BiVO4-rGO with a novel structure on steel fabric used as high-performance photocatalysts

Photocatalytic Degradation of Crystal Violet on Cu, Zn Doped BiVO4 Particles

Fabrication of codoped photocatalysts is a developing area of research. Herein, we explore the visible light photocatalytic properties of Cu, Zn codoped BiVO4 particles. Doping lower valent cations (Cu and Zn) makes the BiVO4 surface more acidic and enables us to target the basic crystal violet (CV) dye. The adopted hydrothermal protocol of synthesis results in the formation of Cu-Zn codoped monoclinic BiVO4 particles. Undoped monoclinic BiVO4, prepared by the same protocol, showed significant formation of oxygen vacancies. XPS analyses confirm the coexistence of Cu2+/Cu+ and Zn2+ dopants. Increased dopant percentage reduced oxygen vacancies. XRD indicates that Cu2+/Cu+ or Zn2+ dopants generally substitute Bi3+ in BiVO4. All photocatalysis activities for CV degradation are reported under near-neutral pH conditions. A typical codoped BiVO4 photocatalyst with 1% Zn and 2% Cu demonstrated the best CV degradation photocatalytic activity. The activity of this Zn, Cu codoped photocatalyst is better than that of pure, Zn-doped, and Cu-doped BiVO4 samples. Active species trapping experiments indicated the possible photocatalysis mechanism. The photocatalysts exhibited appropriate recyclability and photostability.

Photo-electrocatalytic based removal of acetaminophen: Application of visible light driven heterojunction based BiVO4/BiOI photoanode

The presence of organic micro-pollutants (OMPs) in wastewater treatment effluents is becoming a major threat to the water safety for aquatic and human health. Photo-electrocatalytic based advanced oxidation process (AOP) is one of the emerging and effective techniques to degrade OMPs through oxidative mechanism. This study investigated the application of heterojunction based BiVO₄/BiOI photoanode for acetaminophen (40 μg L^-1) removal in demineralized water. Photoanodes were fabricated by electrodeposition of BiVO₄ and BiOI photocatalytic layers. Optical (UV-vis diffusive reflectance spectroscopy), structural (XRD, SEM, EDX) and opto-electronic (IPCE) characterization confirmed the successful formation of heterojunction for enhanced charge separation efficiency. The heterojunction photoanode showed incident photon to current conversion efficiency of 16% (λ_max = 390 nm) at an external voltage of 1 V under AM 1.5 standard illumination. The application of the BiVO₄/BiOI photoanode in the removal of acetaminophen at 1 V (external bias) vs Ag/AgCl under simulated sunlight showed 87% removal efficiency within the first 120 min compared to 66% removal efficiency of the BiVO₄ photoanode. Similarly, combining BiVO₄ and BiOI exhibited 57% increase in first order removal rate coefficient compared to BiVO₄. The photoanodes also showed moderate stability and reusability by showing 26% decrease in overall degradation efficiency after three cycles of each 5 h experiment. The results obtained in this study can be considered as a stepping stone towards the effective removal of acetaminophen as an OMP present in wastewater.

One-step preparation of RGO/Fe3O4-FeVO4 nanocomposites as highly effective photocatalysts under natural sunlight illumination

The study used a one-step hydrothermal method to prepare Fe₃O₄-FeVO₄ and xRGO/Fe₃O₄-FeVO₄ nanocomposites. XRD, TEM, EDS, XPS, DRS, and PL techniques were used to examine the structurally and morphologically properties of the prepared samples. The XRD results appeared that the Fe₃O₄-FeVO₄ has a triclinic crystal structure. Under hydrothermal treatment, (GO) was effectively reduced to (RGO) as illustrated by XRD and XPS results. UV-Vis analysis revealed that the addition of RGO enhanced the absorption in the visible region and narrowed the band gap energy. The photoactivities of the prepared samples were evaluated by degrading methylene blue (MB), phenol and brilliant green under sunlight illumination. As indicated by all the nanocomposites, photocatalytic activity was higher than the pure Fe₃O₄-FeVO₄ photocatalyst, and the highest photodegradation efficiency of MB and phenol was shown by the 10%RGO/Fe₃O₄-FeVO₄. In addition, the study examined the mineralization (TOC), photodegradation process, and photocatalytic reaction kinetics of MB and phenol.

