Enhanced microwave absorption properties of Ni-doped ordered mesoporous carbon/polyaniline nanocomposites

We propose and demonstrate a new scheme to improve microwave absorption property through polyaniline (PANI)-functionalized Ni-doped ordered mesoporous carbon (OMC) by in situ polymerization method. The polymer-functionalized nanocomposites, embedding polyaniline within ordered mesoporous carbon, exhibit strong and broadband microwave absorption due to its better dielectric loss characteristic. OMC-Ni0.15/PANI exhibits an effective absorption bandwidth (i.e., reflection loss (RL) ≤ −10 dB) of 4.7 GHz and an absorption peak of −51 dB at 9.0 GHz. The absorption peak intensity and position can be tuned by controlling the thickness of the coating.     

High rate capability of ordered mesoporous carbon with platelet graphitic pore walls for lithium ion anodes

An ordered mesoporous carbon (OMC) with controllable molecule crystal and platelet graphitic pore walls, which is directionally grown on the internal pore walls of SBA-15 or anchors at liquid/silica interfaces by molecule engineering, has been investigated as lithium ion anodes. It is found that the OMC exhibits high kinetics, rate and cycling performance. The i₀ and D_Li are almost constant after 50 cycles. OMC shows a high reversible specific capacity of 153.9 mAh g^-1 at the current density as high as 3500 mA g^-1. The excellent electrochemical performance could be attributed to the presence of the porosity and platelet graphitic pore walls.     

Preparation and dielectric properties of a polyurethane elastomer filled with resol-derived ordered mesoporous carbon

This study deals with the preparation and dielectric properties of polyurethane (PU) elastomer films by resol-derived ordered mesoporous carbon (OMC) nanopowder incorporation in the PU polymer matrix. Resol-derived OMC with a 2D hexagonal mesoporous carbon framework is used as conducting fillers to achieve homogeneous dispersion and favorable interfacial interactions in the polymer matrix. The dielectric properties depend on the applied field frequency and the carbon filler weight fraction. The carbon fraction has little effect on the relative permittivity. The relative permittivity of all the PU-OMC composites increases with the decline of frequency. Incorporating a small amount of OMC into the PU polymer had no influence on the dielectric loss. Along with the increasing carbon fraction above the percolation threshold, dielectric loss of PU-OMC composites increases exponentially in the low frequency range. PU-0.75 wt% OMC composite possesses the best dielectric properties, and the obtained relative permittivity and dielectric loss at 1 kHz is 9.59 and 0.03018, respectively.     

Synthesis of ordered mesoporous Pd/carbon catalyst with bimodal pores and its application in water-mediated Ullmann coupling reaction of chlorobenzene

Heterogeneous palladium catalysts have been supported on the ordered mesoporous carbons (Pd/OMC) with bimodal pores which are prepared by the surfactant-templating approach. Characterization using XRD, TEM, XPS, H₂ chemisorption, and N₂ sorption techniques reveals that the Pd/OMC catalysts have the ordered 2-D hexagonal mesostructure (space group of p6mm), extremely high surface areas (~1800 m²/g), large pore volumes (~1.64 cm³/g), bimodal pores (6.3 nm of primary mesopores and 1.7 nm of secondary mesopores inside the pore walls), hydrophobic carbon surface, and small metal particles well-dispersed inside the secondary small mesopores. This catalyst exhibits a high yield of 43% for biphenyl from the Ullmann coupling reaction of chlorobenzene in water at 100 °C without assistance of any phase transfer catalyst and can be reused up to 10 times, providing potential opportunities for industrial applications such as coupling and hydrogenation reactions.     

Preparation of hydrophilic mesoporous carbon and its application in dye adsorption

A hydrophilic mesoporous carbon (H-MS) has been prepared by a rapid redox reaction between mesoporous carbon (CMK-3) and an acidic potassium permanganate (KMnO₄) solution at room temperature. The obtained material has a hydrophilic surface by the modification of oxygen-containing groups, and meanwhile retains the ordered mesoporous structure. No obvious difference of pore size between H-MS and CMK-3, and the slight decrease of surface area and pore volume is due to the modification of oxygen-containing groups on the carbon surface. An improved property for adsorbing dyes in aqueous solution was observed in H-MC, and the adsorption amount at equilibrium is ~ 3 times higher than that of CMK-3.     

