Microwave Hydrothermal Method Research Articles

Visible-light driven photocatalyzing degradation of antibiotics and dyes enabled by 0D/1D Tb2O3/Er2O3/TiO2@C hybrids

It remains a huge challenge to design a kind of high performance, multifunctional and low cost photocatalysts driven by visible light for the remediation of pollutants from waste water. In this work, the carbon coated Tb2O3/Er2O3/TiO2 nanotubes (Tb2O3/Er2O3/TiO2@C) 0D/1D hybrid photocatalysts were synthesized by a microwave hydrothermal method. Essentially, the Er2O3 nanoparticles can absorb low-energy photons at 800–980 nm and emit high-energy photons to TiO2 through the up-conversion effect, meanwhile, the Tb2O3 act as a redox center to promote the separation of photoinduction charges since the instantaneous photoelectric density was increased by 10 times by compared to TiO2@C. As a result, the photodegradation efficiency of the optimized Tb2O3/Er2O3/TiO2@C photocatalysts is about 15.7 times higher than that of TiO2@C under visible light irradiation for decomposing rhodamine B, respectively. Moreover, the photodegradation efficiency remained above 70 % after reused for 5 times. Thus, the enhanced synergistic effect between Er2O3 and Tb2O3 promises the excellent photodegradation activity and reduce cost.It remains a huge challenge to design a kind of high performance, multifunctional and low cost photocatalysts driven by visible light for the remediation of pollutants from waste water. The carbon coated Tb2O3/Er2O3/TiO2 nanotubes (Tb2O3/Er2O3/TiO2@C) 0D/1D hybrids were synthesized by a microwave hydrothermal method. The Er2O3 nanoparticles can absorb low-energy photons at 800–980 nm and emit high-energy photons to TiO2 through the up-conversion effect, meanwhile, the Tb2O3 act as a redox center to promote the separation of photoinduction charges since the instantaneous photoelectric density was increased by 10 times by compared to TiO2@C. As a result, the photodegradation efficiency of the optimized Tb2O3/Er2O3/TiO2@C photocatalysts is about 15.7 times higher than that of TiO2@C under visible light irradiation for decomposing rhodamine B. Moreover, the photodegradation efficiency remained above 70 % after reused for 5 times. Thus, the enhanced synergistic effect between Er2O3 and Tb2O3 promises the excellent photodegradation activity and reduce cost.

Microwave-hydrothermal synthesis of calcium borate whiskers: Influencing factors and formation mechanism

The synthesis of whiskers is an important means of high-value utilization of calcium resources. Calcium borate (Ca2B2O5·H2O) whiskers were synthesized by microwave hydrothermal method using CaCl2, Na2B4O7·10H2O and NaOH as raw materials at 140 °C for 2 h. A series of characterizations were conducted on the obtained calcium borate whiskers, including phase identification (XRD and FT-IR), crystal morphology (SEM), crystal structure (TEM and SAED), and thermal stability (TG). Through batch experiments under the control of influencing factors, the effects on product phase and morphology were systematically studied, such as raw material concentration (Ca2+ concentration and the molar ratio of boron/calcium), reaction temperature, holding time and pH value. For the prepared calcium borate whiskers, SAED demonstrated that the whiskers have a single crystal structure, characterized by a sarciniform shape with diameter ranging from 1.2 to 3.1 μm and a length of 50 to 120 μm. And thermal analysis revealed that the calcium borate whiskers remained stable without losing crystalline water at a synthesis temperature of 140 °C, while releasing crystalline water at a temperature range of 383.6 °C to 430.9 °C. The optimal conditions for Microwave-Hydrothermal synthesis were identified based on experimental phenomena, and the solution-liquid–solid (SLS) process of whisker formation was proposed and analyzed. The possible chemical reactions and growth mechanisms of calcium borate whiskers under microwave hydrothermal synthesis were briefly proposed by adjusting the reaction conditions and observing the process of morphological changes.

