Hydrothermal Synthesis Reaction Research Articles

Mild and Efficient Preparation of N-Heterocyclic Organic Molecules by Catalyst-free and Solvent-free Methods.

The small organic molecular compounds with biological activity containing C-C and C-N or C-O bonding were efficiently prepared without catalyst and solvent in the hydrothermal synthesis reactor. Our goal was to explore new applications for the more environmentally friendly and efficient synthesis of bis(indolyl)methyl, xanthene, quinazolinone, and N-heterocyclic derivatives in hydrothermal synthesis reactors under solvent-free and catalyst-free conditions. A greener and more efficient method was successfully developed for the synthesis of bis(indolyl)methyl, heteroanthracene, quinazolinone, and N-heterocyclic derivatives using a hydrothermal synthesis reactor in a solvent- and catalyst-free manner. In a hydrothermal synthesis reactor, bis(indoyl)methyl, xanthene, quinazolinone, and N-heterocyclic derivatives were synthesized without catalysts and solvents. Overall, it is proved once again that the catalyst-free and solvent-free synthesis method has universal value and is a more ideal and environmentally friendly new method, especially the hydrothermal reactor for synthesis.

Deep insights to explain the mechanism of carbon dot formation at various reaction times using the hydrothermal technique: FT-IR, 13C-NMR, 1H-NMR, and UV-visible spectroscopic approaches.

A well-explained mechanism for synthesizing carbon dots (CDs) is not yet explored and is still a subject of great debate and challenge. This study used a one-step hydrothermal method to prepare highly efficient, gram-scale, excellent water solubility, and blue fluorescent nitrogen-doped carbon dots (NCDs) with the particle size average distribution of around 5 nm from 4-aminoantipyrine. The effects of varying synthesis reaction times on the structure and mechanism formation of NCDs were investigated using spectroscopic methods, namely FT-IR, 13C-NMR, 1H-NMR, and UV-visible spectroscopies. The spectroscopic results indicated that increasing the reaction time affects the structure of the NCDs. As the hydrothermal synthesis reaction time is extended, the intensity of the peaks in the aromatic region decreases, and new peaks in the aliphatic and carbonyl group regions are generated, which display enhanced intensity. In addition, the photoluminescent quantum yield increases as the reaction time increases. The presence of a benzene ring in 4-aminoantipyrine is thought to contribute to the observed structural changes in NCDs. This is due to the increased noncovalent π-π stacking interactions of the aromatic ring during the carbon dot core formation. Moreover, the hydrolysis of the pyrazole ring in 4-aminoantipyrine results in polar functional groups attached to aliphatic carbons. As the reaction time prolongs, these functional groups progressively cover a larger portion of the surface of the NCDs. After 21 h of the synthesis process, the XRD spectrum of the produced NCDs illustrates a broad peak at 21.1°, indicating an amorphous turbostratic carbon phase. The d-spacing measured from the HR-TEM image is about 0.26 nm, which agrees with the (100) plane lattice of graphite carbon and confirms the purity of the NCD product with a surface covered by polar functional groups. This investigation will lead to a greater understanding of the effect of hydrothermal reaction time on the mechanism and structure of carbon dot synthesis. Moreover, it offers a simple, low-cost, and gram-scale method for creating high-quality NCDs crucial for various applications.

Synthesis of hierarchically porous Ni foam-supported heazlewoodite Ni3S2 nanorod electrocatalysts for highly efficient oxygen evolution reaction

At present, the design of highly efficient and stable oxygen electrocatalysts for water-splitting cells in alkaline medium is predominantly limited by the sluggish kinetics for the oxygen evolution reaction (OER). This study proposes a facile and reproducible synthesis process to nurture the hierarchically porous Ni3S2 arrays on nickel foam (Ni3S2@NF) for use as a catalyst. For the hydrothermal synthesis reaction, ultrathin nanorod heazlewoodite Ni3S2 catalysts on NF is synthesized by controlling the amount of hydrazine (2 mL) and the processing time/temperatures (150 ℃ for 12 h). Due to the hierarchically porous nanorod morphologies, Ni3S2@NF under O2-saturated 1 M KOH aqueous solution shows excellent OER performance, with a low overpotential of 263 mV at a current density of 100 mA‧cm−2 and a Tafel slope of 72 mV‧dec−1. Further, Ni3S2@NF shows stable potential behavior at around 1.521 V under the constant current operation of 50 mA cm−2 for 50 h. Ni3S2@NF also shows negligible performance degradation during the constant current (at 50 mA cm−2 for 50 h) and voltage cycling (1.25–1.65 V for 1000 cycles) tests in a 1 M KOH solution. The excellent catalytic performance of Ni3S2@NF can be attributed to the hierarchically porous and ultrathin nanorod structures, the multi-valence-state character of Ni element, and the synergistic effect of NF, and high intrinsic catalytic active electrocatalysts for the OER.

