WO3 Nanowires Research Articles

Pd-W18O49 Nanowire MEMS Gas Sensor for Ultraselective Dual Detection of Hydrogen and Ammonia.

Demand for real-time detection of hydrogen and ammonia, clean energy carriers, in a sensitive and selective manner, is growing rapidly for energy, industrial, and medical applications. Nevertheless, their selective detection still remains a challenge and requires the utilization of diverse sensors, hampering the miniaturization of sensor modules. Herein, a practical approach via material design and facile temperature modulation for dual selectivity is proposed. A Pd nanoparticles-decorated W18O49 nanowire gas sensor is prepared for dual detection of hydrogen and ammonia. The sensor exhibits distinct operating temperatures for ultraselective detection of hydrogen (125°C) and ammonia (225°C), with high responses of 35.3 and 133.8, respectively. This dual selectivity with high sensitivity is attributed to enhanced oxygen adsorption, the chemical affinity of sensing materials for target gases, and distinct reactivity profiles of gases. The proposed sensor is further integrated into a microelectromechanical system, enabling its small size, low power consumption, and rapid temperature modulation. Moreover, the practical feasibility of this sensor platform for smart energy monitoring systems is demonstrated by assessing its sensing properties in electrochemical ammonia oxidation reaction systems. This work can provide a practical approach for developing a single gas sensor with multiple functionalities for application in electronic nose systems.

Synthesis of Arrayed Tungsten Disulfide Nanotubes.

Tungsten disulfide nanotubes (WS2-NTs), with their cylindrical structure composed of rolled WS2 sheets, have attracted much interest because of their unique physical properties reflecting quasi-one-dimensional chiral structures. They exhibit a semiconducting electronic structure regardless of their chirality, and various semiconducting and optoelectronic device applications have been demonstrated. The development of techniques to fabricate arrayed WS2-NTs is crucial to realizing the highest device performance. Since the discovery of WS2-NTs, various synthesis techniques have been reported; however, horizontally arrayed WS2-NTs have never been successfully synthesized. Here, we demonstrate a simple technique to synthesize arrayed WS2-NTs. Through precise temperature and gas control, W18O49 nanowires are grown along the [1̅101] direction on an r-plane sapphire substrate, and the nanowires are converted into nanotubes via sulfurization under optimized conditions. The demonstrated synthesis technique for arrayed WS2-NTs will play a central role in the fabrication of devices using transition-metal dichalcogenide nanotubes.

In Situ Generatable and Recyclable Oxygen Vacancy-Modified Fe2O3-Decorated WO3 Nanowires with Super Stability for ppb-Level H2S Sensing.

Detecting hydrogen sulfide (H2S) odor gas in the environment at parts-per-billion-level concentrations is crucial. However, a significant challenge is the rapid deactivation caused by SO42- deposition. To address this issue, we developed a sensing material comprising Fe2O3-decorated WO3 nanowires (FWO) with strong interfacial interaction. During the H2S sensing process, important oxygen vacancies (OVs) are generated in situ and are recyclable on the surface of the Fe2O3 cluster. This sensor achieves a response of 140 (Ra/Rg) toward 50 ppm of H2S at 250 °C, with an experimentally measured detection limit of 1 ppb. It also exhibits remarkable stability, with no significant change observed over a long period of 150 days. Based on a combination of in situ DRIFT and DFT calculations, we have identified that the overactivation of O2 is the key step in the formation of SO42-. This overactivation can be partially modulated by the synergistic effect of Fe2O3 decoration and the in situ generated OVs, regulating the oxidation product to SO2 rather than the toxic SO42-. Furthermore, the continuous generation of OVs compensates for the loss of active sites pertaining to SO42- deposition, thereby contributing to the excellent stability of the sensor. This study underscores the beneficial impact of in situ OV generation in FWO for H2S sensing, offering a dynamic strategy to enhance sensor performance, particularly in terms of stability.

