Conventional Hydrothermal Method Research Articles

Controllable Synthesis and Ultrahigh Proton Conduction of a Hydrogen-Bond Network.

The functionalization of polyoxometalates with organic ligands provides a new-style strategy to accurately incorporate polyoxometalates with advanced functional organic moieties on their surfaces, the development of which has attracted increasing research interest due to the potential applications. A germanium tungstate Na2(H3O)6[{RuIV(bpy)}2{WO2(C2O4)}2(GeW11O39)2]·27H2O (bpy = 2,2'-bipyridine) with two ligands covalently modified was triumphantly synthesized, using the conventional one-pot hydrothermal method. It was systematically characterized by thermogravimetric analysis (TGA), elemental analysis, infrared (IR) spectroscopy, single-crystal X-ray diffraction, X-ray photoelectron spectroscopy (XPS), powder diffraction (PXRD), scanning electronic microscopy (SEM), and ultraviolet-visible (UV-vis) spectroscopy. The two-dimensional (2D) layered structure was established through hydrogen bonding and Na+ bridges. Impedance measurements indicate that it displays outstanding proton conduction properties, with a splendid conductivity up to 1.24 × 10-2 S·cm-1 under 353 K and 90% relative humidity (RH), owing to the rich interlayer hydrogen-bond network formed by the organic ligands ({RuC10H8N2}4+ and {WC2O4}4+), hydrated protons (H3O+), and crystal waters.

Microwave-assisted hydrothermal synthesis of highly dispersed cerium–zirconium solid solution on Ti3C2Tx nanosheets as an efficient decontamination towards sulfur mustard simulants

The microwave-assisted hydrothermal method has facilitated the straightforward and efficient production of nanoscale CexZr1-xO2/Ti3C2Tx composites. This technique has greatly shortened the synthesis time several hours required by conventional hydrothermal method to merely 10minutes. Due to the unique mechanism of microwave-hydrothermal synthesis, composites with excellent crystallinity, uniform particle size, and superior degradation capabilities can be obtained without calcination. Our investigation systematically explores the influence of various factors including mineralizer concentration, dispersant types, synthesis duration, cerium-to-zirconium ratio, as well as MXene content on the material properties. Optimal degradation of 2-chloroethyl ethyl sulfide, sulfur mustard simulants, is achieved using PEG1000 as the dispersant, a cerium-to-zirconium ratio of 1:2, along with 15mL of MXene, resulting in a remarkably short half-life of only 6.5min. Furthermore, it is confirmed that the incorporation of cerium atoms into ZrO2 lattice, forming a solid solution that is deposited onto the interlayer and surface of Ti3C2Tx nanosheets, with the composite particles measuring approximately 5.01nm. The reduced size and increased specific surface area, coupled with the synergistic effects of oxygen vacancies and acid-base sites, ultimately contribute to the hydrolysis and elimination reactions occurring on 2-CEES. This research offers fresh perspectives on the development of novel materials for the degradation of chemical warfare agents.

NiP/Fe3P/MoP@NF nanoblocks as a bifunctional electrocatalyst for water splitting in alkaline seawater and urea solution

Compared with conventional electrolytic fresh water for hydrogen generation, electrolytic seawater for hydrogen production is more cost-effective, because seawater resources are rich, and fresh water resources are short. However, there are many impurity ions in seawater, especially chloride ions, which have great corrosion on the catalyst, so it is a major factor restricting the development of electrolytic seawater. In this study, a novel NiP/Fe3P/MoP@NF catalyst was made via conventional hydrothermal and phosphating method. Experimental results show that the overpotential of NiP/Fe3P/MoP@NF catalyst in the current density of 10 mA cm−2 is just 40 mV for hydrogen evolution reaction (HER) and the overpotential of NiP/Fe3P/MoP@NF catalyst in the same condition is 135 mV for oxygen evolution reaction (OER) in 1 M KOH and seawater solution. In electrolyte solution of 0.5 M urea and 1 M KOH, the overpotential of NiP/Fe3P/MoP@NF catalyst in the same current density of 10 mA cm−2 is 51 mV for HER. Furthermore, the whole alkaline seawater splitting requires an applied voltage of 1.66 V at current density of 10 mA cm−2. Experimental results show that the increased catalytic activity is assigned to the rapid electron transport rate, the exposure of more activity sites, and their synergistic catalysis. The density functional theory (DFT) can show that MoP has the best Gibbs free energy for hydrogen and electrical conductivity compared with NiP and Fe3P, thus enhancing the catalytic performance of NiP/Fe3P/MoP@NF. The paper proposes novel ideas concerning the exploration of catalysts in alkaline seawater and urea solution.

