Hydrothermal Synthesis Research Articles

Recent Advances in the Synthesis and Photoelectrocatalysis of Zeolite-Based Composites

Zeolites are a class of porous aluminosilicates possessing high surface area, good hydrothermal stability, strong sorption, and high ion-exchanging potential, and which frequently serve as efficient catalytic materials. The composites which integrate zeolite with alternative substances like metal oxides or carbon-based materials steadily outperform individual constituents. Recently, the application of zeolite-based composites in the field of photocatalytic oxidation and electrocatalytic oxidation/reduction, which is mainly focused on pollution treatment in sewage and air, have garnered significant attention. Several synthesis strategies for zeolite-based composites including post-treatment and in situ hydrothermal synthesis methods are explicated. Meanwhile, multifarious types of zeolite-based photoelectric catalytic composites are also summarized. Finally, we highlight the advancements improving the performance of zeolite-based composites in the photocatalytic treatment of organic pollutants in wastewater and the electrocatalytic reduction of CO2 and organics.

Hydrothermal synthesis of boron-nitrogen-sulfur tri-doped reduced graphene oxide for PEM fuel cell applications

Hydrothermal synthesis of boron-nitrogen-sulfur tri-doped reduced graphene oxide for PEM fuel cell applications

A study of microstructure and properties of BaTiO3 from solid‐state and hydrothermal synthesis on MLCCs performance

AbstractIt has generally been believed that the performance of ultra‐thin multilayer ceramic capacitors (MLCCs) are mainly controlled by doping elements and the contribution of synthesis approaches of BaTiO3 (BT) powders can be neglected. However, in this study, we demonstrate that the solid‐state powders exhibit a heterogeneous distribution of residual BaCO3 (BC), TiO2, or Ti‐rich phases, whereas hydrothermal powders are characterized by a BC surface layer, which can be characterized by nanoinfrared (AFM‐IR), and the divergent approaches play an important role in the “core–shell” structure. The BC layer in hydrothermal BT contributes to Ti vacancies during sintering, increasing the “core–shell” ratio in MLCCs. This results in augmented capacitance but reduced performance at elevated temperatures. Conversely, the presence of a Ti‐rich phase in solid‐state powders induces Ba vacancies, leading to decreased “core–shell” ratios and dielectric constants.

Boosted Photoelectrochemical Water Oxidation Performance with a Quaternary Heterostructure: CoFe2O4/MWCNT-Doped MIL-100(Fe)/TiO2

Cobalt ferrite (CoFe2O4) combined with multi-walled carbon nanotubes (MWCNTs) is an outstanding material regarding photoelectrochemical water oxidation (PEC-WO) because of its excellent catalytic properties and stability. On the other hand, surface imperfections in CoFe2O4 can cause band bending and surface Fermi level pinning, significantly reducing its PEC conversion efficiency. Heterostructure engineering is essential for achieving increased light-gathering capacity and charge separation efficiency for PEC-WO. In this study, a quaternary heterostructure of CoFe2O4/MWCNT-doped Metal–Organic Framework-100 (Iron), MIL-100(Fe)/Titanium Oxide (TiO2) was synthesized by using a combination of hydrothermal, solvothermal, and “dip and dry” techniques. Characterization results confirmed the formation of a structural network of MIL-100(Fe) on TiO2 surfaces, enhanced by the incorporation of MWCNTs during the hydrothermal reaction. Under 1 sun irradiation, the resultant quaternary heterostructure displayed a photocurrent density (Jph) of 3.70 mA cm−2 under free bias voltage, which is around 3.08 times more than that of pristine TiO2 photoanodes (Jph = 1.20 mA cm−2). This investigation highlights the advantages of the MIL-100(Fe) network in improving the solar PEC-WO performance of TiO2 photoanodes.

Recent Advances in the Synthesis and Application of TS‐1 Zeolite for Green Catalytic Oxidation

AbstractTS‐1 has a unique structure, and TS‐1/H2O2 oxidation system for composition shows excellent catalytic performance in the oxidation of a variety of organic matter. The response conditions of the reaction system are mild, and the ultimate oxidation product is water. It is a typical “green catalytic” system and has received widespread attention from researchers. Here, the synthesis progress of TS‐1 to improve the accessibility and activity of active sites by doping mesoporous and microporous structures into traditional TS‐1 zeolite in recent five years are reviewed, including hydrothermal synthesis, dry gel conversion synthesis, solvent‐free synthesis, microwave assisted synthesis, and isomorphous substitution. Meanwhile, the application of TS‐1/H2O2 system in oxidative desulfurization, ketone ammonia oxidation, olefin epoxidation, and hydroxylation of aromatic hydrocarbons reactions are summarized and discussed. What's more, the reaction mechanism based on TS‐1/H2O2 system is proposed on regarding the isolated skeleton Ti site in titanium‐silicon zeolite as the active central site. Finally, the challenges and future development prospects of TS‐1 zeolite in synthesis and catalytic applications are predicted.