Effect of CdS on microstructure and performance of ZnO composite photocatalyst

AbstractIn this study, Nd‒Dy‒ZnO and CdS‒Nd‒Dy‒ZnO photocatalysts were prepared by microwave hydrothermal method to improve the photocatalytic performance of ZnO. The microstructure and performance of samples were characterized by X‐ray diffraction, scanning electron microscopy, ultraviolet (UV)‒visible, and X‐ray photoelectron spectroscopy, and evaluated with the methylene blue. The results showed that CdS attached to the ZnO crystal surface in the form of flocculent particles, and the combination with CdS promoted the growth of ZnO crystals, while an excess of CdS was found to be detrimental to the crystallization of ZnO. When nCdS/nZnO = 0.30 mol%, composite materials achieved the optimal photocatalytic performance, which made the degradation rate of methylene blue reach 93.42% under UV irradiation for 4 h. CdS‒Nd‒Dy‒ZnO composite photocatalytic material can generate active oxygen groups such as hydroxyl and superoxide radicals simultaneously, which greatly enhances the photocatalytic efficiency of the composite material.

A competitive strategy toward 1 T/2H MoS2 to balance impedance for optimizing electromagnetic wave absorption

Interface engineering and phase engineering play crucial roles in enhancing the design and development of advanced electromagnetic wave (EMW) absorbers. However, there is a lack of focus on designing phase structures and interfaces from a microscopic perspective to adjust impedance matching and EMW absorption. This study introduced a competitive strategy involving 1 T/2H MoS2. The phase structure and composition of MoS2 were controlled using a microwave hydrothermal method. By creating a diverse phase interface within the material in the form of 1 T/2H, a balance between conduction loss and polarization loss was achieved, leading to improved EMW absorption through enhanced impedance matching. The results indicated that the incorporation of the 1 T phase boosted the electron transfer capability of MoS2, increasing conduction loss. The 1 T/2H phase interface enhanced interface polarization, thereby amplifying polarization loss. At a thickness of 2.8 mm, the absorber demonstrated a minimum reflection loss of −64.9 dB and an effective absorption bandwidth of 4.6 GHz. In far-field conditions, the maximum radar cross-section (RCS) of the 1 T/2H phase MoS2 nanoflowers was −27.5 dBm2. This study elucidates the relationship between 1 T/2H phase MoS2 content and phase interfaces with impedance matching, offering a novel approach for developing high-performance MoS2-based EMW absorbing materials.

Preparation of Pt(II/IV)Clx/BiOHC2O4/Bi2O2CO3 composite microrods with enhanced photocatalytic performance for levofloxacin degradation in water

BiOHC2O4 microrods were initially prepared via a straightforward microwave hydrothermal method. These microrods then served as templates for the growth of BiOHC2O4/Bi2O2CO3 composites via anion exchange. Pt loading onto the composite microrods was achieved through photodeposition and chemical reduction methods. The obtained samples were analyzed by XRD, SEM, TEM, XPS, FT-FIR, UV–Vis DRS, PL, N2 physical adsorption, photocurrent and Nyquist impedance measurements. The photocatalytic performance of the fabricated materials for levofloxacin degradation was evaluated under both UV–visible and visible light irradiation. The results showed the formation of Pt(II/IV)Clx species on hierarchical BiOHC2O4/Bi2O2CO3 structure following photodeposition, while metallic Pt was produced via NaBH4 reduction. Pt(II/IV)Clx/BiOHC2O4/Bi2O2CO3 composites displayed superior photocatalytic performance under both light conditions. This enhanced performance can be linked to the presence of Pt(II/IV)Clx, which significantly improves light absorption and facilitates the transfer of photoelectrons and holes (e− and h+). Pt(II/IV)Clx served as a dual-functioning agent, acting as both a photosensitizer to enable visible light activity and as an inhibitor suppressing the recombination of photogenerated carriers. Loading around 4%Pt(wt%), BiOHC/BiOC demonstrated the highest rates of TOC removal, under full light spectrum irradiation for 75 min and visible light irradiation for 300 min, respectively.

