Ultrathin Bi2WO6 Research Articles

Ultrathin 2D/2D MoS2/Bi2WO6 S-scheme heterojunction for boosting photocatalytic degradation of ciprofloxacin

A series of 2D/2D MoS2/Bi2WO6 S-scheme heterojunctions consisting of ultrathin MoS2 nanosheets (MS, 1.6 nm) and ultrathin Bi2WO6 nanosheets (BWO, 1.5 nm) were developed for photocatalytic degradation of ciprofloxacin. The samples with 5 % mass ratio of MS (5 %MS/BWO) exhibits the almost complete degradation of ciprofloxacin (≈100 %) under visible light. It is evidenced that the formation of S-scheme heterojunction with close interfacial interaction facilitates the photoinduced carrier separation and the generation of surface acid sites. The activation of ciprofloxacin molecules is realized through the coordinately interaction of C-N and C=O with the surface W sites. Moreover, the OVs in BWO side is a convenient pathway for activated of O2, embodying in the generation of •O2− and •OH under visible light over photocatalyst. Such an association of charge transfer mechanism with coordination activation shows the enhanced photocatalytic performance toward ciprofloxacin. This work provides a motivation which designs an S-scheme heterojunction photocatalyst with the ability to activate the specific group in molecules to comprehend the degradation of antibiotics.

Efficient piezo-assisted near-infrared-light-driven Cr(VI) reduction over Bi2S3 nanowires transformed from ultrathin Bi2WO6 nanosheets

Efficient piezo-assisted near-infrared-light-driven Cr(VI) reduction over Bi2S3 nanowires transformed from ultrathin Bi2WO6 nanosheets

Halogen-doped ultrathin Bi2WO6 for promoted separation of photogenerated carriers and efficient photocatalysis

Although photocatalysis is a viable and sustainable technique to remove refractory pollutants from wastewater, it is plagued by the low separation efficiency of photo-generated carriers. Herein, in situ surfactants (CTAC, CTAB, and DTAI) assisted synthesis of halogen-doped ultra-thin Bi2WO6 (BWO) nanosheets with oxygen vacancies, which efficiently degraded RhB and TC under visible light. Surfactant as a halogen source can also prevent the formation of BWO layered structures, thus making the sample thinner and thus reducing the transmission distance of photogenerated electrons. The degradation rates of rhodamine B (RhB) and tetracycline (TC) by BWO-Cl-90 and BWO-Br-90 upon visible light illumination are 5.8 times / 5.5 times and 2.5 times / 2.8 times by those of pure BWO, respectively. The free radical trapping experiments and ESR reveal that singlet oxygen (1O2) and photogenerated holes (h+) are the main active free radicals in the degradation of organic pollutants by BWO-Cl-90, while the superoxide radical (·O2-) and photogenerated holes (h+) play the main roles for BWO-Br-90. The photocatalytic mechanism is proposed. In addition, the EIS, photocurrent and photoluminescence (PL) experiments show that halogen doping improves the separation ability of photogenerated carriers. This study reveals a practical method to modify Bi2WO6-based materials for effective wastewater treatment and purification.

An all-in-one self-supporting Na-Bi2WO6 photocatalyst for portable air purifier: Laminar splitting boosts high efficacy in mineralizing toluene and disinfection

An air purifier that provides clean air will be popular if it is portable and capable of removing volatile organic chemicals and reducing exposure to bacteria. Herein, ultra-thin and dense Bi2WO6 nanoflakes grown on W meshes specialize in offering abundant oxygen vacancies due to Na+ driving laminar splitting. Under visible lights, the photogenerated carriers streaming along the ultrathin Bi2WO6 surface produce bountiful reactive oxygen species for mineralizing VOCs and sweeping bacteria. Enriched with •O2- and •OH, a 15 cm*5 cm Na-Bi2WO6 mesh can completely degrade 30 ppm toluene in 0.45 dm3 reactor in 1 hour without producing any toxic intermediates like benzene, and its efficacy only decayed by 4% after a continuous 14-hour run. A cup-shaped air purifier was assembled with the Na-Bi2WO6 mesh, enabling the rapid elimination of 1 ppm toluene, 2 ppm formaldehyde, and bacteria within a 120 dm3 test space.

