Mild Hydrothermal Method Research Articles

Synthesis and crystal structure of a Mn-based coordination complex as precursor for the synthesis of Mn2O3

A new Mn(II) complex with the formula [Mn2(H2O)(phen)4(seb)2]·4.5H2O (phen: 1,10-phenanthroline; H2seb: sebacic acid), (complex 1), was synthesized using a mild hydrothermal method. The structure of complex 1 was studied using powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDS), single crystal X-ray diffraction (SXRD) analysis, thermogravimetric analysis (TGA), and Fourier infrared spectroscopy (FTIR). Mn2O3 was obtained by calcination of complex 1 at 850 °C in air and its pure phase was confirmed by PXRD analysis. The electrochemical performance of Mn2O3 as a material for the negative electrode used in lithium ion batteries (Lib) shows a specific charge and discharge capacity of 377.7 and 798.6 mAh/g, as was observed at the first cycle. The charge and discharge capacity were approximately 168.1 and 168.4 mAh/g after 100 cycles. The above capacities are repeatable and demonstrate the good structural stability of Mn2O3 under applied electric power.

LaCO3OH improving photocatalytic activity of In(OH)3/In2S3 heterostructures

Lanthanum hydroxycarbonate (LaCO3OH), a kind of fluorescence materials, was less studied in application for photocatalysis. In this paper, LaCO3OH/In(OH)3/In2S3 (LCO/IO/IS) heterostructures were firstly synthesized by a mild two-step hydrothermal method and investigated by various technologies. The activity of as-prepared samples was evaluated by the degradation of Rhodamine B (RhB) under visible light ([Formula: see text][Formula: see text]nm). When the content of LaCO3OH is 15[Formula: see text]mol.% (La/In), the obtained sample exhibits the highest performance, beyond two times as high as that of In(OH)3/In2S3. The improved photodegradation activity might be ascribed to higher adsorption capability and photosensitization of RhB due to proper energy structures of the heterostructures, which prompts the effective separation of electrons and holes. This work extends the application of rear earth salts (lanthanum hydroxycarbonate) for purification of dye waste water.

Boosted visible-light photocatalytic performance of TiO2-x decorated by BiOI and AgBr nanoparticles

The prominent visible-light-responsive TiO2-x/BiOI/AgBr photocatalysts with p-n-n heterojunctions were synthesized via a mild hydrothermal method, followed by precipitation approach at room temperature. All of the obtained results illustrated that the ternary TiO2-x/BiOI/AgBr nanocomposites act as a highly efficient photocatalysts for different dyes decomposition compared to the TiO2, TiO2-x, and TiO2-x/BiOI photocatalysts. The remarkable visible light photocatalytic performance for the TiO2-x/BiOI/AgBr photocatalysts is ascribed to striking visible-light absorption capability, plenteous active sites, and reinforced charge separation repressed by p-n-n heterojunctions, which were evidenced by optical, textural, and photoelectrochemical characterizations. The TiO2-x/BiOI/AgBr (10%) photocatalyst with considerable reusability exhibited substantial visible-light photoactivity towards RhB, MB, and fuchsine degradations, in which RhB, MB, and fuchsine degradation percentages are 98% (at 60 min), 99% (at 300 min), and 76% (at 300 min), respectively. Additionally, the results of quenching tests suggested that holes and superoxide radicals have a notable character in the degradation process. The strategy to construct these multi-heterojunction photocatalysts can give an innovative perspective to design highly efficient systems for solving environmental pollution crisis using TiO2 under visible light.