One-Step Hydrothermal Synthesis of Glucose-Induced Low Crystallinity NiCo-Based Layered Double Hydroxides for High-Performance Asymmetric Supercapacitors.

In order to improve the electrochemical performance of NiCo-based layered double hydroxide (NiCoLDH), the synthesis of low-crystallinity NiCoLDH was induced by the adsorption of glucose and NiCoLDH. The results showed that glucose could not only effectively regulate the pore structure and morphology of NiCoLDH, but also had a regular effect on crystallinity. Pure phase NiCoLDH had higher crystallinity. When the mass of glucose is 0.05 g, the prepared NiCoLDH-0.05 is a short-range ordered structure embedded in the amorphous matrix. The crystallinity of the product decreases further with the further increase of glucose mass. Since the ordered structures have higher electrical conductivity, and amorphous structures have more defects and active sites, the structure of NiCoLDH-0.05 is conducive to achieving the best electrochemical performance. Electrochemical test results show that NiCoLDH-0.05 has a high specific capacitance, about 12 times that of the pure phase NiCoLDH, the mass of glucose is higher than or below 0.05 g, the specific capacitance will be further reduced. NiCoLDH-0.05 and activated carbon assembled into an asymmetric supercapacitor have a power density of 400 W kg-1 at an energy density of 32.7 Wh kg-1. This study provides a new idea for obtaining excellent electrochemical properties by adjusting LDH crystallinity.

Hydrothermal Synthesis of La-MoS2 and Its Catalytic Activity for Improved Hydrogen Evolution Reaction

Hydrothermal Synthesis of La-MoS2 and Its Catalytic Activity for Improved Hydrogen Evolution Reaction

Highly dispersed CoWO4 nanoparticles anchored on CNT as electrode for hybrid supercapacitor by microwave-assisted hydrothermal synthesis

Highly dispersed CoWO4 nanoparticles anchored on CNT as electrode for hybrid supercapacitor by microwave-assisted hydrothermal synthesis

Nitride Zeolites from Ammonothermal Synthesis.

Oxide zeolites are synthesized from aqueous solutions in an established way employing hydrothermal synthesis. Transferring this approach to nitride zeolites requires a solvent providing nitrogen for which ammonia has proven to be particularly suitable. We present the successful ammonothermal synthesis of the (oxo)nitridosilicate compounds Ce3[Si6N11], Li2RE4[Si4N8]O3 (RE = La, Ce) and K1.25Ce7.75[Si11N21O2]O0.75. Within this procedure, the usage of supercritical ammonia as a solvent as well as the utilization of the mineralizers NaN3, Li3N and KN3, respectively, allowed the targeted synthesis of large single crystals. Formation of these (oxo)nitridosilicates depend mainly on the employed mineralizer despite their similar degree of condensation. The three compounds were structurally characterized using X-ray diffraction and their crystal structures contain a wide range of different ring sizes within their tetrahedra networks. The zeolite(-like) crystal structures are elucidated and compared to known nitridosilicate representatives of the respective structure types. Their elemental composition was investigated using energy-dispersive X-ray (EDX) spectroscopy and incorporation of the O rather than N-H functionality was confirmed by Fourier-Transform infrared (FTIR) spectroscopy as well as by charge distribution (CHARDI) and bond valence sum (BVS) calculations. The presented examples demonstrate that ammonothermal synthesis provides a one-step access from elemental starting materials towards nitride zeolites.

Resistance Welding Joints of CF/PEEK Orthogonal Laminates Strengthened by in situ Grafting of ZnO‐Nanowires: Preparation, Properties, and Mechanism

ABSTRACTA high strength bonding interface by resistance welding has always been a goal for the production of highly reliable resin‐based composite joints. In this work, SS mesh element with grafted ZnO nanowires (SSM@ZnO) was developed for resistance welding of CF/PEEK composite laminates to improving interfacial strength. First, the surface of stainless‐steel mesh (SSM) was modified by in Situ grafting of zinc oxide (ZnO) nanowires via hydrothermal growth method and the as‐obtained product (SSM@ZnO) used to the resistance welding of carbon fiber/polyether ether ketone (CF/PEEK) orthogonal laminates. The dependance of the SSM@ZnO microstructure, heating properties, wettability and interfacial adhesion on the growth time was investigated. The electrical heating rate under constant input power is increased from 4.8°C/s to 7.12°C/s, and IFSS between SSM@ZnO and PEEK resin is increased from original 45 MPa to 61 MPa. The mechanical properties and failure mode of CF/PEEK resistance welding joints were characterized by single lap shear stress (SLSS) and SEM, respectively. At SSM@ZnO growth time of 8 h, the SLSS reaches the maximum value of 52.8 MPa, and the failure mode was shifted from interfacial peeling between CF/PEEK laminate and adhesion layer to fiber tearing of CF/PEEK laminate surface.

