CeO2/Bi2MoO6 heterostructured microspheres with synergistic effect for accelerating photogenerated charge separation

CeO2 nanospheres incorporated with Bi2MoO6/g-C3N4 enhanced photocatalysis towards environmental pollutant Rhodamine B removal

We have adopted a novel CeO2/Bi2MoO6/g-C3N4-based ternary nanocomposite that was synthesized via hydrothermal technique. The physiochemical characterization of as-prepared samples was examined through various analytical techniques such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy TEM, photoluminescent spectra (PL), X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET), and ultraviolet diffuse reflectance spectroscopy (UV-DRS) technique. In addition, the photocatalytic performance was carried out by degradation of Rhodamine B dye under visible light irradiation using this nanocatalyst. The ternary nanocomposite achieved 94% of the degradation efficiency within 100 min which is higher than the pristine and binary composites under the predetermined condition pH = 7, Rhodamine B dye = 5 mg/L, and catalyst concentration = 150 mg/L. The experimental synergetic effect of CeO2/Bi2MoO6/g-C3N4 ternary nanocomposite has been ascribed to the interfacial charge carrier migration between CeO2, Bi2MoO6, and g-C3N4. The optical absorption range of CeO2/Bi2MoO6/g-C3N4 ternary nanocomposite was enhanced, and the band gap was reduced up to 2.2 eV. In addition, scavenger trapping experiment proves that the super oxide anions (O2-.) and photogenerated holes are the major active species. The reusability and stability experiment proved the CeO2/Bi2MoO6/g-C3N4 ternary nanocomposite keeps good durability during the photocatalytic degradation process after the five successive cycles. Furthermore, based on the results, the charge carrier transfer photocatalytic mechanism was also discussed. This CeO2/Bi2MoO6/g-C3N4 ternary nanocomposite may offer the cheapest material and extend the great opportunity for clean and environmental remediation approach under the visible light irradiation.

Research status and prospect of nano silver (Ag)-modified photocatalytic materials for degradation of organic pollutants

Nano silver (Ag) was metallic Ag monomers with particle size to the nanoscale. Photocatalyst was a kind of semiconductor material with photocatalytic function. Loading precious metal Ag onto semiconductor surfaces by microwave, laser-induced, solvent-thermal and hydrothermal methods could capture photogenerated electrons, reduced the compounding rate of holes and photogenerated electrons during the photocatalytic process, thereby improving the electron transfer efficiency of photocatalysis and enhancing the absorption of visible light by silver nanoparticles through the plasma resonance effect. The highly reactive free radicals produced by photocatalysts were used in the organic degradation process to degrade organic matter into inorganic matter and was a faster, more efficient and less polluting method of pollutant degradation, which has attracted a lot of attention from researchers. This review discussed the modification of various types of photocatalysts by nano Ag through different methods. The photocatalytic degradation of dyes, antibiotics and persistent organic pollutants by different modified composites was also analyzed. This review covered the several ways and means in which nano Ag has modified diverse photocatalytic materials as well as the photocatalytic degradation of dyes, antibiotics and persistent organic pollutants. This review identified the drawbacks of the existing nano Ag-modified photocatalytic materials, including their low yield and lack of recyclability, and it also offered suggestions for potential future directions for their improvement. The purpose of this review was to further research on the technology of nano Ag-modified photocatalytic materials and to encourage the creation of new modified photocatalytic nanomaterials for the treatment of organic pollutant degradation.

The synergistic degradation of pollutants in water by photocatalysis and PMS activation

In recent years, the synergistic degradation of water pollutants through advanced oxidation technology has emerged as a prominent research area due to its integration of various advanced oxidation technologies. The combined utilization of peroxymonosulfate (PMS) activation technology and photocatalysis demonstrates mild and nontoxic characteristics, enabling the degradation of water pollutants across a wide pH range. Moreover, this approach reduces the efficiency of electron hole recombination, broadens the catalyst's light response range, facilitates electron transfer of PMS, and ultimately improves its photocatalytic performance. The paper reviews the current research status of photocatalytic technology and PMS activation technology, respectively, while highlighting the advancements achieved through the integration of photocatalytic synergetic PMS activation technology for water pollutant degradation. Furthermore, this review delves into the mechanisms involving both free radicals and nonradicals in the reaction process and presents a promising prospect for future development in water treatment technology. PRACTITIONER POINTS: Degradation of water pollutants by photocatalysis and PMS synergistic action has emerged. Synergism can enhance the generation of free radicals. This technology can provide theoretical support for actual wastewater treatment.