Influence of graphene surface chemistry on Ir-catalyzed hydrogenation of p-chloronitrobenzene and cinnamaldehyde: Weak molecule-support interactions

Graphene is an ideal model support to investigate the influence of carbon surface chemistry on catalytic reactions. Here a mild hydrothermal method was developed to synthesize graphene-supported iridium nanocatalysts from graphene oxide. By simply varying the hydrothermal conditions, the physicochemical properties of catalysts can be tuned, which can further affect their catalytic performances. Catalysts obtained at higher H2 pressure during hydrothermal process performed higher catalytic activities for hydrogenation of both p-chloronitrobenzene and cinnamaldehyde, benefiting from their higher reduction degrees of iridium nanoparticles. Interestingly, catalysts obtained at lower hydrothermal temperature performed higher activities for p-chloronitrobenzene hydrogenation but lower activities for cinnamaldehyde hydrogenation, due to their distinct surface chemistry of graphene. Through systematic characterizations on 11 catalysts prepared under various conditions, we found that lower hydrothermal temperature endows graphene with larger lateral dimension and more in-plane oxygenated surface groups, which facilitates the accessibility of nitro groups to catalyst surface via H-bond interaction as confirmed by density functional theory calculations. This is not true for cinnamaldehyde, of which adsorption on graphene via π-π stacking interaction is favorable for its hydrogenation.

Morphologically confined hybridization of tiny CoNi2S4 nanosheets into S, P co-doped graphene leading to enhanced pseudocapacitance and rate capability

The transition metal hydroxides/sulfides have been regarded as novel high-efficient electrode materials due to its superior Faradic activity. However, the aggregation problem and poor rate performance severely hinder the practical application in supercapacitors. Herein, morphologically confined hybridization of tiny CoNi2S4 nanosheets into S, P co-doped graphene (DGNCS) is designed and fabricated from NiCo-OH precursor (NCO) nanowires via a mild multi-step hydrothermal method and sulfofication. The S, P co-doped graphene (DG) serves as the conductive pathway and skeleton support and provides abundant coordination atoms to preventtheaggregation and improve the structural stability. The CoNi2S4 nanosheets serves as the main active components and provides abundant active sites to enhance the electrochemical performance. Owing to the synergistic effect of each components, the as-prepared DGNCS electrode delivers a specific capacitance of 1136.5 F g−1 (126.28 mAh g−1) at 2 A g−1 and a satisfactory capacitance retention of 70.1% after 5000 cycles at 15 A g−1. In addition, the rate performance of DGNCS (38.58%) increased by 2.44 times compared with the pure NCS (CoNi2S4). Furthermore, the fabricated asymmetric supercapacitor (ASC) device assembled with active graphene and the as-obtained DGNCS achieves a maximum energy density of 25.62 Wh kg−1 and an outstanding power density of 8000 W kg−1. Moreover, the ASC device shows an excellent cycling stability of 86.49% capacitance retention after 5000 cycling at 5 A g−1. Outstanding electrochemical performance confirms the effectiveness of the fabricating strategy, providing a new pathway for further design of a novel composite electrode for next generation energy storage devices.

Fabrication of highly visible active N, S co-doped TiO2@MoS2 heterojunction with synergistic effect for photocatalytic degradation of diclofenac: Mechanisms, modeling and degradation pathway

In this study, N,S co-doped TiO2@MoS2 nanocomposite were fabricated via a mild and effective hydrothermal method. The structural features and morphologies of nanocomposite were studied in detail by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray analysis, (high resolution) transmission electron microscopy, X-ray photoelectron spectroscopy and UV–vis spectroscopy techniques. The results indicated that nitrogen and sulfur were successfully doped as interstitial doping in TiO2 lattices and simultaneously coupled with MoS2 to form the heterojunction nanostructure. The photocatalytic activity of N,S co-doped TiO2@MoS2 nanocomposite for diclofenac removal under visible LED light irradiation shows 5.0 times and 4.0 times higher than that of MoS2 and N,S co-doped TiO2, respectively. The kinetic model, effect of operational parameters (i.e. pH, catalyst dose, initial pollutant concentration) and mechanism for increasing visible-light photocatalytic activity of the heterostructure nanocomposite is discussed in detail. After six times cycle degradation of diclofenac the N,S co-doped TiO2@MoS2 nanocomposite exhibited steady photoactivity. This work introduces a highly-efficient heterostructure nanocomposite and a research pathway to evaluate the photocatalyst in shorter time which can help to design the system for the environmental pollution purification under sunlight irradiation.

Highly Polarizable Hg2+ Induced a Strong Second Harmonic Generation Signal and Large Birefringence in LiHgPO4.

