Facile Hydrothermal Synthesis Route Research Articles

Constructing a novel Bi2MoO6/TiO2/Ti3C2 composite with efficient carrier separation for excellent photocatalytic purification of TC

Photocatalytic removal of tetracycline (TC) from wastewater is an advantageous method with green and efficient potentials, while the low light utilization and severe charge carrier recombination of conventional photocatalysts limit their practical application. The TiO2/Ti3C2 derived from in-situ partly oxidation of Ti3C2 MXene precursors on which Bi2MoO6 (BMO) was tightly loaded was synthesized via a facile hydrothermal synthesis route. The introducing TiO2/Ti3C2 accelerated the transfer of electrons, improving the efficiency of electron-hole separation, thus strengthened the photocatalytic performance. Under optimum conditions, the BMO/TiO2/Ti3C2 composite significantly removed 87.54 % TC from wastewater within 150 min, which was higher than the original counterparts and remained almost unchanged after four cycles. The active species trapping experiments and ESR analysis displayed that •O2- played a dominant role in TC degradation. The possible degradation pathways were also deduced through liquid chromatography-mass spectrometry (LC-MS) analysis experiments, demonstrating that the terminal products of degradation were mainly CO2 and H2O, confirming the potential of BMO/TiO2/Ti3C2 photocatalyst for the environmentally friendly treatment of antibiotic pollutants in wastewater.

Formation Mechanism and Hydrothermal Synthesis of Highly Active Ir1-xRuxO2 Nanoparticles for the Oxygen Evolution Reaction.

Iridium dioxide (IrO2), ruthenium dioxide (RuO2), and their solid solutions (Ir1-xRuxO2) are very active electrocatalysts for the oxygen evolution reaction (OER). Efficient and facile synthesis of nanosized crystallites of these materials is of high significance for electrocatalytic applications for converting green energy to fuels (power-to-X). Here, we use in situ X-ray scattering to examine reaction conditions for different Ir and Ru precursors resulting in the development of a simple hydrothermal synthesis route using IrCl3 and KRuO4 to obtain homogeneous phase-pure Ir1-xRuxO2 nanocrystals. The solid solution nanocrystals can be obtained with a tunable composition of 0.2 < x < 1.0 and with ultra-small coherently scattering crystalline domains estimated from 1.3 to 2.6 nm in diameter based on PDF refinements. The in situ X-ray scattering data reveal a two-step formation mechanism, which involves the initial loss of chloride ligands followed by the formation of metal-oxygen octahedra clusters containing both Ir and Ru. These octahedra assemble with time resulting in long-range order resembling the rutile structure. The mixing of the metals on the atomic scale during the crystal formation presumably allows the formation of the solid solution rather than heterogeneous mixtures. The size of the final nanocrystals can be controlled by tuning the synthesis temperature. The facile hydrothermal synthesis route provides ultra-small nanoparticles with activity toward the OER in acidic electrolytes comparable to the best in the literature, and the optimal material composition very favorably combines low overpotential, high mass activity, and increased stability.

Strongly coupled design of zinc oxide-nanorods/copper tin sulfide-nanoflowers nanostructures: An electrochemical study in 4-nitrochlorobenzene detection

Developing efficient electrode materials for detecting 4-nitrochlorobenzene (4-NCB) is highly desirable for living organisms and environmental safety. Herein, we designed a hierarchical 1D-2D nanostructure of zinc oxide nanorods@copper tin sulfide nanoflowers (ZnO-NRs@CTS-NFs) by a facile hydrothermal synthesis route for electrochemical detection of 4-NCB. The ZnO-NRs@CTS-NFs modified glassy carbon electrode (GCE) exhibits excellent electrocatalytic performance for 4-NCB, much higher than that of bare GCE, ZnO-NRs/GCE, and CTS-NFs/GCE. Such a desirable electrocatalytic performance is attributed to the large surface area, rich active sites, fast electron transfer through local pn junctions of CTS NFs on ZnO NRs, and the synergistic effect of the as-prepared ZnO-NRs@CTS-NFs nanocomposite. Under optimum conditions, the fabricated ZnO-NRs@CTS-NFs/GCE provides a trace-level detection limit with a wide detection range and high sensitivity. Besides, the fabricated electrochemical sensor displays good selectivity and reproducibility for 4-NCB detection. The practical application of the ZnO-NRs@CTS-NFs modified GCE exhibits satisfactory results in determining 4-NCB in river water, pond water, and industrial wastewater. These results demonstrate that the as-prepared ZnO-NRs@CTS-NFs nanostructures might be one of the most promising electrode materials for 4-NCB detection.

