CMC-Na辅助磁性Fe3S4纳米复合物的合成及其吸附与吸波性质研究

以羧甲基纤维素钠(CMC-Na)为模板,采用简单温和的水热法制备了一种薄片状含碳Fe3S4纳米复合物,并探讨了反应时间和反应温度的影响。采用X射线衍射、扫描电镜、透射电镜、FT IR、振动磁强计和UV-Vis对材料进行了表征。结果表明,这种纳米复合材料在常温下具有较好的吸波性质和对污水中亚甲基蓝染料的吸附作用。     

Hydrothermal synthesis of MoS2 with controllable morphologies and its adsorption properties for bisphenol A

The effect of preparation conditions (molar ratio of S/Mo, hydrothermal temperature and time) on the morphologies of MoS₂ was investigated. The as-synthesized materials were characterized by X-ray diffraction (XRD), field emission scanning microscopy (FESEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Raman spectra and Brunauer–Emmett–Teller’s (BET) surface area measurement. Results showed that the three kinds of morphologies of MoS₂ were obtained. Morphologies varied gradually from the coral-like aggregated particles to flower-like spheres to wrapped nano-sheet structure with increasing hydrothermal temperature and time. It is meaningful for specific morphology demand in different fields. Moreover, the prepared materials were used as tentative adsorbents for the removal of bisphenol A (BPA) as a representative of endocrine disruptors. The results showed that the prepared MoS₂ materials with wrapped nano-sheet structure had good adsorption capacity (39.03 mg/g) and fast adsorption rate (0.0053 g/(mg/min). The adsorption process was thermodynamically exothermic and spontaneous. The study indicated that electrostatic interaction is strong and π-π interaction between BPA and the MoS₂ materials play an important role for BPA adsorption.     

Fe/nanoporous carbon hybrid derived from metal–organic framework for highly effective microwave absorption

A novel Fe/nanoporous carbon (Fe/NPC) composite was synthesized via Fe₃O₄ nanoparticles coating in metal–organic framework. The pyrolysis conditions are carefully optimized, and the effects of pyrolysis temperature on electromagnetic parameters have been systematically analyzed. Among these candidates, the Fe/NPC composite pyrolyzed at 800 °C (Fe/NPC‐800) shows the eminent microwave absorption due to interface polarization and well matched characteristic impedance. The results indicate that the effective reflection loss absorption bandwidth of Fe/NPC‐800 reaches 5.6 GHz (12.4–18 GHz) with a thickness of 1.8 mm. It provides an exciting clue for the fabrication of lightweight and highly effective microwave absorbers in the future.     

片状MoS2/MoS1.5Se0.5纳米复合材料的制备及其摩擦学性能研究

将钼粉与升华硫和硒粉的混合粉末按一定化学计量比混合,通过固相反应法成功制备出了均匀的片状纳米颗粒。分别使用X射线粉末衍射仪(XRD)、扫描电子显微镜(SEM)以及透射电子显微镜(TEM)对该纳米粉体进行结构表征和分析,发现该粉体为MoS2/MoS1.5Se0.5混合晶相,晶粒尺寸在300~600 nm,厚度约为5 nm的片状结构。将该MoS2/MoS1.5Se0.5纳米片作为润滑油添加剂添加到基础油中,使用UMT-2型摩擦磨损试验机对其摩擦学性能进行测试,并对摩擦机理进行了解释,结果表明MoS2/MoS1.5Se0.5纳米片作为润滑油添加剂具有良好的减摩抗磨性能。     

The formation of MoS<Subscript>2</Subscript> secondary phase at the Cu—Zn—Sn—S/Mo interface during the sulfurization process of Cu—Zn—Sn precursor films

We report on the influence of the sulfurization conditions on the MoS₂ secondary phase formation in Cu—Zn—Sn—S thin films synthesized by thermal evaporation method of metals and intermetallics that can be used for the formation of absorbing layers of solar cells. The dependence between photoconductivity and the intensity of the base line of MoS₂ was found in Raman spectra, which is described by a curve with characteristic maximum. It was found that the secondary phase formation on the Cu—Zn—Sn—S/Mo boundary and photoconductivity of sulfurized films are strongly dependent on the applied temperature conditions. Specifically, films without MoS₂ phase have a low photoconductivity, whereas a high photoconductivity was observed for the films with significant content of secondary phase.     

