Figure 1 - uploaded by Daniel Duprez
Content may be subject to copyright.
![Structure of hexagonal WO3 (a) and monoclinic WO3 (b) projected along the (001) direction. Reprinted from Sun et al. [19] with permission from the American Chemical Society.](profile/Daniel-Duprez-2/publication/352077471/figure/fig1/AS:1030456761937921@1622691445469/Structure-of-hexagonal-WO3-a-and-monoclinic-WO3-b-projected-along-the-001.png)
Structure of hexagonal WO3 (a) and monoclinic WO3 (b) projected along the (001) direction. Reprinted from Sun et al. [19] with permission from the American Chemical Society.
Source publication
This review aims to give a general overview of the recent use of tungsten-based catalysts for wide environmental applications, with first some useful background information about tungsten oxides. Tungsten oxide materials exhibit suitable behaviors for surface reactions and catalysis such as acidic properties (mainly Brønsted sites), redox and adsor...
Contexts in source publication
Context 1
... et al. recently compared the potentialities of monoclinic WO3 (m-WO3) and hexagonal WO3 (h-WO3) in electrochemical and gas adsorption applications [19]. The structures of the two forms of WO3 are represented in Figure 1. [19] with permission from the American Chemical Society. ...
Context 2
... sites were monitored by pyridine adsorption, which can lead to four species: LPy (Lewis acid bound Py), BPy (Brønsted acid bound Py), HPy (hydrogen-bonded Py) and PPy (physically adsorbed Py). FTIR spectra of adsorbed pyridine were recorded at room temperature ( Figure 10) and after desorption at 100, 200 and 300 °C. . FTIR spectra of adsorbed pyridine at room temperature on Al2O3 (Al), TiO2 (Ti), SiO2 (Si) and 10%WO3 on these supports (code: WAl, WTi and WSi, respectively). ...
Context 3
... their study on WO3/SiO2 catalysts (0 to 11.7 wt.% W on a silica of 200 m 2 g −1 , i.e., 0 to 2.4 W nm −2 ), Chauvin et al. monitored the acidity of the samples by FTIR spectroscopy of adsorbed 2,6-dimethylpyridine (lutidine) [52]. The spectra reported in Figure 11a show the presence of Brønsted sites (bands at 1643 and 1630 cm −1 ). Lewis sites that should give bands at 1620-1600 cm −1 are clearly absent from the samples. ...
Context 4
... sites that should give bands at 1620-1600 cm −1 are clearly absent from the samples. Amounts of Brønsted sites linearly increase with the WO3 surface density up to 1.5 W nm −2 (Figure 11b). The acidity of WO3/SBA-15 oxides was characterized by Hu et al. using pyridine adsorption, solid-state NMR and quantum chemistry calculation [89]. ...
Context 5
... lutidine adsorption and other spectroscopic investigation, Chen et al. obtained precise information about the change in acid site concentration with respect to the W surface density [54]. Their results are summarized in Figure 12, which shows that monomeric tungsten species contain quasiexclusively Lewis acid sites, while Brønsted sites are relatively abundant on polymeric species appearing for W density above 1.4 W nm −2 . ...
Context 6
... acid properties of WO3-Al2O3 catalysts were recently revisited by Kitano et al., who showed that the formation of Brønsted sites depended on the temperature of calcination [98]. They proposed that Brønsted sites are predominantly located at the boundaries between WO3 monolayer domains ( Figure 13). Potassium-doped WO3/Al2O3 catalysts are able to transform gas mixtures such as CO2/H2S/H2, methanol/H2S or CH4/H2S/CO2 into valuable products such as methyl mercaptan (CH3SH) [99][100][101]. ...
Context 7
... nanoparticles used in bifunctional Pt/WO3-ZrO2 catalysts would also be a source of Brønsted site by H spillover between Pt and WO3 [112]. The surface chemistry and acidity of WO3-ZrO2 catalysts for skeletal isomerization of alkanes were discussed by Di Gregorio and Keller, who suggested that a condensation phenomenon between Lewis and Brønsted sites can occur during the calcination treatment [113] (Figure 14). ...
