Surfactant-assisted Solvothermal Method Research Articles

Unique Tubular BiOBr/g-C3 N4 Heterojunction with Efficient Separation of Charge Carriers for Photocatalytic Nitrogen Fixation.

The industrial ammonia synthesis process consumes a lot of energy and causes serious environmental pollution. As a sustainable approach for ammonia synthesis, photocatalytic nitrogen reduction employing water as the reducing agent has a lot of potential. A simple surfactant-assisted solvothermal method is used to synthesize g-C3 N4 nanotubes with flower-like spherical BiOBr grown inside and outside (BiOBr/g-C3 N4 , BC). The hollow tubular structure realizes the full use of visible light by the multi-scattering effect of light. Large surface areas and more active sites for N2 adsorption and activation are present in the distinctive spatially dispersed hierarchical structures. Particularly, the quick separation and transfer of electrons and holes are facilitated by the sandwich tubular heterojunctions and tight contact interface of BiOBr and g-C3 N4 . The maximal NH3 generation rate of the BiOBr/g-C3 N4 composite catalysts can reach 255.04 μmol⋅ g-1 ⋅ h-1 , and it is 13.9 and 5.8 times that of pure BiOBr and g-C3 N4 . This work provides a novel method for designing and constructing unique heterojunctions for efficient photocatalytic nitrogen fixation.

Interplay between morphology and band gap energy in Fe-MIL-88A prepared via a high temperature surfactant-assisted solvothermal method

Metal-Organic Frameworks (MOFs) are a new class of crystalline microporous solids with superior properties compared to their inorganic counterparts that offer a great variety of properties. Fe-MIL-88A is a biocompatible MOF with a flexible structure that can be synthesized in various morphologies via different chemical methods. The present study proposes two efficient methods, namely, microemulsion and surfactant-assisted solvothermal method, to prepare Fe-MIL-88A nanorods with narrow size distribution and well-defined morphology. The morphology, crystalline and chemical structure of the prepared samples were studied using FESEM images, XRD patterns and FTIR spectra, respectively, and their absorption behavior was scrutinized using UV–Vis spectroscopy. It was observed that MOF nanorods had size and morphology-dependent electronic properties. The band gap energy was inversely proportional to the particle diameter. While MOF microrods showed a single band gap of 2.63 eV, their nanorods showed two band gap energies of about 3.1 and 3.6 eV. Based on the obtained results, the application of MOFs with the desired size and morphology in the field of band gap engineering seems possible.

Enhanced electrochemical performance of LiFePO4 of cathode materials for lithium-ion batteries synthesized by surfactant-assisted solvothermal method

Enhanced electrochemical performance of LiFePO4 of cathode materials for lithium-ion batteries synthesized by surfactant-assisted solvothermal method

Enhanced visible light driven photocatalytic performance of Bi2WO6 nano-catalysts by introducing oxygen vacancy

The introduction of defect has attracted tremendous interest as an efficient measure for improving the photocatalytic activity of semiconductor photocatalysts. Here, Bi2WO6 nano-catalysts with abundant oxygen vacancy fabricated by a facile surfactant-assisted solvothermal method exhibited superior photocatalytic performance for degradation ciprofloxacin, which achieved 90% after 6 h visible light irradiation. The formation of oxygen vacancy was confirmed by the electron paramagnetic resonance spectra. Theoretical calculation confirmed that the existence of oxygen vacancy would create new electric state vacancy band and then improve light harvesting ability. The experimental results further revealed that the oxygen vacancy dominant Bi2WO6 nano-catalysts possess enhanced visible light ability and photogenerated carrier separation efficiency due to the existence of oxygen vacancy. The oxygen defective Bi2WO6 nano-catalysts would be a promising photocatalyst in the field of treatment of environmental pollution.