Tailoring bismuth defects in Bi2WO6 nanosheets for photocatalytic C–H activation

Tailoring the bismuth defects in ultrathin Bi2WO6 nanosheets can efficiently activate the C–H bond in toluene to produce benzaldehyde under light irradiation.

Atomic-level surface modification of ultrathin Bi2WO6 nanosheets for boosting photocatalytic CO2 reduction

Creating useful chemicals based on artificial CO2 photoreduction is considered to be an attractive approach to address the environmental and energy crises. Currently, its selectivity with high conversion efficiency is still a grand challenge. Here, we report the refined substitution of Bi3+ with Ag+ in ultrathin Bi2WO6 nanosheets through a liquid-phase cation exchange process, favoring a high selectivity towards the photocatalytic production of CO from CO2. The incorporation of Ag+ could not only significantly promote the adsorption of both CO2 and H2O molecules, but also facilitate the transfer of photogenerated carriers. The as-fabricated photocatalyst achieves a high CO generation rate of 116.96 μmol g−1 with a superb selectivity of 95.7 % after 6 h reaction without any sacrificial agent, approximate 4.2 times higher than that of pure Bi2WO6. The mechanism for photocatalytic CO2 reduction is proposed, based on in-situ Fourier Transform Infrared spectrometry analyses and Density Functional Theory calculations.

A novel vibration-driven piezostructure assembled from BiFeO3 nanodisks and ultrathin Bi2WO6 nanosheets for organic pollutant degradation

Piezocatalysis has garnered considerable attention as a prospective water treatment technology due to its great potential to convert mechanical energy into electrical energy. This study introduces a novel vibration-driven piezocatalyst by incorporating BiFeO3 (BFO) nanodisks on ultrathin Bi2WO6 (UBWO) nanosheets (denoted as BFO/UBWO) through a facile hydrothermal process to overcome the feeble charge mobility of BiFeO3 for organic pollutant decontamination. Multiple characterization techniques revealed that the BFO/UBWO nanocomposite effectively formed heterojunctions between its individual components, which boosted the piezocatalytic degradation of methyl orange (MO) by facilitating piezo-induced charge carrier migration. Based on optimized reaction conditions, it was discovered that 80 % loading of BFO in BFO/UBWO nanocomposite exhibited superb piezocatalytic performance in which 94 % of MO was decontaminated within 75 min, which was greater compared to bare BFO and UBWO. The calculated synergy factor indisputably confirmed the superiority of BFO/UBWO over its individual components. The scavenger tests demonstrated that holes and •OH radicals served as the dominant reactive species in the piezocatalysis process. As part of the effort to examine the industrial application of the nanocomposite, piezocatalytic activity of BFO/UBWO nanocomposite only decreased marginally after six consecutive tests, and metal leaching was negligible. A possible mechanism of the enhanced piezocatalytic activity of BFO/UBWO nanocomposite was proposed, and the synergy effect of the fabricated heterojunction was investigated in detail. This work not only showcases an innovative strategy for the design of exceedingly effective Bi-based piezocatalysts but also casts light on cost-effective and trouble-free synthesized piezocatalysts for water remediation.

