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1.
Developing highly efficient, cost-saving, and durable multifunctional electrocatalysts for oxygen evolution reaction (OER), oxygen reduction reaction (ORR), and hydrogen evolution reaction (HER) continues to be a significant challenge in the energy field. In this work, we decide to prepare an unusual multifunctional electrocatalyst, such as icosahedral palladium nanocrystals (PdNCs) encapsulating on N–MoO 2–Mo 2C half-hollow nanotube (HHNT) heterointerface, using an in-situ chemical reaction and following sonic probe irradiation method. All the experiments demonstrate that special defect-enriched heterointerfaces N–MoO 2–Mo 2C supported Pd nanocomposite can greatly improve the ORR activity (E onset = 1.01 V and E 1/2 = 0.90 V) with good stability, outstanding HER (η 10 = 65 mV) and OER (η 10 = 180 mV) performances than those of commercial precious electrocatalysts (Platinum on carbon [Pt/C] and ruthenium oxide [RuO 2]). The overall water splitting electrolyzer fabricates by Pd/N–MoO 2–Mo 2C as both anode and cathode electrodes to achieve a current density of 10 Ma/cm 2 at a cell voltage of 1.56 V, which surpasses the most recent reported electrocatalysts. 相似文献
2.
Porous copper oxide (CuO) hollow microspheres have been fabricated through a simple hydrothermal method using PS latex as templates. The as-obtained samples were characterized by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffractometry (XRD) and Fourier transform infrared spectroscopy (FTIR). The influences of the mole ratio of Ethylenediamine (C 2H 8N 2) and copper acetate (Cu(Ac) 2·H 2O), hydrothermal temperature and time on the size and morphologies of the final products have been investigated. The possible formation mechanism of porous CuO hollow microspheres has been proposed and the specific surface area of the hollow microspheres with 81.71 m 2/g is measured by BET method. The band gap value calculated from a UV–vis absorption spectrum of porous CuO hollow microspheres is 2.71 eV. The as-synthesized product exhibits high photocatalytic activity during the photodegradation of an organic dyestuff, rhodamine B (RhB), under UV-light illumination. 相似文献
3.
The spherical mesoporous MCM-41 coated with a novel Ca 2MoO 5:Eu 3+ phosphor layer was prepared for the first time. The obtained Ca 2MoO 5:Eu 3+-MCM-41 was characterized via XRD and FT-IR. The crystal system of the Ca 2MoO 5 phase was determined to be orthorhombic, and its space group was found to be Ima2 (46), and its cell parameters were a = 16.175, b = 5.1514, c = 5.6977 A°; α = β = γ = 90°. The particle dimensions of MCM-41 and Ca 2MoO 5:Eu 3+-MCM-41 nanoparticles were determined to be 260 nm and 229 nm via scanning electron microscopy analysis. Bortezomib was loaded into the Ca 2MoO 5:Eu 3+-MCM-41 nanoparticles under scCO 2 at 200 bars and 40 °C. The results of the TG analysis showed that the amount of drug-loaded to MCM-41 and Ca 2MoO 5:Eu 3+-MCM-41 nanoparticles were determined to be 14.02% and 3.02%, respectively. The BET analysis showed that while the specific surface area and pore volume of MCM-41 and Ca 2MoO 5:Eu 3+ before Bortezomib (BTZ) loading were 1,506 m 2/g and 267 m 2/g, respectively, after drug loading these values were found to decrease to 488 m 2/g and 7.883 m 2/g. It was determined that BTZ was released from the nanoparticles in a sustained manner over 66 h. The R 2 value, which was calculated to be 0.9739, indicated that the release kinetic of BTZ followed the Korsmeyer–Peppas model. 相似文献
4.
Molybdenum trioxide (MoO 3) nanowire with unprecedentedly high aspect ratios (>200) and good crystallinity was prepared via decomposition of (NH 4) 6Mo 7O 24·4H 2O under a microwave-assisted hydrothermal (MH) process. The nanowire was orthorhombic MoO 3 with 50 nm in diameter and 10–12 μm in length. The conventional hydrothermal (CH) reaction required higher temperature and longer reaction times to produce one-dimensional MoO 3, yet its quality was lower. In the electrochemical hydrogen evolution reaction in a H 2SO 4 solution, MoO 3 nanowire from MH process showed much higher electrocatalytic activity than MoO 3 prepared from CH method and commercial bulk MoO 3 particles. The facile vectorial electron transport along the nanowire axis was considered to be responsible for the excellent electrocatalytic activity of the MH–MoO 3 nanowire. 相似文献
5.
