Mesoporous Carbon CMK-3 Research Articles

Highly Stable Pt–Ru Nanoparticles Supported on Three-Dimensional Cubic Ordered Mesoporous Carbon (Pt–Ru/CMK-8) as Promising Electrocatalysts for Methanol Oxidation

The cost of the catalysts used in the direct methanol fuel cell poses a challenge to its widespread use as an energy efficient and environment friendly fuel conversion technology. In this study, two types of highly ordered mesoporous carbon CMK-8 (I and II) with high surface area and 3-D bicontinuous interpenetrating channels were synthesized and deposited with Pt–Ru nanoparticles using the sodium borohydride reduction method. The electrocatalytic capabilities for methanol oxidation were investigated using cyclic voltammetry and chronoamperometry, and the results were compared with that of Pt–Ru deposited on Vulcan XC-72 using the same preparation method as well as with commercial Pt–Ru/C (E-TEK) catalyst. Pt–Ru/CMK-8-I synthesized by the method developed in this work revealed an outstanding specific mass activity (487.9 mA/mg) and superior stability compared with the other supports, thus substantiating its potential to reduce the costs of DMFC catalysts.

Adsorption of Basic Dye in Aqueous Solution by Mesoporous Carbon Materials

Mesoporous carbon CMK-3 with high surface area and opened pore structure was used to adsorb the basic dye, Malachite green (MG). The equilibrium adsorption data was well described by the Langmuir model, and a very high Langmuir adsorption capacity was obtained by this adsorbent. The adsorption kinetics was found to be best represented by a pseudo-second-order kinetic model.

Influence of nitric acid modification of ordered mesoporous carbon materials on their capacitive performances in different aqueous electrolytes

Two kinds of ordered mesoporous carbon (OMC), hexagonal mesoporous carbon CMK-3 and cubic mesoporous carbon CMK-8, are prepared by a hard template nanocasting method. Afterwards, nitric acid modification is conducted to explore the influence of surface functional groups on the supercapacitive characteristics of the OMC electrodes. The electrochemical performances of CMK-3, CMK-8, acid-modified CMK-3 (H-CMK-3) and acid-modified CMK-8 (H-CMK-8) electrodes are investigated in three-electrode cells using alkaline (2M KOH), acidic (2M H2SO4) and neutral (2M Na2SO4) aqueous media. After nitric acid modification, the capacitive performances of two OMCs are improved in KOH, decreased in H2SO4, but showed no change in Na2SO4. The correlations among the change of surface functional groups after acid modification, electrolyte category and the capacitive performance of the OMCs are studied in detail. It can provide a guideline for proper usage of OMC-based materials for the next generation of supercapacitors.

Adsorption of tannic acid and phenol on mesoporous carbon activated by CO2

Ordered mesoporous carbon CMK-3 was synthesized and further activated using CO2 at 1173K for 2h (C1173-2). Batch experiments were conducted to access the adsorption properties of C1173-2 towards aqueous phenol and tannic acid. Nonporous graphite, the pristine CMK-3, and a commercial microporous activated carbon (AC) were also included as comparative adsorbents. The adsorption affinity of C1173-2 for both phenol and tannic acid was much higher than that of CMK-3, resulting from the enhanced specific surface area of C1173-2. After normalizing for adsorbent surface area, phenol adsorption on the three porous carbons was comparable. However, tannic acid adsorption on C1173-2 was similar to that on CMK-3, but prominently higher than that on AC. N2 adsorption results of the porous adsorbents with tannic acid loaded reflected that the pore volume, especially micropore volume of C1173-2 and CMK-3, was effectively utilized by tannic acid, which was different from the poor occupation of pore volumes for AC. Phenol and tannic acid adsorption over C1173-2, CMK-3 and AC followed the pseudo-second order model and the adsorption rate of C1173-2 was the highest. Moreover, adsorption of the two solutes on C1173-2, CMK-3 and AC was affected by external mass transfer and intraparticle diffusion. To our knowledge, it is the first study on the adsorption of aqueous organic contaminants on mesoporous carbon activated by CO2. The findings highlight the significance of CO2 activation method to improve the adsorption properties of ordered mesoporous carbon for aqueous organic contaminants.

