WO3 Matrix Research Articles

Oxygen Vacancy Enabled Electronic Structure Engineering of Pt-WO3 Nanosheets toward Highly Efficient BTEX Sensing.

A Pt nanoparticle-immobilized WO3 material is a promising candidate for catalytic reactions, and the surface and electronic structure can strongly affect the performance. However, the effect of the intrinsic oxygen vacancy of WO3 on the d-band structure of Pt and the synergistic effect of Pt and the WO3 matrix on reaction performance are still ambiguous, which greatly hinders the design of advanced materials. Herein, Pt-decorated WO3 nanosheets with different electronic metal-support interactions are successfully prepared by finely tuning the oxygen vacancy structure of WO3 nanosheets. Notably, Pt-modified WO3 nanosheets annealed at 400 °C exhibit excellent benzene series (BTEX) sensing performance (S = 377.33, 365.21, 348.45, and 319.23 for 50 ppm ethylbenzene, benzene, toluene, and xylene, respectively, at 140 °C), fast response and recovery dynamics (10/7 s), excellent reliability (σ = 0.14), and sensing stability (φ = 0.08%). Detailed structural characterization and DFT results reveal that interfacial Ptδ+-Ov-W5+ sites are recognized as the active sites, and the oxygen vacancies of the WO3 matrix can significantly affect the d-band structure of Pt nanoparticles. Notably, Pt/WO3-400 with improved surface oxygen mobility and medium electronic metal-support interaction facilitates the activation and desorption of BTEX, which contributes to the highly efficient BTEX sensing performance. Our work provides a new insight for the design of high-performance surface reaction materials for advanced applications.

Improved photocatalytic properties of WO3 nanoparticles for Malachite green dye degradation under visible light irradiation: An effect of La doping

Abstract Doped materials have received substantial attention due to their increased usefulness in photocatalytic applications. Within this context, the present study was dedicated to investigating the potential of the precipitation technique for producing La-doped tungsten oxide (WO3). To comprehensively characterize the synthesized La-doped WO3, scanning electron microscopy and X-ray diffraction were judiciously employed. The focal point of the investigation encompassed an examination of the impact of varying La concentrations on multiple fronts: the photocatalytic activities (PCAs), as well as any associated structural and morphological modifications. This holistic approach aimed to uncover the intricate relationship between La incorporation and the resulting properties of the WO3 matrix. Through the degradation of Malachite green dye within an aqueous medium, PCA of the La-doped WO3 samples was quantitatively evaluated. Remarkably, over 180 min under irradiation of visible light irradiation, the achieved levels of dye degradation were remarkable, amounting to 81.165, 83.11, and 83.85% for the respective samples. These findings firmly underscore the potential of La-doped WO3 as a proficient photocatalyst, particularly in color removal from wastewater. This study paves the way for enhanced wastewater treatment approaches by utilizing doped WO3 materials.

SYNTHESIS OF MULTICOMPONENT ZRO<SUB>2</SUB>:WO<SUB>3</SUB>:AL<SUB>2</SUB>O<SUB>3</SUB>:MGO

In this work, the phase composition and microstructure of multicomponent ZrO2:WO3:Al2O3:MgO ceramics were studied depending on the concentration of the components. The dependences between the concentration of elements in the initial charge and the phase composition, volume shrinkage, density and microstructure of synthesized samples are determined. It was found by Raman spectroscopy that the addition of an Al2O3:MgO mixture to the initial ZrO2:WO3 matrix does not lead to the formation of a ZrO2:WO3:Al2O3:MgO solid solution. With an increase in the content of Al2O3:MgO, there is an increase in volumetric shrinkage and density, which may be associated with the formation of the liquid phase of the WO3:Al2O3 system at a temperature of 1450 °C and, as a result, more efficient migration of pores and defects to the surface. The analysis of the SEM images of the cross sections of the obtained samples showed that all samples have a developed morphology with different grain shapes.

