the W species acting as Lewis acid sites, which were both brought about by the synthesis in supercritical CO2, and (iii) the relatively low hydrophilicity, which was tuned by optimizing the tetramethyl orthosilicate concentration and the amount of basic solution used in the synthesis of the materials. Our optimum catalyst was also tested in the reaction of cyclohexene with H2O2, resulting in cyclohexane diol as main product due to the presence of strong Brønsted acid sites in the catalyst, whereas the reaction with limonene yielded the internal epoxide as the major product and the corresponding diol as side product. Importantly, the catalyst did not show leaching and could be reused in five consecutive runs without any decrease in activity.

Preparation of WO3-modified TiO2 thin film by peroxo sol–gel method and its photocatalytic activity in degradation of methylene blue

A series of WO3-modified TiO2 sols with various WO3 contents were synthesized by peroxo sol–gel method using H2O2 as the agent. The as-synthesized WO3-TiO2 sols were light yellow in color. The maximum amount of WO3 which could be incorporated into the TiO2 sol was 4 wt.%. The pH values of the as-prepared sols were near neutral. These sols were very stable even after 2 years in stock. The sols were used to coat on glass substrate. The XRD patterns and the SAED patterns indicated that the phase of TiO2 was anatase. There were no characteristic XRD peaks of WO3 in the WO3-modified TiO2 sol, possibly due to low WO3 loading. The particles were rhombus shaped with the major axis and minor axis of 30–77 nm and 15–31 nm, respectively. WO3 was incorporated into the surface structure of TiO2 and modified the electronic state of Ti. The film coated onto glass substrate was very uniform, and the film thickness was ~ 160 nm. The XPS results exhibited that W existed as 5 + and 6 + oxidation states and Ti existed in Ti3+ and Ti4+. These four chemical states play a role of gathering the photogenerated holes and capturing the photogenerated electrons in the lower conduction band of WO3, respectively. This can effectively enhance the separation rate of photogenerated electron–hole pairs and increase the photoactivity. WO3/TiO2 samples had high photocatalytic activity under UV light illumination to degrade methylene blue, because it had high OH and O2− group contents.

Highly active and durable WO3/Al2O3 catalysts for gas-phase dehydration of polyols.

Gas-phase glycerol dehydration over WO3/Al2O3 catalysts was investigated. WO3 loading on γ-Al2O3 significantly affected the yield of acrolein and the catalyst with 20 wt% WO3 loading showed the highest activity. The WO3/Al2O3 catalyst with 20 wt% WO3 loading showed higher activity and durability than the other supported WO3 catalysts and zeolites. The number of Brønsted acid sites and mesopores of the WO3/Al2O3 catalyst did not decrease after the reaction, suggesting that glycerol has continuous access to Brønsted acid sites inside the mesopores of WO3/Al2O3, thereby sustaining a high rate of formation of acrolein. Dehydration under O2 flow further increased the durability of the WO3/Al2O3 catalyst, enabling the sustainable formation of acrolein. In addition, the WO3/Al2O3 catalyst with 20 wt% WO3 loading showed high activity for the dehydration of various polyols to afford the corresponding products in high yield.

Highly active WO3@anatase-SiO2 aerogel for solar-light-driven phenanthrene degradation: Mechanism insight and toxicity assessment

The global energy crisis and water pollution drive the researchers to develop highly effective and less energy intensive water purification technologies. In this study, a highly active WO3@TiO2–SiO2 nanocomposite was synthesized and used for photocatalytic degradation of persistent organic pollutants under simulated solar light. The optimum WO3@TiO2–SiO2 prepared with 2 wt% WO3 loading and calcination at 800 °C exhibited higher photocatalytic activity, as the rate constant (k1) for phenanthrene degradation was ∼7.1 times of that for the commercial TiO2 (P25). The extremely large specific surface area (>400 m2/g) of WO3@TiO2–SiO2 afforded it with enlarged pollutants adsorption performance and abundant active surface sites. The heterojunction of anatase with SiO2 as well as loading of WO3 decreased the band gap energy (Eg) of TiO2, which extended the utilization spectrum of TiO2 to visible region. Formation of Ti–O–Si band indicated the excess charges can cause Brønsted acidity due to the absorption of protons to compensate the charges. Moreover, the migration of photo-excited electrons from the conduction band of anatase to WO3 and holes in the opposite direction restrained the electron-hole recombination. The photocatalytic degradation mechanism and pathway for phenanthrene degradation were proposed based on experimental analysis and density functional theory (DFT) calculation, and the toxicities of the degradation intermediates were evaluated by quantitative structure–activity relationship (QSAR) analysis. WO3@TiO2–SiO2 also showed good separation (settling) performance and high stability. Our work is expected to offer new insight into the photocatalytic mechanism for WO3, TiO2 and SiO2 based heterojunctions, and rational design and synthesis of highly efficient photocatalysts for environmental application.