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The utilization of coal fly ash derived from circulating fluidized bed combustion (CFBFA) still faces great challenges because of its unique characteristics. In this study, a zeolitic material with Na-P1 zeolite as the main phase was successfully synthesized via a hydrothermal method by using CFBFA as the raw material. The effects of hydrothermal temperature, time, and added CTAB amount on the characterizations of synthesized materials were investigated by XRD, SEM, and XPS. The properties of the optimal zeolitic material and its adsorption performance for Pb2+ in aqueous solution were evaluated. The influences of pH, initial concentration, dosage, and temperature on Pb2+ adsorption were also examined. Results revealed the following optimal parameters for the synthesis of zeolitic material: NaOH concentration of 2 mol·L-1, solid-to-liquid ratio of 1:10 g·ml-1, hydrothermal temperature of 110 °C, hydrothermal time of 9 h, and CTAB amount of 1 g (per 100 ml solution). The adsorption capacities of the zeolitic material reached 329.67, 424.69, and 542.22 mg·g-1 when the pH values of aqueous solution were 5, 6, and 7, respectively. The Pb2+removal efficiency can reach more than 99% in aqueous solution with the initial concentrations of 100–300 mg·L-1 under pH 6 and suitable adsorbent dosage. The adsorption and kinetics of Pb2+ on the zeolitic material can be described by Langmuir isotherm and pseudo-second-order kinetic models, respectively. The ion exchange between Pb2+ and Na+ and chemisorption are the main adsorption mechanism. All these findings imply that the synthesis of low-cost adsorbent for Pb2+ removal from weak acid and neutral aqueous solution provides a highly effective method to utilize CFBFA.

The photocatalytic performance of the semiconductor CdS can be improved with carbon materials capable of limiting photocorrosion and the fast recombination of photogenerated charges. For this purpose, carbon derived from biomass exhibit several advantages including low cost, high abundance, and renewability. Here, photocatalytic CdS nanorods modified with carbon derived from the leaves of Japanese raisin trees were synthesized via a single hydrothermal step. Composite CdS nanorods with 5% biomass-derived carbon photocatalyzed H2 evolution 1.8 times faster than unmodified CdS at a rate of 5.71 mmol g−1 h−1. The apparent quantum efficiency of 5%C/CdS nanorods was 14.96%. Furthermore, the addition of biomass-derived carbon to CdS nanorods augmented the stability of the semiconductor under visible light. The characterization of the composite PC indicated that a larger specific surface area, as well as upgraded charge separation caused by biomass-derived carbon, were involved in the acceleration of photocatalytic hydrogen production.

Vanadium dioxide is considered to be a promising material in most fields because of its special reversible metal-insulator transition (MIT) near ambient temperature. Pure VO2(M) is usually synthesized by a hydrothermal method combined with a subsequent annealing process or one-step hydrothermal synthesis. Both synthetic routes have the disadvantages of long reaction times. In this report, a new synthesis method of VO2(M) nanoparticles was established under liquid conditions. First, the V2O4·2H2O precursor was prepared successfully by using N2H4·2HCl-reduced V2O5 under thermostatic stirring without any reagent auxiliary. Second, the V2O4·2H2O suspension in water transformed into VO2(M) nanocrystals under hydrothermal synthesis. The intermediate and final products were characterized by XRD, SEM, HRTEM, XPS and DSC. The morphology of prepared VO2(M) exhibits a snowflake-like structure (approximately 1.0–4.0 μm in length, 0.5–3.0 μm in width and 50–200 nm in thickness). The phase-transition temperature is 65.49 °C. In addition, the reaction route of "V2O4·2H2O →V2O4·xH2O → VO2(B) → VO2(M) transformation" and reaction mechanism were established by testing the precipitate at different times at the hydrothermal stage.

A large surface area with high active site exposure is desired for the nano-scaled electrocatalysts fabrication. Herein, taking NiMoO4 nanorods for example, we demonstrated the advantages of the microwave-assisted hydrothermal synthesis method compared to the traditional hydrothermal approaches. Both monoclinic structured NiMoO4 in the nanorods morphology are found for these samples but it is more time-saving and efficient in the Ni-Mo synergism for the catalyst obtained by microwave-assisted hydrothermal syntheses method. When evaluated for urea oxidation, the current density can reach 130.79 mA/cm2 at 1.54 V, about 2.4 times higher than that of the counterpart catalyst (54.08 mA/cm2). Moreover, largely improved catalytic stability, catalytic kinetics and rapid charge transfer ability are found on the catalyst obtained by the microwave-assisted approach. The high catalytic performance can be attributed to the high surface area and active site exposure of NiMoO4 nanorods formed by microwave irradiation. Considering the less time, facile synthesis condition and efficient components synergism, the microwave-assisted hydrothermal synthesis method might work better for the nanostructure electrocatalysts fabrication.

ZnO nanorods combined with different concentrations of reduced graphene oxide were synthesized using the hydrothermal method. Structural properties of these nanocomposites were studied by X-ray diffraction analysis. Morphological studies on the shape and size of nanorods were carried out by scanning electron microscopy. X-ray diffraction results revealed highly-crystalline nanorods with a hexagonal wurtzite structure. The morphology of as prepared samples is characterized presence of one-dimensional rod-like nanostructures. Crystallite size, stress and lattice strain were determined by Scherrer equation and Williamson–Hall method. The average particle size of samples calculated from microstructural and morphological analyses are highly interrelated. Microraman spectra exhibited both characteristic bands of ZnO and reduced graphene oxide in the low frequency (300–500 cm−1) and high frequency (1300–1600 cm−1) ranges, respectively, furthermore confirming the efficiency of the hydrothermal synthesis of ZnO/reduced graphene oxide nanocomposites. The band gap of the nanocomposite is lower (2.96 eV).compared to that of ZnO (3.10 eV), as determined from the analysis of UV absorbance spectra.