Temperature-driven enhancement in pseudocapacitive charge storage of Sn-doped WO3 nanoflowers and its high-performance quasi-solid-state asymmetric supercapacitor

The substitution of another metal cations in the WO3 matrix enhances their electrochemical performance due to the synergistic effect. In this report, Sn-doped WO3 nanoflowers are synthesized via a facile single-step hydrothermal method. Further, the temperature-dependent pseudocapacitive behavior of Sn-doped WO3 nanoflowers is investigated for quasi-solid state asymmetric supercapacitors (QSSAC). The electrochemical study reveals that the specific capacitance values of WO3 increase from 72 F g−1 to 138 F g−1 (Sn-doped WO3) at 1 A g−1. The temperature-dependent specific capacitance values of Sn-doped WO3 nanoflowers demonstrating six times enhancement with rising temperature, from 109 F g−1, 139 F g−1, 194 F g−1, 301 F g−1, to 603 F g−1 at 10 °C, 20 °C, 30 °C, 40 °C, to 50 °C respectively. Furthermore, the QSSAC exhibits better stability of 97.51 % up to 2500th cycles with an energy density of 8 W h kg−1 and a power density of 6400 W kg−1, attributed to enhanced conductivity, large diffusion capability, and high strength with multiple redox active sites. The experimental results emphasize the promising electrochemical features of the Sn-doped WO3 matrix, which is an effective approach for electrode materials development.

Redox-based ion-gating reservoir consisting of (104) oriented LiCoO2 film, assisted by physical masking

Reservoir computing (RC) is a machine learning framework suitable for processing time series data, and is a computationally inexpensive and fast learning model. A physical reservoir is a hardware implementation of RC using a physical system, which is expected to become the social infrastructure of a data society that needs to process vast amounts of information. Ion-gating reservoirs (IGR) are compact and suitable for integration with various physical reservoirs, but the prediction accuracy and operating speed of redox-IGRs using WO3 as the channel are not sufficient due to irreversible Li+ trapping in the WO3 matrix during operation. Here, in order to enhance the computation performance of redox-IGRs, we developed a redox-based IGR using a (104) oriented LiCoO2 thin film with high electronic and ionic conductivity as a trap-free channel material. The subject IGR utilizes resistance change that is due to a redox reaction (LiCoO2 ⟺ Li1−xCoO2 + xLi+ + xe−) with the insertion and desertion of Li+. The prediction error in the subject IGR was reduced by 72% and the operation speed was increased by 4 times compared to the previously reported WO3, which changes are due to the nonlinear and reversible electrical response of LiCoO2 and the high dimensionality enhanced by a newly developed physical masking technique. This study has demonstrated the possibility of developing high-performance IGRs by utilizing materials with stronger nonlinearity and by increasing output dimensionality.

Photocarrier transfer induced by Nδ− → Wδ+ in tungsten trioxide/carbon nitride for dual-path production of hydrogen peroxide towards ciprofloxacin degradation

Photo self-Fenton catalyst is a promising candidate for solar energy conversion and environmental remediation. Here we reported a Tungsten trioxide/carbon nitride (WO3/CN) in which the surficial amino groups on CN are inserted into the WO3 matrix, forming coordinate covalently Nδ− → Wδ+ in construction of an intimate S-scheme heterojunction. The intimantance promotes the transfer of photocarriers under light irradiation. The nanohybrids produced hydrogen peroxide (H2O2) in a rate about 20 times of pristine CN. A dual-path architecture in which H2O2 are produced via hole-water oxidation and electron-oxygen reduction was poposed. It is founded that ciprofloxacin also involved in production of H2O2 by their deprotonation to superoxide anions, and holes and hydroxyl radicals effectively attack the weak sites in skeleton of ciprofloxacin. This work suggests a great significance of strategy in self-producing of H2O2 in utilizing solar energy and molecular oxygen for water, particularly the surface water decontamination.

