Commercial Carbon Materials Research Articles

Anodic production of hydrogen peroxide using commercial carbon materials

The electrochemical production of hydrogen peroxide (H2O2) from water is an appealing alternative to substitute the classic anthraquinone process. Herein, we show a process development to maximize the efficiency of the anodic production of H2O2. Carbon materials were used as anodes to optimize process parameters such as current density, electrolyte concentration, and the pH. We found that the electrolyte concentration, pH, and the presence of a chemical stabilizer have a substantial effect on the selectivity of water oxidation to H2O2. The addition of Na2SiO3 as a stabilizer increased the H2O2 production significantly at high pH regimes. A direct relationship between CO32− ion activity and enhanced production of H2O2 was also observed. We report H2O2 concentrations in the anolyte up to 33 mmol L−1 at a current density of 100 mA cm−2 using commercial and low-cost carbon fiber paper.

Mechanical and Thermal Behavior of Fibrous Carbon Materials.

The ability of various commercial fibrous carbon materials to withstand stress and conduct heat has been evaluated through experimental and analytical studies. The combined effects of different micro/macro-structural characteristics were discussed and compared. Large differences in mechanical behavior were observed between the different groups or subgroups of fibrous materials, due to the different types of fibers and the mechanical and/or chemical bonds between them. The application of the Mooney–Rivlin model made it possible to determine the elastic modulus of soft felts, with a few exceptions, which were studied in-depth. The possible use of two different mechanical test methods allowed a comparison of the results in terms of elastic modulus obtained under different deformation regimes. The effective thermal conductivity of the same fibrous materials was also studied and found to be much lower than that of a single carbon fiber due to the high porosity, and varied with the bulk density and the fiber organization involving more or less thermal contact resistances. The thermal conductivity of most materials is highly anisotropic, with higher values in the direction of preferential fiber orientation. Finally, the combination of compression and transient thermal conductivity measurement techniques allowed the heat conduction properties of the commercial fibrous carbons to be investigated experimentally when compressed. It was observed that thermal conductivity is strongly affected under compression, especially perpendicular to the main fiber orientation.

Biochar Derived from Agricultural Wastes as a Means of Facilitating the Degradation of Azo Dyes by Sulfides

Dyes are common contaminants, some of which are teratogenic, carcinogenic, and causative of ecological damage, and dye wastewater often contains toxic sulfides. Biochar has been widely used for the adsorption and catalysis degradation of pollutants, including dyes and sulfides, due to its abundant surface functional groups and large specific surface area. Therefore, the simultaneous treatment of dyes and sulfides with biochar may be a feasible, effective, and novel solution. This study sought to utilize low-cost, environmentally friendly, and widely sourced biochar materials from agricultural wastes such as corn stalk, rice chaff, and bean stalk to promote the reduction of dyes by sulfides. Through the action of different biochars, sulfides can rapidly decompose and transform oxidizing dyes. The RCB800 (rice chaff biochar material prepared at 800 °C) was observed to have the best effect, with a degradation rate of 96.6% in 40 min and 100% in 50 min for methyl orange. This series of materials are highly adaptable to temperature and pH, and the concentration of sulfides has a significant effect on degradation rates. Compared with commercial carbon materials, biochars are similar in terms of their catalytic mechanism and are more economical. Scanning electron microscopy, transmission electron microscopy, and nitrogen adsorption and desorption characterization results indicated that biochar contains more pores, including mesopores, and a sufficient specific surface area, both of which are conducive to the combination of sulfides and dyes with biochar. X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy showed that there are oxygen-containing functional groups (examples include quinones and carboxyl groups) on the surface of biochar that promote the reaction of sulfide and dye. The formation of active polysulfides also potentially plays an important role in the degradation reaction. This article outlines a new method for improving the degradation efficiency of azo dyes and sulfides via biochar materials derived from widely sourced agricultural wastes.

Investigation of Voltage Range and Self-Discharge in Aqueous Zinc-Ion Hybrid Supercapacitors.

