Hydrothermal Synthesis Research Articles

Interface Engineering of Flower-like Co 2 P/WO 3-x /Carbon Cloth Catalysts with Oxygen Vacancies for Efficient Oxygen Evolution Reaction.

The Constructing an efficient and low-cost oxygen evolution reaction (OER) electrocatalyst is critical for improving the performance of electrolysis in alkaline water. In this study, a self-supported electrocatalyst of flower-like cobalt phosphide and tungsten oxide (Co2P/WO3-x/CC) was prepared on carbon cloth (CC)surface by hydrothermal reaction with solution immersion etching and phosphorization annealing under H2/Ar atmosphere. This strategy can generate oxygen vacancies (OV), improving the speed of charge transfer between cobalt phosphide (Co2P) and tungsten oxide (WO3-x) components. The catalyst greatly increases the electrochemical active surface area, which is beneficial for efficient oxygen evolution. Electrochemical testing studies show that in 1.0 M KOH solution, Co2P-WO3-x/CC catalyst exhibits good OER activity, with a low overpotential of 254 mV at 10 mA cm-2, a small Tafel slope of 58.32 mV dec-1. The synergistic effect of oxygen vacancies and Co2P with WO3-xcan regulate electronic structures, expose more active sites, and cooperatively enhancing the OER activity. This study provides a workable strategy for preparing efficient non-noble metal OER electrocatalysts on engineered interfaces and OV.

Hierarchical MoO2@MoS2 heterojunction nanosheets anchored with metal-organic framework-derived CoFe alloy as bifunctional catalysts for flexible zinc-air batteries

Crafting a robust, high-performance, non-precious metal-based flexible air electrode is crucial for realizing flexible zinc-air batteries (ZABs). Herein, hierarchical MoO2 and MoS2 heterojunction nanosheets grown on carbon cloth (CC) are prepared through a simple hydrothermal reaction followed by calcination. Afterward, through self-assembly and high-temperature carbonization of zeolitic imidazolate framework-67 (ZIF-67) and Materials of Institute Lavoisier-101 (MIL-101) on the heterojunction nanosheets, a hierarchical structure of nitrogen-doped carbon (NC) encapsulated CoFe alloy nanoparticles (NPs) supported on MoO2@MoS2 heterojunction nanosheets (CC/MoS2@MoO2@CoFe) is obtained. It exhibits remarkable activity and durability for both bifunctional oxygen evolution and reduction reactions (OER/ORR), attributed to the ternary heterojunction formed by NC-coated CoFe alloy NPs uniformly dispersed among the MoO2@MoS2 nanosheets, along with oxygen vacancies at heterogeneous interfaces between MoS2, MoO2, and Co0.72Fe0.28 alloy. As a binder-less self-supporting electrode, the assembled aqueous ZAB demonstrates a maximum power density of 113.6 mW cm–2, surpassing that of Pt/C + RuO2 (75.2 mW cm–2), along with excellent cycling stability. Furthermore, the CC/MoS2@MoO2@CoFe-based flexible ZABs achieve a maximum power density of 54.1 mW cm–2, exhibit good cycling stability for up to 120 cycles, and show outstanding flexibility. This study paves the way for the practical integration of flexible ZABs into wearable electronic devices, heralding a new era of portable power solutions.

Tailoring anisotropic ZnO/wood-structural holocellulose hybrids for dye degradation through controlled nanoinsertion

Nanostructured inorganic/wood-structural holocellulose hybrids offer new potential applications, including mechanical energy conversion, superhydrophobic materials, gas adsorption and so on. Owing to the anisotropy of wood, controlling the morphology of mineral particles inside porous holocellulose scaffold is still far from satisfactory. In this work, a homogeneous zinc oxide (ZnO) decoration inside wood-structural holocellulose scaffold was achieved while the morphology, distribution and content of ZnO micro-nano particles were controllable through changing the conditions of hydrothermal growth. The holocellulose scaffold was prepared through delignification and periodate oxidation, which is favorable for Zn2+ capture and ZnO nuclei formation because of the surface charge increased. The controlled ZnO insertion was realized by changing metal salt concentration, temperature and hydrothermal time. The obtained multilayer ZnO could provide multiple light refractions and reflections and enhance the utilization of light. Consequently, with a minor ZnO loading (15 wt%), the ZnO/wood-structural hybrids could totally degrade methyl orange and methyl blue in 6 h. This novel and scalable synthesis method shows potential for both the design and photocatalytic activity of holocellulose hybrids.

