Bioinspired hierarchical 3D flower-in-ridge hybrid structure for the photodegradation of persistent organic pollutants

The development of next-generation photocatalysts has consistently gained inspiration from the evolution of natural nanostructures regarding their fabrication and application for the elimination of persistent organic pollutants (POPs). Herein, we synthesized blue-colored oxygen-vacant Bi₂WO_6-x inside butterfly wing architectures (BW-Bi₂WO_6-x) via modified functionalization and solvothermal techniques. Given that the (WO₄)^2- layer in Bi₂WO₆ structurally resembles the structure of WO₃, the introduction of oxygen vacancies (OVs) boosts the solar light absorption in comparison to the short visible light absorption range (<450 nm) in pristine Bi₂WO₆ (P-Bi₂WO₆). Hence, the fabricated BW-Bi₂WO_6-x sample exhibited broadened photo-absorption over the visible to NIR wavelength range, improved semiconductor attachment on the wing architecture and heightened surface area with numerous active sites for the adsorption of POP molecules. The performance of the BW-Bi₂WO_6-x photocatalyst was monitored for the elimination of methylene blue (MB), rhodamine B (RhB) and 4-chlorophenol (4-CP) under UV light exposure, yielding 91%, 92% and 94% degradation, respectively, in 60 min. Similarly, the degradation efficiencies of 94%, 98% and 98% for the photodegradation of MB, RhB and 4-CP under visible light for 60 min, respectively, were observed. Under NIR light, 80%, 79% and 85% degradation efficiencies were observed for MB, RhB and 4-CP, respectively, after 60 min. Therefore, the proposed BW-Bi₂WO_6-x sample can provide insights and inspire the development of photo-responsive materials for applications in energy, defense and water treatment.

A readily synthesized bismuth oxyiodide/attapulgite for the photodegradation of tetracycline under visible light irradiation

Bismuth oxyiodide and attapulgite have proven to be potential materials for the removal of emerging contaminants in wastewater.

Fabrication of one dimensional hierarchical WO3/BiOI heterojunctions with enhanced visible light activity for degradation of pollutants

One-dimensional (1D) hierarchical WO₃/BiOI p–n (WB) heterojunctions with different mass percentages of WO₃ were fabricated through a precipitation process. Various analytical techniques were employed to characterize the resulting WB composites, and their photocatalytic properties were measured by the degradation of rhodamine B (RhB) and methylene blue (MB) under irradiation of visible light. The WB heterojunctions showed largely enhanced photocatalytic performance as compared to the pure photocatalysts. Notably, the degradation rate constant of RhB by WB-10 was 3.3 and 33.6 times higher than those of pure BiOI and WO₃, respectively. The enhanced activity could be attributed to the hierarchical p–n heterostructures, which can supply more reaction sites and effectively promote the separation of photogenerated charge carriers, as confirmed by PL and photocurrent. Trapping experiments implied that holes (h⁺) and superoxide anion radicals (˙O₂⁻) were the dominant active species for organic pollutants decomposition on the WB composites. This work may benefit the construction of hierarchical heterostructures with high photocatalytic efficiency.

One-dimensional (1D) hierarchical WO₃/BiOI p–n (WB) heterojunctions with different mass percentages of WO₃ were fabricated through a precipitation process.

Green biomimetic preparation of efficient Ag-ZnO heterojunctions with excellent photocatalytic performance under solar light irradiation: a novel biogenic-deposition-precipitation approach

Herein, we report a unique single-step biogenic deposition precipitation (BDP) approach as a straightforward route for producing efficient Schottky contact between noble metal nanoparticles and wide-band-gap semiconductors. Successful preparation of Ag-ZnO heterojunctions using fennel seed extract (FSE) has been described. The effective biomolecules available in the seeds functioned as novel biogenic materials for the precipitation of adsorbed silver ions (Ag⁺) on ZnO particles as metallic silver (Ag⁰). The as-prepared composite materials were characterized using diffuse reflectance spectroscopy (DRS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), energy dispersive X-ray (EDX) study, X-ray photoelectron spectroscopy (XPS), photoluminescence spectroscopy (PL) and high-resolution transmission electron microscopy (HR-TEM). The biogenically prepared Ag-ZnO nanocomposites exhibited excellent photocatalytic activity towards reduction/degradation of colored (rhodamine B (Rh-B) dye) as well as colorless (chlorpyrifos pesticide) pollutants when irradiated under solar light. Among the prepared photocatalysts, 3 wt% Ag-ZnO hybrid composite showed the best photocatalytic activity by efficiently degrading hazardous organic pollutants within a very short time. The superior photocatalytic performance of biogenically prepared Ag-ZnO heterojunctions can be ascribed to the clean production of steady and efficient Schottky contact between plasmonic AgNPs and semiconducting ZnO NPs.