Anionic Dye Adsorption on Chemically Modified Ordered Mesoporous Carbons

The surface chemistry of ordered mesoporous carbon CMK-3 was successfully modified by heat treatment in ammonia gas at a temperature of 1173 K, without destroying its hexagonally ordered mesoporous structure significantly. The adsorption kinetics and equilibrium of three commercial anionic dyes, i.e., orange II, reactive red 2 (RR2), and acid black 1(AB1), on the novel functionalized carbon were investigated. It was found that the ammonia-tailored CMK-3 showed a much higher uptake rate than that of a commercial activated carbon, due to its desirable ordered mesoporous structure and the electron-donating effect of the incorporated nitrogen-containing functional groups, particularly for the adsorption of the large molecule dye with a long chain, AB1. The dye initial concentration and adsorption temperature had little influence on the adsorption rate, while the size and spatial structure of dye molecules and the shaking speed played an important role during the adsorption process. The adsorption of AB1 which...

Fabrication of BaTiO3–Carbon Nanocomposite and Porous BaTiO3

A novel nanocomposite was fabricated by introducing BaTiO3 into mesoporous carbon CMK-3 with hexagonal porous structure and pore size around 3.4 nm. Nanosized BaTiO3 crystallites were fully dispersed and confined in the channels of CMK-3. This is the first combination of conventional ferroelectrics with newly developed mesoporous carbon materials. Furthermore, the carbon matrix was thermally removed in oxygen atmosphere to form unique nanoporous structures with the framework of crystalline BaTiO3. The particle morphology evolution from CMK-3 to BaTiO3–CMK-3, and then to porous BaTiO3, was followed by high-resolution scanning electron microscopy (HRSEM). Although this work was aimed at preparation, the present nanocomposite of conductive amorphous carbon and insulate crystalline ferroelectrics, as well as the nanoporous BaTiO3, are expected to have interesting properties in areas such as power storage, microwave adsorbing, and gas sensor.

Selective Heating of Pd-Modified Ordered Mesoporous Carbon CMK-3 by Microwave Irradiation

Abstract Various microwave-heated heterogeneous catalytic reactions can be accelerated by choice of the catalyst supports and solvents. In this work, heterogeneous Pd catalysts supported on ordered mesoporous carbon CMK-3 and related catalysts were prepared. In the presence of these catalysts, the effect of microwave heating on Pd-catalyzed Suzuki–Miyaura coupling as a probe reaction was investigated. The CMK-3 worked efficiently as a “carbon nanoflask” under microwave irradiation, especially in nonpolar solvents such as toluene and o-xylene with a lower ratio of dielectric constant (ε′) to dielectric loss (ε′′) (=tan δ).

Ag Catalyst on Ordered Mesoporous Carbon with High Electro-Oxidation Activity for Formaldehyde

Ag nanoparticles have been fabricated on the surface of CMK-3 mesoporous carbon through an immersion-electrodeposition (IE) technique. Transmission electron microscopy analysis indicated that it was a facile approach to electrochemically prepare nano-sized Ag clusters. Electrochemical experiments showed that Ag nanoproducts were efficient electrocatalysts for anodic oxidation of formaldehyde in alkaline solutions, and as the reduced of the potential value, the electrocatalytic peak current density for the formaldehyde electro-oxidation reaction was increased gradually. Also, the electrocatalytic activity of Ag/CMK-3 nanocatalysts for formaldehyde electro-oxidation is higher than that of Ag/XC-72 nanocatalysts. These findings represented a significant step toward the implementation of individual Ag/CMK-3 nanocatalysts as anodic materials in fuel cells and sensors.

A New Composite Electrode of Li2MnSiO4 Nanoparticles Combined with Mesoporous Carbon CMK-3

Abstract Li2MnSiO4 is prepared by nanocasting using CMK-3 mesoporous carbon, and its electrochemical behavior is explored without removing the CMK-3 template. This preparation provides a new cathode material for large capacity Li secondary batteries, equivalent to two-Li+ charge–discharge processes.

