Controlled synthesis of heterostructured Ag@AgI/ZnS microspheres with enhanced photocatalytic activity and selective separation of methylene blue from mixture dyes

Efficient performance of InP and InP/ZnS quantum dots for photocatalytic degradation of toxic aquatic pollutants

In recent years, the growing concern over the presence of toxic aquatic pollutants has prompted intensive research into effective and environmentally friendly remediation methods. Photocatalysis using semiconductor quantum dots (QDs) has developed as a promising technology for pollutant degradation. Among various QD materials, indium phosphide (InP) and its hybrid with zinc sulfide (ZnS) have gained considerable attention due to their unique optical and photocatalytic properties. Herein, InP and InP/ZnS QDs were employed for the removal of dyes (crystal violet, and congo red), polyaromatic hydrocarbons (pyrene, naphthalene, and phenanthrene), and pesticides (deltamethrin) in the presence of visible light. The degradation efficiencies of crystal violet (CV) and congo red (CR) were 74.54% and 88.12% with InP, and 84.53% and 91.78% with InP/ZnS, respectively, within 50 min of reaction. The InP/ZnS showed efficient performance for the removal of polyaromatic hydrocarbons (PAHs). For example, the removal percentage for naphthalene, phenanthrene, and pyrene was 99.8%, 99.6%, and 88.97% after the photocatalytic reaction. However, the removal percentage of InP/ZnS for pesticide deltamethrin was 90.2% after 90 min light irradiation. Additionally, advanced characterization techniques including UV-visible spectrophotometer (UV-Vis), photoluminescence (PL), X-ray diffractometer (XRD), energy-dispersive spectrometer (EDS) elemental mapping, transmission electron microscopy (TEM), and thermogravimetric analysis (TGA) were used to analyze the crystal structure, morphology, and purity of the fabricated materials in detail. The particle size results obtained from TEM are in the range of 2.28-4.60 nm. Both materials (InP and InP/ZnS) exhibited a spherical morphology, displaying distinct lattice fringes. XRD results of InP depicted lattice planes (111), (220), and (311) in good agreement with cubic geometry. Furthermore, the addition of dopants was discovered to enhance the thermal stability of the fabricated material. In addition, QDs exhibited efficacy in the breakdown of PAHs. The analysis of their fragmentation suggests that the primary mechanism for PAHs degradation is the phthalic acid pathway.

Dynamic properties of photogenerated charge in BiOBr/Bi2WO6/GO ternary composites and its application for organic pollutants degradation

Carbon-based Materials have been extensively researched for their prospect in the fields of environment and energy, especially for graphene oxide (GO). In this work, a novel sodium dodecyl sulfate (SDS)-assisted synthesis of BiOBr/Bi2WO6/GO ternary composite has been synthesized successfully by a handy hydrothermal method. Photoluminescence, Photocurrent, Electrochemical Impedance Spectroscopy, surface photovoltage and transient photovoltage measurements illustrate that construction of p-n BiOBr/Bi2WO6 heterojunction leads to the obviously enhancement of charge separation efficiency, and the photogenerated electrons trapped by GO can effectively inhibit the recombination process of photogenerated charge, resulting in the improvement of charge separation efficiency and the longer lifetime of photogenerated carriers for BiOBr/Bi2WO6/GO. The characterization of structure and morphology indicate that role of GO can also improve the visible light absorption range, and the SDS-assisted synthesis can reduce the size of particle in the composite and enhances the specific surface area of the composite by regulating the particle size and agglomeration. Under optimal conditions, BiOBr/Bi2WO6/GO (SDS) has the outstanding photocatalytic degradation performance and the degradation rate constants for oxytetracycline, tetracycline hydrochloride, methylene blue and rhodamine are 0.056, 0.057, 0.103 and 0.414 min-1, respectively. Notably, the degradation rate constants obtained by BiOBr/Bi2WO6/GO (SDS) are more ten times higher than that of pure BiOBr and Bi2WO6. The possible mechanism of photocatalytic degradation was suggested for BiOBr/Bi2WO6/GO based on the dynamic properties of photogenerated charge and reactive oxidation species results. Surprisingly, the recyclability of the BiOBr/Bi2WO6/GO (SDS) composite obtained from the cyclic experiments has laid a foundation for the study of efficient and stable photocatalysts.

