Monoclinic WO3 Phase Research Articles

Thermomechanical and Structural Analysis of WO3 Array for Optimized Photoelectrochemical Chloride Oxidation Performance.

Understanding the crystal structure of WO3 is essential for optimizing its photoelectrochemical performance. This study comprehensively analyzes the structural characteristics of WO3 during synthesis and investigates their correlation with photoelectrochemical activity. Structural analysis, incorporating annealing procedure and WO3 thickness, identifies a blend of hexagonal, monoclinic, and orthorhombic phases within WO3 array. Specifically, detailed analysis reveals a predominance of monoclinic WO3 phase alongside the orthorhombic WO3 phase, both of which are commonly characterized by their monoclinic structure. Three-dimensional thermomechanical simulations using the finite element method reveal that thermal displacement in WO3 layers increases with thickness during the thermally induced synthesis process. These results highlight a direct correlation between WO3 thickness, thermal displacement, and phase transition, with thicker layers favoring the transformation from orthorhombic to monoclinic structures due to increased thermally induced deformation. The heightened monoclinic structure, which possesses lower symmetry than the orthorhombic structure, induces more defect sites, suggesting increased donor density. Notably, the monoclinic-dominated WO3 exhibits superior performance under UV-visible irradiation in 0.5 M NaCl. Furthermore, the WO3 array demonstrates over 85% Faradaic efficiency for chloride oxidation, indicating preferential selectivity over oxygen evolution reaction in 0.5 M NaCl. This study emphasizes the pivotal role of the crystal structure of WO3 in achieving efficient photoelectrochemical seawater splitting.

Synergic effect of rare earth doped Sm doped WO3 nanoparticles for enhanced MB dye photocatalytic activities of waste water treatment and antibacterial activities against Staphylococcusaureus

One of the most effective ways to reduce environmental pollution on the earth's surface is the catalytic decomposition method. In this paper, the co-precipitation method was successfully used to synthesize pure and Sm (3, 5, and 7 wt%) doped WO3 nanoparticles by various weight percentage. The structural and optical properties of prepared NPs were characterized using XRD, SEM, EDS, HR-TEM, XPS, FTIR and UV–Vis. From XRD analysis confirmed the monoclinic phase of WO3 as well as the substitutional incorporation of Sm in WO3 lattice. The surface morphology of the obtained samples was studied by SEM and HR-TEM, which shows nanoplate morphology. EDS and XPS analysis element confirmation for W, O and Sm. The systematic decrease of bandgap (Eg) from 2.86 to 2.82 eV with increasing Sm doping concentration from 0 to 7 wt% was strong evidenced from UV–Vis analysis. Furthermore, the extensive surface area of the active CV curves and EIS indicating the good to improve photocatalytic performance and photo-generated carriers' separation efficiency. The photodegradation of Methyl Blue (MB) aqueous solution in 120 min under the visible light irradiation is used to assess the photocatalytic activity of the prepared samples. Among the four samples, 7 wt% doped one shows higher degradation efficiency of 94.2 %. Finally, the antibacterial properties of Sm:WO3 (0, 3, 5 and 7 wt%) NPs against Staphylococcusaureus (MTCC 8708) were investigated with the disc diffusion method and zone of inhibition in mm were recorded. Based on the above analysis, the superior antibacterial activity against Staphylococcusaureus (18 mm) is rather obtained with Sm:WO3 (7 wt%) sample.

Amine functionalized graphene oxide decorated with ZnO-WO3 nanocomposites for remediation of organic dye from wastewater

