3D WO3 Research Articles

Anchoring Cu2O onto WO3 by adsorption-ascorbic acid reduction: A p-n junction with improved photocatalytic and photoelectrochemical properties

Tungsten trioxide is a promising photoelectric material owing to its abundant structures and unique properties, but the serious photogenerated charge recombination limits its photocatalytic and photoelectrochemical performance. Herein, 0D Cu2O was anchored onto 3D WO3 in-situ via a facile adsorption-ascorbic acid reduction method at room temperature. The coupling of WO3 with Cu2O produces improved charge separation efficiency, thereby the photocatalytic degradation rate and transient photocurrent of optimal WO3/Cu2O are 2.7 and 1.6 times higher than those of WO3, respectively. The enhanced performance is ascribed to the formation of a p-n heterojunction, which was demonstrated by experimental characterizations and theoretical calculation.

Efficient WO3 Nanoplate Arrays Photoanode Modified by ZnO Nanosheets for Enhanced Charge Separation and Transfer to Promote Photoelectrochemical Performances

AbstractA key factor in the photoelectrochemical (PEC) performance of photoelectrodes is the efficient separation and transfer of photogenerated charges. Herein, a novel photoanode comprising three‐dimensional (3D) WO3 nanoplate@ZnO nanosheet hierarchical type‐II heterojunction arrays (3D WO3@ZnO HHAs) is designed and constructed via modification of the WO3 nanoplate arrays with ZnO nanosheets. The synthesized materials are characterized viaX‐ray diffraction (XRD), ultraviolet and visible spectrophotometry (UV–vis), scanning electon microscopy (SEM), transmission electron microscopy (TEM), and X‐ray photoelectron spectroscopy (XPS) analyses. Photoelectrochemical (PEC) test results reveal that the synthesized 3D WO3@ZnO HHAs photoanode exhibits reduced charge transfer resistance, improved electron‐hole pair life, and enhanced photocurrent density (≈4.5 times increase in comparison to that of the bare WO3). The increased light capture and high surface area in contact with the electrolyte as well as the enhanced charge transfer through the synergy between morphology and band structures may be responsible for the improved PEC characteristics.

3D rectangular WO3 hybridized by PrFeO3 nanoparticles with efficient dual charge transfer for enhanced photo-Fenton-like activity

In this work, zero-dimensional (0D) high crystalline PrFeO3 worm nanocrystals were loaded over a three-dimensional (3D) rectangular WO3 to construct a 0D/3D PFO/W Z-scheme heterojunction by an in situ ultrasonic synthetic process. This heterojunction exhibited excellent photocatalytic activities towards the degradation of organic pollutants such as rhodamine B (RhB), Methylene blue (MB), and tetracycline hydrochloride (TC) in the presence of small amounts of H2O2 under visible-light irradiation. For example, the k value of PFO/W + H2O2 was about 67, 107, 45, 27, 11 and 14 times higher than pure H2O2, PrFeO3, WO3, PFO/W nanocomposite, PrFeO3+ H2O2 and WO3+H2O2 respectively during the degradation of MB. The trapping experiments and ESR measurements identified that the generated ·OH, ·O2−, and h+ were the active species involved in the catalysis. Further, the ·OH radical could be continuously generated by Fe3+/Fe2+ and W6+/W5+ conversion and played the dominant role in the degradation of organic pollutants. The superior photocatalytic performance of the PFO/W + H2O2 system was derived from the synergistic effect of the Z-scheme heterostructure and dual photo-Fenton-like oxidation (Fe3+/Fe2+ and W6+/W5+). A possible mechanism was postulated based on the results obtained. In summary, this study provided new insights into synthesizing an effectively heterogeneous 0D/3D Z-scheme dual photo-Fenton-like catalyst for water clarification.

Three-dimensional WO3 nanorod arrays on Si as photoanodes for efficient photoelectrochemical water splitting

Arrays of WO3–Si forest hierarchical structures have been successfully synthesized by growing WO3 nanorod on the surface of vertically aligned n-Si micropillar arrays using a chemical vapor deposition technique. The three-dimensional (3D) WO3–Si nanorod forest improves photoelectrochemical performances; it exhibits higher photocurrent density and a more negative onset potential of 0.5 V vs. reversible hydrogen electrode compared with the WO3 nanorod array on planar Si substrate. More importantly, this directly grown 3D hierarchical structure exhibits extraordinary stability for water oxidation with negligible losses of photoactivity for 24 h in a neutral pH solution. The enhanced photostability is attributed not only to the formation of O vacancies in WO3, which is resistive to photocorrosion but also the multiple internal reflection in 3D hierarchical structure. Our work demonstrates the importance of structural innovation in improving solar water efficiency.