Lattice variation as a function of concentration and grain size in MgO–NiO solid solution system

The study aimed to understand how changes in crystal's size affect the lattice parameters and crystal structure of Mg1-xNixO solid solution for six X values ranging from x = 0 to x = 1. Mg1-xNixO was synthesized via two different wet-chemical techniques: the sol-gel and the microwave hydrothermal method, both followed by calcination at different temperatures of 673, 873, 1073, 1273 and 1473 K. As annealing caused grain growth, the varied temperature range allowed to examine a wide range of grain sizes. The lattice parameters and x values were determined from XRD (X-ray diffraction) peak positions and intensities respectively. The grain size was evaluated by XRD line profile analysis and supported by SEM (scanning electron microscope) observations. At the temperatures of 673 and 873 K grain size was in the nanometric range and from 1073 K and above grain size was in the micrometric range. A non-monotonic lattice variation versus grain size was found for each concentration. When grain size decreased there was a slight contraction, however for grain size in the nanometric range there was a severe lattice expansion. Both lattice parameter changes were explained by two effects acting together: contraction due to surface stress and expansion due to weakening of the ionic bonding at nanocrystalline particles. In this current research study, the lattice parameter was mapped in two dimensions: concentration and grain size. The findings of this study provided valuable insights into the lattice variation in the MgO–NiO solid solution system.

Plant-Mediated Synthesis of Magnetite Nanoparticles with Matricaria chamomilla Aqueous Extract.

Magnetite nanoparticles (NPs) possess properties that make them suitable for a wide range of applications. In recent years, interest in the synthesis of magnetite NPs and their surface functionalization has increased significantly, especially regarding their application in biomedicine such as for controlled and targeted drug delivery. There are several conventional methods for preparing magnetite NPs, all of which mostly utilize Fe(iii) and Fe(ii) salt precursors. In this study, we present a microwave hydrothermal synthesis for the precipitation of magnetite NPs at temperatures of 200 °C for 20 min and 260 °C for 5 min, with only iron(iii) as a precursor utilizing chamomile flower extract as a stabilizing, capping, and reducing agent. Products were characterized using FTIR, PXRD, SEM, and magnetometry. Our analysis revealed significant differences in the properties of magnetite NPs prepared with this approach, and the conventional two-precursor hydrothermal microwave method (sample MagH). FTIR and PXRD analyses confirmed coated magnetite particles. The temperature and magnetic-field dependence of magnetization indicate their superparamagnetic behavior. Importantly, the results of our study show the noticeable cytotoxicity of coated magnetite NPs-toxic to carcinoma cells but harmless to healthy cells-further emphasizing the potential of these NPs for biomedical applications.

Co-Fe synergistic interaction mediated novel peroxymonosulfate activators: High-efficiently degradation and outstanding mineralization

The search for immobilization methods is the key to current research on environmentally friendly catalysts. In this study, Fe-Co bimetallic organic framework material was prepared by microwave hydrothermal method. After further carbonization, structural frame self-fixing catalyst Fe/CoC was obtained for the activation of peroxymonosulfate (PMS). Based on a stable three-dimensional structure, high specific surface area, variable polymetallic ion valence and remarkable catalytic performance, Fe/CoC achieved 99.59 % treatment efficiency and 93.38 % mineralization efficiency of norfloxacin (NOR) within 30 min. The universality was evaluated in multiple antibiotics and actual water configuration solutions. The matching redox potentials and synergistic interactions between the bimetals enhanced the activation catalytic efficiency, which was attributed to the generation of radical SO4•− and non-radical 1O2. In addition, the voltammetry characteristic curve proved the existence of direct electron transfer in the system. Finally, a relatively complete NOR degradation pathways were proposed based on the 13 intermediates. This work has enriched the development of stable catalysts for PMS activation and provided a new idea for MOFs to participate in antibiotic removal.

