Hydrothermal Synthesis Process Research Articles

Fabrication of Rhenium Disulfide/Mesoporous Silica Core-Shell Nanoparticles for a pH-Responsive Drug Release and Combined Chemo-Photothermal Therapy.

A stimuli-responsive drug delivery nanocarrier with a core-shell structure combining photothermal therapy and chemotherapy for killing cancer cells was constructed in this study. The multifunctional nanocarrier ReS2@mSiO2-RhB entails an ReS2 hierarchical nanosphere coated with a fluorescent mesoporous silica shell. The three-dimensional hierarchical ReS2 nanostructure is capable of effectively absorbing near-infrared (NIR) light and converting it into heat. These ReS2 nanospheres were generated by a hydrothermal synthesis process leading to the self-assembly of few-layered ReS2 nanosheets. The mesoporous silica shell was further coated on the surface of the ReS2 nanospheres through a surfactant-templating sol-gel approach to provide accessible mesopores for drug uploading. A fluorescent dye (Rhodamine B) was covalently attached to silica precursors and incorporated during synthesis in the mesoporous silica walls toward conferring imaging capability to the nanocarrier. Doxorubicin (DOX), a known cancer drug, was used in a proof-of-concept study to assess the material's ability to function as a drug delivery carrier. While the silica pores are not capped, the drug molecule loading and release take advantage of the pH-governed electrostatic interactions between the drug and silica wall. The ReS2@mSiO2-RhB enabled a drug loading content as high as 19.83 mg/g doxorubicin. The ReS2@mSiO2-RhB-DOX nanocarrier's cumulative drug release rate at pH values that simulate physiological conditions showed significant pH responsiveness, reaching 59.8% at pH 6.8 and 98.5% and pH 5.5. The in vitro testing using HeLa cervical cancer cells proved that ReS2@mSiO2-RhB-DOX has a strong cancer eradication ability upon irradiation with an NIR laser owing to the combined drug delivery and photothermal effect. The results highlight the potential of ReS2@mSiO2-RhB nanoparticles for combined cancer therapy in the future.

A novel approach for the facile synthesis of zinc oxide/carbon hybrid systems from corn distillers soluble: Surface modification and characterization for sustainable remediation

Sustainable, efficient, and environmentally friendly ways to tailor the carbonaceous materials from bio sources with desired functionalities remain a challenge around the world. In this study, we represent a novel approach to synthesize carbon hybrid material based on Zinc Oxide/carbon (ZnO/C) hybrid systems by catalytic hydrothermal process via crosslinking reaction through nucleation and growth of ZnO particles at the functional groups of oxidized carbon material. This research explored the volarization of Condensed Corn Distillers Soluble (CDS) as a carbon precursor to synthesize biobased carbon spheres. Surface modification of the produced carbon spheres took place using zinc chloride (ZnCl2) during hydrothermal carbonization (HTC). Zinc chloride (ZnCl2) was used to function as a catalyst during HTC and functioned as a ZnO source to synthesize (ZnO/C) hybrid systems. Design Expert software v13 was used to design the hydrothermal carbonization (HTC) experiments and response surface methodology was used to find the optimized conditions for the preparation of carbon hybrid systems. The hydrothermal synthesis process introduced 3D stone like zinc oxide particles onto the carbon matrix. These particles were self-assembled onto the carbon framework to produce carbon hybrid systems with unique physical, chemical, structural and functional properties. Herein, the obtained carbon hybrid systems (ZnO/C) were investigated and discussed in detail. ZnO/C hybrid systems were analyzed for surface morphology using scanning electron microscopy (SEM) that presented a 3D spherical interconnected phase and XRD analyses were used for phase crystallinity that showed new crystalline phases such as hopeite and zincite after the ZnCl2 incorporation. Surface functional groups were also analyzed by FTIR and results confirmed the presence of hydrophilic groups such as –OH, CC, and COOH on the surface of ZnO/C hybrid carbon systems. This study provided the insightful guidance for tailoring novel design of multifunctional carbon material as an adsorbent/catalyst for various applications of sustainable remediation.