Nickel-organic Frameworks with Hierarchical Flowers Structure Fabricated by Surfactant-assisted Solvothermal Method for High-performance Supercapacitors

Nickel-organic Frameworks with Hierarchical Flowers Structure Fabricated by Surfactant-assisted Solvothermal Method for High-performance Supercapacitors

Contribution of Ultrahigh Electrochemical Performance of NiCo2O4 Nanoneedle-Based Free-Standing Electrode from Functionalized Carbon Cloth

Spinel structure NiCo2O4 suffers from poor electric conductivity and the resulted electrochemical properties in battery/supercapacitor system are still unsatisfied. In this paper, a free-standing electrode based on in-situ growth NiCo2O4 on carbon cloth has been synthesized by a surfactant-assisted solvothermal method (sodium dodecyl sulfate, SDS). The functional carbon cloth substrate makes unexpected contribution to the electrochemical lithium-ion storage. The assembled supercapacitor possesses ultrahigh pseudocapacitive properties with high mass loading. The specific capacitance of 2832[Formula: see text]F[Formula: see text]g[Formula: see text] has been obtained at 1[Formula: see text]A[Formula: see text]g[Formula: see text] current density with maintaining the high rate capability of 1620[Formula: see text]F[Formula: see text]g[Formula: see text] at 20[Formula: see text]A[Formula: see text]g[Formula: see text]. The obtained nanoneedle NiCo2O4/carbon cloth electrode also maintains a specific capacity of 2000[Formula: see text]mA[Formula: see text]h[Formula: see text]g[Formula: see text] at 40[Formula: see text]mA[Formula: see text]g[Formula: see text] and exceptional rate performance (1504[Formula: see text]mAh[Formula: see text]g[Formula: see text] at 400[Formula: see text]mA[Formula: see text]g[Formula: see text] when tested as anode material in lithium ion batteries.

High performance and ultrafast reduction of 4-nitrophenol using metal-organic frameworks

Organic pollutants such as 4-nitrophenol (4-NP) exhibited a negative impact on human health and the environment of a biological system. Thus, several catalysts have been reported to mitigate the toxicity of 4-NP via the reduction to 4-aminophenol (4-AP). Furthermore, the reduction process is important for the synthesis of amine compounds as intermediate for several industrial sectors. Herein, two-dimensional (2D) metal-organic frameworks (MOFs) were synthesized using a surfactant-assisted solvothermal method. X-ray diffraction (XRD) reveals the formation of crystalline material. The scanning electron microscope (SEM) image showed 2D MOF with a thickness of 100−150 nm. Data analysis reveals the successful formation of a high crystalline phase of MOF with the morphology of 2D nanoscale. The synthesis procedure is simple and requires no expensive reagents or special equipment. The catalytic performance of the prepared material was examined for the reduction of 4-NP to 4-AP. The material exhibited ultrafast (2 min) catalytic performance with a complete reduction (conversion 100 %) without an induction period. The simple synthesis procedure besides the high catalytic performance of the prepared material endows the potential of 2D MOF for further applications including catalysis.

Probing the morphology dependence, size preference and electron/ion conductance of manganese-based lithium transition-metal phosphate as cathode materials for high-performance lithium-ion battery

As a promising cathode for next-generation lithium-ion batteries, the morphology dependence, size preference and electron/ion conductance of manganese-based lithium transition-metal phosphate (MLTP) compounds were comprehensively analyzed via synergistic strategies including the surfactant-assisted solvothermal method and surface modification. Variations of morphology, (particle, crystallite and lattice) size and electron/ion conductivity selectively modulated their electrochemical properties. For MLTP cathode materials, the as-prepared small-sized particle with large crystallite and large lattice greatly optimized the cycling stability, reversible capacity and polarization performance, whereas irregular particle morphology mainly inhibited the specific capacity. Meanwhile, the RGO-decorated MLTP-EG12/C cathode material could further unlock the high-rate capability and thermal stability without polarization differences. These regulation mechanisms of morphology, size and conductivity described in this work can be helpful in the development of high-performance cathode materials for lithium-ion batteries.