Synthesis and photocatalytic performance of CoMoO4/MoO3 composite for wastewater treatment

Wastewater treatment is becoming severe issue owe to use of different dyes at commercial level in industries. In search of a suitable photocatalyst such as to degrade these dyes, we have developed CoMoO4/MoO3 composites by varying 1–4 wt% of CoMoO4 and adopting a facile hydrothermal synthesis route. The crystalline and structural investigations of as obtained products were done with the help of XRD spectroscopic tool. The morphological features along with elemental composition were probed by SEM and TEM microscopic tools. To observe the optical band gap structure, a UV–vis spectroscopy was employed, which has explored that the band gap of 3% CoMoO4/MoO3 composite was 2.50 eV which was lesser than pure and other composites. The emission properties and electrons-holes recombination kinetics were studied by PL spectroscopic tool and the as optimized 3 wt% composite sample has offered the lowest recombination rate. For the wastewater treatment, the photodegradation of a model dye i.e methyl orange was observed over the course of contact time with the catalyst and the photocatalytic efficiency of pure MoO3 was compared with 1–4 wt% CoMoO4/MoO3 nanocomposites. This photocatalytic efficiency of the 3% CoMoO4/MoO3 composite turn out to be 92%. Besides, this optimized composite material has exhibited a superior degradation stability i.e 83% even after 5 degradation rounds against methyl orange. Furthermore, the as optimized composite has offered 10 times enhanced rate constant (k) than pure MoO3. These characterizations have shown that this excellent increase in the photocatalytic degradation performance is owe to the formation of p-n junction heterostructure, which led to the successful separation of charge carriers and also owe to the increase in surface area hence increasing the active sites for the reduction of dye molecules. Results also have shown the extended visible light response of the catalyst, hence its performance has been further boosting in visible light region.

A NiS2/C composite as an innovative anode material for sodium-ion batteries: ex situ XANES and EXAFS studies to investigate the sodium storage mechanism.

The successful deployment of sodium-ion batteries (SIBs) requires high-performance sustainable and cost-effective anode materials having a high current density. In this regard, sodium disulphide (NiS2) has been prepared as a composite with activated carbon (C) using a facile hydrothermal synthesis route in the past. The X-ray diffraction pattern of the as-prepared NiS2/C composite material shows well-defined diffraction peaks of NiS2. Most carbonaceous materials are amorphous, and the Brunauer-Emmett-Teller (BET) study shows that the surface area is close to 148 m2 g-1. At a current density of 50 mA g-1, the NiS2/C composite exhibits a high capacity of 480 mA h g-1 during the initial cycle, which subsequently decreases to 333 mA h g-1 after the completion of the 100th cycle. The NiS2/C composite electrode provides an exceptional rate capability by delivering a capacity of 270 mA h g-1 at a high current density of 2000 mA g-1, suggesting the suitability of the NiS2/C composite for SIBs. Ex situ X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) analyses at the Ni K-edge have been used to examine the type of chemical bonding present in the anode and also how it changes during electrochemical redox cycling. The understanding of the sodium storage mechanism is improved by the favorable results, which also offer insights for developing high-performance electrode materials for rechargeable SIBs.