A new ultraviolet nonlinear optical material, namely LiHgPO4, was synthesized using the mild hydrothermal method. The structure of LiHgPO4 features novel double layers constructed by severely distorted HgO6 octahedra and PO4 tetrahedra, which are further interconnected by LiO4 tetrahedra to form a three-dimensional structure. LiHgPO4 exhibits a very strong second harmonic generation (SHG) response of 11.0 times that of KH2PO4 and a relatively large birefringence (0.068 at 1064 nm) among the reported SHG-active phosphates. Theoretical calculations revealed that the introduction of the Hg2+ in a highly distorted HgO6 octahedral geometry is crucial to produce the strong SHG response and large birefringence.

Effect of annealing temperature on morphology and physicochemical properties of cornstarch complexed with oleic acid and molecular dynamics simulation

AbstractBackground and objectivesAnnealing treatment (ANN) as a mild hydrothermal method to improve the complexation between starch and lipids has scarcely been studied. Moreover, the mechanism of starch pretreated by ANN on the complexation between starch and fatty acid still has not been investigated. Therefore, the object of this research was to investigate the effect of ANN pretreatment temperature (50, 55, and 60°C) on the morphology, crystal structure, and thermal properties of CSANN‐OA complex by using confocal laser scanning microscope (CLSM), X‐ray diffraction (XRD), and DSC. The mechanism of the complexation between starch and OA was simulated by the molecular dynamics simulation (MDS) method.FindingsThe results of complex indexes (CI) indicated that CSANN was easier to complex with OA than CSU, and the optimal ANN pretreatment temperature to promote the complexation between CSANN and OA was 50°C. The CLSM displayed that ANN pretreatment at 50°C caused more and stronger fluorescence fragments in CSANN‐OA than that of ANN pretreatment at 55 or 60°C. XRD of both CSU‐OA and CSANN‐OA changed to V‐type crystalline. The relative crystallinity (RC) and gelatinization enthalpy (ΔH) of the complex were decreased with increasing ANN pretreatment temperature, but the gelatinization temperature range (Tc–To) remains unchanged. According to results of MDS, Van der Waals might be dominate driving force between AM and OA.ConclusionsThese results suggest that ANN pretreatment is an effective method to promote the complexation of ANN starch with more polar or nonpolar components.Significance and noveltyThis result can provide available information about the complexation effect and complexation mechanism between starch subjected to ANN pretreatment and fatty acid.

Carbonate-intercalated defective bismuth tungstate for efficiently photocatalytic NO removal and promotion mechanism study

Synthesis of high-efficiency photocatalysts and revealing the photocatalytic mechanism are of far-reaching significance for its commercial applications. Therefore, we design and favorably fabricate the carbonate intercalated Bi2WO6 with oxygen vacancies via employing a mild hydrothermal method with ethylene glycol assist. The prepared catalysts exhibit an excellent photocatalytic NO oxidation activity under visible light irradiation, attributing to the inserted carbonate coupled with oxygen vacancies. Additionally, the promotion mechanism and reaction pathway of photocatalytic NO removal are carefully discussed by experimental detection assisted with density functional theory (DFT) calculation. Our results explicitly reveal that the carbonate coupled with oxygen vacancies can remarkably retard the recombination of electro-hole pairs, and improve the carriers transforming to activity species. The reactants would be easily activated and converted over the carbonate-intercalated defective Bi2WO6 surface, such as the H2O provided electrons to form OH and O2 accepted electrons to generate O2−, which are certified by utilizing DFT simulation to calculate adsorption of reactants on the surface. In addition, the in situ DRIFTS spectra was used to dynamic analyze the photocatalytic NO oxidation process and reveal the promotion mechanism. Finally, the synthesis strategy and mechanism analysis would possess guiding significance for improving photocatalytic efficiency and applications.

