Micro-mesoporous Carbon Research Articles

Employing MnO as multifunctional polysulfide reservoirs for enhanced-performance Li-S batteries

The lithium sulfur (Li-S) batteries are greatly fascinating as the next-generation storage devices owing to their high theoretical energy density and low cost. However, the fast capacity decay resulting from the “shuttle effect” of polysulfide ions and the irregular deposition of the discharge products (Li2S/Li2S2) severely hinder their commercial application. Herein, micro-mesoporous carbon–MnO (MnO/MPC) composites were synthesized with wet impregnation method and applied as the cathode material. In Li-S cells, the MnO/MPC@S cathode showed a rather better cycling stability over 150 cycles than a MPC@S cathode (sulfur loading ∼74%). The influences of the MnO amount and the heat treatment temperature were investigated and optimized. The 10%-MnO/MPC@S cathode material calcined at 600 °C showed excellent rate capability and cycling stability. Owing to the polar MnO nanoparticles, the soluble lithium polysulfides (Li2Sn, 2 < n ≤ 8) can be effectively adsorbed on the host material and the depositing of Li2S and Li2S2 could also be regulated and controlled. Furthermore, compared with the pristine MPC material, the existence of MnO nanoparticle can effectively enhance the reaction kinetics, which could be ascribed to the plenty of polar sites on the surface of MPC material and the electrocatalytic activity of MnO.

Efficient capture of CO2 over ordered micro-mesoporous hybrid carbon nanosphere

Four kinds of carbon-based adsorbents (micro-mesoporous hybrid carbon nanosphere and N-doped hollow carbon sphere with single-, double- or ruga-shell morphology) with different structural and textural properties were prepared and systematically studied in CO2 capture. All synthesized samples possess high specific surface area (828–910 m2 g−1), large pore volume (0.71–1.81 cm3 g−1), and different micropore contents varied from 2.1% to 46.4%. Amongst, the ordered micro-mesoporous carbon nanosphere (OM-CNS) exhibits the best adsorption performance with CO2 uptake as high as 3.01 mmol g−1 under conditions of 298 K and 1.0 bar, better than most of the reported CO2 adsorbents. The excellent CO2 adsorption capacity of OM-CNS can be reasonably attributed to the synergistic effect of ordered mesopore channels and abundant structural micropores which are beneficial for the diffusion and trapping of CO2 adsorbate. Moreover, the OM-CNS shows excellent CO2 trapping selectivity and superior stability and recyclability, which endow the OM-CNS as a promising and environmental-friendly adsorbent for CO2 capture and separation under practical conditions.

KOH activation of biomass-derived nitrogen-doped carbons for supercapacitor and electrocatalytic oxygen reduction

Nitrogen-doped porous carbon has aroused extensive interests owing to its unique physical and chemical properties. However, the complicated nitrogen-doping method and high cost limit its practical application. In this work, the nitrogen-rich biomass soybean was used as a single precursor for both carbon and nitrogen source to prepare nitrogen-doped hierarchical micro-mesoporous carbon via templating carbonization coupling with subsequent KOH activation. The influence of KOH dosage on the morphology, structure and electrochemical performance (supercapacitor and oxygen reduction reaction (ORR)) was studied in detail. The optimized ANPC-3, synthesized under the KOH/carbon mass ratio of 3/1, possesses high specific surface area of 1749 m2 g−1, developed hierarchical micro-mesoporous structures as well as moderate nitrogen content (1.37 at.%). ANPC-3 exhibits a large energy density of 12.5 Wh kg−1 at a power density of 450 W kg−1 with excellent charge-discharge cyclic stability of 96.5% capacitance remaining after 5000 cycles. As an ORR electrocatalyst, it shows improved ORR activity as well as much better stability and methanol-tolerance capacity than commercial Pt/C catalyst. The unique hierarchical micro-mesoporous textures, high surface area and moderate N-doping level make biomass-derived ANPC-3 become an excellent electrode material in various applications.