Construction of WO3 nanowires artificial solid electrolyte interphase on silicon nanoparticles with sea urchin like structure for improving silicon anode stability

Giant volumetric variation of silicon during repeat lithiation/delethiation process leads to structure failure of silicon-based anodes and thus their initial high capacitance is hard to be maintained under long-run cyclic charging/discharging. Construction porous structure silicon composites and formation of artificial solid electrolyte interphase (SEI) coating on silicon particles are two effective ways to improve stability of silicon-based anodes. In this work, above two strategies are combined to construct a composite of inorganic artificial SEI WO3 nanowires/Si nanoparticles with sea urchin like porous structure via simple hydrothermal method. The silicon nanoparticles act as seeds for around 70 nm average diameter WO3 nanowires formation in compared with that of WO3 nano-rods around 500 nm diameter without Si nanoparticle seeds. The WO3 nanowire artificial SEI coating is found to be effective in preventing SEI overgrowth and their network provides spaces for volumetric variation of silicon nanoparticles in the bulk anode matrix during cyclic test, leading to reversible charging/discharging of stable bulk anode in compared with pure silicon anode of fast capacitance decay. The gravimetric capacitance of optimized composite reaches 1410.6 mAh·g−1 and its capacity remains 1039 mAh·g−1 after 200 cycles.

Bio-inspired Mechanically Responsive Smart Windows for Visible and Near-Infrared Multiwavelength Spectral Modulation.

Mechanochromic light control technology that can dynamically regulate solar irradiation is recognized as one of the leading candidates for energy-saving windows. However, the lack of spectrally selective modulation ability still hinders its application for different scenarios or individual needs. Here, inspired by the generation of structure color and color change of living organisms, a simple layer-by-layer assembly approach toward large-area fabricating mechanically responsive film for visible and near-infrared multiwavelength spectral modulation smart windows is reported here. The assembled SiO2 nanoparticlesand W18O49 nanowires enable the film with an optical modulation rate of up to 42.4% at the wavelength of 550nm and 18.4% for the near-infrared region, separately, and the typical composite film under 50% stretching shows ≈41.6% modulation rate at the wavelength of 550nm with NIR modulation rate less than 2.7%. More importantly, the introduction of the multilayer assembly structure not only optimizes the film's optical modulation but also enables the film with high stability during 100000 stretching cycles. A cooling effect of 21.3 and 6.9 °C for the blackbody and air inside a model house in the real environmental application is achieved. This approach provides theoretical and technical support for the new mechanochromic energy-saving windows.

Cephalopods' Skin-Inspired Design of Nanoscale Electronic Transport Layers for Adaptive Electrochromic Tuning.

Cephalopods can change their skin color by using high-speed electron transduction among receptors, neural networks, and pigmentary effectors. However, it remains challenging to realize a neuroelectrical transmission system like that found in cephalopods, where electrons/ions transmit on nanoscale, which is crucial for fast adaptive electrochromic tuning. Inspired by that, hereby an ideal, rapidly responsive, and multicolor electrochromic biomimetic skin is introduced. Specifically, the biomimetic skin comprises W18O49 nanowires (NWs)that are either colorless or blue, Au nanoparticles@polyaniline (Au NPs@PANI) ranging from green to pink, and a flexible conductive substrate. As the applied voltage changes from 0.4 V to -0.7 V and back to 0V, the color of the biomimetic skin transforms from green to blue and ultimately to pink. This color change is attributed to the electrically induced redox reaction of Au NPs@PANI and W18O49 NWs, triggered by the transfer of electrons and ions. Furthermore, the high versatility and adaptability of electrical stimulus enable the creation of a highly interactive electrochromic biomimetic skin system through the integration of sensitive acoustic sensors, providing a perfect environment-responsive platform. This work provides a biomimetic multicolor electrochromic skin that depends on electron/ion transfer on nanoscale, expands potential uses for camouflage skin.