Hybrid-Mechanism Synergistic Flexible Nb2O5@WS2@C Carbon Nanofiber Anode for Superior Sodium Storage.

Sodium-ion batteries (SIBs) have demonstrated remarkable development potential and commercial prospects. However, in the current state of research, the development of high-energy-density, long-cycle-life, high-rate-performance anode materials for SIBs remains a huge challenge. Free-standing flexible electrodes, owing to their ability to achieve higher energy density without the need for current collectors, binders, and conductive additives, have garnered significant attention across various fields. In this work, we designed and fabricated a free-standing three-dimensional flexible Nb2O5@WS2@C carbon nanofiber (CNF) anode based on a hybrid adsorption-intercalation-conversion mechanism of sodium storage, using electrospinning and hydrothermal synthesis processes. The hybrid structure, aided by synergistic effects, releases the advantages of all materials, demonstrating a superior rate performance (288, 248, 211, 158, 90, and 48 mA h g-1 at the current density of 0.2, 0.5, 1, 2, 5, and 10 A g-1, respectively) and good cycling stability (160 mA h g-1 after 200 cycles at 1 A g-1). This work provides certain guiding significance for future research on hybrid and flexible anodes of SIBs.

Electrical and structural engineering of nanoflower-like NiMn-layered double hydroxide by V modulation for high-performance hybrid supercapacitors

This work produced V-doped NiMn-layered double hydroxide(V-NiMnLDH) composite positive electrode material directly on nickel foam using a simple one-step hydrothermal synthesis process. The composite's 3D nanoflower-like design increased spatial utilization, surface area, and active sites for Faradaic redox reactions. The composite material has a specific capacitance of 1551 F g−1 at 1 A g−1 and 85.6 % capacitance retention at 10 A g−1, demonstrating exceptional cycle stability. In addition, we combined V-NiMnLDH with commercial activated carbon to create an asymmetric supercapacitor (ASC) with 63.5 Wh kg−1 energy density and 975 W kg−1 power density. After 5000 charge-discharge cycles, the gadget preserved 89.7 % of its specific capacitance. This material outperforms similar electrode materials in certain performance evaluations. We also used density functional theory (DFT) computations to analyze each element in the V-NiMnLDH composite and explain their electronic density of states contributions. This theoretical framework explains how V doping improves capacitance. Band structure simulations also showed V-NiMnLDH's higher charge transfer and conductivity compared to intermediate products, explaining its extraordinary capacitance performance. Our work combines theoretical and experimental data to advance catalyst design and high-performance energy storage materials.

A novel approach to Hg2+ determination in water samples using carbon dots based on paper and fluorescence digital image analysis

AbstractBACKGROUNDThis work proposes the use of a simple, inexpensive method for the hydrothermal synthesis of fluorescent carbon dot nanoparticles (CDs) from rice starch aimed at the determination of Hg2+ in water. The proposed method involved using a paper‐based analytical device coupled to a 3D plate, with a UV‐LED chamber and a smartphone for the acquisition and analysis of the fluorescence digital images of the CDs.RESULTSThe size of the carbon dots ranged from 0.5 to 3 nm, with an average particle size of ~1 nm. The functionalization of carbon dots with methimazole allowed a high selective for Hg2+ determination. The results obtained showed a linear response R2 of 0.997 and Hg2+ concentration in the range of 0.5–45.0 μmol L−1 with a limit of detection and limit of quantitation of 0.23 and 0.62 μmol L−1, respectively. The results of the study show that there were no significant differences, at 95% confidence level, between the data obtained from the application of the proposed method and the reference method.CONCLUSIONThe proposed method is in line with the principles of green chemistry, as it involves the use of renewable sources for starch extraction and a hydrothermal synthesis process that does not employ toxic reagents. In addition, the method employs only 15 μL reagent/sample. © 2024 Society of Chemical Industry (SCI).