Aqueous zinc‐ion hybrid supercapacitors are a promising energy storage technology, owing to their high safety, low cost, and long‐term stability. At present, however, there is a lack of understanding of the potential window and self‐discharge of this aqueous energy storage technology. This study concerns a systematic investigation of the potential window of this device by cyclic voltammetry and galvanostatic charge–discharge. Hybrid supercapacitors based on commercial activated carbon (AC) demonstrate a wide and stable potential window (0.2 V to 1.8 V), high specific capacitances (308 F g−1 at 0.5 A g−1 and 110 F g−1 at 30 A g−1), good cycling stability (10000 cycles with 95.1 % capacitance retention), and a high energy density (104.8 Wh kg−1 at 383.5 W kg−1), based on the active materials. The mechanism involves simultaneous adsorption–desorption of ions on the AC cathode and zinc ion plating/stripping on the Zn anode. This work leads to better understanding of such devices and will aid future development of practical high‐performance aqueous zinc‐ion hybrid supercapacitors based on commercial carbon materials, thus accelerating the deployment of these hybrid supercapacitors and filling the gap between supercapacitors and batteries.

Investigate the effect of electrolyte and additives on the electrochemical performance of commercial hard carbon materials based Na-ion batteries

Electrolytes play an important role in the battery components it determines the electrochemical window or the working potential region of the battery according to the LUMO and HOMO energy levels and reflects its thermodynamic stability when contacting with the electrode materials. The choice of the electrolyte affects significantly the specific energy, safety, cycle life, storage performance, or operating conditions of batteries. Besides, the electrolytes could be perfectly improved its performance within the addition of some essential additives, which also help to increase the performance of the battery. In this study, the effects of NaPF6, NaClO4, NaOTf, NaFSI, and NaTFSI salts on the hard carbon anode performance were investigated in the carbonate ester solvents including EC:DMC:PC (1:1:1) of 1 M salt concentration without and with additives FEC, VC, and Py13. The compatibility hard carbon electrode-electrolyte systems were investigated for their electrochemical performance by using Galvanostatic cycling with potential limitation, Cyclic voltammetry, and electrochemical impedance spectroscopy in coin-cell type. Among the studied electrolytes, the electrolyte EC:DMC:PC (1:1:1) + 1 M NaOTf exhibited the best electrochemical performance. The specific capacity was above 246 mAh/g after 100 cycles and the Coulombic efficiency higher than 99.6%.

A novel porous carbon derived from CO2 for high-efficient tetracycline adsorption: Behavior and mechanism

High-performance adsorbents derived from wastes are of paramount significance for environmental remediation and value-added utilization. Herein, a novel porous carbon (i.e. electrolytic carbon, EC), prepared from greenhouse gas (CO2) by electrochemical reduction in molten carbonate, was investigated as an efficient adsorbent to remove tetracycline (TC) from water. The EC possessed oxygen-containing functional groups, large specific surface area (1064.8 m2 g−1), high pore volume (1.87 cm3 g−1), and rich mesopore, availing the removal of bulky TC. A rapid adsorption equilibrium (within 1 h) and a high removal efficiency (98.7%) were obtained. Moreover, the adsorption was an exothermic reaction and the whole process obeyed the pseudo-second-order kinetic and Langmuir models, gaining a saturated adsorption capacity of 393.5 mg g−1 at 25 °C, which was superior to various reported biochar and commercial carbon materials. Besides, the adsorption of EC exhibited a wide pH adaptability ranged from 2 to 9, and excellent recyclability. A π-π interaction was identified as the predominant mechanism by investigating the adsorption performance of EC and IR, XPS characterizations. These results highlight significant implication for the future application of CO2-derived carbon adsorbents in the treatment of antibiotic wastewater.