基于有序介孔碳/PDDA固定化漆酶的邻苯二酚传感器性能研究

采用有机交联水性环氧树脂为碳源,以SBA-15为模板,制备了有序介孔碳(OMC),并对其电化学性能进行研究。透射电镜结果表明其具有典型的二维有序六角介孔结构,孔径大约为3nm。电化学测试结果表明OMC/Lac/Au电极对邻苯二酚具有很好的电催化氧化活性。将OMC应用于构建漆酶生物传感器,结果表明,传感器对邻苯二酚的线性检测范围为0.67~8.59μmol/L,灵敏度为0.349A/(mol/L),检测限为0.117μmol/L。     

结构有序、双重孔隙中孔炭材料的合成与表征

采用纳米涂层技术,以介孔分子筛SBA 15为模板,在其纳米孔道内引入糠醇/草酸溶液,经原位聚合,炭化后制得炭/SBA 15复合物。采用化学法脱除模板后制得具有规则结构的中孔炭。高分辨TEM表征结果显示该中孔炭是由纳米炭管相互联接、堆积而成,且具有六方对称结构。氮吸附结果显示其比表面积高达2000m2/g,孔径呈双峰分布。孔径相对较大的孔隙来源于SBA 15孔道经纳米涂层后所保留的孔隙;孔径相对较小的孔隙来源于SiO2移除后遗留的纳米孔空间。该方法可应用于以其他多孔氧化硅为模板制备新型纳米复合物的研究过程。     

Simple and efficient CVD synthesis of graphitic P-doped 3D cubic ordered mesoporous carbon at low temperature with excellent supercapacitor performance

Heteroatom doping is a promising strategy for improving the electrochemical performance of carbon materials. Herein, we spotlight an advantageous, simple, and efficient CVD synthesis of P-doped 3D cubic ordered mesoporous carbon (POMC) for the first time. The POMC was prepared by pyrolysis of acetylene/triphenylphosphine (C₂H₂/Ph₃P) mixture at relatively low temperature over Fe-KIT-6 as a sacrificial template. The ensuing P-doped OMC showed an enhanced porous texture than an undoped counterpart with a specific surface area of 403.5 m²/g, pore volume of 0.545 cm³/g, average pore size of 4.64 nm and suitable heteroatom functionalities with P and O contents of 0.13% and 9.83%, correspondingly. The obtained POMC exhibited a much higher specific capacitance of 288F/g at 0.2 A/g (175F/g for OMC), good cyclic stability of 97.6 %, and good rate capability than pristine OMC in 6 M KOH. It is equivalent to or improved than various stated mono doped and even dual doped porous carbon electrodes. Furthermore, a symmetric supercapacitor (POMC//POMC) was fabricated with 1 M Na₂SO₄ aqueous neutral electrolyte exhibits high cycling stability (89.3%) even with a wide potential window (2.0 V) and offers a relatively high energy density (10.01 Wh/kg) with a power density of 300 W/kg.     

Amorphous Mn oxide-ordered mesoporous carbon hybrids as a high performance electrode material for supercapacitors

A supercapacitor has the advantages of both the conventional capacitors and the rechargeable batteries. Mn oxide is generally recognized one of the potential materials that can be used for a supercapacitor, but its low conductivity is a limiting factor for electrode materials. In this study, a hybrid of amorphous Mn oxide (AMO) and ordered mesoporous carbon (OMC) was prepared and characterized using X-ray diffraction, transmission electron microscopy, N2/77 K sorption techniques, and electrochemical analyses. The findings indicate that the electrochemical activities of Mn oxide were facilitated when it was in the hybrid state because OMC acted as a pathway for both the electrolyte ions and the electrons due to the characteristics of the ordered mesoporous structure. The ordered mesoporous structure of OMC was well maintained even after hybridization with amorphous Mn oxide. The electrochemical-activity tests revealed that the AMO/OMC hybrid had a higher specific capacitance and conductivity than pure Mn oxide. In the case where the Mn/C weight ratio was 0.75, the composite showed a high capacitance of 153 F/g, which was much higher than that for pure Mn oxide, due to the structural effects of OMC.     

The effects of activation method on the pore structure and electrochemical properties of ordered mesoporous carbons used as the electrode materials of supercapacitors北大核心CSCD

An ordered mesoporous carbon. (OMC) synthesized by the soft-template method was activated by (a) CO2 at 900 degrees C for 4 h, (b) H2O at 800 degrees C for 20 min, and (c) H2O at 800 degrees C for 20 min followed by CO2 at 900 degrees C for 4 h to produce three micro-mesoporous carbons, A1, A2 and A3, respectively. Their pore structures were investigated by XRD, TEM, SEM and N-2 adsorption. Their electrochemical properties as the electrode materials of supercapacitors were investigated by cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy. Results indicated that the highly ordered 2D hexagonal original mesostructure of the OMC was well retained after activation. The increasing order of the extent of activation is A1相似文献   

