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Seeking for extremely active and durable bifunctional electrocatalysts towards the overall water splitting possesses a strategic significance on the development of sustainable and clean energy for the replacement of fossil fuels. Ir-based nanomaterials are deemed as one of the most high-efficiency oxygen evolution reaction electrocatalysts while the hydrogen evolution reaction performance is unfavorable. In this work, we report a one-pot hydrothermal synthesis of N-doped graphene anchored Ir nanoparticles (Ir/N-rGO) with ultrasmall particle size (∼2.0 nm). Apart from the predictably superior OER performance, the resultant Ir/N-rGO also displays excellent hydrogen evolution reaction (HER) performance, requiring merely 76 and 260 mV overpotentials to achieve the current density of 10 mA cm-2 towards HER and OER, respectively. When applied as the bifunctional electrodes for overall water splitting, Ir/N-rGO needs a lower overpotential (1.74 V) to achieve a current density of 50 mA cm-2 in alkaline solution, exceeding that of Pt/C and RuO2 couple (1.85 V). Thus, the as-fabricated Ir/N-rGO has a commendable prospect in the practical application of alkaline water electrocatalysis.

Background: Crystal violet dye is stable and difficult to be biodegraded owing to the existence of the multiple aromatic rings of the crystal violet molecules. Removing crystal violet dye from the wastewater is a major challenge. Objective: The aim of the research is to synthesize barium carbonate/tin dioxide nanoparticles and investigate the photocatalytic performance for the degradation of crystal violet. Methods: Barium carbonate/tin dioxide nanoparticles were synthesized via a facile hydrothermal route without any surfactants. The crystal structure, micro-morphology, size and optical performance of the barium carbonate/tin dioxide nanoparticles were investigated by powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy and solid ultraviolet-visible diffuse reflectance spectrum. Results : The size of the barium carbonate/tin dioxide nanoparticles is 20 nm to 200 nm with the band gap of 3.71 eV. The photocatalytic activity of the barium carbonate/tin dioxide nanoparticles was measured by the photocatalytic degradation of crystal violet. The crystal violet degradation efficiency reaches 92.1% with the ultraviolet-visible irradiation time of 8 h using 10 mg barium carbonate/tin dioxide nanoparticles. The crystal violet degradation ratio increases to 96.1% when the dosage of the barium carbonate/tin dioxide nanoparticles increases to 20 mg/10 mL crystal violet dye solution. Active species capture photocatalytic experiments showed that the holes, hydroxyl radicals and superoxide ion radicals are the main active species. Reusability experiments displayed that the barium carbonate/tin dioxide nanoparticles are stable for the crystal violet dye degradation. Conclusion: The barium carbonate/tin dioxide nanoparticles show good photocatalytic performance toward crystal violet under ultraviolet light irradiation.

In the present study, a Bi$_2$WO$_6$/ZnWO$_4$ photocatalyst was successfully constructed by a modified hydrothermal synthesis method with different molar concentrations of Bi$_2$WO$_6$ with respect to ZnWO$_4$. The variation in molar concentrations of Bi$_2$WO$_6$ changed the photocatalytic properties of the Bi$_2$WO$_6$/ZnWO$_4$ catalyst. The synthesized Bi$_2$WO$_6$/ZnWO$_4$ photocatalyst was characterized by various techniques to decipher its structural and spectral properties. The interaction of Bi$^{2+}$ ionic charge carriers and many-body effects cause the band gap to narrow in Bi$_2$WO$_6$/ZnWO$_4$, as shown by PL analysis. The decrease in band gap energies (E$_g$) from 4.7 eV (ZnWO$_4$) to 3.5 eV (30% Bi$_2$WO$_6$/ZnWO$_4$) is beneficial because less energy is required to excite the valence electrons. The maximum degradation of Plasmocorinth B dye was found with 30% Bi$_2$WO$_6$/ZnWO$_4$ under UV irradiation. This increased activity of 30% Bi$_2$WO$_6$/ZnWO$_4$ can be attributed to the (i) synergistic effect in the bicrystalline framework of Bi$_2$WO$_6$ and ZnWO$_4$, (ii) the high close contact between Bi$_2$WO$_6$ and ZnWO$_4$, and (iii) the small crystallite size. The photocatalytic activity of synthesized Bi$_2$WO$_6$/ZnWO$_4$ photocatalyst shows its significant potential in water/ wastewater treatment application.

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.