Photocatalytic degradation is as an efficient technique to eradicate toxic chemical pollutants from contaminated water sources. However, the selectivity and photocatalytic activity are the challenging targets to explore the new photocatalysts. Therefore, our research goal is to develop a suitable photocatalyst to satisfy the recent photocatalytic degradation demand. In this work, amine functionalized graphene oxide (NH2-GO) supported heterojunction ternary novel nanocomposites (NH2-GO/ZnO-WO3) were prepared via simple solvothermal method. Structural and morphological investigations of the prepared composites are systematically observed by Field Emission Scanning Electron Spectroscopy (FE-SEM), X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR), and Ultraviolet–Visible (UV–vis) Spectroscopy. FT-IR analysis confirmed the effective functionalization of amine on graphene oxide. The XRD results indicated that the prepared nanocomposites were free from any impurities and the binary composite (NH2-GO/ZnO) showed hexagonal wurtzite structure, whereas the ternary composite (NH2-GO/ZnO-WO3) exhibited mix crystal structure of monoclinic and hexagonal phase of WO3 and ZnO, respectively. The synthesized ternary photocatalyst (NH2-GO/ZnO-WO3) demonstrated superior photocatalytic efficiency towards various organic dyes such as cationic dye methylene blue (MB, 85.89%) and anionic dye methyl orange (MO, 60.98%) compared to binary photocatalyst (NH2-GO/ZnO) that showed only 52.28% of MB and 25.8% of MO dye degradation under UV light irradiation. The enhanced photocatalytic performance was mainly due to the low recombination rate of photogenerated electron-hole pair, narrow band gap, and large surface area of ternary composite. The presence of lone pair electrons in amino group provides a negative-charged surface composite resulting good interaction with cationic dye is the key to upgrade the photocatalytic performance. The ternary nanocomposite NH2-GO/ZnO-WO3 has the capacity to be a competent and acceptable photocatalyst for the photodegradation of organic dyes used in industries.

Asymmetric supercapacitor performance of hydrothermally-synthesized MWCNT-WO3 composite electrode

Supercapacitors are energy storage devices that have the potential to significantly contribute to meeting energy demands in the modern era. However, the charge storage capacity and stability of pseudocapacitive materials should be improved. To improve the electrode storage capacity, tungsten trioxide (WO3) has been synthesized and deposited on multi-walled carbon nanotubes (MWCNT-WO3) on stainless-steel substrates via hydrothermal technique. The structural, morphological, elemental, and compositional studies on WO3 and MWCNT-WO3 samples were done with X-ray diffractometry (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDX), Fourier transform Infrared Spectroscopy (FTIR), contact angle, and Brunauer-Emmett-Teller (BET). The electrochemical features of the WO3 and MWCNT-WO3 materials were studied for supercapacitor application using a three-electrode set-up. The results obtained show highly crystalline films with porous nanoplates at the surface and monoclinic WO3 phase. The basic elemental constituents and chemical bonds present in the synthesized samples were confirmed using EDX and FTIR spectra. The MWCNT-WO3 exhibited an optimized capacitive behavior when compared to WO3. A specific capacitance of 818.31 Fg−1 was obtained at a scan rate of 5 mVs−1 in 0.5 M H2SO4 electrolyte. The composite MWCNT-WO3 was further used as an electrode in a solid-state asymmetric supercapacitor, PANI||MWCNT-WO3 fabricated with polyaniline (PANI) and MWCNT-WO3 as positive and negative electrodes in polyvinyl alcohol/sulphuric acid (PVA/H2SO4) gel electrolyte. The fabricated materials exhibited excellent electrochemical performance which makes them useful for supercapacitor applications.

Comparison study of WO3 thin film and nanorods for smart window applications

The WO3 thin films were deposited at oxygen partial pressure of 8x10-4 mbar. A template-free straightforward hydrothermal method is employed to produce vertical alignment hierarchical WO3 nano-architectures on clear conducting substrates (3x2.5 cm2 in size and slides resistance 4 O). After being deposited at ambient temperature, the samples were air annealed at 400 °C for 4 h. The optical, electrochromic, surface and structural morphology behavior of the deposited material after annealing were studied using XRD, Raman, FTIR, SEM, electrochemical analyzer and UV–Visible spectrometer characterization methods. After annealing at 400 °C for 4 h in air, every characteristic peak are matched to a monoclinic (crystalline) WO3 phase. The Nano flower array achieved a considerable coloration efficiency (24.09 cm2/s) and low cathodic peak current (−2.03 mA) compare to the Tungsten trioxide thin film produced by the DC magnetron sputtering method. The vertically oriented geometry and the porosity space between the Nano flower, which improve H+ diffusion and provide a considerable contact area for charge-transfer processes, are primarily responsible for the improved electrochromic properties.