Green synthesis of Cu-based metal organic framework for electrochemical CO2 conversion into formic acid

Metal-organic frameworks (MOFs) show promising amendments for the remediation of CO2. As the literature reports considerable progress in the electrochemical reduction of CO2, this work focuses on facile green synthesis of metal-organic framework and yields formic acid. The green synthesis MOF involved the use of an aqueous water-based solvent for synthesis, then compared with the conventional hydrothermal method of synthesis using N, N-Dimethylformamide (DMF), and was studied for electrochemical reduction of CO2. Green synthesis of copper benzene tricarboxylic acid (Cu BTC) and conventional synthesis of Cu BTC were characterized by XRD (X-ray diffraction), SEM (Scanning electron microscopy), TEM (Transition electron microscopy), FT-IR (Fourier transform infrared), and XPS (X-ray photoelectron spectroscopy). The performance of the green synthesis of Cu BTC resulted in the achievement of the highest FE (Faradic efficiency) of formic acid of 88 %, at - 0.6 V (vs. Reversible hydrogen electrode (RHE)) in 0.5 M Potassium chloride (KCl) electrolyte.

Thermoelectric properties of polycrystalline pristine and Pb-doped SnS materials using a conventional hydrothermal method

Tin Sulfide (SnS) has recently garnered significant attention due to its impressive Seebeck coefficient and low thermal conductivity. However, its electrical performance is notably poor, necessitating appropriate doping for its enhancement. To address this, we employed the conventional hydrothermal method to synthesize polycrystals of pristine and lead (Pb)-doped SnS samples to observe the impact on thermoelectric parameters. Utilizing FESEM, we obtained sheet sizes on the nanometer scale and observed irregular sheet-type morphology. HRTEM analysis confirmed the polycrystalline nature of the synthesized samples. Thermal stability assessment through thermogravimetric analysis (TGA) was conducted on all samples up to a temperature of 600 °C. The hydrothermal method resulted in nanostructuring that effectively suppressed the thermal conduction of low-frequency phonons, with increased phonon scattering attributed to the small grain size of particles. For pristine SnS nanoparticles, we determined the lowest total thermal conductivity (κT) to be 0.18 W (m-K)−1, and the highest Seebeck coefficient reached 412.71 μVK−1 at 620 K. In the case of the SnS–Pb(3 wt%) doped sample, there was a slight reduction in the total thermal conductivity (κT) compared to the pristine SnS sample. The pristine SnS sample exhibited the highest electrical conductivity (σ) of 0.21 S/cm at 620 K. In contrast, the SnS–Pb(3 wt%) doped sample demonstrated a twofold increase in electrical conductivity, measuring 0.38 S/cm at 620 K. This enhancement can be attributed to the increased carrier concentration resulting from the Pb(3 wt%) doping of SnS.

Scale-Up, Continuous and Low-Temperature Production of Multimetal Based Electrocatalysts toward Water Electrolysis.

Electrocatalytic water splitting is a crucial strategy for advancing hydrogen energy and addressing the global energy crisis. Despite its significance, the need for a straightforward and swift method to synthesize electrocatalysts with exceptional performance remains pressing. In this study, we demonstrate a novel approach for the preparation of multimetal-based electrocatalysts in a continuous flow reactor, enabling the quick synthesis of a large number of products through a streamlined process. The resultant NiFe-LDH comprises nanoflakes with a high specific surface area and requires only 255.4 mV overpotential to achieve a current density of 10 mA·cm-2 in 1 M KOH, surpassing samples fabricated by conventional hydrothermal methods. Our method can also be applied to craft a spectrum of other multimetal-based electrocatalysts, including CoFe-LDH, CoAl-LDH, NiMn-LDH, and NiCoFe-LDH. Additionally, the NiFe-LDH electrocatalyst is further applied to anodic methanol electrooxidation coupled with cathodic hydrogen evolution. Moreover, the simplicity and generality of our fabrication method render it applicable for the facile preparation of various multimetal-based electrocatalysts, offering a scalable solution to the quest for high-performance catalysts in advancing sustainable energy technologies.