Context 8
... et al. also showed by different techniques (e.g., Raman spectroscopy, EPR, H2-TPR) that tungsten allowed an increase in V-O-V species by confining vanadia in small clusters [128]. Most of these effects were confirmed and detailed in a recent review by Lai and Wachs [129], who stressed three important features of the reaction: (i) the role of V 5+ surface species as active sites: WO3 is not active per se but promotes the reaction by vanadia by formation of oligomeric vanadia (V2O5) sites or crowding; (ii) the specific role of Brønsted acid sites in NH3 activation: most of the Lewis sites are converted to Brønsted sites in the presence of moisture at 250 °C; (iii) the detailed mechanisms reported by Topsoe and Dumesic et al. in the 1990s for V2O5-TiO2 [130,131] (see Figure 15) seemed to be still valid in the 2010s for V2O5-WO3/TiO2, as also recently summarized by Han et al. [132]. This mechanism, however, contrasts with the amide-nitrosamide mechanism proposed by Lietti et al. [133] in which NH3 is predominantly activated on Lewis sites as amide species (Equation (2)). ...
Context 9
... commercial catalyst named VSCR1 has been compared to a catalyst doped with 4-5% SiO2, named VSCR2. Figure 16 shows the global behavior of the two catalysts when they are calcined at 600, 700 and 800 °C. A dramatic improvement of the catalyst stability is obtained by Si doping. ...
Context 10
... pretreated in an acidic medium seem to give good impregnation characteristics [154]. The fabrication process is illustrated in Figure 17. Best results in NH3-SCR were obtained with the monolith impregnated three times with 3% V + 10% W. It is dried at 80 °C and calcined at 500 °C. ...
Context 11
... catalysts were prepared with 10% WO3 and various loadings of ceria (from 0 to 40%). DeNOx activity of these materials is visualized in Figure 18. The catalyst with 20% CeO2 shows the best performance in NH3-SCR. ...
Context 12
... et al. compared the behavior of ceria doped with various acid promoters: phosphotungstic, silicotungstic and phosphomolybdic acids or ammonium sulfate [219]. Ceria doped with phosphotungstic (CeO2-P-W) or silicotungstic acid (CeO2-Si-W) showed the highest NOx conversion (Figure 19). However, CeO2-P-W exhibited the best N2 selectivity over the whole temperature range, especially at T > 450 °C where N2O could be formed. ...
Context 13
... two catalysts (MnOx-CeO2/TiO2 (MnCeTi) and V2O5-WO3/TiO2 (VWTi)), Zhang et al. were able to obtain high NO conversion from 150 to 400 °C [253]. The best configuration was obtained when VWTi was set at the fore part and MnCeTi at the rear part of the catalyst bed ( Figure 21, CC-B curve). MnCeTi is much more active than VWTi for the NO oxidation reaction, allowing work in fast SCR conditions over a wide range of temperatures. ...
Context 14
... is proposed that Ag and AgCl greatly promoted the separation of photogenerated electron-hole pairs and improved the charge transfer efficiency of WO3. Based on the photoelectrochemical test and radical trapping measurement, a Z-scheme mechanism for WO3/Ag/AgCl is proposed where •O2 -and h + play the major roles in photodegradation, while the effect of OH• could be neglected (Fig- ure 31a). Consequently, Z-scheme composite photocatalysts have to be considered as an effective way to enhance the photocatalytic performance of catalysts. ...
Context 15
... et al. [385] proposed plasmonic Ag/Ag2WO4/WO3 Z-scheme visible-light composite photocatalyst for the degradation of rhodamine B, methylene blue and methyl orange. A possible Z-scheme mechanism of the ternary composite was proposed under visible light where Ag particles produce SPR effect but also work as the charge transmission bridge (Figure 31b). Sahoo et al. [386] designed a Z-scheme WO3−X-Ag-ZnCr layered double hydroxide (LDH) photocatalyst for tetracycline degradation, based on the SPR effect of metallic Ag as redox electron mediator. ...
