Effect of bismuth tungstate with different hierarchical architectures on photocatalytic degradation of norfloxacin under visible light

The photocatalytic degradation of norfloxacin by bismuth tungstate(Bi2WO6)with different hierarchical architectures wasinvestigated under visible light irradiation.Bi2WO6was prepared by hydrothermal method with the reaction solution pH rangingfrom4to11.The relatively ultrathin Bi2WO6nanoflakes prepared at pH4showed excellent adsorption and photodegradationefficiency towards norfloxacin.The characterization results showed that Bi2WO6prepared at pH4had a larger specific area andfaster photo-generated carrier separation rate.The decay rate reached the maximum in weak alkaline reaction solution,which couldbe attributed to the presence of moderate OH-anions.The present study demonstrated that the smaller size of Bi2WO6could be anefficient photocatalyst on the degradation of norfloxacin in the aquatic environment.

Iodine-doping-assisted tunable introduction of oxygen vacancies on bismuth tungstate photocatalysts for highly efficient molecular oxygen activation and pentachlorophenol mineralization

In this work,the tunable introduction of oxygen vacancies in bismuth tungstate was realized via asimple solvothermal method with the assistance of iodine doping.With the predictions afforded bytheoretical calculations,the as-prepared bismuth tungstate was characterized using various tech-niques,such as X-ray diffraction,Raman spectroscopy,scanning electron microscopy,transmissionelectron microscopy,X-ray photoelectron spectroscopy,electron spin resonance spectroscopy,anduV-Vis diffuse reflectance spectroscopy.The different concentrations of the oxygen vacancies onbismuth tungstate were found to be intensely correlated with iodine doping,which weakened thelattice oxygen bonds.Owing to the sufficient oxygen vacancies introduced in bismuth tungstate as aresult of iodine doping,the molecular oxygen activation was remarkably enhanced,thus endowingbismuth tungstate with high activity for the photocatalytic degradation of sodium pentachloro-phenate.More encouraging is the total organic carbon removal rate of sodium pentachlorophenateover iodine-doped bismuth tungstate that exceeded 90%in only 2 h and was 10.6 times higher thanthat of the pristine bismuth tungstate under visible light irradiation.Moreover,the mechanism,through which the degradation of sodium pentachlorophenate over iodine-doped bismuth tung-state is enhanced,was speculated based on the results of radical detection and capture experiments.This work provides a new perspective for the enhanced photocatalytic degradation of organochlo-rine pesticides from the oxygen vacancy-induced molecular oxygen activation over iodine-dopedbismuth tungstate.

Oxygen-deficient bismuth tungstate and bismuth oxide composite photoanode with improved photostability

A homogeneous layer of Bi_2O_3-Bi_(14)WO_(24) composite(BWO/Bi_2O_3) thin film was fabricated using a combination of electrodeposition and thermal treatment. The evenly distributed Bi14 WO24 component within the Bi_2O_3 layer was found to be important in stabilising the photoelectrochemical performances of Bi_2O_3 photoanode by promoting the photoelectron transport. The unmodified Bi_2O_3 suffered from severe photocorrosion as proven by X-ray diffraction(XRD) and inductively coupled plasma(ICP) analyses while the composite thin film was active without noticeable activity decay for at least 3 h of illumination. This strategy might be applicable to other photocatalysts with stability issues.

Flower-like Bi_2WO_6/ZnO composite with excellent photocatalytic capability under visible light irradiation

The photocatalytic ability of ZnO is improved through the addition of flower‐like Bi2WO6 to prepare a Bi2WO6/ZnO composite with visible light activity.The composite is characterized by X‐ray diffraction,transmission electron microscopy,scanning electron microscopy with UV–vis diffuse reflectance spectroscopy,X‐ray photoelectron spectroscopy and N2 adsorption‐desorption isotherms.After modification,the band gap energy of Bi2WO6/ZnO is reduced from 3.2 eV for ZnO to 2.6 eV.Under visible light irradiation,the Bi2WO6/ZnO composite shows an excellent photocatalytic activity for degrading methylene blue(MB)and tetracycline.The photo‐degradation efficiencies of(0.3:1)Bi2WO6/ZnO for MB and tetracycline are approximately 246 and 4500 times higher than those of bare ZnO,respectively,and correspondingly,the photo‐degradation rates for the two pollutants are approximately 120 and 200 times higher than those with bare ZnO,respectively.Moreover,the photocatalyst of(0.3:1)Bi2WO6/ZnO exhibits a higher transient photocurrent density of approximately 4.5μA compared with those of bare Bi2WO6 and ZnO nanoparticles.The successful recombination of Bi2WO6 and ZnO enhances the photocatalytic activity and reduces the band gap energy of ZnO,which can be attributed to the effective separation of electron–hole pairs.Active species trapping experiments display that[O2]-is the major species involved during photocatalysis rather than·OH and h+.This study provides insight into designing a meaningful visible‐light‐driven photocatalyst for environmental remediation.