Improved activity and coking-resistance of Fe2O3/ZrO2 catalysts by hydrothermal synthesis in propane dehydrogenation with CO2: Experimental, DFT calculations, and deactivation modeling

In this work, two ZrO2-supported Fe2O3 catalysts were synthesized through the impregnation (Fe2O3/t-ZrO2) and the hydrothermal (Fe2O3/c-ZrO2) methods. The hydrothermal preparation improved the catalyst activity and propylene yield; propane conversion: 45.8 % vs. 31.2 %, propylene yield: 31.1 % vs. 23.2 %. This higher activity was attributed to the high specific surface area and thereby higher Fe dispersion that led to more formation of active Fe3 + sites. According to results, the t-ZrO2 surfaces were known to be more favorable for coke reaction compared to c-ZrO2. Adsorption energy of propane and propylene onto the most stable surfaces of ZrO2 was measured as a criterion for side reactions and coke deposits by DFT calculations. The results showed that propane and propylene are more adsorbed onto t-ZrO2 than onto c-ZrO2, which indicates more cracking of propane and propylene onto t-ZrO2. Finally, the experimental data were successfully fitted with the Deactivation Model with Residual Activity (DMRA). It was found that the Fe2O3/c-ZrO2 catalyst has a higher resistance against the deactivation by coke deposits compared to the Fe2O3/t-ZrO2 catalyst; activation energy of deactivation function: 83.64 vs. 70.09 kJ/mole.

Corrosion of nickel foam electrodes during hydrothermal reactions: The influence of a simple protective carbon black coating

Nickel foam (NF) substrates are widely used to support electrocatalysts, and this is frequently achieved using hydrothermal reactions, where the NF is immersed in the hydrothermal reactor together with the electrocatalyst precursors. However, other reactions including the corrosion of the NF and changes to the pH occur simultaneously, and these can affect the quality of the final electrocatalyst. Herein, a simple approach is devised to minimise these unwanted reactions. Carbon black (CB) was non-covalently functionalised at room temperature using tannic acid to give very stable and good dispersions of fCB in deionised water. Using a simple sonication step, the NF was coated with a uniform layer of the dispersed fCB. This layer served to minimise the corrosion of the underlying NF during the hydrothermal reactions with very good protection observed up to a temperature of 160 °C in deionised water at a pH of 2.0. The corrosion currents of the NF and fCB@NF were estimated at 8.7 µA and 3.9 µA, respectively, at room temperature in this acidic solution. Using a model reaction, the successful nucleation and growth of MnCo2O4 cubes was observed at fCB@NF, but not at the corroding NF.

Hydrothermally Synthesized NiO-SnO2 Nanocomposite as an Efficient Electrocatalyst for Oxygen Evolution Reaction (OER) and Urea Oxidation Reaction (UOR)

This study presents the synthesis and electrochemical evaluation of a NiO-SnO2 nanocomposite as an advanced catalyst for the oxygen evolution reaction (OER) and urea oxidation reaction (UOR) in an alkaline medium. The NiO-SnO2 composite, prepared via hydrothermal synthesis and subsequent annealing at different temperatures (400°C, 500°C, 600°C), demonstrated excellent catalytic performance, and attributed to its unique dual-phase structure comprising monoclinic NiO and tetragonal SnO2. XRD, SEM, and XPS analyses confirmed the material's crystallinity, morphology, and chemical states, highlighting the role of annealing temperature in optimizing structural properties. Electrochemical measurements revealed that the composite annealed at 600°C exhibited superior OER and UOR activities, with overpotentials of 320mV and 140mV, respectively, at a current density of 10mAcm⁻². This enhanced performance is attributed to the synergistic effects between NiO and SnO2, which improve electron transport, active site availability, and catalyst stability. The study underscores the potential of NiO-SnO2 composites for energy-efficient water splitting and urea-rich wastewater treatment.