Polypyrrole/Fe2O3 (PPy/Fe2O3) nano-seeds with distinctive electrochemical properties have been successfully synthesized using improved hydrothermal processes. The study highlights the nano-seed like morphology of polypyrrole/Fe2O3 achieved by lowering both the reaction temperature and time (150 ℃ for 4 h), which are appreciable for energy storage applications. The obtained PPy/Fe2O3, analyzed using different techniques like X-ray photoelectron spectroscopy (XPS), Field Emission Scanning Electron Microscopy (FESEM), Fourier Transform Infrared (FTIR) spectroscopy. Compositional and morphological studies confirmed the formation of interconnected PPy/Fe2O3 nano-seeds. Cyclic Voltammetry response displays superior electrochemical performance of the PPy/Fe2O3. The interconnected nanostructures with voids allow more electrolyte ions to contact the active material, which significantly increases conductivity and electrochemical performance. As compared to the reported hydrothermal methods, the optimized routes take 4 h to achieve a specific nano-seed like morphology which is favorable for energy storage application.

In this investigation, ZnO nanostructures were coated via hydrothermal process on glass substrate surfaces, which were treated by acidic and alkaline solutions. Furthermore, the ZnO structure was doped by different amounts of Al+3 ions to investigate the microstructural variation. Characteristics of the samples by XRD and SEM analyses confirmed the formation of different morphologies and various crystal sizes for the nanostructured ZnO on the substrates including nanoflower, nanorod, and nanopanel morphologies. Furthermore, XRD results showed that the Zn2+ concentration was a crucial factor in changing the grain size. EDS analysis confirmed the uniform distribution of Al dopant, while the FTIR spectra revealed the presence of Al–O and Zn–O stretching bonds in the coatings. The results confirmed that the sample, which was etched by fused NaOH had a uniform and compacted structure. Moreover, it was evident the proposed treatment and synthesis process was successful in the formation of uniform nanostructured ZnO film on the glass substrate without the requirement for seed layer deposition.

An improved hydrothermal synthesis of shape-controlled, size-controlled 60 nm SrTiO3 nanocuboid (STO NC) supports, which facilitates the scalable creation of platinum nanoparticle catalysts supported on STO (Pt/STO) for the chemical conversion of waste polyolefins, is reported herein. This synthetic method (1) establishes that STO nucleation prior to the hydrothermal treatment favors nanocuboid formation, (2) produces STO NC supports with average sizes ranging from 25 to 80 nm with narrow size distributions, and (3) demonstrates how SrCO3 formation and variation in solution pH prevent the formation of STO NCs. The STO synthesis was scaled-up and conducted in a 4 L batch reactor, resulting in STO NCs of comparable size and morphology (m = 22.5 g, davg = 58.6 ± 16.2 nm) to those synthesized under standard hydrothermal conditions in a lab-scale 125 mL autoclave reactor. Size-controlled STO NCs, ranging in roughly 10 nm increments from 25 to 80 nm, were used to support Pt deposited through strong electrostatic adsorption (SEA), a practical and scalable solution-based method. Using SEA techniques and an STO support with an average size of 39.3 ± 6.3 nm, a Pt/STO catalyst with 3.6 wt % Pt was produced and used for high-density polyethylene hydrogenolysis under previously reported conditions (170 psi H2, 300 °C, 96 h; final product: Mw = 2400, Đ = 1.03). As a well-established model system for studying the behavior of heterogeneous catalysts and their supports, the Pt/STO system detailed in this work presents a unique opportunity to simultaneously convert waste plastic into commercially viable products while gaining insight into how scalable inorganic synthesis can support transformative manufacturing.

Phosphorylated chitosan (P-CS) was successfully synthesized using a facile experimental setup of hydrothermal method that was applied to the adsorption of anionic Acid Red 88 (AR88) from aqueous media. The adsorption process obeyed the pseudo-second-order (PSO) kinetic model. In contrast, the adsorption isotherm conformed to the Langmuir model, with the maximum adsorption capacity (qm = 230 mg g−1) at 303 K. Both external and intraparticle diffusion strongly influenced the rate of adsorption. The insights from this study reveal that P-CS could be easily prepared and regenerated for reusability applications. The adsorption mechanism and intermolecular interaction between P-CS and AR 88 were investigated using Fourier transform infrared (FTIR) spectroscopy and calculations via Density Functional Theory (DFT). The key modes of adsorption for the P-CS/AR 88 system are driven by electrostatic attractions, H-bonding, and n-π interactions. The findings herein reveal that P-CS is a promising adsorbent for the removal of anionic dyes such as AR88 or similar pollutants from water.

In this paper, CeVO4 nanostructures were produced with controlled hydrothermal method using hydrazine, cerium nitrate, and ammonium vanadate as reactants. Reaction control was performed utilizing hydrazine and ethylenediamine as new reactants. Other effective parameters such as solvent and surfactant were also carefully studied and optimized. The products were then identified through XRD, EDS, FTIR, FESEM, and BET analyses. FESEM results showed that by adjusting the concentration of ethylenediamine, hydrazine, and PVP surfactant, a rod-shaped morphology with suitable porosity could be created. Due to the high potential of CeVO4 in electrochemical processes, it was first employed for electrochemical storage of hydrogen. The amount of hydrogen storage in nanostructures produced with rod-shaped morphology was about 2575 mAh/g, which is very significant compared to products obtained with sodium hydroxide with spherical morphology.

During the synthesis of CdTe quantum dots (QDs) by the hydrothermal method, a CdS shell layer is naturally formed by the thermal decomposition of thiol ligands, and CdTe/CdS core/shell QDs are produced. Herein, we investigate the selective synthesis of CdTe and CdTe/CdS QDs to control the thermal decomposition of thiol ligands by changing the Te/Cd molar ratio of the precursor solutions. ...