NH2 functionalized MWCNT based self-healing conductive composite for smart sensing

Amino (NH2) functionalized multi-walled carbon nanotubes (MWCNTs) provide superior electrical and mechanical properties, comes at high material cost. The objective of this study is to develop a low-cost, simple, and effective method of NH2-MWCNTs synthesis. To this objective, we have developed in-house NH2 functionalized MWCNTs by reacting with NH4OH using hydrothermal synthesis process. The synthesized NH2-MWCNTs is compared and found compatible to the commercially available one, which is then used to develop self-healing and stretchable (SHS) conductive composite by incorporating into the self-healing supramolecular polymer. The electro-mechanical and self-healing properties of the composite can be tuned by controlling the amount of NH2-MWCNTs loading into the polymer matrix. The optimized composite showed a maximum strength of 286.15 kPa at its maximum strain rate of 410 %, and a high electrical conductivity of 8.23 S cm−1. It is further utilized to demonstrate SHS strain sensor for biomechanical signal detection, which exhibits high sensitivity to human wrist’s flexion and extension. Furthermore, it exhibits a high sensitivity with average TCR value of −5.2 % ℃-1 in a wider temperature range (25–100 ℃). Considering the low-cost in-house synthesis approach as well as the developed sensors’ performances, this study will put a paradigm shift within this research field.

PRODUCTION OF CuO/ZrO2 NANOCOMPOSITES IN POWDER AND FIBER FORMS

CuO/ZrO2 composite systems were synthesized in two different ways and comprehensively characterized with X-ray diffraction(XRD), Fourier transform infrared spectroscopy(FTIR), scanning electron microscopy(SEM), transmission electron microscopy(TEM), and energy dispersive X-ray spectroscopy(EDX). These metal oxide samples were prepared by hydrothermal synthesis and electrospinning process. In these methods, the same metal salts were used as precursors. Separately produced ZrO2 nanoparticles(NPs) and CuO particles have spherical and cube-like shapes, and both morphologies have monoclinic structures. However, ZrO2 and CuO particles do not have uniform diameters, and the average size of these particles ranges between 6–17 and 215–847 nm, respectively. Moreover, CuO/ZrO2 nanocomposite particles(NCPs) were synthesized using a facile and one-pot hydrothermal technique. They have uniform, spherical, and monoclinic structures with a 15nm average diameter. Furthermore, ZrO2 fibers were produced with the electrospinning process as highly crystalline structures after annealing, with a 230 nm average fiber diameter. In addition, ZrO2 fibers were doped with hydrothermally synthesized CuO particles with a drop-casting method for the first time. This study clearly shows that particle-fiber structure allows the development of the efficiency of p-type counterparts by using only 0.5-1.5wt.% n-type. With these results, two methods can be used to produce heterostructure CuO/ZrO2 composite particles/fibers and as potential for photocatalytic degradation.

A Hydrothermal Synthesis Process of ZSM-5 Zeolite for VOCs Adsorption Using Desilication Solution

ZSM-5 zeolite is a kind of high-value-added porous aluminosilicate zeolite. The use of the coal gasification slag utilization process by-product desilication liquid as a silicon raw material to replace the current raw materials such as water glass will help reduce production costs and achieve high-value utilization of solid waste. ZSM-5 zeolites for volatile organic compounds (VOCs) adsorption were prepared by a one-step hydrothermal method using the desilication solution prepared from coal gasification slag as the main silicon source and sodium source. The effects of crystallization reaction time, the crystallization temperature, the Na2O/SiO2 molar ratio, and the SiO2/Al2O3 molar ratio on the relative crystallinity and the specific surface area of the ZSM-5 zeolite were investigated and optimized. The optical reaction conditions were as follows: a crystallization time of 12 h, a crystallization temperature of 170 °C, a Na2O/SiO2 molar ratio of 0.2, and a SiO2/Al2O3 molar ratio of 200. The optimal ZSM-5 zeolite synthesized is hexagonal, with regular grains, a relative crystallinity of 101.48%, a specific surface area of 337.48 m2·g−1, and a pore volume of 0.190 cm3·g−1. And the optimal ZSM-5 zeolite was composed of SiO2 content of 97.52 wt%, Al2O3 content of 1.58 wt%, Na2O content of 0.33 wt%, and SiO2/Al2O3 molar ratio of 104.93. Na2O/SiO2 molar ratio is 0.0033. The results of static adsorption experiments show that the static adsorption capacities of ZSM-5 zeolite for p-xylene, benzene, toluene, and butyl acetate were 118.85, 69.98, 68.74, and 95.85 mg·g−1, respectively, which can effectively adsorb VOCs. The synthetic process of the ZSM-5 zeolite is a simple preparation process and short in synthesis time. The results of this study not only help to realize the high-value utilization of silicon components in solid waste, but also provide an economical and effective way to synthesize VOCs adsorption materials.