Improving the Performance of ZnS Photocatalyst in Degrading Organic Pollutants by Constructing Composites with Ag2O

ZnS is a promising photocatalyst in water purification, whereas its low photon efficiency and poor visible-light response restrict its application. Constructing composites may help solve these problems. In this work, Ag₂O was introduced to ZnS for the first time based on their energy band characteristics to form a novel ZnS/Ag₂O composite photocatalyst. In the model reaction of degrading methylene blue, the as-designed catalyst exhibited high catalytic activity among a series of ZnS-based composite photocatalysts under similar conditions. The catalytic rate constant was up to 0.138 min⁻¹, which is 27.4- and 15.6-times higher than those of ZnS and Ag₂O. This composite degraded 92.4% methylene blue in 50 min, while the ratios were 31.9% and 68.8% for ZnS and Ag₂O. Catalytic mechanism study based on photoluminescence and radical-scavenging experiments revealed that the enhanced photocatalytic activity was attributed to the composite structure of ZnS/Ag₂O. The structure not only facilitated the separation and transmission of photogenerated carriers but also extended the light response range of the catalyst. The as-designed ZnS/Ag₂O composite is promising in degrading organic pollutants in water.

Comparison of Ag and AgI-Modified ZnO as Heterogeneous Photocatalysts for Simulated Sunlight Driven Photodegradation of Metronidazole

Ag and AgI-modified ZnO composites (Ag/ZnO and AgI/ZnO) were synthesized in facile ways. The photocatalysts were used for the photodegradation of metronidazole (MNZ) under the irradiation of simulated sunlight. The results of experiments showed that both Ag/ZnO and AgI/ZnO had a specific molar ratio to reach the best performance. Ag/ZnO performed better in the photodegradation of MNZ than AgI/ZnO under the same conditions. The reaction rate constant of AgI/ZnO was less affected by the variation of initial concentration of MNZ or pH values. The main reactive oxygen species of the photocatalytic process are OH, O2− and h+, but the free radicals which play the most critical part differ in Ag/ZnO and AgI/ZnO. Several intermediates were revealed by LC–MS/MS analysis. The stability of the photocatalysts was evaluated by a series of repeated MNZ photodegradation experiments. The results showed that AgI/ZnO had better stability than Ag/ZnO.

MoS2 nanosheets anchored on porous ZnSnO3 cubes as an efficient visible-light-driven composite photocatalyst for the degradation of tetracycline and mechanism insight

In this study, MoS₂/ZnSnO₃ (MS-ZSO) composite photocatalyst with loading MS nanosheets onto the surface of porous ZSO microcubes was synthesized using a simple hydrothermal route. The prepared MS-ZSO composite can be easily excited under visible light, and 3 % MS-ZSO exhibits an outstanding photo-degradation (>80 % in 60 min) and mineralization performance (>42 % in 60 min) of the tetracycline. A remarkable improvement in the photocatalytic activity of MS-ZSO composite derived from a positive synergistic effect of well-matched energy level positions, increasement the absorption of visible light, prolonged life time decay and improved interfacial charge transfer between MS and ZSO. In-depth investigation on charge carrier separation mechanism toward MS/ZSO composite under visible light was proposed, which was further evidenced by capture experiments and electron spin resonance (ESR) techniques. Furthermore, the corresponding intermediates of tetracycline degradation over MS-ZSO composites were inspected by liquid chromatography-mass spectrometry (LC-MS) analysis, and the possible degradation paths were proposed.

Fabrication of novel g-C3N4 based MoS2 and Bi2O3 nanorod embedded ternary nanocomposites for superior photocatalytic performance and destruction of bacteria

Highly efficient g-C₃N₄ based MoS₂/Bi₂O₃ nanorod embedded novel (g-C₃N₄/MoS₂/Bi₂O₃) nanocomposites were effectively fabricated by a hydrothermal–calcination method. The schematic depiction is illustrating the plausible mechanism of charge separation and degradation of pollutants under visible-light exposure by a g-C₃N₄/MoS₂/Bi₂O₃ photocatalyst.

Degradation of bisphenol a using peroxymonosulfate activated by WO3@MoS2/Ag hollow nanotubes photocatalyst

WO₃@MoS₂/Ag (HW@MA) hollow tubes were successfully engineered to photodegrade bisphenol A (BPA) combined with peroxymonosulfate (PMS) for the first time. XRD, XPS, TEM and SEM were conducted. The HW@MA tubes present excellent photocatalytic performance on the removal of BPA. The intermediate products of BPA were investigated by GC-MS analysis and the degradation pathway was proposed. To explore the transferred mechanism of photoproduced carriers, the electron paramagnetic resonance (EPR) technique was carried out. The results revealed that the superoxide radical (O₂^-), hydroxyl radical (OH), sulfate radical (SO₄^-) were the main active radicals. Moreover, the formed schottky junctions enhanced the separation efficiency of photoinduced electron-hole pairs. Besides, the effect of the photocatalysts' dosage, PMS concentration, pH of the initial solution and co-existing anions on the BPA degradation were investigated.

