Monoclinic WO3 Research Articles

WO2 nanoparticles with oxygen vacancies: a high-efficiency electrocatalyst for the conversion of nitrite to ammonia

Monoclinic WO2 nanoparticles with oxygen vacancies are efficient for electrochemical NO2− reduction to NH3, offering an NH3 yield rate of 14 964.25 ± 826.06 μg h−1 cm−2 and a faradaic efficiency of 94.32 ± 1.15%.

Nanocrystalline Surface Layer of WO3 for Enhanced Proton Transport during Fuel Cell Operation

High ionic conductivity in low-cost semiconductor oxides is essential to develop electrochemical energy devices for practical applications. These materials exhibit fast protonic or oxygen-ion transport in oxide materials by structural doping, but their application to solid oxide fuel cells (SOFCs) has remained a significant challenge. In this work, we have successfully synthesized nanostructured monoclinic WO3 through three steps: co-precipitation, hydrothermal, and dry freezing methods. The resulting WO3 exhibited good ionic conductivity of 6.12 × 10−2 S cm−1 and reached an excellent power density of 418 mW cm−2 at 550 °C using as an electrolyte in SOFC. To achieve such a high ionic conductivity and fuel cell performance without any doping contents was surprising, as there should not be any possibility of oxygen vacancies through the bulk structure for the ionic transport. Therefore, laterally we found that the surface layer of WO3 is reduced to oxygen-deficient when exposed to a reducing atmosphere and form WO3−δ/WO3 heterostructure, which reveals a unique ionic transport mechanism. Different microscopic and spectroscopic methods such as HR-TEM, SEM, EIS, Raman, UV-visible, XPS, and ESR spectroscopy were applied to investigate the structural, morphological, and electrochemical properties of WO3 electrolyte. The structural stability of the WO3 is explained by less dispersion between the valence and conduction bands of WO3−δ/WO3, which in turn could prevent current leakage in the fuel cell that is essential to reach high performance. This work provides some new insights for designing high-ion conducting electrolyte materials for energy storage and conversion devices.

Fabrication of high sensitive proto-type NOx sensor based on Pd nanoparticles loaded on WO3

Herein, we report, development of a proto-type NOx sensor using optimized Pd nanoparticles loaded WO3 (Pd@WO3). The WO3 powder was synthesized hydrothermally using sodium tungstate dihydrate and adipic acid as precursors. The structural and morphological analyses of as-prepared samples were performed using XRD, FESEM and FETEM analysis. The results revealed the formation of irregular shaped monoclinic WO3 particles decorated with Pd nanoparticles of ~10–15 nm size. The NOx sensing characterization of WO3 and Pd@WO3 was performed at different ppm levels and at different temperature. The WO3 nanostructures were found to exhibit maximum response towards NOx gas at room temperature which enhances drastically after Pd loading. The NOx sensor device has been fabricated using optimized Pd loaded WO3 material which showed higher % response towards NOx. The response and recovery time observed were 1 and 2 s respectively. The cross sensitivity observed for other gases and organic vapors was negligible.

