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Hard carbons (HCs) with high sloping capacity are considered as the leading candidate anode for sodium-ion batteries (SIBs); nevertheless, achieving basically complete slope-dominated behavior with high rate capability is still a big challenge. Herein, the synthesis of mesoporous carbon nanospheres with highly disordered graphitic domains and MoC nanodots modification via a surface stretching strategy is reported. The MoOx surface coordination layer inhibits the graphitization process at high temperature, thus creating short and wide graphite domains. Meanwhile, the in situ formed MoC nanodots can greatly promote the conductivity of highly disordered carbon. Consequently, MoC@MCNs exhibit an outstanding rate capacity (125 mAh g-1 at 50 A g-1 ). The "adsorption-filling" mechanism combined with excellent kinetics is also studied based on the short-range graphitic domains to reveal the enhanced slope-dominated capacity. The insight in this work encourages the design of HC anodes with dominated slope capacity toward high-performance SIBs.
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The identification of catalytically active sites (CASs) in heterogeneous catalysis is of vital importance to design and develop improved catalysts, but remains a great challenge. The CASs have been identified in the low-temperature selective catalytic reduction of nitrogen oxides by ammonia (SCR) over a hollandite manganese oxide (HMO) catalyst with a rod-shaped morphology and one-dimensional tunnels. Electron microscopy and synchrotron X-ray diffraction determine the surface and crystal structures of the one-dimensional HMO rods closed by {100} side facets and {001} top facets. A combination of X-ray absorption spectra, molecular probes with potassium and nitric oxide, and catalytic tests reveals that the CASs are located on the {100} side facets of the HMO rods rather than on the top facets or in the tunnels, and hence semi-tunnel structural motifs on the {100} facets are evidenced to be the CASs of the SCR reaction. This work paves the way to further investigate the intrinsic mechanisms of SCR reactions.
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The crystallization of zeolite beta in a dry gel system is found to follow the orientated attachment growth route, escorted with a temporal morphology change from bulky gel, through aggregation of the particulate to large zeolitic crystals. Modification of the precrystallized gel with organosilanes can be used to tune the morphology of the ultimate beta. When hexadecyltrimethoxysilane (HTS) is employed to modify precrystallized gel, a resumed secondary growth produces a hybrid mesocrystal of agglomerated nanozeolites. Combustive removal of organics leads to the formation of hierarchically porous zeolite beta of 100 to 160â nm, composed of nanocrystal building units ranging from 20 to 40â nm, with a noticeable micropore volume of 0.19â mL g(-1) and a meso/macropore size between 5 and 80â nm. Conversely, when 1,8-bis(triethoxysilyl)octane (BTO) is utilized to modify the same precrystallized gel, assemblages of discrete beta nanozeolite of around 35â nm are generated. These assemblages construct a hierarchical zeolite beta with a micropore volume of 0.20â mL g(-1) and auxiliary pores ranging from 5 to 100â nm. Both organosilanes bring about well-connected hierarchical pore networks. HTS has little effect on the Brønsted/Lewis acidity, whereas BTO causes a substantial reduction of strong Brønsted acid sites. The hierarchical beta zeolite-supported Pt catalyst exhibits improved catalytic performance for the hydroisomerization of n-heptane.
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Residual electricity in spent lithium-ion batteries (LIBs) may cause safety issues during their dismantling and shredding in pretreatment processes. However, the migration and transformation of pollutants generated from spent LIBs during discharging were rarely reported, which is critical for prevention of pollution risk and facilitation of discharging efficiency. Herein, this work is focused on the evolution fate of battery chemistry during discharging processing. Here, migration of metal ions inside battery, galvanic corrosion on surface of battery and chemical evolution outside battery were investigated to attain the comprehensive understanding of discharging process. Firstly, efficient and complete discharging can be achieved using 5 wt% CuSO4 as discharging medium, which mainly drive the migration of Li, instead of transition metals, from anode to cathode, resulting in enrichment of Li in cathode material. Besides, different degrees of galvanic corrosion phenomena on surface of spent LIBs can be discovered in different electrolyte solutions, involving with the corrosion of Al or Fe shells and resulting in the leakage of organic electrolytes inside battery into electrolyte solution. The detailed characterization results of the composition of solute indicate that hydroxide precipitates liberated from corroded shell and organic pollutants are their main existence states.