Magnetic CuFe2O4 Spinel-Polypyrrole Pseudocapacitive Composites for Energy Storage.

This investigation focused on the fabrication of ceramic ferrimagnetic CuFe2O4-conductive polypyrrole (PPy) composites for energy storage. CuFe2O4 with a crystal size of 20-30 nm and saturation magnetization of 31.4 emu g-1 was prepared by hydrothermal synthesis, and PPy was prepared by chemical polymerization. High-active-mass composite electrodes were fabricated for energy storage in supercapacitors for operation in a sodium sulfate electrolyte. The addition of PPy to CuFe2O4 resulted in a decrease in charge transfer resistance and an increase in capacitance in the range from 1.20 F cm-2 (31 F g-1) to 4.52 F cm-2 (117.4 F g-1) at a 1 mV s-1 sweep rate and from 1.17 F cm-2 (29.9 F g-1) to 4.60 F cm-2 (120.1 F g-1) at a 3 mA cm-2 current density. The composites showed higher capacitance than other magnetic ceramic composites of the same mass containing PPy in the same potential range and exhibited improved cyclic stability. The magnetic behavior of the composites was influenced by the magnetic properties of ferrimagnetic CuFe2O4 and paramagnetic PPy. The composites showed a valuable combination of capacitive and magnetic properties and enriched materials science of magnetic supercapacitors for novel applications based on magnetoelectric and magnetocapacitive properties.

MoS2/N-doped hollow carbon foam for thermal insulation and broadband electromagnetic wave absorption

In this study, we demonstrated the synthesis of MoS2/N-doped hollow carbon foam (MoS2/NCF) for high performance of electromagnetic wave absorption (EMA), through high-temperature pyrolysis melamine foam and hydrothermal reaction. By adjusting the electromagnetic parameters of N-doped hollow carbon foam (NCF) through MoS2 nanosheets, the effective absorption bandwidth of MoS2/NCF reached 9.62 GHz at the matching thickness was 2.3 mm. Radar cross section (RCS) simulation results demonstrated that MoS2/NCF exhibited a strong reduction ability of RCS. At room temperature, the composite MoS2/NCF could block radiation temperature of around 110 ℃ in the case of a thickness of only 7 mm and a heating plate at 200 ℃. Moreover MoS2/NCF exhibited thermal stability and a certain flame retardants ability. The result indicated that the composite MoS2/NCF was beneficial for its application in the fields of thermal insulation and electromagnetic wave absorption.

Seed-Assisted Hydrothermal Synthesis of Monodispersed Au@C Core–Shell Nanostructures for Enhancing Thermal Diffusivity of Water-Based Nanofluids

Au@C core–shell nanostructures (Au@C-NS) were synthesized through a low-temperature seed-assisted hydrothermal approach using glucose as carbon source. The material characterization and chemical analysis confirm that the synthesis method allows to obtain uniform core–shell nanostructures constituted by a crystalline metal core and an amorphous carbon shell. Depending on the synthesis conditions, their average size ranges from 146 nm to 342 nm with relative standard deviation as low as 7 %. It is proposed that the characteristic monodispersity results due to a high nucleation rate of the carbon phase at the liquid–solid interface. The obtained monodisperse Au@C-NS were used to prepare water-based nanofluids with superior heat transport properties. The thermal lens analysis shows that the thermal diffusivity of Au@C nanofluids is 9.5 % and 31.3 % higher than their Au nanofluids counterparts and pure water, respectively, at particle concentration of 285 × 1011 ml−1. Phonon-related interactions at the metal cores and carbon shells interfaces are proposed as the heat transport mechanism behind the thermal diffusivity enhancement of the Au@C water-based nanofluids.

