Sonochemical synthesis and characterization of Sm2CuO4 nanostructures and their application as visible-light photocatalyst for degradation of water-soluble organic pollutants

In recent years, water contamination has become a significant crisis, and it is crucial to find new materials that can efficiently eliminate these contaminants. The current work presents the Sm2CuO4 nanophotocatalyst for the decolorization of different water-soluble organic contaminants. The fabrication of Sm2CuO4 nanostructures was achieved using a simple and rapid sonochemical pathway, resulting in an optical bandgap of 1.62 eV as determined by diffuse reflectance spectroscopy. Several factors, including different organic contaminants, organic contaminant concentrations, Sm2CuO4 dosages, and the pH of the media, were scrutinized to achieve the best efficiency. The results manifested that Sm2CuO4 was highly effective in removing different organic contaminants from water. For example, when 30 mg of Sm2CuO4 was used with 20 mg L-1 methyl orange under visible irradiation for 100 min, 91.4% of the methyl orange was destroyed. Further investigation revealed that holes (h+) were primarily responsible for pollutant photodegradation when using Sm2CuO4 as a photocatalyst. This finding suggests that Sm2CuO4 could be an excellent candidate for developing new materials to effectively remove water contaminants.

Construction of g-C3N4/CdS/BiVO4 ternary nanocomposite with enhanced visible-light-driven photocatalytic activity toward methylene blue dye degradation in the aqueous phase

Herein, the ternary CdS/BiVO₄/g-C₃N₄ (CBG) hybrid semiconductor photocatalyst was prepared via a hydrothermal technique. The synthesized photocatalysts were thoroughly characterized using powder XRD, XPS, FTIR, SEM, TEM, and UV-DRS to investigate the microstructural, morphological attributes, and optical properties. The photocatalytic activity of the ternary CBG hybrid semiconductor was assessed through the photodegradation of Methylene Blue (MB) aqueous dye under visible light. The outcomes exhibited that the CBG hybrid semiconductor showed excellent photocatalytic activity (about 94.5% after 120 min) compared to the results obtained with the pristine materials or the other composite (CdS/BiVO₄). The enhancement of photocatalytic activity can be due to the construction of heterojunctions among g-C₃N₄, CdS, and BiVO₄, which improves charge transfer efficiency and hence favors the degradation of organic dyes. Moreover, the as-prepared photocatalyst showed excellent stability after five cycles, indicating good stability and reusability. Subsequently, a possible photocatalytic mechanism was proposed based on the experimental results. The current investigation provides a promising strategy to promote photocatalytic activity to eliminate waterborne contaminants.

WSe2/g-C3N4 for an In Situ Photocatalytic Fenton-like System in Phenol Degradation

An in situ photo-Fenton system can continuously generate H₂O₂ by photocatalysis, activating H₂O₂ in situ to form strong oxidizing ·OH radicals and degrading organic pollutants. A WSe₂/g-C₃N₄ composite catalyst with WSe₂ as a co-catalyst was successfully synthesized in this work and used for in situ photo-Fenton oxidation. The WSe₂/g-C₃N₄ composite with 7% loading of WSe₂ (CNW2) has H₂O₂ production of 35.04 μmol/L, which is fourteen times higher than pure g-C₃N₄. The degradation efficiency of CNW2 for phenol reached 67%. By constructing an in situ Fenton-system, the phenol degradation rate could be further enhanced to 90%. WSe₂ can enhance the catalytic activity of CNW2 by increasing electron mobility and inhibiting the recombination of photogenerated electron-hole pairs. Moreover, the addition of Fe²⁺ activates the generated H₂O₂, thus increasing the amount of strong oxidative ·OH radicals for the degradation of phenol. Overall, CNW2 is a promising novel material with a high H₂O₂ yield and can directly degrade organic pollutants using an in situ photo-Fenton reaction.

Photoelectrochemical H2 evolution on WO3/BiVO4 enabled by single-crystalline TiO2 overlayer modulations

Tungsten oxide/bismuth vanadate (WO₃/BiVO₄) has emerged as a promising photoanode material for photoelectrochemical (PEC) water splitting owing to its facilitated charge separation state differing significantly from single phase materials. Practical implementation of WO₃/BiVO₄ is often limited by poor stability arising from the leaching of V⁵⁺ from BiVO₄ during PEC operations. Herein, we demonstrate that the synthesis of a tungsten oxide/bismuth vanadate/titanium oxide (WO₃/BiVO₄/TiO₂) heterostructure onto a fluorine-doped tin oxide-coated glass substrate through a combined simple hydrothermal-spin coating strategy will advance PEC performance while slowing water oxidation kinetics and improving photostability. We show that surface postmodification with a nanometer-thick layer of (1 0 1) monofacet-selective single-crystalline TiO₂ provides stable photocurrent density, up to 1.04 mA cm^-2 at 1.23 V (compared to a reversible hydrogen electrode in 0.5 M Na₂SO₄), with excellent quantum efficiency (45% at 460 nm) and long-term photostability (24 h). Interestingly, crystalline TiO₂ activation layers behave differently from previous TiO₂ amorphous layers, blocking surface defects while improving corrosion resistance, photostability, and the electron transfer process. These results indicate a ≈2.5 times enhancement in photoelectrocatalytic activity related to referenced WO₃/BiVO₄ photoanodes, encouraging the use of single-crystalline TiO₂ modulations to develop a range of materials for PEC/photocatalytic applications.