Context 16
... et al. recently compared the potentialities of monoclinic WO3 (m-WO3) and hexagonal WO3 (h-WO3) in electrochemical and gas adsorption applications [19]. The structures of the two forms of WO3 are represented in Figure 1. [19] with permission from the American Chemical Society. ...
Context 17
... sites were monitored by pyridine adsorption, which can lead to four species: LPy (Lewis acid bound Py), BPy (Brønsted acid bound Py), HPy (hydrogen-bonded Py) and PPy (physically adsorbed Py). FTIR spectra of adsorbed pyridine were recorded at room temperature ( Figure 10) and after desorption at 100, 200 and 300 °C. . FTIR spectra of adsorbed pyridine at room temperature on Al2O3 (Al), TiO2 (Ti), SiO2 (Si) and 10%WO3 on these supports (code: WAl, WTi and WSi, respectively). ...
Context 18
... their study on WO3/SiO2 catalysts (0 to 11.7 wt.% W on a silica of 200 m 2 g −1 , i.e., 0 to 2.4 W nm −2 ), Chauvin et al. monitored the acidity of the samples by FTIR spectroscopy of adsorbed 2,6-dimethylpyridine (lutidine) [52]. The spectra reported in Figure 11a show the presence of Brønsted sites (bands at 1643 and 1630 cm −1 ). Lewis sites that should give bands at 1620-1600 cm −1 are clearly absent from the samples. ...
Context 19
... sites that should give bands at 1620-1600 cm −1 are clearly absent from the samples. Amounts of Brønsted sites linearly increase with the WO3 surface density up to 1.5 W nm −2 (Figure 11b). The acidity of WO3/SBA-15 oxides was characterized by Hu et al. using pyridine adsorption, solid-state NMR and quantum chemistry calculation [89]. ...
Context 20
... lutidine adsorption and other spectroscopic investigation, Chen et al. obtained precise information about the change in acid site concentration with respect to the W surface density [54]. Their results are summarized in Figure 12, which shows that monomeric tungsten species contain quasiexclusively Lewis acid sites, while Brønsted sites are relatively abundant on polymeric species appearing for W density above 1.4 W nm −2 . ...
Context 21
... acid properties of WO3-Al2O3 catalysts were recently revisited by Kitano et al., who showed that the formation of Brønsted sites depended on the temperature of calcination [98]. They proposed that Brønsted sites are predominantly located at the boundaries between WO3 monolayer domains ( Figure 13). Potassium-doped WO3/Al2O3 catalysts are able to transform gas mixtures such as CO2/H2S/H2, methanol/H2S or CH4/H2S/CO2 into valuable products such as methyl mercaptan (CH3SH) [99][100][101]. ...
Context 22
... nanoparticles used in bifunctional Pt/WO3-ZrO2 catalysts would also be a source of Brønsted site by H spillover between Pt and WO3 [112]. The surface chemistry and acidity of WO3-ZrO2 catalysts for skeletal isomerization of alkanes were discussed by Di Gregorio and Keller, who suggested that a condensation phenomenon between Lewis and Brønsted sites can occur during the calcination treatment [113] (Figure 14). ...
Context 23
... et al. also showed by different techniques (e.g., Raman spectroscopy, EPR, H2-TPR) that tungsten allowed an increase in V-O-V species by confining vanadia in small clusters [128]. Most of these effects were confirmed and detailed in a recent review by Lai and Wachs [129], who stressed three important features of the reaction: (i) the role of V 5+ surface species as active sites: WO3 is not active per se but promotes the reaction by vanadia by formation of oligomeric vanadia (V2O5) sites or crowding; (ii) the specific role of Brønsted acid sites in NH3 activation: most of the Lewis sites are converted to Brønsted sites in the presence of moisture at 250 °C; (iii) the detailed mechanisms reported by Topsoe and Dumesic et al. in the 1990s for V2O5-TiO2 [130,131] (see Figure 15) seemed to be still valid in the 2010s for V2O5-WO3/TiO2, as also recently summarized by Han et al. [132]. This mechanism, however, contrasts with the amide-nitrosamide mechanism proposed by Lietti et al. [133] in which NH3 is predominantly activated on Lewis sites as amide species (Equation (2)). ...