Tandem CQDs loaded triple metal oxide interface-reinforced built-in electric field for a wide-spectral-responsive photocatalyst

Focusing at efficient Cefixime (CEFX) removal, a delicate ultrathin-Bi2WO6 (UBWO) stacked quasi-CoFe2O4 binanosheets (BT) were meticulously designed and integrated with spherical MnWO4 (MWO) and carbon quantum dots (CQDs), forming a n-p-n CQDs@MWO/CFO:UBWO nanohybrid. XRD, XPS, TEM and other systematic analysis demonstrated the vertically aligned layer by layer assembly of UBWO:CFO BT, and a shift in the highly exposed (211) facet of UBWO after nanohybrid formation as well as large surface area (323.33 m2/g) was achieved. UV–vis DRS, PL and EIS proved high separation efficiency, prolonged life time and photogeneration of more charge carriers with absorption of full light spectrum. As expected, the optimized 5 %CQDs@0.25MWO/0.1CFO:UBWO nanohybrid displayed excellent visible light absorption and outstanding CEFX photodegradation whose kinetic constant were 21.11, 12.5, 8.82 folds higher than UBWO, CFO and MWO counterparts. This enhanced photodegradation performance ascribed to the dual strategy as follows: (i) Cascaded charge transfer with the Built-in electric field (BIEF) after n-p-n heterojunction, (ii) the upconverted PL and the electron reservoir properties of CQDs. Degradation efficiency maintained over six consecutive cycles affirming the superior recyclability of the photocatalyst. A possible degradation pathway was proposed based on GC-MS/MS analysis and the end products toxicity were systematically predicted using ECOSAR program. The toxicity of the end product was investigated against bacterial species. The proposed work provides a novel way for the fabrication of efficient photocatalyst with excellent practical applicability.

Superior photopiezocatalytic performance by enhancing spontaneous polarization through post-synthesis structure distortion in ultrathin Bi2WO6 nanosheet polar photocatalyst

The internal polarizations of polar photocatalysts could be enhanced through unit cell structure modulations to improve their photocatalytic performances. In this work, a simple, robust and low-cost NaOH etching process is developed to treat ultrathin Bi2WO6 nanosheets after their creation, resulting in a higher degree of polyhedron distortion (∼141 %) and an enhanced piezoelectricity (∼260 % the maximum effective piezoelectric coefficient d33). Compared with pristine ultrathin Bi2WO6 nanosheets, these etched samples demonstrate an improved charge carrier separation and transfer behavior due to their enhanced internal polarization with the assistance of richer oxygen vacancies, which largely enhance their piezocatalysis (∼4.6 times), photocatalysis (∼14.3 times) and especially coupled photopiezocatalysis (∼33.9 times) performances as demonstrated in their sulfamethoxazole (SMX) degradation performances. ·O2–, 1O2 and h+ are proven to be main reactive oxygen species (ROSs) during their photopiezocatalytic process and they could also work well in the real water matrix.

Promoting charge separation of 0D/2D CsPbBr3/Bi2WO6 Z-scheme heterojunctions for boosting photocatalytic N2 reduction

High efficient photocatalytic nitrogen fixation is an alternative strategy to solve the problems of energy consumption and environmental pollution of industrial ammonia production effectively, hence the selection and modification of catalysts are very important to improve the nitrogen fixation efficiency. In this article, a straightforward Z-scheme 0D/2D CsPbBr3/Bi2WO6 heterojunction was successfully constructed via a simple electrostatic self-assembly approach. By combining CsPbBr3 quantum dots (CPB QDs) with ultrathin Bi2WO6 (BWO) nanosheets, a large-area heterointerface of CPB QDs and BWO nanosheets was connected tightly thus shortened the charge transport distance effectively. This facilitates the efficient charge transfer between CPB and BWO through the Z-scheme interface, thereby achieving the purpose of promoting charge separation, which is well validated in differential charge. On the basis of various characterizations, the results indicated that the CPB/BWO heterojunction possessed an excellent photocatalytic nitrogen fixation performance: the production of NH3 at 3CPB/BWO heterojunctions (126.3 μmol‧g−1‧h−1) was about 17.1 times higher than that of pure CPB QDs. The new strategy may offer a new opportunity to the exploration and the research of halide perovskite-type photo catalysts with obviously enhanced nitrogen fixation activities.