Tungsten Trioxide Photoanode-Palladium Cathode Cell for Solar Seawater Splitting

N-type semiconductor-tungsten trioxide (WO3) finds application in a large variety of fields including photocatalysis, gas sensors, smart windows or as a substrate for heterogeneous catalysts. This presentation will focus on recent improvements in optoelectronic and photoelectrochemical (PEC) properties of WO3 thin films achieved in our laboratory. The semitransparent WO3 films are formed on F-doped tin oxide (FTO) conductive glass substrates, using a sol-gel method, by depositing the precursor layer-by-layer and annealing sequentially in the flow of oxygen. Use of appropriate mixtures of tungstic acid and organic structure-directing agents that form the WO3 film precursor, combined with a two-step annealing, allows the formation of highly crystalline nanostructured (NS) electrodes with controlled, large porosity. This renders possible the permeation of the whole mesoporous film by the electrolyte. Annealing of the as-deposited samples in oxygen above 500°C ensures structural ordering with formation of monoclinic WO3. Since none among photostable (metallic oxide) semiconductors exhibits band-edge energy levels that match those of hydrogen and oxygen evolution reactions to allow unassisted water splitting, the present efforts focus on minimizing the bias voltage required to perform visible light-driven photooxidation of water. In fact, a bias voltage of the order of 1 V may be provided by several single-junction PV cells likely to operate in a tandem device with the PEC cell. Despite visible-light absorption range of the WO3 films restricted to 500 nm, under standard conditions, i.e. at 1.23 V vs RHE and under simulated AM 1.5G solar light (100 mW/cm2), stable anodic water splitting photocurrents exceeding 4.5 mA/cm2 are regularly attained.This presentation will principally focus on photoelectrolysis experiments employing synthetic seawater electrolyte, in a two compartment (separated by a sintered glass diaphragm) cell, that showed dominant (with 60-70% Faradaic efficiency) formation of chlorine at the WO3 photoanode with remarkably stable photocurrents reaching 4.7 mA/cm2. In fact, as demonstrated in an earlier work from our laboratory1, the WO3 photoelectrodes exhibit preferentially oxidation of anions (including Cl-) of the acidic aqueous electrolytes. However, in contrast with the Cl- ions, the photooxidation of oxy-anions of acidic electrolytes leads generally to the "passivation" of the WO3 electrodes due to the formation of the surface layers of peroxo species.1 The only identified exception is the methane-sulfonic acid that allows oxygen generation at the WO3 photoanode with large stable photocurrents.2 In the case of seawater photoelectrolysis, the operating potential point at which the photocurrent approaches saturation occurs at ca 0.4 V below E(Cl-/Cl2)=1.36 V vs SHE. Consistently, the incident photon conversion efficiencies (IPCEs) reach a maximum of 85% over 390-410 nm range of wavelengths.3 Good mechanical and chemical stability of the WO3 electrodes in the presence of chlorine evolved from seawater was confirmed by monitoring the photocurrents over a 20 hours-long continuous photoelectrolysis runs.A schematic diagram of the seawater splitting PEC cell, including a NS WO3 film photoanode and a Pd sheet cathode, used in our experiments is shown below.Fig. 1 Schematic diagram of the seawater splitting PEC cell.The current of CO2 gas passing through the seawater represents a possible option for maintaining slightly acidic pH in the cathodic cell compartment. The important advantage of the adopted PEC cell configuration is to circumvent the problem of gas separation, i.e. chlorine/oxygen formed at the photoanode and hydrogen generated at the Pd cathode that is stored in the form of a Pd-H hydride. The storage of hydrogen generated in a PEC water splitting device in the form of a hydride, opens the possibility of its subsequent use as an anode in a hydride-oxygen battery.Such sunlight-driven PEC seawater splitting device can be implemented in remote places to provide on-site relatively small amounts of chlorine for disinfecting purposes including purification of drinking water.More generally, the prospect of using seawater electrolyte for a larger scale PEC hydrogen generation would release the strain on vital fresh water resources. Considering relatively low concentration of Cl- ions in seawater, roughly equivalent to 0.5 M NaCl, the photoelectrolysis delivering photocurrents in the range of mA/cm2 appears well suited for such applications.

Effect of reaction parameters on WOx nanostructures by the solvothermal process

In this work, nanowires and nanorods of WOx have been synthesized by the solvothermal method. The effect of reaction time and acetic acid as solvent were studied. X-ray diffraction (XRD) patterns showed the monoclinic WO2.72, WO2.79, and orthorhombic WO3 crystalline structures. Scanning Electron Microscopy (SEM) and High-Resolution Transmission Electronic Microscopy (HRTEM) images presented nanostructures such as nanowires and nanorods at different sizes. Band gap energies were supplied by Ultra Violet visible (UV-vis) absorption spectra. The Photoluminescence (PL) spectra exhibited three emission peaks in the blue zone at 440, 460, and 484 nm. X-ray Photoelectron Spectroscopy (XPS) was used to calculate W6+, W5+, and W4+ oxidation states. The results showed that increasing the reaction time from 10 h to 24 h affected the crystalline structure from monoclinic to orthorhombic. Moreover, with the addition of acetic acid as solvent, the crystal structure is not affected but stabilizes the monoclinic phase in the course of time.