利用线性酚醛树脂制备有序介孔碳

三嵌段共聚物F127为模板剂,线性酚醛树脂为碳前驱体,采用溶剂挥发诱导有机-有机自组装法(EI-SA)制备了具有二维六方结构的有序介孔碳。利用FT-IR、XRD、TEM、N2吸附/脱附等方法对有序介孔碳的结构进行了表征,研究了不同焙烧温度和模板剂用量对有序介孔碳结构的影响。结果表明,当模板剂的用量一定时,有序介孔碳的孔径、孔容和孔壁厚度都随着焙烧温度的升高而降低,但比表面积却随着微孔含量的增加而增大。随着模板剂用量的增加,介孔碳的有序性降低。有序介孔碳PF-2-500的比表面积、孔径、孔容、孔壁厚度和微孔比表面积比分别为583.82m2/g、3.05nm、0.31cm3/g、3.40nm和361.18m2/g,而有序介孔碳PF-1-500的比表面积、孔径和孔容相对于PF-2-500有所提高,分别为647.79m2/g、3.44nm和0.41cm3/g,但微孔比表面积和孔壁厚度分别降低为309.46m2/g和3.35nm。     

高性能超级电容器有序中孔炭材料的研制

采用微湿含浸法制备了一系列具有不同比表面积和孔径分布的超级电容器有序中孔炭材料。采用液氮吸附脱附等温线、小角XRD以及TEM表征了有序中孔炭的孔结构,在1MEt4NBF4|PC电解液中测试了其电化学性能。结果表明,所制得的有序中孔炭的BET比表面积随糠醇加入量的增加先增加后减小,糠醇加入量少制得具有CMK-5结构的有序中孔炭,加入量多制得的CMK-3结构。电化学性能测试结果表明,在1mA·cm-2的充放电电流密度下各有序中孔炭材料比电容的大小顺序与其BET比表面积的大小顺序基本一致,具有CMK-3结构的有序中孔炭的倍率性能最好,并且也好于无序中孔炭的。     

Mesoporous indium oxide synthesized via a nanocasting route

The synthesis of crystalline mesoporous indium oxide by using a mesoporous carbon (CMK-3) as hard template is described. Transmission electron microscopy (TEM) exhibits the presence of mesoporous structure in our sample and the corresponding wide-angle X-ray diffraction (XRD) pattern confirmed the crystalline wall of sample. N₂ adsorption measurement exhibits the synthesized crystalline mesoporous indium oxide possesses a specific surface area of 39 m²/g and the total pore volume of 0.17 cm³/g, and the corresponding pore size distribution curve reveals the presence of a mesopore of 7.0 nm in maximum. Our work demonstrates that the maintenance of the ordered structure of carbon template is very significant for obtaining high quality replicas via the nanocasting route.     

One-pot synthesis of ordered mesoporous carbon–silica nanocomposites templated by mixed amphiphilic block copolymers

Mixed amphiphilic block copolymers of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO–PPO–PEO) and polydimethylsiloxane-poly(ethylene oxide) (PDMS–PEO) have been successfully used as co-templates to prepare ordered mesoporous polymer–silica and carbon–silica nanocomposites by using phenolic resol polymer as a carbon precursor via the strategy of evaporation-induced self-assembly (EISA). The ordered mesoporous materials of 2-D hexagonal (p6m) mesostructures have been achieved, as confirmed by small-angle X-ray scattering (SAXS), transmission electron microscopy (TEM), and nitrogen-sorption measurements. Experiments show that using PDMS–PEO as co-template can enlarge the pore sizes and reduce the framework shrinkage of the materials without evident effect on the specific surface areas. Ordered mesoporous carbons can then be obtained with large pore sizes of 6.7 nm, pore volumes of 0.52 cm³/g, and high surface areas of 578 m²/g. The mixed micelles formed between the hydrophobic PDMS groups and the PPO chains of the F127 molecules should be responsible for the variation of the pore sizes of the resulting mesoporous materials. Through the study of characteristics of mesoporous carbon and mesoporous silica derived from mother carbon–silica nanocomposites, we think mesoporous carbon–silica nanocomposites with the silica-coating mesostructure can be formed after the pyrolysis of the PDMS–PEO diblock copolymer during surfactant removal process. Such method can be thought as the combination of surfactant removal and silica incorporation into one-step. This simple one-pot route provides a pathway for large-scale convenient synthesis of ordered mesostructured nanocomposite materials.     

Direct template synthesis of mesoporous carbon and its application to supercapacitor electrodes

A direct templating method which is facile, inexpensive and suitable for the large scale production of mesoporous carbon is reported herein. A meso-structure surfactant/silicate template was made in a solution phase and resorcinol-formaldehyde as a carbon precursor was incorporated into the template solution. After aging, carbonization and hydrofluoric acid (HF) etching, mesoporous carbon was obtained. Using X-ray diffraction, scanning and transmission electron microscopy and nitrogen sorption, the synthesis mechanism of the mesoporous carbon was elucidated. According to the small angle X-ray scattering measurements, the surface became smoother after the removal of the silica, indicating that the silica was mostly located at the pore surface of the carbon. Also, the calculation of the pore volume demonstrated that the silica was transferred into the pores of the carbon without structural collapse during HF etching. When the prepared mesoporous carbon was applied to a supercapacitor electrode, the rectangular shape of the cyclic voltammogram was less collapsed, even at a high scan rate, which is indicative of its high rate capability. This was due to the low resistance of the electrolyte in the pores (3.8 Ω cm²), which was smaller than that of conventional activated carbon electrodes and even comparable to that of ordered mesoporous carbon electrodes. This improved performance was probably due to the well developed mesoporosity and high pore connectivity of the prepared mesoporous carbon.     