Tailoring the Emission Behavior of WO3 Thin Films by Eu3+ Ions for Light-Emitting Applications

The article reports the successful fabrication of Eu3+-doped WO3 thin films via the radio-frequency magnetron sputtering (RFMS) technique. To our knowledge, this is the first study showing the tunable visible emission (blue to bluish red) from a WO3:Eu3+ thin film system using RFMS. X-ray diffractograms revealed that the crystalline nature of these thin films increased upto 3 wt% of the Eu3+ concentration. The diffraction peaks in the crystalline films are matched well with the monoclinic crystalline phase of WO3, but for all the films', micro-Raman spectra detected bands related to WO3 monoclinic phase. Vibrational and surface studies reveal the amorphous/semi-crystalline behavior of the 10 wt% Eu3+-doped sample. Valence state determination shows the trivalent state of Eu ions in doped films. In the 400-900 nm regions, the fabricated thin films show an average optical transparency of ~51-85%. Moreover, the band gap energy gradually reduces from 2.95 to 2.49 eV, with an enhancement of the Eu3+-doping content. The doped films, except the one at a higher doping concentration (10 wt%), show unique emissions of Eu3+ ions, besides the band edge emission of WO3. With an enhancement of the Eu3+ content, the concentration quenching process of the Eu3+ ions' emission intensities is visible. The variation in CIE chromaticity coordinates suggest that the overall emission color can be altered from blue to bluish red by changing the Eu3+ ion concentration.

Nanocomposite based hydroelectric cells: Working principle and production of green electrical energy

Hydroelectric cells were prepared to produce the electricity through the splitting of water molecules into hydronium and hydroxide ions at room temperature. Hydroelectric cells of WO3 loaded SnO2 nanocomposite produce electricity without emission of any toxic gas or by-products. The structural, morphological and hydroelectric properties of the nanocomposites were analyzed by using powder X-ray diffraction, Scanning Electron Microscope, Fourier Transform Infra-red Spectra. Adsorption-desorption isothermal curves, pore size distribution and pore volume were investigated by using Barrett‐Joyner‐Halenda technique. Ionic diffusion of the dissociated H3O+ and OH– ions have been investigated by dielectric and dc conductivity measurements of all the samples in dry and wet states. Powder X-ray Diffraction pattern validates the biphasic composite having monoclinic WO3 phase and tetragonal SnO2 phase. Surface chemical analysis and oxygen defect study were investigated using X-ray photoelectron spectrum. The uniform grain distribution along with well crystalline morphology was observed by SEM micrographs. Circular cells of WO3 loaded SnO2 nanocomposite samples of 2-inch diameter have been prepared to investigate the hydroelectric properties. The fabricated HEC of 19.63 cm2 area of 10 wt% WO3 loaded SnO2 nanocomposite delivers maximum short circuit current, open-circuit voltage and off-load output power as 655 mA, 0.959 V, 628 mW, respectively. Output power exhibited by WO3 - SnO2 nanocomposite based Hydroelectric Cell is considerable and has appeared as a feasible green energy source.

High performance and remarkable cyclic stability of a nanostructured RGO-CNT-WO3 supercapacitor electrode.

One of the most pressing concerns in today's power networks is ensuring that consumers (both home and industrial) have access to efficient and long-lasting economic energy. Due to improved power accessibility and high specific capacitance without deterioration over long working times, supercapacitor-based energy storage systems can be a viable solution to this problem. So, here, tungsten trioxide (WO3) nanocomposites containing reduced graphene oxide and carbon nanotubes i.e. (RGO-WO3), (CNT-WO3), and (RGO–CNT-WO3), as well as pure WO3 nanostructures as electrode materials, were synthesized using a simple hydrothermal process. The monoclinic phase of WO3 with high diffraction peaks is visible in X-ray diffraction analysis, indicating good crystallinity of all electrode materials. Nanoflowers of WO3 were well-decorated on the RGO/CNTs conductive network in SEM micrographs. In a three-electrode system, the specific capacitance of the RGO–CNT-WO3 electrode is 691.38 F g−1 at 5 mV s−1 and 633.3 F g−1 at 2 A g−1, which is significantly higher than that of pure WO3 and other binary electrodes. Furthermore, at 2 A g−1, it achieves a coulombic efficiency of 98.4%. After 5000 cycles, RGO–CNT-WO3 retains 89.09% of its capacitance at 1000 mV s−1, indicating a promising rate capability and good cycling stability performance.

