Highly efficient degradation of reactive black KN-B dye by ultraviolet light responsive ZIF-8 photocatalysts with different morphologies

Zeolitic imidazolate framework ZIF-8, a type of metal-organic framework, has diverse applications in multiple catalytic fields due to its outstanding properties. Herein, ZIF-8 photocatalysts with three different morphologies (dodecahedral, pitaya-like, and leaf-like) are successfully synthesized under ambient conditions from zinc salts by altering the volume ratio of methanol and water used as a solvent. The as-synthesized ZIFs have high crystallinity with distinct BET surface areas. The experiments indicate that the ZIFs have high photocatalytic efficiency, in which the leaf-like structure (ZIF-8-F3) is the most efficient in the degradation of reactive black KN-B dye (RB5) under 365 nm UV irradiation. This is due to the efficient inhibition of electron-hole recombination or the higher migration of charge carriers in ZIF-8-F3, thus producing more reactive oxygen species, resulting in greater photocatalytic efficiency. At pH = 11, more than 95% of RB5 is degraded within 2 hours when using 1.0 g L^-1 of ZIF-8-F3. Besides, the photocatalytic and kinetic performances of ZIF-8-F3 are also investigated by optimizing the pH, initial RB5 concentration, and dosage of the used catalyst. These ZIF-8-F3 plates have been shown to be a promising material with high photostability and effective reusability, beneficial to various potential applications in environmental remediation issues.

Synthesis of flower-like MoS2/CNTs nanocomposite as an efficient catalyst for the sonocatalytic degradation of hydroxychloroquine

Contamination of water resources by pharmaceutical residues, especially during the time of pandemics, has become a serious problem worldwide and concerns have been raised about the efficient elimination of these compounds from aquatic environments. This study has focused on the development and evaluation of the sonocatalytic activity of a flower-like MoS₂/CNTs nanocomposite for the targeted degradation of hydroxychloroquine (HCQ). This nanocomposite was prepared using a facile hydrothermal route and characterized with various analytical methods, including X-ray diffraction and electron microscopy, which results confirmed the successful synthesis of the nanocomposite. Moreover, the results of the Brunauer-Emmett-Teller and diffuse reflectance spectroscopy analyses showed an increase in the specific surface area and a decrease in the band gap energy of the nanocomposite when compared with those of MoS₂. Nanocomposites with different component mass ratios were then synthesized, and MoS₂/CNTs (10:1) was identified to have the best sonocatalytic activity. The results indicated that 70% of HCQ with the initial concentration of 20 mg/L could be degraded using 0.1 g/L of MoS₂/CNTs (10:1) nanocomposite within 120 min of sonocatalysis at the pH of 8.7 (natural pH of the HCQ solution). The dominant reactive species in the sonocatalytic degradation process were identified using various scavengers and the intermediates generated during the process were detected using GC-MS analysis, enabling the development of a likely degradation scheme. In addition, the results of consecutive sonocatalytic cycles confirmed the stability and reusability of this nanocomposite for sonocatalytic applications. Thus, our data introduce MoS₂/CNTs nanocomposite as a proficient sonocatalyst for the treatment of pharmaceutical contaminants.

The role of sodium dodecyl sulfate mediated hydrothermal synthesis of MoS2 nanosheets for photocatalytic dye degradation and dye-sensitized solar cell application

The novel properties and exciting behavior of two-dimensional nanosheet-based materials have piqued the interest of research all over the world. In this study, bulk molybdenum disulfide (bulk MoS₂) and sodium dodecyl sulfate-mediated molybdenum disulfide nanosheets (MoS₂-SDS NS) were synthesized via a facile sonication and hydrothermal process. The findings from the characterization revealed that the addition of sodium dodecyl sulfate (SDS) surfactant reduces the crystal phase and changes the structural morphology of bulk MoS₂. Furthermore, the photocatalytic and photovoltaic performance of bulk MoS₂ and MoS₂-SDS NS were also investigated. The results show that by using methylene blue dye, the photocatalytic efficiency increased from 56.30% to 91.84% at 150 min under UV-Visible light irradiation, and the photo-conversion efficiency (PEC (%)) of the dye-sensitized solar cell increased from 1.47% to 3.81% for bulk MoS₂ and MoS₂-SDS NS, respectively. Finally, we discussed in-depth the effect of SDS surfactants on MoS₂, which can improve their photovoltaic and photocatalytic performance.

