Facile Two-step Hydrothermal Route Research Articles

Ternary Nanohybrid of Ni3S2/CoMoS4/MnO2 on Nickel Foam for Aqueous and Solid-State High-Performance Supercapacitors.

To overcome the issues related to supercapacitor (SC) electrodes, such as high cost, low specific capacitance (Cs), low energy density (ED), requirements for expensive binder, etc., binderless electrodes are highly desirable. Here, a new ternary nanohybrid is presented as a binder-free SC electrode based on Ni3S2, CoMoS4, and MnO2. A facile two-step hydrothermal route, followed by a short thermal annealing process, is developed to grow amorphous polyhedral structured CoMoS4 and further wrap MnO2 nanowires on Ni foam. This rationally designed binder-free electrode exhibited the highest Cs of 2021 F g−1 (specific capacity of 883.8 C g−1 or 245.5 mAh g−1) at a current density of 1 A g−1 in 1 M KOH electrolyte with a highly porous surface morphology. This electrode material exhibited excellent cycling stability (90% capacitance retention after 4000 cycles) due to the synergistic contribution of individual components and advanced surface properties. Furthermore, an aqueous binder-free asymmetric SC based on this ternary composite exhibited an ED of 20.7 Wh kg−1, whereas a solid-state asymmetric SC achieved an ED of 13.8 Wh kg−1. This nanohybrid can be considered a promising binder-free electrode for both aqueous and solid-state asymmetric SCs with these remarkable electrochemical properties.

Hierarchical Co3O4@CoAl hydrotalcite grown on Ni foam for high-performance asymmetric supercapacitors

The pineapple flower-like hierarchical Co3O4@CoAl-layered double hydroxides (Co3O4@ CoAl-LDH) with 3D mesoporous network structure were designed and in-situ synthesized on nickel foam (NF) through a facile two-step hydrothermal route for supercapacitors. The Co3O4@CoAl-LDH displayed a greater specific capacitance of 949.7C g−1 (1899.4 F g−1) at 1.0 A g−1, better rate capability and higher cycle stability comparing with the pristine Co3O4 and CoAl-LDH on NF. At the same time, the as-fabricated Co3O4@CoAl-LDH//activated carbon (Co3O4@CoAl-LDH//AC) device delivered outstanding energy densities of 77.58 and 36.03 Wh kg−1 at a power density of 754.83 and 7813.73 W kg−1, respectively, and excellent rate capability and outstanding long-term cycle stability (84.99% retention of the initial value at 5 A g−1 after 20,000 cycles). The superior electrochemical performances showed that the Co3O4@CoAl-LDH was a promising candidate as electrode materials for high-performance energy storage devices.

A novel, facile, and efficient two-step hydrothermal route for WS2 nanosheets and its optimistic exposure as competent industrial-level sonocatalyst

The present work reports a fast and efficient two-step hydrothermal route that can deliver both WO3 nanoparticles and WS2 nanosheets. Prepared samples were characterized using X-ray diffraction, Raman analysis, Fourier transform infrared spectroscopy, and UV–Vis–NIR absorption. Scanning electron microscopy analysis reveals that WS2 powder is composed of nanosheets having layered structures. WO3 nanoparticles and WS2 nanosheets synthesized were found to be efficient sonocatalyst and exhibited good removal efficiency (RE) in the case of water containing methylene blue (MB), which is the most commonly used dye in textile and wood industries. Under same catalyst dosage (1 g/L) and MB concentration (10 mg/L), WO3 nanoparticles showed 61.2% of RE within 90 min, whereas WS2 nanosheets showed a remarkable RE of 85.4% within 30 min. Brunauer–Emmett–Teller surface area analysis and some quantitative explanations are furnished for better sonocatalytic performance of WS2 nanosheets compared to WO3 nanoparticles. It was also established that sonolysis and adsorption, performing separately, do not have significant role in dye degradation. Reusability of WS2 nanosheets is also checked for five consecutive runs and they showed excellent cavitation erosion resistance and hence reproducibility that are very important to be established as a method for industrial dye-contaminated wastewater treatment. Finally yet importantly, capability of suggested sonocatalytic process for industrial-level wastewater treatment was illustrated by calculating electric energy in kilowatt hours (kWh) required to degrade 1 kg of MB (8.3 × 103 kWh/Kg). The lower value energy consumption profile for present sonocatalytic process offers incredible future prospects.