Green and facile synthesis of multihydroxy NaYF4:Yb/Er upconversion nanoparticle using natural peach gum

A simple and effective method has been developed for synthesizing multihydroxy NaYF4:Yb/Er upconversion nanoparticle (UCNP) using natural peach gum (PG) via hydrothermal synthesis. Initially, PG binds to metal ions, followed by pyrolysis to form water-soluble PG polysaccharide (PGP) ligands that coat the surface of the UCNP. This coating imparts hydrophilicity and introduces numerous hydroxyl groups to the UCNP. The resulting UCNP, with diameters ranging from 100 to 200 nm, exhibit a mixed cubic-hexagonal crystalline structure and demonstrate good upconversion luminescence and low toxicity. Additionally, the surface hydroxyl groups facilitate conjugation with functional molecules, enhancing the potential for post-modification. This green, simple, and efficient approach offers a promising pathway for producing UCNP, opening new possibilities for various applications.

Bimetallic nickel‑cobalt sulfide derived from lignin-MOFs hybrid as a high-efficiency heterogeneous catalyst for hydrogenolysis of lignin dimers.

Lignin represents a significant source of aromatic hydrocarbons in the natural world. The production of high-value chemicals from lignin has the great potential to effectively address the issue of fossil energy scarcity. In this study, complex sulfides of nickel‑cobalt bimetallic catalysts were prepared via hydrothermal synthesis and subsequently employed in the catalytic hydrogenolysis of CO bonds present in lignin. A series of complex sulfides Ni3S2/Co3S4-CSn-x-T derived from lignin-MOF (n = 0.5, 1, 1.5 and 2; x = 2, 4 and 6; T = 400, 500, 600 and 700 °C), were prepared under different conditions and subsequently employed in the catalytic hydrogenolysis of lignin model compounds. The optimal catalyst Ni3S2/Co3S4-CS1-4-500 exhibited the highest conversion rate of benzyl phenyl ether (BPE) (about 97.3 %), and the yields of toluene and phenol produced were 49.5 % and 43.6 %, respectively with isopropanol as the reaction solvent and no external H2. The introduction of element sulfur in catalysts could effectively inhibit the further hydrogenation of generated aromatic chemicals. The catalysts were well characterized, and the results demonstrated that the catalysts exhibited high catalytic activity with an increased loading of active components. This study provided some novel findings for the construction of biomass-based catalysts and the production lignin-derived aromatic chemicals.

Adsorption of phosphate by ZnCr-LDHs and its zirconium-based hydrogel spheres in water

Phosphate, as one of the main sources of eutrophication problems, has received much attention from researchers in recent years. The process of encapsulating layered double hydroxides (LDHs) in a hydrogel provides an application idea for the removal of phosphate from water by powder materials. LDHs nanomaterials have the advantages of excellent performance, low cost and no secondary pollution, and are limited by application challenges such as low hydraulic conductivity and difficulties in solid-liquid separation. In this study, ZnCr layered double hydroxides (ZnCr-LDHs) were prepared by hydrothermal synthesis using triethanolamine as a base source, and Zr4+ was utilized to prepare spherical hydrogel beads loaded with ZnCr-LDHs sodium alginate. The successful synthesis of ZnCr-LDH materials and Zirconium alginate hydrogel beads encapsulated with ZnCr-LDH was validated through an array of characterization techniques, including Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), and Fourier Transform Infrared Spectroscopy (FT-IR). The effects of adsorbent dosing, solution pH, adsorption time, initial phosphate concentration, temperature and other anions on phosphate adsorption were investigated. The results showed that under certain experimental conditions (adsorbent dose = 1.0 g/L, initial phosphate concentration = 100 mgP/L, reaction time = 12 h), the composite material could effectively remove phosphate with the maximum adsorption up to 134.95 mgP/g, which effectively solved the solid-liquid separation difficulties of powdered nanomaterials.

Domain-limited surface oxygen vacancy in rutile TiO2 for enhancing photocatalytic hydrogen evolution

Defect engineering is an effective strategy for enhancing the photocatalytic performance of semiconducting metal oxides. In this study, we demonstrate a simple method to engineer oxygen vacancies (OVs) on the surface of rutile TiO2 by the use of thiourea. No bulk phase defects or heteroatom doping are introduced during the hydrothermal reaction, while preserving the original morphology of rutile TiO2. It was observed that the structural synergies with surface OVs significantly alter the electronic structure, thereby extending the absorption region of rutile TiO2 and promoting efficient separation and transport of photogenerated carriers to the surface. The rutile TiO2 with OVs on its surface exhibits highly photocatalytic H2 evolution activity as 54.7 mmol·g-1·h-1 (with 1 wt% Pt loading), with an apparent quantum efficiency (AQY) of 24.7% at 380 nm.