In this study, metallic glass is designed tunable for promising functional applications via a facile and stable, one-step process. Creative approach about alloy design and process is based on the unique properties of the Ti-Cu-Ni-Sn metallic glass that are afforded by the varying oxygen affinities of the four constituent elements. This metallic glass exhibits homogeneous nucleation of oxides and uniform formation of the various metal oxides. The alloy design and hydrothermal synthesis to customize the metallic glasses are the most critical factors that determine the characteristics of the metal oxides and the resulting nanostructures and photoelectrode properties. This enables the desired element to be selectively grown via a facile single-step process. These results provide a promising road map for the application of metallic glasses to photoelectrochemical (PEC) solar water splitting, as well as various other new possibilities.

In this work, vanadium and lanthanum co-doped ZnO/CNTs (VL-ZnO/CNTs) composites of large surface area and enhanced light assimilation range were produced for boosted hydrogen evolution from water. The photocatalysts were investigated for their morphological, structural, optical and photocatalytical properties. The photocatalytic activity of the composites was evaluated in pure water and in a mixture of water and methanol under simulated sunlight and visible light illumination. Under simulated sunlight irradiation, the maximum hydrogen generation rate of 925 μmolh−1g−1 from a combination of water and methanol was attained, which is almost 7 times higher than hydrogen generation rate achieved with pure ZnO. The VL-ZnO/CNTs photocatalyst resulted in hydrogen production rate of 267 μmolh−1g−1 from the water-methanol medium when exposed to visible light. This rate was about 3.5 folds lower than that achieved under simulated sunlight illumination. This improvement in hydrogen production rate is attributed to large surface area, high photo-response, better separation/transportation of the charge carriers and synergistic impact of V, La and CNTs in the designed photocatalyst.

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.

Textile wastewater contains highly toxic, nondegradable, carcinogenic organic pollutants, causing severe damage to the ecological environment. In this work, β-cyclodextrin carbon-sphere-based nanocomposite (CS/SiO2@β-CD) with a core–shell–shell configuration was prepared by hydrothermal synthesis and subsequent sedimentation-azeotropic distillation with SiO2 as intermediate layer for the removal of crystal violet (CV) and bisphenol A (BPA). The chemical structure and morphology of the CS/SiO2@β-CD were characterized by FT-IR, SEM and TEM. The effects of contact time, pH, temperature and initial concentration of the absorbates on the adsorption property were explored. The CS/SiO2@β-CD showed excellent adsorption capacity on CV and BPA, and the maximum adsorption capacity was 87.873 mg g–1 and 165.095 mg g–1, respectively. Their adsorption process was in line with the pseudo-second-order and pseudo-first-order kinetic models, respectively. The adsorption thermodynamics could be better fitted by Langmuir model than by Freundlich model. The calculated thermodynamic parameters (–ΔG0, ΔS0 and ΔH0) illustrated the adsorption of CV was endothermic, in contrast, the adsorption of BPA was exothermic process. Furthermore, the CS/SiO2@β-CD showed excellent recovery performance, making it a potential adsorbent for the practical treatment of textile wastewater.

Crystallization of DNL-6, a silicoaluminophosphate (SAPO) based molecular sieve with the RHO topology, was investigated under both the hydrothermal synthesis (HTS) and dry-gel conversion (DGC) conditions. Crystallization of DNL-6 under the HTS conditions is rather fast. But a combination of crystallization under the DGC conditions and reducing reaction temperature slow down the reactions, allowing for intermediates to be captured. Under the DGC conditions, DNL-6 crystallizes through a semi-crystalline layered phase. The nature of this intermediate is aluminophosphate (AlPO) rather than SAPO with most P atoms having a local environment of P(–O–Al)3(OH). The surfactant (cetyltrimethylammonium chloride) used for synthesis appears to be part of the layered intermediate. Si is directly incorporated in the DNL-6 framework via SM II mechanism when the semi-crystalline AlPO phase is transforming to DNL-6 with the assistance of a very small amount of water. Both the structure directing agent and the surfactant play a role in the formation of DNL-6, as they were found within the final synthesized products. SEM data show that hydrothermal synthesis produces a much more crystalline product. The facts that the semi-crystalline layered phase was also observed in the powder X-ray diffraction patterns of the solid samples obtained under the HTS conditions and that the evolution of the local structure around P and Al in the intermediate phases are similar imply that under the reaction conditions employed in the present study, the formation pathways of DNL-6 under the HTS and DGC conditions appear to have some similarities.

