Low-temperature Hydrothermal Reaction Research Articles

Topotactic Syntopogenous Sodium Vanadium Fluoride for High-Performance Sodium-Ion Batteries: Electron and Sodium-Ion Reservoirs in Perovskite/Diperovskite Superlattice.

In order to simultaneously accelerate ion and electron transfer in sodium-ion battery (SIB) cathodes, a topotactic superlattice was utilized, in which the atomically intrinsic lattice-matching effect from inner to external surface can boost the charge transfer due to the disappearance of the heterojunction interface. Herein, a topotactic syntopogenous Na3VF6/NaVF3 superlattice formulated as Na2.9V1.1F6 (NVF) was synthesized by a facile one-step low-temperature hydrothermal reaction. NVF nanoparticles show an excellent Na+ storage capacity (∼205 mAh g-1) in a high voltage window up to 4.2 V with ultralong cycling stability. That is associated with the mixed occupancy of V and Na in NVF. The multivalent V centers serve as electron reservoirs to inhibit phase transformation, and the Na-enriched Na3VF6 with better electron conductivity acts as a Na+ reservoir for effective electron transfer. Highly reversible (de)intercalation of Na+ is achieved in the channel of perovskite-type NaVF3 with structural integrity.

In Situ Self-Assembly of Nitrogen-Doped 3D Flower-like Hierarchical Porous Carbon and Its Application for Supercapacitors.

The hierarchical porous carbon-based materials derived from biomass are beneficial for the enhancement of electrochemical performances in supercapacitors. Herein, we report the fabrication of nitrogen-doped 3D flower-like hierarchical porous carbon (NPC) assembled by nanosheets using a mixture of urea, ZnCl2, and starch via a low-temperature hydrothermal reaction and high-temperature carbonization process. As a consequence, the optimized mass ratio for the mixture is 2:2:2 and the temperature is 700 °C. The NPC structures are capable of electron transport and ion diffusion owing to their high specific surface area (1498.4 m2 g-1) and rich heteroatoms. Thereby, the resultant NPC electrodes display excellent capacitive performance, with a high specific capacitance of 249.7 F g-1 at 1.0 A g-1 and good cycling stability. Remarkably, this implies a superior energy density of 42.98 Wh kg-1 with a power density of 7500 W kg-1 in organic electrolyte for the symmetrical supercapacitor. This result verifies the good performance of as-synthesized carbon materials in capacitive energy storage applications, which is inseparable from the hierarchical porous features of the materials.

Electron transfer and microbial mechanism of synergistic degradation of lignocellulose by hydrochar and aerobic fermentation

In response to the problem of asynchronous fermentation between lignocellulose and perishable materials in compost, the combined technology of low-temperature hydrochar and compost has been studied. Hydrochar was prepared through low-temperature hydrothermal reactions and applied to aerobic fermentation. The response relationship between lignocellulose content, electron transfer capability, and microbes was explored. The results showed that a pore structure with oxygen-containing functional groups was formed in hydrochar, promoting electron transfer during composting. With the rapid increase in composting temperature, the lignocellulose content decreased by 64.36 mg/g. Oceanobacillus, Cerasibacillus, Marinimicrobium, and Gracilibacillus promoted the degradation of lignocellulose and the carbon/nitrogen cycle during aerobic fermentation, and there was a significant response relationship between electron transfer capability and functional microbes. The combined application of hydrochar and aerobic fermentation accelerated the degradation of lignocellulose. This study provides technical support for the treatment of heterogeneous organic waste.

MnO2-modified soybean root derived porous carbon with excellent capacity deionization

Developing high-efficient capacitive deionization (CDI) systems with low-cost environmentally friendly electrode materials is one of the most effective ways to address freshwater shortage. Meanwhile, large number of soybean roots are discarded as waste with large production of soybean and contribute to enormous pressure on the environment. In this work, soybean roots are adopted to prepare activate carbon (SRKPC) by a carbonization and KOH activation process. A composite of [email protected]2 with MnO2 nanoparticles supported on SRKPC is synthesized by a low temperature hydrothermal reaction, which exhibits excellent electrochemical properties with high specific capacitance (597.9 F g−1 at 2 mV s−1) and bimode sodium storage characteristics. The dual-mode CDI system based on [email protected]2 delivers an effective desalination performance with a desalination capacity of 42.90 mg g−1, a desalination rate of 2.86 mg g−1 min−1 and relatively good desalination recoverability. Therefore, this work not only exemplifies the simple fabrication of low-cost, environmentally friendly, and efficient dual-mode CDI electrode materials for capacitive desalination, but also provides a sustainable way to turn biomass waste into functional materials.