Levulinic Acid Production from Artichoke Leaves (Cynara Scolymus L.) by Catalytic Hydrothermal Reaction

In addition to examining the highest yield production of Levulinic acid (LA) from artichoke leaves by the subcritical catalytic hydrothermal decomposition, the studies were carried out on also increasing the production yields of 5-Hydroxymethylfurfural (HMF), Acetic and Formic acid from this biomass. In order to obtain the most suitable reaction conditions, the effect of different reaction conditions, including different temperature, reaction time, pH and catalyst types, on the decomposition of artichoke leaves and product yields were investigated. The subcritical thermal decomposition studies of artichoke leaves were carried out in an autoclave system at temperatures (120°C, 140°C, 160°C, and 180°C) for reaction times of 10, 20, 30, 40, and 50 min in the presence of H2SO4, HNO3, and HCL catalysts with different pH values; these reactions were realized also without adding a catalyst. As a result of the detailed research, it was seen that the most suitable experimental conditions for the production of LA with the highest yield from artichoke leaves could be achieved by adding sulfuric acid with a pH of 0.5 at a reaction temperature of 180°C and a reaction time of 50 min. The investigations were continued till achieving the highest product yields. After carrying out the experiments stated above, the optimal yields of the products produced from the artichoke biomass by the reactions were found as 209.39 g/kg biomass for LA, 117.40 g/kg biomass for formic acid, 72.27 g/kg biomass for acetic acid, and 39.04 g/kg biomass for 5-HMF.

Enabling Interfacial Lattice Matching by Selective Epitaxial Growth of CuS Crystals on Bi2WO6 Nanosheets for Efficient CO2 Photoreduction into Solar Fuels.

Photocatalytic CO2 reduction serves as an important technology for value-added solar fuel production; however, it is generally limited by interfacial charge transport. To address this limitation, a two-dimensional/two-dimensional (2D/2D) p-n heterojunction CuS-Bi2WO6 (CS-BWO) with highly connected and matched interfacial lattices was designed via a two-step hydrothermal tandem synthesis strategy. The integration of CuS with BWO created a robust interface electric field and provided fast charge transfer channels due to the work function difference, as well as highly connected and matched interfacial lattices. The p-n heterojunctionpromotedelectron transfer from the Cu to Bi sites, leading to coordination of Bi sites with high electronic density and low oxidation state. The Bi sites in BWO nanosheets facilitated the adsorption and activation of CO2, and generation of high-coverage key intermediate b-CO32-, while broad light-harvesting CuS (CS)provide abundant photoinduced electrons that were injected into the conduction band of BWO for CO2 photoreduction reaction. Remarkably, the p-n heterojunction CS-BWO exhibited CO and CH4 yields of 135.7 and 62.5 µmol g-1, respectively, which were significantly higher than those of CS, BWO, and physical mixture CS-BWO nanosheets. This work provided an innovative design strategy for developing high-activity heterojunction photocatalyst for converting CO2into value-added solar fuels.

Effect of Adding Phosphorus on Crystal Structure of W-V-Nb Complex Oxide and Catalytic Selective Oxidation of Acrolein.

The changes in the crystal structure of the W-V-Nb complex oxide with phosphorus addition to the hydrothermal synthesis process are investigated. The effect of the constituent units and crystal structure of phosphorus-added W-V-Nb complex oxide catalysts on the activity and selectivity for selective oxidation of acrolein is discussed. Phosphorus addition to the hydrothermal synthesis process promotes the formation of orthorhombic and trigonal W-V-Nb complex oxides. Orthorhombic and trigonal W-V-Nb complex oxide catalysts give higher acrylic acid selectivity in acrolein oxidation compared to poorly crystalline catalysts that only have {M6O21} pentagonal units and 7-membered rings.