Exploring the Gas-Sensing Mechanism of a WO3 Nanowires-Based Sensor for Ethanol Detection by Near-Ambient Pressure XPS

The WO3 nanowires (NWs), fabricated on a commercial Al2O3-based sensor platform, underwent near ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) analysis during ethanol detection. Our findings revealed challenges that may appear in utilizing NAP-XPS studies for studying a real gas sensor in operando conditions. Through NAP-XPS analysis, we explored the gas-sensing mechanisms of pristine and Pt-decorated WO3 NWs for ethanol sensing at different temperatures, demonstrating a combination of several mechanisms commonly observed in metal-oxide chemiresistors. For ethanol sensing, the primary driving force for the sensor's macroscopic electrical response at low temperatures was the adsorption of ethanol molecules. Conversely, at high temperatures, it involved the adsorption of ethoxy groups along with the reducing effect of ethanol on the WO3 surface. It is shown that the surface oxygen vacancies play a crucial role in the ethanol sensing mechanism of WO3 NWs-based gas sensors. Figure 1

Self-heated WO3 nanowires for selective and sensitive detection of NO2 gas at room temperature

Self-heated WO3 nanowires for selective and sensitive detection of NO2 gas at room temperature

Preparation and electrochromic performance of Nb-Doped Tungsten oxide nanowires

Different niobium (Nb)-doped tungsten oxide (WO3) nanowire films were prepared by magnetron sputtering and hydrothermal methods, and their performances were analyzed. The experimental results revealed that Nb doping caused the tungsten oxide nanowire structure to become loose, increased the interplanar spacing, and raised the oxygen vacancy concentration, significantly improving the electrochromic properties. However, with increasing Nb doping levels, the cyclic stability of the samples decreased, possibly due to lattice distortion induced by Nb. The analysis demonstrated that the sample doped with 0.5% Nb exhibited optimal electrochromic performance and displayed a 5.68% coloring transmittance and an 83.3% optical modulation range at a wavelength of 633 nm. This study elucidated the influence of Nb doping on the electrochromic properties of WO3 nanowire films.

Asymmetric Cu(I)─W Dual-Atomic Sites Enable C─C Coupling for Selective Photocatalytic CO2 Reduction to C2H4.

Solar-driven CO2 reduction into value-added C2+ chemical fuels, such as C2H4, is promising in meeting the carbon-neutral future, yet the performance is usually hindered by the high energy barrier of the C─C coupling process. Here, an efficient and stabilized Cu(I) single atoms-modified W18O49 nanowires (Cu1/W18O49) photocatalyst with asymmetric Cu─W dual sites is reported for selective photocatalytic CO2 reduction to C2H4. The interconversion between W(V) and W(VI) in W18O49 ensures the stability of Cu(I) during the photocatalytic process. Under light irradiation, the optimal Cu1/W18O49 (3.6-Cu1/W18O49) catalyst exhibits concurrent high activity and selectivity toward C2H4 production, reaching a corresponding yield rate of 4.9µmol g-1 h-1 and selectivity as high as 72.8%, respectively. Combined in situ spectroscopies and computational calculations reveal that Cu(I) single atoms stabilize the *CO intermediate, and the asymmetric Cu─W dual sites effectively reduce the energy barrier for the C─C coupling of two neighboring CO intermediates, enabling the highly selective C2H4 generation from CO2 photoreduction. This work demonstrates leveraging stabilized atomically-dispersed Cu(I) in asymmetric dual-sites for selective CO2-to-C2H4 conversion and can provide new insight into photocatalytic CO2 reduction to other targeted C2+ products through rational construction of active sites for C─C coupling.

Visible-Light-Driven Inactivation of Bacteria and H2 Generation Catalyzed by Oxygen-Vacancy-Rich One-Dimensional/Two-Dimensional W18O49/g-C3N4 Z-Scheme Heterostructures.

Z-scheme heterostructure-based photocatalysts consist of a reduction photocatalyst and an oxidation photocatalyst, enabling them to possess a high capacity for both reduction and oxidation. However, the coupling reaction between photocatalytic H2 generation through water reduction and sterilization using Z-scheme systems has been rarely reported. Herein, 1D W18O49 nanowires embedded over 2D g-C3N4 nanosheets are well-constructed as an integrated Z-scheme heterojunction. Experimental results and density functional theory calculations not only demonstrate the achievement of efficient interfacial charge separation and transport, leading to prolonged lifetime of photogenerated charge carriers, but also directly confirm the mechanism of Z-scheme charge transfer. As expected, the optimized W18O49/g-C3N4 nanostructure exhibits superior photocatalytic sterilization activity against Staphylococcus aureus as well as excellent H2 generation performance under visible-light irradiation (λ ≥ 420 nm). Due to its nontoxic nature, W18O49/g-C3N4 holds great potential in eradicating bacterial infections in living organisms.