The excellent infrared radiation regulation ability of VO2 nanorods

Dynamic infrared radiation has significantly contributed to thermal comfort by adaptively radiating heat into space without necessitating external energy consumption. This study introduces a novel approach to fabricate dynamic infrared radiation-regulated materials using VO2 nanorods. The VO2 nanorods were synthesized via a conventional hydrothermal method. XRD and SEM analyses confirmed the high crystallinity and uniform size of the VO2 nanorods. HRTEM measurements revealed that the nanorods had an approximate length of 1 μm and a width of 100 nm. These nanorods were combined with KBr and pressed into a tablet form. Subsequent thermal imaging was conducted to assess their dynamic infrared radiation regulation capability. Remarkably, the optimized variation in emissivity for the VO2-based tablets reached up to 0.46. And the Mie scattering theory was used to interprete the insight mechanism. It seems that the Qabs of VO2 nanorod before and after phase transition dominate the dynamic infrared radiation regulation ability at different temperatures. This finding offers a novel, straightforward, and highly efficient energy-saving solution for thermal management systems.

Tailoring the geometry of visible and near-infrared light active CuSe nanostructure for enhanced photocatalytic activity

Semiconductor photocatalysts play a pivotal role in fostering a sustainable environment by harnessing solar energy directly into chemical energy to achieve various photocatalytic processes. Therefore, a visible-infrared active photocatalyst is the next level of demand for solving the alarming environmental issues. In this regard, the present article reports the investigations of crucial mechanisms and conditions leading to pure and defect-free hexagonal 2D CuSe nanosheets (NSs) and the influence of their structural architecture on visible-infrared active photocatalytic performance. Here, it was achieved by the conventional hydrothermal method by varying the pH of the reaction mixture. XRD analysis was used to examine the crystal structure and lattice parameters of CuSe NSs. The presence of H+ ions was suggested to significantly influence the observed anisotropic crystallite growth across different pH conditions. EDS and XPS analysis exhibited the purity and stoichiometry of 2D CuSe NSs, revealing that the obtained stoichiometry was consistent with CuSe composition. The morphological characteristics were investigated using FE-SEM as well as HR-TEM analyses, and the specific surface area was determined using Brunauer-Emmett-Teller analysis in which a significant change occurred in response to the variation in reaction conditions. The optical properties of optimized 2D CuSe NSs show excellent absorption in the visible and near-infrared region utilizing full solar with a notable decrease in emission intensity, suggesting a reduction in recombination rates due to pH-induced changes in the nanoarchitecture. Herein, methylene blue, a well-established model dye, was used as a probe to assess the photocatalytic activity of the synthesized CuSe NSs. Notably, the CuSe NSs synthesized under neutral conditions demonstrate a remarkable methylene blue degradation efficiency, reaching approximately 98 % within approximately 45 minutes, indicating a high degradation rate. Finally, an in-depth exploration into the intricacies of photocatalytic performance, degradation mechanisms, and the recyclability test was conducted, accompanied by a thorough investigation into the feasibility of CuSe NSs for their practical application in photocatalytic wastewater treatment.

Rapid sonochemical synthesis of highly active and stable 2-D inorganic-organic hybrid catalyst for solvent-free CO2 cycloaddition with epoxides

In order to find a better alternative of conventional hydrothermal method, a novel rapid sonochemical route has been developed for the synthesis of inorganic-organic hybrid metal phosphonate (i.e., Copper phenyl phosphonate (CuPPA)) at ambient conditions and examined as a catalyst in the transformation of carbon dioxide into cyclic carbonates in solvent-free condition. For the first time, the present study has explained the sonochemical synthesis of the 2-D nano-architecture of S-CuPPA within a short reaction period of 2 h at room temperature. However, the hydrothermal method requires high temperature of 443 K and reaction time of 48 h. Materials obtained from both methods have been compared using characterization techniques such as XRD, FT-IR, N2 sorption, FESEM, TEM, XPS, and TGA-DTA. Interestingly, S-CuPPA demonstrates crystallites of smaller size and higher surface area than HCuPPA. The S-CuPPA catalyst exhibited higher catalytic performance with conversion = 99 %, selectivity = 99 %, and yield = 99 % without using any solvent at optimized conditions such as catalyst = 30 mg, co-catalyst (TBAB) = 15 mg, pressure = 4 bar, temperature = 100 °C, and time = 24 h. The easy recoverability, stability, and ability to be recycled over five times with more than 93 % conversion demonstrate its ability to be a suitable industrial catalyst.

