Triconstituent Co-assembly Method Research Articles

Ordered mesoporous silica-carbon-supported copper catalyst as an efficient and stable catalyst for catalytic oxidative carbonylation

Ordered mesoporous silica-carbon (MSC) nanocomposites with homogeneously distributed networks were synthesized by the triconstituent co-assembly method and used as supports of Cu catalysts for dimethyl carbonate (DMC) synthesis. The introduced silica contributes to the considerably increased pore size (∼5.8nm), the enhanced metal-support interaction and high dispersion of Cu nanoparticles (∼3.8nm) confined in the mesopores. An improved catalytic performance of Cu/MSC is achieved, reaching a DMC selectivity up to 90% at a methanol conversion of 1.5%, and a stable performance during five recycling runs. On the other hand, the benchmark Cu/MC catalyst undergoes a dramatic decrease of methanol conversion, from 1.3 to 1.0%, accompanied by a 27% reduction of DMC space-time yield (STYDMC). The mechanism through which the hybrid carrier affects the catalytic performance is analyzed using DFT calculations. The results show that the binding energy of Cu on MSC is greatly increased while the energy barrier to CO insertion for DMC formation is reduced evidently, thus enhancing the metal-support interaction and, in turn, the catalytic performance.

Bimodal highly ordered mesostructure carbon with high activity for Br2/Br− redox couple in bromine based batteries

Bimodal highly ordered mesostructure carbons (BOMCs) with excellent activity to Br2/Br− were designed and fabricated by an evaporation induced triconstituent co-assembly method. The morphologies of BOMCs were tuned via introducing dual templates: triblock copolymer (F127) and SiO2 nanoparticles, where around 5nm pores can be induced by hydrogen bond between resole and F127 and the removal of silica could create around 2nm pores on the 5nm pore walls. The highly ordered mesostructure can effectively shorten mass transfer distance and reduce mass transfer resistance. Meanwhile the around 2nm pores on 5nm pore walls are beneficial to Br2 adsorption and provide more active sites to Br2/Br− reaction. As a consequence, the materials demonstrate extremely outstanding performance to Br2/Br− couple. The zinc bromine flow batteries (ZBFBs) using the prepared carbon exhibit a voltage efficiency of 82.9% and an energy efficiency of 80.1% at the current density of 80mA cm−2, which is by far the best performance ever reported, confirming the excellent activity of designed materials. The results indicate that the prepared BOMC with bimodal highly ordered mesostructure is a very promising candidate for bromine based batteries systems.

Synthesis of mesoporous carbon–silica nanocomposite water-treatment membranes using a triconstituent co-assembly method

Mesoporous carbon–silica nanocomposite membranes with varying silica content demonstrate excellent performance in vacuum membrane distillation (VMD)-based desalination.

Enhanced charge storage by optimization of pore structure in nanocomposite between ordered mesoporous carbon and nanosized WO3−x

Herein, we report preparation of a novel ordered mesoporous carbon/reduced tungsten oxide nanocomposite by post-addition into the ordered mesoporous carbon prepared by triconstituent co-assembly method. The as-prepared composite material is characterized using various analysis methods and nitrogen sorption isotherms, which reveal that small mesopores located within pore wall are selectively filled by tungsten oxide and also reduced tungsten oxide crystals with size of 6 nm are uniformly dispersed in the carbon matrix. Hence, our prepared nanocomposite possesses an ordered pore structure optimized for fast electrolyte transport and highly accessible charge storage sites. When applied as supercapacitor electrode, it exhibits a high volumetric capacity (125Fcm−3), an excellent rate capability (79%) and capacitance increase after long-term cycles (113%).

Direct tri-constituent co-assembly of highly ordered mesoporous carbon counter electrode for dye-sensitized solar cells