Binder-free hierarchical core-shell-like CoMn2O4@MnS nanowire arrays on nickel foam as a battery-type electrode material for high-performance supercapacitors

Binder-free hierarchical core-shell-like CoMn2O4@MnS heterostructures have been successfully grown on the surface of nickel (Ni) foam using facile two-step hydrothermal deposition route. In supercapacitor applications, the as-prepared core-shell-like CoMn2O4@MnS composite electrode has been used successfully as a battery-type material. Scanning electron microscope (SEM) and transmission electron microscope characterizations reveal that the as-prepared CoMn2O4@MnS electrode delivers a dandelion-like heterostructures that contains the MnS nanoparticles grown on the surface of CoMn2O4 nanowire arrays (NWAs), resulting a core-shell-like structure. In addition to increasing electrochemical behaviour and precise surface area, the novel core-shell-like heterostructures provide superhighways for the ultra-fast transfer of electrons and ions. The probable plateaus of cyclic voltammetry and galvanostatic charge-discharge experiments suggest that Faradic battery-type redox activity is given by the as-prepared core-shell-like CoMn2O4@MnS NWAs electrode. As a battery-type material, core-shell-like CoMn2O4@MnS NWAs electrode exhibits a outstanding specific capacity of (~213.0 mA h g−1 at 2 Ag−1), remarkable rate capability (~89.91% retains even at 10 A g−1), and excellent cycling stability (~91.42% at 6 A g−1 over 5000 cycles), which are much higher than those of the bare CoMn2O4 electrode. The excellent energy storage performance corroborates that CoMn2O4@MnS NWAs can serve as an advanced battery-type electrode material for supercapacitor applications.

Facile synthesis of Au-decorated α-Fe2O3/rGO ternary hybrid structure nanocomposites for enhanced triethylamine gas-sensing properties

The preparation of hybrid nanostructures is vitally important to both basic research and actual applications. In this work, a novel hybrid structure of ternary α-Fe2O3/rGO/Au nanocomposites was favorably fabricated though a facile two-step hydrothermal route and subsequent in-situ reducing procedure. The characterization results indicated that the Au nanoparticles with sizes of 20–30 nm were modified on α-Fe2O3 nanocubes with a size range of 180–230 nm and were homogeneously anchored on the appearance of reduced graphene oxide (rGO) sheets. Gas-sensing test results demonstrated that the ternary hybrid structure exhibited improved triethylamine (TEA)-sensing performances such as the highest response (43.6–100 ppm TEA), fast response/recovery rate (5/7 s), and better selectivity (ethanol, ammonia, methanol, formaldehyde, trimethylamine, acetone). This work is expected to propose beneficial reference for the development of complex ternary nanocomposites for TEA detection in the future.

Hybrid Ni3S2-MoS2 nanowire arrays as a pH-universal catalyst for accelerating the hydrogen evolution reaction.

Hybrid Ni3S2-MoS2 NWAs/NF, hybrid Ni3S2-MoS2 nanowire arrays in situ grown on Ni foam via a two-step hydrothermal method, can achieve cathodic current densities of 10 mA cm-2 and 100 mA cm-2 at overpotentials of 99 mV and 260 mV in 1.0 M KOH and 111 mV and 194 mV in 0.5 M H2SO4, respectively. It still needs an overpotential of 103 mV at 10 mA cm-2 in 0.1 M PBS. This work opens a new avenue for designing heterogeneous active electrocatalysts for energy conversion and storage.