Bismuth vanadate/MXene (BiVO4/Ti3C2) heterojunction composite: enhanced interfacial control charge transfer for highly efficient visible light photocatalytic activity

We have synthesized BiVO4/Ti3C2 nanocomposite via a low-cost hydrothermal method and investigate its photocatalytic degradation activity against monoazo (methyl orange) and diazo dye (Congo red) in an aqueous solution under visible light. The physiochemical characterization exhibited that the addition of MXene in pristine BiVO4 nanocomposite led to an increase in specific surface area and reduction in optical band gap energy. MXene also helps in enhancing visible light response via a higher electron-hole pair generation rate and long lifetime. The synthesized BiVO4/Ti3C2 heterojunction composite exhibited 99.5 % degradation efficiency within 60 min for Congo red and 99.1 % for methyl orange solution in 130 min owed to a large specific surface area (1.79 m2/g), reduced band gap (1.99 eV), and low recombination rate of charge carriers. The chemical mechanism for BiVO4/Ti3C2 nanocomposite proposes that Ti3C2 role-plays as electron capture because of the higher potential of MXenes, tuning band gap energy which paves the way to excellent photocatalytic action. This work opens a new basis for developing Ti3C2 based promising and inexpensive co-catalyst for efficient solar utilization in photocatalytic-related applications in the future.

Pt–BiVO4/TiO2 composites as Z-scheme photocatalysts for hydrogen production from ethanol: the effect of BiVO4 and Pt on the photocatalytic efficiency

The photodeposition of platinum particles on the BiVO₄/TiO₂ composite surface promotes the H₂ production by reducing H⁺ species.

Hydrothermal synthesis of cotton-based BiVO4/Ag composite for photocatalytic degradation of C.I. Reactive Black 5

Photocatalytic materials with high efficiency and convenient recyclability have attracted great interest for the treatment of printing and dyeing wastewater. In this paper, a narrow band gap BiVO₄ photocatalyst was loaded onto Ag modified cotton fabric by a hydrothermal method. The prepared composite materials were characterized by scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and ultraviolet visible light absorption spectroscopy (UV-vis). The composite materials as prepared show superb photocatalytic activity and reusable performance for the degradation of C.I. Reactive Black 5 (RB5). The degradation rate can reach 99% within 90 min under 1 kW xenon lamp irradiation, and over 90% of the photocatalytic performance is preserved even after five recycles. Furthermore, the photocatalytic mechanism was proposed by spectral analysis and free radical trapping experiments.

Magnetically Recoverable TiO2/SiO2/γ-Fe2O3/rGO Composite with Significantly Enhanced UV-Visible Light Photocatalytic Activity

In this paper, we report the preparation of a new composite (TiO₂/SiO₂/γ-Fe₂O₃/rGO) with a high photocatalytic efficiency. The properties of the composite were examined by different analyses, including X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), photoluminescence (PL), UV-Visible light diffuse reflectance spectroscopy, Fourier transform infrared spectroscopy (FTIR), Raman, vibrating-sample magnetometer (VSM), and nitrogen gas physisorption (BET) studies. The photocatalytic efficiency of the proposed composite was evaluated by the degradation of methylene blue under UV and visible light, and the results were compared with titanium dioxide (TiO₂), where degradation increased from 30% to 84% and 4% to 66% under UV and visible light, respectively. The significant increase in photocatalytic activity may be explained by the higher adsorption of dye on the surface of the composite and the higher separation and transfer of charge carriers, which in turn promote active sites and photocatalytic efficiency.