Bifunctional photocatalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) have attracted growing interest to understand the mechanisms governing different evolution reactions, and the bifunctional activity of a single type of crystalline photocatalyst has gained especial attention. We herein report the high photocatalytic OER and HER activities of Bi2WO6 nanoplates (BWO NPs) which are synthesized by a simple hydrothermal method, and the switchable OER and HER performances controlled by the pH value of the precursor solvent. In the pH range from 4 to 9, the thickness of BWO NPs along the [0 0 1] direction exhibits interesting dependence on the pH value, which decreases as the pH value increases. Correspondingly, the BWO NPs obtained at the pH value of 7 (BWO-7) show the highest photocatalytic OER activity, while the BWO NPs synthesized at the pH value of 9 (BWO-9) exhibit the highest photoactivity towards HER. The electronic band structure analysis indicates that the highest photocatalytic OER activity is related to the band alignment of the valence band maximum of Bi2WO6, which determines the efficient separation of photogenerated electrons and holes as well as the fast charge transfer kinetics. The crystal facet evolution resulting from thickness reduction promotes the exposure of {0 0 1} facets for HER and decreases the exposure of {1 0 0} and {0 1 0} facets for OER. This work provides new insights into the combined effects of crystal facets and electronic band structures on photocatalysis.

TiO2 nanotube arrays (TiO2 NTs) were regarded as the outstanding semiconductors for the photocatalytic application in waste water treatment and H2 generation, and CdS nanoparticles as the visible light sensitizers were traditionally used to enhance the photocatalytic performance. In this paper, CdS–CuS co-sensitizers were deposited on TiO2 NTs by one-pot hydrothermal method, and the Cu/Cd ratio was changed to adjust the hybrid photocatalyst composition and electron transfer. The photocatalytic data indicated that suitable CdS–CuS composition could effectively enhance the photocatalytic pollutant removal and photocurrent/H2 evolution and the hybrid photocatalyst also exhibited the high stability by the inhibition of CdS photocorrosion. The p-n heterojunction construction of TiO2 NTs/CdS–CuS benefited the solar response, photoelectron separation and photocatalytic reaction, and the photocatalytic mechanism and photoelectron transfer were investigated. The p-n heterojunctional photocatalyst is supposed to apply in environmental remediation and new energy development.

International audience; Anglesite (PbSO4) is a lead sulfate that belongs to the barite group and is naturally ubiquitous in the environment. This work describes a simple way to synthesize crystalline lead sulfate by using a straightforward hydrothermal procedure. Typically, Pb(NO3)2 and Fe2(SO4)3 precursors were mixed and heated at 94°C for 24h. The synthesized samples have been characterized by coupling X-Ray diffraction (XRD) to spectroscopic methods (FTIR and micro-Raman), X-ray absorption spectroscopy (XAS) and electronic microscopy (SEM and TEM). In fine, the results about this new well crystalline synthetic anglesite confirm the efficiency and the importance of this cheap protocol and the synthesized phases obtained. Moreover, the environmental stability and bioaccessibility of anglesite has been done to evaluate environmental stability of anglesite 2 under various physico-chemical conditions and sanitary risks. Finally, the paper allows to obtain precise data on a pure phase in order to be able to more easily evaluate and understand the role of anglesite in As-polluted sites and soils.

In this work, a novel honey/bayberry (HSHB) microsphere was prepared via a simple and green hydrothermal method to investigate the UO22+ adsorption behavior in simulated nuclear effluent. The results showed that spherical HSHB (about 40 nm) had the maximum adsorption capacity of 271.00 mg/g at 328.15 K and displayed a desirable selectivity for the UO22+. Furthermore, combined with the characterization analysis and adsorption experimental results, the phenolic hydroxyl group of HSHB could be combined with UO22+ through chelation. Therefore, these facts indicate that HSHB could be used as a low-cost and environmentally friendly adsorbent for UO22+ removal from nuclear effluent.

International audience; The sintering of uranium oxide powders prepared by hydrothermal conversion of oxalates was studied. A dilatometric study first showed that among the synthesis conditions, only the pH largely impacted the densification, notably through the powders morphology. Three samples (single crystals-pH = 1, microspheres-pH = 2 and nano-powders-pH = 8) were further selected to study their sintering behaviour. Densitometric and granulometric data then allowed establishing sintering maps. For single crystals and microspheres, densities above 96%TD were obtained at 1700°C. In contrast, only 2 to 8 hours at 1500°C were needed to yield comparable results for nano-powders. These observations confirm that the hydrothermal conversion of oxalates can be considered as a promising route for the synthesis of actinide oxides, which can subsequently be sintered directly.

Na3MnCO3PO4 (NMCP) is considered one of the promising cathode materials for sodium-ion batteries due to its high theoretical capacity. The hydrothermal method is an efficient, environmental-friendly, and simple route with low instrument cost to prepare active cathode materials such as NMCP. In this research, magnetic stirring was applied to promote the hydrothermal synthesis, and NMCP was produced by controlling different stirring times. This method results in the formation of pure NMCP upon only 45 min processing time. According to the ICP results, the Na to Mn ratio in the NMCP approached the stoichiometric value of 3 by prolonging the stirring time. By analyzing the charge-discharge behavior of the NMCP materials synthesized through different reaction times, it was found that the NMCP produced at 120 C for 480 min had the highest discharge capacity of 94 mAh g−1, which was resulted from the increased Na to Mn ratio of 2.51. Besides, using Avrami's model, a kinetic equation was proposed for the particles' formation under the stirring hydrothermal process at 120 C. Stirring the solution during the hydrothermal synthesis offers a fast, scalable and eco-friendly way of producing better performing NMCP cathodes with uniform morphological characteristics for sodium-ion batteries.