Hydrothermal synthesis of rGO and MnCoS composite for enhanced supercapacitor application

Nanostructured materials incorporating transition metal sulfides have demonstrated considerable potential across various applications, particularly in the realms of energy production and storage. Sulfide-based material preparation is a challenging and costly procedure that requires a high temperature and reducing atmosphere. This work reports that manganese cobalt sulfide (MCS) and reduced graphene oxide composite manganese cobalt sulfide (rMCS) were successfully prepared through a hydrothermal method. Various characterization techniques were employed to analyze the prepared materials, including X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, Brunauer-Emmett-Teller analysis, and X-ray photoelectron spectroscopy. In a three-electrode system, MCS and rMCS electrodes exhibit an excellent specific capacitance of 1695 and 1925 F g−1 at 1 A g−1 current density respectively. MCS delivers the capacitance retention of 99% and rMCS exhibits the capacitance retention of 100% capacitance retention over 5000 consecutive cycles. The constructed asymmetric supercapacitor electrode (rMCS//rGO) exhibits the energy and power density of 64 Wh kg−1 at 799 W kg−1, respectively with outstanding cyclic stability of 97.4% even after 10,000 cycles. The exceptional electrochemical properties of MCS with rGO composite electrode indicate that they would make an outstanding electrode material for cutting-edge energy storage devices.

Nb(V)-containing saponite: A versatile clay for the catalytic degradation of the hazardous organophosphorus pesticide paraoxon under very mild conditions

A synthetic saponite clay containing structural Nb(V) metal centres (NbSAP) was investigated in the abatement of paraoxon-ethyl, an anti-cholinergic organophosphorus pesticide, under mild conditions (neutral pH, room temperature and ambient pressure) in heterogenous phase, without additional basic additives. The material was selected according to its high surface acidity and ease of preparation through a one-step hydrothermal synthesis. The presence of Nb(V) ions played a crucial role in efficiently catalysing the degradation of aggressive chemical substrates. A niobium(V) oxide with very low surface acidity was also tested as a reference material. The study employed a multi-technique approach to monitor the pesticide degradation pathway and by-products formed during abatement experiments in polar non-protic and aqueous solvents. Notably, in water, the concentration of paraoxon-ethyl significantly decreased by 82 % within the first hour of contact with the clay. Additionally, NbSAP demonstrated a good performance after three repeated catalytic cycles and subsequent reactivation.

Preparation of C-S-H seeds from waste glass powder and its effect on early performance of cement paste

This study investigates the hydrothermal synthesis of calcium silicate hydrate (C-S-H) seeds using nano-size glass powder (NGP) derived from siliceous raw materials and CaO as the calcareous precursor. The influence of varying NGP concentrations on the particle size, microstructure, and phase composition of the C-S-H seeds was systematically analyzed. The synthesized C-S-H seeds were subsequently employed as additives to evaluate their effects on the early hydration process and compressive strength development of cement paste. The results indicate that increasing the NGP concentration from 0.2 mol/L to 0.8 mol/L leads to an exponential increase in the median particle size of the C-S-H seeds from 147 nm to 1328 nm and a corresponding morphological transformation from flocculent to granular structures. Additionally, the purity of the C-S-H sample decreased from 74.8% to 54.5% as the NGP concentration increased. The addition of C-S-H seeds can increase the 12h compressive strength of cement pastes by 15.5%–53.5%. This improvement is due to the accelerated early hydration kinetics induced by the C-S-H seeds, which act as nucleation sites, thereby increasing the nucleation and growth rates by 31.4% and 53.2%, respectively.

The adsorption performance of high crystallinity Na-p zeolites prepared from oil shale ash for the waste water treatment