Synthesis and characterization of TiO2/ZnO heterostructural composite for ultraviolet photocatalytic degrading DOM in landfill leachate.

In order to investigate the photocatalytic degradation of dissolved organic matter (DOM) in landfill leachate, TiO2/ZnO heterostructural composite powders were fabricated combining with hydrothermal synthesis and solid-state reaction method. The prepared TiO2/ZnO composite powders consist of anatase TiO2 nanoparticles distributing on the surface of wurtzite ZnO particles. The optical band gap of TiO2/ZnO powder is less than that of pure ZnO or TiO2 powder. TiO2/ZnO catalyzers show high ultraviolet-degradation efficiency for methylene blue and dissolved organic matter. The degradation rate of TiO2/ZnO powder for fulvic acid-like substances in landfill leachate is 2.99 times that of pure ZnO powder, and is 1.30 times that of pure TiO2 powder. The degradation of fulvic acid-like substances by TiO2/ZnO photocatalyst reduced some molecular weight of benzene ring structure substances in leachate. The effective separation of electron and hole in heterostructural TiO2/ZnO photocatalyst is the main reason for its high photocatalytic degradation efficiency of DOM in landfill leachate.

Influence of CaO Content on the Fly Ash–Lime System Hydrothermal Synthesis Reaction Under Autoclave Curing

As a substitute for traditional Portland cement, the development and research of “low-temperature-synthesized fly ash cement” has been receiving extensive attention. This study explores the effects of calcium oxide content on the fly ash–lime system hydrothermal synthesis reaction under autoclave curing, focusing on the effects of CaO content on the strength of the cement paste. The changes in phase composition, microstructure, and morphology were characterized using X-ray diffraction and scanning electron microscopy (SEM) analysis. The results show that with an increase in the CaO content, the amounts of β-C2S and C12A7 in the gelling material also increase. However, when the CaO content is very high, the amounts of β-C2S and C12A7 in the gelling material no longer increase, and the strength is lost.

Preparation of a novel polysulfone membrane by incorporated with carbon dots grafted silica from rice husk for dye removal

This study demonstrated the modification of polysulfone (PSf) membrane by incorporating carbon dots (CDs) and silica (SiO2) as additives for membrane’s permeability and dye rejection enhancement. Both the CDs and SiO2 were synthesized from rice husk and the carbon dots were impregnated on SiO2 to form CD/SiO2 composite through a hydrothermal synthesis reaction. The impregnation of CDs had shown increment of hydrophilic functional groups with negative surface charge on the SiO2. A series of CD/SiO2 composite embedded ultrafiltration (UF) membranes was developed. Results revealed that the CD/SiO2 additive was endowed with enhanced membrane properties in terms of pore size, pore distribution, hydrophilicity and negative surface charge. All the modified membranes demonstrated higher permeability and dye rejection. Among the membranes, 1.0 wt% of CD/SiO2 loading showed excellent pure water permeability increment of 111 % due to improved membrane hydrophilicity and enlargement of membrane pores. Notably, the 2.5 wt% of CD/SiO2 membrane showed the highest dye removal of 50.54 % compared to pure PSf membrane of 14.52 % albeit it had similar permeability as the pure PSf membrane. This study had demonstrated a circular economy approach in turning rice husk biomass into useful additives for membrane nanotechnology application.