2H-MoS2 as an electrode material for oxygen reduction reaction and supercapacitor applications

Molybdenum Disulfide (MoS2) is a two-dimensional material having hexagonal crystal structure, which is widely used as a catalyst in various electrochemical reactions. In the present work, 2H-MoS2 nano-structures are synthesized in the exfoliated form by a facile hydrothermal synthesis route and are studied as electrode material for electrochemical devices. Formation of 2H-MoS2 phase has been confirmed by XRD and is also supported by the presence of E12g and A1g bands in Raman spectroscopy which appears due to the formation of layered MoS2 sheets. The FESEM images show MoS2 sheets in the form of flower-like microstructures. The ORR limiting current density obtained from polarization curves is 3.51 mA/cm2 at 2400 rpm with an onset potential of 0.06 V vs RHE. The specific capacitance of 2H-MoS2 as determined from CV and GCD are 115.42 F/g (at a scan rate of 10 mV/s) and 57.69 F/g (at current density 0.5 A/g) respectively and the samples retain 71.5 % of specific capacitance after 5000 CV cycles. The sample exhibited an electrochemical double layer capacitive (EDLC) behavior with partial pseudo-capacitance. The results suggest that the MoS2-based materials are potential candidates as electrodes in the electrochemical devices.

Scheelite-type rare earth vanadates TVO4 (T = Ho, Y, Dy) electrocatalysts: Investigation and comparison of T site variations towards bifunctional electrochemical sensing application

In the wake of the recent COVID-19 pandemic, antibiotics are now being used in unprecedented quantities across the globe, raising major concerns regarding pharmaceutical pollution and antimicrobial resistance (AMR). In view of the incoming tide of alarming apprehensions regarding their aftermath, it is critical to investigatecontrol strategies that can halt their spread. Rare earth vanadates notable for their fundamental and technological significance are increasingly being used as electrochemical probes for the precise quantification of various pharmaceutical compounds. However, a comprehensive study of the role of the cationic site in tailoring the response mechanism is relatively unexplored. Hence, in this work we present a facile hydrothermal synthesis route of rare earth vanadates TVO4 (T = Ho, Y, Dy) as efficient electrocatalyst for the simultaneous detection of nitrofurazone (NF) and roxarsone (RX). There appears to be a significant correlation between T site substitution, morphological and the electrochemical properties of rare earth metal based vanadates. Following a comparative study of the electrochemical activity, the three rare-earth vanadates were found to respond differently depending on their composition of T sites. The results demonstrate that Dy-based vanadate displays increased electrical conductivity and rapid charge transfer characteristics. Thus, under optimal reaction conditions DyVO4- based electrodes imparts outstanding selectivity towards the detection of NF and RX with an extensive detection window of NF = 0.01–264 µM & RX = 0.01–21 µM and 36–264 µM and low detection limit (0.002, 0.0009 µM for NF and RX, respectively). In real-time samples, the proposed sensor reveals itself to be a reliable electrode material capable of detecting residues such as NF and RX.

Nano-on-micro approach for fabricating ternary metal oxy-hydroxide–based flexible supercapacitors

In the present work, we unveil a facile and effective method to directly grow Ni–Mo–Co oxy-hydroxide–based 3-dimensional hierarchical nanostructures on carbon microfibers (nano-on-micro) by using a facile hydrothermal synthesis route. Further, the electrochemical activity for directly grown fiber electrode as well as electrode formed by slurry coating of active material formed after hydrothermal reaction has been investigated. In this study, the metal ratios (nickel and cobalt) were selected to cover the wide spectrum of the concentration in order to obtain the optimum concentration for the best electrochemical performance. Electrochemical analysis of these ternary metal oxy-hydroxide–based active materials on the carbon microfiber shows significantly high electrochemical activity with a specific capacitance of 519 Fg−1 in hydrothermally activated sample and 890 Fg−1 in a slurry coated sample (at 1 Ag−1). This simple technique provides a novel method to fabricate high energy-storage devices with the advantage of being lighter and flexible and can be easily integrated for various flexible electronic applications potential applications including e-textiles, personal electronics, military apparel devices, and antimicrobial and biomedical textiles.