ABSTRACTS The Na-p type zeolite has been prepared by the alkali fusion hydrothermal synthesis method using the pure oil shale ash (OSA) and mixture of OSA and coal fly ash (CFA) as raw materials, which was used for adsorption of methylene blue (MB). The XRD spectra of zeolite synthesized from pure oil shale residue under different conditions indicated that the optimal experimental conditions were determined as follows: acid leaching concentration of 10%, sodium hydroxide dosage of 7 g, crystallization temperature of 130°C, and crystallization time of 12 h. Under the same conditions, zeolite was synthesized using the mixture of OSA and CFA, and its properties were characterized using XRD, SEM, and BET techniques. The results showed that the specific surface area and crystallinity of the zeolite prepared from the mixture were 59.6 m2/g and 86.32%, respectively, which were higher than that of pure OSA (20.6 m2/g and 64.07%). When 0.05 g of zeolite was added to the 35 mg/L MB solution and adsorbed for 180 min, the removal rates of MB by pure OSA, single-source zeolite and zeolite prepared from the mixture were 27.6%, 83.4%, and 99.2%, respectively. The adjusted R square verified that the pseudo-second-order kinetics and Langmuir isotherm model were the best fitting models. The maximum adsorption capacity (Qmax) of zeolite prepared from the mixture for MB was 55.5 mg/g. The above results proved that the novel material prepared in this study could be a potential effective wastewater treatment material.

Rational Design of Novel Polar Nonlinear Optical Materials in Alkali Metal Rare Earth Iodates.

Four new potassium rare earth iodates, namely, acentric K2Lu(IO3)5 and KM(IO3)4(HIO3)0.33 (M = Ce/Pr) and centric KLa(IO3)4, were successfully grown by mild hydrothermal reactions. Three of them exhibit polar structures; K2Lu(IO3)5, KCe(IO3)4(HIO3)0.33, and KPr(IO3)4(HIO3)0.33 show second-harmonic generation (SHG) responses of 3.0, 1.0, and 0.8 × KDP, respectively. These three iodates are phase-matchable for second-harmonic generation. The influence of changes in the radius and coordination mode of rare earth ions on the crystal structure and SHG response has been discussed in detail. Our findings suggest that in the alkali metal rare earth iodate, modulating the arrangement of iodate groups by changing the coordination geometry of rare earth ions is an effective strategy for designing polar NLO materials.

Hollow Superhelices Based on Chiral Europium Coordination Polymers.

The construction of helical nanotubes based on chiral coordination polymers (CPs) is an intriguing but challenging task, which is important for the development of functional materials that combine macroscopic chirality with tube-related properties. Here, we selected a chiral europium phosphonate system, e.g., Eu(NO3)3/R-,S-pempH2, and carried out a systematic work. By controlling the hydrothermal reaction conditions such as the pH value of the reaction mixture, the molar ratio and concentration of the reactants, we obtained block-like crystals of R/S-1b, rod-like crystals ofR/S-3r, hollow superhelices of R/S-2hh, and solid superhelices of R/S-4sh. In the latter two cases, the chirality has been successfully transferred and amplificated from the molecular level to the macroscopic level. Interestingly, compounds R/S-2hh and R/S-4sh have the same chemical composition of Eu(R/S-pempH)3×2H2O and show identical PXRD patterns, thus can be considered as the same material except for different morphologies. We further investigatedtheir circularly polarized luminescence (CPL) properties and found that the hollow superhelix of R/S-2hh had a larger dissymmetry factor than the solid superhelix of R/S-4sh. This study not only provides the first example of hollow superhelices of chiral CPs, but also offers the possibility of modulating the chiroptical properties of CPs through morphological control.

Hydrothermal Growth Zinc Oxide Nanorods for pH Sensor Application

The aim of this work is to apply synthesized zinc oxide (ZnO) Nanorods using hydrothermal (HTL) growth technique for pH sensor application. The highly crystallite of ZnO Nanorods was obtained by anneal the growth ZnO Nanorods in furnace at 200 °C for 2 hours. Besides that, XRD analysis shows the produced ZnO Nanorods belonged to the (002) plane. Furthermore, Scanning Electron Microscope (SEM) images confirm that the ZnO Nanorods with hexagonal-faceted structural were successfully produced by HTL growth technique. In addition, Ultraviolet–visible (UV-Vis) spectrophotometer analysis shows that the synthesized ZnO belongs to the wide band gap semiconductor material. The growing ZnO Nanorods were then subjected to electrical measurement with various pH levels. The outcome demonstrates that the current rises as the solution changes from acidic to alkaline. Overall, our study shows a relationship between the electrical as well as the structural characteristics of ZnO Nanorods at various pH levels.

