A general synthesis of alkaline mesoporous carbons (AMCs) is developed based on a simplified silica-templating method for room-temperature catalytic oxidation of H2S. The key to the success relies on dissolving the silica templates to create the interconnected mesoporous structure as well as leaving parts of the alkaline products in the pores; both of them are prerequisites for H2S oxidation. By adjusting the alkaline etching degree and organic/inorganic ratio, the porosity and basicity of the AMC could be simultaneously tuned, allowing the AMCs direct use for H2S catalytic oxidation with an unprecedented removal capacities of 4.49 ± 0.12 g/g. Such excellent catalytic performance should be attributed to the developed pore structure that stores the product sulfur and the strong basicity that promotes the dissociation of H2S into HS– ions. Moreover, this simplified silica-templating method could be easily extended to the preparation of various silica templated mesoporous carbon catalysts. All these AMCs demonstrate a successful combination of low cost with high performance, which may well be the answer for the technical development of industrial H2S removal.Keywords: catalytic oxidation; H2S removal; mesoporous carbon; NaOH etching; silica template;

Hierarchical porous carbons with high surface area were prepared by direct carbonization of the polymers which were synthesized via a typical sol–gel method, using terephthalaldehyde and resorcinol as carbon precursors, and metal chloride as reaction assistant. All the metal chlorides could efficiently help to form 3-D porous network carbon with inter-linking irregular particles, and also successfully contribute to the developing of meso-macropores through the packing of grains. Such hierarchical porosity plays an important role for rapid ion diffusion, resulting in an excellent rate capability and low diffusion resistance. Moreover, it should be noted that ZnCl2 could also act as an in situ activation agent during the carbonization process to generate large surface area of 1106 m2 g−1 and pore volume of 1.2 cm3 g−1. In 3 mol L−1 H2SO4, high specific capacitance of 174.6 F g−1 by using the ZnCl2-assisted hierarchical porous carbon as electrode material is obtained and it could retain ca. 84% when the current density increases from 0.1 A g−1 to 20 A g−1. This superior rate capability is higher than that of many hierarchical porous carbons reported in previous literatures. The facile production and excellent electrochemical performance suggested a low cost and effective method to prepare hierarchical porous carbon for energy storage.

KOH activation is a well-accepted approach to develop microporosity for porous carbons, but its severe etching reactions could inevitably destroy the structural integrity and diminish the heteroatomic surface chemistry of the resultant carbons. Herein, we report a method to prepare well-defined micro-spherical, high-surface-area and high-nitrogen-doping carbons via a mild KOH activation. The key to our synthesis relies in the pre-oxidation of the nitrogen-rich polymeric microspheres from resorcinol, formaldehyde and melamine, which could enrich nitrogen heteroatoms into the resultant carbonized framework, resulting in the carbon easily activated by KOH with low surface etching and high residual of nitrogen heteroatoms. The obtained carbons possess high specific surface area of 2234–3121 m2/g, high nitrogen content of 6.1–12.5 wt % and well-preserved spherical morphology. When used as the electrodes of supercapacitor, these carbon microspheres could deliver high specific capacitance up to 309 F/g, excellent rate performance and high cyclic performance of 96% after 5000 cycles in H2SO4 electrolyte. Furthermore, it is found that nitrogen functionalities could contribute considerable pseudo-capacitance, basically through Faradic reactions of the nitrogen.High-surface-area and high-nitrogen-content carbon microspheres were prepared by pre-oxidation, carbonization and mild KOH activation of nitrogen-rich polymeric microspheres.Download high-res image (348KB)Download full-size image

A category of mesoporous carbons-that covers pristine CMK-3, micropore-enriched CMK-3, nitrogen-doped CMK-3 and a combination of nitrogen-doped and micropore- enriched CMK-3 has been prepared via a one-pot wet-impregnation method, using SBA-15 as mesopore template, phenolic resol as carbon precursor, silicate oligomer as micropore template, and nitrogen-rich hexamethoxymethylmelamine as nitrogen precursor. The synthesis is very flexible to control the pore structure and nitrogen doping of the carbons by changing the initial composition of the precursors. The structural similarity of these materials allow them to serve as model systems for mesoporous carbons in general, to comparatively illustrate the enhanced supercapacitor and Li-S cathode properties by nitrogen doping and micropore development. It is found that additional microporosity prevails over the nitrogen doping on the electrostatic adsorption for supercapacitor, while nitrogen doping performs better on the trapping polysulfide species especially at high current rates for Li-S cathode. Simultaneous creation of microporosity and nitrogen doping into mesoporous carbons could combine the synergistic effects, thus greatly improving the electrochemical properties both for supercapacitors and Li-S cathode.