Architecting a Double Charge-Transfer Dynamics In2S3/BiVO4 n-n Isotype Heterojunction for Superior Photocatalytic Oxytetracycline Hydrochloride Degradation and Water Oxidation Reaction: Unveiling the Association of Physicochemical, Electrochemical, and Photocatalytic Properties

To surmount incompatibility provoked efficiency suppression of an anisotype heterojunction and to pursue an improved intrinsic photocatalytic activity by manipulating oriented transfer of photoinduced charge carriers, an In₂S₃/BiVO₄ (1:1) n-n isotype heterojunction was fabricated successfully through a simple two-step calcination method, followed by a wet-chemical deposition method. The formation of an n-n isotype heterojunction was confirmed by X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and UV-visible diffuse reflectance spectroscopy. The photocatalytic efficiency of the In₂S₃/BiVO₄ catalyst was examined over degradation of oxytetracycline hydrochloride (O-TCH) and oxygen (O₂) evolution reaction. Consequently, an n-n In₂S₃/BiVO₄ isotype heterojunction exhibits a superior O-TCH degradation efficiency (94.6%, 120 min) and O₂ evolution (695.76 μmol, 120 min) of multiple folds as compared to the pure BiVO₄ and In₂S₃ solely. This is attributed to the proper band alignment and intimate interfacial interaction promoted charge carrier separation over the n-n isotype heterojunction. The intimate interfacial contact was confirmed by transmission electron microscopy (TEM), high-resolution TEM, and field emission scanning electron microscopy analysis. The proper band alignment was confirmed by Mott-Schottky analysis. The photoelectrochemical linear sweep voltammetric study shows a superior photocurrent density (269 μA/cm²) for In₂S₃/BiVO₄ as compared to those for pristine BiVO₄ and In₂S₃, which is in good agreement with the photocatalytic results. Furthermore, the superior charge antirecombination efficiency of the n-n isotype heterojunction was established by photoluminescence, electrochemical impedance spectroscopy, Bode analysis, transient photocurrent, and carrier density analysis. The improved photostability of the heterojunction was confirmed by chronoamperometry analysis. An orderly corelationship among physicochemical, electrochemical, and photocatalytic properties was established, and a possible mechanistic pathway was presented to better understand the outcome of the n-n isotype heterojunction. This study presents an effective way to develop new n-n isotype heterojunction-based efficient photocatalysts and could enrich wide applications in other areas.

Evaluating the photocatalytic efficiency of the BiVO4/rGO photocatalyst

The present study reported the preparation of BiVO4 by co-precipitation method. The as-prepared BiVO4 photocatalyst were deposited on rGO sheets to form BiVO4/rGO via the hydrothermal method. The crystalline structure, morphological, optical properties, and surface properties of the synthesized pure BiVO4 compared to BiVO4/rGO composite were studied using X-ray diffraction (XRD), scanning electronmicroscopy (SEM), photoluminescence (PL) spectrophotoscopy, UV-vis spectrophotometer with an integrating sphere, and N2 adsorption-desorption isotherm based on BET theory. The photocatalytic activity of the prepared samples were evaluated by the degradation of MB dye in aqueous medium under visible light irradiation. The result showed that the BiVO4/rGO composite exhibited greater photocatalytic efficiency compared to pure BiVO4 with the photocatalytic degradation efficiency remains stable up to fifth cycle. The improved activity of the BiVO4/rGO composite might be attributed to the high surface area available to adsorb more MB molecules, and efficient charge separation of BiVO4 through π electron on the rGO structure. According to experimental results, the possible photocatalytic mechanism of the BiVO4/rGO composite were determined and the active species hydroxyl radical were reported. Based on photocatalytic activity inhibition in the presence of both h+ (VB) and O2•- (CB) scavengers over the BiVO4 photocatalyst, it can be proposed that the hydroxyl radical generated during the photocatalytic degradation mechanism is mainly responsible by the main active species of h+ and O2•- at VB and CB positions, respectively.

Construction of an artificial inorganic leaf CdS–BiVO4 Z-scheme and its enhancement activities for pollutant degradation and hydrogen evolution

An artificial inorganic leaf CdS–BiVO₄ micro-nano Z-scheme photocatalytic system was synthesized by the BT–DC–SILAR method taking a leaf as a template.