Acetalization of glycerol with various aldehydes has been carried out using mesoporous MoO 3/SiO 2 as a solid acid catalyst. A series of MoO 3/SiO 2 catalysts with varying MoO 3 loadings (1–20 mol%) were prepared by sol–gel technique using ethyl silicate-40 and ammonium heptamolybdate as silica and molybdenum source respectively. The sol–gel derived samples were calcined at 500 °C and characterized using various physicochemical characterization techniques. The XRD of the calcined samples showed the formation of amorphous phase up to 10 mol% MoO 3 loading and at higher loading of crystalline α-MoO 3 on amorphous silica support. TEM analyses of the materials showed the uniform distribution of MoO 3 nanoparticles on amorphous silica support. Raman spectroscopy showed the formation of silicomolybdic acid at low Mo loading and a mixture of α-MoO 3 and polymolybdate species at high Mo loadings. Moreover the Raman spectra of intermediate loading samples also suggest the presence of β-MoO 3. Acetalization of glycerol with benzaldehyde was carried out using series of MoO 3/SiO 2 catalysts with varying MoO 3 loadings (1–20 mol%). Among the series, MoO 3/SiO 2 with 20 mol% MoO 3 loadings was found to be the most active catalyst in acetalization under mild conditions. Maximum conversion of benzaldehyde (72%) was obtained in 8 h at 100 °C with 60% selectivity for the six-membered acetal using 20% MoO 3/SiO 2. Interestingly with substituted benzaldehydes under same reaction conditions the conversion of aldehydes decreased with increase in selectivity for six-membered acetals. These results indicate the potential of this catalyst for the acetalization of glycerol for an environmentally benign process. 相似文献
6.
Molybdic acid (H 2MoO 4, MA) doped polyaniline (PANI) micro/nanostructures were prepared by a self-assembly process in the presence of ammonium persulfate ((NH 4) 2S 2O 8, APS) as the oxidant. The morphology of PANI-MA changed from nanofibers or nanotubes (~160 nm in diameter) to co-existence of nanofibers and microspheres (~3 μm in diameter) and that accompanied an enhancement of the conductivity from 5.42 × 10 ?3 S cm ?1 to 2.8 × 10 ?1 S cm ?1as the molar ratio of MA to aniline varied from 0.01 to 1.5. With increasing the polymerization time, moreover, the pH value of the reaction solution not only decreased due to sulfuric acid produced during the course of the polymerization, but also accompanied a change in morphology from microspheres to nanofibers. All above-mentioned observations could be interpreted by spherical and cylindrical micelle composed of MA as the “soft-template” in forming the micro/nanostructures. 相似文献
7.
Yolk–shell MoO 3 microspheres are prepared by a two‐step process in which molybdenum oxide–carbon (MoO x–C) composite microspheres are first obtained by spray pyrolysis, followed by combustion at 400 °C in air. The yolk–shell microspheres exhibit excellent electrochemical properties and structural stability. 相似文献
8.
Sulfur‐resistant methanation of syngas was studied over MoO 3–ZrO 2 catalysts at 400°C. The MoO 3–ZrO 2 solid‐solution catalysts were prepared using the solution combustion method by varying MoO 3 content and temperature. The 15MoO 3–ZrO 2 catalyst achieved the highest methanation performance with CO conversion up to 80% at 400°C. The structure of ZrO 2 and dispersed MoO 3 species was characterized using X‐ray diffraction and transmission electron microscopy. The energy‐dispersive spectrum of the 15MoO 3–ZrO 2 catalyst showed that the solution combustion method gave well‐dispersed MoO 3 particles on the surface of ZrO 2. The structure of the catalysts depends on the Mo surface density. It was observed that in the 15MoO 3–ZrO 2 catalyst the Mo surface density of 4.2 Mo atoms nm ?2 approaches the theoretical monolayer capacity of 5 Mo atoms nm ?2. The addition of a small amount of MoO 3 to ZrO 2 led to higher tetragonal content of ZrO 2 along with a reduction of particle size. This leads to an efficient catalyst for the low‐temperature CO methanation process. 相似文献
9.
