Mesoporous Carbon Framework Research Articles

Preparation of ordered mesoporous carbon nanopipes with controlled nitrogen species for application in electrical double-layer capacitors

Nitrogen-doped mesoporous carbon nanopipes with various nitrogen states are prepared by controlling the carbonization temperature. Nitrogen adsorption–desorption and transmission electron microscopy (TEM) analyses reveal that the optimum carbonization temperature is 1123 K. A carbonization temperature below 1073 K is insufficient to form a mesoporous carbon framework, while collapse of the carbon structure is observed above 1173 K. X-ray photoelectron spectroscopy measurements clearly show that nitrogen species are chemically transformed into pyrrolic and quaternary state species with higher binding energies. In cyclic voltammetry measurements, polar species of quaternary nitrogen on a carbon surface show a positive effect to enhance the capacitance via an increase in hydrophilicity and wettability of carbon by the electrolyte.

A highly ordered nanostructured carbon–sulphur cathode for lithium–sulphur batteries

The Li-S battery has been under intense scrutiny for over two decades, as it offers the possibility of high gravimetric capacities and theoretical energy densities ranging up to a factor of five beyond conventional Li-ion systems. Herein, we report the feasibility to approach such capacities by creating highly ordered interwoven composites. The conductive mesoporous carbon framework precisely constrains sulphur nanofiller growth within its channels and generates essential electrical contact to the insulating sulphur. The structure provides access to Li+ ingress/egress for reactivity with the sulphur, and we speculate that the kinetic inhibition to diffusion within the framework and the sorption properties of the carbon aid in trapping the polysulphides formed during redox. Polymer modification of the carbon surface further provides a chemical gradient that retards diffusion of these large anions out of the electrode, thus facilitating more complete reaction. Reversible capacities up to 1,320 mA h g(-1) are attained. The assembly process is simple and broadly applicable, conceptually providing new opportunities for materials scientists for tailored design that can be extended to many different electrode materials.

Lithium‐Catalyzed Dehydrogenation of Ammonia Borane within Mesoporous Carbon Framework for Chemical Hydrogen Storage

AbstractAmmonia borane (AB) has attracted tremendous interest for on‐board hydrogen storage due to its low molecular weight and high gravimetric hydrogen capacity below a moderate temperature. However, the slow kinetics, irreversibility, and formation of volatile materials (trace borazine and ammonia) limit its practical application. In this paper, a new catalytic strategy involved lithium (Li) catalysis and nanostructure confinement in mesoporous carbon (CMK‐3) for the thermal decomposition of AB is developed. AB loaded on the 5% Li/CMK‐3 framework releases ∼7 wt % of hydrogen at a very low temperature (around 60 °C) and entirely suppresses borazine and ammonia emissions that are harmful for proton exchange membrane fuel cells. The possible mechanism for enhanced hydrogen release via catalyzed thermal decomposition of AB is discussed.

Highly dispersed platinum supported on nitrogen-containing ordered mesoporous carbon for methanol electrochemical oxidation

Nitrogen-containing ordered mesoporous carbons (NOMCs) characteristic of CMK-3 were nanocasted from mesoporous silica SBA-15 using aniline as carbon precursor. The influence of synthesis condition on the structural parameters of NOMCs were systematically investigated using N 2 adsorption, powder X-ray diffraction (XRD), transmission electron microscopy, X-ray photoelectron spectroscopy (XPS), elemental analysis and thermogravimetric analysis (TGA). The 2D hexagonally ordered nitrogen-containing mesoporous carbon could be synthesized in a wide temperature range (600–950 °C), with Brunauer–Emmett–Teller (BET) surface area varying from 988 to 1166 m 2/g and pore size tunable from 2.7 to 3.3 nm. The N/C molar ratio in the framework of mesoporous carbon was found to be highly dependent on the synthesis condition and reduced from 9.5% to 4.8% as the synthesis temperature increased from 600 to 950 °C. XPS showed that nitrogen atoms were incorporated in graphitic sheets as quaternary nitrogen and pyridine-like nitrogen. The ca. 0.6 eV lower binding energy of Pt nanoparticles in contrast to that of bulk Pt indicated a strong interaction between nitrogen atoms and Pt nanoparticles, which was critical to the uniform dispersion of Pt nanoparticles on the nitrogen-containing mesoporous carbon. The CO stripping peak potentials depended on both the N/C ratio as well as Pt particles size. The activities of methanol oxidation on Pt/NOMCs were investigated by cyclic voltammograms and electrochemical impedance spectroscopy (EIS). The Pt/NOMCs showed generally high CO tolerance and comparable activity to Pt/XC-72 under the identical condition.

Synthesis, characterization, and electrochemical properties of ordered mesoporous carbons containing nickel oxide nanoparticles using sucrose and nickel acetate in a silica template

New ordered mesoporous carbons containing nickel oxide nanoparticles have been successfully synthesized by carbonization of sucrose in the presence of nickel acetate inside SBA-15 mesoporous silica template. The obtained samples were characterized by X-ray diffraction (XRD), nitrogen adsorption–desorption, and transmission electron microscopy (TEM). The NiO nanoparticles were embedded inside the mesoporous carbon framework due to the simultaneous pyrolysis of nickel acetate during carbonization. The electrochemical testing of the as-made nanocomposites showed a large specific capacitance of 230 F g −1 using 2 M KOH as the electrolyte at room temperature. This is attributed to the nanometer-sized NiO formed inside mesoporous carbons and the high surface area of the mesopores in which the NiO nanoparticles are formed. Furthermore, the synthetic process is proposed as a simple and general method for the preparation of new functionalized mesoporous carbon materials, for various applications in catalysis, sensor or advanced electrode material.

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.

A Family of Highly Ordered Mesoporous Polymer Resin and Carbon Structures from Organic−Organic Self-Assembly

The syntheses of a family of highly ordered mesoporous polymers and carbon frameworks from organic−organic assembly of triblock copolymers with soluble, low-molecular-weight phenolic resin precursors (resols) by an evaporation induced self-assembly strategy have been reported in detail. The family members include two-dimensional hexagonal (space group, p6m), three-dimensional bicontinuous (Ia3d), body-centered cubic (Im3m), and lamellar mesostructures, which are controlled by simply adjusting the ratio of phenol/template or poly(ethylene oxide)/poly(propylene oxide) in the templates. A five-step mechanism from organic−organic assembly has been demonstrated. Cubic FDU-14 with a gyroidal mesostructure of polymer resin or carbon has been synthesized for the first time by using the copolymer Pluronic P123 as a template in a relatively narrow range. Upon calcination at 350 °C, the templates should be removed to obtain mesoporous polymers, and further heating at above a critical temperature of 600 °C transfor...

Ordered Mesoporous Polymers and Homologous Carbon Frameworks: Amphiphilic Surfactant Templating and Direct Transformation

Ultrahigh stability (>1400 °C) is found for the highly ordered mesoporous polymers and carbon frameworks synthesized from polymerization of phenol and formaldehyde around triblock copolymer templates. Calcination and carbonization lead to removal of the templates and formation of hexagonal and cubic carbon mesostructures with large uniform pores and surface areas (see schematic diagram).

A Facile Aqueous Route to Synthesize Highly Ordered Mesoporous Polymers and Carbon Frameworks with Ia3̄d Bicontinuous Cubic Structure

By employing an organic-organic self-assembly in a dilute aqueous solution, novel ordered bicontinuous cubic mesoporous polymers and carbons with Iad symmetry are directly synthesized.