Durable and Stable MnMoO4-Coated Copper Mesh for Highly Efficient Oil-in-Water Emulsion Separation and Photodegradation of Organic Contaminants

Wastewater pollution has always been a major environmental problem worldwide. Furthermore, in light of the frequent oil spills that have occurred in recent years, the treatment of oily wastewater is particularly important. Herein, a MnMoO4-coated copper mesh was synthesized via a facile two-step hydrothermal route for application in the separation of oil-in-water emulsions. The mesh showed exceptional wettability and separation efficiency (more than 99.9% for toluene-in-water emulsions). In addition, the mesh possessed excellent photocatalytic activity toward the photodegradation of organic dyes in emulsions. The findings also demonstrated the durability and stability of the mesh, as evidenced by the sustained high separation efficiency that they displayed after abrasion or corrosion. Taken together, the findings indicate that the mesh prepared herein has great potential for application in oily wastewater treatment.

Controlled preparation of fiber-shaped 4-Br/Bi2O3 composite photocatalysts with excellent visible-light photocatalytic activity

In this paper, a series of Bi2O3 modified by 4-bromothiophenol named 4-Br/Bi2O3 composite photocatalysts were successfully synthesized via a facile two-step hydrothermal route. The obtained photocatalysts were characterized by XRD, TEM, SEM, SEM–EDS, XPS, UV–Vis DRS, PL and FT-IR, respectively. It could be observed that the pure Bi2O3 exhibited a rod-shaped structure, while the micro-morphologies of 4-Br/Bi2O3 composites displayed a uniform solid fiber-like structure, which could increase specific surface area and offer more photocatalytic active sites, ultimately enhancing the adsorption capacity and photocatalytic performance of photocatalysts. The 4-Br/Bi2O3 composite with hydrothermal time for preparation being 12 h in the second-step hydrothermal process exhibited the best photocatalytic activity, over which (the dosage of 50 mg) about 99.4% of malachite green(MG) with the initial concentration of 35 mg L−1 in solution was degraded after irradiation for 80 min. Its photocatalytic performance was tremendously improved compared with pure Bi2O3 (only 4.4% decomposition of MG), and this is ascribed to a widening of the photoresponse range and an improved separation efficiency of the current carriers of the composite. The four cyclic reactions revealed its high stability and reusability. Moreover, the active species trapping experiments indicated that ·O2− and h+ were the main active species in the photocatalytic degradation of MG. A possible enhanced photocatalytic mechanism of 4-Br/Bi2O3 composite photocatalysts was also proposed.

Core-shell structured ZnCo2O4@ZnWO4 nanowire arrays on nickel foam for advanced asymmetric supercapacitors

One of the most effective tactics to promote the electrochemical performance of supercapacitors is to design and synthesize hybrid binder-free electrodes with core-shell structures. In this work, hierarchical ZnCo2O4@ZnWO4 core-shell nanowire arrays grown on nickel foam are successfully fabricated via a facile two-step hydrothermal route and subsequent thermal treatment. The ZnCo2O4 nanowire arrays supported on nickel foam serve as the backbone for anchoring ZnWO4 nanosheets. When tested as binder-free electrodes for supercapacitors, the as-prepared ZnCo2O4@ZnWO4 hybrid electrode exhibits an ultrahigh specific areal capacitance of 13.4 F cm−2 at a current density of 4 mA cm−2 and superb cycling stability (98.5% retention after 5000 continuous cycles at a current density of 100 mA cm−2). Furthermore, an asymmetric supercapacitor based on ZnCo2O4@ZnWO4//active carbon is successfully designed. The as-designed asymmetric supercapacitor can achieve a maximum energy density of 24 Wh kg−1 at a power density of 400 W kg−1. Moreover, two as-prepared asymmetric supercapacitor devices in a series connection are able to light up a white light-emitting diode over 30 min. The outstanding electrochemical properties of the hybrid electrode demonstrate that it holds great potential for next generation energy storage applications.