Controlled Growth of WO3 Pyramidal Thin Film via Hot-Filament Chemical Vapor Deposition: Electrochemical Detection of Ethylenediamine

In this work, the structural, optical, morphological, and sensing features of tungsten oxide (WO3) thin film deposited on a silicon substrate via hot-filament chemical vapor deposition (HFCVD) are described. The experimental characterization tools, such as X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), ultraviolet-visible (UV-Vis), and Fourier transform infra-red (FTIR) spectroscopies, etc., were used to determine the properties of WO3 NPys thin films. The grown WO3 thin film illustrated closely packed porous pyramidal nanostructures (NPys) of improved grain size properties. The diffraction analysis revealed (100) and (200) of WO3 phases, suggesting the classic monoclinic crystal WO3 structure. HFCVD grown WO3 NPys thin film was employed as electro-active electrode for detecting ethylenediamine in 10 mL of 0.1 M phosphate buffer solution (PBS) by varying the ethylenediamine concentrations from 10 μM to 200 μM at room temperature. With a detection of limit (LOD) of ~9.56 μM, and a quick reaction time (10 s), the constructed chemical sensor achieved a high sensitivity of ~161.33 μA μM−1 cm−2. The durability test displayed an excellent stability of electrochemical sensor by maintaining over 90% sensitivity after 4 weeks of operation. This work provides a strategy for a facile preparation of WO3 NPys thin film electrode for sensor applications.

Crystallite Size on Micromechanical Characteristics of WO3 Microparticles

This study evaluated the relationship between crystallite size and micromechanical characteristics of micrometersized monoclinic WO3 particles. To avoid the existence of other parameters in the measurement (such as impurities and porous structure in the particle), micrometer WO3 particles were prepared using a direct heat treatment of ultrapure micrometer-sized ammonium tungstate powders. The crystallite size was controlled independently in constant WO3 particle outer diameters to obtain a precise measurement result. The mechanical properties, i.e., hardness and Young’s modulus, were measured by load-controlled nanoindentation test on the singular WO3 particles. The force and displacement relationship data was plotted and analyzed to obtain the relationship between crystallite size and mechanical properties. The results revealed that the micromechanical properties of WO3 particles were strongly dependent on the crystallite size. The hardness and Young’s modulus values increased more than three times when increasing the crystallite size to about 40 nm. The study was completed with a proposed mechanism of crack propagation inside the particle due to static load. The study demonstrates the important role of crystallite size in determining the micromechanical characteristics of WO3 particles. The result is useful especially when utilizing WO3 microparticles for various processes involving extreme conditions, such as high pressure reaction.

Enhanced optoelectronic functionality of N + H codoped monoclinic WO3: A hybrid functional study

N + H co-doping in monoclinic WO 3 has been systematically investigated using the Heyd-Scuseria-Enrzerhof hybrid functional. Results show that N and H tend to stay nearest to each other to form a N H cluster, inducing a dispersive and occupied intermediate band within the band gap of WO 3 . The presence of this intermediate band makes the band gap narrowed by 24%, leading to a remarkable redshift of the optical absorption edge. Simultaneously, the high carrier mobility is beneficial for the electron excitation, also contributable to the enhancement in the photoabsorption of WO 3 . Especially, the N H bond length is very close to that in NH 3 , suggesting that it is likely to utilize NH 3 to dope WO 3 for improved optoelectronic performance. The thermodynamic and kinetic stabilities of the N H cluster in WO 3 have been addressed in details. This work has implications in optimizing the optoelectronic functionality of WO 3 -based materials for environmentally friendly applications.

Structure and Thermal Transformations of Methylammonium Tungstate

AbstractMethylammonium paradodecatungstate, (CH3NH3)10[H2W12O42] ⋅ nH2O, was prepared by the reaction of WO3 or H2WO4 in aqueous methylamine, followed by drying. The [H2W12O42]10− anion consists of two HW3O13 groups containing three edge‐sharing WO6 octahedra and two W3O14 groups having two edge‐sharing connections. On drying the produced material at 70 °C, some lattice water was released, but this did not affect the [H2W12O42]10− structure, although there was a decrease in the unit cell volume. By adding water, the loss of lattice water and structural changes were reversed. The existence of paradodecatungstate anions was confirmed by single‐crystal and powder X‐ray diffraction, Fourier transform infrared, Raman, 183W nuclear magnetic resonance, and ultraviolet‐visible spectroscopy. When the methylammonium paradodecatungstate was heated to more than 150 °C, CH3NH2 and H2O were released, and amorphous WO3 was observed as an intermediate product and monoclinic WO3 as the final product. These results reveal the structure of methylammonium tungstate, which was first reported in 1909 and now is used as an important negative staining reagent for virus observation, is methylammonium paradodecatungstate.