Hydrothermal synthesis of MoS2 nanoparticle as an electroactive material for supercapacitor

Hydrothermal synthesis of MoS2 nanoparticle as an electroactive material for supercapacitor

Catalytic hydrothermal reaction of biomass and its application in blast furnace injection: Physicochemical, conversion mechanism, combustion behavior

This study employs a combination of experimental research and computational fluid dynamics (CFD) simulation to evaluate the optimal conditions for catalytic hydrothermal carbonization suitable for blast furnace injection. Through FTIR spectroscopy, Raman spectroscopy, ICP analysis, and combustion kinetics analysis, the physical and chemical properties of the hydrochar were determined. Subsequently, these properties along with kinetic parameters were applied to an improved CFD model to compare the flow patterns and combustion performance of hydrochar with PCI coal in blast furnaces. The results indicate that the optimal HTC conditions are identified at 300 °C with FeCl3 catalysis, yielding hydrochar (HTC-300-FeCl3) characterized by a calorific value of 32.10 MJ/kg, 98 % K element removal, and enhanced carbonaceous structure ordering. This is attributed to the addition of FeCl3 effectively enhances the generation of hydroxyl radicals in the aqueous phase and promotes deoxygenation and hydrogenation reactions in the solid phase, improving the quality of hydrochars. In addition, CFD model shows that the HTC-300 FeCl3 exhibits a higher burnout (86.2 %) and average gas temperature (2383.1 K) compared to PCI coal, indicating its greater potential as a PCI coal substitute in BF injection.

Hierarchical Bifunctional NiO Electrocatalyst: Highly Porous Structure Boosting the Water Splitting Activity.

The development of an efficient, low-cost and earth-abundant electrocatalyst for water splitting is crucial for the production of sustainable hydrogen energy. However their practical applications are largely restricted by their limited synthesis methods, large overpotential and low surface area. Hierarchical materials with a highly porous three-dimensional nanostructure have garnered significant attention due to their exceptional electrocatalytic properties. These hierarchical porous frameworks enable the fast electron transfer, rapid mass transport, and high density of unsaturated metal sites and maximize product selectivity. Here the process involved obtaining monodispersed microrod-shaped Ni(OH)2 through a hydrothermal reaction, followed by a heat treatment to convert it into hierarchical microrod-shaped NiO materials. N2 sorption analysis revealed that the BET surface area increased from 9 to 89 m2/g as a result of the heat treatment. The hierarchical microrod-shaped NiO materials demonstrated outstanding bifunctional electrocatalytic water splitting capabilities, excelling in both HER and OER in basic solution. Overpotential of 347 mV is achieved at 10 mA/cm2 for OER activity, with a Tafel slope of 77 mV/dec. Similarly, overpotential of 488 mV is achieved at 10 mA/cm2 for HER activity, with a Tafel slope of 62 mV/dec.

Biomass Carbon Dots as Fluorescent Probes for Fast and Highly Selective Detection of Fe3 + in Water Media.

In this study, a novel fluorescent probe for the rapid and highly selective detection of Fe3 + based on biomass carbon dots (b-CDs) was developed. The b-CDs were obtained via one-step hydrothermal synthesis by utilizing laurel fallen leaves. And the as-synthesized b-CDs were applied for sensing Fe3+ based on fluorescence (FL) quenching effect both in water and phosphate buffer solution (PBS) with a wide linear range from 1 µM to 300 µM, the detection limits (LODs) respectively to be 0.34 µM in water and 0.48 µM in PBS solution. The FL intensity of b-CDs was quenched fleetly within 1min after adding Fe3+. The sensing mechanism of the b-CDs + Fe3+ system can be attributed to the internal filtration effect (IFE) mechanism and the electron transfer (ET) between b-CDs and Fe3+ in water, and only the IFE mechanism in PBS solution based on multiple experimental evidences. Moreover, the as-proposed probe was successfully adopted for monitoring Fe3+ in lake water and tap water samples. This research shows some merits of economic, simplicity, green, high selectivity, and quick response for Fe3+ determination, and provides an approach for the water quality monitoring of Fe3+ and the effective utilization of waste biological materials.