MnO2 nanorods are prepared using a hydrothermal method, and used as precursors for the synthesis of LiMn2O4 nanorod-based active material for the cathode of lithium-ion batteries. The effects of additives, pressure, reactant concentration in the solution, and reaction time during the hydrothermal synthesis on the morphology of MnO2 are examined. For the synthesis of the LiMn2O4 nanorods, two synthetic methods, hydrothermal processing of the MnO2 precursor in a Li-containing solution, and the solid-state reaction of the precursor with LiOH·H2O powder are tested. The morphological and electrochemical properties of the resulting materials are then analyzed. The rate and cycle performances of the LiMn2O4 nanorods are considerably improved by a composite coating of Li-ion-conductive Li2O–2B2O3 and electrically conductive carbon. Because the conductive properties of these coating materials can be obtained with low crystallinity of them, superior coating performance is attainable with relatively low-temperature of after heating, which is advantageous in preserving the morphology of LiMn2O4 nanorods.

– The current study aims to prepare an Nb,Ta-containing ordered mesoporous catalyst MCM-41, using hydrated mixed oxide of niobium and tantalum, extracted from the columbite ore processing, as an alternative source of these metals. Direct hydrothermal synthesis was employed to incorporate the metals into the molecular sieve structure using the TEOS + sodium silicate mixture as silica source and varying Nb and Ta content in terms of Si/Me (Me = Nb and Ta) molar ratios of 60, 30 and 15 to evaluate the influence of the charge of these metals on both structural formation and properties of the material. The material was characterized by XRD, SEM, TEM, N2 adsorption, UV–Vis-DRS, and FTIR investigations to the incorporation of the metal into the MCM-41 framework. The techniques employed proved the successful replacement of Si atoms by metallic cations of Nb and Ta. The catalyst showed good structural order preservation and surface area (>600 m2 g-1) with mesoporous behavior with capillary condensation even at a higher metal load. This research signifies a successful procedure of a novel bimetallic mesoporous material with promising properties for several applications using an abundant ore as a metal source.

Hydrothermal synthesis of brookite-type titanium dioxide was examined using aqueous sols of titanate nanosheets, which were prepared with Ti[OCH(CH3)2]4 and N(CH3)4OH by a bottom-up process in aqueous solutions. Highly pure brookite powders were yielded at hydrothermal temperatures as low as 120 °C and N(CH3)4OH/Ti[OCH(CH3)2]4 molar ratios greater than 2. Although titanate nanosheets are formed at N(CH3)4OH/Ti[OCH(CH3)2]4 ≥ 0.4, the addition of excess N(CH3)4OH was critical in forming highly pure brookite powders. Excess N(CH3)4+ caused the precipitation of layered titanates, which were formed by stacking titanate nanosheets. Additionally, the crystal nucleation of brookite occurred in the precipitates. Then, the adsorption of titanate nanosheets on brookite particles caused the particles to transform into rod-like shapes elongated along the c-axis. The adsorbed titanate nanosheets were structurally converted into brookite under the influence of the underlying brookite crystal. Despite having a rough surface, the resulting brookite particles were single crystal-like. Moreover, the use of any tetraalkylammonium hydroxides other than N(CH3)4OH did not yield brookite. The addition of N(CH3)4OH to the reaction sols yielded precipitates of small titanate nanosheets. The morphology of the titanate nanosheets could have a significant influence on brookite crystallization.

Herein, we report the single-step synthesis of ZnO nanostructures by a simple urea hydrolysis method. Pure phase ZnO and hydrozincite (Zn5(CO3)2 (OH)6) nanostructures are easily obtained separately at the optimized hydrothermal conditions, which involve controlling the urea concentration and reaction parameters such as temperature and time. Outside of these conditions, hydrozincite (Zn5(CO3)2 (OH)6) with a small admixture of basic zinc carbonate Zn4CO3 (OH)6⋅H2O are obtained as by products. X-ray diffraction and electron microscopy reveal that the obtained ZnO sample is comprised of spherical nanoparticles and have a hexagonal wurtzite crystalline structure. Further, a single-step synthesis approach was developed that produces micron sized rod-shaped ZnO structures.

We provide the material synthesis method, crystal structure information, and characterization of a novel mixed-valent metal oxide KIn0.33IIITe0.67VITe2IVO7, closely related to zirconolite (CaZrTi2O7), a radioactive waste immobilized material, having a 3D framework. The reported metal oxide containing an alkali-metal cation (K+), main-group cation (In3+), tellurate, and tellurite has been synthesized as both single crystals and a pure polycrystalline phase through a hydrothermal synthesis method. Single-crystal X-ray diffraction indicates that KIn0.33Te2.67O7 crystallizing in the orthorhombic space group Cmcm (No. 63) reveals a 3D framework structure with a 1D channel consisting of Te/InO6 octahedra and TeO4 polyhedra. An interesting transition reaction from KIn0.33Te2.67O7 to KIn(TeO3)2 under hydrothermal conditions at 230 °C is discussed.

With the advantages of high power density, long cycle life, and fast charging, supercapacitor has become a research hotspot in recent decades. Graphene is considered as an ideal electrode material for supercapacitors because of its special electrical and mechanical properties. In order to prepare graphene that can be used as supercapacitor electrode materials, various methods are proposed, among which hydrothermal method is mostly used, but graphene prepared using this method always agglomerates seriously and rarely have pores that might be helpful for the increase of electrochemical performance. Therefore, sodium alginate, which has strong hydrogen bonding with graphene oxide and might be helpful to optimize the structure of graphene in the reduction process, should be considered. In this paper, by optimizing the ratio of reducing agent and graphene oxide in hydrothermal reaction, two samples that exhibit better performance were obtained. On this basis, sodium alginate was added in the process of hydrothermal reduction of graphene oxide, and the effect of it on the structure and properties of graphene was explored. The results demonstrate that pore structure is formed and the rate performance is improved obviously by adding sodium alginate.

