Highly efficient BiVO4/WO3 nanocomposite towards superior photocatalytic performance

Unleashing the power of solar light: WO3 nanorods decorated onto BiVO4 dendrites for tetracycline detoxification and water splitting

The coupling of different oxide materials in a nanohybrid enables the customization of their optical and charge transport properties, leading to improved interfacial charge segregation and migration. In this study, BiVO4/WO3 (BVW), a sunlight-driven photocatalyst with distinct mole ratios was synthesized via a facile hydrothermal approach. The resultant catalyst exhibits a nanorods shape morphology decorated onto dendrite-like matrix and is studied for photocatalytic elimination of tetracycline (TC) and photoelectrocatalytic (PEC) H2 production. The effect of illumination time, solution pH, photocatalyst concentration, and mole ratios of BiVO4 to WO3 on the photocatalytic abatement of TC were tested sequentially as effective operating factors. Under optimal condition, 3:1 BiVO4:WO3 (31BVW) nanohybrid demonstrated a maximum degradation efficacy of 96.2% (rate constant ~0.0241 min-1), which is much better than its individual components and commercial TiO2-P25 (50.9%). The resultant by-products of TC decomposition were analyzed using GC-MS to explain the degradation mechanism. Moreover, as a photoanode, 31BVW showed a high photocurrent density of 0.64 mA/cm2 at 1.23 V vs RHE and a steady photocurrent for ~6 h under chronoamperometry study at1.23 V vs RHE. However, bare BiVO4 and WO3 exhibited the photocurrent density of 0.001 mA/cm2, and 0.015 mA/cm2, respectively at 1.23 V vs RHE. The Mott-Schottky analysis of 31BVW confirms their n-type behavior, with a calculated flat band potential of -0.067 V. The hydrogen production rate was theoretically calculated as 4.56 mmolcm-2 s-1 from chronoamperometric measurements. The photocatalyst's efficacy in TC degradation was further established via its reusability upto 7 cycles. Post degradation characterization of catalyst confirms its stability in lieu of practical usage. Comparative studies with existing literature revealed the superiority of reported photocatalysts in both applications. Overall, the binary BVW photocatalyst shows great potential for removing detrimental contaminants as well as H2 production via PEC water splitting due to efficient charge separation, reduced recombination, high surface area, and widen absorption window of the nanohybrid.

A Meta-Analysis of Influencing Factors on the Activity of BiVO4-Based Photocatalysts

With the continuous advancement of global industrialization, a large amount of organic and inorganic pollutants have been discharged into the environment, which is essential for human survival. Consequently, the issue of water environment pollution has become increasingly severe. Photocatalytic technology is widely used to degrade water pollutants due to its strong oxidizing performance and non-polluting characteristics, and BiVO4-based photocatalysts are one of the ideal raw materials for photocatalytic reactions. However, a comprehensive global analysis of the factors influencing the photocatalytic performance of BiVO4-based photocatalysts is currently lacking. Here, we performed a meta-analysis to investigate the differences in specific surface area, kinetic constants, and the pollutant degradation performance of BiVO4-based photocatalysts under different preparation and degradation conditions. It was found that under the loading condition, all the performances of the photocatalysts can be attributed to the single BiVO4 photocatalyst. Moreover, loading could lead to an increase in the specific surface area of the material, thereby providing more adsorption sites for photocatalysis and ultimately enhancing the photocatalytic performance. Overall, the construct heterojunction and loaded nanomaterials exhibit a superior performance for BiVO4-based photocatalysts with 136.4% and 90.1% improvement, respectively. Additionally, within a certain range, the photocatalytic performance increases with the reaction time and temperature.

A facile synthesis of visible light driven Ni3V2O8 nano-cube/BiVO4 nanorod composite photocatalyst with enhanced photocatalytic activity towards degradation of acid orange 7

Photocatalysis is one of the promising method to degrade harmful organic pollutants under visible light exposure. In this work, a novel Ni₃V₂O₈/BiVO₄ nanocomposite has been prepared by one-pot hydrothermal method, and investigated through X-ray diffraction, FT-IR, UV-visible diffuse reflectance spectroscopy, scanning and transmission electron microscopy and photoluminescence techniques. Subsequently, the photocatalytic performance of Ni₃V₂O₈/BiVO₄ nanocomposite has been examined by degrading AO7 under visible light illumination. The photocatalytic efficiency of the optimized 1:2 ratio of Ni₃V₂O₈/BiVO₄ nanocomposite photocatalyst is found to be 87% with a rate constant value of 0.03387 min^-1 which are higher than those of other prepared photocatalysts. This nanocomposite exhibits excellent stability even after 3 three cycles, and shows 1.135- and 1.17-times higher photocurrent intensity than pure BiVO₄ and Ni₃V₂O₈ respectively. The mechanism for the degradation of AO7 over Ni₃V₂O₈/BiVO₄ nanocomposite photocatalyst has been proposed.

