Morphology Of WO3 Research Articles

Hunting of “two birds with one arrow” strategical design of Nb doped WO3 decorated on the BN nanosheet and their enhanced photocatalytic degradation of Rose Bengal dye and Chloramphenicol drug

In the present work, “Killing two birds (RB and CAP) with one arrow (Nb/WO3/BN)” plan of action was performed for the photocatalytic degradation of organic dye of Rose Bengal (RB) and organic drug of Chloramphenicol (CAP) was degraded under visible light irradiation with the active catalyst of Nb/WO3/10 % BN composite for first time. The as-prepared Nb/WO3 was functionalized with thin-sheet structure of BN nanocomposite was synthesized via acid precipitation method followed by ultra-sonication method. The effective formation of Nb/WO3/BN were characterized by using XRD, UV-DRS, XPS, SEM-EDS, TEM, Photoluminescence (PL) and electrochemical impedance spectroscopy (EIS). The XRD, UV-DRS results clearly revealed that formation of ternary phases in the composites. Formation of ternary composite also confirmed by the XPS analysis. The morphology of WO3, Nb/WO3 and BN were examined by the SEM analysis. Furthermore, the inner morphology of cubic structure of WO3 nanoparticles and Nb/WO3 were decorated on the surface of the BN nanosheet were approved by TEM analysis. Interestingly, photocatalytic degradation of RB revealed by 94.31 % within 60 min as well as CAP degraded 95.13 % within 60 min by Nb/WO3/10 % BN ternary composite under visible light irradiation. Meanwhile, the different prepared photocatalyst, Nb/WO3/10 % BN was found to be the most efficient photocatalyst for degradation of RB and CAP. This results ascribed to the 30 mg of the photocatalyst and 10 mg/L concentration were optimum loading for the degradation of RB and CAP. Scavenger studies were also confirmed in order to understand the mechanism of photodegradation process. It was noted that electrons and holes pair are generated by irradiation of light, followed by (.OH) radical plays a crucial role for the photodegradation mechanism. The active photocatalyst Nb/WO3/10 % BN shows a good stability at room temperature and it can be recycled and reused up to five successful cycles without the major loss in their performances. Therefore, these work revealed that, the best sequence of Nb/WO3/10 % BN nanocomposite is new plan of action for photodegradation of RB and CAP.

Photocatalytic depolymerization of lignin to produce high value-added chemicals by carbon quantum dots modified WO3 nanosheets

Photocatalysis, a sustainable development strategy, employed to produce value-added chemicals from lignin, has attracted much attention due to its low energy consumption and mild reaction conditions. Carbon quantum dots (CQDs) and tungsten oxide (WO3) composite photocatalysts (CQDs/WO3) were prepared by ultrasonic assisted wet impregnation method in this study. The CQDs/WO3 nanosheets exhibit good optical properties and satisfactory performance of lignin depolymerization. Characterization results embody that the addition of CQDs significantly changes the morphology of WO3. Compared with bulk pure WO3, CQDs/WO3 becomes a nanosheet structure in the size of ∼ 200 nm. Furthermore, CQDs can absorb photogenerated electrons as well as reduce the recombination of photogenerated electrons and holes. The strong oxidizing ability of n-type semiconductor WO3 enables it to effectively break the typical bonds like C-O or C-C near polar functional groups in lignin. Due to this ingenious design, dealkaline lignin conversion was up to 34.21% as well as the highest yields of vanillin and vanillic acid in the form of lignin were 24.74 mg/g and 8.02 mg/g in 2 h at room temperature, visible light illumination and air atmosphere, respectively. And optimized CQDs/WO3 also had satisfactory effects on three natural lignin (grass lignin, pine lignin and birch lignin), which proved its universality. Electron spin resonance experiments and mechanism investigation demonstrated that ·O2- and ·OH play a weighty role in photocatalytic depolymerization of lignin. This study provides a new gambit for converting lignin to high value-added chemicals (vanillin and vanillic acid) over modified WO3.