Surface Lewis acid sites and oxygen vacancies of Bi2WO6 synergistically promoted photocatalytic degradation of levofloxacin

Ultrathin Bi2WO6 nanosheets with a high concentration of surface oxygen vacancies (BWO-OVs) are successfully constructed for the degradation of levofloxacin (LVX) under visible light irradiation and show a high degradation efficiency of LVX (≈100 %). It is revealed that the oxygen vacancies (OVs) over BWO-OVs nanosheets can not only accelerate the separation of photo-induced electrons and holes, but also activate the O2 molecules to form O2– species. The FTIR spectra and density functional theory deeply demonstrate that piperazine ring and CO groups (carboxylic acid) in LVX can be chemisorbed and activated by surface Lewis acid sites. The EPR results reveal that photo-generated holes, O2– and OH species are reactive oxygen species for the photocatalytic degradation of LVX. The possible intermediate is well investigated by LC-MS results combined with the FTIR spectra results. This work provides a new perspective for understanding photocatalytic degradation from the interaction between the active sites of a photocatalyst and antibiotics molecules.

Ultrafast photocatalytic degradation of nitenpyram by 2D ultrathin Bi2WO6: mechanism, pathways and environmental factors

Ultrafast photocatalytic degradation of nitenpyram by 2D ultrathin Bi2WO6: mechanism, pathways and environmental factors

Synergetic piezo-photocatalytic effect in ultrathin Bi2WO6 nanosheets for decomposing organic dye

Synergetic piezo-photocatalytic effect in ultrathin Bi2WO6 nanosheets for decomposing organic dye

Construction of GQDs‐Decorated Ultrathin Bi2WO6 Nanosheets Hydrogel: a Recyclable‐Flexible Platform with Excellent Piezo‐Photocatalytic Activity for High‐Performance Water Decontamination and its Theoretical Interpretation

AbstractIt is demonstrated that, by using the electronic reconstruction of ultrathin Bi2WO6 (BWO) nanosheets with graphene quantum dots (GQDs) upon a unique process of laser irradiation in liquid (LAL), a kind of GQDs modified BWO nanosheets under metastable state were synthesized, which performed excellent visible‐light piezo‐photocatalytic organics degradation. Furthermore, using commercial cpolyacrylamids (PAM) as the additional materials, a kind of electronic reconstruction GQDs‐BWO nanosheets hydrogel was achieved by dispersed the functionalized powders into a super absorbent polymers (SAPs) system upon in situ polymerization method, which showed that it is a bracing idea to use SAPs for water decontamination reactors to enable full use of vibration energy synergistic with light of nature to driven pollution degradation. First‐principles calculation was also simultanously performed in this study. This study may provide a new enlightenment on fabricating novel 2D nanomaterials hydrogel for efficient effluent purification and potentially other environmental or energy applications.

Ultra-Thin Carbon-Doped Bi2WO6 Nanosheets for Enhanced Photocatalytic CO2 Reduction

The photocatalytic reduction of CO2 is a promising strategy to generate chemical fuels. However, this reaction usually suffers from low photoactivity because of insufficient light absorption and rapid charge recombination. Defect engineering has become an effective approach to improve the photocatalytic activity. Herein, ultra-thin (~ 4.1 nm) carbon-doped Bi2WO6 nanosheets were prepared via hydrothermal treatment followed by calcination. The ultra-thin nanosheet structure of the catalyst not only provides more active sites but also shortens the diffusion distance of charge carriers, thereby suppressing charge recombination. Moreover, carbon doping could successfully extend the light absorption range of the catalyst and remarkably promote charge separation, thus inhibiting recombination. As a result, the as-prepared Bi2WO6 photocatalyst with ultra-thin nanosheet structure and carbon doping exhibits enhanced photocatalytic CO2 reduction performance, which is twice that of pristine ultra-thin Bi2WO6 nanosheet. This study highlights the importance of defect engineering in photocatalytic energy conversion and provides new insights for fabricating efficient photocatalysts.