Synthesis of vertical WO3 nanoarrays with different morphologies using the same protocol for enhanced photocatalytic and photoelectrocatalytic performances

Tungsten trioxide (WO3) nanoarrays with different morphologies were successfully synthesized by a hydrothermal method on an FTO substrate. Various nanostructures of WO3 including nanoflakes, nanoplates, nanoflowers and nanorods were obtained by adjusting only the acidity of the precursor solution. XRD patterns confirmed that the as-prepared orthorhombic WO3·0.33H2O transformed to the monoclinic WO3 phase under annealing at 500 °C. UV-Vis absorbance spectroscopy indicated that the absorption edge of WO3 nanoflowers exhibited a slight red-shift compared to other morphologies of WO3. The obtained WO3 nanoflower arrays exhibit the highest photocurrent density and photocatalytic degradation activity towards methylene blue. Finally, the mechanism of the photocatalytic degradation of methylene blue by WO3 is discussed.

Boosting photoresposive ability of WO3-Bi2O3nanocomposite rods via annealing-induced intrinsic precipitation of nanosized Bi particles

In this study, Bi-particle-functionalized tungsten trioxide-bismuth oxide (WO₃-Bi₂O₃) composite nanorods were prepared by integrating sputtering and hydrothermal syntheses with an appropriate postannealing procedure to induce Bi particle precipitation. Unlike other routes in which metal particle decoration is achieved externally, in this study, photoresponsive one-dimensional WO₃-Bi₂O₃composite nanorods were decorated with Bi particles by using the internal precipitation method. Structural analysis revealed that the Bi-metal-particle-functionalized WO₃-Bi₂O₃composite nanorods with particle size ranging from 5 to 10 nm were formed through hydrogen gas annealing at an optimal annealing temperature of 350 °C. Compared with the pristine WO₃nanorod template, the Bi-WO₃-Bi₂O₃composite nanorods exhibited higher photoresponsive performance, substantial photogenerated charge transfer ability, and efficient separation of photogenerated electron-hole pairs. The study results indicated that the Bi-WO₃-Bi₂O₃composite nanorods had superior decontamination ability and excellent stability toward RhB dye as compared with pristine WO₃. Moreover, the photogenerated charge separation and migration efficiencies of the WO₃-Bi₂O₃nanorods could be tuned through appropriate reduction of the surface oxide layer; this is a promising approach to designing WO₃-Bi₂O₃nanorods with high photoactive performance.

Surface Engineering of WO3/BiVO4 to Boost Solar Water-Splitting

Single-phase photoanodes often suffer inferior charge transport, which can be mitigated by constructing efficient heterojunctions. Thus, we have fabricated a fluorine-doped tin oxide (FTO)/WO3/BiVO4 heterojunction using hydrothermal and spin-coating methods. Surface engineering was exploited to further accelerate the reaction kinetics, which was achieved via post-modification with NaOH solution. This treatment alters the surface chemical state of the BiVO4 nanoparticles, leading to enhanced charge transport and surface water oxidation processes. As a result, the optimized sample can produce a photocurrent more than two times that of WO3. The simple post-treatment provides a viable and cost-effective strategy for promoting the photoelectric properties of photoanodes.

Solar-Light-Responsive Titanium-Sheet-Based Carbon Nanoparticles/B-BiVO4/WO3 Photoanode for the Photoelectrocatalytic Degradation of Orange II Dye Water Pollutant