Synthesis of Au/SnO2 core-shell structure nanoparticles by a microwave-assisted method and their optical properties

Au/SnO₂ core-shell structure nanoparticles were synthesized using the microwave hydrothermal method. The optical and morphological properties of these particles were examined and compared with those obtained by the conventional hydrothermal method. In microwave preparation, the peak position of the UV-visible plasmon absorption band of Au nanoparticles was red-shifted from 520 to 543 nm, due to the formation of an SnO₂ shell. An SnO₂ shell formation was complete within 5 min. The thickness of the SnO₂ shell was 10-12 nm, and the primary particle size of SnO₂ crystallites was 3-5 nm. For the core-shell particles prepared by a conventional hydrothermal method, the shell formed over the entire synthesis period and was not as crystalline as those produced, using the microwave method. The relationship between the morphological and spectroscopic properties and the crystallinity of the SnO₂ shell are discussed.     

Microwave absorption properties and infrared emissivities of ordered mesoporous C-TiO2 nanocomposites with crystalline framework

Ordered mesoporous C-TiO₂ nanocomposites with crystalline framework were prepared by the evaporation-induced triconstituent co-assembly method. The products were characterized by XRD, TEM, N₂ adsorption-desorption and TG. Their microwave absorption properties were investigated by mixing the product and epoxy resin. It is found that the peak with minimum reflection loss value moves to lower frequencies and the ordered mesoporous C-TiO₂ nanocomposite possesses an excellent microwave absorbing property with the maximum reflection loss of −25.4 dB and the bandwidth lower than −10 dB is 6.6 GHz. The attenuation of microwave can be attributed to dielectric loss and their absorption mechanism is discussed in detail. The mesoporous C-TiO₂ nanocomposites also exhibit a lower infrared emissivity in the wavelength from 8 to 14 μm than that of TiO₂-free powder.     

Flowerlike MoS2 nanoparticles: solvothermal synthesis and characterization

Flowerlike MoS₂ nanoparticles have been successfully synthesized through a mild solvothermal reaction with the aid of ethanol aqueous solution, and the samples have been characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and low temperature nitrogen adsorption-desorption. The nanometer flower MoS₂ is composed of ultrathin nanosheets of approximately 10 nanometers in thickness. The influence of the reaction temperature and the reaction time on the formation of the flowerlike MoS₂ nanoparticles were evaluated. The optimal experimental conditions were determined as follows: the molar ratio of 1:1 between ethanol and water, the reaction temperature of 190°C, and the reaction time of 24 h. __________ Translated from Chinese Journal of Inorganic Chemistry, 2008, 24(6) (in Chinese)     

不同硫源水热合成的MoS2催化剂的形貌和加氢脱氧活性比较研究

分别采用硫脲、L-胱氨酸和硫磺为硫源水热合成了三种MoS₂催化剂,对其结构和形貌特征进行了表征,并以对甲酚为探针化合物,比较研究了三种MoS₂的加氢脱氧（HDO）催化活性。结果表明,硫源对MoS₂晶体结构的影响不大,但对其形貌和比表面积影响较大。与商业MoS₂相比,所制备的MoS₂催化剂都表现出更高的HDO活性;其中,以硫脲为原料合成的MoS₂具有较高的比表面积和花状结构,其催化活性最高,在300℃下进行对甲酚的HDO反应,脱氧度可达99.3%。     