Opto-electronic and electrochemical evaluations of particulate wo3 and sno2 in electrocodeposited Zn- tio2 nanocomposites coatings for sensor application

This study synthesized, characterized and determined the electronic and optical properties of Zn-TiO2, Zn-TiO2-WO3 and Zn-TiO2-SnO2 nano-composite coatings on low carbon steel. It has also determined the effect of these coatings on the corrosion of mild steel in saline environment. This was with a view to produce an active coating to providing alternative to hazardous chromium coating. Active multi functional nano crystalline coatings of the composites were electrolytically fabricated on low carbon steel from Zinc bath, with its Cation and nanoparticulates of TiO2, SnO2 and WO3 were uniformly codeposited in the Zn matrix. The nano-powders were characterized with Scanning Electron Microscope/Energy Dispersive Spectrometer (SEM/EDS) analyses for confirmation of the chemical compositions and purity. The electrocodeposition bath compositions were developed with 120 gram per litre of ZnCl2, 30 gram per litre of KCl along sides with the nanopowders. Other additives including cetylpridinum chloride, 2- Butyne 1,4diol were added as surfactants and Thiourea was added as stabilizer. The coated specimens were sectioned into parts, some of which were characterized with electrical meters and solar simulator to determine the electrical conductivity and solar response of the coated samples respectively. Samples were also subjected to corrosion experiment in 3.5% NaCl (saline) media to study their corrosion resistance properties in the test media through Potentiodynamic polarization method. The results, the electrical conductivity of the generated nano-composite coatings displayed a better electrical conductivity of 2.45E-01Ω-1m-1 which made it a better sensor material and outstanding corrosion resistance with corrosion rate at 0.10116 mm/year. The study concluded that both matrices with the Nano Particulate WO3 and SnO2 can be use as sensor materials but the WO3 matrix showed a better electrical conductivity both in the presence and absence of uv light and enhanced corrosion protection under light and dark conditions, thus a better sensor’s material.

Inserting Bi atoms on the [WO6] framework: Photochromic WO3/Bi2WO6 nanoparticles enable visual sunlight UV sensing

Photochromic tungsten oxide (WO3) offers incredible prospects for protecting human health by visually sensing ultraviolet (UV) radiation exposure from sunlight. Heterojunction engineering can improve the charge carrier separation efficiency in the photochromic procedure to implement this possibility, but it suffers from the finiteness of crystal phase interfacial contact and/or the complexity of synthetic protocols. Here, the construction of an atomic-scale crystal/amorphous WO3/Bi2WO6 nanoparticle results from introducing Bi atoms on the [WO6] framework to form [Bi2O2] components for in-situs incorporating Bi2WO6 into the WO3 matrix. The absence of well-defined interfaces in WO3/Bi2WO6 type II heterostructures ensures an efficient photoexcited electrons transfer from Bi2WO6 to WO3; abundant WO6 units serve as the sites for rapid capture and consumption of photogenerated electrons to facilitate electron-hole separation. Complexing the efficient photochromic products with hydroxyethyl cellulose, the WO3/Bi2WO6-based photochromic films (PCFs) and a colorimetric card indicating different UV intensities are developed. The invisible UV rays are converted into visible color changes; thus, the UV radiation intensity can be estimated from the dark change in the colored PCFs. This work presents a way to elevate the carrier utilization efficiency in WO3 and delivers candidates for exploring efficient and cost-effective UV radiation sensors.

Enhanced electrochromic properties of Ag-incorporated WO3 nanocomposite thin films

WO3 nanocomposite thin films, in which metal nanoparticles are incorporated into a WO3 matrix, offer an enhanced electrochromic response speed with color neutrality. This article reports the structural, optical, and electrochemical properties of Ag nanoparticle-incorporated electrochromic WO3 thin films with different concentrations. Room-temperature-sputtered thin films using composite targets with a low Ag concentration exhibited a random distribution of small nanoparticles. In contrast, in the film with a higher Ag concentration, the particles were merged, resulting in a single or polycrystalline phase. Surface plasmon resonance peaks were observed in the absorption spectra of the Ag–WO3 composite films, indicating the formation of metallic nanoparticles, which was also confirmed via high-resolution transmission electron microscopy. The optical bandgaps decreased gradually from 3.15 eV for WO3-δ to 3.02 and 2.99 eV for W0.97Ag0.03O3-δ and W0.91Ag0.09O3-δ thin films, respectively. The W0.91Ag0.09O3-δ thin film showed a faster switching time of 2.6 s for coloring and 4.8 s for bleaching with a higher coloration efficiency of 66.52 cm2/C than those of the WO3-δ thin film, which were 3.8 s, 6.8 s, and 58.68 cm2/C, respectively. However, transmittance modulation in the W0.91Ag0.09O3-δ thin film was inferior to that in the other films. Furthermore, the W0.91Ag0.09O3-δ thin films were black in the colored state, whereas the bare WO3-δ and W0.97Ag0.03O3-δ thin films were Prussian blue, suggesting the realization of color neutrality through the incorporation of Ag nanoparticles.