Graphene Oxide/Carbon Nanocoil Composite for High‐performance Humidity Sensor

Designing a humidity sensor with high performance to quick and accurate detect relative humidity (RH) is important in various applications. Consideration must be given to both the high response and the quick reversibility. Here, based on Quartz Crystal Microbalance (QCM) sensing platform, we utilized commercial graphene oxide as a sensing material, and added commercial carbon nanocoil to block the stacking of graphene oxide layers. The fabricated novel sensor possessed super high response (4618 Hz/97 % RH) and quick reversibility (2 s). This work not only expands the application of commercial carbon materials, but also achieves the development of high‐performance humidity sensor with commercial potential.

Catalytic performance and mechanism of biochars for dechlorination of tetrachloroethylene in sulfide aqueous solution

Biochar (BC) has been investigated as a natural and economical activator to treat organic contamination. Compared with commercial carbon materials, BCs have a better prospect of large-scale application. For the first time, this study certified degradation of tetrachloroethene (PCE) in sulfide-containing aqueous solutions catalyzed by wormwood-based BCs pyrolyzed at 600 °C, 700 °C, and 800 °C (BC600, BC700, and BC800). Interestingly, BC800 could catalyze PCE dechlorination and form acetylene and chloride ion with over 99 % nontoxic transformation in neutral and alkaline pH conditions. Furthermore, materials surface properties, BC dosages and sulfide concentrations were considered as limiting factors for dechlorination, and the last one had the strongest influence. XPS analysis demonstrated that catalytic ability of BC was attributed to pyridine nitrogen (N6) on surface, because C and O adjacent to N6 strongly favor nucleophilic reactions. These results evaluated the applicability of degrading toxic chlorinated alkenes mediated by natural carbon materials in sulfide-containing environment.

Integrating Effect of Surface Modification of Microporous Carbon by Phosphorus/Oxygen as well as the Redox Additive of p‐Aminophenol for High‐Performance Supercapacitors

AbstractIn present work, commercial microporous carbon materials are modified on the surface with phosphorus/oxygen species by using phytic acid as sole dopant, which plays crucial effect on the carbon structure, wettability, electrical conductivity, and capacitive behaviors. It reveals that with increasing the content of heteroatoms, the porosity and contact angle are decreased but the conductivity turns much larger. Furthermore, p‐aminophenol is introduced to serve as redox additive, which can produce more active surface sites by forming hydrogen bond and complexation with the surface functional groups, further providing additional pseudo‐capacitance. As a result, the energy density of carbon sample by phosphorus/oxygen doping in 1 m H2SO4 electrolyte with p‐aminophenol is as high as 9.2 Wh kg−1, which is 2.6 than that of pristine carbon. What is more, in terms of the simple operation and effective performance, the integration of surface modification toward carbon materials and redox additive can be favorable for largely enhancing the supercapacitor performance.

Synthesis Strategies of Porous Carbon for Supercapacitor Applications

AbstractSupercapacitors (SCs) have experienced a significant increase in research activity and commercialization during the past few decades. As the primary and most important electrode active material for commercial SCs, porous carbon is produced at an industrial‐scale through traditional carbonization‐activation strategies. Nevertheless, commercial porous carbon materials have some disadvantages such as high production cost, corrosion of equipment, and emission of toxic gases and byproduct pollutants during production. In recent years, huge efforts have been made to develop novel synthesis strategies for porous carbon materials. This review focuses on the pore formation mechanisms in traditional carbonization‐activation methods, emerging activation methods, template methods, self‐template methods, and novel emerging methods for the synthesis of porous carbons for SCs. Strategies developed so far for the synthesis of porous carbon materials are summarized. The mechanisms and recent advances for each strategy are reviewed. Furthermore, future directions and synthesis strategies for porous carbons are proposed.