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The circulating non-fried roast (CNR) technology was firstly applied to roast mutton. The formation of (non)volatile compounds in the mutton roasted for 0-15 min was investigated. The samples roasted at varying times were discriminated using GC-O-MS and multivariate data analysis. A total of 40 volatile compounds were observed, in which 17 compounds were considered as key odorants with odor activity values (OAVs) higher than 1, such as dimethyl trisulfide and 2-ethyl-3,5-dimethylpyrazine. Composition and concentrations of volatile compounds were significantly changed during the process. The key nonvolatile compounds that contributed to flavor were 5'-inosine monophosphate (5'-IMP) and glutamic acid based on taste active values (TAVs) greater than 1. The reduced concentrations of most free amino acids and 5'-nucleotides decreased the equivalent umami concentrations (EUC). The higher thermal conductivity, lower thermal diffusivity and water activity were responsible for the formation of volatile compounds with increased roasting times. The CNR technology was an efficient tool to roast meat products.
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Temperatura Alta , Compostos Orgânicos Voláteis , Compostos Orgânicos Voláteis/análise , Aromatizantes/análise , Odorantes/análise , Cromatografia Gasosa-Espectrometria de MassasRESUMO
Graphitic carbon nitride (g-C3N4)-supported V2O5 catalysts were prepared by the impregnation pyrolysis method, and their physicochemical properties were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FT-IR), Raman, X-ray photoelectron spectroscopy (XPS), UV-vis, TGA, N2 adsorption, and H2-TPR. These catalysts exhibit extremely high activity and selectivity in the aerobic oxidation of ethyl lactate to ethyl pyruvate. The excellent catalytic performance derives from the high surface-chemisorbed oxygen species. Low calcination temperature and interaction with g-C3N4 are conducive to increasing the surface-chemisorbed oxygen species of V2O5. The optimal catalyst 13V2O5/g-C3N4 gives 96.2% conversion of ethyl lactate with 85.6% selectivity toward ethyl pyruvate in 4 h at 130 °C and 1 atm oxygen, which is significantly superior to those of previously reported V-containing catalysts. This catalyst is also stable and reusable, and the ethyl pyruvate yield is reduced by less than 10% after four runs without any regeneration treatment.
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Visible-light-driven mesoporous bismuth titanate photocatalyst, which possesses wormlike channels, mixed phase mesostructured frameworks, large pore diameter (approximately 6.1 nm), and low band gap energy (2.5 eV), has been successfully prepared via a modified evaporation-induced self-assembly technique (EISA).
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The delamination and intercalation of a layered microporous aluminophosphate, [Al3P4O16](3-).3[CH3(CH2)NH3]+ (AlP), with aromatic amine have been carried out and were followed by XRD and SEM measurements. The basicity of the amine plays an important role in this process, as do the dielectric constant of the solution and the amount of amine added. A saturated benzylamine (pKa of 9.34) intercalate of the aluminophosphate are obtained in solutions with dielectric constant of 50-70 and an amine concentration of 10 mmol/g AlP, while no aniline (pKa of 4.60) intercalates are formed under similar conditions. The remarkable effect of basicity of the amine can be explained by a metathetical balanced reaction model, which was proved by the results of the intercalation processes of 4-methylpiridine (pKa = 6.00) and 4-methylimidazole (pKa = 7.55).
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Delamination and intercalation of a layered microporous aluminophosphate [Al3P4O16](3-) .3[CH3CH2NH3]+ (AlP) were carried out in water/ethanol/amine and water/methanol/amine solutions. A good colloidal dispersion and saturated amine intercalates of the aluminophosphate can be obtained in solutions with dielectric constants in the range 50-70 and an amine concentration of 10 mmol/g AlP. The saturated C2-C12 amine intercalates of AlP with an even number of carbon atoms are packed with alkylamine bilayers tilted at an angle of 44.8 degrees in the interlayer region.
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Ordered 2-D hexagonal mesoporous TiO(2)-SiO(2) nanocomposites consisted of anatase TiO(2) nanocrystals and amorphous SiO(2) nanoparticles, with large mesochannels and high specific surface areas, have been extensively and detailedly evaluated using various cationic dyes (methylene blue, safranin O, crystal violet, brilliant green, basic fuchsin and rhodamine-6G), anionic dyes (acid fuchsin, orange II, reactive brilliant red X3B and acid red 1) and microcystin-LR. We use mesoporous 80TiO(2)-20SiO(2)-900 for the degradation of cationic dyes and MC-LR, due to the dominant adsorption of SiOH groups and synergistic role of coupled adsorption and photocatalytic oxidation. For anionic dyes, due to the adsorption results predominantly from TiOH groups, our strategy realizes the enhanced photocatalytic oxidation by strong surface acids and larger available specific surface area. Based on this, we prepared 90TiO(2)-10SiO(2)-700 to degrade them. The results show that our samples exhibit excellent degradation activities to all the contaminants, which are much higher than that of P25 photocatalyst. The dyes are not only decolorized promptly but degraded readily as well. It is strongly indicated that our mesoporous nanocomposites are considerably stable and reusable. These results demonstrate that our mesoporous TiO(2)-SiO(2) nanocomposites present extensive and promising application in the fast and highly efficient degradation of various organic pollutants.