Towards selective glycerol hydrodeoxygenation to 1,3-propanediol with effective Pt-WOx catalyst design: Insights from first principles

DFT simulations predicted the C-O bond cleavage in glycerol on Brønsted acidic Pt-WOx catalyst under a hydrogen atmosphere to be via a “protonation dehydration” mechanism. Interfacial Pt-WOx sites facilitate Brønsted acid (BA) site formation by hydrogen spillover and synergistic activity of Pt and WOx. At strong BA sites, selective formation of 1,3-PDO is likely due to the large difference of over 40 kJ/mol in primary and secondary C-O bond cleavage barriers. The secondary C-O bond cleavage has a linear relation with NH3 binding energy while there is a non-monotonic trend for the primary C-O cleavage. Hence, Brønsted acid strength is a potential descriptor for the catalyst activity and 1,3-PDO selectivity. Synthetic strategies enabling fine dispersion of WOx to trimeric units on the Pt nanoparticles, while preventing W doping and agglomeration of WOx to 3D WO3 on small Pt nanoparticles are desirable for high BA strength and thereby 1,3-PDO yield.

A novel combustion drying synthesis route of 3D WO3–SiO2 composite aerogels for enhanced adsorption and visible light photocatalytic activity

The 3D network nanoporous WO3–SiO2 composite aerogels were successfully synthesized by a novel combustion drying method. All the as-prepared composite aerogels were still with a typical three-dimensional network nanoporous structure, and exhibited high specific surface area with 486–667 m2/g and pore volume 2.0–2.68 cm3/g. Although samples were prepared by burning process, they still shown good hydrophobicity and heat resistance. The adsorption and photocatalytic properties of WO3–SiO2 composite aerogels showed that WO3–SiO2 composite aerogels realized the comprehensive utilization of the adsorption and photocatalysis, and the composite aerogels with high W content exhibited excellent adsorption performance and visible light photocatalytic activity. At last, the mechanism of synthesis of WO3–SiO2 composite aerogels by combustion drying technology was discussed. The results provide a new technical solution for the synthesis of composite aerogels photocatalysts.

Sensing performance for ethylene glycol of hydrothermally self-assembled 3D WO3

A series of hierarchically self-assembled three-dimensional (3D) WO3 with different mass ratios of urea to sodium tungstate were prepared by a one-step hydrothermal method, and the sensing characteristics for ethylene glycol were studied. The results showed that when the mass ratio of urea to sodium tungstate is 0.1:1, the sample WO3-0.1 exhibited the highest response (740.3) to 100 ppm ethylene glycol at 200 °C. In addition, sample WO3-0.1 had excellent selectivity, repeatability, stability and moisture resistance. Due to the hierarchically self-assembled 3D structure, sample WO3-0.1 possessed the maximum number of mesopores, the vacant oxygen concentration of sample WO3-0.1 was twice as much as the sample WO3-0 without urea. Moreover, the growth mechanism of hierarchically self-assembled 3D WO3 was explored by discussing the synergistic effect of ammonium chloride and oxalic acid. Based on outstanding properties for ethylene glycol, the 3D WO3 prepared in this work will have practical significance and potential applications for environmental monitoring.

Charge-Transfer Resonance and Surface Defect-Dominated WO3 Hollow Microspheres as SERS Substrates for the miRNA 155 Assay.

Chemical enhancement with charge transfer (CT) between the adsorbed Raman molecule and the semiconductor mainly contributed to semiconductor surface-enhanced Raman scattering (SERS). In this work, a three-dimensional (3D) WO3 hollow microsphere is first developed as a SERS-active substrate. This 3D WO3 has a smaller band gap and rich surface defects compared with flake WO3. Interestingly, these properties in the WO3 hollow microspheres lead to an increase in charge transfer, which causes a strong CT interaction between the substrate-Raman molecule interfaces, resulting in a large SERS enhancement. The 3D WO3 showed an excellent SERS performance with an enhancement factor (EF) of 1.6 × 106. Finally, a SERS biosensor is constructed based on the above-mentioned semiconductor materials, which can be used for the sensitive detection of miRNA 155 with a limit of detection (LOD) of 0.18 fM by employing a catalytic hairpin assembly (CHA) strategy. This work provides important guidance for semiconductor topography design to improve the SERS performance, supplying a new strategy for biomolecular analysis and disease diagnosis.