Localized Electric Field‐Induced Efficient Photocatalytic Oxidation over Cu‐Doped WO3 Nanofibers with Strong Dopant/Matrix Interaction

AbstractPhotocatalytic oxidation technology can mineralize hazardous volatile organic compounds (VOCs), but the poor photocatalytic oxidation activity limits its practical application. Here we develop Cu‐doped WO3 electrospun nanofibers through a non‐equivalent doping strategy. The Cu dopant prefers substituting five‐coordinated W atoms atop the WO3 matrix, inducing strong dopant/matrix interaction (SDMI) effect and prominent charge rearrangement. A localized electric field (LEF) forms pointing from positively charged WO3 matrix to negatively charged Cu dopant, which triggers efficient photoexcited charge separation. Further, the Cu dopant promoted the production of ⋅OH radicals and thereby enhanced VOCs photodegradation. The 0.7 % Cu‐doped WO3 nanofibers show optimal photocatalytic oxidation performance towards formaldehyde and acetone, 5.5 and 4.8 times higher than pristine WO3 nanofibers, respectively. This work highlights the role of dopant‐induced LEF on the charge carriers separation and might shed light on developing more efficient photocatalysts with non‐equivalent dopants.

Phase evolution in annealed Ni-doped WO3 nanorod films prepared via a glancing angle deposition technique for enhanced photoelectrochemical performance

Ni-doped WO3 nanorod films were fabricated via a reactive magnetron cosputtering with a glancing angle deposition technique. The crystal structure and surface morphology were observed using grazing incident X-ray diffraction and field emission Scanning Electron Microscopy, respectively. The chemical compositions and oxidation state of each element were investigated by X-ray photoemission spectroscopy. The local structure and phase evolution were investigated via X-ray absorption spectroscopy. The local structure of Ni atoms in WO3 nanorod films is characterized as a NiWO4 nanocluster in the WO3 matrix, which is supported by calculated spectra. The phase information obtained after annealing demonstrates that short-length order in amorphous transitions to crystallinity. The phase information of the local structures were acquired and discussed as well as the effect on the annealing process. The coupling of amorphous WO3, crystalline WO3, and amorphous NiWO4 exhibits high photoelectrochemical activity of the sample annealed at 400 °C, which was observed with a large current density (2.35 μA/cm2) at 1.20 V vs. Ag/AgCl under visible light irradiation, which is greater than that of the unmodified WO3 photoelectrode (1.38 μA/cm2).

Enhanced electrochromism from non-stoichiometric electrodeposited tungsten oxide thin films

Nanocrystalline structure tungsten oxide (nc-WO3; WO3·2H2O) thin films were deposited on fluorine-doped tin oxide (FTO) substrates via a facile electrochemical deposition (ECD) method. The X-ray diffraction (XRD), Fourier Transform Infrared (FT-IR) spectrum, and scanning electron microscope (SEM) results confirmed the gradual temperature dependent structural transitions from nanocrystalline tungsten oxide (nc-WO3) to amorphous tungsten oxide (a-WO3) at 200 °C. Electrochromic (EC) performances of the films were examined in an aqueous solution of 0.5 M H2SO4 by cyclic voltammetry tests integrated in-situ transmittance measurements. The results showed that the EC properties of WO3 films were closely correlated to its structural arrangements of –OH groups and the structural water molecules present in the WO3 matrix. A fast-switching speed (5 s for coloration and 3 s for bleaching), a significant optical modulation (above 89 % at 632 nm), a high coloration efficiency of 51.1 cm2/C and cycling stability of more than 1000 cycles were achieved for nc-WO3 film. Additionally, an EC device was successfully assembled using NiO film prepared by chemical bath deposition as a complementary electrode and exhibited fascinating performance.