Br doped porous bismuth oxychloride micro-sheets with rich oxygen vacancies and dominating {0 0 1} facets for enhanced nitrogen photo-fixation performances

Bismuth oxychloride micro-sheets with rich oxygen vacancies (BiOCl-OV) are firstly prepared through a surfactant assisted solvothermal method. Due to the selective surfactant adsorption, the as-prepared BiOCl-OV exposes high percentage {0 0 1} facets. Moreover, the ion-exchange process not only introduces Br atoms but also creates cavities in crystal structure of the Br doped BiOCl-OV (Br-BiOCl-OV). When used as photocatalyst for N2 photo-fixation, the optimized Br-BiOCl-OV demonstrates an ammonia producing rate of 6.3 μmol h−1 under visible light irradiation, which is greatly enhanced than that of pristine BiOCl-OV (4.1 μmol h−1). The density functional theory (DFT) calculation suggests that because of the introduced Br atoms and the oxygen vacancies, the adsorbed N2 on Br-BiOCl-OV exhibits greater NN bond length than that adsorbed on pristine BiOCl-OV, attributing to the effective activation of the inert NN bonds. Photocurrent response, state/transient PL spectra and electrochemical impedance spectroscopy indicate that the Br-BiOCl-OV possesses promoted charge separation and suppressed charge recombination, which finally leads to the high N2 photo-fixation performances.

Novel defect-fluorite pyrochlore sodium niobate nanoparticles: solution-phase synthesis and radiation tolerance analysis.

Materials possessing a defect-fluorite pyrochlore structure can have a range of useful properties that are sought after, which include their radiation tolerance, nuclear waste immobilization, and phase stability at elevated temperatures. In this study, we demonstrate for the first time the synthesis and a detailed analysis of defect-fluorite pyrochlore sodium niobate (NaNbO3) nanoparticles. This analysis included an investigation into their stability to elevated temperatures and neutron irradiation. A surfactant-assisted solvothermal method is used to prepare nanoparticles of NaNbO3. This solution-phase approach results in the formation of crystalline nanoparticles of a defect-fluorite pyrochlore NaNbO3 at relatively low temperatures. The products had an average diameter of ∼74 ± 11 nm. The nanoparticles adopted a defect-fluorite pyrochlore phase and matched the cubic Fm3[combining macron]m space group. This pyrochlore form of NaNbO3 was found to be stable up to 500 °C. The nanoparticles transformed into the orthorhombic and rhombohedral perovskite phases of NaNbO3 along with the introduction of a pseudo-hexagonal Nb2O5 at higher temperatures. These defect-fluorite pyrochlore nanoparticles of NaNbO3 also exhibited a resistance to radiation induced amorphization. The dimensions, phase, and crystallinity of the defect-fluorite pyrochlore nanoparticles after exposure to a flux of neutrons were comparable to those of the as-synthesized product. The thermal stability and radiation tolerance of these pyrochlore nanoparticles could be useful in the design of thermally resilient materials, high temperature catalysts, and durable materials for the handling and storage of radioactive waste.

The excellent electrochemical performances of ZnMn2O4/Mn2O3: The composite cathode material for potential aqueous zinc ion batteries

A novel composite material of ZnMn2O4/Mn2O3 is fabricated via a facile surfactant-assisted solvothermal method, followed by an annealing process at 600 °C in air for 4 h. When further evaluated as a cathode for aqueous rechargeable zinc ion batteries (ARZIBs) for the first time, it delivers an initial discharge capacity of up to 82.6 mAh/g at 0.5 A/g just using 1 mol/L ZnSO4 as the electrolyte, and the amazing reversible capacity of 111.9 mAh/g can be achieved even after 300 cycles, much higher than the initial one. As the current density increases to 3.2 A/g, it also exhibits a high capacity as much as 42.1 mAh/g. The superior cycleability and remarkable rate performance are attributed to the synergistic effect, the ultrafast ion transportation characteristic and the smaller self-discharge phenomenon of ZnMn2O4 and Mn2O3. Thus, the work gives a new insight into developing new-type of cathode materials for large-scale application of ARZIBs with low cost, high safety and large power density.