Enhancing Visible Light Photocatalytic Degradation of Bisphenol A Using BiOI/Bi2MoO6 Heterostructures

With the growing population, access to clean water is one of the 21st-century world's challenges. For this reason, different strategies to reduce pollutants in water using renewable energy sources should be exploited. Photocatalysts with extended visible light harvesting are an interesting route to degrade harmful molecules utilized in plastics, as is the case of Bisphenol A (BPA). This work uses a microwave-assisted route for the synthesis of two photocatalysts (BiOI and Bi₂MoO₆). Then, BiOI/Bi₂MoO₆ heterostructures of varied ratios were produced using the same synthetic routes. The BiOI/Bi₂MoO₆ with a flower-like shape exhibited high photocatalytic activity for BPA degradation compared to the individual BiOI and Bi₂MoO₆. The high photocatalytic activity was attributed to the matching electronic band structures and the interfacial contact between BiOI and Bi₂MoO₆, which could enhance the separation of photo-generated charges. Electrochemical, optical, structural, and chemical characterization demonstrated that it forms a BiOI/Bi₂MoO₆ p-n heterojunction. The free radical scavenging studies showed that superoxide radicals (O₂•^-) and holes (h⁺) were the main reactive species, while hydroxyl radical (•OH) generation was negligible during the photocatalytic degradation of BPA. The results can potentiate the application of the microwave synthesis of photocatalytic materials.

Facile synthesis of ternary dual Z-scheme g-C3N4/Bi2MoO6/CeO2 photocatalyst with enhanced 4-chlorophenol removal: Degradation pathways and mechanism

The design of visible-light-driven photocatalysts has been rapidly developed due to the great application potential in environmental pollution remediation. The present work focused on the construction of a novel ternary g-C₃N₄/Bi₂MoO₆/CeO₂ nanocomposite and the application for photocatalytic removal of 4-CP under irradiation. The g-C₃N₄/Bi₂MoO₆/CeO₂ photocatalysts were successfully synthesized by a facile solid-state thermolysis assisted ultrasonic dispersion to introduce g-C₃N₄ nanosheets into Bi₂MoO₆/CeO₂ composite. Morphology characterization revealed that the Bi₂MoO₆/CeO₂ spherical structure uniformly dispersed on the g-C₃N₄ nanosheets and the close interface contact induced the generation of dual Z-scheme heterojunction. The as-prepared photocatalysts shown enhanced catalytic activity in comparison with binary Bi₂MoO₆/CeO₂ composites and the optimal CBC-20% exhibited the highest degradation efficiency of 99.1% for 4-CP under 80 min illumination, which was attributed to the efficient separation of photogenerated e^--h⁺ pairs under the dual Z-scheme charges transfer mode. Additionally, combined with trapping experiments and EPR analysis, 4-CP was decomposed mainly by the active species ^•O₂^- and h⁺ with a marginal assistance of ^•OH during the photocatalytic process. The intermediates for 4-CP degradation were analyzed and a reasonable degradation pathway was proposed.

Sunlight-induced enhanced photocatalytic reduction of chromium (VI) and photocatalytic degradation of methylene blue dye and ciprofloxacin antibiotic by Sn3O4/SnS2 nanocomposite

Detection of residual organic and inorganic species in water bodies, including drinking water, has led to developing strategies for their removal. Here, we report a very efficient method of removing Cr(VI), organic dye, and antibiotic from water using a type-II heterojunction based on Sn₃O₄/SnS₂ solar photocatalyst. The toxic Cr(VI) species are reduced by photocatalytic methodology, while methylene blue (MB) dye and ciprofloxacin (CIP) antibiotics are removed by photocatalytic degradation. The structural, compositional, morphological, and optical properties of the hydrothermally synthesized photocatalyst have been studied. Under sunlight exposure, more than 99.9% of Cr(VI) is reduced within 60 min at a reaction rate of 0.066 min^-1. While 99.6% of MB and 90% of CIP degradation are achieved in 90 min and 120 min, corresponding to photocatalytic degradation rates of 0.043 min^-1 and 0.019 min^-1, respectively. The total organic carbon after degradation corresponded to 85.1% for MB and 72.4% for CIP mineralization. The observed photocatalytic degradation is attributed to in situ generation of reactive oxygen species (ROS), e.g., superoxide radicals and hydroxyl radicals. The role of ROS towards photocatalytic degradation of MB and CIP, respectively, was confirmed from ROS scavenging studies. The MB and CIP degradation mechanism has been discussed by analyzing their degradation products.

A high-efficiency mediator-free Z-scheme Bi2MoO6/AgI heterojunction with enhanced photocatalytic performance

A high-efficiency Z-scheme Bi₂MoO₆/AgI heterojunction was designed and fabricated via in situ growth of AgI on Bi₂MoO₆. Its photocatalytic activity was investigated with the degradation of malachite green (MG). After 40 min of visible light irradiation, near complete degradation of MG (20 mg/L) occurred when BA11 (Bi₂MoO₆:AgI = 1:1, 2.0 g/L) was present, while only 29.0% and 49.7% of the MG could be degraded in the presence of Bi₂MoO₆ and AgI, respectively. The excellent photocatalytic activity of BA11 results from strong visible light absorption and the low recombination efficiency of photogenerated electron-hole pairs induced by the formation of heterojunction. Density function theory (DFT) calculations revealed that the formation of built-in electric field at the interface between Bi₂MoO₆ and AgI facilitates the effective separation and transfer of photogenerated charge carriers. Results of reuse experiments indicated that the heterostructured photocatalyst has excellent stability. Radical scavenging experiments and electron spin resonance spectra showed that superoxide radicals (O₂^-) and hydroxyl radicals (OH) were the major reactive oxygen species in the photocatalytic system. The photocatalytic degradation pathway of MG was proposed based on the organic degradation intermediates detected. These findings demonstrate that the mediator-free Z-scheme Bi₂MoO₆/AgI heterojunction could serve as a promising photocatalyst in photocatalytic treatment of organic pollutants.