Development of a high pressure stirring cell up to 2 GPa: a new window for chemical reactions and material synthesis

ABSTRACT A new method for stirring under high pressure conditions has been developed and tested. The key component is a Teflon cell assembly equipped with magnetic stirring function, which is capable to operate across a wide pressure range, up to at least 2 GPa, in a large volume press. The setup enables adjustable stirrer rotation rate and detection of stirring in a sample, e.g. to observe liquid–solid phase transitions at high pressure. The viscosity limit of stirring is ca. 500 times that of water at room temperature (i.e. ∼500 mPas). Moreover, we show that zinc oxide nanoparticles hydrothermally synthesized at 0.5 GPa and 100°C under stirring conditions show an order of magnitude smaller size (100 nm) compared to those synthesized under non-stirring conditions (1 μm). The wide pressure range for stirring of viscous media opens interesting possibilities to produce novel materials via hydrothermal synthesis and chemical reactions.

Template-assisted synthesis of LiNi0.8Co0.15Al0.05O2 hollow nanospheres as cathode material for lithium ion batteries

Based on hydrothermal synthesis and solid-phase thermal reaction, LiNi0.8Co0.15Al0.05O2 hollow nanospheres (LNCA HNSs) were synthesized by using SiO2 hollow nanospheres as hard template. Firstly, the SiO2 HNSs were prepared. Then, (Ni0.8Co0.15Al0.05)CO3 nanosheets grew on the surface of SiO2 HNSs to form SiO2@(Ni0.8Co0.15Al0.05)CO3 hollow nanospheres with double shells by hydrothermal method. Finally, the above precursors and lithium source were calcined at high temperature, and then SiO2 template was etched to obtain hollow LNCA HNSs. The characterization results showed that the LNCA HNSs are hollow spheres with a diameter of about 1.8 μm. The shell thickness of LNCA HNSs is about 300 nm. Compared with LNCA nanoparticles and LNCA microparticles, LNCA HNSs showed excellent stability, high capacity, and good rate performance as cathode materials for lithium ion batteries. The LNCA HNSs exhibited a reversible capacity of 202.4 mA h g−1 at 0.1 C and good stability of 179.1 mA h g−1 at 1 C after 80 cycles.

Photocatalytic decontamination of tetracycline and Cr(VI) by a novel α-FeOOH/FeS2 photocatalyst: One-pot hydrothermal synthesis and Z-scheme reaction mechanism insight

Tetracycline and Cr(VI) as non-biodegradable environmental contaminants have attracted increasing attention because of their chronic toxicity. In this regard, the environmentally friendly Z-scheme photocatalytic decontamination system has been widely used for contaminant treatment. Herein, a novel 3D Z-scheme α-FeOOH/FeS2 composite photocatalyst was successfully synthesized for the first time via a simple one-pot hydrothermal method. X-ray diffraction (XRD) and Fourier-transform infrared (FT-IR) analyses and high-resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS) demonstrated that the O component of the heterogeneous nanostructures formed by the FeOFe linkages in α-FeOOH was replaced by S to generate FeSFe linkages in the resulting FeS2. As expected, the novel 3D Z-scheme α-FeOOH/FeS2 composites exhibited remarkable photocatalytic activity for Cr(VI) reduction and tetracycline degradation compared to pure α-FeOOH. Photoluminesence (PL) measurement and electrochemical impedance spectroscopy (EIS), as well as density functional theory (DFT) calculations, suggested that the enhanced photocatalytic activity of the Z-scheme α-FeOOH/FeS2 composite can be attributed to the improved photo-absorption properties and the effective separation of photo-induced charge carriers caused by the Z-scheme system of the as-prepared 3D α-FeOOH/FeS2 composites. Thus, this work may facilitate the effective design of α-FeOOH-based photocatalysts.