Nano-zirconia has been widely applied due to its excellent physical and chemical properties (e.g., high strength, corrosion resistance, oxygen ion conductivity). Existing preparation methods of nano-zirconia tend to require long reaction time, and the sizes of final particles are large with uneven distributions. Sub-/supercritical hydrothermal synthesis of nanoparticles is favored by researchers owing to controllable reaction process, uniform particle size distribution, good reproducibility, short reaction time, high conversion rate and harmlessness to environment. In this paper, the characteristics and mechanisms of dissolution, crystallization and growth of nano-zirconia during sub-/supercritical hydrothermal synthesis are systematically reviewed. The influences of process and material parameters on the size and purity of particles are analyzed. Then, the reaction mechanism and product phase transition mechanism during hydrothermal synthesis of zirconia are summarized to provide a theoretical reference for the oriented preparation. Finally, the improvement and commercialization of sub-/supercritical hydrothermal synthesis technology are evaluated, and the future research topics are proposed.

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.

The design and construction of bifunctional electrocatalysts with high activity and durability is essential for overall water splitting. Herein, a unique 3D hierarchical NiMo3S4 nanoflowers with abundant defects and reactive sites were grown directly on carbon textiles (NiMo3S4/CTs) using a facile hydrothermal synthesis method. The defect-rich NiMo3S4 nanoflakes, prepared by doping Ni2+ in the lattice of Mo-S, displays extended d-spacing of (0 0 2) crystal plane, resulting in the electrocatalytic activity of hydrogen evolution and oxygen evolution reaction (HER and OER) was improved under alkaline conditions. The self-supported NiMo3S4/CTs electrode delivers a small overpotential of 149.5 mV for HER and 126.2 mV for OER at 10 mA cm−2, respectively. Based on detailed structure analysis and density functional theory (DFT) calculations, the excellent HER and OER activities can be attributed to the unique structure of the nanoflowers, where the metallic characteristics for Ni-doped Mo-S lead to the enhancement of intrinsic conductivity and the rich abundance of Ni3+ active sites. As a result, the NiMo3S4/CTs as efficient bifunctional electrocatalysts for overall water-splitting was performed in alkaline electrolyte, where the system required only 1.55, 1.66 and 1.76 V to deliver current densities of 10, 50 and 100 mA cm−2, respectively. This study provides a new method for improving the electrocatalysis properties of transition metal sulfides by metal-ion doping to generate more active defect sites, thus promoting the development of non-noble-metal electrocatalysts for overall water splitting.

We have developed an efficient strategy to synthesize an active and durable electrocatalyst of Pd hydride nanocubes (NCs). Instead of the traditional chemical method, the PdH0.43 NCs are firstly prepared via a hydrogen diffusion procedure, followed by hydrothermal synthesis of an amorphous CuO layer encapsulating the PdH0.43 NCs to prevent the hydrogen atoms from escaping. Obvious lattice expansion is demonstrated playing a pivotal role in the enhancement of their oxygen reduction reaction (ORR) activity and durability. The obtained PdH0.43@CuO NCs catalysts exhibit an ORR mass activity of 0.18 A mg−1 at 0.90 V versus reversible hydrogen electrode in an alkaline medium, which is about five times higher than that of commercial Pt/C. Accelerated durability tests show that there is only a 32 mV decay in half-wave potential even after 10,000 potential cycles, indicating the excellent stability of PdH0.43@CuO NCs. Density functional theory (DFT) calculations also indicate that, compared to Pd, PdH0.43 has a lower limiting barrier to form OH− during the ORR process. The present study illustrates the importance of lattice expansion caused by hydrogen and offers an available strategy to design highly efficient and durable Pd-based electrocatalysts for alkaline fuel cells.

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.

Transition metal molybdates/carbonates and hybrid nanomaterials have attracted great attention in energy storage applications because of their enriched redox activity, good electronic conductivity, and stable crystallinity. We synthesize a multicomponent MnMoO4/MnCO3 hybrid by a one-step hydrothermal method with urea as the reaction fuel. By controlling only the urea concentration in the initial precursor solution, the MnMoO4/MnCO3 molecular ratio is controlled effectively, which is found to have a profound effect on the electrochemical properties of the hybrid electrodes. The electrochemical measurements show that the specific capacitance of MnMoO4/MnCO3 hybrid is 1311 F/g, the energy density of 116.8 Wh/kg, and power density of 383 W/kg at a current density of 1 A/g with 79% capacitance retention over 5000 cycles. The fabricated asymmetric supercapacitor device exhibits good energy storage performance, including the specific capacitance of 97 F/g along with the energy density of 26.5 Wh/kg and the power density of 657 W/kg at a current density of 1 A/g and good reversibility with capacitance retention of 85% after 2000 cycles and 70% over 5000 cycles. The increase in the energy density of 900% with a mere 60% decrement in the energy density indicates its potential superior applications in high-power devices.