Hollow Co2SiO4 microcube with amorphous structure as anode material for construction of high performance lithium ion battery

To solve the problem of large volume expansion of cobalt silicate electrode during cyclic process and low electric conductivity, Co2SiO4 with amorphous, porous and hollow structure is firstly designed to act as high performance lithium ion battery (LIB) anode. Compared with crystalline materials, the amorphous Co2SiO4 microcube could facilitate Li+ diffusion to enhance their performance of LIBs because of isotropic characteristics. Here, the amorphous Co2SiO4 hollow microcube (named as a-Co2SiO4 HC) was prepared by mild hydrothermal method with use of MnCO3 microcube as hard-template. Benefitting from the advantages of such structure, Li+ diffusion rate was greatly accelerated and the volume expansion can be alleviated. The as-prepared amorphous Co2SiO4 hollow microcube as anode material of LIBs exhibited significantly improved electrochemical performance of 610 mAh g−1 even after 380 cycles at 500 mAh g−1 than their crystalline counterpart (only 280 mAh g−1 retained after 380 cycles). This work is a good try to employ amorphous metal silicate in LIBs and simultaneously motivate the exploration of other amorphous materials for high performance LIBs, SIBs, catalysts, etc.

Controllable Zn0.76Co0.24S Nanoflower Arrays Grown on Carbon Fiber Papers for High-Performance Supercapacitors

A nanoflower structure of Zn[Formula: see text]Co[Formula: see text]S directly grown on carbon fiber papers (CFP) was successfully designed by a mild two-step hydrothermal method. Benefiting from their fascinating structural features, Zn[Formula: see text]Co[Formula: see text]S/CFP electrode exhibits a maximum specific capacitance of 300[Formula: see text]F[Formula: see text]g[Formula: see text] at current density of 1[Formula: see text]A[Formula: see text]g[Formula: see text] and 84% capacitance retention after 5,000 cycles at current density of 5[Formula: see text]A[Formula: see text]g[Formula: see text]. Subsequently, Zn[Formula: see text]Co[Formula: see text]S/CFP//AC all-solid-state asymmetric supercapacitor (ASC) device is assembled and able to illuminate the red LEDs. ASC devices deliver a maximum energy density of 9.59[Formula: see text]W[Formula: see text]h[Formula: see text]kg[Formula: see text] at a power density of 750[Formula: see text]W[Formula: see text]kg[Formula: see text]. Therefore, this impressive result demonstrates that the nanoflower Zn[Formula: see text]Co[Formula: see text]S have promising applications in the development of high-performance supercapacitors.

Microwave solvothermal carboxymethyl chitosan templated synthesis of TiO2/ZrO2 composites toward enhanced photocatalytic degradation of Rhodamine B

A series of TiO2/ZrO2 composites with various molar ratios of ZrO2:TiO2 were synthesized by a facile and mild microwave hydrothermal method with carboxymethyl chitosan (CMCS) as templates. The as-obtained products were characterized with wide-angle powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FTIR), UV–vis diffuse reflectance spectrophotometry (UV–vis-DRS), N2 adsorption-desorption isotherms (BET), and X-ray photoelectron spectrometer (XPS). The TiO2/ZrO2 composites with heterogeneous structure consisted of particles which showed a better regularity and uniform with about 800 nm in diameter, and showed a larger specific surface area and smaller energy band gap than pure ZrO2. Comparative experiments including varying the pH of the solution and the content of titania demonstrated that the 5% TiO2/ZrO2 composites (nTi:nZr = 5:100) at pH = 10.3 possessed the best photocatalytic property. Moreover, the possible reasons for these phenomena were clarified. Cyclic experiments proved that the resulting TiO2/ZrO2 composites as photocatalyst could be reused efficiently. Meanwhile, a possible mechanism of photocatalysis was proposed.

Combined effects of interface modification and nano‐reinforcement via nano‐enhanced interphase in hybrid‐fabric composites for tribological applications

