Search

An open-tubular radially cyclical electric field-flow fractionation technique which achieves the online separation of microparticles in a functional annular channel is proposed in this study. The system was set up by using a stainless steel tube and a platinum wire modified with ionic liquid/mesoporous silica materials as the external and internal electrodes. The feasibility for online separation of various particles was experimentally demonstrated. Particles in the channel were affected by a radial electric field and field-flow fractionation (FFF). On the cross section, different particles showed distinctive migration distances depending on their own properties and the different magnitudes of forces being exerted. The same kind of particles form an annular distribution within the same annulus while different particles form annular distributions at varied concentric annuli through electrophoresis. Under a laminar flow of FFF, different sizes of particles formed a conical arrangement within the annular separation channel. With the joint influence of electric field and flow field, different trajectories were obtained and the particles were eventually separated. Voltage, frequency and duty cycle value are the main parameters affecting the separation of particles. By adjusting these parameters, particles migrate in a zigzag trajectory on one side of the electrodes (mode I) and reach both sides of the electrodes (mode II). Six polystyrene particles were completely separated with high resolution within several minutes. Our system offers numerous advantages of label-free, high-resolution and online separation without tedious operations, and it is a promising tool for the effective separation of various micro-objects. [ABSTRACT FROM AUTHOR]

Abstract: Mesoporous silica KIT-6-, SBA-15-, and MCM-41-supported Ni catalysts (Ni/KIT-6, Ni/SBA-15, and Ni/MCM-41) were prepared via impregnation method and studied for CO2 reforming of CH4. The catalysts were characterized by X-ray diffraction analysis, N2 physisorption measurements, scanning electron microscopy, transmission electron microscopy, and temperature-programmed oxidation (O2-TPO). The Ni/KIT-6 catalyst exhibited higher catalytic activity and long-term stability compared with Ni/SBA-15 or Ni/MCM-41. The conversion of CH4 and CO2 over Ni/KIT-6 was 99 and 99 %, respectively. The superior catalytic behavior of Ni/KIT-6 is closely related to the large-pore cubic Ia3d structure of KIT-6, which enhanced dispersion of Ni nanoparticles, reduced carbon deposition, and increased diffusion of reactant and products.Graphical Abstract: [ABSTRACT FROM AUTHOR]

Oxidative desulfurization (ODS) of organic compounds containing sulfur element from a model oil was performed using tungsten oxide catalysts supported on mesoporous silica with cubic Ia3d mesostructure, well-defined mesopores (7.2 nm), high surface area (719 m2/g), and three-dimensional pore network (WOx/KIT-6). The prepared WOx/KIT-6 catalysts (5-20 wt% WOx) were characterized by X-ray diffraction analysis, N2 sorption measurements, electron microscopy, H2-temperature programmed reduction, Raman spectroscopy, and thermogravimetric analysis. Among the mesoporous catalysts, 10 wt% WOx/KIT-6 exhibited the best catalytic performance. Sulfur-containing organic compounds, such as dibenzothiophene, 4,6-dimethyldibenzothiophene, and benzothiophene, were completely (100 %) removed from the model oil over 10 wt% WOx/KIT-6 catalyst in 2 h. In addition, the catalyst could be reused several times with only slight decrease in catalytic activity. [ABSTRACT FROM AUTHOR]

Lithiation-delithiation reactions in Li-ion batteries do exhibit a huge electrochemically driven volume change of the anode material between the lithium-free and lithiated-host states, which results in a gradually fading capacity. Minimizing this volume change of the electrode during cycling is essential to achieve stable electrochemical behavior and thus for innovating design of electrode materials for Li storage. Here, ordered mesoporous CoSn intermetallic anode materials with various Co/Sn atomic ratios are developed. A dual-buffer effect is discovered that accommodates the volume changes in the electrode material by not only repeatedly generating void nanospaces but also by incorporating electrochemically inactive elements. Novel insights into the nanostructural changes of electrode materials during the lithiation-delithiation process are obtained by in operando small angle X-ray scattering. The degrees of volume change and nanoscopic order are found to be highly dependent on the Co contents in the mesoporous CoSn intermetallic anode materials, being possible to achieve a durable nanostructured electrode upon prolonged cycling. [ABSTRACT FROM AUTHOR]