A flexible all-solid-state asymmetric supercapacitors based on hierarchical carbon cloth@CoMoO4@NiCo layered double hydroxide core-shell heterostructures

Flexible and lightweight wire-shaped supercapacitors are important energy storage devices used for portable or wearable electronics. However, practical applications of flexible supercapacitors are still limited by the relatively poor performances. Herein, the hierarchical carbon cloth@CoMoO4@NiCo-LDH core-shell nanowire arrays supported have been synthesized via a facile two-step hydrothermal route coupled with annealing treatment. In addition, a possible mechanism for the growth of NiCo-LDH nanosheets (NSs) shell onto CoMoO4 nanowires (NWs) core is put forward based on the time-dependent experiments. The CC@CoMoO4@NiCo-LDH-12 h electrode exhibits a high specific capacitance of 2024 F g−1 at 1 A g−1, with 80.3% retention of the initial specific capacitance at 20 A g−1 and outstanding cycling stability. In addition, we have fabricated a flexible all-solid-state asymmetric supercapacitor (ASC) which achieves a maximum energy density of 59.5 Wh kg−1 at a power density of 800 W kg−1 and long-term cycling stability (89.7% device capacitance retention over 5000 cycles). The remarkable electrochemical performance can be ascribed to the rational combination of two electroactive materials and the reasonable array configuration.

Porous Co3S4@Ni3S4 heterostructure arrays electrode with vertical electrons and ions channels for efficient hybrid supercapacitor

Faradic electrodes with large specific surface areas, efficient electrons/ions migration channels and high redox activities are essential prerequisites for high performance supercapacitors. Herein, highly porous Co3S4@Ni3S4 heterostructure arrays were prepared onto Ni foam substrate by a facile two-step hydrothermal route for application as supercapacitor electrode. Because of the novel core-sheath heterostructure with vertically aligned porous nanowires arrays and macroporous channels, the Co3S4@Ni3S4 electrode can offer high electrons/ions mobilities and large specific surface area, therefore enables an areal capacitance (CA) of 3.6 F cm−1 at 0.8 mA cm−2 and 80% initial CA maintaining ratio undergoes 5000 consecutive charge-discharge cycles. When used as positive electrode of hybrid supercapacitor, the lightweight Co3S4@Ni3S4//porous carbon hybrid supercapacitor delivers an areal capacitance of 0.513 F cm−2 at 2 mA cm−2 and moderate rate capability, therefore can deliver areal energy densities of 0.19–0.021 mWh cm−2 within areal power density range of 1.72–38.4 mW cm−2, good cycleability and slow self-discharge behavior. The current Co3S4@Ni3S4 heterostructure arrays electrode paves a feasible avenue to improve the capacitive performances of supercapacitors through construction of hierarchically porous nanoarrays architectures.

Terbium(III) Modified Fluorescent Carbon Dots for Highly Selective and Sensitive Ratiometry of Stringent.

Highly selective and sensitive detection of guanosine 3'-diphosphate-5'-diphosphate (ppGpp), namely, the stringent in plants or microorganisms responding to strict or extreme environmental conditions such as stress and starvation, which plays an important role in gene expression, rRNA and antibiotics production, regulations of virulence of bacteria, and growth of plants, faces a great challenge owing to its extreme similarity to normal nucleotides. By modifying the surface groups of a facile two-step hydrothermal route prepared carbon dots (CDs) with terbium ions (Tb3+) in this contribution, a novel fluorescent probe with excellent properties such as highly physical and chemical stability, narrow emission and excitation wavelength-independent emission was prepared. The Tb3+ ions on the surface of CDs cannot only preserve the intrinsic fluorescence (FL) of CDs but also keep its own coordination capacity with rare earth complex, and thus the clamp structure (four phosphate groups) of ppGpp can specific binding with Tb3+ ions on the surface of CDs to produce antenna effect. Therefore, a highly selective and sensitive fluorescent ratiometry of ppGpp was developed by terbium-modified carbon dots (CDs-Tb) with the limit of detection as low as 50 nM based on the synergistic effect of antenna effect of Tb3+ ions and specific recognition capacity of CDs. The applicability of this assay was demonstrated by CDs-Tb-based paper sensor for high distinguishing ppGpp from other nucleotides with similar structure.