DFT study into the reaction mechanism of CO methanation over pure MoS2

Mo‐based catalysts are commonly used in the direct methanation of CO; however, no integrated mechanism has been proposed due to limits in characterizing the nano‐sized active structures of MoS₂. Thus, we report our investigation into the mechanism of CO methanation over pure MoS₂ through density functional theory simulations, considering that only MoS₂ edge sites exhibit catalytic activity. Simulations revealed the presence of (010) and (110) surfaces on the MoS₂ edges. Both surfaces are reconstructed by the redistribution of surface sulfur atoms upon exposure to H₂/H₂S, and after sulfur coverage redistribution, S vacancies are generated for CO hydrogenation. The reaction mechanisms on both surfaces are discussed, with the S‐edge being better suited to CO methanation than Mo‐edge on the (010) surface. The rate‐controlling step differs between surfaces, and corresponds to the initial activation reaction, which was achieved more easily on the (110) surface.     

Synthesis of Highly Uniform Molybdenum–Glycerate Spheres and Their Conversion into Hierarchical MoS2 Hollow Nanospheres for Lithium‐Ion Batteries

Highly uniform Mo–glycerate solid spheres are synthesized for the first time through a solvothermal process. The size of these Mo–glycerate spheres can be easily controlled in the range of 400–1000 nm by varying the water content in the mixed solvent. As a precursor, these Mo–glycerate solid spheres can be converted into hierarchical MoS₂ hollow nanospheres through a subsequent sulfidation reaction. Owing to the unique ultrathin subunits and hollow interior, the as‐prepared MoS₂ hollow nanospheres exhibit appealing performance as the anode material for lithium‐ion batteries. Impressively, these hierarchical structures deliver a high capacity of about 1100 mAh g^?1 at 0.5 A g^?1 with good rate retention and long cycle life.     

Low‐Temperature Atomic Layer Deposition of MoS2 Films

Wet chemical screening reveals the very high reactivity of Mo(NMe₂)₄ with H₂S for the low‐temperature synthesis of MoS₂. This observation motivated an investigation of Mo(NMe₂)₄ as a volatile precursor for the atomic layer deposition (ALD) of MoS₂ thin films. Herein we report that Mo(NMe₂)₄ enables MoS₂ film growth at record low temperatures—as low as 60 °C. The as‐deposited films are amorphous but can be readily crystallized by annealing. Importantly, the low ALD growth temperature is compatible with photolithographic and lift‐off patterning for the straightforward fabrication of diverse device structures.     

Improved hydrothermal synthesis of MoS2 sheathed carbon nanotubes

MoS₂ sheathed carbon nanotubes have been successfully synthesized using a hydrothermal route under controlled conditions. The resultant material was studied by XRD, EDS, HRTEM, and Raman spectroscopy. Advantages of the preparation presented here compared to other methods are: a) lower reaction temperature, b) high yield of sheathed nanotubes including ends and full body, c) simple process with non-toxic materials, and d) no damage inflicted to nanotubes.     

Synthesis and crystal morphology control of AlPO4-5 molecular sieves by microwave irradiation

AlPO₄-5 molecular sieves have been synthesized by the hydrothermal and solvothermal reactions using triethylamine as a template, aluminum isopropoxide and orthophosphate as the aluminum and phosphorus resource under microwave irradiation. The influences of various experimental parameters, such as reaction time, reaction temperature and reaction power, have been systematically investigated. The morphology control of AlPO₄-5 molecular sieves was achieved by changing the dosage of solvent and HF to control the solvent polarity and control the nucleation respectively. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and so on. The results show that the aspect ratio of the AlPO₄-5 molecular sieves increases with the increase of the solvent polarity and with the increasing concentration of HF, the morphology of AlPO₄-5 molecular sieves changes from hexagonal plate to hexagonal rod.     