3D Tungsten Trioxide Nanosheets as Optoelectronic Materials for On-chip Quantification of Global Antioxidant Capacity

The photoelectrochemical properties of semiconductors mainly depend on the size and shape of the corresponding nanoparticles. Herein, 3D WO3 nanosheets were controllably synthesized with the aid of polyethyleneimine, which presents enhanced photocurrent responses. Based on this excellent photoelectrochemical property, a photoelectrochemical chip was prepared by lithography technology for the smart monitoring of the antioxidant capacity(AC) in red wine and exhibits a series of advantages including rapid response time, high sensitivity, and long-lasting stability. The mechanism of the present photoelectrochemical sensing was explored and shows a single electron transfer reaction. Furthermore, only 200 µL of samples are required for one testing, which demonstrates that the present photoelectrochemical chip can be potentially integrated with a portable commercial device(such as a mobile phone) for further research and development of food and drug supervision.

Three-Dimensional Tungsten Disulfide Raman Biosensor for Dopamine Detection.

Two-dimensional (2D) transition metal dichalcogenides (TMDCs) are promising materials for detection of biomolecules due to their large surface-to-volume ratio. However, their poor response to the cellular environment hinders the realization of high-performance 2D TMDC sensors. Here, we present a hierarchical Raman scattering sensor consisting of the WS2 directly grown on an array of three-dimensional (3D) WO3 nanohelixes (NHs) by sulfurization. Both the adsorption of biomolecules and the proliferation of cells are significantly promoted for the 3D WS2/WO3 NH sensor compared to the control sensor with sulfurized WS2 on 2D WO3 film, leading to much enhanced sensitivity to dopamine. In addition, according to the in vitro test using PC12 cells, the 3D WS2/WO3 NH sensor shows a significant increase in hydrophobicity and Raman frequency shift, indicating that both the attachment of cells and the detection of biomolecules are improved.

Controlled growth of AgI nanoparticles on hollow WO3 hierarchical structures to act as Z-scheme photocatalyst for visible-light photocatalysis

Controllable fabrication of nanomaterials with hierarchical architecture have received much attention in the field of photocatalysis due to their enhanced light-harvesting efficiency. Moreover, fabricating direct Z-scheme heterojunctions havebeenproven to be effective way to enhance the photocatalytic performance of photocatalysts. Herein, hierarchically hollow WO3 nanoflower was successfully synthesized by a simple hydrothermal treatment of tungsten chloride (WCl6) in ethanol solution. Decoration of the obtained WO3 with AgI nanoparticles in situ can form the Z-scheme AgI/WO3 hollow hierarchical nanoflowers (AgI/WO3 HHNFs). The AgI/WO3 HHNFs exhibited excellent photocatalytic activity and remarkable stability for the degradation of tetracycline hydrochloride (TC-HCl) and Eosin B (EB) under the irradiation of a low energy consume light (LED lamp, 5 W). Interestingly, compared to pure AgI nanoparticles, 3D hollow WO3 nanoflowers and AgI/WO3 nanosheets, the AgI/WO3 HHNFs revealed conspicuously enhanced photocatalytic activity. Thisphenomenon could be associated to three aspects, namely the high light-harvesting efficiency, increased light trapping and scattering capability and strongly coupled Z-scheme heterointerface, which effectively improved the photoelectron-hole sepreation efficiency. Our work therefore provide a novel insight for the fabrication of 3D hollow hierarchical structures.

3D core-shell WO3@α-Fe2O3 photoanode modified by ultrathin FeOOH layer for enhanced photoelectrochemical performances

Abstract The solar light absorption efficiency as well as the carrier separation and transfer efficiency in the bulk and on the surface of the photoanodes are still the main challenges for efficient photoelectrochemical (PEC) water splitting. Hence, in this work, a 3D core-shell WO3@α-Fe2O3 photoanode modified by ultrathin FeOOH layer was designed and fabricated for the first time to maximize respective merits of 1D WO3 (excellent electron transport pathways), α-Fe2O3 (strong visible light absorption) and FeOOH (a hole transfer) to achieve efficient PEC performances. As a result, the as-fabricated WO3@α-Fe2O3/FeOOH photoanode exhibits a 120 mV negatively shift in onset potential and yields a photocurrent density of 1.12 mA/cm2 at 1.23 V vs. RHE, which is 1.72 and 3.73 times than that of WO3@α-Fe2O3 and WO3 photoanodes, respectively. Moreover, this work may provide an effective strategy of maximizing the advantages of each component in the composite photoelectrode to achieve effective PEC performance.