The ultrasonic parameters, the optical parameters along with the IR spectroscopy and magnetic susceptibility studies have been employed to explore the role of Gd 2O 3 in the structure of the glasses xGd 2O 3–60B 2O 3–10MoO 3–(30- x)Bi 2O 3, with 0 ≤ x ≤ 7 mol %. IR analysis indicates that Gd 2O 3 is preferentially incorporated into the borate network-forming BO 4 units. It is assumed that Bi 2O 3 and MoO 3 enter the structure as modifiers in the form of BiO 6 and MoO 6 only. The compositional dependence of the mechanical and the optical parameters are interpreted in terms of the transformation of the structural units BO 3 into BO 4, the increase in the number of bridging oxygen atoms, and the substitution of high bond strength Gd–O, in the place of low bond strength Bi–O bond. The results of the magnetic susceptibility reveal the paramagnetic behavior as described by the Curie-Weiss law and indicating the presence of weak antiferromagnetic exchange interactions between Gd 3+ ions. The magnetic entropy change of the glasses was determined according to the temperature and magnetic field dependence of magnetization. 相似文献
10.
采用水热法合成了MoO_3/酚醛树脂前驱体,然后在空气中进行煅烧处理,成功制备了一种新型核壳MoOx/C微球。对材料的晶体结构、形貌和元素价态进行分析表明,该材料的主要成分是单斜相MoO_2、正交晶系MoO_3和碳。树脂在空气中的煅烧碳化将MoO_3/酚醛树脂前驱体中的六方晶系的MoO_3还原为单斜相MoO_2。其中少量的MoO_2会在空气中重新被氧化成正交晶系的MoO_3,形成了MoO_2/MoO_3异质结构。在这一系列反应的综合作用下,形成这种表面有裂纹的核壳MoOx/C微球复合材料。将该材料用作锂离子电池负极材料,表现出了循环稳定性高、倍率性能好等优异的电化学性能。在100 mA·g-1的电流密度下充放电循环100次之后,可逆容量达640.6 mAh·g-1。 相似文献
11.
A series of MoO 3/H-ZSM-5 (Si/Al = 25) catalysts were prepared via calcination at a lower-than-usual temperature (400 °C) and subsequently evaluated in the methanol-to-hydrocarbon reaction at that same temperature. The catalytic properties of those catalysts were compared with the sample prepared at the more conventional, higher temperature of 500 °C. For the lower temperature preparations, molybdenum oxide was preferentially dispersed over the zeolite external surface, while only the higher loading level of MoO 3 (7.5 wt% or higher) led to observable inner migration of the Mo species into the zeolite channels, with concomitant partial loss of the zeolite Brønsted acidity. On the MoO 3 modified samples, the early-period gas yield, especially for valuable propylene and C 4 products, was noticeably accelerated, and is gradually converted into an enhanced liquid aromatic formation. The 7.5 wt% MoO 3/H-ZSM-5 sample prepared at 400 °C thereby achieved a balance between the zeolite surface dispersion of Mo species, their inner channel migration and the corresponding effect on the intrinsic Brønsted acidity of the acidic zeolite. That loading level also possessed the highest product selectivity (after 5 h reaction) to benzene, toluene and xylenes, as well as higher early-time valuable gas product yields in time-on-stream experiments. However, MoO 3 loading levels of 7.5 wt% and above also resulted in earlier catalyst deactivation by enhanced coke accumulation at, or near, the zeolite channel openings. Our research illustrates that the careful adoption of moderate/lower temperature dispersion processes for zeolite catalyst modification gives considerable potential for tailoring and optimizing the system''s catalytic performance. 相似文献
12.
Molybdenum forms a range of oxides with different stoichiometries and crystal structures, which lead to different properties and performance in diverse applications. Herein, crystalline molybdenum oxide thin films with controlled phase composition are deposited by atomic layer deposition. The MoO 2(thd) 2 and O 3 as precursors enable well-controlled growth of uniform and conformal films at 200–275 °C. The as-deposited films are rough and, in most cases, consist of a mixture of α- and β-MoO 3 as well as an unidentified suboxide MoO x (2.75 ≤ x ≤ 2.89) phase. The phase composition can be tuned by changing deposition conditions. The film stoichiometry is close to MoO 3 and the films are relatively pure, the main impurity being hydrogen (2–7 at-%), with ≤1 at-% of carbon and nitrogen. Post-deposition annealing is studied in situ by high-temperature X-ray diffraction in air, O 2, N 2, and forming gas (10% H 2/90% N 2) atmospheres. Phase-pure films of MoO 2 and α-MoO 3 are obtained by annealing at 450 °C in forming gas and O 2, respectively. The ability to tailor the phase composition of MoO x films deposited by scalable atomic layer deposition method represents an important step towards various applications of molybdenum oxides. 相似文献
13.