Hybrid Nomex/PTFE (Polytetrafluoroethylene) fabric composites have demonstrated sufficient potential in tribological field due to their prominent mechanical and self‐lubricating capabilities. However, the poor fabric‐matrix interfacial adhesion and weak bonding of transfer‐film to counterface are still the bottlenecks for practical applications of these materials. Herein, growth of ZnO nanowires onto the surface of hybrid Nomex/PTFE fabric based on air‐plasma treatment was developed, aiming at enhancing the fabric‐matrix interfacial performance using a mild hydrothermal method. Mechanical testing showed significant improvement in the interfacial adhesion strength, while retaining the full mechanical strength and flexibility of pristine hybrid‐fabric. More importantly, the ZnO nanowires, released onto the interface during sliding process, participated in the tribo‐physical actions contributing to the formation of a uniform and tenacious transfer‐film. It is thought, therefore, that the ZnO‐enhanced interphase has the dual effects of interface modification and nano‐reinforcement of transfer‐film. As a result, the tribological performance of hybrid‐fabric–ZnO nanowires composites presented a considerable enhancement under varied load conditions. POLYM. COMPOS., 40:3383–3392, 2019. © 2019 Society of Plastics Engineers

Soft-templating and hydrothermal synthesis of NiCo2O4 nanomaterials on Ni foam for high-performance supercapacitors

Nickel cobalt oxide (NiCo2O4) was successfully grown on the nickel foam by a mild hydrothermal method combined with a simple annealing treatment, utilizing SDS, PVP, CTAB, and PVA as template agents. The effect of different template agents on the morphology and electrochemical performance of NiCo2O4 electrode for supercapacitor was further investigated in detail. The physicochemical properties of the NiCo2O4 materials were examined via the X-ray diffraction and the scanning electron microscopy. It could be seen from the XRD patterns that there were no other clear clutter peaks, which indicated that the purity of the material was relatively high. As shown by the SEM diagram, the prepared NiCo2O4 showed different morphology structures via the addition of the template agent, which exhibited high capacitance and cycling stability. Specially, the NiCo2O4 electrode with the usage of 0.75 g SDS, PVP, CTAB, PVA, and none template agents showed high capacitance of 1357, 1469, 1290.6, 1297.4, and 863.8 F g−1 at 1 A g−1. In addition, asymmetric supercapacitors (ASC) were assembled with the brilliant binary oxides as the positive electrode, activated carbon as negative electrode, and 6 mol/L KOH solution as electrolyte. The ASC device demonstrated a high energy density of 64.76 Wh kg−1 at a power density of 774.8 W kg−1. Remarkably, it still displayed desirable cycle retention of 84.39% over 5000 cycle numbers at a current density of 10 A g−1, and the excellent electrochemical performance suggested its potential application in electrode material for supercapacitor.

Utilizing an In Situ Reduction in the Synthesis of BaMoOF5

A new molybdenum containing oxyfluoride, BaMoOF5, space group Cmcm with lattice parameters of a = 7.1445(3), b = 6.7894(3), c = 10.1969(4), was synthesized via a mild hydrothermal crystal growth method. The synthesis resulted in high-quality single crystals of the title material, which were characterized by single-crystal X-ray diffraction. The structure is discussed in detail. A new Mo(V) oxyfluoride, BaMoOF5, was synthesized via a mild hydrothermal route that included an in-situ reduction step to reduce molybdenum from a starting oxidation state of 6+ to 5+.

K2[B4O5(OH)4]·H2O and K2[B4O5(OH)4]: two new hydrated potassium borates with isolated [B4O5(OH)4]2−units and different structural frameworks

Two new hydrated potassium tetraborates with isolated [B4O5(OH)4]2−units were obtainedviaa mild hydrothermal method.

Synthesis and characterization of La- and Ce-codoped polycrystal ZnO prepared by hydrothermal method for 1,2-propanediol

La/Ce-codoped ZnO (La/Ce–ZnO)-based gas sensors are successfully prepared by a simple mild hydrothermal method. And the structures, morphologies and sensing properties are examined by XRD, SEM and XPS, respectively. The 1,2-propanediol gas-sensing analysis reveals that the La/Ce–ZnO-based gas sensor displays the highest response compared with La-doped ZnO and Ce-doped ZnO sensors. La/Ce–ZnO-based gas sensor exhibits an excellent response (681) and possesses good response and recovery property of 11 and 45 s to 100 ppm 1,2-propanediol at 240 °C, respectively. The mechanism of gas sensing and enhanced gas response of La/Ce–ZnO is discussed.