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.

Facile synthesis of in situ CNT/WO3∙H2O nanoplate composites for adsorption and photocatalytic applications under visible light irradiation

Composites of refluxed carbon nanotubes (CNTs) at different contents and orthorhombic tungsten oxide hydrate (WO3∙H2O) were prepared via acid precipitation at room temperature. The CNTs produced a new phase of monoclinic tungsten oxide dihydrate WO3∙2H2O, caused the breakage of WO3∙H2O nanoplates, and affected the microstrain in the nanocomposites. The CNTs also enhanced the absorbance in the visible range and increased the specific surface area and pore volume but abnormally enlarged the optical bandgap, which was assigned to the emerging monoclinic WO3∙2H2O phase. The adsorptivity and photocatalytic activity of the nanocomposites increased remarkably with CNT content. H2O2 strongly enhanced the photocatalytic activity of the pristine and nanocomposite samples, implying the vital role of photogenerated electrons in the photocatalytic process. Among the synthesized samples, the sample with 20 wt.% CNTs showed the highest adsorptivity and photocatalytic efficiency under visible light irradiation. It also exhibited good reusability in methylene blue degradation and applicability in degrading different organic dyes. This study presents a simple method to prepare CNT@WO3∙H2O nanocomposites with a large surface area, a high adsorptivity, and a high photocatalytic activity under visible light irradiation.

Effect of reaction time on the phase transformation and photocatalytic activity under solar irradiation of tungsten oxide nanocuboids prepared via facile hydrothermal method

ABSTRACT Monoclinic WO3 nanocuboids were synthesized via a one-pot hydrothermal method in a highly acidic environment at 180°C for different reaction times (12, 24, and 48 h). The phase transformation from orthorhombic to monoclinic and then to oxygen-deficient Magnéli phase and an increase in optical bandgap from 2.43 to 2.70 eV were observed when the reaction time increased from 12 to 24 h and then to 48 h. All samples showed photocatalytic activity towards the degradation of methylene blue (MB) under solar light irradiation, which was strongly enhanced in the presence of hydrogen peroxide (H2O2). Sample prepared for 24 h showed the highest MB removal efficiency of 31.4% in the absence of H2O2, which was enhanced to 76% and 92% when adding 0.2 and 0.5 mL of H2O2, respectively. These results give insights into the phase transformation and photocatalytic mechanism of WO3 nanocuboids prepared via the hydrothermal method.

Synthesis, crystal structure and properties of hepta(ammonium) penta(1H-imidazol-3-ium) paratungstate B tetrahydrate

An attempted isolation of the elusive diammonium tetraoxidotungstate (NH4)2[WO4] as its imidazole (Im) adduct resulted in the serendipitous formation of hepta(ammonium) penta(1H-imidazol-3-ium) paratungstate B tetrahydrate having formula [NH4]7[ImH]5[W12O42]·4H2O (1). The synthesis, vibrational spectra, crystal structure and thermal study of the mixed cationic paratungstate tetrahydrate 1 are reported. The structure of 1 consists of a centrosymmetric paratungstate [W12O42]12– anion devoid of internal hydrogen atoms, which is charge balanced by ammonium and 1H-imidazol-3-ium cations. One of the four unique NH4 + cations and one of the three crystallographically independent 1H-imidazol-3-ium cations are disordered around a center of inversion. The cations, [W12O42]12– anion and the unique lattice water molecules are joined with the aid of five varieties of hydrogen bonding interactions. A comparative study of twenty-three partaungstates is described. Thermal decomposition of 1 results in the formation of monoclinic tungsten trioxide WO3.