The Core/Shell Structure P Doped MoS2@Ni3S2 Nanorods Array for High Current Density Hydrogen Evolution in Alkaline and Acidic Electrolyte

Electrocatalysis is the most promising strategy to generate clean energy H₂, and the development of catalysts with excellent hydrogen evolution reaction (HER) performance at high current density that can resist strong alkaline and acidic electrolyte environment is of great significance for practical industrial application. Therefore, a P doped MoS₂@Ni₃S₂ nanorods array (named P-NiMoS) was successfully synthesized through successive sulfuration and phosphorization. P-NiMoS presents a core/shell structure with a heterojunction between MoS₂ (shell) and Ni₃S₂ (core). Furthermore, the doping of P modulates the electronic structure of the P-NiMoS; the electrons transfer from the t_2g orbital of Ni element to the e_g empty orbital of Mo element through the Ni−S−Mo bond at the Ni₃S₂ and MoS₂ heterojunction, facilitating the hydrogen evolution reaction. As a result, P-NiMoS exhibits excellent HER activity; the overpotential is 290 mV at high current density of 250 mA cm⁻² in alkaline electrolyte, which is close to Pt/C (282 mV@250 mA cm⁻²), and P-NiMoS can stably evolve hydrogen for 48 h.     

Defect Engineering of MoS2 and Its Impacts on Electrocatalytic and Photocatalytic Behavior in Hydrogen Evolution Reactions

Molybdenum disulfide (MoS₂) has been regarded as a favorable photocatalytic co‐catalyst and efficient hydrogen evolution reaction (HER) electrocatalyst alternative to expensive noble‐metals catalysts, owing to earth‐abundance, proper band gap, high surface area, and fast electron transfer ability. In order to achieve a higher catalytic efficiency, defects strategies such as phase engineering and vacancy introduction are considered as promising methods for natural 2H‐MoS₂ to increase its active sites and promote electron transfer rate. In this study, we report a new two‐step defect engineering process to generate vacancies‐rich hybrid‐phase MoS₂ and to introduce Ru particles at the same time, which includes hydrothermal reaction and a subsequent hydrogen reduction. Compositional and structural properties of the synthesized defects‐rich MoS₂ are investigated by XRD, XPS, XAFS and Raman measurements, and the electrochemical hydrogen evolution reaction performance, as well as photocatalytic hydrogen evolution performance in the ammonia borane dehydrogenation are evaluated. Both catalytic activities are boosted with the increase of defects concentrations in MoS₂, which ascertains that the defects engineering is a promising route to promote catalytic performance of MoS₂.     

Electrolysis of solid MoS2 in molten CaCl2 for Mo extraction without CO2 emission

Sintered (300 °C) porous pellets of MoS₂ were electrolysed to elemental S and Mo in molten CaCl₂ (800–900 °C) under argon at 1.0–3.0 V for 1–20 h. On a graphite anode, the product was primarily S (but traces of CS₂ could not yet be excluded by this work) and evaporated from the molten salt, allowing the electrolysis to continue. It then condensed to solid at the lower temperature regions of the system. The anode remained intact after repeated uses. The MoS₂ pellet was highly conducting at high temperatures and could be fast electro-reduced to fine Mo powders (0.1–1.0 μm) in which the S content could be below 1000 ppm. No reduction occurred at voltages below 0.5 V. Partial reduction was seen at 0.5–0.7 V, and converted MoS₂ to a mixture of MoS₂ and Mo₃S₄, or Mo₃S₄ and Mo with the Mo content increasing with the voltage. Cyclic voltammetry of the MoS₂ powder in a Mo-cavity electrode, together with the electrolysis results, revealed the reduction mechanism to include two steps: MoS₂ to Mo₃S₄ at −0.28 V (potential vs. Ag/AgCl), and then to Mo at −0.43 V.     