A novel nano-heterojunction photocatalysts of CdS/MoS2 with appropriate interfacial contact was successfully obtained by the facile two-step hydrothermal synthesis. The MoS2 ultrathin layer was well combined with CdS nanosheets and formed the interaction, which facilitated the transfer and separation of charges. The CdS/MoS2 15 wt% possessed much higher H2 evolution photocatalytic performance (35.24 mmol h−1 g−1), exhibiting an 85.95 times enhancement as compared to that of pure CdS (0.41 mmol h−1 g−1). Moreover, the photochemical stability of CdS/MoS2 heterojunctions was excellent, which showed no significant decrease in activity after four cycles of experiments. The finding provides a novel method to integrate the structure of MoS2 with CdS, which exhibits great potential in solar energy conversion.

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.

This communication reports hydrothermal synthesis of molybdenum trioxide (MoO3) with long microsheets morphology and their gas sensing characteristics through clad-modified fiber optic gas sensor technique. Synthesized material is subjected to characterization analysis including XRD, SEM and Raman Spectra. Spectral analysis on the gas sensing characteristics reveal that MoO3 microsheets exhibit good gas response to methanol at room temperature. Gas sensing mechanism is also discussed.

The wide use of manganese dioxide (MnO2) as an electrode in all-solid-state asymmetric supercapacitors (ASCs) remains challenging because of its low electrical conductivity. This complication can be circumvented by introducing trivalent gadolinium (Gd) ions into the MnO2. Herein, we describe the successful hydrothermal synthesis of crystalline Gd-doped MnO2 nanorods with Ni(OH)2 nanosheets as cathode, which we combined with Fe3O4/GO nanospheres as anode for all-solid-state ASCs. Electrochemical tests demonstrate that Gd doping significantly affected the electrochemical activities of the MnO2, which was further enhanced by introducing Ni(OH)2. The GdMnO2/Ni(OH)2 electrode offers sufficient surface electrochemical activity and exhibits excellent specific capacity of 121.8 mA h g−1 at 1 A g−1, appealing rate performance, and ultralong lifetime stability (99.3% retention after 10,000 discharge tests). Furthermore, the GdMnO2/Ni(OH)2//PVA/KOH//Fe3O4/GO solid-state ASC device offers an impressive specific energy density (60.25 W h kg−1) at a high power density (2332 W kg−1). This investigation thus shows its large potential in developing novel approaches to energy storage devices.

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.

Developing environmentally friendly methods to produce hydrogen peroxide (H2O2) has received increasing attention. Photocatalysis has been proved to be a sustainable technology for H2O2 production. Herein, the novel non-metal elements (B, P, and S) doped g-C3N4 tubes (B-CNT, P-CNT, and S-CNT) photocatalysts were obtained via a hydrothermal synthesis followed by thermal polymerization. By adjusting the precursor, the yield of g-C3N4 tubes (CNT) materials has been greatly improved. The as-prepared B-CNT, P-CNT, and S-CNT photocatalysts show an enhanced photocatalytic H2O2 production with the formation rate constants values of 42.31 μM min−1, 24.95 μM min−1, and 24.22 μM min−1, respectively, which is higher than that of bulk CN (16.40 μM min−1). The doped B, P, S elements significantly enhanced the photocatalytic activity by adjusting their electronic structures and promoting the separation of electron-hole carriers. The results have shown great potential for the practical application of CNT photocatalysts.

Supercapacitor with high specific capacity is desirable for various energy storage and high powerdensity applications. Though Graphene has been the preferred material for high current density, nanocomposites have been attempted to increase the specific capacitance. Hydrothermal synthesis of cadmium sulfide/graphene (CdS/G) nanocomposite with CdS nanoparticles anchored/decorated over the graphene sheets is reported. The structural studies reveal the hexagonal phase of the prepared materials. The specific surface area (BET) and porosity is found to increase upon nanocomposite formation. The electrochemical characteristics such as cyclic voltammetry (CV), GCD and EIS of the CdS/G nanocomposite have been investigated. The capacitance of CdS/G nanocomposite almost doubled to 248 Fg−1 indicating the enhanced performance of the nanocomposite system and in addition it also showed excellent cycling stability of 74.8 percent after 1000 cycles. The supercapacitor investigated retained the initial energy density after charge-discharge, at 0.5 A/g for 1000 cycles. The graphene nanosheets increased the specific surface area and interfacial electron transfer of the composite material. It enhances the specific capacitance and cyclic stability of the supercapacitor device.