Functional Superhydrophobic Coating Systems for Possible Corrosion Mitigation

Because of their repellent, corrosion-mitigating, anti-icing, and self-cleaning properties, superhydrophobic coatings have numerous applications from windshields to textiles. A superhydrophobic coating is defined as one having a water contact angle (WCA) greater than 150° with a surface sliding angle less than 10°, and very low hysteresis between the advancing and receding angles. Its surface exhibits the so-called “lotus leaf effect,” whereby water bounces and balls up on contact. Here, water droplets run off readily, taking along dirt and dust for a self-cleaning effect that keeps the surface dry. The chemical composition of a surface affects the WCA, which can rise to 120°, but to achieve a WCA greater than 150°, which is considered superhydrophobic, an additional micro- and nanostructural component is needed. This functional hierarchical micro- and nanomorphology is exhibited in nature by plants and insects. A superhydrophobic coating on metallic substrates promises to provide corrosion mitigation by blocking oxygen and electrolytes, which are needed for the initiation of corrosion at the surface and interface. The methods used for preparing functional superhydrophobic coatings include sol-gel processing, layer-by-layer assembly, etching, lithography, chemical and electrochemical depositions, chemical vapor deposition, electrospinning, hydrothermal synthesis, and one-pot reactions. In this work, some research studies conducted to develop robust and durable superhydrophobic coatings are discussed in detail and analyzed for possible corrosion mitigation on the surfaces of metals and alloys. Scientists, engineers, students, and other participants in automotive, aircraft, energy, defense, electronics, and other industries will benefit greatly from this work.

Localized ZnO Growth on a Gold Nanoantenna by Plasmon-Assisted Hydrothermal Synthesis.

The excitation of localized surface plasmon resonances (LSPRs) in metal nanostructures enables subwavelength photon localization and large electric field enhancement, which can be advantageously used to strongly enhance light-matter interactions at the nanoscale. For this purpose, efficient methods for deterministically handling and arranging nanomaterials at the exact position of the localized electric field are required. In this Letter, we propose a novel method based on a hydrothermal synthesis reaction to locally and selectively synthesize zinc oxide in a plasmonic nanoantenna. We first make evident the role of LSPR for achieving efficient heating of gold nanostructures. Then, by selectively addressing one of the LSPRs of a gold antenna, we demonstrate that localized zinc oxide formation at the targeted location of the antenna can be achieved due to the nanoscale confinement of the heat production.

Hydrothermal Synthesis of Three-Dimensional Perovskite NiMnO3 Oxide and Application in Supercapacitor Electrode

Supercapacitors are attractive as a major energy storage device due to their high coulombic efficiency and semi-permanent life cycle. Transition metal oxides are used as electrode material in supercapacitors due to their high conductivity, capacitance, and multiple oxidation states. Nanopowder transition metal oxides exhibit low specific surface area, ion diffusion, electrical conductivity, and structural stability compared with the three-dimensional (3D) structure. Furthermore, unstable performance during long-term testing can occur via structural transition. Therefore, it is necessary to synthesize a transition metal oxide with a high specific surface area and a stable structure for supercapacitor application. Transition metal oxides with a perovskite structure control structural transition and improve conductivity. In this study, a NiMnO3 perovskite oxide with a high specific surface area and electrochemical properties was obtained via hydrothermal synthesis at low temperature. Hydrothermal synthesis was used to fabricate materials with an aqueous solution under high temperature and pressure. The shape and composition were regulated by controlling the hydrothermal synthesis reaction temperature and time. The synthesis of NiMnO3 was controlled by the reaction time to alter the specific surface area and morphology. The prepared perovskite NiMnO3 oxide with a three-dimensional structure can be used as an active electrode material for supercapacitors and electrochemical catalysts. The prepared NiMnO3 perovskite oxide showed a high specific capacitance of 99.03 F·g−1 and excellent cycle stability with a coulombic efficiency of 77% even after 7000 cycles.

Ni–Fe Phosphate/Ni Foam Electrode: Facile Hydrothermal Synthesis and Ultralong Oxygen Evolution Reaction Durability

Nickel–iron phosphate film with a porous surface formed by ultrathin nanotubes was successfully grown on Ni foam (NF) through a simple hydrothermal route at 150 °C for 90 min in the presence of HCl...

Current State of Studies on Synthesis and Application of Zinc Stannate (Review)

The published works representing the current state of research in the field of the synthesis and application of zinc stannate are reviewed. The data on crystalline modifications of ZnSnO3 are provided and the primary areas of the application of zinc stannate are investigated. Options of various synthesis methods, such as chemical vapor deposition, reactions under high pressure, hydrothermal synthesis, ion-exchange and solid-phase reactions, the coprecipitation method, and the sol-gel method, are demonstrated.