Highly performed tungsten trioxide-polyaniline composite thin film and their accelerated oxygen evolution electrocatalyst activity

The low-cost and efficient catalyst for the oxygen evolution process is used in a variety of energy storage and conversion devices. In this work, a hydrothermal technique with only one step is used to incorporate a thin layer of WO3 onto PANI. When exposed to the oxygen evolution process in 1 M KOH solution, this film demonstrates excellent electrocatalytic activity and durability. Higher current densities for OERs of 50 mAcm-2 and 100 mAcm−2 are confirmed at overpotentials of 289 mV and 302 mV, respectively, with the enhanced WO3-PANI. To generate 10 mAcm−2, just 254 mV of overpotential is required. Low polarization resistance and swift kinetics through electrode–electrolyte contact are indicated by the WO3-PANI's low charge transfer resistance (Rct) value. The surface area expands as a result of PANI integration, increasing the number of exposed active spots for OER activity. It also shows excellent stability in a controlled electrolysis experiment for 24 h without a noticeable change in OER activity.WO3 and PANI are considered to be the main contributors to the extremely active and stable because of their combined abilities to decrease the adsorption energies of intermediates, induce lattice distortion into the crystalline morphology of WO3, and preserve a high lattice oxygen content. This study presents a simple synthetic technique to produce highly functional, affordable, and binder-free electrocatalysts.

Morphology-Controlled WO3 for the Photocatalytic Oxidation of Methane to Methanol in Mild Conditions

Since WO3 is a relatively abundant metal oxide and features the ability to absorb in the visible spectrum, this non-toxic semiconductor is a promising photocatalyst among sustainable materials. These properties have delivered intriguing catalytic results in the conversion of methane to methanol; however, initial investigations indicate low photocatalytic efficiency resulting from fast recombination of photogenerated charges. To explore this aspect of inefficiency, five different morphologies of WO3 consisting of micron, nanopowder, rods, wires, and flowers were obtained and characterized. In addition, several electron capture agents/oxidizers were investigated as a means of improving the separation of photogenerated charges. The photocatalytic activity of different morphologies was assessed via CH3OH formation rates. Based on our results, WO3 flowers produced the highest methanol productivity (38.17 ± 3.24 µmol/g-h) when 2 mM H2O2 was present, which is approximately four times higher in the absence of H2O2. This higher methanol production has been attributed to the unique structure-related properties of the flower-like structure. Photoluminescence emission spectra and diffuse reflectance data reveal that flower structures are highly catalytic due to their reduced electron/hole recombination and multiple light reflections via petal-like hollow chambers.

Mechanism of Tungsten Recovery from Spent Cemented Carbide by Molten Salt Electrodeposition

The accumulation of spent carbide (YG8), not only pollutes the environment but also causes waste of tungsten, cobalt and other rare metal resources. To better address this issue, we proposed a combined electrochemical separation process of low-temperature aqueous solution and high-temperature molten salt for tungsten and cobalt. H<sub>2</sub>WO<sub>4</sub> was obtained from spent carbide in an aqueous solution, and we calcined it to obtain WO<sub>3</sub>, which was used as a raw material to obtain tungsten by using molten salt electrodeposition. The influence of the current efficiency and the electrochemical behavior of the discharge precipitation of W(VI) were also studied. The calcination results showed that the morphology of WO<sub>3</sub> was regular and there were no other impurities. The maximum current efficiency of 82.91% was achieved in a series of electrodeposition experiments. According to XRD and SEM analysis, the recovered product was high purity tungsten, which belongs to the simple cubic crystal system. In the W(VI) reduction mechanism experiments, the electrochemical process of W(VI) in NaCl-Na<sub>2</sub>WO<sub>4</sub>-WO<sub>3</sub> molten salt was investigated using linear scanning voltammetry (LSV) and chronoamperometry in a three-electrode system. The LSV showed that W(VI) was reduced at the cathode in two steps and the electrode reaction was controlled by diffusion. The fitting results of chronoamperometry showed that the nucleation mechanism of W(VI) was an instantaneous nucleation mode, and the diffusion coefficient was 7.379×10<sup>−10</sup> cm<sup>2</sup>·s<sup>−1</sup>.