When 2D g-C3N4 meets 0D CNQDs and 1D CNTs: A strategy for photocatalytic hydrogen production over a ternary non-metallic catalyst

Utilizing solar energy to facilitate photocatalytic hydrogen production holds great promise in addressing the energy crisis. One material that shows tremendous potential in this field is two-dimensional graphitic carbon nitride (2D g-C3N4). However, the fast recombination rate of photogenerated carriers and the limited specific surface area impede its photocatalytic activity. This research endeavors to address these limitations by developing a ternary composite photocatalyst, CNQDs/g-C3N4/CNTs, by employing the microwave hydrothermal method. g-C3N4 was co-modified with zero-dimensional g-C3N4 quantum dots (0D CNQDs) and one-dimensional carbon nanotubes (1D CNTs). Incorporating CNQDs and the g-C3N4 interface facilitates the separation of photogenerated carriers, while the tubular channel of CNTs provides favorable conditions for transferring photogenerated electrons. Additionally, the introduction of CNQDs and CNTs significantly increases the specific surface area of the sample, thereby enhancing the number of reaction active sites available for the photocatalytic production of hydrogen. The hydrogen generation rate of the CNQDs/g-C3N4/CNTs is 1109.388 μmol⋅g−1⋅h−1, surpassing that of the single g-C3N4 specimen by 3.62 times. The application of density functional theory (DFT) calculations reinforces the enhanced performance of the composite through the synergistic effect of CNQDs and CNTs. This effect optimizes the adsorption behavior of the active intermediate (H*) and reduces the Gibbs free energy ΔG(H*) associated with the photocatalytic hydrogen evolution reaction.

Constructing Heterointerfaces in Dual-Phase High-Entropy Oxides to Boost O2 Activation and SO2 Resistance for Mercury Removal in Flue Gas.

The low O2 activation ability at low temperatures and SO2 poisoning are challenges for metal oxide catalysts in the application of Hg0 removal in flue gas. A novel high-entropy fluorite oxide (MgAlMnCo)CeO2 (Co-HEO) with the second phase of spinel is synthesized by the microwave hydrothermal method for the first time. A high efficiency of Hg0 removal (close to 100%) is achieved by Co-HEO catalytic oxidation at temperatures as low as 100 °C and in the atmosphere of 145 μg m-3 Hg0 at a high GHSV (gas hourly space velocity) of 95,000 h-1. According to O2-TPD and in situ FT-IR, this extremely superior catalytic oxidation performance at low temperatures originates from the activation ability of Co-HEO to transform O2 into superoxide and peroxide, which is promoted by point defects induced from the spinel/fluorite heterointerfaces. Meanwhile, SO2 resistance of Co-HEO for Hg0 removal is also improved up to 2000 ppm due to the high-entropy-stabilized structure, construction of heterointerfaces, and synergistic effect of the multicomponents for inhibiting the oxidation of SO2 to surface sulfate. The design strategy of the dual-phase high-entropy material launches a new route for metal oxides in the application of catalytic oxidation and SO2 resistance.

Highly Effective Fe-Doped Nano Titanium Oxide for Removal of Acetamiprid and Atrazine under Simulated Sunlight Irradiation

Pesticides are widely detected in large quantities in the environment, posing an ecological threat to the human body and ecology. Semiconductor nanomaterials such as nano-titania (nTiO2) have strong photocatalytic degradation efficiency for pollutants. However, the wide bandgap and limited light absorption range inhibit nano-titania’s practical application. Therefore, nTiO2 was modified by Fe3+ doping using the microwave hydrothermal method to improve its photocatalytic performance in this study. Fe-nTiO2 doped with a 1.0% mass ratio was used due to its high photocatalytic performance. Its maximum degradation efficiencies for ACE and ATZ under a 20 W xenon lamp were 88% and 88.5%, respectively. It was found that Fe3+ doping modification distorted the spatial morphology of nTiO2 and shortened the bandgap to facilitate the photocatalytic reaction. The electron paramagnetic resonance results showed that the reactive radicals (1O2, ·OH) produced by photogenerated electrons (e−) and holes (h+) of Fe-nTiO2 were the main active species in the degradation of ACE and ATZ. Additionally, the application of Fe-nTiO2 significantly enhanced the growth of lettuce under sunlight; the degradation efficiencies of ACE and ATZ in lettuce were 98.5% and 100%, respectively. This work provides new insights into the removal of organic contaminants by photocatalysts under sunlight in agriculture.