Influence of integrated nitrogen functionalities in nitrogen doped graphene modified WO3 functional visible photocatalyst

Nitrogen doped graphene modified WO3 nanocomposites were synthesized through an effective methodology. The prepared photocatalysts were employed as active candidates for degradation of highly toxic organics i.e., 2, 4 dichloro phenol (2, 4-DCP) and methyl orange (MO). XRD profile of N-graphene showed complete reduction of GO into N-graphene. All diffraction peaks of WO3 along with N-graphene indicated monoclinic phase of WO3. SEM and TEM images of 3.0% N-graphene/WO3 have demonstrated the mixed morphology of irregular massive rod like blocks and round shaped particles of WO3 distributed on cracked sheets of N-graphene. Nitrogen defects in graphene altered zero band gap semi-metallic graphene to semiconducting material and increased the absorption edge of N-graphene/WO3 nanocomposites towards visible region as studied in DRS analysis. FTIR and Raman studies showed the strong connection between N-graphene and WO3 by making W−O−C surface linkage. The noticeable reduction in PL emission peaks of 3.0% N-graphene/WO3 indicated obvious separation of photo induced charge carriers. The study of radical scavengers suggested that holes (h+) and •OH are the main elements for the decontamination of both MO and 2, 4-DCP. XPS analysis shows all possible C−N bonding configurations in 3.0% N-graphene/WO3. 3.0% N-graphene/WO3 composite showed the maximum photo degradation of MO (~94.0%) and 2, 4-DCP (~81.0%). The synergism between N-graphene and WO3 results into more sporty sites on catalyst and restoring of sp2 structural defects in N-graphene lattice improve the transportation of charge carriers during photocatalysis. This work provides innovative strategies for designing the N-graphene/semiconductor nanosystems with enhanced photocatalytic phenomena in the environmental cleanup remedies.

Characterization and coloration efficiency studies using cyclicvoltammetry and chronocoulometric methods on TiO2 doped WO3 nanocrystalline thin films

Using dc reactive magnetron sputtering, titanium doped WO3 thin films were deposited on various substrates at various oxygen partial pressures and temperatures and their optical, structural, morphological and electrochromic properties were investigated. At a sputtering pressure of 17.6 mTorr and a substrate temperature of 600 K, the optical transmittance of the films in the visible range is found to be up to 84%. As the sputtering pressure increased,the optical bandgap is observed to increase. X-ray diffractograms of the films showed sharp peaks from the reflections of (0 0 1) and (0 2 1) planes of monoclinic crystalline phase of WO3. The morphology studies revealed that titanium is incorporated into the films. Films were immersed in an anhydrous electrolyte to investigate their electrochromic properties. The diffusion coefficient of lithium ions and coloration efficiency were calculated using cyclicvoltammetry and chronocoulometric methods. Deposition parameters viz., the sputtering pressure and sputtering temperature were found to influence several parameters that include the thickness, transmittance, bang gap and refractive index of the films.

Facile synthesis and efficient photoelectrochemical reaction of WO3/WS2 core@shell nanorods utilizing WO3∙0.33H2O phase

One-dimensional (1D) WO3/two-dimensional (2D) WS2 heterojunction nanostructures are of great interest in various photoelectrochemical (PEC) and electrochemical applications. In this study, we introduced a simple and effective route to synthesize 2D WS2 shell layer on WO3 nanorods by utilizing WO3∙0.33H2O phase. The formation of WO3∙0.33H2O nanorods was critically affected by hydrothermal reaction temperature. The WO3∙0.33H2O phase was preferentially transformed into hexagonal WO3 and 2D WS2 through oxidation and sulfurization at 450 °C, respectively. The 2D WS2 shell layer was more favorably formed on WO3 nanorods, which were synthesized at 180 °C and possessed a significant amount of WO3∙0.33H2O phase (referred to as W-180), than on WO3 nanorods with predominant monoclinic WO3 phase, which were synthesized at 200 °C (referred to as W-200). Thus, the WO3/WS2 core@shell nanorods from W-180 exhibited significantly enhanced PEC performance because of the improved charge transfer properties attributed to the advantageous heterojunction effect of 1D WO3/2D WS2. The new synthesis route from WO3∙0.33H2O phase to 2D WS2 can be applied to synthesize various WO3/2D WS2 heterojunction nanostructures, such as thin films, nanoparticles, and nanorods.