Microstructure and Mechanical Properties of W-Al2O3 Alloy Plates Prepared by a Wet Chemical Method and Rolling Process

The uneven distribution and large size of the second phase weakens the effect of dispersion strengthening in ODS-W alloys. In this article, the W-Al₂O₃ composite powders were fabricated using a wet chemical method, resulting in a finer powder and uniformly dispersed Al₂O₃ particles in the tungsten-based alloy. The particle size of the pure tungsten powder is 1.05 μm and the particle size of W-0.2 wt.%Al₂O₃ is 727 nm. Subsequently, the W-Al₂O₃ alloy plates were successfully obtained by induction sintering and rolling processes. Al₂O₃ effectively refined grain size from powder-making to sintering. The micro-hardness of the tungsten alloy plates reached 512 HV_0.2, which is 43.7% higher than that of pure tungsten plates. The nano-hardness reached 14.2 GPa, which is 24.1% higher than that of the pure tungsten plate; the compressive strength reached 2224 MPa, which is 37.2% higher than that of the pure tungsten.

A Z-scheme CdS/BiVO4 photocatalysis towards Eriochrome black T: An experimental design and mechanism study

The synergistic photocatalytic activity was obtained when CdS and BiVO₄ nanoparticles (NPs) were coupled. The samples were characterized by XRD, FTIR, SEM-EDX, and UV-DRS techniques, and their pHpzc was also estimated. The crystallite size of the coupled sample was estimated at 37.3 and 12.5 nm by the Scherrer and Williamson-Hall equations, respectively. The band gaps and the potential positions of VB and CB levels of the semiconductors used were determined. The highest boosted photocatalytic activity was obtained when the CdS: BiVO₄ mole ratio was 1:1. RSM studied the simultaneous interactions between the selected variables, and the model F-value of 110.61> F_{0.05, 14, 13} = 2.4 accompanied by the LOF F-value of 5.20 < F_{0.05, 10, 3} = 8.79 confirm the model significance. The correlation coefficients of R² = 0.9861, the adjusted R² = 0.9710, and the predicted R² = 0.9417, also establish a satisfactory model for processing the experimental data. In the scavenging agent study, photodegradation mechanisms were suggested; among them, the direct Z-scheme mechanism is more favorable for illustrating the EBT-photodegradation by the binary CdS-BiVO₄ photocatalyst. The proposed system, especially the direct Z-scheme mechanism, is suitable as a potential hydrogen production system.

Bio-alcohol induced self-assembly of heterojunctioned TiO2/WO3 composites into a hierarchical yolk-shell structure for photocatalysis

In the fabrication of efficient multicomponent semiconductors for photocatalysis, well-defined hierarchical structures and high-quality heterojunctions are still highly desired. A general preparation method was developed for a series of hierarchical TiO2-based heterojunctions with tailored interior space from solid, core-shell and yolk-shell to fully hollow structures.

BiVO4/WO3 nano-composite: characterization and designing the experiments in photodegradation of sulfasalazine

A BiVO₄-WO₃ nano-composite (NC) was hydrothermally prepared and characterized by different techniques including X-ray diffraction (XRD), scanning electron microscope equipped with an energy-dispersive X-ray (EDX) analyzer, X-ray mapping, UV-Vis reflectance spectroscopy (DRS), and photoluminescence spectroscopy (PL). The average crystallite size of 8.5 nm was estimated for the composite by the Williamson-Hall equation. The band gap energies of 2.46, 3.02, and 2.95 eV were obtained for the direct electronic transitions of BiVO₄, WO₃, and the composite, respectively. The point of zero charges (pHpzc) of the composite was also estimated at 5. The composite was then used in the photodegradation of sulfasalazine (SSZ). When the moles of WO₃ was four times greater than BiVO₄, the best photocatalytic activity and the lowest PL intensity were obtained. The simultaneous effects of the experimental variables on the boosted photocatalytic activity of the composite (to the single semiconductors) were studied by the response surface methodology (RSM). A significant quadratic model was confirmed for processing the data based on the F value of a model F value of 63.55 > F_{0.05, 14, 13} = 2.55. This was also confirmed by LOF F value of 2.56 < F_{0.05, 10, 3} = 8.79. Besides, the multiple correlation coefficients R² (R² = 0.9856), adjusted R² (adj-R² = 0.9701), and predicted R² (pred-R² = 0.9098) confirm the goodness of the model. The optimal run included C_SSZ 9 mg/L, pH 4, 40 min irradiation time, and 0.8 g/L of the composite under the visible light irradiation.

Electronic and optical competence of TiO2/BiVO4 nanocomposites in the photocatalytic processes

Nanocomposites with different ratios of titanium dioxide and bismuth vanadate [TiO₂]/[BiVO₄] give rise to compatible electronic band structure alignment at their interfaces to ensure enhanced photoactivated charge transfer under visible light. The sol–gel method and suitable post-synthesis thermal treatments were used to synthesize different compositions with stabilized anatase phase of TiO₂ and monoclinic scheelite polymorph BiVO₄. Structural, electronic and optical characterizations were performed and the results were analysed as a function of the stoichiometry, in which both crystalline structures show a clear junction formation among their characteristic stacking planes. Photocatalytic and (photo) electrochemical responses of the nanocomposites were investigated and tested for the degradation of azo dyes (Acid Blue-113, AB-113) (~ 99%) under visible light radiation. The nanocomposite with a mass ratio of (1:10) shows the highest photocatalytic efficiency compared to the other compositions. HRTEM images showed marked regions in which both crystalline structures form a clear junction and their characteristic planes. However, the increase of BiVO₄ content in the network overcomes the photocatalytic activity due to the decrease in the reduction potential of the photo-generated electrons with high recombination rates.