Catalysis and characterization of carbon-supported ruthenium for cellulose hydrolysis

Ru catalyst supported on mesoporous carbon CMK-3 shows high activity and durability for the hydrolysis of cellulose to glucose in hot compressed water at 503 K. The Ru/CMK-3 catalyst also hydrolyzes cellobiose to glucose in water at 393 K. Several physicochemical methods such as XRD, TEM, XPS, H 2-TPR, O 2-titration, and XAFS were used to characterize active Ru species on CMK-3 and to clarify the formation pathway of the active species. From these studies, we conclude that hydrous Ru oxide RuO 2·2H 2O is formed on CMK-3 after H 2-reduction of RuCl 3/CMK-3 at 673 K and subsequent passivation at room temperature, and that the Ru oxide nanoparticles with a mean diameter of 1.1 nm are highly dispersed on CMK-3.

Study on the electrochemical properties of cubic ordered mesoporous carbon for supercapacitors

Highly ordered, three-dimensional (3D) cubic mesoporous carbon CMK-8 is prepared by a facile nanocasting approach using cubic mesoporous silica KIT-6 as starting template. Afterwards, in order to increase the active sites of surface electrochemical reactions and promote the wettability in aqueous electrolyte, a chemical surface modification is carried out on the CMK-8 by nitric acid treatment. Two electrodes are prepared from the CMK-8 and the acid-modified CMK-8 (H-CMK-8) and used as the active materials for supercapacitors. The unique 3D mesoporous network combined with high specific surface area makes the nano-channel surfaces of the CMK-8 carbon favorable for charging the electric double-layer, resulting in that the CMK-8 and the H-CMK-8 electrodes both show well supercapacitive properties. Furthermore, the specific capacitance of the CMK-8 can be further improved by acid treatment, so that the H-CMK-8 exhibits the largest specific capacitance of 246 F g −1 at a current density of 0.625 A g −1 in 2 M KOH electrolyte. Also, the two carbon electrodes both exhibit good cycling stability and lifetime. Therefore, based on the above investigations, such CMK-8 carbon, especially H-CMK-8 carbon can be a potential candidate for supercapacitors.

Adsorption process of methyl orange dye onto mesoporous carbon material–kinetic and thermodynamic studies

The mesoporous carbon CMK-3 adsorbent was prepared, characterized, and used for the removal of anionic methyl orange dye from aqueous solution. Adsorption experiments were carried out as batch studies at different contact time, pH, initial dye concentration, and salt concentration. The dye adsorption equilibrium was rapidly attained after 60min of contact time. Removal of dye in acidic solutions was better than in basic solutions. The adsorption of dye increased with increasing initial dye concentration and salt concentration. The equilibrium data were analyzed by the Langmuir and Freundlich models, which revealed that Langmuir model was more suitable to describe the methyl orange adsorption than Freundlich model. Experimental data were analyzed using pseudo-first-order and pseudo-second-order kinetic models. It was found that kinetics followed a pseudo-second-order equation. Thermodynamic study showed that the adsorption was a spontaneous and exothermic process.

Synthesis of ordered mesoporous silicon oxycarbide monoliths via preceramic polymer nanocasting

Highly ordered mesoporous silicon oxycarbide (SiOC) monoliths have been synthesized using liquid poly(hydridomethylsiloxane) (PHMS) as starting preceramic polymer and mesoporous carbon CMK-3 as direct template. Monolithic SiOC-carbon composites were generated via nanocasting of PHMS into CMK-3, pressing without any additive, cross-linking at 150 °C under humid air and subsequent thermolysis at 1000 or 1200 °C under argon atmosphere. The carbon template was finally removed by the thermal treatment at 1000 °C in an ammonia atmosphere, as a result of the generation of monolithic SiOC ceramics with ordered mesoporous structures. The products were characterized by scanning electron and transmission electron microscopes, X-ray diffraction, Fourier transformation infrared spectrometer, X-ray photoelectron spectroscope and nitrogen absorption–desorption analyzer. The as-prepared SiOC monoliths exhibited crack-free, ordered 2-dimentional hexagonal p6mm symmetry with high specific surface areas. With increasing the calcination temperature, the ordered mesoporous structure was still remained and the specific surface area just had a slight reduction from 616 to 602 m 2 g −1. Moreover, the porous SiOC monoliths possessed good compression strengths and anti-oxidation properties.