Morphology-controlled Fe3O4/carbon nanocomposites were synthesized by a solvothermal reaction followed by calcination under a nitrogen atmosphere. Flower-like structures, dispersed nanoflakes and hollow microspheres could be readily obtained by adjusting the concentrations of the reactants. Based on the time-dependent structure evolution, a possible mechanism for the formation of the different morphologies under various conditions was discussed. The lithium storage properties of the different Fe3O4/carbon composites were compared. The flower-like sample shows the best electrochemical performance with the highest specific capacity of 227 mAh/g at a current rate of 5 C while hollow microspheres and dispersed nanoflakes have specific capacities of only 45 and 10 mAh/g, respectively.

A new strategy to improve the CO2 capture performance of solid amine sorbents has been developed based on the balance of CO2 kinetic diffusion and thermodynamic sorption. The CO2-neutral surfactant was introduced into polyethyleneimine (PEI) to create extra CO2 transfer pathways, facilitating CO2 diffusion into the deeper PEI films. Consequently, the sorbents offered increased amount of reactive sites and higher utilization efficiency of amine groups, leading to a dramatically enhanced CO2 dynamic capacity and total capacity. Due to the facilitating diffusion, the sorbents could work at room temperature with very good performance. At 30 °C the surfactant-promoted sorbents had the CO2 capture capacity as high as 142 mg g−1 and their amine utilization was over 50%, which are the highest values ever reported for the PEI loaded sorbents working at this temperature. The surfactant-promoted sorbents also exhibited much better sorption kinetics and regeneration performance. In addition to advancing the support or amine, the present study provides another cost-efficient and general approach to design high performance CO2 solid sorbents and may have a major impact on the advance of current carbon capture and storage technologies.

Graphene sheets were prepared via chemical reduction of graphite oxides and then graphitized at 2800 °C. The structure changes from pristine graphite to graphitized graphene sheets were monitored using X-ray diffraction and Raman spectroscopy. It was found that the graphitized graphene sheets exhibited relatively low degree of graphitization and high level of structural defects. XPS spectra revealed that oxygen functionalities could be completely eliminated after graphitization. Morphology observations indicated that graphitization could induce the coalescence and connection of the crumpled graphene agglomerations into compressed grains. The connections included the joint of graphitic sheets along the c-axis with van der Waals force between graphitic sheets and the joint of sheets in the in-plane with covalent bond between carbon atoms. New structures such as the formation of loop at the tip of graphene sheets and the formation of 3D concentric graphene nanoparticles occurred in the graphitized graphene sheets, as a result of self-organization to achieve their lowest potential energy. Our findings should provide some experimental implications for understanding of graphitization behaviour and thermal stability of strictly 2D graphene monolayers.

Partially unzipped carbon nanotubes prepared by strong oxidation and thermal expansion of carbon nanotubes were explored as an advanced catalyst support for PEM fuel cells. The unique hybrid structure of 1D nanotube and 2D double-side graphene resulted in an outstanding electrocatalytic performance.