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.

Advanced oxidation process (AOP) has attracted widespread attention because it can effectively remove antibiotics in water, but its practical engineering application is limited by the problems of the low efficiency and difficult recovery of the catalyst. In the study, nano-spinel CoFe2O4 was prepared by hydrothermal method and served as the peroxymonosulfate (PMS) catalyst to degrade antibiotic amoxicillin (AMX). The reaction parameters such as CoFe2O4 dosage, AMX concentration, and initial pH value were also optimized. The reaction mechanism was proposed through free radical capture experiment and possible degradation pathway analysis. In addition, the magnetic recovery performance and stability of the catalyst were evaluated. Results showed that 85.5% of AMX could be removed within 90 min at optimal conditions. Sulfate radicals and hydroxyl radicals were the active species for AMX degradation. Moreover, the catalyst showed excellent magnetism and stability in the cycle experiment, which has great potential in the AOP treatment of antibiotic polluted wastewater. HIGHLIGHTS Magnetic nano-CoFe2O4 was fabricated by hydrothermal process.; High activity of removing AMX in the CoFe2O4/PMS system.; The recovery of nano-CoFe2O4 was convenient due to strong magnetics.; The nano-CoFe2O4 exhibited good stability and reusability.

NiMoS2 is a promising material for various functional applications and highly compatible with GO to make hybrid nanocomposites with excellent characteristics for supercapacitor electrode material. Deposition of NiMoS2 was achieved on the rGO(reduced Graphene Oxide) surface to form a NiMoS2−rGO nanocomposite by the method of the facile hydrothermal synthesis process. XRD pattern shows the crystalline nature of composites. Raman and EPMA result interpreting the composites formation and elements compositions, respectively. The sheet-like morphology of rGO was found in the composites by FESEM images. Particles distribution was confirmed by HR-TEM. The electrochemical properties of the pure NiMoS2 and NiMoS2–rGO composites have been studied by cyclic voltammetry analysis. The results revealed that the NiMoS2/5% rGO nanocomposites exhibit high specific capacitance compared to pure NiMoS2 due to the synergistic effects of NiMoS2 and rGO in the composite material. The photocatalytic behavior of the prepared nanocomposites for dye degradation was tested. The quantity of rGO has significantly improved the photocatalytic behavior of NiMoS2/rGO composites. The studies on degradation mechanism, the N2 adsorption/desorption isotherms, pore size distribution behavior and % of removal of MB reveal the enhanced photocatalytic performance of sysnthesised composites.

Zeolites are the most used solid catalysts in the chemical industry. The hydrothermal synthesis of these porous aluminosilicate crystals is a multistep process that involves the polymerization of s...

The high energy demand of CO2 absorption-desorption technologies has significantly inhibited their industrial utilization and implementation of the Paris Climate Accord. Catalytic solvent regeneration is of considerable interest due to its low operating temperature and high energy efficiency. Of the catalysts available, heterogeneous catalysts have exhibited relatively poor performances and are hindered by other challenges, which have slowed their large-scale deployment. Herein, we report a facile and eco-friendly approach for synthesizing water-dispersible Fe3O4 nanocatalysts coated with a wide range of amino acids (12 representative molecules) in aqueous media. The acidic properties of water-dispersible nanocatalysts can be easily tuned by introducing different functional groups during the hydrothermal synthesis procedure. We demonstrate that the prepared nanocatalysts can be used in energy-efficient CO2 capture plants with ease-of-use, at very low concentrations (0.1 wt %) and with extra-high efficiencies (up to ∼75% energy reductions). They can be applied in a range of solutions, including amino acids (i.e., short-chain, long-chain, and cyclic) and amines (i.e., primary, tertiary, and primary-tertiary mixture). Considering the superiority of the presented water-dispersible nanocatalysts, this technology is expected to provide a new pathway for the development of energy-efficient CO2 capture technologies.