Effective 1D/2D nanostructured S-scheme W18O49/g-C3N4 heterojunction photocatalyst fabrication for improved photocatalytic nitrogen fixation performance

The fundamental insights into the reaction mechanism, especially the electron transfer mechanism, are highly promising yet challenging for W18O49/g-C3N4 heterojunction catalysts during photocatalytic nitrogen fixation. Herein, the 1D/2D nanostructured S-scheme heterojunctions were designed by in situ growth of 1D W18O49 nanowires on 2D g-C3N4 nanosheets through solvothermal method using methanol as solvent. In situ XPS analysis revealed that electrons in the conduction band of W18O49 recombine with holes in the valence band of g-C3N4 under the conduction effect of internal electric field, band bending, and Coulombic attraction in the W18O49/g-C3N4 heterojunction. The photogenerated electrons are retained in g-C3N4, where the negative reduction potential of its conduction band enhances the activation of N2. As a result, the ammonia generation rate employing the optimal W18O49/g-C3N4 heterojunction is 64.8 μmol gcat−1 h−1, approximately double that of W18O49 alone and 2.3 times higher than that of g-C3N4. The enhanced activity and facile methodology make the current material exceedingly appealing for implementation in photocatalytic nitrogen fixation for the synthesis of ammonia.

Significantly enhanced oxygen vacancies in W18O49 nanowires for electrochromic films by annealing in argon

Owing to the energy-efficient attributes of electrochromic technology, there has been a growing emphasis on the fabrication of electrochromic devices with high-contrast and stable performance. As an electron donor, the deliberate incorporation of oxygen vacancies into an electrochromic material is poised to significantly elevate the film's electrochromic characteristics. In this study, we successfully synthesized one-dimensional W18O49 nanowires thin films with enhanced oxygen vacancies using a straightforward combination of solvothermal reactions and annealing in Ar. In comparison to films annealed in air, those treated in argon (Ar) exhibited a higher concentration of oxygen vacancies, resulting in improved light absorption characteristics. The optimal annealing conditions were determined to be 400 °C for 40 min. Under these conditions, the thin film demonstrates enhanced electrochromic performance, exhibiting a notable 71.6% modulation in transmittance, a 27.2% increase compared to the air condition. It displays a rapid response time (Tb = 3.3 s, Tc = 3 s), high coloration efficiency (CE = 55.9 cm2 C−1), and excellent cycling stability (with a ΔT retention rate of 93.9% after 750 cycles).

Enhanced Transport Kinetics of Electrochromic Devices by W18O49 NW/Ti3C2Tx Composite Films

AbstractElectrochromic devices can facilitate the realization of a wide set of future applications, ranging from energy‐saving windows to smart wearables and stealth. Historically, tungsten oxides have been the most studied materials for electrochromism, albeit with bottlenecks like limited conductivity, high charge transport barrier, and low ion diffusivity. Here, inspired by the recent MXene materials, the study has engineered an electrochromic composite of MXene nanosheets (Ti3C2Tx) and W18O49 nanowires (NWs). A transparent conductive electrode is fabricated by co‐assembly of Ag and W18O49NWs, followed by depositing W18O49 NW/Ti3C2Tx layers for the fabrication of the electrochromic device. The incorporation of Ti3C2Tx nanosheets enhances the transport of electrons and ions within the electrochromic layer, leading to a significant improvement in the electrochromic performance. Noteworthily, the film structure comprising 15 layers of W18O49 NW/Ti3C2Tx composite reveals enhanced transmittance modulation (61%), rapid response time (4.5 s coloration, 6.5 s bleaching), and high coloration efficiency (139.1 cm2 C−1). Moreover, the electrode also presents a high diffusion coefficient of Li+ and good cycling stability (96.66% after 250 switching cycles). Finally, a large‐scale (15 × 20 cm2) flexible electrochromic device with a solid electrolyte is successfully fabricated and utilized as a smart window and a flexible stealth patch.