Influence of Surfactant on the Morphology and Photocatalytic Activity of Anatase TiO2 by Solvothermal Synthesis

Highly photocatalytically active anatase TiO2 were synthesized by a solvothermal method using tetrabutyl titanate (TBT), citric acid, and ethanol as row material. The morphology and photocatalytic activity of titanium oxide have changed significantly with the presence of surfactants, such as cetyltrimethylammonium bromide (CTAB), sodium dodecylbenzenesulfonate (SDBS), and diethanolamine (DEA). Scanning electron microscope and X-ray powder diffraction results show that the synthesized products are anatase TiO2 spherical particles with a micronanostructure. The crystal type of TiO2 has no obvious change with the addition of different surfactants, but the morphology, size, and dispersion of the TiO2 particles have changed to some extent. Among the three surfactants, CTAB is beneficial to reduce TiO2 particle size and improve TiO2 dispersion and agglomeration. DEA is favor to self-assembly the nanocrystals into spherical particles. Degradation of methyl orange photocatalyzed by TiO2 prepared with CTAB as surfactant reaches 95.4% under ultraviolet light for 100 min. After five recycles, the catalyst did not exhibit significant loss of photocatalytic activity, confirming that the photocatalyst is essentially stable. This work indicates that the surfactant-assisted solvothermal method is an effective approach to improve the structure, morphology, and photocatalytic performance of TiO2. Moreover, the surfactants with various types can interact with the precursors of TiO2 in different ways.

Conformal coating of ultrathin metal-organic framework on semiconductor electrode for boosted photoelectrochemical water oxidation

Exploring efficient photocatalysts for water oxidation is highly demanded because of their significant role in artificial photosynthesis. The research of metal-organic frameworks (MOFs) based photoelectrochemical (PEC) water splitting is promising but still in its infancy due to the challenge to fabricate high-quality MOFs photoelectrode. Here an Fe2O3/Fe-based MOF core/shell nanorod is prepared for efficient PEC water oxidation via a facile surfactant-assisted solvothermal method. With polyvinylpyrrolidone (PVP) molecules as intermedia, an ultrathin MOF shell of several nanometers thick can be controllably grown on the surface of Fe2O3 nanorod. Charge dynamical behaviors study by ultrafast transient absorption spectroscopy (TAS) and photoelectrochemical impedance spectroscopy (PEIS), reveal that the ultrathin MOF shell is crucial to promote the charge separation by providing a cascade band level, but also accelerate the hole injection efficiency via exposing more accessible Fe-oxo cluster active sites. Accompanied with good visible-light response, the Ti-doped Fe2O3/NH2-MIL-101(Fe) photoanode delivers a boosted photocurrent density of 2.27 mA cm−2 at 1.23 V vs. RHE, which is about 2.3 folds of that of pristine Fe2O3. This study provides new insights into the rational design of semiconductor/MOFs hybrid materials for photo/photoelectrochemical catalysis.

Enhanced generation of hydroxyl radicals on well-crystallized molybdenum trioxide/nano-graphite anode with sesame cake-like structure for degradation of bio-refractory antibiotic

Anodic electro-catalysis oxidation is a highly effective way to solve the pollution problem of antibiotics in wastewater and receiving water bodies. In this study, for the first time, molybdenum trioxide/Nano-graphite (MoO3/Nano-G) composites are synthesized as anodic catalysts by a surfactant-assisted solvothermal method followed by low-temperature calcination. The effects of the proportion of MoO3 to Nano-G (10, 30 and 50%) on the properties of composites are investigated through structural characterizations and electrochemical measurements. Results indicate that MoO3(30)/Nano-G electrode displays the electro-catalysis degradation efficiency of 99.9% towards ceftazidime, which is much higher than those of Nano-G (46.7%) and dimensionally stable anode (69.2%). The degradation mechanism for ceftazidime is studied by investigating the yields and kinds of active species. Results show that all of the OH, O2− and H2O2 are responsible for the electro-catalytic degradation process, and the produced OH radicals are the major active species for ceftazidime degradation. The synergistic effects between MoO3 and Nano-G greatly contribute to the activation of H2O molecules to produce OH, meanwhile the special sesame cake-like structure facilitates to the exposure of contaminants to OH on active sites to enhance the degradation efficiency. These results suggest that MoO3/Nano-G electrodes can be considered as the promising catalysts for treating bio-refractory organic wastewater.