Two-Dimensional Tellurium Nanosheets for the Efficient Nonenzymatic Electrochemical Detection of H2O2

This study reports, for the first time, the utilization of two-dimensional (2D) tellurium (Te) nanosheets for the efficient nonenzymatic detection of hydrogen peroxide (H2O2). H2O2 acts as a pivotal biomarker with widespread applications across environmental, biological, industrial, and food processing domains. However, an excessive accumulation of H2O2 in the body poses a severe threat to human life. Consequently, the imperative need for a selective, sensitive, and cost-effective sensing platform for H2O2 detection has gained paramount significance. Employing a low-cost and straightforward hydrothermal method, Te nanosheets were synthesized to address the escalating demand for a reliable detection platform. The as-synthesized Te nanosheets are characterized through Raman spectroscopy and atomic force microscopy techniques. The electrochemical performance of the Te nanosheets integrated onto a glassy carbon (Te-GC) electrode was thoroughly investigated using cyclic voltammetry, differential pulse voltammetry, and chronoamperometry. The experiments were designed to evaluate the response of the Te-GC electrode in the presence and absence of H2O2, alongside its performance in the detection of other pertinent interfering analytes. The sensor shows a limit of detection of 0.47 µM and a sensitivity of 27.2 µA µM−1 cm−2 towards H2O2. The outcomes of this study demonstrate the efficacy of Te nanosheets as a promising material for nonenzymatic H2O2 detection in urine samples. The simplicity and cost-effectiveness of the hydrothermal synthesis process, coupled with the notable electrochemical performance of the Te/GC electrode, highlight the potential of Te nanosheets in the development of a robust sensing platform. This research contributes to the ongoing efforts to enhance our capabilities in monitoring and detecting H2O2, fostering advancements in environmental, biomedical, and industrial applications.

Efficient oxygen evolution using conductive cobalt-based metal-organic framework

The electrically conductive Cobalt-benzene-1,3,5-tribenzoate metal–organic framework (Co-BTB) was easily synthesized using the hydrothermal synthesis process. The framework showed a low overpotential (only 170 mV to obtain 10 mA cm−2) for the oxygen evolution reaction (OER) surpassing the benchmark electrocatalyst IrO2 which showed an overpotential of 250 mV at the same obtained current density. Moreover, the Co-BTB possesses good kinetics with an estimated Tafel slope of only 46.5 mV dec−1. It provided a high density of catalytic centers with electrically conductive characteristics, as suggested by ECSA. The framework was identified as a promising MOF electrocatalyst for the OER due to its performance as well as its chemical and electrochemical robustness.

Preparation and characterization of anhydrous magnesium carbonate: Effect of different anions of the magnesium sources

The hydrothermal synthesis process for anhydrous magnesium carbonate (MgCO3) from Na2CO3 and three different soluble magnesium sources (MgSO4, MgCl2 and Mg(NO3)2) are investigated. High purity MgCO3 particles are synthesized at the reaction temperature of 160 °C, the reaction time of 6 h, and the reactant ratio of 1:1 in the three groups of experiments. The effect of different anions of the magnesium sources are investigated through comparison of the morphologies and specific surface areas of the obtained MgCO3 particles. MgCO3 particles using Mg(NO3)2 as the magnesium source shows the thinnest layers stacked structure with flawless surface and the least specific surface area. Besides, the PHREEQCI computation results show that the water activity of the reaction solution using Mg(NO3)2 as the magnesium source is the lowest. Based on the above results, the possible synthesis mechanism of MgCO3 with the different magnesium sources are proposed.