In-situ deposition of tungsten oxide hole-contact by Hot-Wire CVD and its application in dopant-free heterojunction solar cells

The tungsten oxide (WO x ) thin films have been deposited by a novel hot filament oxidation-sublimation process and applied in the dopant-free heterojunction solar cells as the hole selective contacts. The oxygen flow ratio plays a significant role during the deposition process. With increasing the oxygen flow ratio from 1.7% to 6.7%, the morphology of WO x films changes from small cauliflower-like particles to large cluster accumulation, and the ratio of W6+ increases from 76.1% to 91.4% with the ratio of W5+ decreasing from 23.9% to 8.6%. The work function of WO x can be tailored in a range of 5.5–6.1 eV by increasing the oxygen flow ratio. Its optical band gap maintains above 3.2 eV with the conductivity of about 10−5 S·cm−1. We have applied the WO x films in dopant-free silicon heterojunction solar cells as the hole selective contact layer by replacing the p-type amorphous silicon layer. By taking advantage of the highly transparent WO x layer, a high photon-current density of 39.6 mA·cm−2 was achieved with the oxygen flow ratio of 1.7%. It is interesting to find that the optimum cell conversion efficiencies of 14.9% were obtained with the oxygen flow ratio of 1.7% and the thickness of 10–20 nm for the deposition of WO x layer. This work proves the feasibility and good potential of Hot-Wire CVD prepared WO x hole selective contact for efficient dopant-free silicon heterojunction solar cells.

Influence of Mo+2 ion concentration on crystallization, microstructure, crystal imperfection and morphology of WO3 sprayed thin films

Compositional dependence of microstructure and morphological properties of MoxW1−xO3 (0.2 ≥ x ≥ 0.0 at. %) thin films was studied. MoWO3 films were deposited by chemical spray pyrolysis technique on pre-heated glass substrates at 400 °C and the sedimentation rate was kept constant at 70 ml min−1 with the deposition time fixed at 10 min to keep the film thickness constant at about 650 ± 5 nm. The prepared thin films were studied using x-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and energy dispersive x-ray analysis (EDAX) techniques. The nature of the as-deposited films displayed by XRD showed beyond a reasonable doubt that they are amorphous. After thermal annealing at 500 °C for 2 h, all samples will be transferred to a polycrystalline having a triclinic structure. The microstructural parameters of the pure and doped samples were measured, using different methods and a comparison between them to determine the accuracy percentage of the measurement of these methods. The results also showed that the average crystallite size of the films decreased from 24 to 12 nm, on the contrary the internal microstrain increased from 23 × 10−3 to 30 × 10−3 with the addition of Mo element in WO3. Field emission scanning electron microscopy (FE-SEM) analysis also revealed that Mo dopant caused significant changes in the surface morphology of the films as well as an increase in particle size with increasing molybdenum concentration. The EDX results exhibited that the percentages of the isotropic elements MoxW1−xO3 agree well with those determined by atomic weight. In general, the results obtained in this study confirm that MoxW1−xO3 with these properties, is suitable for photovoltaic and optoelectronic applications.

Solar-driven WO3·H2O/TiO2 heterojunction films immobilized onto bamboo biotemplate: Relationship between physical color, crystal structure, crystal morphology, and energy storage ability

In this study, different morphologies of WO3⋅H2O/TiO2 (WT) heterojunction films were successfully synthesized on bamboo biotemplate via facile two-step hydrothermal deposition methods. The WO3·H2O self-assembled by nanosheets or nanoplates on anatase TiO2-coated bamboo (TiO2-B) exhibited a distinctive surface color. The addition of WO3·H2O could significantly extend the optical responses of TiO2-B in the ultraviolet to the visible region. Based on the various analysis techniques, the formation mechanisms of the WO3·H2O hierarchical architectures with different crystal structures were also proposed. In addition, the photoactivity and post illumination activity of WT films were examined by constructing ·O2ˉ and ·OH in light and in light-off, respectively. The results showed that WT films with different crystal structures exhibited different photoactivity and energy storage abilities, and the photoactivity of WT films was negatively correlated with their energy storage ability. The presence of an anatase TiO2 thin film on the bamboo surface provided abundant active sites for WO3·H2O growth, which formed direct S-scheme heterojunctions for solar energy conversion and storage. Therefore, we anticipate that solar-driven energy storage heterojunctions with accessible and rich crystal morphologies will provide new insights for various applications, such as efficient wastewater treatment, self-cleaning coating, and air purification.