Microwave-assisted hydrothermal synthesis of ZnO@ZrO2 nanohybrid for biomedical and photocatalytic applications

The present study was conducted to synthesize zinc oxide decorated on zirconium oxide (ZnO@ZrO2) nanohybrid synthesized through microwave-hydrothermal (MW-HT) method. Various analytical techniques were used to analyze the morphology, surface properties, constitution of hybrid, and elemental composition. Additionally, the anti-microbial activity of ZnO@ZrO2 nanohybrid was assessed against Gram-positive and Gram-negative pathogenic bacteria, hemolytic, anti-oxidant as well as anti-inflammatory assay. The hexagonal wurtzite phase of the ZnO was revealed by the XRD analysis. The experimental results reveal that the synergetic effect between the Zn and Zr active sites results an excellent biomedical activity. The ZnO@ZrO2 nanohybrid was successfully applied to the photocatalytic degradation of basic fuchsin (BF) dye within short period of time under visible light (VL) radiation. Moreover, the ZnO@ZrO2 nanohybrid exhibited an extraordinary performance for photocatalytic degradation of BF with a pseudo-first order rate constant (k) of ca. 0.1702 min−1, which was 2.5 and 1.8 fold compared to ZnO and ZrO2 photocatalysts. These results indicated that the ZnO@ZrO2 nanohybrid can be used as a potential biomaterial for bioengineering and photocatalytic applications.

Enhancing Dy2O3/g-C3N4 visible photocatalytic hydrogen production performance by loading graphene-like carbon from Enteromorpha prolifera (EP-GL)

Using Enteromorpha prolifera (EP) as a raw material, biomass graphene-like carbon (EP-GL) can be prepared and used as a cocatalyst to modify semiconductor photocatalytic materials, which contributes to achieving a sustainable development strategy. In this study, graphene-like carbon was successfully obtained from EP biomass through high-temperature pyrolysis. It was then used to modify a Dy2O3/g-C3N4 semiconductor composite photocatalyst using a simple microwave hydrothermal method. The incorporation of EP-GL not only acted as a transfer channel for photogenerated electrons and enhanced the separation of photogenerated carriers, but also significantly increased the specific surface area of the catalyst, providing more active sites for photocatalytic reactions. Additionally, the heterojunction formed between Dy2O3/g-C3N4 aided in the separation of electron-hole pairs, further improving the efficiency of photocatalytic hydrogen production. The composite catalyst achieved a hydrogen generation rate of 683.16 μmol⋅g−1⋅h−1 in ethylene glycol solution and 723.57 μmol⋅g−1⋅h−1 in glucose solution. These rates were 3.84 and 3.56 times greater than those of Dy2O3 alone, respectively. This demonstrated the superior performance of the ternary composite photocatalyst in harnessing visible light for efficient hydrogen production.

Effect of temperature and time on the synthesis of calcium phosphate obtained by microwave hydrothermal method

Bioceramics are materials used in biomedical devices for bone replacement, and calcium phosphate derivatives are widely used in cases of bone defect repair. The aim was to evaluate the influence of temperature and time on the synthesis of calcium phosphate obtained by the microwave hydrothermal method on its structural and morphological characteristics with a view to application as a bone graft. The calcium phosphate powders (calcium octophosphate, hydroxyapatite and calcium triphosphate) were produced using the microwave hydrothermal method. To obtain the calcium phosphate powders, aqueous solutions of Ca (OH)2 and H3 PO4 were used and subjected to the microwave hydrothermal method at temperatures of 110°C and 130°C for 30 and 60 minutes, then calcined at 700°C for 1 hour and characterized using XRD, FTIR, SEM, particle size distribution, apparent density, and apparent porosity. The results obtained by the techniques confirm crystalline and morphological modifications, and homogeneous distribution of the particles, and the phases of interest, octophosphate, hydroxyapatite and calcium β-triphosphate, were identified. The formation of the β-TCP phase was predominant in the samples in which the microwave hydrothermal synthesis was carried out over a longer time and at a higher temperature. It was found that the proposed synthesis method was effective in terms of time/temperature, offering advantages over conventional techniques, such as improving the primary characteristics for choosing a biomaterial to be used in cases of bone regeneration.