Controlling over ordered porosity by self-assembly is challenging in the area of materials science. Materials with highly ordered aperture are favorable candidates in catalysis and energy conversion device. Here we describe a facile process to synthesize highly ordered mesoporous carbon (OMC) by direct tri-constituent co-assembly method, which uses resols as the carbon precursor, tri-block copolymer F127 as the soft template and tetraethoxysilane (TEOS) as the inorganic precursor. The obtained products are characterized by small-angle X-ray diffraction (SAXD), Brunauer-Emmett-Teller (BET) nitrogen sorption-desorption measurement and transmission electron microscope (TEM). The results indicate that the OMC possesses high surface areas of 1209 m(2) g(-1), homogeneous pore size of 4.6 nm and a large pore volume of 1.65 cm(3) g(-1). The advantages of high electrochemical active surface area and favorable accessible porosity of OMC benefit the catalysis of I(3)(-) to I(-). As a result, the OMC counter electrode displays a remarkable property when it was applied in dye-sensitized solar cells (DSSCs). For comparison, carbon black (CB) counter electrode and Pt counter electrode have also been prepared. When these different counter electrodes were applied for dye-sensitized solar cells (DSSCs), the power-conversion efficiency (η) of the DSSCs with CB counter electrode are measured to be 5.10%, whereas the corresponding values is 6.39% for the DSSC with OMC counter electrode, which is comparable to 6.84% of the cell with Pt counter electrode under the same experimental conditions.

Studies on Adsorption of Phenol onto Ordered Mesoporous Carbon Prepared by Evaporation-Induced Triconstituent Co-assembly Method

Studies on Adsorption of Phenol onto Ordered Mesoporous Carbon Prepared by Evaporation-Induced Triconstituent Co-assembly Method

A new restriction effect of aging time on the shrinkage of ordered mesoporous carbon during carbonization

A new effect of aging time (AT) on the shrinkage of ordered mesoporous carbon (OMC) prepared by an evaporation-induced triconstituent co-assembly method has been reported. Increasing AT from 0.5 to 2.0 h can gradually reduce framework shrinkage of the OMC during carbonization. This novel effect is effective and simple for preparing the OMC with large mesopore sizes, high pore volumes and surface area.

Influence of Preparation Conditions on Structural Stability of Ordered Mesoporous Carbons Synthesized by Evaporation-induced Triconstituent Co-assembly Method

Various ordered mesoporous carbons (OMCs) have been prepared by evaporation-induced triconstituent co-assembly method. Their mesostructural stability under different carbon content, aging time and acidity were conveniently monitored by X-ray diffraction, transmission electron microscopy, and N2 sorption isotherms techniques. The results show mesostructural stability of OMCs is enhanced as the carbon content increases from 36% to 46%, further increasing carbon content deteriorates the mesostructural stability. Increasing aging time from 0.5 h to 5.0 h make the mesostructural stability go through an optimum (2.0 h) and gradually reduce framework shrinkage of the OMCs. Highly OMCs can only be obtained in the acidity range of 0.2–1.2 mol/L HCl, when the acidity is near the isoelectric point of silica, the resulting OMCs have the best mesostructure stability. Under the optimum condition, the carbon content of 46%, aging time of 2.0 h, and 0.2 mol/L HCl, the resulting OMCs have the best mesostructure stability and the highest BET surface areas of 2281 m2/g.

Mesoporous tungsten carbide-supported platinum as carbon monoxide-tolerant electrocatalyst for methanol oxidation

This paper reports a CO-tolerant electrocatalyst, mesoporous tungsten carbide-supported platinum (Pt/m-WC), for methanol oxidation. The support m-WC was synthesized by evaporation-induced triconstituent co-assembly method in which phenol formaldehyde polymer resin was used as the carbon precursor, tungsten hexachloride as the tungsten precursor and an amphiphilic triblock copolymers (P123) as the template. Nano-sized platinum particles were loaded on the m-WC to prepare Pt/m-WC. The structure and morphology of the prepared electrocatalyst were characterized by transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET) and X-ray diffraction (XRD), and its activity toward methanol oxidation and its tolerance for CO were determined by cyclic voltammetry (CV) and chronopotentiometry (CP). It is found that the m-WC carburized at 900 °C(m-WC-900) has a larger specific surface area (182 m2 g−1) and a appropriate crystal structure compared to the m-WC carburized at 800 °C or 1000 °C, and thus is better as the support of platinum. The prepared Pt/m-WC-900 exhibits higher activity toward methanol oxidation and better tolerance for CO than Pt/Vulcan XC-72. The onset potential of CO electro-oxidation on Pt/m-WC is 0.449 V, which is more negative than that on Pt/Vulcan XC-72 (0.628 V).