Investigation on structural, morphological and electrochemical properties of Mn doped WO3 nanoparticles synthesized by co-precipitation method for supercapacitor applications

The work reported here, demonstrates the synthesis of pristine WO3 and Manganese (Mn)-doped through the hydraulic acid-assisted precipitation method. Structural, morphological, compositional, optical and electrochemical properties of the synthesized samples were analysed. The structural analysis through X-ray diffraction studies confirmed the monoclinic phase of WO3 as well as the substitutional incorporation of Mn inWO3 lattice. A bandgap value of 2.9 eV was estimated from Optical analysis using Kubelka-Munk model. The defect centered luminescence as a consequences of Mn doping was analyzed using photoluminescence spectroscopy (PL). FT Raman Spectroscopic data also reconfirmed the monoclinic structure of the sample and incorporation of Mn into the lattice of Mn-doped WO3. The surface morphological study was performed using Field Emission Scanning Electron Microscope (FESEM), which exhibits the development of mesoporous networks. The Conductivity, dielectric and electrochemical studies were performed on these mesoporous structures to inveterate the impact of Mn doping. A dynamic increment in AC conductivity was observed with doping even at room temperature. Most significantly, we prove that Mn doped WO3 for the first time, Nanoparticles are an outstanding candidate for applications for supercapacitors. Pure and Mn doped WO3 electrochemical properties cyclic voltammetry measurements have been used to analyze samples. The results showed the excellent electrochemical efficiency on 1 wt% Mn doped WO3 electrode (1178 F/g specific capacitance at 2 mA/cm2 and charge transfer ability) for supercapacitors.

CuO-doped WO3 thin film H2S sensors

WO3 and CuO-doped WO3 (0.03CuO-0.97WO3) thin films were prepared by electron beam evaporation on fused silica and alumina substrates and their optical and H2S sensing properties were studied. As-deposited films were amorphous and crystallized into the monoclinic WO3 phase after annealing at 400 °C for 2 h in air. The thicknesses of the WO3 and CuO-doped WO3 films were 830 ± 10 nm and 642 ± 10 nm, respectively. The refractive indices were in the range: 2.33−1.80 in UV–vis-NIR region. The surface electrical conductivity of WO3 decreased drastically by ∼103 times on doping with 3 mol% of CuO. The H2S response of films was measured as a function of operating temperatures in the range of 200 °C–300 °C and it is found that CuO doping produces a large enhancement in H2S response. The sample 0.03CuO-0.97WO3 shows peak response of 11,700 for 600 ppm H2S at 275 °C. The response and recovery transients improve significantly with CuO doping in WO3 and with an increase in the sensor operating temperature from 200 °C–300 °C.

Dual S-scheme heterojunction ZnO–V2O5–WO3 nanocomposite with enhanced photocatalytic and antimicrobial activity

In this work, tri-phase direct dual S-scheme ZnO–V2O5–WO3 heterostructured nanocomposite and pure ZnO, V2O5, and WO3 nanoparticles were synthesized by using a facile co-precipitation approach to investigate antibacterial and photocatalytic characteristics of the grown nanocomposite. The physical properties of as-synthesized products were examined by employing characterization techniques such as Scanning electron microscope (SEM), Energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Raman, Fourier transform infrared spectroscopy (FTIR), and UV–vis spectroscopy. The XRD results confirmed the formation of pristine ZnO, V2O5, WO3 nanoparticles and the existence of diffraction peaks related to hexagonal phase ZnO, orthorhombic V2O5, and monoclinic phase of WO3 in ZnO–V2O5–WO3 nanocomposite. The variation in structural parameters was studied by SSP, Scherrer plot, and W–H models. The energy bandgap of nanocomposite (2.63 eV) was calculated from UV–vis spectroscopy, which indicated the usability as a photocatalyst under direct sunlight. FTIR and Raman's spectra also supported the formation of the ZnO–V2O5–WO3 nanocomposite. Spherical and roughly hexagonal morphology were seen in SEM images. EDX analysis has confirmed the existence of Zn, V, W, and O in the nanocomposite. The antibacterial test against Klebsiella pneumonia, Staphylococcus aureus, Proteus Vulgaris, and Pseudomonas aeruginosa bacteria showed higher activity. The photocatalytic performance of the ZnO–V2O5–WO3 nanocomposite (99.8%) was the highest against methylene blue (MB) as compared to pure ZnO (78.8%), V2O5 (85.8%), and WO3 (80.0%) under natural sunlight. The degradation efficiency of ZnO–V2O5–WO3 against cresol red (CR), rhodamine-B (RhB), methyl orange (MO), safranin-O (SO), and methyl red (MR) dyes was 67.0%, 86.6%, 98.0%, 76.8%, and 99.0%, respectively, under direct sunlight in 80 min. Different schematic models are designed to illustrate the photocatalytic reaction mechanism, whereas the separation of charge carriers and enhanced photocatalytic performance can be efficiently explained by S-scheme.