Mixed phase anatase nanosheets/brookite nanorods TiO2 photocatalysts for enhanced gas phase CO2 photoreduction and H2 production

CO2 photoreduction and H2 photocatalytic production reactions have been studied on different TiO2 polymorphs (anatase and brookite) engineered with specific nanocrystal shape. Anatase TiO2 materials of nanosheet morphology and brookite TiO2 of nanorod morphology were developed via a hydrothermal synthesis process. Mixed-phase anatase/brookite TiO2 materials of the above extreme cases were also developed, controlling the phase composition. The materials were fully characterized by a variety of techniques including structural, morphological, textural and electronic properties characterization. N2 physisorption analysis and CO2 adsorption isotherms have shown that minimum amount of brookite phase (i.e. ca. 7 wt%) in the final material improved the textural properties and the CO2 uptake ability. Electron paramagnetic spectroscopy (EPR) provided evidences for improvements in the formation and availability of photogenerated electrons in the mixed-phase materials. CO2 photoreduction was increased by ca. 220% in the optimized mixed-phase anatase/brookite TiO2. Photocatalytic H2 production rates were also improved by ca. 140%. The results in the present study have shown that the TiO2 phase as well as the amount of each TiO2 polymorph plays vital role in photocatalytic efficiency and that the photocatalytic improvement depends greatly on the specific reactions. The new insights provided herein would be of interest for studied focusing on materials shape engineering and phase composition and their effect on activity.

Ppb-level detection of trimethylamine as biomarker in exhaled gas based on MoO3/V2O5 hierarchical heterostructure

The toxic gas trimethylamine (TMA) with fishy odor can not only be used as an indicator for evaluating seafood spoilage, but also as a biomarker for trimethylaminuria and kidney disease. This paper constructs a ppb-level trimethylamine gas sensor that operates at room temperature based on MoO3/V2O5 nanocomposites, which were fabricated by hydrothermal synthesis process. The adsorption energy of TMA on sensitive materials was calculated through the density functional theory, and the sensing mechanism was explored by simulating the adsorption process of TMA on the sensitive materials. The response (11.37%) of MoO3/V2O5 composites to ultra-low concentration (20 ppb) TMA was better than that of pure MoO3 nanorods (5.49%) and V2O5 nanospheres (6.36%) at room temperature. Compared with pure MoO3 sensors, an n-n heterojunction is formed between MoO3 and V2O5, which enhances the sensing performance of pure sensing material for TMA. In addition, the detection of exhaled gas in simulated kidney disease patients indicates that this sensor has great potential as an effective TMA detection tool in the field of non-invasive disease diagnosis.

Facile synthesis of silver doped WO3 nanocomposite with 2-D reduced graphene oxide to boost photocatalytic efficiency

Two-dimensional (2D) carbonaceous substances and their nanohybrid have lately garnered great interest as photocatalysts owing to outstanding contribution toward photocatalytic degradation and purification. A novel 2-D rGO dependent Ag/WO3 photocatalyst was successfully fabricated using hydrothermal and ultrasonic synthesis processes. The photocatalysts properties such as surface, structure, morphology and optical were studied using modern analytical techniques. The photocatalytic effectiveness of the synthesized product was evaluated by measuring the rate of Methylene blue (MB) dye mineralization when exposed to a visible source. By virtue of its lower charge transfer resistance (Rct; 0.6 Ω) and better electrical conductivity, the photocatalyst demonstrated much stronger photocatalytic behavior toward dye removal than pure tungsten trioxide and silver doped WO3 photocatalysts. The Ag/WO3/rGO photocatalyst degraded the dye at a rate of almost 96.92% faster than Ag/WO3 (0.011 min−1) and WO3 (0.009 min−1). The separation of photogenerated electron (e-) and hole (h+) pairs and the rise in optical absorbance contributed to a notable improvement in WO3′s photocatalytic efficiency after adding silver dopant and rGO sheets. Transient photocurrent measurements revealed that the graphene-based material has persistent photo-excited charge carriers.