White light emitting Mesoporous Carbon-Silica Nanocomposite

Visible photoluminescence (PL) from oxidized mesoporous carbon-silica nanocomposite (MPCS) prepared by the triconstituent co-assembly method is reported. White PL from MPCS was observed by naked eye at room temperature. Oxidation effects on carbon-silica bonding states and transmittance were investigated. PL intensity decreased with decreasing of carbon dangling bond density by oxidation at above 500 °C. The transmittance of MPCS at excitation and emission wavelengths increased with increasing of oxidation temperature. It is concluded that PL intensity is determined by the balance between PL related carbon density and transmittance. We proposed an additional wet oxidation that can increase PL intensity by the increase of transmittance under suppressing carbon desorption.

Ordered mesoporous carbon/sulfur nanocomposite of high performances as cathode for lithium–sulfur battery

Ordered mesoporous carbon/sulfur (OMC/S) nanocomposites with hierarchically structured sulfur loading, ranging from 50 to 75 wt%, were synthesized via a simple melt-diffusion strategy. The OMC with a BET surface area of 2102 m 2 g −1, a pore volume of 2.0 cm 3 g −1 and unique bimodal mesoporous (5.6/2.3 nm) structure, was prepared from a triconstituent co-assembly method. The resulting OMC/S nanocomposite material served as cathode of rechargeable lithium–sulfur (Li–S) battery. It has been tested that the novel OMC/S cathode can deliver a superior reversible capacity and cyclability. In particular, the nanocomposite with a loading of 60 wt% sulfur (OMC/S-60) presents the highest sulfur utilization ca. 70%, an excellent high rate capability ca. 6 C and a good cycling stability for up to 400 full charge–discharge cycles. The exceptional electrochemical performances are exclusively attributed to the large internal surface area and high porosity of the ordered mesoporous carbon, which favorites both electron and Li-ion transportations.

White Light Emission from Mesoporous Carbon–Silica Nanocomposites

Visible photoluminescence properties of mesoporous nanocomposites of carbon and silicon dioxides prepared using the triconstituent co-assembly method is reported. Intense white-light emission from the nanocomposites was observed at room temperature, under 370-nm light irradiation after proper carbon desorption by air-oxidation. We observed that the shapes of the luminescence spectra, especially in the green-yellow region, were highly dependent on the oxidation condition of the samples.

Synthesis of ordered mesostructured polymer–organosilica composites by the triconstituent co-assembly method

Ordered mesoporous polymer–organosilica composites have been synthesized through a triconstituent co-assembly strategy. These composites have ordered 2-D hexagonal mesostructures (space group p6m) with uniform pore size (6.2–7.3 nm), suitable surface areas (619–794 m 2 g −1) and pore volumes (0.61–0.88 cm 3 g −1). With increasing BTSE (1,2-bis(triethoxysilyl)ethane) content, the surface area and pore volume reduce. The composites have homogeneous interpenetrating frameworks, in which both polymer and organosilica synergistically support the ordered mesostructure. The hybrid materials exhibit good adsorption capacities of benzene (up to 2.0 mmol g −1), suggesting their use as a potential adsorbent for removal of volatile organic compounds.

Microwave absorption properties and infrared emissivities of ordered mesoporous C–TiO 2 nanocomposites with crystalline framework

Ordered mesoporous C–TiO 2 nanocomposites with crystalline framework were prepared by the evaporation-induced triconstituent co-assembly method. The products were characterized by XRD, TEM, N 2 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–TiO 2 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–TiO 2 nanocomposites also exhibit a lower infrared emissivity in the wavelength from 8 to 14 μm than that of TiO 2-free powder.

Electromagnetic wave absorption and infrared camouflage of ordered mesoporous carbon–alumina nanocomposites

Ordered mesoporous C–Al 2O 3 nanocomposites with different alumina contents were prepared via evaporation-induced triconstituent co-assembly method. As shown by X-ray diffraction (XRD), N 2 adsorption–desorption and transmission electron microscopy (TEM), the C–Al 2O 3 nanocomposites exhibit ordered mesoporous structures, and the results indicate that the carbon as amorphous components in the mesostructured framework can stabilize the ordered mesostructures of the nanocomposites. Furthermore, the electromagnetic wave absorption properties and infrared emissivities of the ordered mesoporous C–Al 2O 3 nanocomposites were examined systematically. It was observed that the mesoporous nanocomposites have excellent electromagnetic wave absorption properties and low infrared emissivities. For example, the sample with 50 wt.% Al 2O 3 achieves a maximum reflection loss of −15.3 dB and the bandwidths being lower than −10 dB is 7.4 GHz with a thickness of 3 mm in 0.5–18 GHz, whereas its infrared emissivity can reach 0.46 in the wavelength range from 8 to 14 μm.