Synthesis, characterization, and catalytic application of highly ordered mesoporous alumina-carbon nanocomposites

Highly ordered mesoporous carbon-alumina nanocomposites (OMCA) have been synthesized for the first time by a multi-component co-assembly method followed by pyrolysis at high temperatures. In this synthesis, resol phenol-formaldehyde resin (PF resin) and alumina sol were respectively used as the carbon and alumina precursors and triblock copolymer Pluronic F127 as the template. N2-adsorption measurements, X-ray diffraction, and transmission electron microscopy revealed that, with an increase of the alumina content in the nanocomposite from 11 to 48 wt.%, the pore size increased from 2.9 to 5.0 nm while the ordered mesoporous structure was retained. Further increasing the alumina content to 53 wt.% resulted in wormhole-like structures, although the pore size distribution was still narrow. The nanocomposite walls are composed of continuous carbon and amorphous alumina, which allows the ordered mesostructure to be well preserved even after the removal of alumina by HF etching or the removal of carbon by calcination in air. The OMCA nanocomposites exhibited good thermostability below 1000 °C; at higher temperatures the ordered mesostructure partially collapsed, associated with a phase transformation from amorphous alumina into γ-Al₂O₃. OMCA-supported Pt catalysts exhibited excellent performance in the one-pot transformation of cellulose into hexitols thanks to the unique surface properties of the nanocomposite.     

Synthesis of Pt-containing ordered mesoporous carbons and their catalysis for toluene hydrogenation

Highly ordered Pt-containing mesoporous carbons (Pt-OMCs) have been synthesized by a multi-component co-assembly method followed by pyrolysis at high temperature. In this synthesis, resorcinol, formaldehyde and chloroplatinic acid were used as the carbon and Pt precursors. The triblock copolymer Pluronic F127 was used as the template. X-ray diffraction, N₂-adsorption measurements and transmission electron microscopy revealed that the Pt nanoparticles in about 1–3 nm were embedded in the highly ordered mesostructure carbon. The Pt3.1-OMC was used as the catalyst in the hydrogenation of toluene. By comparing with the traditional impregnated 3.3Pt/OMC catalyst to our catalyst, Pt3.1-OMC, the sample exhibited a much higher selectivity to methylcyclohexane.     

Ordered Mesoporous Carbons

Ordered mesoporous carbons have recently been synthesized using ordered mesoporous silica templates. The synthesis procedure involves infiltration of the pores of the template with appropriate carbon precursor, its carbonization, and subsequent template removal. The template needs to exhibit three‐dimensional pore structure in order to be suitable for the ordered mesoporous carbon synthesis, otherwise disordered microporous carbon is formed. MCM‐48, SBA‐1, and SBA‐15 silicas were successfully used to synthesize carbons with cubic or hexagonal frameworks, narrow mesopore size distributions, high nitrogen Brunauer–Emmett–Teller (BET) specific surface areas (up to 1800 m² g^–1), and large pore volumes. Ordered mesoporous carbons are promising in many applications, including adsorption of large molecules, chromatography, and manufacturing of electrochemical double‐layer capacitors.     

Preparation of polyaniline coated activated carbon and their electrode performance for supercapacitor

Polyaniline coated mesoporous and microporous activated carbons were prepared by chemical oxidation polymerization of aniline adsorbed on activated carbons. BET and mesopore specific surface areas of the obtained activated carbons decreased by coating with polyaniline. The electrode performance of the polyaniline coated activated carbons for supercapacitor was investigated. The electrochemical pseudo-capacitances increased with increasing polyaniline content in activated carbons. The capacitances due to polyaniline in the mesoporous activated carbon are much higher than those in the microporous activated carbon. The uniform coating of polyaniline on mesopores of activated carbon plays an important role in pseudo-capacitance due to polyaniline.     

Highly active PtCo nanoparticles on hierarchically ordered mesoporous carbon support for polymer electrolyte membrane fuel cells

Journal of Materials Science - In this work, PtCo nanoparticles (NPs) on hierarchically ordered mesoporous carbon (PtCo/OMC) are synthesized for polymer electrolyte membrane fuel cells (PEMFCs)...