Influence of PEG Stoichiometry on Structure-Tuned Formation of Self-Assembled Submicron Nickel Particles.

Self-assembled submicron nickel particles were successfully synthesized via the one-step surfactant-assisted solvothermal method. The impact of surfactant and reducing agent stoichiometry is investigated in this manuscript. Different morphologies and structures of Ni particles, including flower-like nanoflakes, hydrangea-like structures, chain structures, sphere-like structures, and hollow structures were prepared through different processing conditions with two parameters such as temperature and time. Based on scanning electron microscopy (SEM), X-ray diffraction (XRD), thermal gravimetric analysis (TGA) and vibrating sample magnetometry (VSM), the submicron nickel particles show good saturation magnetization and excellent thermal stabilities with a possible growth mechanism for the variety of the structure-tuned formation. Importantly, the microwave absorption properties of the submicron nickel particles were studied. The lowest reflection loss of Ni-P9/T200/H15 with a thin layer thickness of 1.7 mm can reach −42.6 dB at 17.3 GHz.

Preparation of an octahedral PtNi/CNT catalyst and its application in high durability PEMFC cathodes.

In order to promote the application of proton exchange membrane fuel cells (PEMFCs) in electric vehicles (EVs), it is important to improve the activity of cathode catalysts and the corrosion resistance of carbon supports under high potentials formed during transient vehicle operating conditions. An octahedral PtNi/CNT catalyst with a well-defined structure and enhanced oxygen reduction reaction (ORR) performance was prepared through a surfactant-assisted solvothermal method. Its mass activity and specific activity reach 5.5 and 8.5 times those of the commercial Pt/C catalyst, respectively, and its stability is also higher after durability testing. In addition, the membrane electrode assembly (MEA) fabricated using the octahedral PtNi/CNT catalyst in a cathode exhibits extremely outstanding durability under high potential, and the attenuations of its maximum power density and cell voltage at 600 mA cm−2 are only 4.8% and 3.6%, respectively, which are far below those of the control prepared with commercial Pt/C. These results demonstrate that carbon materials with a graphite structure exhibit actual application potential in the preparation of octahedral catalysts. These carbon-supported octahedral catalysts are expected to be applied in PEMFC cathodes after the materials and preparation process are further improved.

Morphology-controlled synthesis of hierarchical mesoporous α-Ni(OH)2 microspheres for high-performance asymmetric supercapacitors

A simple morphology-controlled synthesis for hierarchical α-Ni(OH)2 microspheres has been developed. Three kinds of α-Ni(OH)2 microspheres with different structures were prepared by one-step surfactant-assisted solvothermal method, using water, ethanol and their mixture as solvent respectively. The effects of solvent on the structure, morphology and capacitive performance of α-Ni(OH)2 were investigated. The microstructure and chemical composition of as-prepared α-Ni(OH)2 were characterized by a variety of means, such as XRD, BET, XANES, SEM, TEM and HRTEM. Among the as-prepared samples, Ni(OH)2-c microspheres, obtained from the mixed solvent (ethanol solution), are composed of hierarchical flower-like nanosheets and possess the roughest surface and the largest specific surface area (101.3 m2 g−1). Electrochemical measurements reveal that Ni(OH)2-c is of the highest specific capacitance (1087.1 F g−1 at a current density of 1 A g−1) and excellent cycling stability (97.7% capacitance retention after 3000 charge-discharge cycles at a current density of 5 A g−1) in 6 M KOH electrolyte. Furthermore, an symmetric supercapacitor (Ni(OH)2//AC), using Ni(OH)2-c as positive electrode and activated carbon as negative electrode, delivers a high energy density 32.9 Wh kg−1 at power density 0.8 kW kg−1 under potential window 1.6 V. Additionally, Ni(OH)2//AC exhibits good cycling performance (98% capacitance retention after 3000 cycles at a current density of 5 A g−1) and nearly 100% Coulombic efficiency. The performances suggest its potential application in supercapacitors.

