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To overcome the drawback caused by rapid recombination of photogenerated electron-hole pairs, a novel visible-light-driven Bi2WO6/r-GO/Bi25FeO40 Z-scheme photocatalyst was fabricated through the hydrothermal method. The as-prepared sample was analyzed by X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscopy (TEM), scanning e...
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Surface-modified ZnO photocatalysts with enhanced UVA-light-driven and visible-light-driven activities were synthesized by the thermal shock method with Cu(NO3)2 at different thermal shock temperatures (300 – 600°C). The influences of thermal shock temperatures on the crystal structure, morphology, surface functional groups and surface composition...
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... Between different crystal phases of bismuth ferrites, the sillenite Bi 25 FeO 40 phase has a small band-gap value (around 1.8-2.0 eV) and greater photocatalytic performance [25]. Nevertheless, the low photoactivity of Bi 25 FeO 40 bismuth ferrite as a single photocatalyst hinders its requests. ...
... The phase structure, morphology, optical, and photoelectrochemical features of as-constructed materials were explored through some characterization techniques. The photocatalytic efficiencies of ZIF-67(5 to 50 wt%)/Bi 25 3 .9H 2 O was supplemented into the above solution. Furthermore, 0.5 g of kappa-carrageenan was added, which is used as a capping material. ...
... In the current work, the photodegradation efficiency of ZIF-67, Bi 25 Furthermore, the physically-mixed ZIF-67/Bi 25 FeO 40 possessed high photocatalytic performance, reaching 87 %. Also, the photodegradation activity of the constructed samples toward OFL degradation can be determined from the degradation rates. ...
In the photocatalytic degradation processes of organic pollutants, the designing and fabricating photocatalytic heterojunctions is the best solution to increase the charge separation efficiency and boost the photoactivity of semiconductors. In this research, we fabricated sillenite Bi25FeO40 crystals and Co-zeolitic imidazolate framework (ZIF-67) separately, and then combined them in different percentages (from 5 to 50 wt% ZIF-67) to achieve efficient nanocomposite heterojunctions for visible-light-assisted ofloxacin (OFL) degradation and successfully reduced charge recombination. Unsurprisingly, ZIF-67/Bi25FeO40 hybrid endorsed superior photocatalytic activity for OFL degradation. Under visible-light irradiation, the 25 wt% ZIF-67/Bi25FeO40 sample degraded 95.5 % of OFL after 60 min, which compared to undecorated Bi25FeO40 was approximately 7.2-times improvement. These achievements are ascribed to the boosted visible-light harvesting and the great separation of photoinduced e−-h+ pairs as a result of the creation of Z-system heterojunction between ZIF-67 and Bi25FeO40 phases. According to the trapping experiments, radical dotO2−, radical dotOH, and h+ species act as key reactive species in OFL photodegradation. The photocatalytic degradation of about 90.1 % was still reached at the end of the fifth photodegradation round, demonstrating high durability of synthesized ZIF-67/Bi25FeO40 heterojunction. This work will be useful for the development of Z-scheme ZIF-67/Bi25FeO40 heterojunction with high photocatalytic performance.
... The p-type semiconductor behavior is a characteristic of BFO synthesized by the hydrothermal method in an oxidizing medium, generating Bi vacancies, which, by ionization, release their holes [16]. In addition, the n-type conductivity specific to Bi 25 FeO 40 is highlighted by the Mott-Schottky analysis of S3 ( Figure 6) [30]. The characteristics of BFO ceramics are heavily influenced by factors such as grain size and density. ...
Bismuth ferrite (BiFeO3, BFO) is still widely investigated both because of the great diversity of its possible applications and from the perspective of intrinsic defect engineering in the perovskite structure. Defect control in BiFeO3 semiconductors could provide a key technology for overcoming undesirable limitations, namely, a strong leakage current, which is attributed to the presence of oxygen vacancies (VO) and Bi vacancies (VBi). Our study proposes a hydrothermal method for the reduction of the concentration of VBi during the ceramic synthesis of BiFeO3.Using hydrogen peroxide (H2O2) as part of the medium, p-type BiFeO3 ceramics characterized by their low conductivity were obtained. Hydrogen peroxide acted as the electron donor in the perovskite structure, controlling VBi in the BiFeO3 semiconductor, which caused the dielectric constant and loss to decrease along with the electrical resistivity. The reduction of Bi vacancies highlighted by a FT-IR and Mott—Schottky analysis has an expected contribution to the dielectric characteristic. A decrease in the dielectric constant (with approximately 40%) and loss (3 times) and an increase of the electrical resistivity (by 3 times) was achieved by the hydrogen peroxide-assisted hydrothermal synthesized BFO ceramics, as compared with the hydrothermal synthesized BFOs.