A flower-like Fe3O4/carbon nanocomposite with nano/micro hierarchical structure is prepared by controlled thermal decomposition of the iron alkoxide precursor, which is obtained via an ethylene glycol-mediated solvothermal reaction of FeCl3 and hexamethylenetetramine (HMT) in the absence of any surfactant. The nanocomposite is characterized by the assembly of porous nanoflakes consisting of Fe3O4 nanoparticles and amorphous carbon that is in situ generated from the organic components of alkoxide precursor. When used as the anode materials for the lithium-ion batteries, the resultant nanocomposite shows high capacity and good cycle stability (1030 m Ah g−1 at a current density of 0.2 C up to 150 cycles), as well as enhanced rate capability. The excellent electrochemical performance can be attributed to the high structural stability and high rate of ionic/electronic conduction arising from the synergetic effect of the unique nano/micro hierarchical structure and conductive carbon coating.Research highlights▶ Fe3O4/carbon micro-flowers are prepared from the iron alkoxide precursor. ▶ Carbon is in situ generated from the organic components of alkoxide precursor. ▶ The composite combines the advantages of hierarchical structure and carbon coating. ▶ Anode material for lithium-ion battery with excellent electrochemical performance.

Carbide derived carbon/xerogel nanocomposites were prepared by chlorine etching titanium carbide xerogel which was synthesized via sol–gel technique using titanium isopropoxide as titanium source and sucrose as carbon precursor, followed by carbothermal reduction process. As-prepared nanocomposites possessed not only three-dimensional network inherited from titanium carbide xerogel but uniform micropores derived from TiC parent. The superior rate capability in organic electrolyte was found with capacitance retention ratio of 85% at 10 Ag−1 as compared to that of conventional carbide derived carbon. Such results could be associated with the advantageous architectures of nanocomposites, which were preferred in decreasing ion transfer resistance, shortening diffusion distance as well as improving electron conductivity.

Ultrahigh-pore-volume carbon aerogels were synthesized by adding rigid silica nanoparticles to resorcinol-formaldehyde sols, followed by supercritical drying, pyrolysis and HF leaching. The presence of silica nanoparticles in polymer gels dramatically inhibits volume shrinkage and framework collapse during the supercritical drying and pyrolysis processes, resulting in the obtained carbon aerogels exhibiting very low bulk density and high pore volume. By changing the mass ratio of silica nanoparticles/resorcinol-formaldehyde resin, pore volumes of carbon aerogels can be tuned in the range of 2.8–6.0 cm3/g.

Graphene nanosheets were synthesized using graphite oxide as a precursor by detonation. The composition, and structure of graphene nanosheets were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning and transmission electron microscopy, selected area electron diffraction, and Raman spectroscopy. Results indicated that the as-prepared material was transparent and wrinkled, and comprised 2-5 graphenes with a highly crystalline structure. The exfoliation and reduction of graphite oxide to graphene nanosheets was induced by the self-generated thermal energy and shockwave of detonation.

Na2CO3-impregnated activated carbon fibers (ACFs) have been developed as low-concentration H2S oxidation catalysts at ambient temperature. Two series of commercial pitch-based and poly(acrylonitrile)-based ACFs were used to evaluate the role of pore structure in the oxidation of H2S. The initial, impregnated, and exhausted materials were characterized using elemental analysis, N2 adsorption, scanning electron microscopy (SEM), thermogravimetry analysis, and activity tests. The catalytic oxidation of H2S continued until all effective pores of the catalysts were blocked by the oxidation products. The saturation sulfur capacity was found to be in the range of 0.10−0.81 g of H2S/g of catalyst, with the value strongly dependent on the pore structure (especially the volume of pores larger than 0.7 nm) but independent of the nitrogen functional groups. Further quantitative analysis suggested that elemental sulfur as a dominant product mostly deposited in large pores (d > 0.7 nm), whereas sulfuric acid was preferably produced in small micropores (d < 0.7 nm). A possible mechanism of H2S oxidation with respect to the pore size of catalysts is proposed.

Anthracite was activated by NaOH to prepare high-performance activated carbons as electrodes for electric double-layer capacitors. The porous structure and electrochemical characteristics of the carbons were investigated by nitrogen sorption and electrochemical methods. The effect of pore structure on the electrochemical performance of the carbons in a 1 mol/L (C2H5)4NBF4/propylene carbonate (PC) electrolyte was investigated. The as-prepared activated carbons exhibit large surface areas (943-2479 m2/g) and high-specific capacitances (57–167 F/g). The specific capacitance depends not only on the surface area, but also on the pore size distribution (PSD) of the carbon. Pores with a size of 2–3 nm are crucial for the ions to penetrate inside them for the (C2H5)4NBF4/PC electrolyte. Specific capacitance is higher and impedance is lower for the sample with a wider PSD due to the fact that electrolyte ions could easily enter the pores.