Visible-light-driven activity and synergistic mechanism of TiO2@g-C3N4 heterostructured photocatalysts fabricated through a facile and green procedure for various toxic pollutants removal

Heterostructured photocatalysts based on g-C₃N₄ and TiO₂ represent a promising kind of photocatalyst in environmental fields, but the synthesis methods are always complex and not green. In the present paper, a facile and green one-step calcination procedure at lower temperature (450 °C) with the assistance of water is developed to synthesize a visible-light-active TiO₂@g-C₃N₄ heterostructured photocatalyst, which shows higher visible-light-driven activity (k = 0.014 min^-1) than pure g-C₃N₄ (k = 0.0036 min^-1) and TiO₂ (k = 0.0067 min^-1) for methyl orange degradation. Excellent performance (over 90% conversion) was also observed for the removal of rhodamine B, phenol, and Cr(VI) under visible light. The heterostructured photocatalyst showed favorable reusability, preserving 86% of its activity after five successive cycles. A mechanism study demonstrates that the enhanced photocatalytic activity results from the efficient separation of the photo-generated charge carriers through the intimate interface between the two semiconductors based on their appropriate band structures and light-induced mechanism. The heterostructured photocatalyst will certainly find wide applications in the treatment of various toxic pollutants in wastewater using abundant solar energy. Furthermore, this facile and green procedure and the proposed synergistic mechanism will provide guidelines in designing other g-C₃N₄ based organic-inorganic composite photocatalysts for various applications.

Enhanced photocatalytic activity of Bi12O17Cl2 nano-sheets via surface modification of carbon nanotubes as electron carriers

A novel carbon nanotubes modified Bi₁₂O₁₇Cl₂ composite (CNTs/Bi₁₂O₁₇Cl₂) was prepared via hydrothermal method. The chemical structures, morphologies, optical properties of the synthesized samples were revealed by XRD, XPS, SEM, TEM, BET and UV-vis DRS measurements. The photocatalytic activity of the CNTs/Bi₁₂O₁₇Cl₂ composite was evaluated with degradation reaction of rhodamine B (RhB) under visible light. CNTs/Bi₁₂O₁₇Cl₂ exhibited improved photocatalytic activity in comparison with pure Bi₁₂O₁₇Cl₂, and kept favorable stability and recyclability in the reaction. The relatively high photocatalytic activity of CNTs/Bi₁₂O₁₇Cl₂ resulted from the enhanced separation efficiency of photo-induced charges, which were revealed by the photoluminescence spectra and transient photocurrent measurements. CNTs loaded at the surface of Bi₁₂O₁₇Cl₂ sheets acted as electron carriers to efficiently transfer the photoinduced electrons, namely to promote the separation of photoinduced electrons and holes, thus improving the photocatalytic activity of the composite materials. At last, a possible photocatalytic reaction mechanism over the CNTs/Bi₁₂O₁₇Cl₂ composite was proposed based on the results of trapping experiment, ESR measurements and the band energy analysis.

Green synthesis of balsam pear-shaped BiVO4/BiPO4 nanocomposite for degradation of organic dye and antibiotic metronidazole

A novel balsam pear-shaped BiVO₄/BiPO₄ composite photocatalyst for a highly efficient degradation of organic dye and antibiotic was fabricated.

Construction of 2D/2D layered g-C3N4/Bi12O17Cl2 hybrid material with matched energy band structure and its improved photocatalytic performance

A series of visible-light-induced 2D/2D layered g-C₃N₄/Bi₁₂O₁₇Cl₂ composite photocatalysts were successfully synthesized by a one step chemical precipitation method with g-C₃N₄, BiCl₃ and NaOH as the precursors at room temperature and characterized through XRD, FTIR, XPS, TEM, BET and UV-vis DRS measurements. The results of XRD, FTIR and XPS indicated that g-C₃N₄ has been introduced in the Bi₁₂O₁₇Cl₂ system. The TEM image demonstrated that there was strong surface-to-surface contact between 2D g-C₃N₄ layers and Bi₁₂O₁₇Cl₂ nanosheets, which contributed to a fast transfer of the interfacial electrons, leading to a high separation rate of photoinduced charge carriers in the g-C₃N₄/Bi₁₂O₁₇Cl₂ system. Rhodamine B was considered as the model pollutant to investigate the photocatalytic activity of the resultant samples. The g-C₃N₄/Bi₁₂O₁₇Cl₂ composite showed a clearly improved photocatalytic degradation capacity compared to bare g-C₃N₄ and Bi₁₂O₁₇Cl₂, which was ascribed to the interfacial contact between the 2D g-C₃N₄ layers and Bi₁₂O₁₇Cl₂ sheet with a matched energy band structure, promoting the photoinduced charges' efficient separation. Finally, combined with the results of the trapping experiment, ESR measurements and the band energy analysis, a reasonable photocatalytic mechanism over the 2D/2D layered g-C₃N₄/Bi₁₂O₁₇Cl₂ composite was proposed.

Surface-to-surface contact g-C₃N₄/Bi₁₂O₁₇Cl₂ hybrid material with a matched energy band structure could efficiently transfer photoinduced charges, improving the photocatalytic activity.