One-pot hydrothermal synthesis of willow branch-shaped MoS2/CdS heterojunctions for photocatalytic H2 production under visible light irradiation

Willow branch-shaped MoS₂/CdS heterojunctions are successfully synthesized for the first time by a facile one-pot hydrothermal method. The as-prepared samples were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, nitrogen adsorption-desorption measurements, diffuse reflectance spectroscopy, and photoelectrochemical and photoluminescence spectroscopy tests. The photocatalytic hydrogen evolution activities of the samples were evaluated under visible light irradiation. The resulting MoS₂/CdS heterojunctions exhibit a much improved photocatalytic hydrogen evolution activity than that obtained with CdS and MoS₂. In particular, the optimized MC-5 (5 at.% MoS₂/CdS) photocatalyst achieved the highest hydrogen production rate of 250.8 μmol h^-1, which is 28 times higher than that of pristine CdS. The apparent quantum efficiency (AQE) at 420 nm was 3.66%. Further detailed characterizations revealed that the enhanced photocatalytic activity of the MoS₂/CdS heterojunctions could be attributed to the efficient transfer and separation of photogenerated charge carriers resulting from the core-shell structure and the close contact between MoS₂ nanosheets and CdS single-crystal nanorods, as well as to increased visible light absorption. A tentative mechanism for photocatalytic H₂ evolution by MoS₂/CdS heterojunctions was proposed. This work will open up new opportunities for developing more efficient photocatalysts for water splitting.     

Topochemical Path in High Lithiation of MoS2

Lithiation of MoS₂/RGO (reduced graphite oxide) electrodes repeatedly reached experimental capacities larger than 1000 mA · g^–1, corresponding to at least 6 lithium equivalents per gram of MoS₂. At our best knowledge, a convincing explanation is still missing in literature. In most cases, phase separation into Li₂S and elemental Mo was assumed to occur. However, this can only explain capacities up to 669 mA · g^–1, corresponding to an exchange of four Li. Formation of LiMo alloys could resolve the problem but the Li/Mo system does not contain any binary phases. If signs for Li₂S formation were found, indeed experimental capacities were below 700 mAh · g^–1. Here we present a topochemical mechanism, which sustains multiple charge/discharge cycles at 1000 mAh · g^–1, corresponding to an exchange of at least 6 Li per formula unit MoS₂. This topochemical reaction route prevents decomposition into binary phases and thus avoids segregation of the components of MoS₂. Throughout the whole lithiation/delithiation process, distinct layers of Mo are preserved but extended or shrunk by slight movements and reshuffling of sulfur and lithium atoms. On addition of 6 Li per formula unit to MoS₂, all central sulfur atoms are hosted in mutual Mo–S layers such that formal S^2– and Mo^2– anions appear coordinated by lithium cations. Indeed, similar structures are known in the field of Zintl phases. Our first‐principles crystal structure prediction study describes this topological path through conversion reactions during the lithiation/delithiation processes. All optimized phases along the topological path exhibit a distinct Mo layering giving rise to a series of dominant scattering into pseudo 001 reflections perpendicular to these Mo planes. The mechanism we present here explains why such high capacities can be reached reversibly for MoS₂/RGO nano composites     

Revealing the Role of Gold in the Growth of Two-Dimensional Molybdenum Disulfide by Surface Alloy Formation

The formation of Mo/Au surface alloy during Au-assisted chemical vapor deposition (CVD) of MoS₂ is confirmed by a series of control experiments. A metal–organic chemical vapor deposition (MOCVD) system is adapted to conduct two-dimensional MoS₂ growth in a controlled environment. Sequential injection of Mo and S precursors, which does not yield any MoS₂ on SiO₂/Si, grows atomically thin MoS₂ on Au, indicating the formation of an alloy phase. Transmission electron microscopy of a cross-section of the specimen confirms the confinement of the alloy phase near the surface only. These results show that the reaction intermediate is the surface alloy, and that the role of Au in the Au-assisted CVD is the formation of an atomically thin reservoir of Mo near the surface. This mechanism is clearly distinguished from that of MOCVD, which does not involve the formation of any alloy phases.