Facile synthesis of small MgH2 nanoparticles confined in different carbon materials for hydrogen storage

We introduce a facile chemical solid state method to in situ grow MgH2 nanoparticles in various carbon materials. Commercial carbon materials, containing coconut shell charcoal (CSC), multi-walled carbon nanotube (CNT), graphite (G) and activated carbon (AC) are employed as the templates. The MgH2@X (X = CSC, CNT, G and AC) composites were successfully obtained by the simple solid state method. The hydrogen storage properties of MgH2@X (X = CSC, CNT, G and AC) composites are systematically studied by temperature-programmed desorption system, isothermal de/hydrogenation apparatus and differential scanning calorimetry measurements. Experimental results reveal that the MgH2@CSC composites have the most fascinating hydrogen absorption and desorption performance, followed by MgH2@CNT, MgH2@G and MgH2@AC composites. The dehydrogenation of MgH2@CSC composites begins at 245 °C. Moreover, the MgH2@CSC composites exhibit superior de/hydrogenation kinetic performance. The composites could desorb 5.4 wt% hydrogen within 10 min at 325 °C, and the dehydrogenated composites take up 5.0 wt% hydrogen within 5 min at 250 °C under 2 MPa H2 pressure. Among the carbon materials, CSC with layered structure composed of interconnected wrinkles is most beneficial to maintain the high dispersity and nano size of MgH2 nanoparticles, resulting in the superior de/hydrogenation performance.

The surface modification of the separator for electrocatalyst in lithium-sulfur batteries

The introduction of electrocatalyst can promote redox kinetics to improve the performance of lithium-sulfur (Li-S) batteries. Currently, much attention has been paid to modify site and effectiveness of electrocatalysts. Herein, the commercial platinum carbon (Pt/C) material was investigated to modify the polypropylene separator from the cathode side (PP@Pt battery), which was compared with the cathode doped (C-S-Pt) and unmodified (PP) batteries. The results show that PP@Pt battery delivers superior cycle performance and cycling stability than other batteries, confirming that the catalytic effect of Pt/C layer on the separator precede that of cathode doping. This is attributed to that the highly dispersed Pt/C layer is in intimate contact with the sulfur electrode to provide sufficiently active sites, which not only enhances the electronic conductivity but also provides a desired reaction site.

Permeability of fibrous carbon materials

The air permeability of a number of commercial fibrous carbon materials: soft non-woven felts, rigidised felts and rigid boards, based on either PAN- or Rayon-derived fibres presenting various diameters, graphitised or not, and consolidated by different methods, was measured and investigated. Consistent behaviours were found within families of closely related materials, but the diversity of porous structures prevented any model, including the very popular Tomadakis–Sotirchos equation, to fit all results. The Archie’s coefficient and the tortuosity factor for viscous flow were thus calculated. Not only all data were perfectly aligned on one single master curve, but the analysis was extended to many other fibrous materials and the same master curve was found to be relevant. The Archie’s coefficient thus appears to be an intrinsic property, purely defined by the material geometry, as it does not depend on the 1D, 2D or 3D type of flow. A fitting equation was proposed, encompassing all fibrous materials in very broad ranges of porosities and porous structures.

Facile hydrogel-derived sub-10 nm tin–iron alloy embedded in 3D carbon nanocorals with improved cycle life and rate capability

Tin-based alloys have been regarded as promising anodes to replace commercial carbon materials for Li-ion batteries, but their Li-storage performance, especially cycle life, still fails to meet the requirements for electric vehicles and large-scale electricity storages. Herein, we propose a facile and scalable hydrogel-derived route for uniformly immobilizing sub-10 nm Sn-based alloys within three-dimensional (3D) carbon nanocorals, using polymer-hybridized cyano-bridged coordination polymer hydrogels (cyanogels) as precursors. As a representative example, 3D Sn–Fe@C nanocorals have been constructed through freeze-drying and thermal-autoreduction processes using polyethylene glycol (PEG) hybridized Sn(IV)–Fe(II) cyanogels as precursors. PEG plays critical roles in structural tailoring of hybrid cyanogels and size control of Sn–Fe alloys, and as a result, the average alloy size in optimized Sn–Fe@C nanocoral is only 5.9 nm. The ultrasmall alloy size, uniform dispersity of alloy, as well as coral-like framework structure, enable the Sn–Fe@C nanocorals to exhibit long-term cyclic life and high-rate performance.