Context 24
... commercial catalyst named VSCR1 has been compared to a catalyst doped with 4-5% SiO2, named VSCR2. Figure 16 shows the global behavior of the two catalysts when they are calcined at 600, 700 and 800 °C. A dramatic improvement of the catalyst stability is obtained by Si doping. ...
Context 25
... pretreated in an acidic medium seem to give good impregnation characteristics [154]. The fabrication process is illustrated in Figure 17. Best results in NH3-SCR were obtained with the monolith impregnated three times with 3% V + 10% W. It is dried at 80 °C and calcined at 500 °C. ...
Context 26
... catalysts were prepared with 10% WO3 and various loadings of ceria (from 0 to 40%). DeNOx activity of these materials is visualized in Figure 18. The catalyst with 20% CeO2 shows the best performance in NH3-SCR. ...
Context 27
... et al. compared the behavior of ceria doped with various acid promoters: phosphotungstic, silicotungstic and phosphomolybdic acids or ammonium sulfate [219]. Ceria doped with phosphotungstic (CeO2-P-W) or silicotungstic acid (CeO2-Si-W) showed the highest NOx conversion (Figure 19). However, CeO2-P-W exhibited the best N2 selectivity over the whole temperature range, especially at T > 450 °C where N2O could be formed. ...
Context 28
... two catalysts (MnOx-CeO2/TiO2 (MnCeTi) and V2O5-WO3/TiO2 (VWTi)), Zhang et al. were able to obtain high NO conversion from 150 to 400 °C [253]. The best configuration was obtained when VWTi was set at the fore part and MnCeTi at the rear part of the catalyst bed ( Figure 21, CC-B curve). MnCeTi is much more active than VWTi for the NO oxidation reaction, allowing work in fast SCR conditions over a wide range of temperatures. ...
Context 29
... is proposed that Ag and AgCl greatly promoted the separation of photogenerated electron-hole pairs and improved the charge transfer efficiency of WO3. Based on the photoelectrochemical test and radical trapping measurement, a Z-scheme mechanism for WO3/Ag/AgCl is proposed where •O2 -and h + play the major roles in photodegradation, while the effect of OH• could be neglected (Fig- ure 31a). Consequently, Z-scheme composite photocatalysts have to be considered as an effective way to enhance the photocatalytic performance of catalysts. ...
Context 30
... et al. [385] proposed plasmonic Ag/Ag2WO4/WO3 Z-scheme visible-light composite photocatalyst for the degradation of rhodamine B, methylene blue and methyl orange. A possible Z-scheme mechanism of the ternary composite was proposed under visible light where Ag particles produce SPR effect but also work as the charge transmission bridge (Figure 31b). Sahoo et al. [386] designed a Z-scheme WO3−X-Ag-ZnCr layered double hydroxide (LDH) photocatalyst for tetracycline degradation, based on the SPR effect of metallic Ag as redox electron mediator. ...
Citations
... These properties make tungsten-based catalysts an attractive option for various catalytic applications. (2.6-2.8 eV band gap) [24][25][26] . However, because of the different solubility of tungstate anion and organic materials a phase transfer catalyst is necessary for these organic reactions. ...