Impregnated mesoporous carbon aerogels serve as novel catalysts for the first time with respect to low-temperature oxidation of H2S to elemental sulfur, and exhibit particularly high activity (up to 3 g sulfur per gram of catalyst) and high selectivity.

Ultrafine SnO2-containing nanocomposites were synthesized from glucose/SnCl2 acid solution under hydrothermal environment. The content of SnO2 in the nanocomposites could be adjusted by changing the mass ratio of SnCl2 to glucose in the initial solution. The crystalline structure and morphology of the as-synthesized nanocomposites have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM). The results revealed that the nanocomposites were composed of highly dispersing SnO2 nanoparticles with the sizes of only a few nanometers (3–5 nm). Electrochemical tests demonstrated that the electrochemical performances were strongly dependent on the content of SnO2 in the nanocomposites. The nanocomposites containing 75 wt.% SnO2 exhibited an outstanding reversible capacity of 610 mAh/g and high capacity retention after 200 cycles. The extraordinary performance should originate from the very small size of SnO2 nanoparticles and carbon precursor matrix derived from glucose which can confer the ability to accommodate the volume changes and prevent the agglomeration of Sn particles during charge/discharge process.

Spherical carbon aerogels (SCAs) with controlled particle size and mesopore size were synthesized by an emulsified sol–gel polymerization of phenol, melamine and formaldehyde. The adsorption rate and capacity of biomolecules with different molecular dimensions, including l-phenylalanine (Phe), vitamin B12 (VB), α  -chymotrypsin (Chy) and bovine serum albumin (BSA) onto SCAs were investigated. The mesopore size can be easily tuned in the range from 5 to 10 nm by simply adjusting catalyst concentration in the initial solution and the spherical particle size can be controlled in 50–500 μm by changing stirring speed. The as-prepared SCAs have high specific surface area (>600 m2/g>600 m2/g) and large pore volume (>1 cm3/g>1 cm3/g). The hardness of SCAs is ca. 10 times as large as that of commercial spherical activated carbon particles. The adsorption rate of VB is strongly depended on the mesopore size and particle size, and show an increasing tread with the increase of mesopore size and the decrease of particle size. For small molecule Phe, the specific surface area is key factor to determine the adsorption capacity, but the adsorption capacity of large molecules (VB, Chy and BSA) is dependent on the pore size of SCAs, which should be suitably larger than the molecule size of biomolecules.Spherical carbon aerogels with controlled particle size and mesopore size were used as hosts for selective adsorption biomolecules with different molecular dimensions.

Mesoporous carbons were synthesized by organic–organic self-assembly of triblock copolymer F127 and resorcinol–furfural oligomers. The effects of the mass ratio of F127 to oligomers (F127/RF), reaction time of resorcinol with furfural and furfural/resorcinol ratio (F/R) on pore architecture and phase purity of mesoporous carbons were investigated. Resorcinol–furfural oligomers prefer to mix with hydrophilic poly(ethylene oxide) (PEO) blocks rather than with hydrophobic poly(propylene oxide) (PPO) blocks, and thereby cause a swelling of the hydrophilic volume and force the hydrophilic/hydrophobic interface toward low interfacial curvature. As a result, mesostructures including disordered, 3D body-centered cubic (Im3m), 2D hexagonal (p6m), wormlike and mesocellular structures were obtained by increasing the mass ratio of F127/RF. The physiochemical properties of oligomers would determine the quality of interactions between F127 and oligomers, which can affect swelling extent of PEO blocks and the resultant mesostructures. At the same F127/RF ratio, a mesostructure transition from Im3m to p6m to disorder was observed as the degree of polymerization of oligomers increased. This transition is attributed to the decreased thermodynamic driving force for oligomers to mix with PEO blocks. Decreasing F/R ratio could improve the hydrophilic properties of oligomers, which is favor for forming highly ordered mesostructures.