S, N Co-Doped Carbon Dot-Functionalized WO3 Nanostructures for NO2 and H2S Detection

This paper reports the synthesis of a S, N co-doped carbon dot (C-dot)-functionalized WO3 (C(S, N)-WO3) nanostructure via a hydrothermal method, which exhibits ultrasensitivity for NO2 at the ppb level and H2S at the ppm level along with remarkable selectivity. The WO3 morphology is optimized by varying the pH (1.5–3.5) of the solution. Characterization results reveal that the surface morphology at pH 3 is superior for producing uniform nanoneedle nanostructures with high sensitivity toward NO2 and H2S. To further enhance the sensitivity and selectivity of WO3 nanoneedles, the effect of mixing of C-dots into WO3 is investigated systematically. The optimized weight of C-dots in the C(S, N)-WO3 composite is 10 mg, which exhibits sensitivity values of 2.2 to 250 ppb for NO2 and 29.5 to 100 ppm for H2S. The C(S, N)-WO3 composite material shows the highest sensitivity at an optimum substrate temperature of 150 °C, without an obvious influence of humidity up to 50% relative humidity. The limit of detection of the composite sensor is 250 ppb NO2 along with excellent repeatability and good long-term stability.

Dimension dependency of tungsten oxide for efficient gas sensing

In this review, the impact of the structure dimensionality and surface morphologies of WO3 for efficient detection of gases such as H2, NH3, H2S, CO, O3, VOCs etc. along with the influence of surface functionalization and doping has been discussed.

Dewetted Silver Nanoparticle-Dispersed WO3 Heterojunction Nanostructures on Glass Fibers for Efficient Visible-Light-Active Photocatalysis by Magnetron Sputtering.

Fabrication of hybrid-heterojunction nanostructures comprising the Z-scheme and localized surface plasmon resonance is essential for enhancing the photocatalytic degradation of organic compounds to enable environmental remediation. This study focuses on the dispersion of dewetted Ag nanoparticles over the 3D network-like silica glass fibers (SGFs) coated with a Cu-doped WO3 heterojunction system by a high-throughput and cost-effective method using magnetron sputtering, followed by solid-state dewetting. The influence of Cu doping on the crystal structure, growth direction, and morphology of WO3 and the effect of localized surface diffusion-driven dewetted Ag nanoparticles on the photocatalytic performance were investigated. The Cu doping changed the optical band gap, and the 2Cu–WO3/SGF exhibited excellent photocatalytic activity. The surface dispersion of dewetted Ag nanoparticles over Cu–WO3/SGFs exhibited lowest photoluminescence intensity, indicating the effective separation of photogenerated electrons–holes, which led to highest efficiency (∼98%) in photocatalytic degradation of methylene blue among all the fibers with a degradation rate constant (k = 0.0205 min–1) that was ∼18.6 times higher than that of pure WO3 (k = 0.0011 min–1). The findings of this study can provide insights for designing low-cost and efficient visible-light-active photocatalysts for organic dye degradation, enabling environmental remediation.

Degradation of Methylene Blue with Layered Ni-Fe/WO3 Nanostructured, Composite Films Electrodeposited Onto Graphite

Dyes from textile companies, such as methylene blue (MB), stain water bodies and result in harmful environmental effects. They can also change the color of water bodies, which inhibits aquatic photosynthesis and lowers oxygen levels, compromising aquatic health. In order to treat dye contamination in water, several methodologies exist, including electrochemical oxidation with boron-doped diamond, TiRuO2 1 and Ti/Pt2 anodes. In the search for a lower cost anode material and thus a more cost-effective electrochemical oxidation process, a composite photoelectrocatalyst composed of tungsten trioxide, nickel-iron, and graphite was fabricated. Both decolorization and degradation of MB were examined in a chloride mediated electrolyte.Ni-Fe clusters were electrochemically deposited onto a graphite surface using recurrent galvanic pulses. WO3 was then electrochemically deposited through the generation of base method, potentiostatically. Cyclic voltammetry (CV) using an electrolyte containing 10 mM MB in 10 mM phosphate buffer saline and 100 mM potassium chloride at room temperature on screen-printed electrodes identified the region where the Ni-Fe/WO3 graphite composite catalyst resulted in a large anodic current, which included the oxidation of water, chlorine and organic. Electrolysis by chronoamperometry was implemented with and without light, in a single compartment electrochemical cell. The color change was measured using absorbance spectrophotometry. In order to confirm oxidation of total organic, COD measurements provided insight on whether the observed color change was caused by decomposition of MB at the working electrode or conversion to leucomethylene blue, at the counter electrode. Since Ni-Fe can oxidize under electrolysis conditions for MB degradation, the survivability of Ni-Fe underneath WO3 was inspected. Both scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) verified the presence of discrete Ni-Fe islands surrounded by WO3; after 16 hrs of electrolysis at 1.9 V vs Ag changes in the composition as well as the WO3 morphology was observed.Overall, with an increase in the electrolysis time there was a clear change in the electrolyte color. After 2 hours, the coloration of the MB solution dropped by 78% and after 16 hours, 89%. COD analysis confirmed the degradation of methylene blue by the Ni-Fe/WO3 graphite catalyst, and it was enhanced by 100 W/m2 UV light, with less conversion of methylene blue to leucomethylene blue, and an overall more efficient degradation. Acknowledgments: The authors thank The Center for Advanced Materials Processing at Clarkson University for use of their equipment and guidance provided by Hubert Bilan. This work was funded in part by NSF #20-508484 REU Site: Aquatic Sciences, Engineering, and Technology (ASET). Panizza, A. Barbucci, R. Ricotti, G. Cerisola, Separation and Purification Technology, 54 (2007) 382–387.Rodrigues de Oliveira, N. S. Fernandes, J. Vieira de Melo, D. Ribeiro da Silva, C. Urgeghe, C. A. Martínez-Huitle, Chemical Engineering Journal, 168 (2011) 208–214.