Vertically aligned nickel-iron-phosphide nanosheets on three-dimensional porous nickel foam for overall water splitting

A low-cost, earth-abundant and efficient bifunctional electrocatalysts for overall electrochemical water splitting is an important development in the field of electrochemistry. In this work, nickel-iron phosphide (NiFeP) nanosheets on three-dimensional (3D) porous interconnected nickel foam with rich active sites are processed by two-step synthesis. Conversion of nickel foam to nickel iron layered double hydroxide (NiFeLDH) by low-temperature hydrothermal reaction followed by thermal phosphidation using red phosphorus as the source. The thermal phosphidation process is optimized with respect to temperature and duration. The electrochemical performances of the electrocatalyst are strongly depends on the phosphidation temperature and duration. The NiFeP (NFP) electrocatalyst synthesized at 500 °C for 30 mins (NFP500–30) shows the overall water splitting voltage of 1.69 V at 50 mA/cm2 in 1.0 M KOH. The improvement in electrocatalyst performance is attributed to the Fe substitution, vertically aligned nanostructure surface with abundant active sites and 3D porous interconnect network structure. The electrocatalyst exhibits robust durability with high conductivity and excellent corrosion resistance.

Photocatalytic degradation of TiO2 via incorporating Ti3C2 MXene for methylene blue removal from water

The photocatalytic degradation of TiO2 as the best method to solve the pollution of dye wastewater has been widely studied. However, the photocatalytic degradation efficiency of TiO2 needs to be further improved even though much effort has been paid, especially under visible (Vis) light. TiO2/MXene composites were synthesized by low temperature hydrothermal reaction using TiO2 (P25) and MXene nanosheets as raw materials for the degradation of methylene blue (MB) dye. The removal rate of MB was effectively improved by the combination of TiO2 with MXene materials. The best removal efficiency was achieved at a mass ratio (4:1) of TiO2 to MXene. The removal rate of TiO2/MXene composite materials for MB under ultraviolet light was 96.44%, which was 29.83% higher than that of pure TiO2. Under Vis light, the removal rate of MB was 8.26 times higher (40.19%) than that of pure TiO2. In addition, the degradation process of MB dye was significantly promoted under both external and visible light. Therefore, the utilization efficiency of Vis light was greatly improved, and the degradation process of MB dye was promoted. The enhancement of removal efficiency was attributed to the enhanced charge anti-recombination and high adsorption capability toward MB. This work successfully improved the rate of dye removal of TiO2 by incorporating MXene nanosheets, heralding the exciting prospects of TiO2/MXene composites in dye wastewater treatment.

The effect of high-temperature alteration of oceanic crust on the potassium isotopic composition of seawater

High-temperature hydrothermal alteration of oceanic crust is one of the two main sources of potassium (K) to the oceans, with modern flux estimates ranging roughly from ∼8 to 30 % of the K flux from rivers. Despite the role of high-temperature hydrothermal fluids in the global seawater K budget, little is known about its effect on the K isotopic composition of the oceans. Here we present stable K isotope measurements (δ41KSRM3141a) of globally distributed high-temperature hydrothermal fluids from three mid-ocean ridge systems: the East Pacific Rise (n = 21), the Juan de Fuca Ridge (n = 34), and the Mid-Atlantic Ridge (n = 18). We find a strong correlation between δ41K and Mg/K ratios, consistent with conservative mixing between a high-temperature hydrothermal fluid (i.e., Mg = 0) and seawater as fluids ascend to the seafloor and/or due to seawater entrainment during sampling. The δ41K of end-member hydrothermal fluids is found to range between −0.80 ‰ and 0.07 ‰, with an average value of −0.36 ± 0.30 ‰ (2σ, n = 38). Most (∼76 %) of the variability in end-member fluid δ41K compositions observed here can be explained by high-temperature fluid-rock K exchange, with little (∼0.2 ‰) to no K isotope fractionation between hydrothermal fluid and altered crust. Larger deviations from the average end-member hydrothermal fluid value are likely to result from processes other than high-temperature fluid-rock exchange, such as (1) low-temperature hydrothermal reactions during fluid recharge, (2) reaction of fluids with local sedimentary sources, and (3) phase separation. The K contents of end-member fluids vary considerably, from ∼1 to 38 mM, thus a K-weighted average of −0.37 ± 0.24 ‰ (2σ, n = 38) is estimated to represent the δ41K composition of the global hydrothermal K flux. Our results suggest that K sourced from axial hydrothermal alteration does not contribute to the elevated 41K/39K of seawater compared to bulk silicate Earth (BSE). In addition, subduction of oceanic crust altered under high-temperature conditions is unlikely to be a significant source of K isotopic heterogeneity to Earth’s mantle.