Coal fly ash supported CoFe2O4 nanocomposites: Synergetic Fenton-like and photocatalytic degradation of methylene blue

Rapid industrialization is causing a serious threat for the environment. Therefore, this research was aimed in developing ceramic cobalt ferrite (CoFe2O4) nanocomposite photocatalyst coated with coal fly ash (CFA-CoFe2O4) using facile hydrothermal synthesis route and their applications against methylene blue. The pristine cobalt ferrite photocatalyst was also prepared, characterized, and applied for efficiency comparison. Prepared photocatalyst were characterized by X-ray diffraction (XRD), fourier transformed infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy with energy dispersive spectroscopy (SEM/EDS). Optical response of catalysts was check using photoluminescence spectroscopy (PL). pH drift method was used for the surface charge characteristics of the material under acidic and basic conditions of solution pH. The photocatalytic degradation potential of all the materials were determined under ultra-violet irradiations. The influencing reaction parameters like pH, catalyst dose, oxidant dose, dye concentration, and irradiation time, were sequentially optimized to obtain best suited conditions. The 99% degradation of 10 ppm methylene blue was achieved within 60 min of reaction time under pH = 5 and 7, catalyst dose = 10 and 12 mg/100 mL, oxidant = 12 mM and 5 mM for cobalt ferrite and CFA-CoFe2O4 photocatalysts, respectively. Afterwards, the radical scavenging experiments were conducted to find out the effective radical scavengers (˙OH, h+, and e−) in photocatalytic degradation process. The kinetic study of the process was done by applying 1st order, 2nd order, and BMG models. Statistical assessment of interaction effect among experimental variables was achieved using response surface methodology (RSM).

Highly selective simultaneous electrochemical detection of trace level of heavy metals in water samples based on the single-crystalline Co3O4 nanocubes modified electrode

This study discussed the simultaneous electrochemical detection of highly toxic Pb2+, Cu2+, Hg2+ heavy metals by the Co3O4 modified electrode. The Co3O4 nanocubes (Co3O4-NC) are prepared by the facile hydrothermal synthesis route which produces highly crystalline particles without an annealing process. The structural properties are characterized by XRD, Raman, XPS, FESEM, and HRTEM analysis. The SAED pattern endorses the single-crystalline nature of Co3O4-NC. The prepared material was subjected to detect the heavy metals electrochemically via DPV techniques. The Co3O4-NC/SPCE revealed good electroanalytical activity towards both individual and simultaneous detection of heavy metals. The developed heavy metal sensor exhibited good sensitivity (16.73 ± 0.8 µA µM−1 cm−2 for Pb2+, 11.46 ± 0.5 µA µM−1 cm−2 for Cu2+, and 16.86 ± 0.7 µA µM−1 cm−2 for Hg2+) and LOD (4.1 ± 0.2, 0.9 ± 0.04, 0.1 ± 0.005 nM for Pb2+, Cu2+, Hg2+, respectively) in the simultaneous detection. Moreover, the Co3O4-NC/SPCE exhibited high selectivity with the other potential interfering metal ions and nitro compounds in tap water and pond water samples. Additionally, the Co3O4-NC/SPCE reveals good recoveries of about 100–101.5% for tap water and 97–101% for pond water samples. Hence, our proposed Co3O4-NC/SPCE is a good electrode material for the determination of toxic heavy metal pollutants in real-time monitoring sensor devices.

Synthesis, characterization and fluorescent performance studies of novel diphenyl sulfone-functionalized water-soluble polymer

In this communication, a novel water-soluble diphenyl sulfone-functionalized polymer was successfully synthesized through a facile hydrothermal synthesis route and then characterized by FT-IR, UV?Vis, 1H-NMR and 13C- -NMR spectroscopy. Fluorescence quenching experiments revealed that the fluorescence intensities of the resulting diphenyl sulfone-functionalized polymers were linear with the concentrations of Fe3+ and 4-nitrophenol (4-NP) in the concentration ranges of (5.0?24.9)?10-8 and (5.0?50.0)?10-7 mol dm-3, with detection limits of 2.8?10-8 and 2.2?10-7 mol dm-3, respectively. These results created opportunities for the development of novel chemosensors by introducing selective fluorescent groups into polymeric materials.