Evolution of intrinsic 1-3D WO3 nanostructures: Tailoring their phase structure and morphology for robust hydrogen evolution reaction

The use of non-noble electrocatalyst to harness molecular hydrogen by splitting water is highly appreciated. WO3 is one such high-caliber electrocatalyst for Hydrogen evolution reaction (HER) which can be tuned to attain various crystallographic phases and morphologies by altering the surfactants and synthesis parameters of hydrothermal synthesis. Seven different morphologies of WO3 ranging from 1 to 3D nanostructures were synthesized and subjected to HER under extreme pH conditions. The kinetic performance of 1D – nanorods of WO3 outperformed all its counterpart electrocatalysts with an exceptional Tafel slope of 96 and 105 mV dec−1 at pH = 0 and 14 respectively. The very high aspect ratio of WO3 nanorods in conjunction with an excellent specific surface area by precision tailoring of the crystallographic facets along the (0 0 1) direction enabled better adsorption energies necessary for HER. The nanorod structures of WO3 were further screened by Stainless steel (SS) and Carbon cloth (CC) substrates to determine their efficacy as a real-time electrode for hydrogen production. The nanorods deposited on CC in acidic media displayed an outstanding endurance of 12 h under a static overpotential of −0.5 V vs. RHE and a striking Tafel slope of 76 mV dec−1 comparable with standard Pt/C. The intrinsic interface of CC compared to SS along with the inherent complexity of WO3 nanorods has enriched the overall kinetic performance required for hydrogen evolution. This research has a promising scope for engineering the morphology and phase structure of WO3 metal oxide at the molecular level for boosting the interfacial active sites required for large scale production of hydrogen.

Porous nanoplate-like tungsten trioxide/reduced graphene oxide catalyst for sonocatalytic degradation and photocatalytic hydrogen production

A simple, cost-effective, ultrasound-assisted hydrothermal method was used to synthesize tungsten trioxide (WO3) and subsequently a tungsten trioxide/reduced graphene oxide (WO3/rGO) composite. The formation of the WO3/rGO composite was confirmed by XPS and Raman analyses. XPS analysis of the WO3/rGO composite revealed the presence of tungsten, carbon, and oxygen. Raman spectroscopy confirmed the presence of G and D bands in the WO3/rGO composite. The randomly arranged, interconnected, nanoplate-like morphology of WO3 was destroyed owing to the presence of rGO nanosheets and converted into a highly porous nanostructure. Multifunctional WO3 and WO3/rGO photocatalysts were used to study the sonocatalytic degradation of hazardous Congo red (CR) azo dye and photocatalytic hydrogen production. The surface area of the WO3/rGO composite (62.03 m2/g) was larger than that of WO3 (44.79 m2/g), thereby enhancing the efficiency of the sonocatalytic degradation and photocatalytic hydrogen production, which corresponds to the effective inter-charge transfer between WO3 and rGO. Platinum was used as a co-catalyst with WO3/rGO to promote hydrogen production. The incorporation of rGO enhanced the CR dye degradation efficiency from 56 to 94% and the hydrogen production activity from 424.5 to 825.8 µmol/h⋅g.

