Surface Area Of Carbon Materials Research Articles

Turning coal hydrogenation liquefaction residue into high conductivity carbon black with magnesium citrate-assisted steam activation followed by high temperature treatment

The high conductivity carbon black was prepared using coal hydrogenation liquefaction residue as raw material, through a combination methods of solvent extraction purification, magnesium citrate-assisted carbonization, steam activation, and high-temperature treatment. The effects of carbonization and activation process parameters, heat treatment temperatures, and other factors on the microstructure, specific surface area, degree of graphitization, and conductivity of the carbon black were studied. The coal direct liquefaction residue was firstly purified using a xylene and tetrahydrofuran solution with a volume ratio of 1:1 by centrifugal separation method to obtain coal liquefaction asphalt. Then, the coal liquefaction asphalt was mixed with magnesium citrate in a mass ratio of 3:7 and ball-milled for 90 min. After carbonizing at 950 °C for 120 min, magnesium ions were leached out with hydrochloric acid. The obtained sample was activated with steam at 900 °C for 100 min and then underwent high-temperature treatment at 1500 °C under a N2 atmosphere for 120 min. The microstructure of the conductive carbon black exhibited an irregular blocky structure with an average particle size of 2–10 μm. The specific surface area of carbon material was 579.69 m2/g, with the pore distribution predominantly microporous, accounting for 69.81 % of the total pore volume. It featured a higher degree of graphitization (ID/IG=1.06) and fewer surface oxygen-containing functional groups compared with coal direct liquefaction residue. Electrochemical testing showed that the electrical resistance of the carbon material was only 1.55 Ω, and the reversible capacity under a current density of 1 A/g was 96 mAh/g, which are superior to those of the existing commercial conductive carbon black. The microporous structure and higher degree of graphitization facilitate efficient electron transmission, while the lower content of surface oxygen functional groups effectively reduces electron transfer resistance. This work offers new insights into the structural design and performance enhancement of coal liquefaction residue-derived conductive carbon black functional materials. Furthermore, it has significant implications for the future development of conductive carbon black in energy saving and energy storage.

Synergistic sorption: Enhancing arsenic (V) removal using biochar decorated with cerium oxide composite

Removal of Arsenic, a potent carcinogen from aqueous environments is imperative to ensure the provision of potable water and to mitigate the risks associated with its exposure. In this study, we explore a composite based on biochar derived from coconut-shell loaded with Cerium Oxide for the removal of Arsenic (As(V)) by adsorption. The synthesized adsorbent combines the characteristic high specific surface area of carbon materials with high adsorption affinity of CeO2 towards Arsenic to create a synergistic effect. Various parameters such as initial concentration, adsorbent dosage, presence of coexisting anions etc., were investigated to determine the kinetics and thermodynamics of adsorption. The effect of initial pH on the adsorption was also investigated and maximum removal efficiency of around 99 % was observed. A very high adsorption capacity was observed and highlighting the genesis of a highly effective adsorbent for the removal of As(V) incorporating an inexpensive and ecologically acceptable approach.

Enhanced electrochemical performance and interdiffusion behavior of sodium ions in onion-derived freeze-dried and KOH-activated carbon for sodium-ion battery anodes

Biomass-derived carbon materials are widely regarded as promising anode materials for sodium-ion batteries (SIBs) owing to their environmental friendliness, high electronic conductivity, stability, and low cost. However, their commercial application is restricted because of their low capacities and poor cycling stabilities. Heteroatom doping and increasing the active specific surface area of carbon materials have proven to be key to solving these problems. In this study, a facile activation and annealing process combined with freeze drying and KOH treatment was used to successfully prepare nitrogen-doped onion-derived carbon materials (dried onion (DO) and freeze-dried onion (FDO)) with high specific surface areas. The obtained carbon materials exhibited excellent electrochemical performances as anodes for SIBs, delivering high discharge reversible capacities of 140.5 (DO) and 151.4 (FDO) mAh/g at a current density of 0.05 A/g after 30 cycles. The capacities reached 45 (DO) and 66 (FDO) mAh/g at 30 A/g. Specifically, FDO//Na3V2(PO4)3@C full cells achieved a reversible capacity of 43.9 mAh/g with a specific energy of 91.5 Wh kg−1 at 5 C after 1,000 cycles, indicating that it provides broad prospects for the energy storage system of SIBs.