Construction of 2D/2D heterostructure with porous few layer g-C3N4 and NiCo2O4 nanosheets towards electromagnetic wave absorption

Developing high-performance materials with ultra-high reflection loss (RL ≤ -65 dB) for electromagnetic wave (EMW) absorption is pivotal to address electromagnetic pollution, but it is still challenging. Herein, a two-dimensional (2D)/2D PFL g-C3N4/NiCo2O4 heterostructure with porous few-layer g-C3N4 (PFL g-C3N4) and ultrathin NiCo2O4 nanosheets has been prepared by self-assembly, hydrothermal reaction, and calcination strategies. The 2D/2D heterostructure exhibits extraordinary EMW absorption property, achieving a reflection loss (RL) value of -68.59 dB and an effective absorption bandwidth (EAB) of 1.92 GHz at a matching thickness of 2.5 mm. As expected, the porous few layer g-C3N4 nanosheets provide rich interface which increases multiple reflection paths and enhances the conduction loss. The cooperative effects of magnetic loss, dielectric loss, and impedance matching contribute to the exceptional EMW absorption property of PFL g-C3N4/NiCo2O4 (2D/2D) heterostructure. The potential of PFL g-C3N4/NiCo2O4 in actual radar stealth is verified through radar scattering cross-section (RCS) simulation. This work paves the way for utilizing 2D/2D heterostructure as an ultra-efficient EMW absorbers.

Efficient H2 evolution over MoS2-NiS2/g-C3N4 S-scheme photocatalyst with NiS2 as electron mediator

Low-cost transition metal sulfides are commonly utilized as photocatalysts for H2 production owing to their exceptional conductivity and superior specific surface area. In this study, MoS2-NiS2 nanoflowers with multidimensional space structure was obtained through the sulphuration reaction between S2- and NiMoO4 under Kirkendall effect during hydrothermal reaction. Subsequently, MoS2-NiS2 was loaded on the surface of g-C3N4 nanosheets using a solvent self-assembly strategy to form 3D MoS2-NiS2/g-C3N4 heterojunctions. The experimental results demonstrate that the H2 production rate of 20 wt% MoS2-NiS2/g-C3N4 reaches 22153 μmol·g-1·h-1 under a 300 W Xe lamp irradiation, which is 59.5 and 201.4-folds than MoS2-NiS2 and g-C3N4, and surpasses 20 wt% MoS2/g-C3N4 (211 μmol·g-1·h-1) and 20 wt% NiS2/g-C3N4 (6183 μmol·g-1·h-1). The XPS and Superoxide radical capture experiments demonstrate that the charge transfer between MoS2-NiS2 and g-C3N4 follows the S-scheme route, and NiS2 functions as an electron mediator, facilitating the transfer of electrons from MoS2 to g-C3N4 to consume the holes, which enhances the efficiency of H2 evolution reaction on g-C3N4. Furthermore, the S-scheme heterojunction of MoS2-NiS2/g-C3N4 with the multidimensional geometric structure can provide abundant active sites for catalytic reactions, this presents a promising approach for the development of cost-effective and high-performance g-C3N4-based heterojunctions. This work offers distinctive perspectives on the trajectory of renewable H2 energy development.

In situ growth of MnO2 on graphitized cellulose nanocrystal: A novel coaxial heterostructures with unblocked conductive networks as advanced electrode materials for supercapacitor

Manganese dioxide (MnO2) with high theoretical capacitance and natural abundance has attracted great attention but is still challenging for use in supercapacitors, due to the limited conductivity and lower electron and ion migration. Here, a facile in situ growth strategy is developed to prepare heterostructural graphitized cellulose nanocrystal (GCNC)/MnO2 with unblocked conductive networks through a hydrothermal reaction. The GCNC with highly ordered graphitic carbon layers as conductive support framework solves the agglomeration problem of MnO2 and increases effective specific surface areas in contact with electrolyte ions. Meanwhile, the stable connection of MnOC covalent bonds enhances the interface bonding, which effectively reduces the contact resistance at the interface of heterostructural GCNC/MnO2 and enhances the interface firmness. The resulting GCNC/MnO2 electrode shows a remarkable specific capacitance of 528.2 F g−1 at 0.5 A g−1. Furthermore, the symmetric supercapacitor based on GCNC/MnO2-15 mM exhibits high rate capability and excellent cycle stability of 100 % capacitance retention after 3000 cycles. This work provides a new path to designing high performance electrode material for sustainable energy technologies.