Self‐Supporting CuCo2S4 Microspheres for High‐Performance Flexible Asymmetric Solid‐State Supercapacitors

Copper cobalt sulfide (CuCo2S4) microspheres were grown directly on a carbon cloth (CC) substrate via a facile hydrothermal synthesis route. The possible formation mechanism of flower‐like CuCo2S4 microspheres was also discussed. The resultant composite was explored as a binder‐free electrode for supercapacitors, delivering a high capacitance of 166.67 mAh g–1 at 1 A g–1, excellent rate capability (108.33 mAh g–1 at 10 A g–1) and pronounced long‐term cyclability up to 3000 cycles. A flexible solid state supercapacitor was also assembled with binder‐free electrode materials and exhibits an energy density of 17.12 Wh kg–1 at a power density of 194.4 W kg–1, and a good cycling stability with 78.4 % of initial capacity retention rate can be maintained at 1 A g–1 after 3000 cycles. In addition, the electrochemical performance of supercapacitor device is still quite stable even if it was bent 180° or twisted 150°. Two charged CuCo2S4/CC//AC supercapacitors in series can light 1 red color LED's (2 V) for 5 minutes. All these features indicate that the CuCo2S4/CC device is an excellent candidate for energy storage.

Facile hydrothermal synthesis of the colloidal hierarchical Volborthite (Cu3V2O7(OH)2·2H2O) hollow sphere phosphors

Colloidal hierarchical self-assembled Cu3V2O7(OH)2·2H2O hollow spheres were synthesized using a facile hydrothermal synthesis route without using PS hollow sphere template. Powder x-ray diffraction (XRD) of the obtained Cu3V2O7(OH)2·2H2O sample demonstrated that the sample well-indexed to the monoclinic phase with high purity and well crystallinity. Fourier Transform infrared (FT-IR) of the sample proved hydrophilicity of the as-synthesized sample. Moreover, scanning electron microscopy (SEM) analysis indicated that the product consist of a large amount of the colloidal hierarchical Cu3V2O7(OH)2·2H2O hollow spheres with a mean diameter of about 2–4 µm, in which an individual self-assembled spherical structure was composed of a large number of the 50–90 nm nanoparticles. The optical properties of the sample was studied by ultraviolet–visible spectroscopy (UV–Vis) and emission/excitation spectra analyses (PL). The results showed that the sample has photo absorption ability in the visible region and an energy band-gap of 2.44 eV was estimated from UV–Vis absorption spectrum. Also, the as-prepared nanostructures has a very red-shifted PL emissions with high intensity under the excitation wavelength of 237 nm in their photoluminescence spectra.

Facile hydrothermal synthesis and luminescent properties of Sm3+/Eu3+ codoped GdPO4 phosphors

Well-defined GdPO4 nanocrystals were successfully prepared through the facile hydrothermal synthesis route followed by a heat treatment. The microstructure, morphologies and photoluminescence properties of as-prepared samples were investigated via X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), fourier transform infrared spectroscopy (FT-IR), photoluminescence (PL) spectroscopy and luminescence decay, which were significantly affected by the reaction conditions (phosphorus source, acidity of hydrothermal process and surfactants). It is found that Sodium dodecyl sulfate (SDS) as a shape modifier has the dynamic effect by adjusting the growth rate of different facets, resulting in morphology transformation of GdPO4·H2O from the nanowire (without SDS) to the nanorod (with SDS). Strong yellow-orange emissions could be obtained in Sm3+ and Eu3+ ions codoped GdPO4 phosphors under ultraviolet light irradiation. Moreover, the energy transfer mechanism from Sm3+ to Eu3+ has been studied and proved to be a dipole-dipole interaction mechanism. These results show this yellow-orange-emitting phosphors material may have potential applications in field-emission displays.