Photocatalytic Activity of Cu2S/WO3 and Cu2S/SnO2 Heterostructures for Indoor Air Treatment.

Volatile organic compounds (VOCs) are commonly found in indoor spaces (e.g., homes or offices) and are often related to various illnesses, some of them with carcinogenic potential. The origins of VOC release in the indoor environment are in office products, building materials, electronics, cleaning products, furniture, and maintenance products. VOC removal can be done based on two types of technologies: adsorption in specific materials and decomposition via oxidative processes. The present article reports the development and photocatalytic activity of two heterostructures (Cu2S/WO3 and Cu2S/SnO2) used for indoor air decontamination. The acetaldehyde removal rate is discussed in correlation with the S-scheme mechanisms established between the heterostructure components but also comparatively with the bare catalysts’ activity. Acetaldehyde was considered as a VOC reference because it was found by the International Agency for Research on Cancer to be one of the most frequent air toxins with potential carcinogenic effects. The samples contained monoclinic WO3, tetragonal SnO2, and orthorhombic Cu2S crystalline structures. The Cu2S crystallite size in the heterostructure varied from 75.9 to 82.4 Å, depending on the metal oxide substrate. The highest photocatalytic efficiency (75.7%) corresponded to Cu2S/SnO2, with a constant rate of 0.106 s−1 (which was three times faster than WO3 or SnO2 and seven and a half times faster than Cu2S).

Effect of ferroelectric polarization field on different carrier migration in photoanode

Spontaneous polarization field in ferroelectric can improve the oxidation kinetics and photocurrent of a photoanode in photoelectrochemical water splitting. But the impact of ferroelectric polarization field on the migration of different charge carriers which have different mobility and diffusion length is still unknown. In this work, we synthesized tetragonal BaTiO3 nanoparticles by solvothermal method successfully and fabricated the hybrid photoanode composed by monoclinic WO3 and BaTiO3 for solar water oxidation. Density functional theory calculations showed that the mobility of electron was faster than that of the hole in WO3, and had a longer diffusion length. We demonstrated that the polarization field of ferroelectric had a greatly impact upon holes migration compared with electrons, thus the thin hybrid photoanode after poling by bias presented a significant improvement of photocurrent (210.5%) under the back-side illumination, and a remarkable augment of charge separation efficiency (94%) and oxidation kinetics (69%) at 1.23 V. Our work provided a deeper understanding of how ferroelectric polarization field affected the photoelectrochemical water oxidation and a general pathway towards enhancing minority carrier collection in photoanode.

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.

Nickel-doped monoclinic WO3 as high performance anode material for rechargeable lithium ion battery

• Monoclinic WO 3 nanoparticles are successfully doped by 10 wt% of Nickel element. • The N10mWO 3 delivers 1st /2nd discharge capacities of 1287/1012 mAh g −1 at 100 mA g −1 . • The N10mWO 3 exhibits the capacity retention of 79.60% at 100 mA g −1 after 500 cycles. • The N10mWO 3 shows high rate capability, 650.2 mAh g −1 even at 1000 mA g −1 . The anode materials are one of the critical components in rechargeable lithium ion batteries (LIBs). The monoclinic tungsten trioxide (mWO 3 ) is introduced as interesting anode electrode for LIBs due to its good structure for intercalation and de-intercalation of lithium ions, high abundance and various oxidation state of tungsten and etc. In this study, we prepare and investigate the effect of various amounts of nickel dopant on characteristics and electrochemical properties of the mWO 3 as the anode electrode in a rechargeable LIB. The experimental investigations confirm that the number of nickel atoms has a remarkable effect on controlling spherical particle diameter, crystallite size, and electrochemical properties of mWO 3 . The electrochemical results demonstrate that the 10 wt% nickel dopant leads to make the highest improvements for electrochemical behaviors of mWO 3 . The sample exhibits higher 1 st /2 nd electrochemical capacities (1287/1012 mAh g −1 at 100 mA g −1 ), good cycle life (capacity retention of 79.60% after 500 cycles at 100 mA g −1 ), and better rate capability (650.2 mAh g −1 even at 1000 mA g −1 ) among un-doped and doped mWO 3 samples, including 5 and 20 wt% nickel atoms. These improvements can be related to the spherical morphology of nanoparticles and high electrical conductivity making by nickel dopant, which is beneficial to enhance lithium-ion diffusion and electron transfer in the monoclinic structure of WO 3 . The anode electrode reported here exhibits excellent properties in LIBs for various energy storage applications..