Composite materials based on active carbon/TiO2 for photocatalytic water purification

The present work describes the preparations of active carbon (AC) – titania composites with different AC/TiO2 ratio, their characterization using XRD, BET and SEM and evaluation of adsorption capacity and photocatalytic activity in aqueous solution using azo-dye Acid Orange 7 (AO7). Composite materials based on AC/TiO2 were prepared from commercial active carbon (1737 m2 g-1) and TiO2 (P25, 45 m2 g-1) materials by the mixing method. The studied parameters were the ratio of AC/TiO2, hydrothermal treatment and milling of as-prepared composites.The composites show increased BET surface area proportional to the content of AC in the material. The disappearance of AO7 is due to the combination of two processes, e. g. adsorption and photocatalytic oxidation which take place in parallel. Thus the overall removal of AO7 has been corrected on adsorption (measured in dark) to obtain the rate of AO7 disappearance due to photocatalytic oxidation (PO). The optimum ratio of AC/TiO2 was found to be 0.23 where PO rate is only slightly lower than that for P25 and overall AO7 removal is twice higher than for P25 itself. The less intensive (low-frequency) milling of the composite results in the decrease of carbon particle size, increase in AO7 adsorption and decline in the PO of AO7. More intensive milling (high-frequency) results in the decrease of the anatase content, appearance of the small amount of brookite and almost negligible PO rate of AO7. Irradiation of low-frequency milled AC/TiO2 composite in aqueous suspensions resulted in the generation of a comparable concentration of hydroxyl radical spin-adduct (DMPO−OH) as non-milled composite, high-frequency milled composite revealed substantially lower DMPO−OH concentration which can be explained by the increased concentration of carbon-centered radicals in AC acting as scavengers of photogenerated electrons.

Ultrathin MOF nanosheet assembled highly oriented microporous membrane as an interlayer for lithium-sulfur batteries

Lithium sulfur (Li-S) batteries are attracting increasing attentions as promising next-generation rechargeable batteries. However, the rapid capacity fading of sulfur cathodes caused by the shuttling of polysulfide intermediates between the cathodes and anodes restricts the application of Li-S batteries. In this work, a facile wet-chemistry method is developed for the direct synthesis of few-molecular-layer thin metal-organic framework (MOF) nanosheets without using surfactant. By assembling these ultrathin MOF nanosheets with a facile vacuum filtration method, a highly oriented and flexible MOF membrane with favorable mechanical properties is achieved for the first time. The excellent features make the as-prepared MOF nanosheets ideal to fabricate lightweight interlayer modified separators for suppressing the polysulfide shuttling of Li-S batteries. When using the MOF membrane modified separator, the Li-S batteries made from commercial carbon materials exhibits the significantly enhanced cycling stabilities. This work brings new opportunities for the synthesis and application of MOF materials.

Enhanced Catalytic Properties of Carbon supported Zirconia and Sulfated Zirconia for the Green Synthesis of Benzodiazepines

AbstractThis work reports for the first time a new series of promising porous catalytic carbon materials, functionalized with Lewis and Brønsted acid sites useful in the green synthesis of 2,3‐dihydro‐1H‐1,5‐benzodiazepine – nitrogen heterocyclic compounds. Benzodiazepines and derivatives are fine chemicals exhibiting interesting therapeutic properties. Carbon materials have been barely investigated in the synthesis of this type of compounds. Two commercial carbon materials were selected exhibiting different textural properties: i) Norit RX3 (N) as microporous sample and ii) mesoporous xerogel (X), both used as supports of ZrO2 (Zr) and ZrO2/SO42− (SZr). The supported SZr led to higher conversion values and selectivities to the target benzodiazepine. Both chemical and textural properties influenced significantly the catalytic performance. Particularly relevant are the results concerning the non‐sulfated samples, NZr and XZr, that were able to catalyze the reaction leading to the target benzodiazepine with high selectivity (up to 80 %; 2 h). These results indicated an important role of the carbon own surface functional groups, avoiding the use of H2SO4. Even very low amounts of SZr supported on carbon reveal high activity and selectivity. Therefore, the carbon materials herein reported can be considered an efficient and sustainable alternative bifunctional catalysts for the benzodiazepine synthesis.