Development of Highly Sensitive Ethane Gas Sensor Based on 3D WO3 Nanocone Structure Integrated with Low‐Powered In‐Plane Microheater and Temperature Sensor

AbstractMetal oxide nanostructures are the most promising materials for the fabrication of advanced gas sensors over two decades. Especially, reliable responsivity and selectivity for various harmful gases are the main requirements for the future chemiresistive‐type gas sensors. Here, a 3D nanocone (NC) of WO3 for a real‐time ethane (C2H6) gas sensor is reported. A compact WO3 nanoparticles thin film deposited on the sensor interdigitate electrodes (IDEs) by using radio frequency (RF) sputter and subsequently, WO3 thin film is converted into highly ordered 3D NC with simple monolayer of polystyrene. An in‐plane microheater integrated with a temperature sensor is also developed here in which the heater, temperature sensor, and the gas sensor share the same plane instead of a conventional vertical structure where the microheater and the sensor IDE are placed one above the other. Prior to the fabrication, COMSOL simulations are carried away to predict the heater performance and surface charge densities of the NC structures. A comparative study between the planar WO3 and highly ordered 3D NC WO3 in sensor response has been conducted. The fabricated sensors (planar WO3) and 3D NC WO3 show a high response ΔR/R (%) of 44% and 52% to 100 ppm of ethane at 200 °C respectively.

Regulation of specific surface area of 3D flower-like WO3 hierarchical structures for gas sensing application

The 3D flower-like WO3 nanoparticles with hierarchical structures were synthesized via a hydrothermal synthesis technique by using NaHSO4 as a capping agent. It demonstrates that surface area of the synthesized WO3 products can be manipulated via adjusting concentration of the capping agent NaHSO4 alone. The contribution of alcohol is to construct hierarchical structures with large specific surface areas, while the effect of SO42− is to inhibit the growth rate in the thickness direction of nanosheets which are self-assembled as well to form hierarchical structures. In addition, the gas-sensing property of sensors fabricated by 3D flower-like hierarchical structured WO3 nanoparticles were carried out by detecting different volatile gases with a lower concentration. All the samples are sensitive to ethanol gas and the WO3 3D flowers synthesized by 12 g NaHSO4 exhibit the excellent gas-sensitive property due to the highest surface area, the sensitivity as high as 96 under the concentration of 35 ppm at the optimal temperature of 350 °C, which implies that this 3D hierarchical structured WO3 nanoparticles could be used as a high-efficiency sensor candidate materials for selective detection of ethanol.

Fabrication of Large Area Crack‐Free 2D and 3D WO3 Inverse Opal Films by “Dynamic Hard Template Infiltration Strategy”

AbstractLarge‐area crack‐free 2D and 3D WO3 inverse opal (IO) films, using a wide range of sizes of sacrificial PS spheres as colloidal crystal template, were fabricated by “dynamic hard template infiltration strategy”. First a dynamic PS opal film was formed floating on the surface of water followed by infiltration of a preformed WO3 sol underneath the PS opal film. The resultant PS/WO3 opal composite film was then deposited on various types of substrates (rigid and flexible) and 2D WO3 IO films were obtained following the removal of the PS template by chemical method. Based on this strategy, multiple layer WO3 IOs were fabricated through a layer by layer route. The WO3 IO films deposited on indium tin oxide coated conductive (ITO) substrates were used as active electrode in the fabrication of electrochromic devices, demonstrating their advanced properties for electrochromic application.

Simple synthesis of 1D, 2D and 3D WO3 nanostructures on stainless steel substrate for high-performance supercapacitors

Tungsten oxide (WO3) is a kind of good pseudocapacitive material due to its polyvalent, high theoretical specific capacitance, low cost, excellent electron transport properties and good stability. However, the effect of its morphology on capacitive performance is not so clear yet. Herein, WO3 nanomaterials with different structures such as WO3 nanorods (1D structure), nanoplates (2D structure), and microspheres (3D structure) are fabricated on stainless steel substrate by a facile hydrothermal route. The morphologies and structures are characterized by field emission scanning electron microscopy (FESEM), X-Ray Diffraction (XRD), high resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS). Moreover, the supercapacitor performances of as-prepared WO3 with different structures are investigated systematically. Among these three structures, WO3 microspheres exhibit the highest gravimetric specific capacitance of 536.72 F/g (the areal capacitance is 751.40 mF/cm2) at a scan rate of 10 mV/s and shows excellent cycle stability (92.3% after 2000 CV cycles) when compared with other structures. This strategy provides the versatile way for design the high performance energy storage devices.