An acidic tungstate-based zwitterionic organosilica drived simple self-condensation of tungstic acid and zwitterionic organosilane (PMO-IL-WO4²⁻), was remarkably demonstrated to be highly efficient and environmentally friendly catalyst for directly selective synthesis of benzimidazoles from benzyl alcohols under atmpshpheric air pressure and without any additional oxidant. The one-pot synthesis of benzimidazoles from benzyl alcohols and 1,2-phenylenediamine was efficiently achieved via direct dehydrogenative reaction using a low amount of recoverable PMO-IL-WO4²⁻ nanocatalyst in water under ambient conditions with a conversion efficiency of more than 90%. Enhancements in yield and selectivity of benzimidazole formation were observed when water was utilized as the solvent. Furthermore, the PMO-IL-WO4²⁻ nanocatalyst exhibited exceptional stability, demonstrating the ability to be effortlessly separated and reused for at least eight reaction cycles without any noticeable loss in activity or product selectivity. This method supports an eco-friendly atom economy and provides a sustainable approach to accessing benzimidazoles directly from benzyl alcohols under mild conditions, demonstrating its potential for practical applications in organic synthesis.
... This work directly addressed this need by presenting a novel route for W 2 N decomposition, which overcame the drawbacks of particle coarsening originating from intermediate species [26]. Our findings not only offer potential improvements in the densification of tungsten but also open doors for applications demanding a high surface area and precise control over tungsten nanostructures, for instance, in the fields of catalysis [27], nanocomposites [28], and microelectronics [29]. Importantly, further exploration of this method and optimizing reaction parameters and precursor properties hold immense promise for developing an even more efficient and scalable synthesis of fine-grained tungsten. ...
A facile, one-step nitridation–decomposition method was developed for the synthesis of nanosized tungsten powder with a high surface area. This approach involved the nitridation of WO3 in NH3 to form mesoporous tungsten nitride (W2N), followed by in situ decomposition of W2N to directly yield single-phase W particles. The phase and morphology evolution during the synthesis were systematically investigated and compared with the carbothermal reduction of WO3. It was revealed that powdered tungsten product with single-phase particles was obtained after nitridation at 800 °C combined with in situ decomposition at 1000 °C, displaying an average particle size of 15 nm and a large specific surface area of 6.52 m2/g. Furthermore, the proposed method avoided the limitations associated with intermediate phase formation and coarsening observed in carbothermal reduction, which resulted in the growth of W particles up to ~4.4 μm in size. This work demonstrates the potential of the nitridation–decomposition approach for the scalable and efficient synthesis of high-quality, fine-grained tungsten powder.
... The O-O deformation and W-O deformation modes, respectively, were ascribed to the comparatively high peak at a low frequency of 136 cm − 1 and the weak band at 327 cm − 1 , indicating the anisotropic atoms aligning on the surface of nano-pellets. [39] Fig. 2(c) shows the results of a study into the optical absorption characteristics of WO 3 NP using UV-visible spectroscopy (Shimadzu UV-3600 Spectrophotometer) in the 300-800 nm range at room temperature. We have analysed the spectrum obtained to acquire the band-gap energy (E bg ) of the WO 3 NP. ...
... In addition, tungsten is chosen for this study because of its capability to form various oxides differing in stoichiometry and crystalline structure for various temperature and pressure combinations [22]. This aspect is promising considering the potential catalytic and wettability applications associated with various types of tungsten oxides [23,24]. ...
Despite ultrafast laser-induced topography modification becoming a recognized surface texturing technique in the recent years, comparatively little work has focused on the accompanying chemical alterations. This study aims to fill that gap by investigating the oxidation induced by ultrafast laser irradiation of metals, with a specific focus on tungsten, in different environments: ambient and high vacuum (10-7 mbar). Laser irradiating conditions were chosen to generate so-called High Spatial Frequency Laser Induced Periodic Surface Structures with a sub-100 nm period and sub-20 nm amplitude, as they are supposed to arise in a non-ablative regime. Contact angle measurements, Scanning Transmission electron microscopy cross-sectional images, and x-ray photoelectron spectroscopy analyses were used to investigate the surface chemistry of these structures and reveal significant structural differences between the laser-generated oxides and those accumulated over time from ambient exposure. To establish an oxidation mechanism during laser interaction with tungsten, Two Temperature Model and Molecular Dynamics simulations (TTM-MD) were conducted to determine the temperature evolution over time. The simulation results, complemented by oxygen diffusion data, provide a predictive insight into the development of a thin oxide layer induced by laser irradiation, a conclusion substantiated by the STEM images. These findings suggest that oxidation can occur mostly by solid-state diffusion while the surface is still in the process of cooling down to room temperature following ultrafast photoexcitation.