Different morphologies of WO3 and their exposed facets-dependent acetone sensing properties

Daisy-like hexagonal WO3 and rose-like monoclinic WO3 hierarchical structures were fabricated via facile hydrothermal technic in this work. The acetone sensing properties of the products were evaluated in detail. The results reveal that the hexagonal daisy-like WO3 sensor exhibits high sensitivity, good selectivity, rapid response/recovery, and remarkable repeatability to acetone (0.2∼200 ppm) at 260 °C. The outstanding sensing performance is attributed to the synergistic effects of the dominant (002) facets and the intracrystalline tunnel structure of hexagonal phase. The morphology formation mechanism and the acetone sensing mechanism are discussed. This work has practical significance for environmental monitoring of acetone as well as for breath diagnosis of diabetes.

Robust Z-scheme g-C3N4/WO3 heterojunction photocatalysts with morphology control of WO3 for efficient degradation of phenolic pollutants

Z-scheme g-C3N4/WO3 heterojunction photocatalysts with morphology control of WO3 are facilely fabricated via a thermal-induced self-polymerization of melamine in the presence of WO3 nanowires, nanosheets and microflowers, and they are successfully applied in simulated sunlight photocatalytic degradation of two refractory phenolic pollutants, p-nitrophenol and methylparaben. The g-C3N4/WO3 heterojunctions exhibit enhanced photocatalytic removal efficiency towards the target pollutants in comparison of pristine g-C3N4 and WO3; moreover, both the ratio and morphology of WO3 influence the photocatalytic activity of g-C3N4/WO3 dramatically. At the same ratio of WO3 in heterojunctions, g-C3N4/WO3 nanowires exhibit the highest pollutants removal efficiency among three heterojunction photocatalysts. By combination of testing results including photoelectronchemistry, photoluminescence and active species trapping it is confirmed that the unique Z-scheme band alignment of g-C3N4/WO3 heterojunctions plays the dominated role to the enhanced photocatalytic activity, which not only boosts the spatial separation of charge carriers but also endows the g-C3N4/WO3 with supreme redox capacity; additionally, intimate interfacial contact between WO3 and g-C3N4 in the heterojunctions can further promote this Z-scheme-dictated charge carrier transfer and separation. Under the attack of active species like hVB+, O2− and OH radicals, the target pollutants can be oxidized deeply to harmless inorganic compounds.

Design and fabrication of carbon dots decorated WO3 nanosheets hybrid photoanodes for sunlight-driven dye-sensitized solar cell applications

This work demonstrates the selection of the substrates to be used for photoanode and counter electrode for dye-sensitized solar cells (DSSC). A novel carbon dots (CDs) decorated WO3 nanosheets hybrid structure was synthesized by facile hydrothermal route, which acts as a photoanode materials: counter electrode (Pt) and iodide/triiodide (I−/I3−). Sun stimulator (AM 1.5G, 100 mW/cm2) is used as source of light to evaluate the photovoltaic characteristics. The samples using various mass ratios (1:1, 1:2, 1:3) of CDs and WO3 were prepared under the same conditions. The monoclinic structure with sheet-like morphology of WO3 was identified by XRD, Raman and TEM measurements. The optimized CDs/WO3 (1:3) photoanode exhibits a huge surface area (102.4 m2/g) and porous size (12 nm) since the CDs are rapidly anchored on the WO3 nanosheets. Due to the high absorption ability that prevents the recombination rate of the electron–hole pair, the optimized CDs/WO3 (1:3) photoanode delivers a high photoconversion efficiency of 11.7%, which is 3.35 times better than that of bare WO3 (3.5%). The improved photoconversion efficiency of WO3 by carbon was also discussed in detail.

Improving Photoelectrochemical Properties of Anodic WO3 Layers by Optimizing Electrosynthesis Conditions.