Identify the Removable Substructure in Carbon Activation

Activated carbon plays a pivotal role in achieving critical functions, such as separation, catalysis, and energy storage. A remaining question of carbon activation is which substructures in amorphous carbon are preferentially removed during activation. Herein, we report the first structure–activation correlation elucidated on the basis of unprecedented comprehensive characterization on carbon activation. We discover that activation under CO2 preferentially removes graphenic layers that are more defective. Therefore, the resulting activated carbon contains thinned turbostratic nanodomains that are of a higher local graphenic order. The mechanistic insights explain why more defective soft carbon is “burned” under CO2 at a much faster rate than hard carbon. The mechanism leads to an activation-based design principle of mesoporous carbon. Guided by this principle, a bimodal micromesoporous carbon is prepared simply by CO2 activation. Our findings may cause a paradigm shift for the rational design of nanoporou...

Bacterial-cellulose-derived interconnected meso-microporous carbon nanofiber networks as binder-free electrodes for high-performance supercapacitors

Abstract Bacterial cellulose (BC), a typical biomass prepared from the microbial fermentation process, has been proved that it can be an ideal platform for design of three-dimensional (3D) multifunctional nanomaterials in energy storage and conversion field. Here we developed a simple and general silica-assisted strategy for fabrication of interconnected 3D meso-microporous carbon nanofiber networks by confine nanospace pyrolysis of sustainable BC, which can be used as binder-free electrodes for high-performance supercapacitors. The synthesized carbon nanofibers exhibited the features of interconnected 3D networks architecture, large surface area (624 m2 g−1), mesopores-dominated hierarchical porosity, and high graphitization degree. The as-prepared electrode (CN-BC) displayed a maximum specific capacitance of 302 F g−1 at a current density of 0.5 A g−1, high-rate capability and good cyclicity in 6 M KOH electrolyte. This work, together with cost-effective preparation strategy to make high-value utilization of cheap biomass, should have significant implications in the green and mass-producible energy storage.

Adsorption of methylene blue and malachite green on micro-mesoporous carbon materials

The aim of this work was to investigate the determination of adsorption kinetics and adsorption isotherms for methylene blue (MB) and malachite green (MG) from aqueous solutions, on micro-mesoporou...

Graphitic Nanocarbon–Selenium Cathode with Favorable Rate Capability for Li–Se Batteries

A well-organized selenium/carbon nanosheets nanocomposite(Se/CNSs) is prepared by confining chain-like Sen molecules in hierarchically micromesoporous carbon nanosheets. A unique two-dimensional morphology and high graphitization degree of carbon nanosheets benefits fast Li+/e- access to the active Se, which guarantees a high utilization of Se during the(de)lithiation process. Besides, the chain-like Se molecules confined in the carbon matrix could alleviate the shuttle effect of polyselenides and promise a stable electrochemistry. Therefore, the resultant Se/CNSs delivers a highly reversible capacity, a long cycle life and favorable rate capabilities. Furthermore, a Li-Se pouch cell built from a metallic Li anode and the as-prepared Se/CNSs cathode exhibits an excellent electrochemical performance, demonstrating the potential of Se/CNSs in serving future energy storage devices with high energy density.

海带基微孔/介孔复合多级孔纳米炭的制备及电化学性能研究

以新鲜海带为前驱体，通过清洗、酸化和高温炭化过程制备了微孔/介孔复合多级孔炭纳米材料。采用SEM，TEM，N2吸脱附，Raman光谱和电化学测试对其结构和电化学性能进行了表征，结果表明海带基多孔炭性能好于商业活性炭，800℃焙烧获得的多孔炭材料具有最大的比表面积(1703.97 m2/g)和最佳的电化学性能，其在4 M的KOH电解液中，5 A/g电流密度下比电容高达200 F/g，并表现出极佳的循环稳定性。这可归因于高的比表面积和独特的微/介孔复合孔结构。 The fresh seaweed is used as a natural precursor to prepare micro-mesoporous nano-carbon materials. The micro-mesoporous carbon was synthesized by washing, acidification and carbonization at different temperatures. The synthesized hierarchical micro-mesoporous carbon was characterized by SEM, TEM, BET, Raman and electrochemical measurement techniques. The results confirmed that such micro-mesoporous carbon possessed higher electrochemical capacitance than commercial active carbon. The porous carbons activated at 800˚C present high surface area (up to 1703.97 m2/g) and high specific capacitance of 200 F/g at a current density of 5 A/g, and superior cycling stability in a 4 M KOH aqueous solution. The good capacitive performance can be ascribed to the high specific surface area and well-controlled micro- and mesoporosity.