Synthesis of Graphene Hydrogel and Graphene Oxide/Polyaniline Composites for Asymmetric Supercapacitor

As a kind of new carbon materials, graphene has excellent performances such as superior conductivity, high specific surface area (2675 m2 g−1), and high cycle life. But graphene sheets are easily restacked by van der Waals interactions during the processes of preparation, storage, and application of them, which can loss ultrahigh specific surface area. The restacking of graphene sheets could be prevented by constructing graphene hydrogel (GH) or graphene composite. In this work, GH was prepared by a one-step hydrothermal synthesis reaction and glucose is used as a reducing agent, while graphene oxide/polyaniline (GP) composites was prepared by coating polyaniline on GO through in situ chemical polymerization of aniline. Then an asymmetric supercapacitor (GH//GP) was further assembled, where GH and GP are the positive and negative electrodes, respectively. The electrochemical properties of GH, GP, and GH//GP are studied using voltammetry and galvanostatic charge/discharge. The consequences indicate that the energy density of GH//GP reaches 5.6 W h kg−1 at power density of 226.5 W kg−1 and 3.1 W h kg−1 at energy density of 8446.2 W kg−1.

Preparation of autoclave concrete from basaltic lunar regolith simulant: Effect of mixture and manufacture process

Abstract To build a permanently inhabited base on the Moon is a vitally important step to developing lunar exploration and deep space detection. Indigenous materials become a significant requirement for lunar construction as transporting construction materials from Earth is extremely expensive. Fortunately, construction materials can be fabricated by utilizing in situ materials on the Moon surface. Autoclaving technology is a feasible method for lunar construction material manufacture. In this study, basaltic lunar regolith simulant (LRS) was utilized to imitate the lunar regolith as major raw material. Firstly, Ca(OH)2 and PI 52.5 were compared to choose better calcareous material. In addition, the influence of calcareous material ratio, LRS fineness, briquetting pressure value and autoclaving craft on mechanical property were discussed to determine an appropriate material system and manufacture process. Furthermore, strength effect mechanism was expounded by the investigation of pore characteristics and hydration products. The results indicated that Ca(OH)2 was more effective in producing better performance LRS autoclaved concrete and introducing appropriate amount of Ca(OH)2 can improve the strength and promote target hydration products generation effectively. Meanwhile, the increasing of LRS fineness resulted in weakening of compressive strength which was ascribe to the increasing pore volume caused by the arch effect during briquetting process with finer LRS particles. Moreover, augmentation of briquetting pressure value made significant improvement in compactness of rough-body and autoclaved specimens and finally resulted in increment of density and enhancement of strength. On the other hand, the extension of saturated vapor pressure duration time enhanced the compressive strength by promoting hydrothermal synthesis reaction and generating of target hydration products.

Na2MoO4 as both etcher for three-dimensional holey graphene hydrogel and pseudo-capacitive feedstock for asymmetric supercapacitors

Porous graphene hydrogel (pGH) have attracted considerable attention due to their unique properties and practical applications in the field of supercapacitors. Their exceptional porous structure (high degree of porosity, high pore volume and high specific surface area) combined with the inherent properties of graphene can fully broaden the ion channel and then improve the performance of the supercapacitor. Here a general and scalable synthesis method to prepare three-dimensional integrate electrode of porous graphene hydrogel (pGH) has been developed using Na2MoO4 as pore-making agent by a hydrothermal synthesis reaction. The as-prepared porous graphene hydrogel can be used as an electrode with a gravimetric capacitance of 473 F g−1, nearly three times that of the hydrogel electrode without puncturing pores, contributes to its highly specific area and ion channels. In addition, the nanocomposite of MoO3/GH can also works as positive electrode while the MoO3 nanoparticles produced during the hydrothermal process is an ideal material for pseudo-capacitance. At the same time, the sodium molybdate is added into the acidic electrolyte to interact with hydrogen ions to produce the pseudo-capacitance either. Then, an asymmetric supercapacitor (pGH||MoO3/GH) was fabricated by using pGH as negative electrode while MoO3/GH as positive electrode, and the maximum energy density is 40.34 W h kg−1 at a current density of 1 A g−1 while the power density is 565.13 W kg−1.