... Figure 7c represents the single Si 2p peaks at 103.9 eV for pure SiO 2 , corresponding to Si 4+ [45]. The lattice oxygen species at ca. 531-532 eV [46] and the adsorbed water/hydroxyl species at ca. 532-533 eV [47] exhibited a negative shift to ~ 530.5 eV in the Fe-WO 3 /SiO 2 catalyst, as revealed in Fig. 7c ...
The enhancement of the photocatalytic performance of pristine WO 3 was systematically adjusted due to its fast recombination rate and low reduction potential. A designed heterostructure photocatalyst was necessarily synthesised by Fe ³⁺ metal ions doping into WO 3 structure with and composition modification. In this study, we synthesised a retrievable Fe-doped WO 3 /SiO 2 heterostructure using a surfactant-assisted hydrothermal method. This heterostructure was then employed as an effective photocatalyst for the removal of Cr(VI) under visible light irradiation. Enlarged photocatalytic reduction was observed over a synergetic 7.5 mol% Fe-doped WO 3 /SiO 2 -20 nanocomposite, resulting in dramatically increased activity compared with undoped WO 3 and SiO 2 nanomaterials under visible light illumination within 90 min. The presence of 7.5 mol% Fe ³⁺ ion dopant in WO 3 optimised electron–hole recombination, consequently reducing WO 3 photocorrosion. After adding SiO 2 nanoparticles, the binary WO 3 -SiO 2 nanocomposite played roles as both adsorbent and photocatalyst to increase specific surface area. Thus, the 7.5 mol% Fe-doped WO 3 /SiO 2 -20 nanocomposite catalyst had more active sites on the surface of catalyst, and enhanced photocatalytic reduction was significantly achieved. The results showed 91.1% photocatalytic reduction over the optimum photocatalyst, with a photoreduction kinetic rate of 21.1 × 10 –3 min ⁻¹ , which was approximately four times faster than pristine WO 3 . Therefore, the superior optimal photocatalyst demonstrated reusability, with activities decreasing by only 9.8% after five cycles. The high photocatalytic performance and excellent stability of our photocatalyst indicate great potential for water pollution treatments.
... Tungsten (W) is a transition metal commonly used as a catalyst [104]. Can et al. [105] reported that tungsten oxide is well-suited for catalysis and surface reactions, including redox and adsorption properties owing to the presence of oxygen vacancies as well as photo-stimulation response under visible light (the bandgap of tungsten oxide is equal 2.6-2.8 eV). ...