Synthesis-in-place hydrothermal growth of hematite nanorods on patterned substrate for highly sensitive and rapid acetone detection

Hematite (α-Fe2O3) is an attracting gas sensing material for detecting volatile organic compounds due to its adjustable semiconducting properties and abundant reserves. However, its low sensitivity in thin film structures requires the design of nanostructures for practical applications. Herein, we present a facile hydrothermal method for directly grown hematite nanorods on patterned SiO2/Si substrate. It was demonstrated that hematite nanorods were synthesized directly on the area of Pt interdigitated electrodes on a SiO2/Si substrate using a one-step hydrothermal synthesis process. The optimal synthesis conditions were determined by analyzing the morphology and gas sensing performance of hematite nanorods, which varied with synthesis time. Rapid response time of less than 5 s to acetone at 350 °C was achieved with pristine hematite nanorods. To improve the gas sensing properties, hematite nanorods were decorated with Au nanoparticles, dramatically enhanced sensitivity and selectivity to acetone in comparison with the sensing properties of pristine hematite nanorods. Furthermore, the sensors displayed rapid response and long-term stability. Our synthesis-in-place hydrothermal method for hematite nanorods expands the potential use of this strategy to fabricate high-performance gas sensors with various nanostructured metal oxides.

Graphene oxide modified K, P co-doped g-C3N4 and CoFe2O4 composite for photocatalytic degradation of antibiotics

BackgroundThe utilization of photocatalysts for the removal of contaminants present in aquatic systems has attracted great interest due to their promising removal efficiencies. MethodsIn this work, phosphorus and potassium co-doped g-C3N4 (KPCN) was heterostructured with CoFe2O4 photocatalyst and modified with graphene oxide (GO) by using hydrothermal synthesis process (KPCN/GO/CoFe2O4). The formation of the KPCN/GO/CoFe2O4 nanocomposite was confirmed by different characterization techniques. The KPCN/GO/CoFe2O4 nanocomposite followed the S-scheme charge transferal route. The photocatalytic activity of KPCN/GO/CoFe2O4 composite was analysed for tetracycline (TC) and doxycycline (DOX) antibiotics removal using visible light. Significant findingsKPCN/GO/CoFe2O4 showed the highest photocatalytic activity compared to g-C3N4, KPCN, and KPCN/GO photocatalysts. KPCN/GO/CoFe2O4 photocatalyst showed 85% degradation for tetracycline antibiotics within 60 min and 99% degradation for doxycycline antibiotics within 60 min. The degradation efficiencies were improved with doping and further improved by adding GO and CoFe2O4. The light-harvesting was improved by doping, GO enhanced photocatalyst adsorption capabilities and heterojunction formation improved the ability to separate charges. Heterojunction with magnetic CoFe2O4 photocatalyst also improved the separation ability and reusability of KPCN/GO/CoFe2O4 photocatalyst.

NiCo2S4 nanocone arrays on three-dimensional graphene with small hole diameters for asymmetric supercapacitor

Chemical vapor deposition (CVD) is utilized to fabricate 3D graphene (3D Gr) with small hole diameters using nickel nanoparticles sintered at high temperatures as the sacrificial template. NiCo2S4 nanocone arrays (NiCo2S4 NCAs) are vertically grown in situ on the 3D Gr by a seeding layer and hydrothermal synthesis process. The results show the hole diameters of 3D Gr are ∼ 3 µm. The small hole diameters of 3D Gr not only enhances the high electrical conductivity but also increases the contact area to the solution. Moreover, NiCo2S4 NCAs on the 3D Gr can provide more electrochemical redox activities and shorter channels for ion transport. NiCo2S4 NCAs/3D Gr is applied as a supercapacitor electrode, showing a specific capacitance of 948.9 F/g at 1 A/g. In addition, an asymmetric supercapacitor is assembled with the NiCo2S4 NCAs/3D Gr as the cathode material and the activated carbon as the anode material. The supercapacitor has an energy density of 64.1 Wh/kg at the power density of 1153.8 W/kg. It exhibits 90 % capacitance retention under 10, 000 charge and discharge cycles at 10 A/g.