Mechanochemical method has applied to the green preparation of iron-molybdenum catalyst efficiently, and their catalytic performance was evaluated by the oxidation of methanol to formaldehyde. In order to investigate the formation process of iron-molybdenum catalyst based on mechanochemical method, various characterization techniques have been employed. Results indicate that iron-molybdenum catalyst could not be generated during ball milling process without calcining, and calcination is crucial step to regulate the ratio of MoO3 and Fe2(MoO4)3. For the formation of MoO3 and Fe2(MoO4)3 phase, 180 °C could be the key turning temperature point. Fe2(MoO4)3 and MoO3 phases are concurrently emerged when Mo/Fe atomic ratio exceeds 1.5. The aggregation of Fe2(MoO4)3 is severe with the increasing calcination temperature. Fe2(MoO4)3 is stable below 600 °C, while MoO3 phase could be subliming with the increasing temperature. The catalytic performance of iron-molybdenum catalyst has closely correlation with the phase compositions, which can be controlled by synthesis temperature and Mo/Fe molar ratio. The iron-molybdenum catalyst with Mo/Fe atomic ratio of 2.6 calcined at 500 °C for 4 h showed the best methanol conversion (100%) and formaldehyde yield (92.27%). 相似文献
14.
A novel type of uranium‐containing microspheres with an urchin‐like hierarchical nano/microstructure has been successfully synthesized by a facile template‐free hydrothermal method with uranyl nitrate hexahydrate, urea, and glycerol as the uranium source, precipitating agent, and shape‐controlling agent, respectively. The as‐synthesized microspheres were usually a few micrometers in size and porous inside, and their shells were composed of nanoscale rod‐shaped crystals. The growth mechanism of the hydrothermal reaction was studied, revealing that temperature, ratios of reactants, solution pH, and reaction time were all critical for the growth. The mechanism study also revealed that an intermediate compound of 3 UO 3?NH 3?5 H 2O was first formed and then gradually converted into the final hydrothermal product. These uranium‐containing microspheres were excellent precursors to synthesize porous uranium oxide microspheres. With a suitable calcination temperature, very uniform microspheres of uranium oxides (UO 2+x, U 3O 8, and UO 3) were successfully synthesized. 相似文献
15.
Experimental studies on diesel soot oxidation under a wide range of conditions relevant for modern diesel engine exhaust and continuously regenerating particle trap were performed. Hence, reactivity tests were carried out in a fixed bed reactor for various temperatures and different concentrations of oxygen, NO 2 and water (300–600 °C, 0–10% O 2, 0–600 ppm NO 2, 0–10% H 2O). The soot oxidation rate was determined by measuring the concentration of CO and CO 2 product gases. The parametric study shows that the overall oxidation process can be described by three parallel reactions: a direct C–NO 2 reaction, a direct C–O 2 reaction and a cooperative C–NO 2–O 2 reaction. C–NO 2 and C–NO 2–O 2 are the main reactions for soot oxidation between 300 and 450 °C. Water vapour acts as a catalyst on the direct C–NO 2 reaction. This catalytic effect decreases with the increase of temperature until 450 °C. Above 450 °C, the direct C–O 2 reaction contributes to the global soot oxidation rate. Water vapour has also a catalytic effect on the direct C–O 2 reaction between 450 °C and 600 °C. Above 600 °C, the direct C–O 2 reaction is the only main reaction for soot oxidation. Taking into account the established reaction mechanism, a one-dimensional model of soot oxidation was proposed. The roles of NO 2, O 2 and H 2O were considered and the kinetic constants were obtained. The suggested kinetic model may be useful for simulating the behaviour of a diesel particulate filter system during the regeneration process. 相似文献
16.
High surface area ZrO2–KOH sample was prepared and used the catalyst for the synthesis of glycerol carbonate (GC) from dimethyl carbonate (DMC) and glycerol. The structure properties of ZrO2–KOH were characterized by XRD, BET, CO2-TPD, XPS, and ICP-OES. It was found that the strong basicity of ZrO2–KOH might be attributed to the oxygen vacancies as well as the big surface area. Experiments were developed to evaluate the effects of catalysis loading, proportion of reactants, temperature and reaction time on the conversion of glycerol to GC. The consequences showed that ZrO2–KOH was a highly efficient basic catalyst for synthesis of GC from glycerol. The catalytic performance of ZrO2–KOH is much better than that of ZrO2–KOH–CP, ZrO2–NH4OH, and some reported heterogeneous catalysts. And the higher performance of ZrO2–KOH was ascribed to the strong basicity. 99.43% conversion was obtained in a particular situation of catalyst/glycerol weight ratio of 3 wt%, DMC/glycerol molar ratio of 3:1, reaction temperature of 80 °C, and reaction time of 2 h. The plausible reaction mechanism for the transesterification on the strong basic active sites was discussed. 相似文献
17.