The improvement of photocatalysis O2 production over BiVO4 with amorphous FeOOH shell modification

A novel amorphous FeOOH modified BiVO₄ photocatalyst (A-FeOOH/BiVO₄) was successfully produced and characterized by various techniques. The results showed that amorphous FeOOH with about 2 nm thickness evenly covered on BiVO₄ surface, which caused resultant A-FeOOH/BiVO₄ exhibiting higher visible light photocatalytic performance for producing O₂ from water than BiVO₄. When the covered amount of amorphous FeOOH was 8%, the resultant photocatalyst possessed the best photocatalytic performance. To find the reasons for the improvement of photocatalytic property, electrochemical experiments, DRS, PL and BET, were also measured, the experimental results indicated that interface effect between amorphous FeOOH and BiVO₄ could conduce to migration of photogenerated charge, and exhibit stronger light responded capacity. These positive factors promoted A-FeOOH/BiVO₄ presenting improved the photocatalytic performance. In a word, the combination of amorphous FeOOH with BiVO₄ is an effective strategy to conquer important challenges in photocatalysis field.

Bismuth vanadate-based semiconductor photocatalysts: a short critical review on the efficiency and the mechanism of photodegradation of organic pollutants

The number of publications on photocatalytic bismuth vanadate-based materials is constantly increasing. Indeed, bismuth vanadate is gaining stronger interest in the photochemical community since it is a solar-driven photocatalyst. However, the efficiency of BiVO₄-based photocatalyst under sunlight is questionable: in most of the studies investigating the photodegradation of organic pollutants, only few works identify the by-products and evaluate the real efficiency of BiVO₄-based materials. This short review aims to (i) present briefly the principles of photocatalysis and define the photocatalytic efficiency and (ii) discuss the formation of reactive species involved in the photocatalytic degradation process of pollutants and thus the corresponding photodegradation mechanism could be determined. All these points are developed in a comprehensive discussion by focusing especially on pure, doped, and composite BiVO₄. Therefore, this review exhibits a critical overview on different BiVO₄-based photocatalytic systems with their real efficiency. This is a necessary knowledge for potential implementation of BiVO₄ materials in environmental applications at larger scale than laboratory conditions.

A simple sonochemical approach to fabricate a urea biosensor based on zinc phthalocyanine/graphene oxide/urease bioelectrode

A novel zinc phthalocyanine/graphene oxide (ZnPh/GO) nanocomposite modified glassy carbon electrode (GCE) was prepared by using sonochemical approach and simple drop casting method. Urease (Urs) was used as the specific enzyme for urea detection and was physically immobilized onto the surface of ZnPh/GO nanocomposite. The fabricated ZnPh/GO/Urs matrix was successfully characterized by UV-vis-spectroscopy, FT-IR spectroscopy, scanning electron microscopy (SEM), raman spectrum, thermogravimetric analysis, cyclic voltammetric (CV) and amperometric techniques. The electrocatalytic performance of the ZnPh/GO/Urs electrode was investigated by urea biosensor. Our results demonstrate that the modified electrode has excellent electrocatalytic activity towards the sensing of urea in 0.1 M phosphate buffer solution (PBS, pH 7.2). The biosensor tolerated a wide linear concentration range for urea from 0.4 to 22 μM (R² = 0.991), with a detection limit of 0.034 µM (S/N = 3). The ZnPh/GO/Urs bioectrode has several excellent properties, including a fast response time, high reproducibility and stability.

Fabrication of g-C3N4/NiO heterostructured nanocomposite modified glassy carbon electrode for quercetin biosensor

Herein, we report a one-pot synthesis of structurally uniform and electrochemically active graphitic carbon nitride/nickel oxide (g-C₃N₄/NiO) nanocomposite and an investigation on the electrocatalytic oxidation of quercetin (QR). The synthesized g-C₃N₄/NiO nanocomposite has uniform surface distribution, which was characterized with scanning electron microscopy (SEM). Moreover, the composition of synthesized g-C₃N₄/NiO nanocomposite was characterized by UV-vis-spectroscopy, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR spectra), BET, SEM and HRTEM. The g-C₃N₄/NiO was electrochemically treated in 0.1 MPBS solution through cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The peak current response increases linearly with QR concentration from 0.010 μM to 250 µM with a fast response time of less than 2 s and a detection limit of 0.002 μM. To further evaluate the feasibility of using this sensor for real sample analysis, QR content in various real samples including green tea, green apple, honey suckle were determined and satisfactory results were achieved.

One-step synthesis of composite material MWCNT@BiVO4 and its photocatalytic activity

In this research, a composite material (MWCNT@BiVO₄) was prepared using a one step hydrothermal method.