Direct deposition of anatase TiO2 on thermally unstable gold nanobipyramid: Morphology-conserved plasmonic nanohybrid for combinational photothermal and photocatalytic cancer therapy

Deposition of crystalline titanium dioxide (TiO2) on gold nanostructures has been considered as a promising strategy for near-infrared (NIR) light-activated photocatalysis. A typical route comprises pre-deposition of amorphous TiO2 on the gold surface and its ensuing crystallization by high-temperature annealing. Such condition, however, is not compatible with highly plasmonic but thermally unstable sharp-tipped gold nanostructures, causing structural disruption and plasmonic decline. Herein, we report a hybridization method excluding high-temperature annealing, i.e., direct deposition of anatase TiO2 onto sharp-tipped gold nanobipyramid (Au NBP/a-TiO2) with conserving their morphology without agglomeration via low-temperature hydrothermal reaction. In addition to keeping the plasmonic photothermal performance, Au NBP/a-TiO2 exhibits enhanced photocatalytic generation of reactive oxygen species in response to the NIR excitation, evidencing the efficient injection of hot electrons from the Au NBP to the anatase shell. In vitro and in vivo studies revealed that the efficient photocatalytic/photothermal responses of Au NBP/a-TiO2, along with dispersion stability in biological media and minimal toxicity, hold potential for synergistic photothermal and photodynamic therapy. We believe that the low-temperature synthetic method introduced here might offer a general way of crystalline deposition of TiO2 on a variety of gold nanostructures, broadening the spectrum of NIR-responsive photocatalytic hybrid nanostructures for biomedical applications.

Multi-slice Ni-doped brochantite modified and polymer crosslinked cellulose paper with high wet stability and oil repellency for water disposal

Cellulose paper (CP) is an environmentally-friendly and low-cost material, but its application in petrochemical water disposal is limited by poor wet stability and oil repellency. In this work, based on the crosslinking and low-temperature hydrothermal reaction, we report a novel CP material which is crosslinked by polyethyleneimine (PEI)-glutaraldehyde (GA)-cellulose and modified by Ni-doped brochantite crosslinked CP (NB-PCCP) for the removal of emulsified oils and dyes in wastewater. The crosslinking process enhances the wet strength of CP, and the formation of the multi-slice structure of Ni-doped brochantite on PCCP surface improves the oil repellency. Results show that NB-PCCP possesses outstanding oil-in-water emulsion separation performance with high oil rejection of 99.9%, the Young's modulus of NB-PCCP is quadruple that of untreated CP in wet conditions, indicating improved wet stability in practice application. NB-PCCP also displays excellent removal performance for dyes due to the existence of high-density hydroxyl radicals, as well as excellent acid/alkali resistance. The research on CP provides significant guidance for the design of cellulose-based material with multi-slice structure as well as high wet strength and oil repellency for the purification of wastewater.

Electrochemical Characteristics of Synthesized Nb 2 O 5 -Li 3 VO 4 Composites as Li Storage Materials

The increasing demand for energy storage in mobile electronic devices and electric vehicles has emphasized the importance of electrochemical energy storage devices such as Li-ion batteries (LIBs) and supercapacitors. For reversible Li storage, alternative anode materials are actively being developed. In this study, we designed and fabricated an Nb2O5-Li3VO4 composite for use as an anode material in LIBs and hybrid supercapacitors. Nb2O5 powders were dissolved into a solution and the precursors were precipitated onto Li3VO4 through a simple, low-temperature hydrothermal reaction. The annealing process yielded an Nb2O5-Li3VO4 composite that was characterized by X-ray diffraction, electron microscopy, and X-ray photoelectron spectroscopy. Electrochemical tests revealed that the Nb2O5-Li3VO4 composite electrode demonstrated increased capacities of approximately 350 and 140 mAh g-1 at 0.1 and 5 C, respectively, were maintained up to 1000 cycles. The reversible capacity and rate capability of the composite electrode were enhanced compared to those of pure Nb2O5-based electrodes. These results can be attributed to the microstructure design of the synthesized composite material.