Sea urchin-like architectures and nanowire arrays of cobalt–manganese sulfides for superior electrochemical energy storage performance

Cobalt–manganese (Co–Mn)-based bimetallic compounds (such as Co–Mn oxides, hydroxides) have been investigated as a new type of high-performance electroactive materials for energy storage device. Nevertheless, Co–Mn sulfides are seldom investigated, especially for those with hierarchical architectures and structures. Herein, we first adopt a facile two-step hydrothermal route and synthesize Co–Mn sulfides with sea urchin-like architecture and nanowire array structure. The anion-exchange sulfuration process gives rise to hierarchical structure with numerous nanosheets grown on the surface. Benefiting from the attractive structures and the high electrochemical activity of Co–Mn sulfides, the Co–Mn sulfides show improved performance than Co–Mn oxides with similar morphology. Especially, the Ni foam-supported Co–Mn sulfide nanowire arrays exhibit superior performance of 502 C g−1 at 1 A g−1 as well as excellent cycling stability with 107% of capacity retention after 2000 cycles. In addition, a hybrid supercapacitor Co–Mn sulfide nanowire arrays/RGO displays an energy density of 18.4 Wh kg−1 at 375 W kg−1. More importantly, an ultrahigh power density (22.5 kW kg−1 at 9.5 Wh kg−1) and outstanding cycling stability can also be achieved. The excellent electrochemical performance can be ascribed to the attractive structure and high electrochemical activity of Co–Mn sulfide.

Hydrothermal Synthesis of CoMoO4/Co9S8 Nanorod Arrays on Nickel Foam for High-Performance Asymmetric Supercapacitors with High Energy Density

CoMoO4/Co9S8 nanorod arrays supported on nickel foam are successfully assembled via a facile two-step hydrothermal route. Due to the unique nanorod array structure, the CoMoO4/Co9S8, as the electrode, possesses a high capacity 1.54mA h·cm−2 (343.21mA h·g−1) and a large capacitance 9.17Fcm−2 (2059.26Fg−1) at a current density of 20 mA·cm−2 (4.44 A·g−1), and an excellent cycling stability (8.6% degradation after 3000 cycles). The asymmetric supercapacitor based on the CoMoO4/Co9S8 nanorod arrays as a positive electrode and porous active carbon as a negative electrode in an alkaline KOH aqueous electrolyte is fabricated. Owing to the synergetic effect between CoMoO4/Co9S8 and active carbon, CoMoO4/Co9S8//active carbon asymmetric supercapacitor exhibits an outstanding energy density of 42 Wh·kg−1 and an excellent cycling stability with 89.5% specific capacitance retained after 5000 cycles in an operating voltage of 1.6V. The facile synthesis route and remarkable supercapacitive performance of the CoMoO4/Co9S8 nanorod arrays is promising as a positive electrode materials for high-performance asymmetric supercapacitors.

Hybrid nanoarchitecture of TiO2 nanotubes and graphene sheet for advanced lithium ion batteries

A novel hybrid nanoarchitecture of TiO2 nanotubes/graphene was synthetized through a facile two-step hydrothermal route. The anatase TiO2 nanotubes with a diameter of about 20nm show a net-like structure and high dispersion on the graphene nanosheets. The as-prepared sample (TOG2) exhibits a high average capacity of 410mAhg−1 at 0.1Ag−1, superior cycling stability with negligible capacity fade over 300 cycles and rate capability of 192mAhg−1 at 1Ag−1. The enhanced electrochemical properties can be attributed to its unique hybrid structure. One-dimensional hollow tubular structure of TiO2 provides numerous open channels for electrolyte to access and facilitate the ultrafast diffusion of lithium ions. In addition, the graphene sheets are favorable for the fast electron transport within the electrode, as well as keep the structural integrity during long-term cycling processes.

Three-dimensional porous graphene-encapsulated CNT@SnO2 composite for high-performance lithium and sodium storage

Tin oxide (SnO2) is regarded as a promising anode material for both lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs) due to its large theoretical capacity. However, poor electrical conductivity and the weak cyclability resulted from dramatic volume expansion upon cycling process still hinder its practical application. Herein, we report a facile two-step hydrothermal route to encapsulate core–shell structured carbon nanotube (CNT)@SnO2 composite in a graphene coating with novel three-dimensional (3D) porous framework architecture (CNT@SnO2@G) as anode for both LIBs and SIBs. The resultant CNT@SnO2@G electrode suggests outstanding lithium and sodium storage performance with large specific capacity, remarkable cycling stability and excellent rate capability. For LIBs, it delivers a high initial discharge capacity of 1400mAhg−1 at 100mAg−1, improved reversible capacity of 947mAhg−1 after 100 cycles at 100mAg−1, and enhanced rate capability of 281mAhg−1 at 3000mAg−1. In addition, sodium storage testing suggests that a high discharge capacity of 323mAhg−1 after 100 cycles at 25mAg−1 was achieved. The present unique structural design associated with the remarkable lithium and sodium storage performance ensures CNT@SnO2@G as an advanced anode material for rechargeable LIBs and SIBs.