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Corantes/química , Microcistinas/química , Dióxido de Silício/química , Titânio/química , Poluentes da Água/química , Purificação da Água/métodos , Catálise , Toxinas Marinhas , Nanocompostos/química , Nanocompostos/efeitos da radiação , Oxirredução , Processos Fotoquímicos , Fotólise , Dióxido de Silício/efeitos da radiação , Titânio/efeitos da radiação , Raios UltravioletaRESUMO
MSU-S((BEA)) and MSU-S((Y)) mesoporous molecular sieves with different Si/Al ratios were prepared and characterized by XRD, XRF, N(2) adsorption, (27)Al MAS NMR, NH(3)-TPD and 2,6-di-tert-butyl-pyridine adsorption. Their catalytic behavior for the liquid phase isomerization of alpha-pinene has been investigated and compared with conventional zeolites and mesoporous molecular sieves. The activity correlates well with the amount of the accessible acid sites on the catalyst surface. MSU-S((BEA)) with Si/Al ratio of 67 has the highest activity in comparison to others. Ninty-seven percent conversion of alpha-pinene and 91% yield for main products like camphene, limonene, tricylene and terpinolene can be obtained at 70 degrees C. The catalyst is stable and reusable, and the product yield is only reduced by 10% after four runs, which is probably caused by the slow dealumination in the framework wall during the reaction.
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Monoterpenos/química , Zeolitas/química , Ácidos/química , Adsorção , Monoterpenos Bicíclicos , Catálise , Interações Hidrofóbicas e Hidrofílicas , Isomerismo , Espectroscopia de Ressonância Magnética , Nitrogênio/química , Porosidade , Temperatura , Difração de Raios XRESUMO
In this article, we report a controllable and reproducible approach to prepare highly ordered 2-D hexagonal mesoporous crystalline TiO2-SiO2 nanocomposites with variable Ti/Si ratios (0 to infinity). XRD, TEM, and N2 sorption techniques have been used to systematically investigate the pore wall structure, and thermal stability functioned with the synthetic conditions. The resultant materials are ultra highly stable (over 900 degrees C), have large uniform pore diameters (approximately 6.8 nm), and have high Brunauer-Emmett-Teller specific surface areas (approximately 290 m2/g). These mesostructured TiO2-SiO2 composites were obtained using titanium isopropoxide (TIPO) and tetraethyl orthosilicate (TEOS) as precursors and triblock copolymer P123 as a template based on the solvent evaporation-induced co-self-assembly process under a large amount of HCl. Our strategy was the synchronous assembly of titanate and silicate oligomers with triblock copolymer P123 by finely tuning the relative humidity of the surrounding atmosphere and evaporation temperature according to the Ti/Si ratio. We added a large amount of acidity to lower condensation and polymerization rates of TIPO and accelerate the rates for TEOS molecules. TEM and XRD measurements clearly show that the titania is made of highly crystalline anatase nanoparticles, which are uniformly embedded in the pore walls to form the "bricked-mortar" frameworks. The amorphous silica acts as a glue linking the TiO2 nanocrystals and improves the thermal stability. As the silica contents increase, the thermal stability of the resulting mesoporous TiO2-SiO2 nanocomposites increases and the size of anatase nanocrystals decreases. Our results show that the unique composite frameworks make the mesostructures overwhelmingly stable; even with high Ti/Si ratios (> or =80/20) the stability of the composites is higher than 900 degrees C. The mesoporous TiO2-SiO2 nanocomposites exhibit excellent photocatalytic activities (which are higher than that for commercial catalyst P25) for the degradation of rhodamine B in aqueous suspension. The excellent photocatalytic activities are ascribed to the bifunctional effect of highly crystallized anatase nanoparticles and high porosity.
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Nanoestruturas/química , Dióxido de Silício/química , Temperatura , Titânio/química , Catálise , Tamanho da Partícula , Fotoquímica , Porosidade , Propriedades de SuperfícieRESUMO
Monodisperse and high-surface-area mesoporous inorganic spheres of various compositions including metal oxides, mixed oxides, and metal phosphates are prepared by templating mesoporous carbon spheres which are replicated from spherical mesoporous silica. Due to the rigid and thermally stable framework of carbon template, the crystalline phases of the obtained metal oxide spheres can be readily tailored by controlling crystalline temperatures. Moreover, the sphere morphologies can be changed from solid structure to hollow structure in some cases by changing the polarity of the precursor, due to the hydrophobic nature of carbon template.