The Influence of the Structural and Morphological Properties of WO3 Thin Films Obtained by PLD on the Photoelectrochemical Water-Splitting Reaction Efficiency.

Due to its physical and chemical properties, the n-type tungsten oxide (WO3) semiconductor is a suitable photoanode for water decomposition reaction. The responses of the photoelectrochemical PEC water-splitting properties as an effect of structural and optical changes of WO3 thin films, as well as the nature of electrolyte solutions, were studied in this work. The WO3 thins films have been obtained by pulsed laser deposition (PLD) on silicon (Si(001)) covered with platinum substrates using three different laser wavelengths. As the XRD (X-ray diffraction) and XTEM (cross-section transmission electron microscopy) analysis shows, the formation of highly crystalline monocline WO3 phase is formed for the film deposited at 1064 nm wavelength and poor crystalline phases with a large ordering anisotropy, characteristic of 2D structures for the films deposited at 355 nm and 193 nm wavelengths, respectively. The photogenerated current densities Jph depend on the laser wavelength, in both alkaline and acidic electrolyte. The maximum values of the photocurrent density have been obtained for the sample prepared with laser emitting at 355 nm. This behavior can be correlated with the coherent crystallized atomic ordering that appear for long distances (10–15 nm) in the (001) plane of the monoclinic WO3 phase structure films obtained at 355 nm laser wavelength. All the samples show poor current density in dark conditions and they are very stable in both acidic and alkaline solutions. The highest photocurrent density value is obtained in acidic solution for the WO3 thin film prepared by 355 nm laser (29 mA/cm2 at 1.6 V vs. RHE (1.35 V vs. Ag/AgCl)).

Synthesis of Citrus Limon mediated SnO2-WO3 nanocomposite: Applications to photocatalytic activity and electrochemical sensor

The SnO2-WO3 nanocomposite was synthesized through green combustion method using Citrus Limon (lemon Juice) as a fuel. Powder X-ray Diffraction (PXRD) pattern confirms the biphasic composite having (i) tetragonal SnO2 (JCPDS No: 041-1445) and (ii) monoclinic WO3 (JCPDS No: 033-1387) phases. Fourier Transform Infra-red (FTIR) spectrum shows the vibrational peaks at 598 cm-1 for Sn-O-Sn and 711 cm-1 and 807 cm-1 for W-O bonds, respectively. A strong absorption band was observed at 268 nm, which is corresponding to the bandgap of 4.09 eV. The SnO2-WO3 nanocomposite shows agglomerated, irregular shape of nanoparticles. The average particle size was found to be 75 nm. SnO2-WO3 nanocomposite shows marvellous photocatalytic activity against methylene blue (MB) dye degradation in all parameters. Also, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques were employed to analyze the electrochemical properties of prepared samples by using modified carbon paste electrodes for the determination of hydrogen peroxide (H2O2).