One-Step Synthesis of Ag@TiO₂ Nanoparticles for Enhanced Photocatalytic Performance

Polyamide network polymers (PNP) modified TiO₂ nanoparticles (NPs) were decorated with Ag NPs in hydrothermal gel method, forming one-step synthesized photocatalysts, Ag@TiO₂ NPs. The effect of PNP and the amount of Ag NPs added were investigated in this work. PNP acted as a nanocage to prevent TiO₂ aggregation and capture Ag accurately, which could effectively control product sizes and improve dispersibility in solvents. Simultaneously, TiO₂ NPs modified with Ag NPs exhibited remarkable photocatalytic effects. One-step synthesis simplified the experimental process and avoided the agglomeration of silver ions during the secondary reaction, achieving the purpose of uniform distribution at a specific location of TiO₂ NPs. The prepared Ag@TiO₂ NPs-0.5 could remove 79.49% of Methyl Orange (MO) after 3 h of ultraviolet light irradiation, which was 2.7 times higher than the reaction rate of pure TiO₂ NPs. It also exhibited good photoactivity under Visible light conditions. Moreover, the mineralization rate of MO over the Ag@TiO2 NPs-0.5 could be up to 72.32% under UV light and 47.08% under Visible light irradiation, which revealed that the prepared catalysts could effectively degrade most of the MO to CO₂ and H₂O. The samples also demonstrated the excellent stability and easy recyclability with over 90% of the original catalytic level for MO degradation. The photocatalysts studied also exerted broad application prospects such as photovoltaic hydrogen production, electronic sensors and biomedicine.

Photophysical and Photocatalytic Properties of BiSnSbO₆ under Visible Light Irradiation

BiSnSbO₆ with strong photocatalytic activity was first fabricated by a high-temperature, solid-state sintering method. The resulting BiSnSbO₆ was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), UV-vis diffuse reflectance spectroscopy (DRS) and X-ray photoelectron spectroscopy (XPS). The results showed that BiSnSbO₆, with a pyrochlore structure and a cubic crystal system by a space group Fd3m, was well crystallized. The lattice parameter or the band gap of BiSnSbO₆ was 10.234594 Å or 2.83 eV. Compared with N-doped TiO₂, BiSnSbO₆ showed higher photocatalytic activity in the degradation of benzotriazole and rhodamine B. The apparent first-order rate constant for BiSnSbO₆ in the degradation of benzotriazole and rhodamine B was 0.0182 min^-1 and 0.0147 min^-1, respectively. On the basis of the scavenger experiment, during the photocatalytic process, the main active species were arranged in order of increasing photodegradation rate: •OH < •O₂^- < h⁺. The removal rate of benzotriazole or rhodamine B was approximately estimated to be 100% with BiSnSbO₆ as a photocatalyst after 200 min visible-light irradiation. Plentiful CO₂ produced by the experiment indicated that benzotriazole or rhodamine B was continuously mineralized during the photocatalytic process. Finally, the possible photodegradation pathways of benzotriazole and rhodamine B were deduced.

Structure-Dependent Photocatalytic Performance of BiOBrxI1−x Nanoplate Solid Solutions

BiOXxY1−x (X, Y = Cl, Br, and I) solid solutions have been regarded as promising photocatalysts attributed to their unique layered structure, tunable band structure, and chemical and optical stability. In this study, BiOBrxI1−x nanoplate solid solutions with a high exposure of {001} crystal facets were prepared by a facile alcoholysis method at room temperature and atmospheric pressure. X-ray diffraction (XRD) peaks exhibited a slight shift to lower diffraction angle with the increase of I content in BiOBrxI1−x samples, which resulted in a gradual increase in their cell parameters. Field emission scanning electron microscopy (FESEM) and transmission electron microscope (TEM) images revealed that BiOBrxI1−x samples exhibited 2D plate-like structure with the in-plane wrinkles. The regular changes in optical absorption threshold and Eg value seen in UV-vis diffuse reflectance spectra (UV-vis DRS) indicated that the optical absorption property and band structure could be modulated by the formation of BiOBrxI1−x solid solutions. The photocatalytic degradation of active dye Rhodamine B (RhB) over BiOBrxI1−x solid solutions showed that BiOBr0.75I0.25 had the best photocatalytic activity. The RhB photodegradation processes followed a pseudo-first-order kinetic model. The synergistic effect of structural factors (including amount of exposed {001} facets, interlayer spacing of (001) plane, and energy-level position of the valence band) determined the photocatalytic performance of BiOBrxI1−x solid solutions.

Fe3O4–Ag2WO4: facile synthesis, characterization and visible light assisted photocatalytic activity

Photo-generated charge carriers are effectively separated on a magnetic nano-composite (Fe₃O₄–Ag₂WO₄) surface under visible light irradiation.