Mesoporous carbon–titania nanocomposites for high-power Li-ion battery anode material

We have investigated the Li-ion battery anode properties of several kinds of mesoporous composites of carbon and titanium dioxides (titania, TiO 2) prepared by tri-constituent co-assembly method. The maximum reversible capacity (197 mAh/g) at current density of 50 mA/g was obtained for the composite of TiO 2:carbon=7:3 calcined at 600 °C. It was also found that the composite maintained the high reversible capacity as large as 109 mAh/g even at the high current density of 1000 mA/g.

A “teardown” method to create large mesotunnels on the pore walls of ordered mesoporous silica

A “teardown” method to create large mesotunnels (∼9 nm) on the pore walls of ordered mesoporous silicas is demonstrated by digesting the organic constituents from polymer–silicate nanocomposites. The ordered mesostructured polymer–silicate composites were first obtained via the evaporation-induced triconstituent co-assembly method by using a low-molecular-weight phenolic resin (resols) as an organic precursor; prehydrolyzed TEOS as an inorganic precursor, and triblock copolymer F127 as a template. All of organic components including F127 and phenolic resins are removed by the microwave digestion (MWD) method from mesostructured polymer–silica composites. While the removal of triblock copolymer F127 generates main pore channels, the phenolic resins can also be torn down from the pore walls, yielding mesotunnels between the channels. The resulting silica products exhibit ordered 2-D hexagonal mesostructure, large pore volume (up to 1.92 cm 3/g), and very large pore size (up to 22.9 nm), which is even larger than their mesostructural cell parameter (14.2 nm). TEM images confirm the existence of mesotunnels on the silica pore walls. FT-IR and 29Si solid-state NMR results reveal that these silica products have a large number of silanol groups.

Electrochemical properties of an ordered mesoporous carbon prepared by direct tri-constituent co-assembly

An ordered mesoporous carbon with a high surface area of 2390 m 2/g and a large pore size of 6.7 nm was synthesized through an organic–inorganic-surfactant tri-constituent co-assembly method which used resols as the carbon precursor, silicate oligomers as the inorganic precursor and triblock copolymer as the soft template. The electrochemical properties of this carbon were evaluated as an electrode material for electrochemical double layer capacitor and lithium-ion battery. It shows rectangular-shaped cyclic voltammetry curves over a wide range of scan rates even up to 200 mV/s between 0 and 3 V, with a large capacitance of 112 F/g in nonaqueous electrolyte. As a negative electrode material for lithium-ion battery, it delivers a reversible specific capacity as high as 1048 mAh/g and a good cycling ability with capacity retention of 500 mAh/g over 50 cycles.

Triconstituent Co-assembly to Ordered Mesostructured Polymer−Silica and Carbon−Silica Nanocomposites and Large-Pore Mesoporous Carbons with High Surface Areas

Highly ordered mesoporous polymer-silica and carbon-silica nanocomposites with interpenetrating networks have been successfully synthesized by the evaporation-induced triconstituent co-assembly method, wherein soluble resol polymer is used as an organic precursor, prehydrolyzed TEOS is used as an inorganic precursor, and triblock copolymer F127 is used as a template. It is proposed for the first time that ordered mesoporous nanocomposites have "reinforced concrete"-structured frameworks. By adjusting the initial mass ratios of TEOS to resol, we determined the obtained nanocomposites possess continuous composition with the ratios ranging from zero to infinity for the two constituents that are "homogeneously" dispersed inside the pore walls. The presence of silicates in nanocomposites dramatically inhibits framework shrinkage during the calcination, resulting in highly ordered large-pore mesoporous carbon-silica nanocomposites. Combustion in air or etching in HF solution can remove carbon or silica from the carbon-silica nanocomposites and yield ordered mesoporous pure silica or carbon frameworks. The process generates plenty of small pores in carbon or/and silica pore walls. Ordered mesoporous carbons can then be obtained with large pore sizes of approximately 6.7 nm, pore volumes of approximately 2.0 cm(3)/g, and high surface areas of approximately 2470 m(2)/g. The pore structures and textures can be controlled by varying the sizes and polymerization degrees of two constituent precursors. Accordingly, by simply tuning the aging time of TEOS, ordered mesoporous carbons with evident bimodal pores at 2.6 and 5.8 nm can be synthesized.