Pulsed laser deposition of nanostructured tungsten oxide films: A catalyst for water remediation with concentrated sunlight

The increasing interest for addressing photocatalyst materials towards an effective application with sunlight is an important topic in materials science. We present here a novel investigation of tungsten trioxide (WO3) coatings fabricated by pulsed laser deposition (PLD) with the aim of providing a nanostructured photocatalyst capable of working with concentrated sunlight and exhibiting good stability in acidic environment. This is important since: (1) acidic pH is common in industrial wastewaters and (2) acidic pH is also known to enhance photo-Fenton reactions. Samples produced by PLD were deposited on glass slides with area of 19 cm2 and then thermally annealed at different temperatures (200, 400 and 600 °C) for 8 h to investigate the growth mechanism of WO3. Material characterization was performed by scanning electron microscopy (SEM), X-Ray diffraction (XRD) and micro-Raman, revealing the growth of a crystalline monoclinic phase of WO3 with a highly structured surface featuring nanoflakes in a flower-shape like structure with an energy bandgap of 2.6 eV. To study its photocatalytic properties, the catalyst annealed at the temperature of 600 °C evolved into a complete WO3 oxide presenting monoclinic phase and was investigated under labscale artificial visible light in both direct photocatalysis and in presence of H2O2 as a radical source (photo-Fenton-like process) using 10 ppm solutions of the Methylene Blue (MB) dye as a model pollutant. The study was then replicated in higher volume scale under concentrated solar light from a parabolic dish concentrator (PDC) apparatus to demonstrate application. Results highlighted high surface adsorption of 15%, 54% total MB degradation on direct photocatalysis and 85% in the photo-Fenton-like mode after 120 min of experiment.

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.

The hierarchical nanostructured Co-doped WO3/carbon and their improved acetone sensing perfomance

Hierarchical nanostructured Co-doped WO3 with carbon as template has been successfully synthesised through facile sol-gel method. The synthesised Co-doped WO3 was characterized by X-ray diffraction, Scanning electron microscopy, Transmission electron microscopy, Energy dispersive X-ray spectrometry, and Brunauer-Emmett-Teller and X-ray photoelectron spectroscopy. The gas sensing properties of WO3 doped with Co from 0 to 0.8 wt % were also investigated on various VOCs. The fabricated sensor based on 0.6 wt% Co-doped WO3 with carbon as a template showed good sensitivity, selectivity, fast response and recovery time towards 1.5 ppm of acetone at 50 °C under 90% relative humidity. The excellent gas sensing properties could be attributed to high surface area, small crystallite size, defect of WO3 and Co catalysis effect which promotes gas adsorption and most importantly the stabilized monoclinic phase of WO3, which accounts for the good selectivity.

Studies on magnetron sputtered deposited nanocrystalline tungsten oxide films useful for electrochromic devices

WO3 thin films were sputtered on to different substrates (viz., Si, quartz and ITO coated glasses) at different temperatures and partial pressures using DC magnetron sputtering. The influences partial pressures of O2 and Ar and substrate temperature (at constant sputtering power) on different characteristics viz., optical, structural, morphological, compositional and electrochromism of the films have been investigated. These characteristics were observed to be strongly reliant on deposition conditions. Thickness and roughness (r.m.s.) of the films were found to be in the ranges of 700–918 nm and 3.18–8.4 nm, respectively. The transmittance in the visible wavelength region of these films was found to in the range of 33–80% depending upon the deposition conditions and optical band gap is found to decrease with increase of substrate temperature from 400 K to 600 K at 16.3 mTorr. The X-Ray diffractogram of the films (deposited at 400 K at 16.3 mTorr) exhibited sharp peaks from the reflections of (0 2 1) and (4 2 1) planes of monoclinic crystalline phase of WO3 indicating the prepared films are of crystalline in nature. The structural arrangement of WO3 molecules in the films were analyzed using micro-Raman studies. The morphology studies (using FE-SEM, AFM and EDS techniques) of the films indicated reasonably good stoichiometry of WO3 films; these results further indicated that the films consist of nanoparticles of with sizes varying upon the deposition conditions. For studying the electrochromism of the films, they were immersed in an anhydrous electrolyte (mixture of 0.2 M lithium perchlorate and 50 ml propylene carbonate); coefficient of diffusion of Li+ ions and coloration efficiency were measured by cyclic voltammetry and chrono-coulometry methods, respectively. The partial oxygen pressure and substrate temperature used during deposition were found to influence the above mentioned parameters of the films to a larger extent.