Controllable preparation of highly uniform CuCo2S4 materials as battery electrode for energy storage with enhanced electrochemical performances

In this work, three different morphologies of CuCo2S4 materials have been prepared by a facile hydrothermal synthesis route by controlling the species of solvent and molar concentration of precursors. The effects of reaction conditions on the physical characteristics (including microstructure, morphology, specific surface area and pore structure) and electrochemical behaviors of the products were systematically investigated. The experimental results reveal that as-obtained highly uniform micro-/nanostructure CuCo2S4 particles prepared by mixed solvent (H2O/ethylene glycol(EG)) and low molar concentration of precursors manifest the best electrochemical performances. The specific capacity is up to 90.6mAhg−1 at a current density of 2Ag−1, and 47.9% of capacity retention rate can be retained when the current density varies from 2 to 50Ag−1. Furthermore, a superior cycling stability with 95.6% of initial capacity retention rate can be maintained at 3Ag−1 after 5000 consecutive charge-discharge cycles. The enhanced electrochemical performances can be mainly attributed to the highly uniform micro-/nanostructure with relatively larger specific surface area and total pore volume. Therefore, the results above demonstrate that the as-prepared highly uniform micro-/nanostructure CuCo2S4 particles might be promising candidate battery electrode materials for energy storage.

Novel nanosheets-assembled Bi 12.5 P 0.5 O 20 microcubes: Facile hydrothermal synthesis, optical and catalytic performances

Fabrication of assembly structure composed of building blocks is one of the important challenges in material chemistry field, because such unique nanoarchitectures help us to a better comprehension of the “bottom-up” route and afford a platform to explore and discover some new and interesting performances of micro/nanomaterials. Herein, we for the first time present a facile hydrothermal synthesis route for the fabrication of novel nanosheets-assembled Bi12.5P0.5O20 microcubes with the edge-length in 1–2 µm. The thickness of the sheet-like building block was calculated to be ∼23 nm. Some factors (reaction temperature, time, the presence of sodium carboxymethyl cellulose and the amount of NaOH) influencing the morphology and phase of the product were also investigated. UV–vis diffuse reflectance spectrum of the product revealed that the bandgap of the Bi12.5P0.5O20 sample was 2.71 eV. Furthermore, catalytic experiments demonstrated that the Bi12.5P0.5O20 microcubes exhibited excellent catalytic ability for the transformation of 4-nitrophenol in the existence of excess NaBH4 solution.

Facile hydrothermal synthesis of Fe 3+ doped Bi 2 Mo 2 O 9 ultrathin nanosheet with improved photocatalytic performance

Abstract Construction of doped-type semiconductor-based photocatalysts can be considered as an excellent platform for enhancing photocatalytic performance owing to their unique properties such as excellent light-absorption ability, more reactive sites and increased photo-induced charge transfer capability. Therefore, we propose a facile hydrothermal synthesis route for the construction of Fe 3+ doped Bi 2 Mo 2 O 9 ultrathin nanosheet with thicknesses of ~4 nm. Experimental result indicated that the introduction of Fe 3+ into the Bi 2 Mo 2 O 9 lattice could enhance the light absorption ability and narrow the band-gap of the final product. Photocatalytic results showed that Fe 3+ doped Bi 2 Mo 2 O 9 ultrathin nanosheet exhibited enhanced photocatalytic activity for the decomposition of Rhodamine B (RhB) compared with pure Bi 2 Mo 2 O 9 . Moreover, an enhanced mechanism of photocatalytic performance over Fe 3+ doped Bi 2 Mo 2 O 9 ultrathin nanosheet was investigated and proposed.