Construction of visible-light driven Bi2MoO6-rGO-TiO2 photocatalyst for effective ofloxacin degradation

Photocatalytic removal is more appropriate for the destruction of organic contaminants. The ternary Bi₂MoO₆-reduced graphene oxide (rGO)-TiO₂ catalyst was synthesized using a simple hydrothermal method, and various surface analytical optical techniques were analyzed. The photocatalytic decomposition efficiency of the Bi₂MoO₆-rGO-TiO₂ composite was 92.3% higher than those of pure and binary photocatalysts. The effects of operational parameters, such as catalyst ratio, catalyst variation, rGO ratio variation, and pH value variation were also analyzed. The as-prepared ternary photocatalyst exhibited low photoluminescence and high photocurrent density, which suppressed photon-induced electron and hole (h⁺) recombination and effective charge separation. The study demonstrated that rGO has excellent electron transfer performance and enhanced photocatalytic reaction stability. The perfect cycling stability of Bi₂MoO₆-rGO-TiO₂ was retained even after five consecutive cycles on the photocatalytic degradation reaction performance. In this study, we propose a decomposition performance mechanism for ofloxacin degradation that underwent visible-light irradiation.

Efficient reduction of Cr(VI) by a BMO/Bi2S3 heterojunction via synergistic adsorption and photocatalysis under visible light

The development of efficient visible light driven photocatalyst is the premise of the progress of photocatalytic technology. In this paper, a well-designed orthorhombic Bi₂MoO₆/Bi₂S₃ (BMO/Bi₂S₃) composite was obtained by a two-step fabrication route. Using MoO₃ nanobelt as a sacrificial template, BMO nanosheet-based framework was prepared by refluxing process. Through anion exchange reaction of the synthesized BMO to introduce Bi₂S₃ nanosheets, and BMO/Bi₂S₃ heterojunction was successfully constructed. Simultaneously, the Bi₂S₃ loading percentage of BMO/Bi₂S₃ was controlled by tuning the anion exchange time. The intimate interfacial contact between the BMO framework and Bi₂S₃ nanosheets endows the nanocomposites with high adsorption and photocatalytic removal of Cr(VI). Photocatalytic tests show that BMO/Bi₂S₃-1 composite possess the highest activity with 100 % removal rate of Cr(VI) in 15 min. The dramatically enhanced adsorption and photocatalytic capacity of BMO/Bi₂S₃ photocatalysts can be ascribed to the frame structure, large surface area and numerous nanochannels. In addition, the BMO/Bi₂S₃ photocatalyst is highly stable during the reaction and can be used repeatedly. These features indicate that the BMO/Bi₂S₃ composite could be used for environmental remediation and wastewater treatment.

In situ fabrication of I-doped Bi2O2CO3/g-C3N4 heterojunctions for enhanced photodegradation activity under visible light

Iodine-doped Bi₂O₂CO₃/g-C₃N₄ heterojunctions consisting of graphitic carbon nitride (g-C₃N₄) and iodine-doped bismutite (Bi₂O₂CO₃) components were successfully in situ synthesized by a one-pot hydrothermal method. Characterizations such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and scanning electron microscope (SEM) demonstrated iodine was favorably doped into the Bi₂O₂CO₃ component, of which the {001} facets grew in situ from {002} facets of g-C₃N₄ for the heterostructure construction of I-doped Bi₂O₂CO₃/g-C₃N₄ (IB/CN). The photocatalytic activity of catalysts was evaluated by the degradation efficiency of 1,5-dihydroxynaphthalene under visible light. 1.5-IB/CN with a reasonable iodine doping amount (Bi: I molar ratio = 1.0: 1.5) exhibited the superior photodegradation performance compared to Bi₂O₂CO₃, achieving an 85.5% removal ratio after 100 min illumination. The enhanced activity of 1.5-IB/CN was attributed to both of the heterostructure that promoted the separation of photoinduced carriers and iodine doping that tuned the bandgap for sufficient visible-light harvesting. The degradation intermediates of 1,5-dihydroxynaphthalene in the system were determined and its possible photodegradation pathway was proposed in detail. This study provides a rational approach for enhancing the visible-light catalytic activity of wide-bandgap Bi₂O₂CO₃, and reveals a new perspective on the removal mechanism of organic pollutants.

Bio-inspired construction of melanin-like polydopamine-coated CeO2 as a high-performance visible-light-driven photocatalyst for hydrogen production

In recent years, cerium oxide has been the most widely studied photocatalyst due to its unique properties.