Comparative study of microwave-assisted and hydrothermal hydroxyapatite synthesis from neutralization slag: Optimization, energy, and adsorption

The study proposes the utilization of microwave-assisted methods for converting neutralization slag (NS) into hydroxyapatite (HAP), offering an alternative to the conventional hydrothermal method. The microwave-assisted approach addresses the challenges encountered in hydrothermal reactions, such as particle agglomeration, reduced specific surface area, prolonged reaction time, high temperature requirements, and inadequate saturation adsorption capacity. By employing the response surface methodology with a Box-Behnken design, the study found that the microwave-assisted method significantly reduced the synthesis time from 90 to 25 min and the temperature from 120 °C to 56 °C. Furthermore, the microwave method consumed only 1/43 of the energy utilized in hydrothermal synthesis. To assess the performance of the synthesized HAP, various detection methods were utilized, including XRD, SEM-EDS, FTIR, Zeta potential, and ICP, which analyzed the crystal structure, crystallinity, morphology, chemical composition, and surface charge of HAP. The BET method was used to measure the specific surface area, further confirming the successful synthesis of HAP. The HAP synthesized through this microwave-assisted method exhibited a saturation adsorption capacity of up to 98.4 mg/g of fluoride ions from vanadium industrial raffinate. This study demonstrates that the microwave-assisted method provides a viable solution for reducing energy consumption and enhancing HAP synthesis efficiency for wastewater treatment in the vanadium industry.

Synthesis, structure and characterization of two new silver-iron based phosphates AgFe2(PO4)2F(H2O)2 and Ag3Fe2(PO4)(HPO4)3

Two new silver-iron based phosphates AgFe2(PO4)2F(H2O)2 (1) with monoclinic P21/n and Ag3Fe2(PO4)(HPO4)3 (2) with triclinic P-1 were synthesized by a conventional hydrothermal method, featuring a dimer structure and a twisted honeycomb-like lattice, respectively. XPS and BVS (Bond Valence Sum) calculations indicated only Fe3+ ions in both compounds, while FT-IR spectra proved the presence of [H2O] in 1 and [OH] groups in 2. Solid-state UV–vis–NIR diffuse reflectance spectra suggested their wide optical band gaps of 2.31 eV and 1.94 eV, respectively. Magnetic measurements indicated that both compounds display a long-range antiferromagnetic ordering at low temperature, showing the change of magnetic entropy of 9.59 J mol−1 K−1 in 1 and that of 14.87 J mol−1 K−1 in 2, respectively.

A new S = 2 kagomé lattice compound with ferromagnetic behaviors

A new compound NaMn3(SeO3)2(HSeO3)6 was obtained by a conventional hydrothermal method. This compound crystallizes in a trigonal system with space group R-3, exhibiting a typical kagomé structure, where the kagomé layers are composed of [MnO6] octahedra linked by [SeO3] groups. Magnetic susceptibility measurements confirm that this compound exhibits a ferromagnetic transition at ∼13 K, as further confirmed by the heat capacity data. The magnetic entropy was estimated, indicating that the system may release almost the entire entropy at low temperature.

A novel nanozyme doped ZnO/r-GO-based sensor for highly sensitive electrochemical determination of muscle-relaxant drug: cyclobenzaprine HCl.

A nanocomposite of Ce-doped ZnO/r-GO was synthesized using a conventional hydrothermal method. The synthesized nanocomposites were utilized for the purpose of sensitive and selective detection of cyclobenzaprine hydrochloride (CBP). The properties of the composite were extensively analyzed, including its morphology, structure, and electrochemical behavior. This study investigates the application of a modified glassy carbon electrode for the detection of CBP, a muscle relaxant used to treat musculoskeletal diseases that cause muscle spasms. The electrode is modified with Ce-doped ZnO/r-GO. Various detection methods, such as cyclic voltammetric and square wave techniques (SWV), were utilized. The composite material showed high effectiveness as an electron transfer mediator in the oxidation of CBP. The electrode showed a good response for SWV evaluations in CBP identification, with a minimum detection limit of 1.6 × 10-8M and a wide linear range from 10 × 10-6 M to 0.6 × 10-7 M, under ideal conditions. The rate constant for charge transfer (ks) and the estimation of the electrochemical active surface area were obtained. A developed sensor exhibited desirable selectivity, long-lasting stability, and remarkable reproducibility. A sensor was used to analyze water, human serum, and urine samples, resulting in positive recovery results.