... The total dye was photodegraded in 15 minutes using 25 mg of catalyst dispersed into 50 mL of RhB solution ( 10 mg L −1 ). In this context, several heterojunctions materias have been used for MO [66,71,72,[74][75][76][77][78][79], RhB [53,59,60,61,67,72,73,78,[80][81][82][83][84][85][86][87][88][89][90][91][92][93][94][95], MB [53,72,75,77,94,[96][97][98][99][100][101][102][103][104][105] and other pulliting dyes [54,75,100,103,[106][107][108][109][110][111][112][113][114][115][116][117][118] removal, as shown in Table 2. ...
Among the technologies proposed for wastewater treatment, the Advanced Oxidation Processes are viable and technological strategies for dyes degradation. Different photocatalytic systems classified in metal oxides alone or combined through hybrid composites or immobilized onto supports have been designed in various nanostructured shapes for their application in the photodegradation of polluting dyes. This review aims to describe the dyes as an environmental threat, photocatalysis as an effective process to remove dyes from water and provide an overview of the recent studies using photocatalytic systems grouped according to their development. Furthermore, this review describes the main parameters of a photocatalytic system with an important role in dye photodegradation. Finally, we discuss the limitations of photocatalysis for real industrial applications and the challenges for this environmental nanotechnology.
... The EIS spectra of as-prepared products are shown in Fig. 12C. A widely accepted view was that the smaller arc radius revealed a better charge separation efficiency and a quicker interfacial charge migration [71,72]. Apparently, the arc radius in the EIS spectrum of N-BiOBr/NiFe 2 O 4 -15 nanocomposite was the smallest when compared to other products, demonstrating positive effect in reducing the charge transfer resistance and favoring the charge carrier separation. ...
In the present work, new Z-scheme N-BiOBr/NiFe2O4 nanocomposites were successfully constructed by a facile hydrothermal method. Various analytical characterization techniques were employed to examine the physicochemical and optical absorption properties of prepared photocatalysts. The prepared N-BiOBr/NiFe2O4 nanocomposites considerably enhanced the simultaneous visible light removal of phenol and Cr(VI) when compared with single-phase component photocatalysts. Especially, the N-BiOBr/NiFe2O4-15 nanocomposite demonstrated the top-flight photoactivity. The formed Z-scheme system in the nanocomposite significantly decreased the charge carrier recombination and improved the photoactivity. Photoluminescence and photoelectrochemical measurements were conducted to confirm the evidence of efficient charge carrier separation by the nanocomposites. Moreover, the N-BiOBr/NiFe2O4-15 nanocomposite can be magnetically separated and possessed good recycle performance up to five successive runs. The active species capturing experiments demonstrated that the hydroxyl radicals can degrade the phenol efficiently and that photogenerated electrons can reduce the Cr(VI). Finally, the mechanism of excellent photoactivity of N-BiOBr/NiFe2O4 nanocomposite was discussed.
In latest events, water pollution has posed an immense threat, and its sustainable treatment is a topic of concern. Among myriad of water treatment, research community has lensed towards sustainable heterogeneous photocatalysis especially, inorganic semiconductors. Bismuth tungstate a pristine Aurivillius compound with unique crystal structure, exceptional photochemical stability, and strong redox abilities but minimum visible light absorption and quick carrier recombination are its caveats, these caveats are circumvented by synthesizing BiOX (X=F, Cl, Br and I) composites with surface modifiers, doping with hetero atoms (metals and non‐metals), construction of the heterojunction and amalgamation of carbon materials. The heart of this review is strategic engineering of flower‐like morphology photocatalyst synthesis and optical properties, it also discusses the charge transfer kinetics, photocatalytic performance, and durability. The flower‐like morphology highlighted in this review is due to its ability to harvest light, providing larger specific surface area which introduces more active sites and efficient excitons generation. The comprehensive tabulated data in this review will help the actively engaged research community in Bismuth heterogenous photocatalysis. It also sheds light on the future view of environmental remediation via photocatalytic developments.
From a new perspective, polymorphism is now often considered as a functional property that extends the applications of many materials. BiFeO3 is still an interesting material from both fundamental and applied points of view. A unique characteristic of BiFeO3 film, the polymorphism was stabilised only using the epitaxial strain caused by the substrate of the film. Here we report the hydrothermal synthesis of biphasic BiFeO3 ceramics using low NaOH concentration and temperature. The ability of BiFeO3 ceramics to morph into tetragonal and rhombohedral allotropic phases was demonstrated, confirming the theoretical prediction that the polymorphism can be stabilised even in powder form. Based on our experimental study NaOH(aq) is proposed as responsible for the strain on the structure of the rhombohedral phase. In addition, the in-depth characterisation of this biphasic ceramic opens up new opportunities for the technological applications of BiFeO3 material.