According to the sustainability concept, this work developed a green geopolymeric composite (Geo) prepared by mingling 50 wt% slag + 50 wt% brick-waste (BW) as an alternative eco-friendly and low-cost cementitious material. The main target of this study is to find a solution to the problem of poor characteristics of binding materials containing high proportions of BW; most previous studies recommended using only 10–20 wt% BW. The compressive-strength results showed that replacing slag with 50 wt% BW reduced the strength from 47 to 24.6 MPa at normal curing conditions for 28-days, referring to the detrimental impact of BW on mechanical performance. In an endeavour to enhance the mechanical performance of this composite, different doses from laboratory-prepared tungsten oxide nanoparticles (0.25, 0.5, 1 wt%WO3-NPs) and hydrothermal curing at various steam-pressure/periods were used. From an economic point of view, hydrothermally treated Geo-paste modified with 0.25 wt%WO3-NPs at 3 bar/4hrs was selected as an ideal composition/curing-conditions; the compressive-strength reached 54.5 MPa exceeding the standard limit of Portland cement (42.5 MPa). This clearly shows the synergistic role of using WO3-NPs and hydrothermal curing to enhance the compressive-strength, which was confirmed using different analysis techniques. XRD, TGA/DTG and SEM/mapping proved that the catalytic performance of WO3-NPs/hydrothermal-curing participates in augmenting binding hydrates, creating a cubic-stable-phase of tricalcium-aluminate-hydrate (C3AH6) and different types of zeolitic-like structure (spherical Zeolite-NaP, rods analcime and stacked-plates cancrinite). To maximize the benefits of employing WO3-NPs in the developed composites, their anti-microbial activity was studied. The measured inhibition zone around specimens containing WO3-NPs proved that these composites have a superior self-cleaning efficiency against Candida albicans, Mucor circinelloides, Salmonella typhi and Staphylococcus aureus due to the WO3- NPs’ photocatalytic activity.
... The XRD pattern of WO 3 , WTC-1, WTC-3 and WTC-5 heterojunctions is displayed in Fig. 4a. Here the diffractions patterns of WO 3 nanosheets could be well indexed to the standard monoclinic phase of WO 3 [32] . Prominent diffractions peaks are ascribed to (0 0 2), (0 2 0), (2 0 0), (1 2 0), (1 1 2), (0 2 2), (2 0 2), (2 2 2) and (4 0 0), respectively. ...
... where λ is 1.54056 Å and 0.94 is a constant for the Cu Kα radiation, β is line broadening in the radian (FWHM [32,35]. The Raman spectrum of WTC heterojunctions composites clearly displays the predominance of monoclinic phase of WO 3 rather than the Ti 3 C 2 , similar to the observations made in XRD analysis. ...
This article describes a straightforward chemical procedure that involves hydrothermal and ultrasonic treatments to create a new 2D/2D ultrathin WO3/Ti3C2 heterojunctions. The features of the fabricated heterojunctions were characterized and examined by field emission electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), optical absorption spectroscopy (UV–Vis). By photodegrading an organic dye under the influence of visible light, the photocatalytic degradation capabilities of the heterojunctions were also investigated. The performance of WO3/Ti3C2 was superior to that of bare WO3, with a removal rate of 94% and a kinetic rate constant (k) that was approximately 3 times that of WO3. The creation of 2D/2D heterojunction was observed to encourage the spatial charge separation and increase the surface reactive sites, to result with the increased photocatalytic activity in WO3/Ti3C2 heterojunction. The photocurrent values discovered through photoelectrochemical studies further indicated Ti3C2′s active function in enhancing water-splitting performance. The impedance analysis examined by an electrochemical method revealed that heterojunctions might be helpful in accelerating the migration of charges quickly to get the outcomes seen.
... (iii) Improved Bioavailability: The stability of tungstenbased nanoparticles enhances their bioavailability, which refers to their ability to reach and interact with bacterial cells effectively [50,51]. These nanoparticles can maintain their structure and properties during transportation, storage, and application, ensuring that they retain their antibacterial activity until they reach the target site [51]. ...
In recent years, the rise of antibiotic-resistant bacteria has posed a significant challenge to public health worldwide. As traditional antibiotics become less effective, there is an urgent need to explore alternative strategies to combat bacterial infections. Tungsten-based nanoparticles have emerged as promising candidates for their potential as antibacterial agents. This article highlights the pressing need for effective antibacterial agents and discusses the potential of tungsten-based nanoparticles in addressing this urgent concern. We delve into the unique properties and mechanisms of action exhibited by these nanoparticles, including their ability to generate reactive oxygen species and induce photothermal effects, leading to bacterial cell death. Additionally, we discuss the challenges associated with utilizing tungsten-based nanoparticles, such as their potential toxicity and compatibility with human cells. Furthermore, we explore the future prospects and ongoing research efforts aimed at optimizing the synthesis, characterization, and application of tungsten-based nanoparticles as antibacterial agents. By addressing these challenges and harnessing the potential of tungsten-based nanoparticles, we can pave the way for the development of effective antibacterial strategies and contribute to combating the global threat of antibiotic resistance.