Highly ordered mesoporous antimony-doped tin oxide (ATO) materials, containing different amount of antimony in the range of 0-50mol%, are prepared via a nanoreplication method using a mesoporous silica template. The mesoporous ATO materials thus obtained exhibit high electrical conductivity, high reversible capacity, superior cycle stability and good rate capability as anode materials for lithium-ion batteries, compared to those of pure mesoporous tin oxide. Amongst the ATO materials in this work, the mesoporous ATO material with 10mol% of antimony has highest discharge capacity of 1940mAhg-1 (charge capacity of 1049) at the 1st cycle, best cycle performance (716mAhg-1 at 100th cycle) and excellent rate capability, which are probably due to the enhanced electrical conductivity as well as reduced crystalline size. Ordered mesoporous antimony-doped tin oxide (ATO) materials with Ia3d mesostructure were obtained using nanoreplication method. The electrical conductivity of meso-ATO-10 is drastically enhanced, compared to that of meso-ATO-0. Moreover, the Sb-doping results in the high capacity retention (67% at 100th cycle) as well as excellent rate capability. We believe that the Sb-doping reduces the possibility of aggregation of the metallic tin toward larger crystals and accommodates the electrochemically induced volume change during Li alloying-dealloying process. [ABSTRACT FROM AUTHOR]

Highly ordered mesoporous tungsten trioxide (WO3) with high surface area (75 m2/g) and well-defined mesopores were successfully prepared through a hard templating method using a mesoporous silica KIT-6 as a template and (NH4)6H2W12O40 ⋅ xH2O as a tungsten precursor. Oxidative desulfurization of a model oil with H2O2 as the oxidant was carried out at 50°C under atmospheric pressure in order to analyze the catalytic activity. The desulfurization reactions were optimized by various kinds of reaction parameters such as H2O2/S molar ratio, reaction temperatures and series of sulfur-containing compounds [dibenzothiophene (DBT), benzothiophene (BT) and 4,6-dimethyl dibenzothiophene (4,6-DMBT)]. Excellent catalytic activity for the removal of the sulfur-containing compounds from the model oil was observed with mesoporous WO3 catalyst, where the activity was maintained during 5 recycle tests without any regeneration process. The high catalytic activity and durability is mainly attributed to well-defined mesopores and high surface area of mesoporous WO3 catalyst. [ABSTRACT FROM AUTHOR]

Ordered mesoporous MCo 2 O 4 (M = Cu, Zn and Ni) spinel catalysts were synthesized via nano-replication method using mesoporous silica KIT-6 as the hard template. They were applied to methane combustion, in comparison with bulk MCo 2 O 4 spinel catalysts prepared by co-precipitation method. A combined N 2 adsorption-desorption, XRD and TEM results clearly confirm that mesoporous MCo 2 O 4 (m-MCo 2 O 4 ) spinel catalysts contain ordered mesostructure, resulting in the higher BET surface area and pore volume than bulk ones (b-MCo 2 O 4 ). Moreover, the former catalysts demonstrate the better thermal stability as indicated by larger amount of MCo 2 O 4 phase and smaller size of crystallite domain after calcination at 550 °C. Therefore, such excellent properties rationalize that the m-MCo 2 O 4 spinel catalysts reveal higher catalytic activity for methane combustion than bulk counterparts. When it comes to the catalytic performance of the meso catalysts for methane combustion, the m-CuCo 2 O 4 spinel catalyst has superior performance, which is related to the high normalized amount of Co 3+ cations on the surface, as evidenced by XPS. [ABSTRACT FROM AUTHOR]