Electrochemical energy storage performance of heterostructured SnO2@MnO2 nanoflakes

In this work, we report synthesis of SnO2@MnO2 nanoflakes grown on nickel foam through a facile two-step hydrothermal route. The as-obtained products are characterized by series of techniques such as scanning electron microscopy (SEM), X-ray diffraction spectroscopy (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The as-obtained SnO2@MnO2 nanoflakes are directly used as supercapacitor electrode materials. The results show that the electrode possesses a high discharge areal capacitance of 1231.6mFcm−2 at 1mAcm−2 and benign cycling stability with 67.2% of initial areal capacitance retention when the current density is 10mAcm−2 after 6000 cycles. Moreover, the heterostructured electrode shows 41.1% retention of the initial capacitance when the current densities change from 1 to 10mAcm−2, which reveals good rate capability. SnO2@MnO2 nanoflakes products which possess excellent electrochemical properties might be used as potential electrode materials for supercapacitor applications.

Ni-, Pt- and (Ni/Pt)-doped TiO2 nanophotocatalysts: A smart approach for sustainable degradation of Rhodamine B dye

Ni (1wt%)-, Pt (1wt%)- and [Ni (0.5wt%)/Pt (0.5wt%)]-doped TiO2 nanoporous catalysts have been successfully obtained through a facile two-step hydrothermal route. TiO2 crystallizes mostly in the anatase phase and acts as a mesoporous matrix. Meanwhile, Ni, Pt and Ni/Pt dopants form small nanoparticles (NPs) (3–95nm in diameter) which are hosted by the TiO2 framework. The resulting composites exhibit a rather large surface area, in the range of 186–200m2/g. The band gap energy reduces from 3.03eV for the undoped TiO2 to 2.15eV for the Pt-loaded TiO2. As a consequence, absorption expands toward the visible light range. The photodegradation of Rhodamine B dye in aqueous medium has been investigated under UV–vis light irradiation. The presence of Ni, Pt and Ni/Pt NPs significantly enhances the photocatalytic activity of the material. Furthermore, the Ni-doped TiO2 shows ferromagnetic behavior at room temperature, which makes its recovery and subsequent fast reutilization possible. Interestingly, this sample also exhibits the best stability upon recycling. Considering all the current challenges in sustainable water remediation, these new photocatalysts could find applications in real environmental contexts in the near future.

NiMoO4nanowire @ MnO2nanoflake core/shell hybrid structure aligned on carbon cloth for high-performance supercapacitors

A novel hybrid structure of core/shell NiMoO4@MnO2was directly synthesized on carbon cloth by a facile two-step hydrothermal route for supercapacitors.

Controlled synthesis of CuInS2/reduced graphene oxide nanocomposites for efficient dye-sensitized solar cells

A nanocomposite comprised CuInS2 and reduced graphene oxide have been successfully synthesized via a facile two-step hydrothermal route using graphene oxide, thiourea, Indium chloride tetrahydrate and cuprous chloride as the raw materials, and L-Ascorbic acid as the reductant. Compared with pristine CuInS2, CuInS2 and reduced graphene oxide nanocomposites exploited as counter electrodes have exhibited outstanding electrocatalytic activity for the reduction of triiodide and excellent chemical stability due to the introduction of reduced graphene oxide. The characterization measurements indicate that the power conversion efficiency of dye-sensitized solar cell fabricated with CuInS2 and reduced graphene oxide nanocomposites counter electrode achieves 6.96%, which is higher than that of device using pristine CuInS2 counter electrode (5.49%), and comparable to the conventional platinum counter electrode (6.92%) under the same test conditions.