Physical characterization of Ag:WO3 cermet films used as top electrode for stable and high contrast organic light-emitting diodes

A low reflectance green top-emitting OLED using a cermet Ag:WO3 thin film as a top cathode has been fabricated and fully characterized. The cermet film has been made by co-evaporating Ag and WO3 materials. Depending on the Ag concentration in the WO3 matrix, the optical and electrical properties vary a lot, as this will be investigated by optical simulations as well as by studying single film properties deposited on silicon and glass wafers. A plasmonic absorption of Ag occurs for metal concentrations around 60–70%, which confirms the “nano” nature of the cermet material, with Ag nanocrystals embedded in an amorphous WO3 oxide matrix (also confirmed by TEM). Using an optimal (optical, electrical) Ag:WO3 (70%) cermet composition as a top electrode in the OLED allows to strongly reduce the device mean reflectance in the visible while its contrast ratio becomes far better (maximum + 76% at 1000 lux) than a reference green device (with Ag as top electrode instead of Ag:WO3). The device with the cermet shows very good lifetimes when driven at constant current drive: an extrapolated lifetime of 90 000 h at 100 cd/m2 has been estimated, based on accelerating ageing tests done for 1000 cd/m2 to 20 kcd/m2 initial luminance values.

Role of Cu in the enhancement of NH3 sensing performance of spray pyrolyzed WO3 nanostructures

Cu doped WO3 (Cu: WO3) films synthesized by chemical spray pyrolysis were explored for Ammonia (NH3) gas sensing. Obtained films were examined by X-ray diffraction technique (XRD), Scanning Electron Microscopy (SEM), UV–Visible spectroscopy (UV), Photoluminescence (PL), Raman and X-ray Photoelectron spectroscopy (XPS). XRD and Raman studies reveals the existence of monoclinic-I (γ-WO3) phase. Lower angle shift of (200) peak was noted in XRD for 3% Cu: WO3 primarily due to tensile strain developed in the WO3 lattice caused by Cu incorporation. SEM morphographs exhibited well defined grains on amalgamation of Cu in WO3 matrix. Photoluminescence studies showed enhancement in the oxygen vacancies upon Cu doping which plays crucial role in improving the sensor response. Gas sensing measurements of the films were performed at an operating temperature of 250 °C towards 1, 3 and 5 ppm concentration of NH3 gas. Incorporation of Cu into WO3 enhanced sensor response and shortened response time comapred to pristine WO3 films. 3% Cu doped WO3 showed good sensor response of 1.58 for 5 ppm concentration of NH3.

Electrochemical Characteristics of Reconstructed WO3 Electrodes by Embedding ITO Nanocrystals

ITO nanocrystal-embedded WO3 electrodes (ITO@WO3) have been successfully fabricated with a facile solution process, and the structure and electrochromic properties were studied by transmission electron microscope, scanning electron microscope, X-ray diffraction and electrochemical methods. The results show that moderate embedding of ITO nanocrystals (NCs) effectively improves the electrochromic performance that the optical modulation and coloration efficiency are increased from about 20.86% and 30.18 cm2 C−1 to about 29.37% and 33.49 cm2 C−1, respectively. Further analysis of the cyclic voltammetry and chronoamperometry indicate that the diffusion-controlled reactions associating with the electrochromic of the electrodes are enhanced with the increasing ITO NCs at the low content, while the excessive ITO NCs inhibit them. On the other hand, the capacitive contribution to the total insertion/extraction charges keep steady with various ITO NCs contents in the considering range of the present work, suggesting that ITO NCs affect little on the capacitive nature of the WO3 matrix. These results provide a better understanding of the electrochemical kinetics of the nanocrystal embedded electrodes and are helpful to design more efficient electrochromic devices.