We developed an improved hexagonal wurtzite ZnO and ZnO/C microflowers through the facile hydrothermal technique. The obtained nanostructures were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), Transmission electron microscopy (TEM), Energy-dispersive X-ray spectroscopy (EDX) and UV–visible diffuse reflectance spectroscopy (UV–Vis DRS). The formation of flower-like material is confirmed using SEM and TEM analysis with an average diameter of about 2 µm composed of several plate-like nanostructures. The optical analysis results show that the presence of carbon particles with ZnO structures has significantly increased the light absorption ability of nanocomposite. The photocatalytic degradation ability of prepared nanostructures was examined using methylene blue as a model pollutant. The obtained results show that the photocatalytic degradation ability of ZnO/C nanostructures is approximately two times higher than the pristine ZnO microflowers. Based on the investigation, an enhancement of the photocatalytic ability of ZnO/C nanocomposite is achieved due to the synergistic effect between carbon particles and flower-like ZnO nanostructures.

Bismuth antimony telluride (Bi0.5Sb1.5Te3) is a ternary compound with good thermoelectric properties at near room temperature. In this research, Bi0.5Sb1.5Te3 powders were hydrothermally synthesized at different temperatures (100, 150, 190, and 230°C) for 24 h. The deposition procedure of Bi0.5Sb1.5Te3 thin films was done by using thermal evaporation. The phases and microstructures of powders and thin films were investigated by x-ray diffraction and field emission scanning electron microscopy. Moreover, the size distribution of powders was investigated using a particle size analyzer. The phase and microstructural results of the different synthesized powders confirmed that the Bi0.5Sb1.5Te3 thin film prepared by powder synthesis at 150°C for 24 h is the best choice for manufacturing with good thermoelectric properties because of its nano-sized grains and high purity. The results showed that the Bi0.5Sb1.5Te3 thin film fabricated by powders synthesized at 150°C has a single rhombohedral phase with a good semiconductor performance. The results of thermoelectric tests confirmed that the Bi0.5Sb1.5Te3 thin film fabricated using a hydrothermal method and thermal evaporation deposition approach shows a high Seebeck coefficient (183.5 μV/K) and low electronic thermal conductivity (1.32 × 10−4 W/m k−1) at 298 K. Besides, the power factor values of 0.7, 2.59 and 2.9 μW/cm K−2 were obtained at 298, 373 K and 473 K, respectively.

The WO3 is a promising photoanode material for photoelectrochemical (PEC) water oxidation. Loading co-catalysts is an effective strategy for favoring the charge transfer and light harvesting of WO3, which can in turn improve its PEC performance. Herein, the ferrihydrite (Fh), a kind of poorly crystalline iron oxide material, was loaded on the WO3 photoanode through a two-step hydrothermal synthesis. The obtained Fh/WO3 photoanode exhibited a remarkable photocurrent density of 0.6 mA/cm2 at 1.23 V (vs. RHE), which was 1.79 times higher than the bare WO3. For the Fh/WO3 photoanode, the bulk charge separation efficiency is 45.6% and the photoconversion efficiency is 0.066%, which are both higher than the bare WO3. The decorated Fh can form an additional interface between the WO3 and the electrolyte, which decreases the impedance and favors the charge transfer. Moreover, the Fh can function as a hole storage layer, which can temporarily store the photogenerated holes and induce the longer lifetime of charge carriers, thus improving the charge separation and water oxidation reaction kinetics.

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. ...

It is well known that the intelligent hybridization of active materials and the controllable recombination of nanostructures can significantly improve the electrochemical performance of pseudocapacitor electrodes. In this work, a NiO/NiCo2O4 needle/sphere nanostructure was synthesized on the hydrochloric acid-activated Nickel foam by a simple hydrothermal method and measured the performance of it as an electrode material for supercapacitors. Field emission scanning electron microscope, transmission electron microscope, X-ray diffraction, and X-ray photoelectron spectroscopy were used to characterize the morphology and composition of the samples. The electrodes display a prominent specific capacitance (2447 F/g at the ampere density of 2 A/g) and remarkable cycling stability (85.2% capacity remained after 3000 cycles), owing to the unique needle/sphere composite architecture and the rational combination of active materials. The results demonstrate that the three-dimensional composite structure of NiO/NiCo2O4 nanomaterials provides a large specific surface area for the electrode, which promotes the penetration of electrolyte ions and the transmission of electrons. This novel structured material will be promising in the application of supercapacitor electrode materials.