Low Temperature Hydrothermal Synthesis of Biochar from Green Algae and Its Combustion Performance

The low temperature hydrothermal carbonization reaction of green algae was studied by combining with the low temperature hydrothermal carbonization technology. The hydrothermal carbon was prepared in the temperature range of 180?C - 240?C. The experimental results had been characterized in detail by oxygen bomb calorimeter, synchronous thermal analyzer and infrared spectrum analysis. The effects of reaction time, reaction temperature and salt concentration on hydrothermal carbonization and combustion were analyzed by studying the experimental conditions under the optimal calorific value. Results showed that algal carbonized, diversity and continental wooden biomass combustion process, and algae in the low temperature hydrothermal carbonization reaction of calorific value significantly increase, and comprehensive consideration of low temperature hydrothermal carbonization algae biomass to improve its calorific value is the best solution to time, salt concentration control in 8 - 10 h, around 0.05%, the reaction temperature is slightly greater than 240?C. It provides a reference for the further research in the field of clean biomass and is of great significance for the development of algal biomass combustion function.

Hydrothermal Synthesis and Crystal Structure of a (Ba0.54K0.46)4Bi4O12 Double-Perovskite Superconductor with Onset of the Transition Tc ∼ 30 K

A new superconducting double perovskite was successfully synthesized by a low-temperature hydrothermal reaction at 240 °C. The crystal structure refinement of this double perovskite was done by single-crystal X-ray diffraction, and it had a cubic unit cell of a = 8.5207(2) Å with space group Im3̅m (No. 229). This superconducting double-perovskite chemical composition was estimated by electron probe microanalysis and was similar to the refined data. The superconducting transition temperature of the double perovskite was ∼30 K; the electrical resistivity began to fall at ∼25 K, and zero resistivity occurred below 7 K. Moreover, temperature-dependent resistivity under various magnetic fields and isothermal magnetization measurements ensured the nature of a type II superconductor for the sample. Finally, the metallic nature of the material was investigated by a first-principles study.

Synthesis, crystal structure and physicochemical properties of organic-inorganic compounds KCS-3 and KCS-4

Abstract Organic-inorganic hybrid aluminosilicate compounds KCS-3 and KCS-4 were successfully synthesized by low-temperature hydrothermal reaction of mother gels composed of organically-bridged silane, fumed alumina, alkali metal hydroxide and water. Two bridged organosilanes i.e. 4,4′-bis(triethoxysilyl)-1,1′-biphenyl (BTEbP) and 1,4-bis(triethoxysilyl)benzene (BTEB) were used as a Si source for the synthesis of KCS-3 and KCS-4, respectively. The presence of T3 (≡O3Si–R, R: organic group) local structure, AlO4 tetrahedral unit and the organic groups originating from the employed organosilane were confirmed by 29Si, 27Al and 13C MAS NMR measurements. Their crystal structures were solved by the direct space method using the parallel tempering algorithm from powder X-ray diffraction data. The crystal structure of KCS-3 belongs to tetragonal symmetry (lattice constants: a = 10.22 A and c = 71.37 A, space group: I41/amd). Four aluminosilicate layers composed of 4-ring and 8-ring were stacked along c-axis, and adjacent layers were connected alternately by a biphenyl pillar (–C6H4–C6H4–) and a Q2 Si pillar (–OSi(OH)2O–). KCS-3 showed amphiphilic adsorption properties, reflecting the presence of hydrophilic- and lipophilic-inner spaces. On the other hand, the crystal structure of KCS-4 belongs to monoclinic symmetry (lattice constants: a = 10.05 A, b = 9.349 A, c = 5.052 A and β = 97.01°, space group: P21/c). A large amount of Li ions forming four-coordination environment is included in a layer-like framework, and adjacent layers were bridged by a phenylene group, that is, KCS-4 can be regarded as a hybrid-type lithosilicate.

A novel in situ hydrothermal preparation route for Sb2S3 and its solar cell application

In this study, we reported a novel in situ hydrothermal approach for fabricating Sb2S3 films. Metal Sb films were first deposited on substrates using room-temperature radio frequency magnetron sputtering and then undergo an in situ transformation to Sb2S3 films through a novel low-temperature hydrothermal reaction. Characteristics of the obtained Sb2S3 films prepared by our method were investigated. Planar Sb2S3 solar cells utilizing in situ fabricated Sb2S3 film as absorber has also been fabricated and yielded a power conversion efficiency of 1.32%.

Formation of Fe(III)–oxides on the magnetite surfaces in the low–temperature hydrothermal reaction

Formation of Fe(III)–oxides on the magnetite surfaces in the low–temperature hydrothermal reaction

Facile synthesize VO2 (M1) nanorods for a low-cost infrared photodetector application

Infrared photodetector is an important technology for both civilian and military applications. However, conventional commercial detectors generally require complex designs, expensive devices and cumbersome procedures. In this work, monoclinic phase VO2 (M1) nanorods (NRs) with metal-insulator transition properties were synthesized through a low-temperature hydrothermal reaction and subsequent annealing. The evolution of vibrational modes of VO2 (M1) NRs have been observed using Raman and IR spectroscopies during the structural phase transition. In addition, a high-sensitivity infrared photodetector based on a network of the VO2 (M1) NRs was fabricated with a low-cost method, and the electron transfer processes in nanorod (NR) networks has been discussed. The device exhibited high photosensitivity, excellent stability, and reproducibility in atmospheric condition at room temperature.