Solvent Effect on the Structural, Optical, Morphology, and Antimicrobial Activity of Silver Phosphate Microcrystals by Conventional Hydrothermal Method.

The design of particle size and morphology are a promising approach to investigating the properties exhibited by different types of materials. In the present study, the silver phosphate microcrystals (Ag3PO4) were first time synthesized using the hydrothermal and solvothermal method by combination of the solvents water/isopropyl alcohol (SP-IA), water/acetone (SP-AC), water/ammonium hydroxide (AP-AH), all in a ratio of 1:1 (v/v). The synthesized materials were structurally characterized by X-ray diffraction (XRD), Rietveld refinement, and Raman vibrational spectroscopy, where it was confirmed that the pure phase was achieved for all prepared samples. The study of the optical properties by UV-vis diffuse reflectance spectroscopy (UV-vis/DRS) and colorimetry revealed that the obtained materials have an optical bandgap between 2.30 and 2.32 eV. The FE-SEM images collected revealed different morphologies for the synthesized materials, with a predominance of tetraploid-shaped microcrystals for the SP-AC sample, rods for the SP-IA sample, cubes and polyhedral for the SP-WT sample and condensed polyhedral for the SP-AH sample. The photocatalytic performance against the Rhodamine B dye (RhB) was 100%, 98.2%, 94.2%, and 87.8%, using the samples SP-AC, SP-IA, SP-WT, and SP-AH as photocatalyst at time of 12 min. On the other hand, the antimicrobial performance of SP-AC sample showed superior performance, resulting in the minimum inhibitory concentration-MIC of 7.81 μg mL-1 for the strain of E. coli, 7.81 μg mL-1 for the strain of E. aureus, 15.62 μg mL-1 for the strain of P. auruginosa, and 15.62 μg mL-1 for the strains of C. albicans. In this way, was synthesized a promissory antimicrobial and photocatalyst material, through an easy and cost-effective method.

MgHg(SeO3)2(H2O)2: A magnesium mercury selenite with large birefringence

Selenite crystalline materials have been popular owing to the diverse structures and optical performances. A new mercury selenite, MgHg(SeO3)2(H2O)2, was synthesized by using a conventional hydrothermal method. It crystallizes in the monoclinic structure with a C2/c space group, MgHg(SeO3)2(H2O)2 exhibits a three-dimensional (3D) structure, which is made up of [Hg(SeO3)2]2–∞ chains and distorted MgO4(H2O)2 octahedra. Besides, it presents a large birefringence of 0.137 @ 546 nm according to experimental measurement. Synthesis, crystal structure, thermal stability, optical property measurements and theoretical studies were performed in this work.

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.

Synthesis of zeolite X from fly ash in an impinging stream reactor and its mechanisms

The conventional hydrothermal method with magnetic stirring for the synthesis of zeolite X from fly ash has some problems, such as low micromixing efficiency, low mass transfer rate, and long synthesis time. In this study, impinging stream reactor is used to improve the mass transfer and micromixing and the mechanism how the nucleation and crystallization of zeolite is accelerated is explored. The results show that premixing in the impinging stream reactor can reduce the stirring and aging time from 4 h to 20 min because the hydroxyl free radicals resulting from the cavitation effect can accelerate the crystallization of zeolite. After collision, the viscosity of the system is increased from 0.22 Pa·s to 3 Pa·s, which can increase the residence time of cavitation bubbles in the gel solution and effectively inhibit the aggregation of crystal nuclei. As a result, the crystal nuclei in the system are well dispersed. The impinging stream reactor can also accelerate the mass transfer between liquid and solid phases and improve the micromixing of raw materials, so that the polymerization between Si and Al is increased and the nucleation of zeolite X is accelerated. The degree of order of zeolite X samples obtained by premixing in the impinging stream reactor is much higher than that obtained by magnetic stirring. The relative crystallinity after crystallization for 12 h (100 %) is higher than that obtained by magnetic stirring (94.93 %); and the n(Si/Al) is lower than that obtained by magnetic stirring. It is concluded that premixing in the impinging stream reactor can improve the polymerization of aluminosilicate and accelerate the nucleation and crystallization of zeolite X. Under the same conditions, zeolite X synthesized by premixing in the impinging stream reactor has better CO2 adsorption capacity than those synthesized by magnetic stirring and industrial synthesis.