A Facile Hydrothermal Route for Synthesis of ZnS Hollow Spheres with Photocatalytic Degradation of Dyes Under Visible Light

A facile hydrothermal method was employed for the synthesis of ZnS hollow spheres by using thioglycolic acid (TGA) as a capping agent under hydrothermal condition. The obtained products were characterized by X-ray powder diffraction (XRD) and X-ray Photoelectron Spectroscopy (XPS). No diffraction peaks from other crystalline forms were detected, the synthesized ZnS hierarchical hollow spheres were relatively pure. The photocatalytic activities of as-synthesized samples were evaluated by the degradation of methyl orange (MO) and rhodamine B (RhB) under the condition of visible-light irradiation. The higher the initial MO and RhB concentrations, the longer it takes to reach the same residual concentration, implying that the apparent rates of MO and RhB degradation decrease with increase in the initial MO and RhB concentration. The increase of photocatalyst dosage from 0.2 to 0.6 g/L results in a sharp increase of the photodegradation efficiency from 68.50 to 92.66% after 180 min of visible-light irradiation for MO degradation, and the increase of photocatalyst dosage from 0.2 to 0.4 g/L results in a distinct increase of the photodegradation efficiency from 65.72 to 90.85% after 180 min of visible-light irradiation for RhB. The elution of intermediates generated in the photocatalytic mineralization of MO and RhB resulted in an increase in total organic carbon (TOC) level, leading to the difference between TOC removal rate and MO and RhB decolorization rates.

3D Nanosheet-Assembled CoSe Quasi-Microspheres as Advanced Electrode Materials for Electrochemical Energy Storage

Metal selenides, as a new class of metal chalcogenide, have recently attracted researcher's attention as superior electrode materials for energy storage. In this work, we have prepared the 3D nanosheet-assembled CoSe quasi-microspheres by a facile hydrothermal synthesis route and utilize them as supercapacitor electrode materials for the first time. The resulting 3D nanosheet-assembled CoSe quasi-microspheres manifest superior capacitive properties with a high specific capacitance of 440 F g−1 at 1 A g−1, excellent capacity retention rate of 85.9, 56.4 and 41.4% at 10, 50 and 100 A g−1, and good cycling stability with 102.3 and 96.3% of initial capacity retention rate at 2 and 10 A g−1 over 2000 and 5000 cycles, respectively. The good electrochemical performances can be ascribed to the unique 3D micro-/nanostructure with superior pore-size distribution, relatively large mesopores and exceptional electrical conductivity. The asymmetric supercapacitor is further assembled by employing 3D nanosheet-assembled CoSe quasi-microspheres as the cathode and activated carbon (AC) as the anode, respectively. The CoSe/AC asymmetric device displays a energy density of 17.6 Wh kg−1 at a power density of 684 W kg−1, and maintains 95.5% of its initial capacity at 3 A g−1 over 2000 cycles.

Morphological, structural and field emission characterization of hydrothermally synthesized MoS2-RGO nanocomposite

A few layered MoS2-RGO nanocomposite has been synthesized employing a facile hydrothermal synthesis route. The morphological and structural analysis performed using SEM, TEM, HRTEM and Raman spectroscopy clearly reveal formation of vertically aligned a few layer thick MoS2 sheets on RGO surface. Attempts have been made to reveal the influence of graphite oxide (GO) percentage on morphology of the nanocomposite. Furthermore, field emission (FE) investigations of as-synthesied MoS2-RGO nanocomposite are observed to be superior to the pristine MoS2 emitter. The values of turn-on field, defined at emission current density of 10 μA cm−2, are found to be 2.6 and 4.7 V μm−1 for the MoS2-RGO (5%) nanocomposite and pristine MoS2 emitters, respectively. The value of threshold field, defined at emission current density of 100 μA cm−2, is found to be 3.1 V μm−1 for MoS2-RGO nanocomposite. The emission current stability at the pre-set value of 1 μA over 3 h duration is found to be fairly good, characterized by current fluctuation within ±18% of the average value. The enhanced FE behavior for MoS2-RGO nanocomposite is attributed to a high enhancement factor (β) of 4128 and modulation of the electronic properties. The facile approach adopted herein can be extended to enhance various functionalities of other nanocomposites.