RGO/WO3 hierarchical architectures for improved H2S sensing and highly efficient solar-driving photo-degradation of RhB dye

Surface area and surface active sites are two important key parameters in enhancing the gas sensing as well as photocatalytic properties of the parent material. With this motivation, herein, we report a facile synthesis of Reduced Graphene Oxide/Tungsten Oxide RGO/WO3 hierarchical nanostructures via simple hydrothermal route, and their validation in accomplishment of improved H2S sensing and highly efficient solar driven photo-degradation of RhB Dye. The self-made RGO using modified Hummer’s method, is utilized to develop the RGO/WO3 nanocomposites with 0.15, 0.3 and 0.5 wt% of RGO in WO3 matrix. As-developed nanocomposites were analyzed using various physicochemical techniques such as XRD, FE-SEM, TEM/HRTEM, and EDAX. The creation of hierarchic marigold frameworks culminated in a well affiliated mesoporous system, offering efficient gas delivery networks, leading to a significant increase in sensing response to H2S. The optimized sensor (RGO/WO3 with 0.3 wt% loading) exhibited selective response towards H2S, which is ~ 13 times higher (Ra/Rg = 22.9) than pristine WO3 (Ra/Rg = 1.78) sensor. Looking at bi-directional application, graphene platform boosted the photocatalytic activity (94% degradation of Rhodamine B dye in 210 min) under natural sunlight. The RGO’s role in increasing the active surface and surface area is clarified by the H2S gas response analysis and solar-driven photo-degradation of RhB dye solution. The outcome of this study provides the new insights to RGO/WO3 based nanocomposites’ research spreadsheet, in view of multidisciplinary applications.

One-pot synthesis of tungsten oxide nanostructured for enhanced photocatalytic organic dye degradation

Herein, WO3 nanorods have been prepared by simple hydrothermal method with the assistance of Na2SO4 as a structure-directing agent (SDA). The impact of SDA concentrations on the structural, morphological, optical, and photocatalytic performance of WO3 nanoparticles has been investigated. From XRD pattern, the phase transformation (monoclinic to hexagonal) was observed after adding SDA into WO3 matrix. Randomly oriented hexagonal WO3 nanorods were developed by the influence of SDA, which has been observed with FE-SEM analysis. The chemical composition and electronic structure of hexagonal WO3 nanorods photocatalyst were confirmed by X-ray photoelectron spectroscopy. The blue shift absorbance was recorded in UV–Vis spectrum. In the PL spectrum, the surface oxygen vacancy or defects were obtained at a wavelength of 520 and 552 nm. Also, the influence of defects in the WO3 nanorods facilitates to improve the photocatalytic dye degradation performance. The hexagonal WO3 nanorods prepared at 0.05 m of SDA exhibit maximum degradation efficiency of 86% under visible light exposure. Furthermore, the specific catalyst showed an excellent stability and reusability up to four consecutive cycles of photocatalytic dye degradation.

Fast response of CO2 room temperature gas sensor based on Mixed-Valence Phases in Molybdenum and Tungsten Oxide nanostructured thin films

Molybdenum - tungsten oxide (Mo1-xWxO3, x = 1, 0.8, and 0.6) nanostructured thin films-based room temperture (RT) gas sensors are prepared by means of reactive RF magnetron co-sputtering at 400 °C. The structural, morphology, topography, optical, and electrical characterizations of the prepared sensors are carried out by XRD Rietveld structure refinement analyses, SEM, AFM, UV-VIS spectrophotometer, and source meter. By controlling the deposition temperture of 400 °C, a co-existing phase of MoO3 and MoO2 in WO3 matrix is presented with high oxygen vacancies concentration as calculated from the XRD Rietveld Refinement analyses. By increasing the Mo content, the calculated oxygen vacancies concentration increases by factor of 1.36. The optical characterization of Mo0.2W0.8O3 thin film shows a high transparent of 99.6% at 500 nm. The prepared thin films have successfully tested to detect carbon dioxide (CO2) at RT (20 °C) with high selectivity and repeatability. The Mo0.4W0.6O3 sensor film shows an electrical Schottky contact with fast response and recovery times towards CO2 under UV light activation. Mo0.4W0.6O3 thin film under dark and UV conditions were able to detect low CO2 concentration of 2 and 0.5 sccm CO2 at RT, respectively. Under UV illumination, Mo0.4W0.6O3 film shows a fast response and recovery time of 6.53 and 8.05 s at 0.5 sccm with sensitivity of 29.19%. Under UV photonic activation, higher electron concentration is presented in the oxide surface, which leads to high probability for reaction with CO2 molecules, and consequently enhanced the chemisorption of CO2. The enhanced CO2 gas sensitivity and fast response may refer to the high oxygen vacancies concentration and the active role of the grain boundaries in MoO2, MoO3 and WO3 mixed-valence nanostructured under UV activation.