Application of NiFe2O4 nanoparticles towards the detection of ovarian cancer marker

In this work, we explored the potential application of NiFe2O4 magnetic nanoparticles in sensing platforms due to their cost-effectiveness and good magnetic properties. The spinel-type metal oxide was prepared using the conventional hydrothermal synthesis method. The structural, morphological, and magnetic properties of the as-synthesized NiFe2O4 nanoparticles were discussed. The nanoparticles were functionalized with cystamine, glutaraldehyde, and PVDF and then modified with the CA 125 antibody to obtain the immunosensor. FTIR and electrochemical analyses reveal immobilization of the antibody on the surface of the NiFe2O4 magnetic nanoparticles. The immunosensor developed in this work was made on a printed circuit board, allowing it to be used as a point-of-care device. The immunosensor showed excellent stability, reproducibility, specificity, and selectivity. Our findings are of great significance for developing novel, high-performance point-of-care electrochemical biosensors to be applied in detecting the CA 125 antigen, a widely used biomarker for the prognosis of ovarian cancer.

Sb/X (X = Mn, Er, Ho) Co‐Doped Lead‐Free Double Perovskite Cs2NaInCl6 for Single‐Component White Light Emission

AbstractRecently, the incorporation of transition‐metal ions into lead‐free double perovskite has garnered considerable attention for improving the lattice environment and enhancing photoluminescence (PL) to achieve white light emission. Here, Sb/X (Mn, Er, Ho) co‐doped Cs2NaInCl6 (CNIC) microcrystals (MCs) synthesized by conventional hydrothermal method are developed for single‐component white light emission with various photoinduced transition mechanisms. Sb doping in CNIC MCs causes the breaking of non‐parity forbidden transition under 360 nm laser excitation and results in blue emission; Sb/X co‐doping for CNIC MCs successfully broadens the spectrum with multi‐peak emission, which consists of unique X‐peak emission and blue emission peaked at 445 nm. The energy transfer channels from both free excitons state of CNIC and self‐trapping excitons (STEs) state of [SbCl6]3− to X ion are proved and studied by use of steady‐state and time‐resolved PL spectroscopy. Among them, Sb/Er co‐doped CNIC MCs show unique dual‐mode PL under 360 and 980 nm laser excitation. Single‐component white light emitting diode is successfully fabricated by adjusting the composition of Sb/X co‐doped CNIC MCs, which provides an alternative path for realizing single‐component white light illumination.

Photocatalytic activity enhancement by noble metal deposition on faceted F-TiO2 synthesised by microwave assisted method. A study of selective oxidation of gas-phase ethanol in a FBPR reactor

In the present work, fluorinated titanium dioxide (TiO2-F) with high exposition of facet {001} was prepared by following a facile and high yield hydrothermal method assisted by microwave. This faceted TiO2 was then modified by Au or Ag deposition at two different metal loadings (0.125 and 0.25 wt%). A wide physicochemical characterisation of the materials was performed. X-ray difractograms showed high {001} facet exposition in all materials. By X-ray fluorescence it was found that the different samples contained about 5% of fluor. All samples presented high surface area and high uniformity and homogeneity of particles, which highlights the good properties that can be achieved by the microwave synthesis method compared to conventional hydrothermal methods. Oxidation state of the noble metals was studied by XPS. On the other side, TiO2-F and the metallised titania powders were immobilised on polystyrene pellets (PS) for evaluating their gas photocatalytic activity in volatile organic compounds (VOCs) decontamination by following the reaction of photoxidation of ethanol in gas phase. It was found that activity was considerably improved by the addition of noble metals, obtaining high conversion and selectivity to CO2. It is remarkable that the selectivity to CO is almost zero. The highest efficiency was found for the faceted TiO2-F sample with the lowest Au loading (0.125 wt%) immobilised on PS where 91% ethanol conversion and 100% CO2 selectivity were achieved. Different reaction variables were also studied.