The present paper deals with differential thermal analysis studies conducted to find out the onset temperature for silicothermic reduction of MoO 2 to Mo. The reaction kinetics of Si–MoO 2 system has been analyzed by a model-free Kissinger method. X-ray diffraction analysis has confirmed the formation of Mo metal and SiO 2 as the slag phase after silicothermic reduction of MoO 2. The activation energy for silicothermic reduction of MoO 2 to Mo was evaluated to be 309 kJ mol ?1. 相似文献
18.
The reaction of MoO 3 with various oxides of manganese (MnO, Mn 2O 3, Mn 3O 4 and MnO 2) and with MnCO 3 has been studied in air and nitrogen atmospheres employing DTA, TG and X-ray diffraction methods, with a view to elucidating the conditions for the formation of MnMoO 4. Thermal decomposition of MnCO 3 has also been studied in air and nitrogen atmospheres to help understand the mechanism of the reaction between MnCO 3 and MoO 3. The studies reveal that, whereas MnO, Mn 2O 3 and MnO 2 react smoothly with MoO 3 to form MnMoO 4, Mn 3O 4 does not react with MoO 3 in the temperature range investigated (48O–6OO°C). An equimolar mixture of MnCO 3 and MoO 3 reacts in air to yield MnMoO 4, while only a mixture of Mn 3O 4 and MoO 3 remains as final product when the same reaction is carried out in nitrogen. Marker studies reveal that manganese ions are the main diffusing species in the reaction between MoO 3 and manganese oxides that result in MnMoO 4. 相似文献
19.
Nanoplate-like bismuth molybdates (γ-Bi 2MoO 6) is prepared for the first time by urea assisted solution combustion synthesis (SCS) and studied the structural and electrochemical properties to explore the possibility of using as negative electrodes in pseudocapacitors. The formation of single phase γ-Bi 2MoO 6 and plate-like morphology is revealed from XRD Rietveld refinement and FESEM, respectively. The pseudocapacitive behaviour of γ-Bi 2MoO 6 is analyzed by cyclic voltammetry and galvanostatic charge–discharge techniques. The effect of Na based aqueous electrolytes on capacitance of the Aurvillius type structured Bi 2MoO 6 is investigated. As prepared γ-Bi 2MoO 6 nanoplates provide the high specific capacitance (519 F g −1) compared with the high-temperature monoclinic phase γ(H) Bi 2MoO 6 in 1 M NaOH electrolyte. The obtained high specific capacitance of as prepared Bi 2MoO 6 could be attributed to the decrease in particle size, increase in active sites, and nanoplate-like structure of as prepared γ-Bi 2MoO 6. 相似文献
20.
The aromatic [CpCo(S 2C 2(R)(H))] (R = Ph, Me, 9-phenanthryl, H) complexes reacted with N-halosuccinimides (NXS; X = Cl, Br, I) in carbon tetrachloride at room temperature to undergo the N-succinimide substitution reaction on the dithiolene ring, but no halogenated dithiolene complex was obtained. The imidation products [CpCo(S 2C 2(R)( N-sccinimide))] were yielded up to 64% where X = I and R = 9-phenanthryl. The reaction of [CpCo(S 2C 2(Ph)(H))] with N-bromophthalimide (NBP) also gave the imidation product [CpCo(S 2C 2(Ph)( N-phthalimide))]. This is the rare direct imidation reaction to an aromatic metallacycle by NXS. The reaction of [CpCo(S 2C 2H 2)] (R = H) with NIS afforded the double imidation product. One by-product in this reaction was the dithiolene-dithiolene homo-coupling product [CpCo(S 2C 2(R))] 2 (R = Ph, Me, 9-phenanthryl). The microwave-enhanced (MW) reactions were attempted in the carbon tetrachloride solution. Although the solution temperature increased up to only 43 °C by MW irradiation, the imidation reaction worked with short reaction time. 相似文献
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