Preparation of 2D/2D g-C3N4 nanosheet@ZnIn2S4 nanoleaf heterojunctions with well-designed high-speed charge transfer nanochannels towards high-efficiency photocatalytic hydrogen evolution

In this work, we design and construct a novel 2D/2D g-C3N4 nanosheet@ZnIn2S4 nanoleaf via a simple one-step surfactant-assisted solvothermal method for photocatalytic H2 generation. Its unusual 2D/2D heterojunction structure provides far more contact areas and much faster charge transport rate than the 2D/0D heterojunction structure of g-C3N4 nanosheet@ZnIn2S4 microsphere. More importantly, this unique 2D/2D heterojunction leads the g-C3N4 nanosheet@ZnIn2S4 nanoleaf composite to generate numerous intimate high-speed charge transfer nanochannels in the interfacial junctions, and which could considerably enhance the photogenerated charge separation and migration efficiency, thus yielding a remarkable visible-light-driven H2 evolution rate without the additive Pt cocatalyst (HER=2.78mmolh−1g−1), nearly 69.5, 15.4, 8.2 and 1.9 times higher than that of pure g-C3N4 nanosheet, pure ZnIn2S4 microsphere, 2D/0D g-C3N4 nanosheet@ZnIn2S4 microsphere and pure ZnIn2S4 nanoleaf, respectively. Additionally, the 2D/2D g-C3N4 nanosheet@ZnIn2S4 nanoleaf exhibits an outstanding stability and recyclability, manifesting a promising potential application in sustainable energy conversion. This work would provide a platform for the design and synthesis of binary heterojunction composite system with highly-efficient charge separation and transfer.

Oleylamine-assisted solvothermal synthesis of copper antimony sulfide nanocrystals: Morphology and phase control

We report a one-pot synthesis of copper antimony sulfide nanocrystals by a facile and easily scalable route using a surfactant assisted solvothermal method. Phase-pure and quasi-monodisperse Cu3SbS4 nanocrystals have successfully been synthetized by adjusting the sulfur to copper molar ratio as well as the surfactant to solvent volumetric ratio. Nanocrystals morphology and chemical composition are characterized. As synthetized and purified nanocrystals are formulated into a colloidal suspension in order to fabricate copper antimony sulfide films. Morphological, electrical and optical characterizations of famatinite films are conducted. The electrical resistivity of the as deposited films is comprised between 10Ωcm and 48Ωcm. The optical gap is found to be indirect with a value of 0.82eV.

Effect of Various Spinel Ferrite Nanopigments Modified by Amino Propyl Trimethoxy Silane on the Corrosion Inhibition Properties of the Epoxy Nanocomposites

A series of ferrite spinel nanopigments doped with various elements were synthesized via a surfactant-assisted solvothermal method. Then, they were modified with 3-amino propyl trimethoxy silane (APTMS) and characterized by x-ray diffraction analysis, thermal gravimetric analysis, Fourier transform infrared spectroscopy, and energy dispersive x-ray spectroscopy. The unmodified and APTMS modified spinel nanopigments were incorporated into epoxy coatings and their inhibition properties were studied by electrochemical impedance spectroscopy and salt spray test. Results showed that the APTMS modified ZnFe2O4 nanopigment resulted in greater improvement of the barrier action and inhibitive properties of the epoxy coating than Fe3O4 nanopigment.