In order to develop high energy density Li rechargeable batteries, nano-sized materials have attracted attention as the active materials. Mesoporous materials consist of the micrometre-sized particles, and they have high surface area due to their mesopore and thin wall thickness of framework. Here, we synthesize a highly ordered mesoporous RuO 2 to investigate the effect that the mesoscopic structure has on the capacity and their corresponding reaction mechanism of Li rechargeable battery. The synthesized mesoporous RuO 2 shows an initial discharge capacity of 1366 mAh g −1 on mesoporous RuO 2 , which is higher than that of commercial RuO 2 . Our findings via In situ X-ray analysis techniques combined with electrochemical analysis demonstrate that the additional capacity of mesoporous RuO 2 is resulted from the enhanced interfacial reaction between Ru metal and Li 2 O formed by conversion reaction of RuO 2 . Nano-size effects of mesoporous structure such as high surface area, easy electron transport, and small domain would enable to improve the interfacial reaction of highly ordered mesoporous RuO 2 . The understanding of this relationship between structural engineering and electrochemical properties provides the insight into development of high energy density anode materials in next generation Li rechargeable battery. [ABSTRACT FROM AUTHOR]

Abstract: Mesoporous silica KIT-6-, SBA-15-, and MCM-41-supported Ni catalysts (Ni/KIT-6, Ni/SBA-15, and Ni/MCM-41) were prepared via impregnation method and studied for CO2 reforming of CH4. The catalysts were characterized by X-ray diffraction analysis, N2 physisorption measurements, scanning electron microscopy, transmission electron microscopy, and temperature-programmed oxidation (O2-TPO). The Ni/KIT-6 catalyst exhibited higher catalytic activity and long-term stability compared with Ni/SBA-15 or Ni/MCM-41. The conversion of CH4 and CO2 over Ni/KIT-6 was 99 and 99 %, respectively. The superior catalytic behavior of Ni/KIT-6 is closely related to the large-pore cubic Ia3d structure of KIT-6, which enhanced dispersion of Ni nanoparticles, reduced carbon deposition, and increased diffusion of reactant and products.Graphical Abstract: [ABSTRACT FROM AUTHOR]

We describe the synthesis and characterization of hierarchically porous organic-inorganic hybrid silica with periodic 2-D hexagonal order and tunable location of secondary nanopores through co-condensation of tetraethylorthosilicate (TEOS) and a new type of amphiphilic organosilicate precursors. Our amphiphilic organosilicates offer unique tunability of secondary micropores by carefully controlled bond molecular structure and number of bonds between hydrophobic adamantylphenols pore-generating moieties and siloxane precursors. Small angle X-ray scattering (SAXS) and microscopy results show a good structural order of the organic-inorganic hybrid silica. In addition, 29 Si CP-MAS NMR spectra confirm the successful incorporation of organosilicate precursors into a silica framework. The primary cylindrical mesopores (∼6.4 nm) were originated from the cooperative self-assembly of Pluronic P123 triblock copolymer templates while smaller meso-/micropores were derived from adamantylphenols groups. We have previously demonstrated that adam-graft SQ had an affinity for hydrophobic PO core blocks to be located close to PO segment, which resulted in small pores next to primary mesopores and the resultant increment of mesopore size as well as wrinkled silica walls. On the contrary, the secondary small pores were mainly generated within a silica network while the size of the primary mesopores unaffected with the addition of adam-bridge SQ due to its selective incorporation into a silica framework. Moreover, the organic-inorganic hybrid silica prepared with adam-bridge SQ showed higher thermal stability than that of adam-graft SQ and SBA-15 type mesoporous silica. It is attributed to more Si O Si bonds formed from the bridged structure as well as enhanced hydrogen-bonding interaction between adam-bridge SQ hybrid silica and P123 templates. [ABSTRACT FROM AUTHOR]