We report the preparation and application of a heterostructured photoelectrocatalyst comprising carbon nanoparticles (CNPs) and boron codoped BiVO₄ and WO₃ for the removal of an organic dye pollutant in water. The materials, synthesized by hydrothermal method, were characterized by X-ray diffraction, diffuse reflectance UV-visible spectroscopy, energy-dispersive X-ray spectroscopy, and electron microscopy. The catalysts were immobilized on treated titanium sheets by drop-casting. The fabricated electrodes were characterized by linear sweep voltammetry (LSV) and chronoamperometry. Diffuse reflectance spectroscopy of the catalysts reveals that the incorporation of CNPs and B into the structure of monoclinic BiVO₄ enhanced its optical absorption in both UV and visible regions. The LSV measurements carried out in 0.1 M Na₂SO₄ showed that the BiVO₄- and WO₃-based photoelectrode demonstrated significant photoactivity. CNP/B-BiVO₄ and CNP/B-BiVO4/WO₃ photoanodes gave photocurrent densities of approximately 0.83 and 1.79 mA/cm², respectively, at 1.2 V (vs 3 M Ag/AgCl). The performance of the electrodes toward degradation of orange II dye was in the order BiVO₄ < B-BiVO₄ < WO₃ < CNP-BiVO₄ < CNP/B-BiVO₄ < CNP/B-BiVO₄/WO₃, and the apparent rate constants obtained by fitting the experimental data into the Langmuir Hinshelwood kinetic model are 0.0924, 0.1812, 0.254, and 0.845 h^-1 for BiVO₄, WO₃, CNP/B-BiVO₄, and CNP/B-BiVO₄/WO₃, respectively. The chemical oxygen demand abatement after 3 h of electrolysis at the best performing photoanode was 58%. The study showed that BiVO₄ and WO₃ are promising anodic materials for photoelectrocatalytic water treatment plant.

Enhanced Photoelectrochemical Water Splitting with Er- and W-Codoped Bismuth Vanadate with WO3 Heterojunction-Based Two-Dimensional Photoelectrode

A novel two-dimensional (2D) heterojunction photoelectrode composed of WO₃ and (Er,W):BiVO₄ is proposed for water oxidation with efficient photoinduced charge carrier separation and transfer. Er stoichiometric along with W nonstoichiometric codoping was introduced to simultaneously manage vacancy creation during substitutional doping, enhance light absorption, and reduce overall impedance. It was found that Er³⁺ is substituted at the Bi³⁺ sites in the BiVO₄ lattice to provide expanded light absorption from 400 to 680 nm. The fabricated WO₃/(Er,W):BiVO₄ electrode shows photocurrent densities of 4.1 and 7.2 mA cm^-2 at 1.23 and 2.3 V (vs reversible hydrogen electrode, RHE), respectively, under a 1 sun illumination in K₂HPO₄ electrolyte. This electrode has shown remarkably high charge separation efficiency of 93% at 1.23 V (vs RHE). With the addition of a standard surface catalyst (i.e., Co-Pi), the WO₃/(Er,W):BiVO₄/Co-Pi electrode exhibits the highest photocurrent of 5.6 ± 0.3 mA cm^-2 at 1.23 V (vs RHE), nearing the theoretical limit (i.e., 7.5 mA cm^-2) while retaining 98% of the photoelectrochemical cell performance after 3 h. By concomitantly doping the Bi³⁺ and V⁵⁺ sites to enhance absorption, this study demonstrates for the first time a planar WO₃/BiVO₄ heterojunction that reaches 88% of the record-high performance of its nanostructured counterpart. Through a detailed characterization of the electrodes, it is concluded that the stoichiometric Er and nonstoichiometric W codoping extend light absorption region and improve charge separation efficiency by reducing bulk resistance. The photoactive materials with 2D morphology were synthesized using a facile ultrasonic spray-coating technique without any complex process steps and thus it can be scaled for commercial development.

Multichannel Charge Transport of a BiVO4/(RGO/WO3)/W18O49 Three-Storey Anode for Greatly Enhanced Photoelectrochemical Efficiency

Photoelectrochemical (PEC) solar conversion is a green strategy for addressing the energy crisis. In this study, a three-storey nanostructure BiVO₄/(RGO/WO₃)/W₁₈O₄₉ was fabricated as a PEC photoanode and demonstrated a highly enhanced PEC efficiency. The top and middle storeys are a reduced graphene oxide (RGO) layer and WO₃ nanorods (NRs) decorated with BiVO₄ nanoparticles (NPs), respectively. The bottom storey is the W₁₈O₄₉ film grown on a pure W substrate. In this novel design, experiments and modeling together demonstrated that the RGO layer and WO₃ NRs with a fast carrier mobility can serve as multichannel pathways, sharing and facilitating electron transport from the BiVO₄ NPs to the W₁₈O₄₉ film. The high conductivity of W₁₈O₄₉ can further enhance the charge transfer and retard electron-hole recombination, leading to a highly improved PEC efficiency of the BiVO₄/WO₃ heterojunction. As a result, the as-fabricated three-storey photoanode covered with FeOOH/NiOOH achieves an attractive PEC photocurrent density of 4.66 mA/cm² at 1.5 V versus Ag/AgCl, which illustrates the promising potential of the three-storey hetero-nanostructure in future photoconversion applications.

Electrospun BiVO4 nanobelts with tailored structures and their enhanced photocatalytic/photoelectrocatalytic activities

We reported the fabrication of BiVO₄ nanobelts with tailored structures by a versatile electrospinning method.