Synthesis of recyclable catalyst–sorbent Fe/CMK-3 for dry oxidation of phenol

The magnetic mesoporous material Fe/CMK-3 acting as a catalyst–sorbent was synthesized by using ordered mesoporous carbon CMK-3 as the supporter, Fe(NO 3) 3 as the iron source, and glycol as the reducing agent. The samples synthesized were characterized by powder X-ray diffraction (XRD), N 2 adsorption–desorption, scanning electron microscope (SEM) and transmission electron microscopy (TEM). The results show that the prepared Fe/CMK-3 preserved the ordered mesoporous structure of CMK-3, and magnetic species was mainly Fe 3O 4, which was dispersed inside channels of CMK-3 as nanoparticles with the diameter of around 10 nm. The adsorption and catalytic dry oxidation efficiency of the prepared Fe/CMK-3 were determined. The results also show that Fe/CMK-3 had good adsorption performance of phenol in aqueous solution and could be easily separated from water and recycled due to its ferromagnetic nature. Iron oxides supported on CMK-3 were excellent catalysts for dry oxidation of phenol. After 15 adsorption–catalytic oxidation cycles, the phenol adsorption capacity of Fe/CMK-3 only decreased a little, suggesting the good practicality. Combined thermogravimetry and mass spectrum (TG–MS) instrument was used to investigate the catalytic oxidation of phenol on Fe/CMK-3 and the ignition characteristics of the catalyst–sorbent. The supported Fe 3O 4 was found to be not only the magnetic component but also the active catalyst for the oxidation of phenol. The adsorbed phenol could be oxidized into CO 2 and H 2O at 220 °C at which no obvious phenol desorption or CMK-3 ignition occurred.

Improving the electrocapacitive properties of mesoporous CMK-5 carbon with carbon nanotubes and nitrogen doping

Nitrogen-containing carbon composite materials composed of mesoporous carbon CMK-5 and carbon nanotubes (CNTs) were prepared by the chemical vapor deposition method with Fe(NO 3) 3-impregnated SBA-15 as template and pyridine as the carbon precursor. The Fe nanoparticles confined in the channels of SBA-15 induced the formation of mesoporous carbon characteristic of CMK-5, whereas Fe particles homogeneously dispersed on the external surface of SBA-15 served as catalysts for CNTs growth. The contents of CNTs, the N doping level and the microstruture of the carbon composite were closely related to the initial Fe/Si atomic ratio in SBA-15 template. Incorporation of CNTs in the composite was found to substantially reduce the electric resistance, leading to the composite materials exhibiting excellent rate-performance. A maximum specific capacitance of 208 F/g and a power density of 10 kW/kg were achieved in 6.0 mol/L KOH aqueous electrolyte when these carbon composites were applied as supercapacitor electrodes. Moreover, the composite electrode also exhibited good electrochemical stability with no capacitance loss after 1000 cycles of galvanostatic charge–discharge process.

Taguchi optimization approach for Pb(II) and Hg(II) removal from aqueous solutions using modified mesoporous carbon

Using the Taguchi method, this study presents a systematic optimization approach for removal of lead (Pb) and mercury (Hg) by a nanostructure, zinc oxide-modified mesoporous carbon CMK-3 denoted as Zn-OCMK-3. CMK-3 was synthesized by using SBA-15 and then oxidized by nitric acid. The zinc oxide was loaded to the modified CMK-3 by the equilibrium adsorption of Zn(II) ions from aqueous solution followed by calcination to convert zinc nitrate to zinc oxide. The CMK-3 had porous structure and high specific surface area which can accommodate zinc oxide in a spreading manner, the zinc oxide connects to the carbon surface via oxygen atoms. The controllable factors such as agitation time, initial concentration, temperature, dose and pH of solution have been optimized. Under optimum conditions, the pollutant removal efficiency (PRE) was 97.25% for Pb(II) and 99% for Hg(II). The percentage contribution of each controllable factor was also determined. The initial concentration of pollutant is the most influential factor, and its value of percentage contribution is up to 31% and 43% for Pb and Hg, respectively. Our results show that the Zn-OCMK-3 is an effective nanoadsorbent for lead and mercury pollution remediation. Langmuir and Freundlich adsorption isotherms were used to model the equilibrium adsorption data for Pb(II) and Hg(II).