Organic and carbon aerogels were prepared by sol–gel polymerization of phenol, melamine and formaldehyde, followed by supercritical drying and pyrolysis. The effect of the mole ratio of melamine/phenol (M/P) on microstructure of organic and carbon aerogels was investigated by N2 adsorption, SEM and TEM. Coordination M/P could change the hydrophilicity and cross-linking density of polymer framework, thereby affecting polymer colloid nanoparticle nucleation and growth, and ultimately determine the 3-dimensional network of the gels. The bulk densities of organic and carbon aerogels have maxima at M/P of 0.1, which are inversely proportional to volume shrinkage of gels during drying and pyrolysis. The size of the nanoparticles could be adjusted by varying M/P in the range from 10 to 22 nm. The mesopore volumes of organic and carbon aerogels are tailored in the range of 1.4–2.9 and 0.8–2.5 cm3/g, respectively. The average mesopore diameter has experienced a decreasing first and increasing afterward tendency with the increase of M/P, and exhibit a minimum at M/P of 0.1.

Mesoporous titanium carbides were prepared via carbothermal reduction of organic–inorganic gels using titanium n-butoxide as a Ti source and sucrose as a carbon precursor. The as-made titanium carbides were used as starting materials for producing carbide-derived carbons (CDCs) through thermochemical treatment in a chlorine environment. The influence of the ratio of titanium n-butoxide to sucrose (R) on the porous structure and physical properties of the mesoporous titanium carbide and the resulting CDCs were investigated using X-ray diffraction, Raman spectroscopy, scanning and transmission electron microscopy, and N2 adsorption. It was found that mesoporosity and macroporosity developed in the course of the formation of the titanium carbides can be preserved and transmitted to the carbon material after chlorine treatment, while microporosity was formed by extraction titanium atoms from the carbide. The obtained CDCs have a hierarchical structure of multiscaled pores, including uniform micropores produced from carbides, mesopores with diameter of 3-4 nm original from the residual free carbon and macropores formed by interconnection and overlapping of the carbon particles. By changing the R, the Brunauer–Emmett–Teller specific surface areas and total pore volumes of the CDCs could be adjusted in the range of 1479-1 640 m2/g and 1.06-2.03 cm3/g, respectively. These hierarchical porous carbons would have potential applications for use in catalysis, adsorption, gas separation, and electrochemical energy storage.

Chemical states of nitrogen in the carbon aerogels synthesized from phenol-melamine-formaldehyde were investigated by elemental analysis, X-ray photoelectron spectroscopy and nitrogen adsorption. It is found that the carbon aerogels are rich in mesopores and the nitrogen content of the carbon aerogels increases from 1.6 to 3.1 wt. % with increasing melamine to phenol ratios. Over two-thirds of nitrogen are on periphery of graphene layers (pyridinic-N, pyrrolic-N and/or pyridonic-N, pyridine N-oxide) and less than one-third in central position of graphene layers (quaternary-N). Polymerisation at low pH might cause a preferred location of nitrogen on periphery of graphene layer.

Oxygen-rich activated carbons (OAC) were prepared from bituminous coal through a quick KOH activation. OAC exhibited a moderately large surface area of 1950 m2/g, a relative wide pore size distribution, good conductivity and very high oxygen content (up to 12 wt.%). Compared with high surface area activated carbons prepared by the conventional KOH activation, OAC have superior capacitive behavior, power output and high energy density in electrochemical double layer capacitors (EDLC). OAC presented a high specific capacitance of 370 F/g in 3 M KOH electrolyte at a low current density of 50 mA/g and still remained 270 F/g even at a high current density of 20 A/g.

Impregnated mesoporous carbon aerogels serve as novel catalysts for the first time with respect to low-temperature oxidation of H2S to elemental sulfur, and exhibit particularly high activity (up to 3 g sulfur per gram of catalyst) and high selectivity.

Partially unzipped carbon nanotubes prepared by strong oxidation and thermal expansion of carbon nanotubes were explored as an advanced catalyst support for PEM fuel cells. The unique hybrid structure of 1D nanotube and 2D double-side graphene resulted in an outstanding electrocatalytic performance.