The research on the best technology of large-scale hydrothermal preparation of Co–Mn–Fe–Zn–O (CMFZ) material will provide reference for its industrial production. The CMFZ nanopowders were prepared on a large scale by hydrothermal method to explore the optimal process to obtain NTC ceramic materials with high consistency. The precursor morphology showed that their grain sizes were small, and with the increase of reaction temperature, reaction time, and stirring speed, the grain size of the powder first decreased to 20.01 nm and then increased to 36.56 nm, and the grain size of the corresponding ceramic samples also decreased and then increased. The optimum preparation conditions at 150 °C for 9 h and stirring speed of 200 rpm resulted in the smallest precursor grain size of 20.01 nm and the highest room-temperature resistivity ρ25 and material constant B25/50 of 1.44 kΩ cm and 3953 K, respectively, with average deviations of 0.089 and 0.237, indicating that the consistency of electrical properties were better. The study of the optimum technique for the large-scale hydrothermal preparation of CMFZ materials will provide a reference for their industrial production.

Using oxalic acid as a reducing agent, hydroquinone (HQ), graphene (GO), and acidified carbon nanotubes (CNTs) were compounded directly to synthesize reduced graphene oxide (rGO)/CNTs/HQ hydrogels by a one-step hydrothermal method, and the phase composition and electrochemical properties were studied. During the hydrothermal reaction, the π bond in the hydroquinone molecule will be compounded with the large π bond on the surface of rGO due to the π-π interaction. At the same time, CNTs play a role of spacer and support in rGO/CNTs/HQ and improve the conductivity of rGO/CNTs/HQ. The prepared rGO/CNTs/HQ has a mass-specific capacitance of 219 Fg−1 at 0.5 Ag−1; at 10 Ag−1, the mass-specific capacitance retains 81%, confirming its excellent rate performance; After 2000 cycles, the mass ratio capacitance retains 94%, and the cycle performance is excellent.

The tin oxide nanopowder is synthesized by hydrothermal method and the hydrothermal time effect on its phase structure, morphology and optical properties are studied. The results show that the samp...

The mechanisms behind the phase formation of SrxNbyO(x+5 y/2) perovskites in hydrothermal reactions are yet not well understood. In this work, we report on the one-pot hydrothermal synthesis of SrNb2O6, Sr2Nb2O7 and Sr5Nb4O15 layered perovskites in highly concentrated NaOH solutions. The mechanisms that govern the crystallization and the crystallite morphology of the synthesized perovskites are explained as a function of the NaOH concentration. The crystal structure, morphology, and optical properties of the obtained SrNb2O6, Sr2Nb2O7 and Sr5Nb4O15 perovskites were analyzed using XRD, EDS, HR-TEM, UV–vis absorption, diffuse reflectance spectroscopy (DRS), and Raman spectroscopy. The element composition and resultant crystalline phases are determined by using EDX and Rietveld refinement techniques, respectively. NaOH concentration is the main parameter for the control over the phase formation. High concentration of NaOH accelerates the hydrolysis rate for the transformation from Nb2O5 to Nb6O198− and finally to NbO67−. These polyanions favor the formation of the different crystalline phases, as high concentration of Nb6O198− the preferential formed phases are SrNb2O6, and Sr2Nb2O7, while high concentration of NbO67− induced the formation of Sr5Nb4O15 as a majority phase. The concentration of NaOH also plays a decisive role in the precipitation of SrNb2O6, Sr2Nb2O7 and Sr5Nb4O15 perovskites, high NaOH concentration promotes the Sr2+ complexation favoring the formation of Sr2+ rich phases.

To simplify the complicated synthetic techniques so that getting CuII-SSZ-13 zeolites with ideal structures and CuII cations distribution, and to interrogate CuII cations dynamics dependent NH3 mediated performance of selective catalytic reduction (NH3-SCR) of NO and hydrothermal stability, a microwave-assisted hydrothermal synthesis route was performed to prepare CuII exchanged SSZ-13 zeolite catalysts. The effects of synthetic temperature and time on the structure of SSZ-13 zeolite and NH3-SCR performance are clarified. The types and numbers of CuII species of fresh and hydrothermal aged samples were precisely explored. The NH3-SCR activity, N2 selectivity of fresh and aged CuII-SSZ-13 zeolites synthesized by different conditions are evaluated, respectively. Experimental characterizations demonstrate that the CuII-SSZ-13 zeolites can be synthesized with short crystallization time assisted with microwave treatment. The microwave synthesis temperature and time can affect the nucleation and growth process of SSZ-13 and thus resulting in SSZ-13 with different framework structures and various affinity to CuII ions. When the temperature and time are 175 °C and 9 h, the as-synthesized CuII-SSZ-13 sample shows a stable framework structure, large specific surface area, and more [Z2CuII] speciation. This sample also shows excellent catalytic activity and hydrothermal stability. Characterization results also show that the microwave treatment can strengthen the Al-O-Si bonds in the zeolite framework. Our work provides a facile strategy to synthesize CuII-SSZ-13 zeolite and atomic-level understanding of catalytic property and hydrothermal stability.