Although anodic tungsten oxide has attracted increasing attention in recent years, there is still a lack of detailed studies on the photoelectrochemical (PEC) properties of such kind of materials grown in different electrolytes under various sets of conditions. In addition, the morphology of photoanode is not a single factor responsible for its PEC performance. Therefore, the attempt was to correlate different anodizing conditions (especially electrolyte composition) with the surface morphology, oxide thickness, semiconducting, and photoelectrochemical properties of anodized oxide layers. As expected, the surface morphology of WO3 depends strongly on anodizing conditions. Annealing of as-synthesized tungsten oxide layers at 500 °C for 2 h leads to obtaining a monoclinic WO3 phase in all cases. From the Mott-Schottky analysis, it has been confirmed that all as prepared anodic oxide samples are n-type semiconductors. Band gap energy values estimated from incident photon−to−current efficiency (IPCE) measurements neither differ significantly for as−synthesized WO3 layers nor depend on anodizing conditions such as electrolyte composition, time and applied potential. Although the estimated band gaps are similar, photoelectrochemical properties are different because of many different reasons, including the layer morphology (homogeneity, porosity, pore size, active surface area), oxide layer thickness, and semiconducting properties of the material, which depend on the electrolyte composition used for anodization.

An Easy and Ecological Method of Obtaining Hydrated and Non-Crystalline WO3-x for Application in Supercapacitors.

In this work, we report the synthesis of hydrated and non-crystalline WO3 flakes (WO3−x) via an environmentally friendly and facile water-based strategy. This method is described, in the literature, as exfoliation, however, based on the results obtained, we cannot say unequivocally that we have obtained an exfoliated material. Nevertheless, the proposed modification procedure clearly affects the morphology of WO3 and leads to loss of crystallinity of the material. TEM techniques confirmed that the process leads to the formation of WO3 flakes of a few nanometers in thickness. X-ray diffractograms affirmed the poor crystallinity of the flakes, while spectroscopic methods showed that the materials after exfoliation were abundant with the surface groups. The thin film of hydrated and non-crystalline WO3 exhibits a seven times higher specific capacitance (Cs) in an aqueous electrolyte than bulk WO3 and shows an outstanding long-term cycling stability with a capacitance retention of 92% after 1000 chronopotentiometric cycles in the three-electrode system. In the two-electrode system, hydrated WO3−x shows a Cs of 122 F g−1 at a current density of 0.5 A g−1. The developed supercapacitor shows an energy density of 60 Whkg−1 and power density of 803 Wkg−1 with a decrease of 16% in Csp after 10,000 cycles. On the other hand, WO3−x is characterized by inferior properties as an anode material in lithium-ion batteries compared to bulk WO3. Lithium ions intercalate into a WO3 crystal framework and occupy trigonal cavity sites during the electrochemical polarization. If there is no regular layer structure, as in the case of the hydrated and non-crystalline WO3, the insertion of lithium ions between WO3 layers is not possible. Thus, in the case of a non-aqueous electrolyte, the specific capacity of the hydrated and non-crystalline WO3 electrode material is much lower in comparison with the specific capacity of the bulk WO3-based anode material.

Effect of the Morphology of Tungsten Oxide Embedded in Sodium Alginate/Polyvinylpyrrolidone Composite Beads on the Photocatalytic Degradation of Methylene Blue Dye Solution.

Tungsten oxide nanostructures were modified by oxygen vacancies through hydrothermal treatment. Both the crystalline structure and morphological appearance were completely changed. Spherical WO3·H2O was prepared from tungstic acid solution by aging at room temperature, while rod-like WO3·0.33H2O was prepared by hydrothermal treatment of tungstic acid solution at 120 °C. These structures embedded in sodium alginate (SA)/polyvinylpyrrolidone (PVP) were synthesized as novel porous beads by gelation method into calcium chloride solution. The performance of the prepared materials as photocatalysts is examined for methylene blue (MB) degradation in aqueous solutions. Different operation parameters affecting the dye degradation process, such as light intensity, illumination time, and photocatalyst dosage are investigated. Results revealed that the photocatalytic activity of novel nanocomposite changed with the change in WO3 morphology. Namely, the beads with rod nanostructure of WO3 have shown better effectiveness in MB removal than the beads containing WO3 in spherical form. The maximum degradation efficiency was found to be 98% for WO3 nanorods structure embedded beads, while the maximum removal of WO3 nanospheres structure embedded beads was 91%. The cycling-ability and reuse results recommend both prepared structures to be used as effective tools for treating MB dye-contaminated wastewaters. The results show that the novel SA/PVP/WO3 nanocomposite beads are eco-friendly nanocomposite materials that can be applied as photocatalysts for the degradation of cationic dyes in contaminated water.