Designing of nickel cobalt molybdate/multiwalled carbon nanotube composites for suppression of electromagnetic radiation

One-dimensional nanorod structures of cobalt molybdate, nickel cobalt molybdate and nickel cobalt molybdate/multiwalled carbon nanotube composites have been effectively synthesized by mild hydrothermal method. The elemental analysis of prepared composite nanorods is studied by Fourier transform infrared and electron diffraction X-ray spectroscopy. Structures and morphologies of samples are characterized by X-ray diffraction and field emission scanning electron microscope. SEM morphology authenticates the development of nanorod structures of synthesized samples. The particles’ size attained by CoMoO4, NiCoMoO4 and NiCoMoO4/CNTs from SEM morphology is in the range of 45–65 nm, 75–85 nm and 100–125 nm. It is experiential that after Ni doping in CoMoO4 particle size is increased and constituent parts are transformed into consistent dimension with better morphology. The SEM image of NiCoMoO4/CNTs shows the thread-like structures that reveal the presence of carbon nanotubes in the composite. EMI shielding measurements were taken using pressed rectangular pellets of 2 mm thickness. The measured total electromagnetic interference (EMI) shielding efficiency (~ SET) of NiCoMoO4/CNTs is 48.84 dB in the Ku band (12.4–18.0 GHz), and involvement of SE due to the absorption of total EMI SE of the composite is larger than that of reflection. This is due to the development of strong conducting network through MWCNTs within divalent transition metal-doped metal–metal matrix. The obtained results suggest the usefulness of the composite for commercial use in far-field EMI shielding and suppression of electromagnetic radiation.

Preparation of amino-functionalized magnetic biochar with excellent adsorption performance for Cr(VI) by a mild one-step hydrothermal method from peanut hull

Amino-functionalized magnetic biochar from wasted peanut hull (MPHC-HDA) with excellent adsorption properties for Cr(VI) was successfully prepared by a mild one-step hydrothermal method in the presence of iron chloride and hexamethylenediamine (HDA). The physicochemical properties of the peanut hull based biochar (PHC), HDA-modified PHC (PHC-HDA) and MPHC-HDA were comparatively characterized by XRD, SEM, FT-IR, VSM, N2 adsorption/desorption and XPS. Static adsorption experiments show that MPHC-HDA presents the maximum adsorption capacity of 142.86 mg g−1 among them; this adsorption follows pseudo-second-order kinetics model and Langmuir isotherm. Furthermore, MPHC-HDA with easily separated characteristic after adsorption can also be recycled for three times. Importantly, this method can be extended to other renewable wasted bioresource including sunflower seed shell, pumpkin seed shell, corncob, etc., indicating it has great potentiality in the field of wastewater treatment.

Energy‐Band‐Controlling Strategy to Construct Novel CdxIn1‐xS Solid Solution for Durable Visible Light Photocatalytic Hydrogen Sulfide Splitting

Photocatalytic waste hydrogen sulfide (H2S) conversion into clean energy (H2) has an alluring prospect. Herein, a series of novel CdxIn1‐xS solid solutions are constructed by a mild hydrothermal method for visible light photocatalytic H2S splitting. The CdxIn1‐xS solid solutions with an orderly tuned visible‐light response range from 550 to 600 nm present a more positive valence band (VB) position and remarkable separation ability of charge carriers. As a result, the optimized cubic CdxIn1‐xS solid solution casts the extraordinary photocatalytic H2 evolution rate (16.35 mmol g−1 h−1) from H2S, which is 5‐ and 23‐fold higher than that over bare CdS (3.40 mmol g−1 h−1) and β‐In2S3 (0.72 mmol g−1 h−1), respectively, exceeding previous CdS‐based photocatalysts in the absence of co‐catalysts. The corresponding quantum efficiency (QE) at 420 nm is 26.7%. The combination of experiment and density functional theory (DFT) calculation confirms that the formation of CdxIn1‐xS solid solution has three functions for H2S splitting: i) improving anti‐photocorrosion properties of CdS‐based catalytsts; ii) promoting the further oxidation of sulfur (S) adsorbed on the catalyst surface; and iii) enhancing the charge‐separation efficiency. This work reports a novel CdxIn1‐xS solid solution for highly efficient photocatalytic H2 generation from H2S under visible light irradiation.