The thermal insulators with extraordinarily ultra-low dielectric constants (k

Vanadium dioxide (VO2) is an interesting compound that exists in different polymorphic phases with varying characteristics and potential applications. In this study, fabrication and property analyses of three VO2 polymorphs, namely VO2 (B), VO2 (A), and VO2 (M), are described. Specifically, VO2 (B) was prepared via hydrothermal method under a low synthesis temperature of 180 °C and a fast processing time of 24 h. In addition, VO2 (A) and VO2 (M) were derived from the as-synthesized VO2 (B) using sequential hydrothermal treatment and calcination process, respectively. From the field-emission scanning electron microscope (FESEM) scans, belt-like VO2 (B) nanoparticles with dimensions of as low as 35 × 130 nm2 were formed. Further, hydrothermal treatment of the as-synthesized VO2 (B) resulted to a flower-shaped VO2 (A) due possibly to an oriented attachment mechanism. Meanwhile, annealing of the VO2 (B) sample caused granular growth that produced plate-like and oblate shaped VO2 (M) with dimensions of 135 to 306 nm in diameter and 28 to 37 nm in thickness. Moreover, the thermochromic properties of the samples were examined using differential scanning calorimetry (DSC) while the thermophysical properties of the samples were measured via microflash method. Accordingly, the prepared VO2 (A) and VO2 (M) samples exhibited phase transition behavior at 168.37 °C and 68.6 °C, respectively. Subsequently, changes in the thermophysical properties of each sample can be observed across the measured transition temperature. In particular, an increase in both the thermal diffusivity and thermal conductivity of VO2 (M) can be observed when the temperature was raised from 50 °C to 100 °C. On the other hand, there is a noticeable decrease in the thermal conductivity of VO2 (A) when the temperature was increased from 150 °C to 200 °C.

In this work, we have synthesised a mixture consisting of sodium calcium silicate and calcium silicate nanostructures in the presence and absence of the hydrothermal method. The synthesised products were identified utilising many techniques such as XRD, EDS, FT-IR, HR-TEM, and FE-SEM. The XRD demonstrated that the mean crystallite size of the product, which was synthesised in the absence of the hydrothermal method, is 72.71 nm. The average crystallite size of the products, which were synthesised using the hydrothermal method at 160℃ for 4, 8, and 16 h, are 44.85, 34.89, and 37.38 nm, respectively. HR-TEM confirmed that all the products consist of irregular and rod shapes. The product, which was synthesised after 8 h of hydrothermal treatment, was operated as an adsorbent for the efficient removal of toxic ions (Cd(II) and Hg(II)) from aqueous media. The maximum adsorption capacity of the adsorbent towards Hg(II) and Cd(II) ions are 177.94 and 199.20 mg/g, respectively. The removal process of the studied ions was fitted well with the pseudo-second-order kinetic model and Langmuir equilibrium isotherm. Thermodynamic parameters confirmed that the removal process of the studied ions was spontaneous, chemical, and endothermic.

In order to compare the effect of preparation method on the catalytic performance over Ni/3D-SBA-15 catalyst for CO2 methanation, one-pot and two-pot synthesis strategies were used in this work. 3D-SBA-15-derived Ni-phyllosilicate catalyst could be obtained via a two-pot hydrothermal synthesis using 3D-SBA-15 and nickel nitrate as precursors at 180 °C. This Ni-phyllosilicate catalyst with a monolithic macromorphology and a microcosmic appearance of 3D-networked framework covered by nanosheets, was also achieved via a one-pot hydrothermal method with elimination of the preparation and pretreatment of 3D-SBA-15. The one-pot-synthesized Ni/S–O catalyst not only showed high catalytic activity due to the small-sized Ni particles, but also exhibited excellent anti-sintering property owing to the strong metal-support interaction derived from Ni-phyllosilicate. Compared with the two-pot synthesis, many advantages were observed for one-pot synthesis including monolithic appearance, high convenience, large Ni-phyllosilicate amount and low cost.

A facile “green chemistry” hydrothermal method of chitosan-Ag nanoparticles (NPs) synthesis has been proposed. Chitosans of different molecular weight (from 20 to 1200 kDa) have been used as reducing agents and particle stabilizers. The obtained chitosan–Ag nanocomposites have been studied by UV–Vis and IR spectroscopy, X-ray powder diffraction analysis, and transmission electron microscopy. Nanocomposites have a “core-shell” structure, spherical shape with size up to 60.0 nm and the surface ξ-potential value >40.0 mV. Optimal parameters of synthesis (time, temperature, molecular weight of chitosan) of chitosan–Ag nanoparticles with highest antimicrobial activity against gram-positive and gram-negative bacteria and fungi have been found.

MoS2/rGO composites were synthesized by hydrothermal method from the precursors of MoS2 and reduced graphene oxide (rGO) prepared in the former steps. The influence of the synthesis conditions including hydrothermal temperature and mass ratio of MoS2 to rGO on the structure, morphology, and optical absorption capacity of the MoS2/rGO composites was systematically investigated using physicochemical characterizations. The photocatalytic performance of as-prepared samples was investigated on the degradation of Rhodamine B under visible light, in which, the composites obtained at hydrothermal temperature of 180°C and MoS2/rGO mass ratio of 4/1 exhibited the highest photodegradation efficiency of approx. 80% after 4 hours of reaction. This enhancement in photocatalytic behaviour of composites could be assigned to the positive effect of rGO in life time expansion of photoinduced electrons—holes.

Sodium gadolinium molybdate (Na0.5Gd0.5MoO4) powder as a new photocatalyst was prepared using GdCl3·6H2O, H2NCSNH2 and Na2MoO4·2H2O as raw materials by hydrothermal approach. The as-synthesized products were characterized with XRD, FESEM, XPS, Raman, FTIR, BET surface area analysis, UV–Vis absorption spectra and PL spectroscopy, respectively. The photocatalytic performance of Na0.5Gd0.5MoO4 catalysts was assessed using the photocatalytic degradation of rhodamine B (RhB) at room temperature under visible light. The Na0.5Gd0.5MoO4 catalyst exhibited enhanced photoability as the Gd3+ ions increase. The excellent photocatalytic performance for photocatalysts arise from the separation and migration of the electron–holes pairs in the structure and the narrow band gap energies resulting in the visible absorption ability’s improvement. Additionally, the h+ was discovered to be the most significant reactive group for RhB photodegradation and the possible photocatalytic mechanism was also devised.