RGO and CNTs synergistically modified mixed-phase nickel sulfide nanohybrids with abundant redox-active sites for high-performance hybrid supercapacitors

Hybrid supercapacitors (HSCs) integrating high energy density and power density have great prospects for applications in new high-performance energy storage and conversion devices. Herein, a novel reduced graphene oxide (RGO) and carbon nanotubes (CNTs) synergistically modified mixed-phase nickel sulfide (NiS/NiS2) nanohybrids (NSRCs) were successfully designed and synthesized by a facile one-step solvothermal method. Benefiting from the high conductivity and high specific surface area of carbon materials and the high specific capacity of nickel sulfide, as well as the stable nanostructures constructed by the synergistic effect of multiple components, the synthesized novel NSRCs nanohybrids exhibit impressive electrochemical performances, such as high specific capacity of 178.2 mAh g−1 (1604.1 F g−1) at 0.6 A g−1, excellent rate capability (57.3 % at 20 A g−1). Furthermore, the assembled hybrid supercapacitors (NSRC-24//AC HSC) with optimal NSRC-24 electrode and activated carbon (AC) electrode imparted a high energy density of 44.2 Wh kg−1 at a power density of 359.2 W kg−1 and excellent cycling stability (98.1 % capacity retention after 12,000 cycles at 5 A g−1). Thus, the synthesized novel NSRCs nanohybrids are highly promising candidates as advanced electrode materials for aqueous high-performance energy storage devices.

Tailoring hierarchically porous structure of biomass-derived carbon for high-performance supercapacitors

Biowaste-derived hierarchical porous carbon materials and understanding their structure-property relationship have a significant impact on the development of low-cost and high-performance supercapacitors. Herein, we report the effective one-step construction of large specific surface area and hierarchical porous carbon materials (CPC) using waste corncobs as raw material and investigated the relationship between intrinsic pore characteristics and specific capacitance. The textural properties such as surface area and pore characteristics, are controlled by modulating the various activating agent, carbonization temperature and time. The as-prepared porous carbon material (particularly CPC-3) at activation temperature of 700 °C obtained via potassium permanganate modulation with optimal specific surface area and volume of pores 1612.86 m2 g−1 and 2.25 cm3 g−1, which exhibited the ultra-high capacitance of 691.05 F g−1 at a current density of 0.5 A g−1 with good rate capability. In addition, the electrode exhibits excellent capacitance retention of 109.7 % over 10000 charge-discharge cycles at a current density of 10 A g−1. Furthermore, the assembled symmetric supercapacitor using CPC-3 and PVA-KOH gel electrolyte delivered a high energy/power density of 16.47 Wh kg−1/15360 W kg−1, respectively. The as-prepared quasi-solid-state device also shows superior applicability and outstanding cycling stability over a wide temperature range of −25 to +60 °C. This work provides a fundamental understanding of the structure-property relationship of the biomass-derived hierarchical porous carbon and allows for the development of supercapacitors in harsh temperature conditions.

Activating biomass carbon with metallurgical slag by pyrolysis in molten salt for high-performance supercapacitors.