Co single atom coupled oxygen vacancy on W18O49 nanowires surface to construct asymmetric active site enhanced peroxymonosulfate activation

Enhancing the activation of peroxymonosulfate (PMS) is essential for generating more reactive oxygen species in advanced oxidation process (AOPs). Nevertheless, improving PMS adsorption and expediting interfacial electron transfer to enhance reaction kinetics pose significant challenges. Herein, we construct confined W18O49 nanowires with asymmetric active centers containing Co-Vo-W (Vo: oxygen vacancy). The design incorporates surface-rich Vo and single-atom Co, and the resulting material is employed for PMS activation in water purification. By coupling unsaturated coordinated electrons in Vo with low-valence Co single atoms to construct an the “electron fountainhead”, the adsorption and activation of PMS are enhanced. This results in the generation of more active free radicals (SO4•-, •OH, •O2-) and non-free radicals (1O2) for the decomposition of micropollutants. Thereinto, the degradation rate of bisphenol A (BPA) by Co-W18O49 is 32.6 times faster that of W18O49 monomer, which is also much higher than those of other transition-metal-doped W18O49 composites. This work is expected to help to elucidate the rational design and efficient PMS activation of catalysts with asymmetric active centers.

Flexible Ce-doped WO3 nanowire arrays with enriched oxygen vacancies for soft-packaged asymmetric supercapacitor

Tungsten trioxide (WO3) is recognized as a promising anode material for asymmetric supercapacitors (ASCs), yet its low conductivity and stability as well as energy density greatly limit its development. Herein, a flexible Ce-doped WO3 (Ce1.5%-WO3) nanowire array with rich oxygen vacancies is grown on carbon cloth by a solvothermal synthesis. The specific capacitance of Ce1.5%-WO3 is 493F g−1 at 4 A/g and remains 90.4 % after 5000 cycles, superior to that of WO3 nanowire arrays (416F g−1, 80.3 %). The improved performance mainly stems from the synergistic effects of more oxygen vacancies, higher specific surface area, wider lattice spacing, faster ion diffusion, and electron transport generated by Ce doping. As-prepared ASC device can reach an energy density of 31.7 Wh kg−1 at a power density of 700 W kg−1. Furthermore, two flexible soft-packaged ASCs connected in series can illuminate different electronic devices. This strategy proves the great application prospect of Ce-doped WO3 nanowire arrays flexible electrodes in supercapacitors.

A flexible electrochromic device with variable infrared emissivity based on W18O49 nanowire cathode and MXene infrared transparent conducting electrode

Electrochromism with tunable infrared (IR) responses has emerged as an intriguing technology for adaptive IR camouflage and radiative thermal management. Its current development is however hindered by low IR emissivity modulation and unsatisfactory cycle life. Herein, a flexible IR electrochromic device with large IR emissivity modulation and high stability is fabricated by combining an oxygen-deficient W18O49 nanowire cathode and a MXene-based IR transparent conducting electrode. The nanowire structure and abundant oxygen vacancies of W18O49 works in synergy with the high IR transparence of the MXene conducing electrode, to provide the IR emissivity to vary from 0.8 to 0.4 within 3–5 μm (△ε = 0.4), and from 0.77 to 0.3 within 8–14 μm (△ε = 0.47). A long cycle life of more than 2000 cycles was also verified, which could be attributed to the high stability of W18O49 and no material phase transition during cycling. This work demonstrates a viable pathway to design and build high performance flexible IR electrochromic devices for adaptive thermal management.

Composites of W18O49 Nanowires with g-C3N4/RGO Nanosheets for Broadband Light-Driven Photocatalytic Wastewater Purification.