In-situ construction of WC/Bi2WO6 nanocomposites for efficient photodegradation of bisphenol A with peroxymonosulfate activation

Exploring highly efficient catalyst is the key for integration of photocatalysis and peroxymonosulfate (PMS) activation. Herein, WC/Bi2WO6 nanocomposites were judiciously constructed by anchoring the non-noble metal plasmonic WC nanocrystals onto the surface of ultrathin Bi2WO6 nanosheets to activate PMS for efficient photodegradation of bisphenol A (BPA). The prepared WC/Bi2WO6 nanocomposites possess abundant heterojunction interface, resulting in excellent photoabsorption capability, interfacial charge transfer dynamics, and charge carrier concentration. As expected, WC/Bi2WO6 nanocomposites exhibit superior catalytic activity and stability in PMS activation toward BPA degradation with removal efficiency of 97.4%, which is higher than that of Bi2WO6. The content of WC nanocrystals are critical to tune the catalytic activity of the nanocomposites. The intermediates and degradation pathways were determined through LC-MS/MS analysis. Finally, the reaction mechanism was systematically elucidated based on the active species detection, charge transfer dynamics, and band structures. The desirable photocatalytic performances can be ascribed to the constructional heterojunction between the WC nanocrystals and Bi2WO6 nanosheets, which can efficiently enhance the photoabsorption capability, heighten the interfacial charge transfer ability, and ameliorate the charge carrier concentration. This study provides some insights to construct highly efficient photocatalyst modification with non-noble metal based plasmonic materials for environmental remediation.

In Situ Construction of Lead‐Free Perovskite Direct Z‐Scheme Heterojunction Cs3Bi2I9/Bi2WO6 for Efficient Photocatalysis of CO2 Reduction

The well‐known toxicity of lead‐halide‐perovskite (LHP) nanocrystals limits their commercial applications in photocatalysis. Herein, an in situ controlled growth strategy is reported for lead‐free perovskite nanocrystals (Cs3Bi2I9) on the surface of ultrathin Bi2WO6 nanosheets through co‐sharing Bi atoms, to generate a direct Z‐scheme heterojunction of Cs3Bi2I9/Bi2WO6. Co‐sharing of the Bi atom can enable intimate contact and strong electron coupling between Cs3Bi2I9 and Bi2WO6, which can effectively promote the interfacial charge transfer between Cs3Bi2I9 and Bi2WO6 complying with a Z‐scheme pathway. The resulting efficient charge transfer and well‐preserved redox ability of Cs3Bi2I9/Bi2WO6 heterojunction endow it with a significant improvement of photocatalytic activity for the conversion of CO2‐to‐CO integrated with water oxidation, exhibiting a fourfold increase compared with pure Cs3Bi2I9 nanocrystals. This study paves a new avenue for the construction of efficient Z‐scheme heterojunction based on lead‐free halide perovskite, which should stimulate further passion on the development of high performance of lead‐free halide perovskite materials for photocatalytic application.

Topotactic Transformation of Bismuth Oxybromide into Bismuth Tungstate: Bandgap Modulation of Single-Crystalline {001}-Faceted Nanosheets for Enhanced Photocatalytic CO2 Reduction.