Building architecture of TiO2 nanocrystals embedded in amorphous WO3 films with improved electrochromic properties

TiO2 nanocrystals embedded amorphous WO3 electrochromic films have been successfully fabricated with a facile one-step solution process. The structure and electrochromic properties of composite films were studied by transmission electron microscope, scanning electron microscope, X-ray diffraction, Raman spectroscopy, and electrochemical methods. The results show that anatase TiO2 nanocrystals with a size of about 5–10 nm were homogeneously embedded in the amorphous WO3 matrix (TiO2@WO3). Compared with pure WO3 film, the electrochromic performances of TiO2@WO3 are evidently enhanced. The further electrochemical analysis indicates that the enhancement may be mainly ascribed to the reconstruction of amorphous WO3 matrix with the emerging interfaces between nanocrystals and amorphous matrix. And the extremely high value of the coloration/bleaching reversibility is associated with the suppressing effect of TiO2 nanocrystals upon the Li+ trapping in WO3 matrix.

Rationally designed Fe2O3/GO/WO3 Z-Scheme photocatalyst for enhanced solar light photocatalytic water remediation

A novel ternary Fe2O3/GO/WO3 all-solid-state Z-Scheme photocatalyst was rationally designed. Structural, morphological, optical and electronic properties of the synthesized nanocomposite were investigated by XRD, SEM, TEM, UV–vis Diffuse Reflectance and Raman spectroscopy. The results revealed the successful synthesis of the nanocomposite materials. Uniquely, double absorption edges at 2.0 and 2.3 eV for Fe2O3/WO3 and triple absorption edges at 1.5, 1.8 and 2.1 eV for Fe2O3/GO/WO3 were investigated for the first time. Lower absorption band edges dominated for both Fe2O3/WO3 and Fe2O3/GO/WO3, while higher absorption edges dominated for pure nanomaterials. The enhanced interaction among GO, Fe2O3 and WO3 matrix explained the reduction in the CB energy leading to efficient electron separation and transformation and consequently improving the photocatalytic activity. The visible light photocatalytic performance of Fe2O3/GO/WO3 nanocomposites were evaluated for degradation of methylene blue (MB) and crystal violet (CV) dyes as model water pollutants. The photocatalytic activity for degradation of both dyes was found to be greatly enhanced in the presence of ternary Fe2O3/GO/WO3 nanocomposite as compared to nanocomposite systems of Fe2O3/WO3, WO3/GO and Fe2O3/GO or pure Fe2O3 and WO3 nanomaterials. The enhancement in the photocatalytic performance of the ternary Fe2O3/GO/WO3 nanocomposite was expected to be due to the all-solid-state Z-Scheme in which the photogenerated electrons in the CB of photosystem I (WO3) transferred through GO mediator and recombined with the photogenerated holes in the VB of Fe2O3 (photosystem II). So that, the electron-hole pair recombination can be suppressed in both systems. Moreover, the photocatalytic activity of Fe2O3/GO/WO3 nanocomposite has been tested for the degradation of phenol. The results show that 95.4% of phenol was degraded in 120 min. This study provides an efficient green Z-Scheme photocatalyst for water remediation utilizing solar light.