Nanostructured semiconducting properties of Sn-doped graphene synthesised by the hydrothermal method

This work developed a hydrothermal process for the effective synthesis of Sn-doped graphene nanoparticles. To prepare the samples at 180°C in carbon tetrachloride organic solvent and different levels of Sn concentrations (0.3, 0.6 and 0.9) were used. A variety of analyses were carried out on the prepared materials, including XRD, SEM with EDX, TEM, AFM, UV, PL and I-V. The XRD analysis revealed good crystallinity and hexagonal structure in Sn-doped graphene nanoparticles. An SEM micrograph reveals that the morphology is flower, nano-chalk pieces and agglomerated at some places. The TEM images clearly specify the spherical and are agglomerated at some places. Topography images (AFM) show that hydrothermal treatment at different concentrations influences the growth of Sn-doped graphene NPs. The bandgap of Sn-doped graphene nanoparticles is estimated as 2.23, 3.7 and 4.7 eV. All the p-Si/n-graphene diodes exhibited excellent rectification with less reverse current. The impact of metal (Sn) doping concentration favourably decreases the n value of the p-Si/n-Sn-doped graphene diode. In the current work, it is shown that the p-Si/n graphene diode is highly sensitive to various concentrations of graphene.

Synthesis of 2D type A molecular sieves by alkaline removal of natural kaolin

Type A molecular sieves have been extensively employed in various fields. It is noteworthy that the direct synthesis of type A molecular sieves from natural kaolin is a common practice among researchers. Traditional type A molecular sieves are characterized by a three-dimensional cubic lattice structure. In this study, our objective is to facilitate the transformation of type A molecular sieves into a two-dimensional layered configuration by employing a two-dimensional layered material as a templating agent. In this research, natural kaolin serves as the primary source material. To eliminate impurities including quartz, illite, and dolomite, an alkali-based solvent extraction method is employed, yielding amorphous silicon and aluminum compounds. Subsequently, a graphene-based templating agent is introduced, and a hydrothermal synthesis process is employed to fabricate two-dimensional type A molecular sieves. The method described herein yields two-dimensional layered type A molecular sieves with a crystallinity exceeding 90%, thereby resulting in a specific surface area that is approximately 11-fold greater compared to their three-dimensional type A counterparts. The applicability of this methodology can be extended to the valorization of low-grade natural mineral resources, optimizing their utility. Furthermore, the approach presented herein for the synthesis of two-dimensional molecular sieves is of a universal nature, offering valuable insights that can serve as a reference for the synthesis of various other categories of two-dimensional molecular sieves.

Microporous exposure on catalytic performance of MoVNbTeOx mixed metal oxides in the oxidative dehydrogenation of ethane

The catalytic performance of the non-purified MoVNbTeOx catalyst was optimized by changing the composition of the synthesis gel method in the hydrothermal synthesis process. However, the enhancement in activity was more pronounced for the post-treatment process of the non-purified catalyst. The catalytic performance of non-purified MoVNbTeOx catalysts and phase-pure M1 catalysts in the oxidative dehydrogenation of ethane (ODHE) were enhanced by water agitation post-treatment. The results showed that the phase-pure M1 catalyst obtained by treating the MoVNbTeOx catalyst with nitric acid had an increased activity per unit mass, but with a mass loss of catalyst materials during the purification process. After several days of post-treatment with water agitation, the catalytic activity of the non-purified MoVNbTeOx and the M1 samples gradually increased and stabilized, where both catalysts had a comparable catalytic performance. All the samples were systematically characterized, showing that the catalytic performance of the samples was mainly correlated with the enhanced specific surface area/pore volume. The results show that for the hydrothermally synthesized MoVNbTeOx catalysts, the reaction takes place in the micropores and the key to improve the performance of MoVNbTeOx catalysts is to effectively expose the active sites. Physical post-treatment process that does not require nitric acid or hydrogen peroxide for purification is also effective in enhancing catalyst activity by boosting the active site.