The photocatalytic conversion of CO2 to energy-rich CH4 solar fuel is an ideal strategy for future energy generation as it can resolve global warming and the imminent energy crisis concurrently. However, the efficiency of this technology is unavoidably hampered by the ineffective generation and utilization of photoinduced charge carriers. In this contribution, we report a facile in situ topotactic transformation approach where {001}-faceted BiOBr nanosheets (BOB-NS) were employed as the starting material for the formation of single-crystalline ultrathin Bi2WO6 nanosheets (BWO-NS). The as-obtained BWO-NS not only preserved the advantageous properties of the 2D nanostructure and predominantly exposed {001} facets but also possessed enlarged specific surface areas as a result of sample thickness reduction. As opposed to the commonly observed bandgap broadening when the particle sizes decrease to an ultrathin nanoscale owing to the quantum size effect, the developed BWO-NS exhibited a fascinating bandgap narrowing compared to those of pristine Bi2WO6 nanoplates (BWO-P) synthesized from a conventional one-step hydrothermal approach. Moreover, the electronic band positions of BWO-NS were modulated as a result of ion exchange for the reconstruction of the energy bands, where BWO-NS demonstrated significant upshifting of CB and VB levels; these are beneficial for photocatalytic reduction applications. This propitious design of BWO-NS through integrating the merits of BOB-NS caused BWO-NS to exhibit substantial 2.6 and 9.3-fold enhancements of CH4 production over BOB-NS and BWO-P, respectively.

Facile Fabrication of Z-Scheme Bi2WO6/WO3 Composites for Efficient Photodegradation of Bisphenol A with Peroxymonosulfate Activation.

The rational fabrication of direct Z-scheme heterostructures photocatalysts is a pivotal strategy to boost the interfacial charge migration and separation. Herein, direct Z-scheme Bi2WO6/WO3 composites were rationally fabricated for the degradation of bisphenol A combined with the activation of peroxymonosulfate (PMS). The tight interface contact between Bi2WO6 and WO3 was successfully formed by the in situ epitaxial growth of ultrathin Bi2WO6 nanosheets at the surface of WO3 nanorods. The Bi2WO6/WO3 composite presented highly efficient catalytic performance toward degradation of BPA with PMS activation as compared to the WO3 and Bi2WO6. PMS can dramatically boost the photocatalytic activity of the composites. Moreover, the results of active radical scavenging experiments revealed that h+, •O2−, and •SO4− are critical active species in the photodegradation reaction. Finally, the photocatalytic mechanism for the degradation of BPA is also discussed in detail. The great improvement of photocatalytic performance should be ascribed to the effective formation of the direct Z-scheme heterojunctions between Bi2WO6 and WO3, resulting in improved light absorption, an efficient transfer and separation of photoinduced charge carriers, and a considerable amount of the electrons and holes with strong reduction and oxidation abilities. The study might provide new inspirations to design and construct heterostructured nanomaterials with outstanding photoactivity for environmental remediation.

Effective charge kinetics steering in surface plasmons coupled two-dimensional chemical Au/Bi2WO6-MoS2 heterojunction for superior photocatalytic detoxification performance

Developing and designing a rational heterojunction with efficient charge kinetics properties have been a research hotspot for improving photocatalytic performance. Herein, a surface plasmons coupled two-dimensional chemical Au/Bi2WO6-MoS2 heterojunction was synthesized. In thus a system, Au nanoparticles are tightly attached to the sides of Bi2WO6 nanosheets, conducting a HEI effect with additional visible light response to inject “hot electrons” into Bi2WO6, resulting in additional charge generation. Meanwhile, few-layer MoS2 nanosheets were chemically assembled onto ultrathin Bi2WO6 nanosheets via interfacial SO bonds to form a intimate 2D-2D nanojunction, the separated and injected electrons on the surface of Bi2WO6 were further directional transfer to MoS2 nanosheets through SO bonds for detoxification of heavy metal ions Cr(VI), and the corresponding holes left on Bi2WO6 nanosheets were applied for simultaneous degradation of tetracycline antibiotic. The photocatalytic detoxification activity of Au/Bi2WO6-MoS2 was nearly 4.84, 3.47 and 1.90 times higher than that of pristine Bi2WO6, Au/Bi2WO6 and Bi2WO6-MoS2 composites, which could be ascribed to the effective charge kinetics steering and well manipulation of charge flow by virtue of the rational structural and compositional features. This work provides a new perspective for the construction of high-activity detoxification photocatalysts through steering charge kinetics.