Interface enriched highly interlaced layered MoS2/NiS2 nanocomposites for the photocatalytic degradation of rhodamine B dye

In the past few decades, air and water pollution by organic dyes has become a serious concern due to their high toxicity. Removal of these organic dyes from polluted water bodies is a serious environmental concern and the development of new advanced photocatalytic materials for decomposing organic dyes can be a good solution. In this work, layered molybdenum disulfide/nickel disulfide (MoS₂/NiS₂) nanocomposites with various NiS₂ content was synthesized by a one-step hydrothermal method using citric acid as a reducing agent. The X-ray diffraction pattern shows the hexagonal and cubical crystal structure of MoS₂ and NiS₂, respectively. Morphological analysis confirms the formation of MoS₂/NiS₂ nanosheets. The elemental composition of the samples was carried out by XPS, which shows a significant interaction between NiS₂ and MoS₂. The photocatalytic performance of MoS₂/NiS₂ nanocomposites was studied by the degradation of rhodamine B (RhB). Ni-4 sample shows higher photocatalytic activity with a maximum degradation of 90.61% under visible light irradiation for 32 min.

The photocatalytic performance of MoS₂/NiS₂ nanocomposites was studied by the degradation of rhodamine B (RhB). Ni-4 sample shows higher photocatalytic activity with a maximum degradation of 90.61% under visible light irradiation for 32 min.

Recent advances in photodegradation of antibiotic residues in water

Antibiotics are widely present in the environment due to their extensive and long-term use in modern medicine. The presence and dispersal of these compounds in the environment lead to the dissemination of antibiotic residues, thereby seriously threatening human and ecosystem health. Thus, the effective management of antibiotic residues in water and the practical applications of the management methods are long-term matters of contention among academics. Particularly, photocatalysis has attracted extensive interest as it enables the treatment of antibiotic residues in an eco-friendly manner. Considerable progress has been achieved in the implementation of photocatalytic treatment of antibiotic residues in the past few years. Therefore, this review provides a comprehensive overview of the recent developments on this important topic. This review primarily focuses on the application of photocatalysis as a promising solution for the efficient decomposition of antibiotic residues in water. Particular emphasis was laid on improvement and modification strategies, such as augmented light harvesting, improved charge separation, and strengthened interface interaction, all of which enable the design of powerful photocatalysts to enhance the photocatalytic removal of antibiotics.

Fabrication of Hierarchical Co9S8@ZnAgInS Heterostructured Cages for Highly Efficient Photocatalytic Hydrogen Generation and Pollutants Degradation

In the present study, a hierarchical Co₉S₈@ZnAgInS heterostructural cage was developed for the first time which can photocatalytically produce hydrogen and degrade organic pollutants with high efficiency. First, the Co₉S₈ dodecahedron was synthesized using a metal-organic framework (MOFs) material, ZIF-67, as a precursor, then two kinds of metal sulfide semiconductors were elaborately integrated into a hierarchical hollow heterostructural cage with coupled heterogeneous shells and 2D nanosheet subunits. The artfully designed hollow heterostructural composite exhibited remarkable photocatalytic activity without using any cocatalysts, with a 9395.3 μmol g^-1 h^-1 H₂ evolution rate and high degradation efficiency for RhB. The significantly enhanced photocatalytic activity can be attributed to the unique architecture and intimate-contact interface between Co₉S₈ and ZnAgInS, which promote the transfer and separation of the photogenerated charges, increase light absorption, and offer large surface area and active sites. This work presents a new strategy to design highly active semiconductor photocatalysts by using MOF materials as precursors and coupling of metal sulfide semiconductors to form hollow architecture dodecahedron cages with an intimate interface.

Synthesis and characterization of vanadium-doped Mo(O,S)2 oxysulfide for efficient photocatalytic degradation of organic dyes

We developed simple and low cost synthesis methods at low temperature to synthesize V-doped Mo(O,S)₂ for the photocatalytic degradation of dyes.

Addition of MnO2 in synthesis of nano-rod erdite promoted tetracycline adsorption

Erdite is a rare sulphide mineral found in mafic and alkaline rocks. Only weakly crystallised fibrous erdite has been artificially synthesised via evaporation or the hydrothermal method, and the process generally requires 1–3 days and large amounts of energy to complete. In this study, well-crystallised erdite nanorods were produced within 3 h by using MnO₂ as an auxiliary reagent in a one-step hydrothermal method. Results showed that erdite could synthesised in nanorod form with a diameter of approximately 200 nm and lengths of 0.5–3 μm by adding MnO₂; moreover, the crystals grew with increasing MnO₂ addition. Without MnO₂, erdite particles were generated in irregular form. The capacity of the erdite nanorods for tetracycline (TC) adsorption was 2613.3 mg/g, which is higher than those of irregular erdite and other reported adsorbents. The major adsorption mechanism of the crystals involves a coordinating reaction between the −NH₂ group of TC and the hydroxyl group of Fe oxyhydroxide produced from erdite hydrolysis. To the best of our knowledge, this study is the first to synthesise erdite nanorods and use them in TC adsorption. Erdite nanorods may be developed as a new material in the treatment of TC-containing wastewater.