Catalytic Acetone Oxidation over MnOx Catalysts: Regulating Their Crystal Structures and Surface Properties

This study investigates the catalytic oxidation of acetone by different crystal phases of MnO2 prepared via different methods. Compared with β-MnO2 and γ-MnO2, α-MnO2 exhibited superior catalytic activity. Moreover, as replacements for traditional hydrothermal methods and air calcination, the use of microwave hydrothermal methods and N2 calcination significantly enhanced the catalytic performance of the MnO2 catalyst. The optimal catalyst, MnO2-WN (α-MnO2 synthesized via microwave hydrothermal method and N2 calcination), converted 100% of 100 ppm acetone below 150 °C, with the CO2 yields reaching 100%. Further, the stability of the catalyst and its potential for other volatile organic compounds (VOCs) were also determined. The experimental data demonstrated that its outstanding activity primarily stemmed from the improved preparation method, enhancing the specific surface area of the catalyst, optimizing the pore structure, improving the redox performance, and generating more acidic sites and active oxygen species, thereby creating a synergistic effect. Finally, the reaction pathway of acetone oxidation on the catalyst surface has been explored. This work provides a new perspective for developing economically efficient MnOx catalysts for removing VOCs.

Hierarchical Mo-doped Ni[sbnd]Co hydroxides cauliflower-like microspheres via a rapid microwave hydrothermal synthesis for supercapacitors

Transition metal double hydroxide (TMDH) materials have the advantages of low cost, simple preparation, wide variety, and tunable physical and chemical properties, which have broad research prospects in developing and applying high-performance electrode materials. Herein, molybdenum-doped nickel-cobalt double hydroxides (NiCoDH-Mo) were prepared by a rapid one-step microwave hydrothermal method in tens of minutes. Extensive investigations have been conducted on the morphology, crystal structure, and electrochemical properties of nickel‑cobalt double hydroxides with varying concentrations of Mo doping. The incorporation of Mo dopants into NiCoDH-Mo0.50 has yielded the formation of hierarchical cauliflower-like microspheres, which exhibit a significantly enhanced specific surface area of 91.7 m2 g−1 along with an improved electrical conductivity of 0.0233 μS cm−1. Thus, the optimized NiCoDH-Mo0.50 electrode has a high specific capacity of 160.5 mAh g−1 at a current density of 1 A g−1 and can maintain a high specific capacity of 115.3 mAh g−1 when the current density increases by 20 times. Finally, the NiCoDH-Mo cathode and mango seed-derived activated carbon anode were assembled into a hybrid supercapacitor with an energy density of 41.3 Wh kg−1 at a power density of 850 W kg−1, which also exhibits a capacity retention of 84 % after 8000 cycles. Therefore, we provide a facile and efficient strategy to prepare TMDH electrode materials with excellent performance for energy storage systems.

Microwave Hydrothermal Preparation of VO2

As a thermal phase transition material, VO2 is famous for its phase transition performance. When the temperature is lower than the phase transition temperature, VO2 behaves as a semiconductor with high infrared transmittance. When the temperature exceeds the phase transition temperature, VO2 exhibits a metallic state and has a high refractive index for infrared. Regulation of phase transition temperature is key to the application of VO2. In this article, microwave hydrothermal is used to prepare VO2. H+ concentration, microwave power, annealing temperature, and annealing time are used as variable conditions to find the best preparation conditions. The preparation of samples is studied by X‐ray diffractometer, scanning electron microscope, and differential scanning calorimeter. After comparative research, the optimum preparation process of vanadium dioxide by microwave hydrothermal method is found. In addition, by varying the acidic conditions and microwave power during the preparation process, the phase transition temperature of VO2 can be regulated.