Nitrogen-containing high surface area carbon cryogel from co-condensed phenol–urea–formaldehyde resin for CO2 capture

A cost-effective nitrogen-doped super high surface area carbon cryogel has been successfully synthesized from phenol–urea–formaldehyde (PUF) resin. Pore structure and chemical characteristics were investigated using scanning electron microscopy, Fourier transform infrared spectroscopy, element analysis, X-ray photoelectron spectrometry, mercury porosimetry and N2 adsorption–desorption. It was found that the organic cryogel with mesopores and macropores from PUF resin having a N content of 9.03 wt%, which is an ideal precursor for preparing N-doped carbon cryogels. The carbon cryogel obtained having a high apparent surface area of up to 1710 m2/g, large micropore volumes up to 0.64 cm3/g, a small average micropore width of 1.04 nm and a moderate nitrogen content of 2.08 wt%. The lab-made carbon cryogel showed good CO2/N2 sorption selectivity, 15.8:1 at 273 K and 16.4:1 at 298 K. The CO2 capture capacities as high as 5.5 mmol/g at 273 K and 4.5 mmol/g at 298 K up to 1 bar were obtained, which were among the highest compared to other commercial carbon materials.

Carbon Nano-Onions Synthesized By Laser Pyrolysis As Catalyst Support in Proton Exchange Membrane Fuel Cells

Proton exchange membrane fuel cells (PEMFC) typically utilize nanostructured carbon (such as carbon black, carbon nanotubes, graphene and porous carbon) as the support material for catalysts. The durability and electrical conductivity of the material are important contributors to the fuel cell performance, as well as the structural design to maximize the triple phase boundary between the fuel, the catalyst and the electrolyte membrane. In view of engineering the structure and composition of the carbon catalyst support, a versatile manufacturing method with flexibility in size, shape, structure, and properties (such as electrical conductivity) of the carbon material would open up a chance to investigate an expansive composition matrix for potential improvements of the cell performance. In addition, for potential commercialization, processes that are clean and high-throughput are desired. Laser pyrolysis of hydrocarbons has been established as a widely adopted gas phase production of carbon nanoparticles. In particular, multilayered particles with concentric graphitic shells, commonly called carbon nano-onions, are of interest as the size, shape and the number of graphitic shells are easily tuned by adjusting the experimental parameters. In this work, we present a CO2 laser induced pyrolysis of gaseous hydrocarbons (such as acetylene and ethylene) that generates various types of carbon nanoparticles, and demonstrate that these carbon nano-onions have superior durability and electrical conductivity to commonly used commercial carbon materials such as Vulcan XC-72. Platinum-decorated carbon nano-onions have been used to fabricate PEMFCs and they are shown to have comparable performance to conventional cells, and the accelerated stress test reveals that the durability of the cells have improved.

Intensification of catalytic wet peroxide oxidation with microwave radiation: Activity and stability of carbon materials

Several commercial carbon materials have been tested as catalysts in the Microwave-assisted Catalytic Wet Peroxide Oxidation process (MW-CWPO). Two graphites (G-F and G-S), two activated carbons (AC-M and AC-C), two carbon blacks (CB-V and CB-A) and silicon carbide (SiC) were selected due to their MW-absorbing properties. Phenol (100 mg L−1) was used as target pollutant, operating in batch at pH0 3, 120 °C, 500 mg L−1 catalyst load and the theoretical stoichiometric amount of H2O2 (500 mg L−1). All carbon materials showed to be active in terms of H2O2 decomposition and phenol oxidation. Nonetheless, G-S and AC-M stood out as the most active materials in terms of TOC removal, with values of 94 and 93% TOC elimination, respectively. On the other hand, both carbon blacks and G-F yielded a significantly lower TOC degradation. Surface chemistry seems to rule the activity of graphites, in particular the pH slurry (4.5 for G-S and 8.4 for G-F). The most active catalysts, G-S and AC-M were used in 5 consecutive cycles in order to study their stability. While G-S remained active, AC-M.