... eV, depending on the synthesized structure form [5,6]. WO 3 has multiple allotropic forms such as tetragonal, orthorhombic, triclinic, and monoclinic. Furthermore, WO 3 has two monoclinic phases, namely, ε-WO 3 and γWO 3 which is the most common and stable phase [7,8]. WO 3 has oxygen vacancies in sub-stoichiometric forms, such as (WO 2.9 ), (WO 2.83 ), and (WO 2.72 ), which affect the photocatalytic performance [9,10]. ...
WO3 films were chemically prepared by spray pyrolysis method using different starting tungsten precursors. The WO3 layers were deposited at 450 °C and subsequently were heat treated at 500 °C in the air for 30 min. The effect of starting tungsten precursors on the physical properties and catalytic activity of WO3 layers was investigated. The results of XRD show that the WO3 films were crystalline and can be indexed to the monoclinic structure. The sample prepared using ammonium metatungstate precursor showed enhanced crystallinity and surface morphology. The diffuse reflection spectrophotometry shows that the obtained WO3 films have a direct bandgap about of 2.7–2.9 eV. Chemical catalytic activity was evaluated through the reduction of 4-nitrophenol to 4-aminophenol. All prepared WO3 thin films showed catalytic activity; however, the sample prepared using ammonium metatungstate precursor exhibited much higher catalytic activity when compared to the other precursors, which is consistent with other results. Furthermore, this sample demonstrated good stability and recyclability.
... Tungsten oxides with substoichiometric phases have been demonstrated as potential alternatives to commercial platinum catalyst in acidic HER process [12][13][14] , benefiting from these abundant oxygen vacancies that can afford substoichiometric WO 3-x catalysts with favorable hydrogen adsorption energies and improved conductivity 15 . However, their alkaline HER activities have been rarely explored, because tungsten oxides featured with acidic-oxide property will be gradually dissolved in alkaline electrolyte [16][17][18] . Although first-row (3d) transition metals (Fe, Co, Ni) as additives have been proven to significantly improve the alkaline HER performance of tungsten oxides 19 , the introduction of foreign atoms probably obscures the catalytic mechanism, since the identification of doping state of low-atomic-number 3d metals among tungsten arrays is rather challenging 20 . ...
The lack of available protons severely lowers the activity of alkaline hydrogen evolution reaction process than that in acids, which can be efficiently accelerated by tuning the coverage and chemical environment of protons on catalyst surface. However, the cycling of active sites by proton transfer is largely dependent on the utilization of noble metal catalysts because of the appealing electronic interaction between noble metal atoms and protons. Herein, an all-non-noble W/WO2 metallic heterostructure serving as an efficient solid-acid catalyst exhibits remarkable hydrogen evolution reaction performance with an ultra-low overpotential of −35 mV at −10 mA/cm² and a small Tafel slope (−34 mV/dec), as well as long-term durability of hydrogen production (>50 h) at current densities of −10 and −50 mA/cm² in alkaline electrolyte. Multiple in situ and ex situ spectroscopy characterizations combining with first-principle density functional theory calculations discover that a dynamic proton-concentrated surface can be constructed on W/WO2 solid-acid catalyst under ultra-low overpotentials, which enables W/WO2 catalyzing alkaline hydrogen production to follow a kinetically fast Volmer-Tafel pathway with two neighboring protons recombining into a hydrogen molecule. Our strategy of solid-acid catalyst and utilization of multiple spectroscopy characterizations may provide an interesting route for designing advanced all-non-noble catalytic system towards boosting hydrogen evolution reaction performance in alkaline electrolyte.