Active electrodes of transition metal selenides attract extensive consideration in energy storage application because of its improved electrochemical performances. In this study, evolution of flower like MnSe2@MoSe2 was subsequently synthesized through one pot hydrothermal route. Growth of combined composite exposed flowerlike morphology with looser corrugated nanospikes increases surface area for redox reaction which reduces ionic diffusion pathway and improves supercapacitor performance in three-cell configurations. The best performed (MMS-3) electrode exhibited 719 Fg−1 specific capacitance and retained 99.78% capacity retention over 2000 cycles. Furthermore, as an asymmetric MnSe2@MoSe2//AC device delivered significant 75 Whkg−1 energy density at 747 Wkg−1 power density. Besides, asymmetric (MMS-3)//AC device maintained 99.16% capacity retention after constant 2000 charge discharge cycles. In a small-scale practical demonstration, MnSe2@MoSe2//AC device illuminated red LED and displayed improved electrochemical performance. Hence, both Mn (manganese) and Mo (molybdenum) mutual role promotes more affluent redox chemistry, which is beneficial for higher electrochemical activity. Thereby, Se provided greater number of electroactive sites that can aid maximum utilization of electrolyte ions.

Potassic rocks are rapidly activated and converted to cancrinite (CAN) zeolites in NaOH solution via microwave-assisted hydrothermal (MH) method. The conditions of zeolization process via MH method are optimized, and the mechanism is illustrated. The phase transition process of potassic rocks is obtained as follows: decomposition of the potassic rocks→zeolite sodalite→zeolite CAN. In this process, the microwave exerts a reinforcement effect by generating the cleavage cracks on the surface of potassic rocks and accelerating the dissolution and crystallization processes. The synthesized zeolite CAN exhibits the maximum adsorption capacity of 6.5 mg g−1 for methylene blue. In addition, the filtrate is further used to prepare linda type A (LTA) zeolites by conventional hydrothermal synthesis method. The synthesized zeolite LTA presents the cubic morphology with rounded corners, and its Ca2+ ion exchange capacity could reach 335.6 mg CaCO3 g−1.

Engineering lattice defects in two-dimensional (2D) sulfide semiconductors has been accepted as an effective strategy to enhance the efficiency of the solar-to-fuels conversion. Although many researches have proven the lattice defect-mediated photocatalytic activity of ZnIn2S4, the artificial control of S-defects for optimizing the charge-carrier kinetics process in ZnIn2S4 has long been a challenging task. Herein, we report a facile one-step method to modulate the lattice S-content of ZnIn2S4 microflowers (MFs) only through adjusting the used amount of S-precursor in the hydrothermal solution that contains the metal precursors with a fixed Zn/In stoichiometric ratio at 1:2. We also demonstrated that the S-vacancies at the In facets were the main type of lattice defects in the formed ZnIn2S4 MFs, which could enhance both the separation and migration processes of the photoinduced charge-carriers due to the existence of discrete defect energy-levels (DELs) and the reduced effective mass of electrons, as evidenced by the first-principles calculations and the electron spectra analyses. The ZnIn2S4 MFs with the optimal content of S-vacancy obtained by a hydrothermal treatment of the precursors with the Zn/In/S stoichiometric ratio of 1:2:8 possessed the long-lived photoinduced electron (~94.64 ns) for contributing to the photo-physical and -chemical processes. Thus, upon visible light irradiation, the H2-evolution rate of this sample reached ~ 2.40 mmol h−1 g−1 with an apparent quantum efficiency of ~ 0.16% at 420 nm even though only using 5 mg of photocatalysts without any cocatalysts.

The metal-exchanged zeolites as catalysts have been widely applied in many catalytic reactions, but their syntheses are environmentally unfriendly due to the multiple steps such as ion-exchange for the formation of a large amount of wastes. Herein, we for the first time report a method for one-pot fabrication of metal-zeolite catalysts (M-SSZ-13, M-Beta, M-ZSM-5, and M-EU-1; M = Cu, Co, Ni) from a combination of solvent-free and sodium-free routes by mixing, grinding, and heating the raw materials of aluminosilicate gel, organic templates, and metal-amine complexes. As a typical example, Cu-SSZ-13 zeolite is successfully synthesized from heating the mixture of aluminosilicate gel, organic template, and Cu-amine complex. Catalytic tests in selective catalytic reduction of NOx with NH3 (NH3-SCR) show that the synthesized Cu-SSZ-13 zeolite before and after hydrothermal aging at 750 °C for 16 h are completely comparable with the commercial Cu-SSZ-13 zeolite from the conventional hydrothermal synthesis. Very interestingly, the method in this work has obvious advantages such as high yield, reduced pollutants, and simple process, which should be potentially important for practical applications of the metal-zeolites in the future.

Two new compounds, Cs2[Cu2Re6S8(CN)6]⋅3H2O (I) and (H3O)2[Cu{Cu2(µ-CN)}Re6Se8(CN)6]·6.5H2O (II), were synthesized under hydrothermal conditions from a mixture of CuCN and Cs2.67K1.33[Re6S8(CN)2(OH)4]·4H2O or Cs2.75K1.25[Re6Se8(CN)4(OH)2]·H2O, respectively. The reaction involves replacement of OH– by CN– and the formation of interpenetrating anionic framework through –CN–Cu–CN– bridges. The framework cavities accommodate counterions and water molecules. The obtained compounds were characterized by single crystal X-ray diffraction (CIF files CSD nos. 2048821 (I), 2048822 (II)), IR spectroscopy, and elemental analysis.