Fast triethylamine gas sensing response properties of nanosheets assembled WO3 hollow microspheres

The three-dimensional (3D) WO3 hollow microspheres assembled by single-crystalline nanosheets have been successfully synthesized using a simple low-temperature solvothermal strategy followed by an annealing process in atmosphere. The morphology analysis reveals that the entire growth of WO3 hollow microspheres which mainly includes sphere formed and sphere hollowed these two processes. The as-fabricated WO3 hollow microspheres based sensor exhibits high selectivity and short response time (∼1.5 s) towards 50 ppm triethylamine (TEA) detection at 220 °C, which is better than almost all of the reported TEA sensing sensors. The unique 3D hierarchical hollow and porous structure can be associated with the ultrafast gas-sensing performance. The excellent gas-sensing properties and simple synthesis route demonstrate WO3 hollow microspheres could be a promising candidate as a TEA gas-sensing material.

Facile synthesis 3D flower-like Ag@WO3 nanostructures and applications in solar-light photocatalysis

Tungsten trioxide (WO3) nano-material is an indirect band gap semiconductor with gap energy of 2.5–2.8 eV and has multifunctional in electrochromic, optochromic, gaschromic and photocatalytic applications. In this work, we report a novel and facile approach for the direct fabricates the 3D flower-like WO3. The WO3 were assembled from ultrathin nanosheets as the building blocks and the thickness of sheets only have 10 nm and exposed (002) facets on the top and bottom. The as-prepared WO3 have high special surface area and were employed as scaffolding to deposit the Ag nanoparticles on the surface by the method of in situ redox reaction. The Ag nanoparticles deposition on the surface of WO3 flowers significant enhances the absorption in visible light by the effect of SPR. The photocatalytic performance of Ag@WO3 plasmonic photocatalyst is obviously improved when small amounts of Ag particles are deposited on WO3 photocatalyst surface. This study provided new insights into the fabrication and practical application of high-performance photocatalysts in degrading organic pollutants.

Designing a 3D nanoporous network via self-assembly of WO3 nanorods for improved electrocapacitive performance

This work presents the first report on effective utilization of protonated urea, to design 3D WO3 nanoporous networks using self-assembly of WO3 nanorods, exhibiting enhancement in electrocapacitive performance.

Silver-controlled evolution of morphological, structural, and optical properties of three-dimensional hierarchical WO3 structures synthesized from hydrothermal method

Hierarchical structures of self-assembled three-dimensional (3D) WO3–Ag were synthesized via hydrothermal growth using precursor solutions of peroxopolytungstic acid with different amounts of Ag. The as-grown samples were analyzed by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), thermogravimetric analysis (TGA), Raman spectroscopy, Fourier transform infrared (FTIR) spectroscopy, ultraviolet–visible spectroscopy, and X-ray photoelectron spectroscopy. The XRD and Raman studies showed that as the amount of Ag was varied from 0 to 10 wt% in the hydrothermal growth solution, the crystal phase gradually changed from orthorhombic WO3·0.33H2O to hexagonal WO3. The FTIR and TGA studies revealed different hydration levels, supporting the XRD and Raman results. By controlling the amount of Ag in the precursor solution, platelet-like building blocks and hexagonal building blocks were obtained, highlighting the role of Ag in the hydrothermal growth of 3D WO3·0.33H2O and WO3 microcrystals. In addition, high-magnification FESEM images showed that the Ag nanoparticles were anchored on the surface of the 3D hierarchical WO3–Ag structures, and the UV–vis measurements demonstrated that the 3D hierarchical structures gradually absorbed more light when the Ag content was increased. Moreover, the band-gap energy decreased when the Ag content was increased from 0 wt% (Eg = 2.65 eV) to 10 wt% (Eg = 2.26 eV). These experimental results demonstrate that the amount of Ag played a crucial role in determining the building blocks' morphology, and the hydration level, optical properties, and crystal phase of the WO3·nH2O microcrystals.