Exploring a broadened operating pH range for norfloxacin removal via simulated solar-light-mediated Bi_2WO_6 process

Semiconductor photocatalysis can be operated over a narrow pH range for wastewater treatment. In this study, a simulated solar-light-mediated bismuth tungstate (SSL/Bi2WO6) process is found to be effective for norfloxacin degradation over a narrow pH range. To broaden the operating pH range of the SSL/Bi2WO6 process, an NH4+ buffer system and an Fe3+ salt were introduced under extremely basic and acidic pH conditions, respectively. The NH4+ buffer system continuously supplied hydroxyl ions to generate ·OH radicals and prevented acidification of the solution, resulting in improved norfloxacin removal and mineralization removal under alkaline conditions. In contrast, the Fe3+ salt offered an additional homogeneous photo-sensitization pathway. The former treatment assisted in norfloxacin decay and the latter increased the collision frequency between the photo-generated hole and hydroxyl ions. Moreover, the effect of parameters such as pH and Fe3+ dosage was optimized.

Morphology Controlled Synthesis and Characterization of Bi_2WO_6 Photocatalysts

Nest-like and multilayered-disk-like Bi2WO6 photocatalysts were synthesized through a hydrothermal strategy using thiourea and acetic acid as complexing agents. The nest-like Bi2WO6 showed excellent visible-light-driven photocatalytic performance, and it could decompose rhodamine B（RhB） within 100 minutes. This excellent performance resulted from its special microstructure and the relatively large surface area.

In situ single iron atom doping on Bi_(2)WO_(6)monolayers triggers efficient photo-fenton reaction

Developing an efficient photocatalytic system for hydrogen peroxide(H_(2)O_(2))activation in Fenton-like processes holds significant promise for advancing water purification technologies.However,challenges such as high carrier recombination rates,limited active sites,and suboptimal H_(2)O_(2)activation efficiency impede optimal performance.Here we show that single-iron-atom dispersed Bi_(2)WO_(6)monolayers(SIAD-BWOM),designed through a facile hydrothermal approach,can offer abundant active sites for H_(2)O_(2)activation.The SIAD-BWOM catalyst demonstrates superior photo-Fenton degradation capabilities,particularly for the persistent pesticide dinotefuran(DNF),showcasing its potential in addressing recalcitrant organic pollutants.We reveal that the incorporation of iron atoms in place of tungsten within the electron-rich[WO_(4)]^(2-)layers significantly facilitates electron transfer processes and boosts the Fe(II)/Fe(III)cycle efficiency.Complementary experimental investigations and theoretical analyses further elucidate how the atomically dispersed iron induces lattice strain in the Bi_(2)WO_(6)monolayer,thereby modulating the d-band center of iron to improve H_(2)O_(2)adsorption and activation.Our research provides a practical framework for developing advanced photo-Fenton catalysts,which can be used to treat emerging and refractory organic pollutants more effectively.

A review on Bi_(2)WO_(6)-based photocatalysts synthesis, modification, and applications in environmental remediation, life medical, and clean energy

Photocatalysis has emerged a promising strategy to remedy the current energy and environmental crisis due to its ability to directiy convert clean solar energy into chemical energy.Bismuth tungstate(Bi_(2)WO_(6))has been shown to be an excellent visible light response,a well-defined perovskite crystal structure,and an abundance of oxygen atoms(providing efficient channels for photogenerated carrier transfer)due to their suitable band gap,effective electron migration and separation,making them ideal photocatalysts.It has been extensively applied as photocatalyst in aspects including pollutant removal,carbon dioxide reduction,solar hydrogen production,ammonia synthesis by nitrogen photocatalytic reduction,and cancer therapy.In this review,the fabrication and application of Bi_(2)WO_(6) in photocatalysis were comprehensively discussed.The photocatalytic properties of BizwO-based materials were significantly enhanced by carbon modification,the construction of heterojunctions,and the atom doping to improve the photogenerated carrier migration rate,the number of surface active sites,and the photoexcitation ability of the composites.In addition,the potential development directions and the existing challenges to improve the photocatalytic performance of Bi_(2)WO_(6)-based materials were discussed.