Hollow-structured Cu0.3Co2.7O4 microspheres have been synthesized by a simple one-pot template-free hydrothermal method with copper sulfate, cobalt acetate and ammonia as raw materials. The products were characterized by powder X-ray diffraction, energy dispersive X-ray analysis, selected area electron diffraction, high-resolution transmission electron microscopy, scanning electron microscopy and BET measurements. The research results show that the hollow Cu0.3Co2.7O4 microspheres consist of single-crystalline nanocubes with the diameter of about 20 nm. The formation mechanism of hollow Cu0.3Co2.7O4 microspheres is suggested as Ostwald ripening in a solid-solution-solid process, and Cu0.3Co2.7O4 microspheres are mesoporous containing two pore sizes of 3.3 and 5.9 nm. The as-prepared Cu0.3Co2.7O4 sensors have optimal gas responses to 50×10−6 mg/m3 C2H5OH at 190 °C.

The barium ferrite BaFe12O19 with c-plane anisotropy, which possessed relative high saturation magnetization and low coercivity, had been synthesized by hydrothermal method with different reaction time of 5 h, 8 h,11 h,14 h, and 17 h. The X-ray diffraction (XRD), field emission scanning electron microscope (FESEM) and vibrating sample magnetometer (VSM) were used to study the phase composition, microstructure and magnetic properties of barium ferrite, respectively. The results showed the intensities of the peak were enhanced and there was no impurity phase. With the prolonging of the reaction time to 11 h, 14 h and 17 h, the grain size increased, and the equivalent diameter was about 1 μm, and the thickness was about 100 nm. When the reaction time was 17 h，the coercivity of barium ferrite was 1104 Oe. The reduction of coercivity was ascribed to the increase of particle size and the reduction in magnetic anisotropy.

Two techniques using subcritical and supercritical water are introduced herein: supercritical hydrothermal synthesis of metal oxide nanoparticles and hydrothermal processing of waste and biomass. Recent progress of supercritical hydrothermal synthesis method is reviewed particularly for oxidation catalysts. Then hydrothermal treatment methods for biomass and waste are summarized from the viewpoint of phase behavior, homogeneous reaction, and reaction with catalysts. Fractionation of valuable materials through reforming of biomass and waste using the characteristic properties of the hydrothermal reaction field is emphasized. Cellulose and lignin, the major components of woody materials, and heavy oil as a representative waste material have been studied intensively for treatment under hydrothermal conditions. Process design aspects are discussed to provide a future scope of related technologies.

Our previous work reported a new strategy based on a P excess reaction system to hydrothermally synthesize lithium transition metal phosphates (LiMPO4), and herein the effect of P excess on the synthesis and property of LiMPO4 is investigated in detail by taking the multi-component LiMn0.8Fe0.19Mg0.01PO4 as a case. The results show that a proper degree of P excess is fairly profitable for hydrothermal synthesis including the effect on suppressing the occurrence of undesired Fe2+ oxidation during synthesis and improving the particle dispersion of hydrothermal product, and thus the obtained samples have enhanced electrochemical performance. These effects of P excess should be general and applicable to hydrothermal synthesis of other lithium transition metal phosphates.

Here, we have successfully synthesized single-phase ZnWO4 nanoparticles using a highly effective low-temperature ionic liquid-assisted hydrothermal method at 180 °C for 24 h. TEM images show that agglomerated, irregular-shaped nanoparticles and XRD confirm the monoclinic wolframite phase of ZnWO4 with P2/c space group. The main vibrational modes for ZnWO4 are observed in the IR region from 468 to 880 cm−1 and the optical absorption peaks at 280 nm. Also, photocatalytic degradation was carried out over suspensions of ZnWO4 against Indigo Carmine (IC) dye under UV light irradiation. The effects of various operational parameters were examined and we observed that the degradation efficiency was reached up to 90% within 120 min. Hence, ZnWO4 nanoparticles are proven to be good materials for photocatalytic dye degradation application and the future of the technology. We have successfully synthesized ZnWO4 nanoparticles via ionic liquid-assisted hydrothermal method. The obtained product shows excellent photocatalytic activity against Indigo Carmine (IC) dye solution.

Bimetallic chalcogenides, with several excellent properties, have been reported to be promising electrocatalysts for the hydrogen evolution reaction (HER) in the past few years. Hence, it is of great interest to develop more bimetallic chalcogenides in the relevant fields. Herein, Ag8SnS6 nanoparticles with different Ag/Sn ratios have been synthesized by adjusting the precursor molar ratio via a facile hydrothermal method, among which the sample obtained at SnBr2/AgNO3 = 1/6 exhibits the best performance for HER. After coupling with carbon nanotubes (CNTs), the catalytic performance of Ag8SnS6 nanoparticles can be improved significantly owing to the enhanced charge transport. The resultant Ag8SnS6 + CNT composite shows efficient electrocatalytic activity and good stability for HER in an acid solution. This study reveals the electrocatalytic performance of Ag8SnS6 nanoparticles in HER for the first time and provides a useful guide for the optimization of an HER electrocatalyst.

The present work deals with the synthesis and characterisation of a hybrid nanocomposite, WO3-doped KIT-6, encompassing mesoporous characteristics, using novel hydrothermal practice with great hum...

Fluorescent nanostructures based on carbon, or carbon dots, are attracting much attention and interest because of their diverse properties which can be applied in several fields of knowledge, such as optics, biomedicine, environmental research, among others. Such properties are in part, derived from its intrinsic luminescence from tunable functional groups. In this work, we produced carbon nanodots (CND) using agro-industrial residues, such as Lolium perenne and malt bagasse. The methods used were conventional hydrothermal syntheses and microwave-assisted hydrothermal synthesis. To the best of our knowledge, this is the first time that carbon dots synthesized from this ryegrass type are reported. The synthesis methods were one step (no catalyst, base, or acid were added for passivation), and the functional groups responsible for the luminescence and high solubility in water were identified by infrared spectroscopy, being mainly C=O, C–OH, C–N, and N–H. According to our theoretical studies, the C=O group introduced a new energy level for electronic transitions that can affect the emission properties. Fluorescence images of osteoblasts using CNDs were acquired and their chelating property towards Pb2+ and Cr6+ detection was tested.