Micro-Mesoporous Carbon Materials from Carbonized Rice Husk as Active Components of Supercondenser Electrodes

Activated carbon materials (CM) were prepared from rice husk carbonized in a fluidized bed reactor. Low temperature nitrogen adsorption at 77 K was used for characterizing the EM texture. Variations in the preparation conditions (carbonization followed by activation) allowed the materials to be synthesized with the BET surface area from 440 to 2290 m 2 /g. Application of potassium or sodium carbonates as activating agents led to the formation of CM with the BET surface area up to 1200 m 2 /g. CM with a larger surface area – up to 2290 m 2 /g – were obtained upon activation with sodium hydroxides. Electrochemical properties and capacitive characteristics were studied using voltammetry and chronopotentiometry in the galvanostatic mode in aqueous 1M H 2 SO 4 electrolyte and ionic liquid BMIMBF 4 . At low charging/discharging rates (0.2 A/g), a linear dependence of bulk capacity on the specific surface area of CM but not on the electrolyte nature was shown. At high charging/discharging rates (2 A/g), negligible or considerable decrease in the specific capacity was observed in 1M H 2 SO 4 and in the ionic liquid, respectively. These observations were accounted for by the influence of the porous structure.

The Electrochemical Behavior of 1-Ethyl-3-Methyl Imidazolium Tetracyanoborate Visualized by In Situ X-ray Photoelectron Spectroscopy at the Negatively and Positively Polarized Micro-Mesoporous Carbon Electrode

The electrochemical properties of the C(Mo2C) | EMImB(CN)4 system have been analyzed using cyclic voltammetry, in situ X-ray photoelectron spectroscopy and electrochemical impedance spectroscopy techniques. The cyclic voltammetry and electrochemical impedance measurements indicated that the tetracyanoborate anions started to electrooxidize and electropolymerize at E = 2.12 V (vs. Ag/AgCl in EMImBF4). However, despite of the formation of compact dielectric polymer layer at the micro-mesoporous C(Mo2C) electrode surface very slow electrochemical polymerization of tetracyanoborate anions continued further at E > 2.12 V leading to the blocking of the C(Mo2C) electrode porous structure and to the reduction of the electrochemically active surface area necessary for the construction of the high energy density supercapacitors. Thus, the tetracyanoborate anion based ionic liquids can be used as the electrolytes for the initial formation of the passivating solid-electrolyte interface for the very wide cell potential supercapacitor positive electrodes, as an electrolyte additives for the solid-electrolyte interface formation or for the correction of the solid-electrolyte interface damages.

Designing micro- and mesoporous carbon networks by chemical activation of organic resins

Carbon xerogels with ultrahigh micro- and mesopore volumes were synthesized from the activation of polymeric resins prepared by sol–gel polycondensation of resorcinol/formaldehyde mixtures in basic medium and subcritical drying. Various activating conditions (e.g., agent, temperature, impregnation conditions) were used and it was found that the textural features of the resulting carbon xerogels are linked to the experimental procedure of the activation reaction to promote the porosity development. The shrinkage and structural collapse of the fragile resins typically obtained upon annealing at high temperatures (during carbonization and/or physical activation) is suppressed when the impregnation of the chemical activating agent is performed under controlled conditions. If the alkaline reagent (either KOH or K2CO3) is put in contact with the resin by wet impregnation (liquid/solid); under such conditions, the intimate contact between both compounds allows the formation of microporosity during the activation along with the enlargement and/or preservation of the mesoporosity of the pristine resin. Furthermore, the chemical activation via wet impregnation allows the combination of high surface areas and the preservation (even higher development) of the mesoporosity created during the synthesis of the resin. The effect of the impregnation method was found highly dependent of the reagent and activation temperature, highlighting the possibility to design micro-mesoporous carbon xerogels at low temperatures with a subtle control of the activation conditions.

High performance anode of lithium-ion batteries derived from an advanced carbonaceous porous network

Constructing sufficient micropores and small mesopores for Li+ storage while maintaining a developed hierarchical macro/mesoporous structure for rapid mass transfer are critical for porous carbons in lithium-ion battery (LIB) applications. Herein, a new kind of hierarchical macro–meso–microporous carbon with high surface area (HSHPC) for LIB application is successfully fabricated by using a porous network structured polymer as a precursor. The as-prepared HSHPC presents a 3D continuous macro/mesopore structure and ultrahigh surface area of 2602 m2 g−1. As a result, it exhibits a high specific capacity of 660 mAh g−1 and stable cycling performance during 100 cycles at a current density of 0.1 A g−1. Furthermore, the ideal macro/mesoporous network is able to guarantee rapid ion diffusion and transfer, thus attaining an excellent high-rate performance in contrast to graphite.