Effect of Additives on the Morphologies of Hydrothermal Products Prepared from Semi-Dry Desulfurization Residues

For effective utilization of the residues, calcium sulfate whiskers were prepared from semi-dry desulfurization residues by hydrothermal synthesis reactions. Aiming at collecting the products with a long length and large aspect ratio, the additives, including sodium oleate, sodium dodecyl benzene sulfonate (SDBS), and sodium citrate, were added to control the growth of the crystal. Compared with no additives, whiskers with relatively a longer length and larger aspect ratio could be obtained in the presence of sodium oleate or SDBS. The sodium citrate made the whiskers thicker and shorter. Then, the effects of the additives on crystal growth and the morphology of the hydrothermal products were investigated with the aid of X-ray diffraction (XRD) patterns and molecular dynamics simulations. According to the results of XRD, the diffraction intensity of the crystal face (400) increased under the influence of sodium oleate, promoting crystal growth along the c-axis. The molecular structures of the corresponding faces were built based on the strong peaks shown in the XRD patterns. The atomic distribution on the computed crystal faces was presented. The interaction energies on different faces were calculated to illustrate the different adsorption configurations of the additives. Among the calculated faces, the interaction energies on (400) were both most negative for sodium oleate and SDBS. Therefore, sodium oleate and SDBS preferred to adsorb on (400). As a result, the growth of (400) was thus inhibited and the crystal grew along the c-axis. Compared with sodium oleate and SDBS, the lowest adsorption energy of sodium citrate on the face (310) indicated that sodium citrate has no positive effect on the directional growth of the crystal parallel to c-axis. The molecular simulation results were virtually identical to the crystal faces analysis results.

Zn(tp)(RdmB)(H2O)] and [Cd(tp)(RdmB)]: Two Unusual One-Dimensional Rhodamine B Coordination Polymeric Ribbons as Luminescent Sensors for Small Molecules and Metal Cations

Two new complexes, [Zn(tp)(RdmB)(H2O)] (I) and [Cd(tp)(RdmB)] (II) (tp = terephthalate, RdmB = rhodamine B), are obtained by similar hydrothermal synthesis reactions. X-ray crystallography reveals that both compounds are one-dimensional (1D) polymeric solids, in which I (C36H36N2O8Zn) ascribes to monoclinic C2/m space group, Z = 4 (a = 18.834(5) A, b = 16.859(5) A, c = 10.111(3) A, β = 97.638(4)°), while II (C108H102N6O21Cd3) crystallizes in monoclinic P21/n, 4 (a = 12.2309(1) A, b = 61.5661(7) A, c = 12.5852(1) A, β = 93.951(1)°). Owing to the difference in the coordination sphere around the metal center, four-coordinated zinc centers for I bridged by linear tp molecules associated with RdmB ligands result in an interesting 1D infinite zigzag tape-like structure, whereas six-/seven-coordinated cadmium centers for II bridged by the same ligands generate a novel 1D infinite biserrated edge ribbon structure with a 2,3,3-linked {62.10}{63}{6} network or a simplified 2,4-linked {43.62.8}{4} topological networ...

Optimization of hydrothermal conversion of bamboo (Phyllostachys aureosulcata) to levulinic acid via response surface methodology

In this study, the dilute acid hydrolysis of lignocellulosic bamboo (Phyllostachys aureosulcata) particles to levulinic acid in a hydrothermal synthesis reactor is reported. The aim of the study was to optimize the reaction conditions for maximum levulinic acid production in terms of reaction time (t), reaction temperature (T) and HCl concentration (cHCl) via Response Surface Methodology (RSM). A maximum levulinic acid yield of 9.46 w% was predicted at the following reaction conditions: t of 3 h, T of 160 °C and cHCl of 0.37 M. A maximal experimental yield of levulinic acid of 10.13 w% was observed, which in respect to the cellulose fraction of the bamboo particles corresponds to 34.60 w% or 48.05 mol%. Furfural, which is formed by the hemicellulose fraction of bamboo, has not been observed within the boundaries of the RSM model, since it is already degraded under the given reaction conditions. The conversion of levulinic acid and furfural occurred more or less simultaneously, however, furfural was more vulnerable to degradation reactions at the given process conditions. Therefore, if both fractions (cellulose + hemicellulose) are required to be valorized, further optimization is required. However, the global results of this study provide insight in the potential of lignocellulosic bamboo as an alternative platform to fossil sources.