Platinum-enhanced amorphous TiO2-filled mesoporous TiO2 crystals for the photocatalytic mineralization of tetracycline hydrochloride

The adsorption ability and photoactivity of a photocatalyst largely determine the mineralization efficiency of antibiotics. Herein, aiming to enhance the adsorption and mineralization of antibiotics, we constructed a hierarchical porous core-shell structure by filling amorphous TiO₂ in the pores of Pt-doped mesoporous TiO₂ crystals (MCs). The physical-chemical properties of the prepared samples were investigated by surface photovoltage spectroscopy, X-ray photoelectron spectroscope, etc. Adsorption and photocatalysis experiments were conducted with tetracycline hydrochloride as the model antibiotic. Pt nanoparticles doped at the interface of the rutile-amorphous homojunction remarkably enhanced the built-in electric field. The enhanced electric field increased the hole transfer to the catalyst surface, and the Pt doping treatment promoted the growth of amorphous TiO₂ into the mesopores of the MCs. The optimization increased the surface area of the catalyst without increasing the thickness of the amorphous TiO₂ shell, thereby reducing the charge migration distance from the core-shell interface to the catalyst surface. The adsorption amount and mineralization efficiency of tetracycline hydrochloride for the porous core-shell composite were 6.7 and 3.8 times of those for MCs, respectively.

Solar light harvesting with multinary metal chalcogenide nanocrystals

The paper reviews the state of the art in the synthesis of multinary (ternary, quaternary and more complex) metal chalcogenide nanocrystals (NCs) and their applications as a light absorbing or an auxiliary component of light-harvesting systems. This includes solid-state and liquid-junction solar cells and photocatalytic/photoelectrochemical systems designed for the conversion of solar light into the electric current or the accumulation of solar energy in the form of products of various chemical reactions. The review discusses general aspects of the light absorption and photophysical properties of multinary metal chalcogenide NCs, the modern state of the synthetic strategies applied to produce the multinary metal chalcogenide NCs and related nanoheterostructures, and recent achievements in the metal chalcogenide NC-based solar cells and the photocatalytic/photoelectrochemical systems. The review is concluded by an outlook with a critical discussion of the most promising ways and challenging aspects of further progress in the metal chalcogenide NC-based solar photovoltaics and photochemistry.

Effective bandgap narrowing of Cu–In–Zn–S quantum dots for photocatalytic H2 production via cocatalyst-alleviated charge recombination

Effective bandgap narrowing of Cu–In–Zn–S quantum dots is achieved with increased tolerance of Cu from the cocatalyst-alleviated charge recombination.

Two-dimensional bismuth oxybromide coupled with molybdenum disulphide for enhanced dye degradation using low power energy-saving light bulb

In the present work, two-dimensional bismuth oxybromide (BiOBr) was synthesized and coupled with co-catalyst molybdenum disulphide (MoS₂) via a simple hydrothermal process. The photoactivity of the resulting hybrid photocatalyst (MoS₂/BiOBr) was evaluated under the irradiation of 15 W energy-saving light bulb at ambient condition using Reactive Black 5 (RB5) as model dye solution. The photo-degradation of RB5 by BiOBr loaded with 0.2 wt% MoS₂ (MoBi-2) exhibited more than 1.4 and 5.0 folds of enhancement over pristine BiOBr and titanium dioxide (Degussa, P25), respectively. The increased photocatalytic performance was a result of an efficient migration of excited electrons from BiOBr to MoS₂, prolonging the electron-hole pairs recombination rate. A possible charge transfer diagram of this hybrid composite photocatalyst, and the reaction mechanism for the photodegradation of RB5 were proposed.

Highly efficient visible-light photocatalytic activity of MoS2–TiO2 mixtures hybrid photocatalyst and functional properties

2D-layered molybdenum disulfide (MoS₂) and MoS₂/TiO₂ nanocomposite were synthesized by a hydrothermal method.