The removal of antibiotics from water using solar (visible) light catalytic technology has the advantages of high efficiency, safety, and environmental friendliness. The bismuth tungstate semiconductor catalyst Bi2WO6 exhibits superior performance; however, further research is required to elucidate its synergistic catalytic effects and to better understand its adsorption performance. Herein, a series of modified bismuth tungstate catalysts were prepared by introducing various dispersants. Advanced characterization methods were employed to reveal the structure and composition of the Bi2WO6 catalyst, and the preparation conditions of modified Bi2WO6 were optimized by investigating the adsorption and photocatalytic properties of the catalysts. The synergistic effects of catalyst adsorption and visible light catalysis significantly enhanced the removal of tetracycline through a mechanism whereby the pollutants were enriched on the surface of the catalyst owing to its superior adsorption capacity; this provided a sufficient reaction microenvironment for photocatalytic degradation. The catalyst was loaded onto a sponge surface and subjected to continuous-stream catalysis in a reactor for the degradation of tetracycline-containing wastewater (influent pollutant concentration = 0.8 mg/L). This sponge-loaded Bi2WO6 catalyst was used with a dosage of 0.6 g/L under a light source intensity of 140000 Lux and illumination for 2-h intervals. A hydraulic retention time (HRT) of more than 6 h was observed, and the system achieved a degradation efficiency for trace tetracycline up to 97%, while exhibiting good operational effects after continuous operation for 12 d.
To study the degradation of tetracycline by Bi2S3-based binary composite and ternary composite photocatalysts, Cu2O/Bi2S3 and NH2-UiO-66/BiOBr/Bi2S3 was successfully fabricated by the solvothermal method, which can effectively and stably degrade tetracycline (TC). The crystal structure, chemical composition, and microscopic morphology of the as-prepared sample were analysed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The photocatalytic performance of the composite photocatalyst was estimated by degradation of TC under visible-light irradiation. The results showed that the removal ratio of TC by Cu2O/Bi2S3 and NH2-UiO-66/BiOBr/Bi2S3 are 95.2% and 93.2%, respectively. The photoelectric properties of the material were evaluated by PL and EIS analysis, and compared to Bi2S3, the overall visible light absorption capacity, as well as the separation and transfer rates of photogenerated carriers of the composites photocatalyst have been significantly improved. Both Cu2O/Bi2S3 and NH2-UiO-66/BiOBr/Bi2S3 can achieve a good photodegradation performance for TC, but the results of UV–vis DRS spectrum, Mott–Schottky curve, and free radical trapping experiments show that their photodegradation mechanism for TC is different. For Cu2O/Bi2S3, •O2⁻ and h⁺ are the main active species in the photocatalytic reaction process, among which •O2⁻ plays the most important role, but •OH has almost no effect, and for NH2-UiO-66/BiOBr/Bi2S3, the main active species are •OH and h⁺. The possible photocatalytic mechanisms for Cu2O/Bi2S3 and NH2-UiO-66/BiOBr/Bi2S3 are Z-scheme and double Z-schemes are proposed, respectively.
To study the degradation of bisphenol A (BPA) of the different Bi2WO6-based composite photocatalyst under visible-light irradiation, a novel Z-scheme Cu2S/reduced graphene oxide/Bi2WO6 (Cu2S/RGO/Bi2WO6) was successfully synthesised by solvothermal-hydrothermal method, andBi25FeO40/RGO/Bi2WO6 was introduced for comparative study. The Cu2S/RGO/Bi2WO6 was characterised by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS) test and X-ray photoelectron spectrometer (XPS).TheBi2WO6,Cu2S/RGO/Bi2WO6andBi25FeO40/RGO/Bi2WO6 were used to degrade bisphenol (BPA) under visible light, respectively, and in addition peroxymonosulfate (PMS) was used as an additive for the Cu2S/RGO/Bi2WO6 to degrade BPA. For Cu2S/RGO/Bi2WO6@PMS, the removal ratio of BPA is 91.0% in 40 minutes, which is much higher than pure Bi2WO6 (22.0%),Cu2S/RGO/Bi2WO6 without PMS (56.1%) and Bi25FeO40/RGO/Bi2WO6 (48.3%). A Z-scheme photocatalytic mechanism was proposed for Cu2S/RGO/Bi2WO6@PMSbased on the results of UV–vis DRS, PL analysis and Mott–Schottky curve. There are four factors that contribute to CuS2/RGO/Bi2WO6with PMS to achieve excellent photocatalytic performance: 1. The larger specific area; 2. the higher absorption capacity of visible light; 3. RGO can act as a very important role to significantly accelerate electron transfer, and 4. PMS can be activated to generate •SO4⁻ for BPA degradation.