Developing a photocatalyst that can effectively utilize the full solar spectrum remains a high-priority objective in the ongoing pursuit of efficient light-to-chemical energy conversion. Herein, the ternary nanocomposite g-C3N4/RGO/W18O49 (CN/RGO/WO) was constructed and characterized by a variety of techniques. Remarkably, under the excitation of photon energies ranging from the ultraviolet (UV) to the near-infrared (NIR) region, the photocatalytic performance of the CN/RGO/WO nanocomposite exhibited a significant enhancement compared with single component g-C3N4 or W18O49 nanosheets for the degradation of methyl orange (MO). The MO photodegradation rate of the optimal CN/1.0 wt% RGO/45.0 wt% WO catalyst reached 0.816 and 0.027 min-1 under UV and visible light excitation, respectively. Even under low-energy NIR light, which is not sufficient to excite g-C3N4, the MO degradation rate can still reach 0.0367 h-1, exhibiting a significant enhancement than pure W18O49. The outstanding MO removal rate and stability were demonstrated by CN/RGO/WO nanocomposites, which arise from the synergistic effect of localized surface plasmon resonance effect induced by W18O49 under vis-NIR excitation and the Z-scheme nanoheterojunction of W18O49 and g-C3N4. In this work, we have exploited the great potential of integrating nonmetallic plasmonic nanomaterials and good conductor RGO to construct high-performance g-C3N4-based full-solar spectral broadband photocatalysts.

Construct electron transport path through NH2-MIL-125 modified Fe-doped W18O49 nanowires to enhance photocatalytic nitrogen fixation performance

Ammonia has important application value in agriculture and industry as a raw material for producing nitrogen fertilizers and organic chemicals. The Haber-Bosch method is generally utilized to synthesize ammonia through N2 and H2 as raw materials in industry, but the process generates serious energy consumption and pollution. In the paper, a heterojunction catalyst is constructed that adopts NH2-MIL-125 and Fe-doped W18O49 (Fe-W18O49) for photocatalytic nitrogen fixation. Fe-W18O49 is a nanowire containing oxygen vacancies (OVs). OVs can provide active sites for the adsorption and activation of nitrogen gas. The 3D plate-like morphology of NH2-MIL-125 can observably reduce the occurrence of nanowires aggregation. This phenomenon can be attributed to NH2-MIL-125 playing a supporting role in the fixation of nanowires. New mesoporous are formed between NH2-MIL-125 and Fe-W18O49 in the constructed compound catalyst, which can realize efficient mass transfer between the inside and outside of the catalyst. EPR characterization discovers that Fe-W18O49/NH2-MIL-125 cannot produce •O2˗ and •OH radicals. The type II heterojunction forms between Fe-W18O49 and NH2-MIL-125. The heterojunction improves the carrier migration path, and the photocurrent intensity is significantly increased. Under simulated sunlight, Fe-W18O49/NH2-MIL-125–2 emerges the best catalytic performance with an ammonia formation rate of 128.2 µmol g−1 h−1. The yield of ammonia is boosted in comparing with NH2-MIL-125 (13 times) and Fe-W18O49 (1.7 times). After several cycles, Fe-W18O49/NH2-MIL-125 remain maintains good stability during the catalytic process. This paper provides a possibility for constructing low-cost heterojunction catalysts in the territory of photocatalytic nitrogen fixation.

Tuning excited-state electronic structure in tungsten oxide for enhanced nitrogen photooxidation as fertilizer

Nitrate (NO3–) is an important raw ingredient for fertilizer, but its conventional synthesis is restricted by high energy consumption and CO2 emissions. Though there have been some studies on photocatalytic nitrogen oxidation, the production rate of nitrate is undesirable and the excited-state charge-transfer pathway still remains unclear. Herein, we fabricated the V-doped W18O49 nanowires (V- W18O49) for direct nitrate synthesis from N2 photooxidation. The NO3- production rate is as high as 39.85 μmol g−1 h−1 with exceptional catalytic stability and the photosynthetic nitrate fertilizer was employed to promote the growth of crops. Time-resolved spectroscopic results confirmed that the introduction of V doping in V- W18O49 has created new high-efficiency electron-transfer (ET) pathways from the W-O site to the V-dopant under photoirradiation, which leads to an improved π-backdonation process that facilitates nitrogen activation. This newly formed ET channel facilitated efficient charge separation and ultrafast photogenerated carriers transfer, thus overcame the sluggish ET kinetics.