Investigating intrinsic and extrinsic defects in an inorganic hybrid system (BaTiO3–CaF2) via vacuum ultraviolet-excited low-temperature luminescence

Investigations into the luminescence of undoped and Eu-doped BaTiO3@CaF2 hybrid compound, as well as its individual components, were performed at both room and low temperatures, and the findings were discussed in the context of intrinsic and extrinsic defects present in both matrices. The synthesis process employed an eco-friendly method, capable of producing crystalline phases in just 1 min of plateau time at temperatures as low as 140 °C. The microwave-hydrothermal method can provide free oxygen ions at the surface, allowing them to interact with the ions from the precursor solution of CaF2. For Eu-doped samples, while the isolated CaF2 showed the characteristic 4f65d1-4f7 Eu2+ transition, BaTiO3@CaF2 hybrid compound showed the association of two defects, resulting in emissions related to defects from oxygen ions as well as Eu2+. The evidence of intrinsic defects was confirmed by comparing the samples measured at 60 K, where the influence of lattice vibrations was reduced, leading to a decrease in non-radiative processes. Another difference observed was the presence of the 4f-4f transitions associated with the presence of Eu3+ in this sample. Discussions were further supported by X-ray Absorption Spectroscopy (XAS) results, performed at the Ti K-edge and Eu L3-edge. EXAFS parameters were estimated based on the incorporation of Eu into the CaF2 structure and replacing Ca sites. For the BaTiO3@CaF2:Eu system, both EuBa and EuTi had to be included in the fitting process, indicating that some of the Eu dopant is either in the lattice of CaF2 or in BaTiO3.

Facile synthesis of oxygen-deficient BiOBrxCl1−x solid solutions for efficient photocatalytic degradation of organic pollutants

In this study, a series of oxygen-deficient BiOBrxCl1−x (x = 0, 0.1, 0.3, 0.5, 0.7, 0.9, 1) solid solution photocatalysts by the microwave hydrothermal method. By changing the Br/Cl molar ratio, the light absorption edge of BiOBrxCl1−x was effectively red-shifted from 345 to 430 nm. The performance of BiOBr0.3Cl0.7 solid solution catalyst showed the best photocatalytic duty for the degradation of norfloxacin (NOR) and methyl orange (MO). The degradation rate of NOR reached 90.2% within 50 min (catalyst dosage: 20 mg), whereas that of MO reached 82.7% within 30 min (catalyst dosage: 5 mg). Environmental factors affecting the degradation of NOR by BiOBr0.3Cl0.7 (such as pH, type of inorganic anions, amount of catalyst, and concentration of NOR) were discussed in detail. The presence of oxygen vacancies (OVs) was confirmed by electron spin resonance (ESR) experiments. Furthermore, free radical capture and ESR experiments identified the main active free radicals involved in the degradation of NOR over BiOBr0.3Cl0.7. Finally, a possible photocatalytic degradation mechanism was proposed.

Microwave-hydrothermal synthesis of F and Fe co-doped CeO2 photocatalysts for efficient removal of 2,4,6-TCP under visible light

In recent years, the massive use and migration of chlorine-containing organics into the environment potentially threaten the natural environment and human health. Advanced oxidation technology based on photocatalysts is a promising approach for the degradation of chlorine-containing organic pollutants, but the development of stable and efficient photocatalysts remains a challenge. In this study, a new visible light-responsive photocatalyst based on F and Fe co-doped CeO2 (FeFC) was synthesized by making full use of overall heating characteristic of microwaves. XRD, SEM-EDS, XPS, BET and DRS results showed that F and Fe was successfully co-doped into CeO2 with increased BET surface and narrowed band gap. The degradation experiments showed that the co-doping of F and Fe significantly enhanced the photocatalytic activity of CeO2 by enhancing visible light absorption and charge carriers separation. Moreover, CeO2 material with both F and Fe doping of 10 % (FeFC-10) showed the highest removal (99.8%) and de-chlorination (89%) rates of 2,4,6-TCP within 4h, which was 3.8 and 3.2 times higher than that of pure CeO2 prepared by microwave and muffle furnace, respectively. Free radical scavenging experiments and electron paramagnetic resonance (EPR) tests finally demonstrated that the h+ and ·OH were the active species that played a catalytic redox role in this reaction system. Furthermore, the degradation intermediates of 2,4,6-TCP were identified by LC-MS and the possible reaction pathways were suggested. In this paper, the photocatalyst (FeFC-10) synthesized by microwave-hydrothermal method could not only save time and energy, but also efficiently degrade 2,4,6-TCP, which could provide the theory and practice for protecting water environment contaminated by chlorine-containing organics through the synthesis of CeO2 based photocatalysts.