Carbon Nanocage: Super-Adsorber of Intercalators for DNA Protection

In this research, we report the binding behaviors of two kinds of intercalators, methyl violet and 3,6-diaminoacridine hydrochloride, to various mesoporous materials, carbon nanocage, mesoporous carbon CMK-3, activated carbon, and mesoporous silica SBA-15. Due to its unique cage type structure, carbon nanocage shows greater adsorption capacity than the other adsorbents. In addition, competitive adsorption of methyl violet between DNA and mesoporous materials confirmed that carbon nanocage can very efficiently inhibit intercalation of methyl violet by DNA. Carbon nanocage might then be useful for entrapment of harmful aromatic molecules.

Sorption of uranium(VI) using oxime-grafted ordered mesoporous carbon CMK-5

A new sorbent for uranium(VI) has been developed by functionalizing ordered mesoporous carbon CMK-5 with 4-acetophenone oxime via thermally initiated diazotization. The sorption of U(VI) ions onto the functionalized CMK-5 (Oxime-CMK-5) was investigated as a function of sorbent dosage, pH value, contact time, ionic strength and temperature using batch sorption techniques. The results showed that U(VI) sorption onto Oxime-CMK-5 was strongly dependent on pH, but to a lesser extent, on ionic strength. Kinetic studies revealed that the sorption process achieved equilibrium within 30 min and followed a pseudo-first-order rate equation. The isothermal data correlated with the Langmuir model better than the Freundlich model. Thermodynamic data indicated the spontaneous and endothermic nature of the process. Under current experimental conditions, a maximum U(VI) sorption capacity was found to be 65.18 mg/g. Quantitative recovery of uranium was achieved by desorbing the U(VI)-loaded Oxime-CMK-5 with 1.0 mol/L HCl and no significant decrease in U(VI) sorption capability of Oxime-CMK-5 was observed after five consecutive sorption–desorption cycles. The sorption study performed in a simulated nuclear industry effluent demonstrated that the new sorbent showed a desirable selectivity for U(VI) ions over a range of competing metal ions.

High pressure carbon dioxide adsorption on nanoporous carbons prepared by Zeolite Y templating

Nanoporous carbons were synthesized by chemical vapor deposition using furfuryl alcohol/butylene as a carbon source and zeolite Y as a hard template (ZYC). The ZYC were characterized by PXRD, N2 sorption, and SEM. The carbon materials exhibited predominant microporosity, and the specific surface area increased from 2563 to 3010m2g−1 as the pyrolysis temperature was raised from 800 to 1000°C. ZYC prepared at 1000°C showed a CO2 adsorption capacity of 986mgg−1adsorbent at 40bar 298K, which surpasses the capacities of commercial carbons and mesoporous carbon CMK-3, and closely approaches the best performance of the metal organic framework MOF-177. The CO2 adsorption capacities of the adsorbents were found to be closely correlated with the BET surface areas of the materials tested.

Copper oxide and ordered mesoporous carbon composite with high performance using as anode material for lithium-ion battery

A composite of leaf-shaped copper oxide (CuO) nanoparticles mainly covered on the ordered mesoporous carbon CMK-3 is synthesized by a facile precipitation method. This material (CuO/CMK-3) has been characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and nitrogen sorption. Electrochemical analyses show that the material possesses excellent cycling stability and high rate capability with an average discharge capacity of 171 mAh g −1 at 25 C using as the anode material for lithium-ion battery.