Novel in situ multiharmonic EQCM-D approach to characterize complex carbon pore architectures for capacitive deionization of brackish water

Multiharmonic analysis by electrochemical quartz-crystal microbalance with dissipation monitoring (EQCM-D) is introduced as an excellent tool for quantitative studying electrosorption of ions from aqueous solution in mesoporous (BP-880) or mixed micro-mesoporous (BP-2000) carbon electrodes. Finding the optimal conditions for gravimetric analysis of the ionic content in the charged carbon electrodes, we propose a novel approach to modeling the charge-dependent gravimetric characteristics by incorporation of Gouy-Chapman-Stern electric double layer model for ions electrosorption into meso- and micro-mesoporous carbon electrodes. All three parameters of the gravimetric equation evaluated by fitting it to the experimental mass changes curves were validated using supplementary nitrogen gas sorption analysis and complementing atomic force microscopy. Important overlap between gravimetric EQCM-D analysis of the ionic content of porous carbon electrodes and the classical capacitive deionization models has been established. The necessity and usefulness of non-gravimetric EQCM-D characterizations of complex carbon architectures, providing insight into their unique viscoelastic behavior and porous structure changes, have been discussed in detail.

Nitrogen-doped porous “green carbon” derived from shrimp shell: Combined effects of pore sizes and nitrogen doping on the performance of lithium sulfur battery

Nitrogen-rich porous “green carbons” derived from abundant shrimp shell shows good performance for Li–S batteries. The strategy in this work is highlighted to selective removal of intrinsic CaCO3 in shrimp shell followed by KOH activation to tune the pore sizes of the obtained carbons. On the basis of the different porous structures, the discharge capacity of the obtained carbons as Li–S cathodes follows the order of micro-mesoporous carbon>mesoporous carbon>microporous carbon. The high capacity of the micro-mesoporous carbon is attributed to its positive characters such as the coexistence of micro-mesoporous structure, the large pore volume and the high specific surface area. Furthermore, well-dispersed nitrogen in the porous carbons is naturally doped and inherited from shrimp shell, and can help to enhance cycle stability when used as cathodes. As a result, all carbon cathodes exhibit the good cycle stability (>78%) due to their nitrogen doping induced chemical adsorption of sulfur on the surface areas of the porous carbons. Among them, mesoporous carbon cathode shows the best cycle stability with 90% retention within 100 cycles, which is mainly attributed to the synergistic effects of its both large pore size (5.12 nm) and high nitrogen content (6.67 wt %).

Synthesis of Nitrogen-Doped Micro-Mesoporous Carbon for Supercapacitors

Supercapacitors are considered to be the most promising power source to meet the pressing requirements of energy storage. Supercapacitive electrode materials, which are closely related to the high-efficiency energy storage, have provoked more interest. Herein, we present a high-capacity supercapacitor material based on the nitrogen-doped micro-mesoporous carbon material, which is synthesized by employing urea-formaldehyde resin as carbon and nitrogen sources, zinc chloride as a porogen and SBA-15 as a hard template. With high surface area, abundant porosity and nitrogen-doped, the composite material exhibits a reversible specific capacitance of 226.3 F g−1 at the current density of 1.0 A g−1 in 6 M KOH electrolyte, and maintains a better high-class capacitance retention capability. These results show that nitrogen-doped micro-mesoporous carbon material represents a promising alternative to efficient electrode material for supercapacitors.

Influence of Temperature on the Oxygen Electroreduction Activity at Micro-Mesoporous Carbon Support

Influence of temperature on the kinetics of oxygen electroreduction on molybdenum carbide derived carbon based catalysts has been analyzed in O2 saturated 0.1M KOH solution using rotating disc electrode and cyclic voltammetry methods. The calculated kinetic current density value (|jkin| = 62.6 A m−2) at the half-wave potential (−0.05 V vs. Hg|HgO|0.1M KOH) of platinum nanoparticles modified catalyst was maximal at 60°C. Two different linear areas in the Tafel-like plot have been observed for unmodified and Pt nanoparticles modified catalysts within the studied temperature range from 10 to 80°C. The calculated experimental apparent activation energy values for the oxygen reduction were within a range from 19 to 27 kJ mol−1 for Pt nanoparticles modified carbon catalyst within potential range from 0.05 to −0.07 V vs. Hg|HgO|0.1M KOH. The oxygen reduction peak current density values decrease with increasing the temperature from 10 to 80°C.