Tuned S-Scheme Cu2S_TiO2_WO3 Heterostructure Photocatalyst toward S-Metolachlor (S-MCh) Herbicide Removal.

A dual S-scheme Cu2S_TiO2_WO3 heterostructure was constructed by sol–gel method using a two-step procedure. Due to the synthesis parameters and annealing treatment the heterostructure is characterized by sulfur deficit and oxygen excess allowing the passivation of oxygen vacancies. The photocatalytic activity was evaluated under UV and UV–Vis irradiation scenarios using S-MCh as reference pollutant. The heterostructure is composed on orthorhombic Cu2S, anatase TiO2 and monoclinic WO3 with crystallite sizes varying from 65.2 Å for Cu2S to 97.1 Å for WO3. The heterostructure exhibit a dense morphology with pellets and particle-like morphology closely combined in a relatively compact assembly. The surface elemental composition indicate that the heterostructure maintain a similar atomic ratio as established during the synthesis with a slight sulfur deficit due to the annealing treatments. The results indicate that the three-component heterostructure have higher photocatalytic efficiency (61%) comparing with two-component heterostructure or bare components. Moreover, Cu2S_TiO2_WO3 exhibit a superior constant rate (0.114 s−1) due to the high concentration of photogenerated charge carriers, efficient charge separation and migration.

Synthesis of tungsten oxide/ amino-functionalized sugarcane bagasse derived-carbon quantum dots (WO3/N-CQDs) composites for methylene blue removal

In this present study, the tungsten oxide/amino-functionalized sugarcane bagasse derived-carbon quantum dots (WO3/N-CQDs) composite has successfully been prepared through a simple mixing process. The WO3 was synthesized through a precipitation method, and CQDs were amino-functionalized using ethylenedinitrilotetraacetic acid (EDTA) and ethylenediamine (EDA) through one-pot hydrothermal method. It is revealed that N-CQDs incorporation into WO3 alters the bandgap energy, crystallinity, surface area, and photoluminescence (PL) properties. The produced composites exhibit higher monoclinic WO3 crystallinity, larger surface area, lower bandgap energy and quenched photoluminescence intensity. The as-prepared WO3/N-CQDs composites exhibit better adsorption and photocatalytic degradation performance of methylene blue (MB) than the pristine WO3. It shows that the combination of N-CQDs and WO3 enhanced visible light absorption, by lowering the bandgap energy of WO3 from 2.175 to 1.495 eV. The best performance composite is WO3/N-CQDs EDA 2.5% with an efficiency of 96.86%, removal rate constant of 0.02017/min, and chemical oxidation demand (COD) removal efficiency achieved 84.61%. Moreover, the WO3/N-CQDs EDA 2.5% shows a significant photocatalytic activity even at higher MB initial concentration with 92.93% removal for 50 ppm MB. Subsequently, the composite also has good stability after a sequential 3-times cycle of degradation with 86.85% removal. The increasing photocatalytic performance is affected by the quenching effect of PL and lower bandgap energy. The lower intensity of the PL indicates the reduced charge carrier recombination resulting in increased photocatalytic activity. The combination of N-CQDs and WO3 resulted in improved photodegradation, which shows its significant potential to be utilized for wastewater treatment.

Fabrication of two-phase WO3 nanorod photoelectrode and its enhanced photoinduced cathodic protection performance

In this paper, two-phase WO3 photoelectrodes with different morphologies were obtained by controlling the concentration of Na2WO4 in the precursor solution, and their photoinduced cathodic protection(CP) performance was explored. The heterojunctions formed between hexagonal and monoclinic WO3 are favorable for the directional separation of photogenerated carriers. Meanwhile, the ordered growth of WO3 nanorods perpendicular to Ti substrate is conducive to the directional transmission of photogenerated carriers, which makes it have good photoinduced CP performance.