Hydrothermal Preparation, Crystal Chemistry, and Redox Properties of Iron Muscovite Clay.

The development of functional materials based on Earth-abundant, environmentally benign compositions is critical for ensuring their commercial viability and sustainable production. Here we present an investigation into the crystal chemistry and electrochemical properties of the muscovite clay KFe2.75Si3.25O10(OH)2. We first report a low-temperature hydrothermal reaction that allows for a significant degree of control over sample crystallinity, particle morphology, and cation distribution through the lattice. A complex sequence of stacking faults is identified and characterized using a combination of Mössbauer spectroscopy and total scattering neutron experiments. We then show the existence of a reversible electrochemical process using galvanostatic cycling with complementary cyclic voltammetry suggesting that the redox activity occurs primarily on the surface of the particles. We conclude by determining that the ability to (de)intercalate Li ions from the material is hindered by the strong negative charge on the transition metal silicate layers, which prevents the displacement of the interlayer K ions. This work calls attention to a hugely Earth-abundant family of minerals that possesses useful electrochemical properties that warrant further exploration.

New optimized method for low-temperature hydrothermal production of porous ceramics using diatomaceous earth

Abstract The aim of this study was to test the diatomaceous earth from a deposit near Rožden Village (Macedonia) as a raw material for low temperature hydrothermal production of porous ceramics. Hydrothermal synthesis of porous ceramics has been carried out under saturated steam pressure at 130 °C for a period of 1, 2 and 3 h. The objective of this work was to investigate the impact of slaked lime, autoclave curing time, autoclaving temperature and compaction pressure on the compressive strength and porosity of the products. During the hydrothermal synthesis, newly obtained calcium silicate hydrate dominates which give positive effect to the compressive strength and product porosity confirmed by X-ray powder diffraction. Moreover, a calcite was also evidenced by FTIR spectroscopy whose presence additionally increases the compressive strength of the hydrothermal products. The products obtained during the low-temperature hydrothermal reaction are classified as light porous ceramics with bulk density ranging from 0.71 to 0.91 g/cm 3 and compressive strength within 14.7–19.4 MPa.

Hydrothermal Synthesis, Crystal Structure, and Visible-Region Photocatalytic Activity of BaBi2 O6

The pentavalent bismuthate BaBi2O6 was prepared by a low-temperature hydrothermal reaction using NaBiO3.nH2O and Ba(OH)2.8H2O as starting materials. The X-ray powder diffraction pattern was indexed with a hexagonal cell (space group: P-31 m), the same as a PbSb2O6-type crystal. The crystal structure of this compound was refined using synchrotron X-ray powder diffraction data. The cell parameters were found to be a=5.57534(6) and c=5.7381(1) Å and the final reliability (R) factors obtained by Rietveld analysis were Rwp=5.15 % and Rp=3.62 %. This compound exhibited profound photocatalytic activity for phenol decomposition under visible light irradiation.

Memory properties of Au nanoparticles prepared by tuning HAuCl4 concentration using low-temperature hydrothermal reaction

An organic memory device with embedded gold nanoparticles (AuNPs) as charge storage elements and polymethylsilsesquioxane (PMSSQ) as organic dielectric layer was fabricated in this work. The AuNPs were prepared using sacrificial hydrothermal reaction on Al template, and the effect of HAuCl4 on size of AuNPs was studied. Field-emission scanning electron microscopy confirmed the increase of particle size with the increase in HAuCl4 concentration. X-ray diffraction analysis confirmed the formation of AuNPs with face-centered cubic (FCC) structure. The electrical properties of the memory system were investigated using a semiconductor characterization system. Current–voltage analysis confirmed the nonvolatile electrical bistability behavior and charge transport mechanism. Capacitance–voltage measurement indicated a memory behavior with flatband voltage shift because the AuNPs trapped and stored charges in the device. The optimal memory properties of AuNPs embedded in PMSSQ were obtained for FCC-structured AuNPs grown in 0.010M HAuCl4, with a mixture of 82±5nm (area density, 1.3×1012m−2) and 42±7nm (area density, 2.7×1012m−2) grain sizes that produced the lowest switch ON voltage of 2.2V and highest flatband voltage of 2.6V.