A self-cleaning window for high-efficiency photodegradation of indoor formaldehyde

Formaldehyde(HCHO)as an indoor air pollutant released by new furniture and decorative materials is of great concern.Developing a self-cleaning device to remove HCHO is an ideal way to improve indoor air quality.In this study,a self-cleaning window with a multilayered structure constructed from fluorinedoped tin oxide/bismuth tungstate/resorcinol-formaldehyde resin(FTO/Bi_(2)WO_(6)/RF)has been fabricated,which is capable of degrading HCHO in natural indoor condition.The as-fabricated device could utilize the natural room light and promote the generation and transfer of the photocatalytic carriers in Bi_(2)WO_(6),which subsequently delivers a good catalytic oxygen reduction efficiency in RF to produce hydrogen peroxide(H_(2)O_(2)).The as-synthesized H_(2)O_(2)could further split into hydroxyl radicals(•OH),then oxide the HCHO molecules in the air.The present study demonstrates a novel and efficient strategy to fabricate a transparent multifunctional window for self-cleaning indoor gaseous pollutants,the concept is of great importance to be expanded in a broad range of indoor furniture for in-house air pollution control.

Preparation and performance of novel magnetic phase-change-microcapsule-supported Bi_(2)WO_(6)catalyst

The design and synthesis of novel photocatalyst with self-temperature control function is an important topic in the field of advanced environmental functional materials.In this work,submicron-sized magnetic phase change microcapsules composed of paraffin core and Fe_(3)O_(4)-loaded silica shell are prepared,on which the Bi_(2)WO_(6)crystals is grown in situ through hydrothermal reaction to obtain novel magnetic phase-change-microcapsule-supported Bi_(2)WO_(6)catalyst(MP@FS/BWO).The MP@FS/BWO has a paraffin encapsulation ratio of 57.1%,and the phase change enthalpy of 105.1 J/g in a temperature range of 50–60℃,which endows the MP@FS/BWO with a certain self-temperature regulation ability.MP@FS/BWO shows excellent catalytic performance in the decomposition of rhodamine B under the simulated sunlight irradiation.After the light source is turned off,it still has good catalytic ability by maintaining high temperature due to its temperature control function based on the phase transition process.The MP@FS/BWO can be easily recycled by magnetic separation and shows good structural stability and reusability.This work provides a new idea for the development of long-effect and energy-saving outdoor photocatalysts.

Harnessing Vis-NIR broad spectrum for photocatalytic CO2 reduction over carbon quantum dots-decorated ultrathin Bi2WO6 nanosheets

The photocatalytic reduction of CO2 to energy-rich hydrocarbon fuels is a promising and sustainable method of addressing global warming and the imminent energy crisis concomitantly. However, a vast majority of the existing photocatalysts are only capable of harnessing ultraviolet （UV） or/and visible light （Vis）, whereas the near-infrared （NIR） region still remains unexplored. In this study, carbon quantum dots （CQDs）-decorated ultrathin BizWO6 nanosheets （UBW） were demonstrated to be an efficient photocatalyst for CO2 photoreduction over the Vis-NIR broad spectrum. It is noteworthy that the synthesis procedure of the CQDs/UBW hybrid nanocomposites was highly facile, involving a one-pot hexadecyltrimethylammonium bromide （CTAB）-assisted hydrothermal process. Under visible light irradiation, the optimized 1CQDsAJBW （1 wt.% CQD content） exhibited a remarkable 9.5-fold and 3.1-fold enhancement of CH4 production over pristine Bi2WO6 nanoplatelets （PBW） and bare UBW, respectively. More importantly, the photocatalytic responsiveness of CQDs/UBW was successfully extended to the NIR region, which was achieved without involving any rare earth or noble metals. The realization of NIR-driven CO2 reduction could be attributed to the synergistic effects of （i） the ultrathin nanostructures and highly exposed {001} active facets of UBW, （ii） the excellent spectral coupling of UBW and CQDs, where UBW could be excited by the up-converted photoluminescence of CQDs, and （iii） the electron-withdrawing nature of the CQDs to trap the photogenerated electrons and retard the recombination of charge carriers.