Influence of the negative potential of molybdenum carbide derived carbon electrode on the in situ synchrotron radiation activated X-ray photoelectron spectra of 1-ethyl-3-methylimidazolium tetrafluoroborate

Negatively charged 1-ethyl-3-methylimidazolium tetrafluoroborate (EMImBF4) | Mo2C derived micro-mesoporous carbon (C) electrode interface has been studied using in situ synchrotron radiation initiated X-ray photoelectron spectroscopy (XPS) in order to estimate true potentials when slow electrochemical processes start at the C electrode used in the supercapacitors. A three-electrode system within the very wide working electrode (WE) potential region down to -1.90V (vs. Ag/AgCl wire in EMImBF4) has been used for the polarization of the C WE during the in situ XPS measurements. Parallel to XPS measurements in high vacuum chamber, the cyclic voltammetry measurements in the three-electrode system were carried out in the Ar-filled glovebox in order to obtain electrochemical data down to -2.40V (vs. Ag/AgCl wire in EMImBF4) for studied C electrode material.WE potential vs. XPS spectra relationship has been established and discussed here.

On the use of carbon black loaded nitrogen-doped carbon aerogel for the electrosorption of sodium chloride from saline water

Highly micro-mesoporous carbon electrodes have been synthesized by the polycondensation of resorcinol-formaldehyde-melamine mixtures in the presence of a carbon conductive additive. The materials showed high surface functionalization (N- and O- groups) provided by the precursors. Despite the low amount used, the conductive additive had a marked effect on the porosity of the aerogels; for a given series, the carbon black loaded materials showed similar micropore volumes and a more developed mesoporosity than the pristine aerogels. Furthermore, the activation treatment under CO2 atmosphere led to an increase in the surface area along with a widening of the mesoporosity. The synthesized aerogels were explored as electrodes for the electro-assisted removal of sodium chloride from saline water. A desalting capacity of 7.3mg/g was obtained for monolith electrodes of sample MRF-Act/CB, along with an excellent chemical stability upon charge and discharge at high polarization voltages. Such good electrochemical performance is due to the combination of an adequate pore network and surface functionalization with an enhanced electrical conductivity achieved upon the incorporation of the carbon black additive during the polycondensation of the aerogel precursors.

Lignosulphonate-cellulose derived porous activated carbon for supercapacitor electrode

A meso-microporous carbon was prepared by the combination of a template method and chemical activation with earth abundant cellulose and lignosulphonate as the sources..

Challenges of and Insights into Acid-Catalyzed Transformations of Sugars

The selective transformation of hexose and pentose sugars to intermediate platform chemicals, such as furans, is an essential step in the conversion of cellulosic and hemicellulosic biomass to biofuels and biochemicals. Yet, many challenges in achieving commercially viable processes remain. In this feature article, we outline challenges that need to be overcome to enable these transformations. Then, we present the newly introduced acid-catalyzed isomerization of aldose sugars to ketose sugars via a class of solid Lewis acid catalysts (e.g., Sn-Beta, Ti-Beta). We elucidate mechanistic insights arising from subnanometer cooperativity and solvent effects that can be controlled to tune reaction pathways and selectivity and draw parallels between heterogeneous and homogeneous Lewis acid catalysts. Subsequently, we discuss fructose dehydration to 5-hydroxyl-methylfurfural (HMF) via homogeneous and heterogeneous Bronsted acid-catalyzed chemistry. We show how fundamental insights arising from the combination of kinetics, spectroscopy, and multiscale simulations rationalize the improved yield of HMF in water–organic cosolvents. The stability of heterogeneous Lewis acid catalysts under low pH enables tandem Bronsted and Lewis acid-catalyzed reactions in a single pot that overcomes equilibrium limitations and gives a high HMF yield starting from sugar raw materials. Additionally, we provide an overview of multicomponent adsorption of biomass derivatives from solution in microporous materials and discuss how structure–property relations can lead to superior micro- and micromesoporous carbon adsorbents for reactive adsorption toward high HMF yield. Finally, we provide an outlook for the field.