Pyrolysis of sustainable biomass to advanced carbon materials for energy storage is key-enabling in energy and environmental sustainability. However, obtaining carbon materials with well-defined microstructure and composition for high-performance energy storage is extremely challenging. Herein, efficient activation of biomass carbon is realized by introducing extra metallurgical slag during pyrolysis of coconut shell in Na2CO3-K2CO3 molten salt. The molten salt guides the formation of carbon with a hierarchical honeycomb-like nanostructure, while the metallurgical slag facilitates enhanced doping of the heteroatom species, conjointly contributing to the increase of the specific surface area of carbon materials from 424 m2 g-1 to 1451 m2 g-1 and the extension of the single N dopant to multiple dopants of N, P, Zn and Co. Such adequate tuning of the microstructure and composition in the pyrolysis product increases the capacitance for supercapacitors from 30 F g-1 to 135 F g-1 at 0.5 A g-1. The results can provide new insights for the controllable upgradation of both biomass and waste industrial slag toward enhanced energy storage.

Polysaccharide of agar based ultra-high specific surface area porous carbon for superior supercapacitor

Although extensive research has been focused on porous carbon in supercapacitor, the simple and non-template preparation of high specific surface area (SSA) carbon material with hierarchical porous structure is still a lingering issue. Herein, the cross-linked hierarchical porous carbon with ultra-high SSA of 3184 m2 g−1 is prepared via the sol-gel follows the freeze drying and followed activation process. Agar is used as carbon precursor, L-arginine is nitrogen sources, and the formed gel is activated by KHCO3. The obtained N-doped porous carbon shows a superior specific capacitance of 443.0 F g−1 at 0.5 A g−1 in 6 M KOH, and exhibits an excellent rate capability (255 F g−1 at 50 A g−1). Furthermore, due to the combined synergistic effect of high SSA, hierarchical porous structure and N doping, the symmetric supercapacitor that assembled with the prepared gel electrolyte of Agar-Na2SO4 achieves a superior energy density of 35.5 Wh kg−1 and a long cycle life with the capacitance retention of 99.7% after 20,000 cycles. This work provides an efficient and simple method to prepare ultra-high surface area, hierarchical porous structure carbon materials for high performance supercapacitor.

ВЛИЯНИЕ СВОЙСТВ УГЛЕРОДНЫХ МАТЕРИАЛОВ НА УДЕЛЬНУЮ ЭНЕРГИЮ И ДЛИТЕЛЬНОСТЬ ЦИКЛИРОВАНИЯ ЛИТИЙ-СЕРНЫХ АККУМУЛЯТОРОВ

The effect of the structure and the specific surface area of carbon materials, contained in positive electrodes, on the peculiarities of cycling of lithium-sulfur cells (the depth of electrochemical reduction of sulfur and lithium polysulfides, the changes in capacity and Coulomb efficiency of cycling) was studied. The studies showed that the depth of electrochemical transformations of sulfur and lithium polysulfides depended not only on the specific surface area of the carbon material contained in positive electrodes, but also on the structure and the surface morphology of the carbon material particles.

Psyllium-Husk-Assisted Synthesis of ZnO Microstructures with Improved Photocatalytic Properties for the Degradation of Methylene Blue (MB).

Wastewater from the textile industry is chronic and hazardous for the human body due to the presence of a variety of organic dyes; therefore, its complete treatment requires efficient, simple, and low cost technology. For this purpose, we grew ZnO microstructures in the presence of psyllium husk, and the role of psyllium husk was to modify the surface of the ZnO microstructures, create defects in the semiconducting crystal structures, and to alter the morphology of the nanostructured material. The growth process involved a hydrothermal method followed by calcination in air. Additionally, the psyllium husk, after thermal combustion, added a certain value of carbon into the ZnO nanomaterial, consequently enhancing the photocatalytic activity towards the degradation of methylene blue. We also investigated the effect of varying doses of photocatalyst on the photocatalytic properties towards the photodegradation of methylene blue in aqueous solution under the illumination of ultraviolet light. The structure and morphology of the prepared ZnO microstructures were explored by scanning electron microscopy (SEM) and powder X-ray diffraction (XRD) techniques. The degradation of methylene blue was monitored under the irradiation of ultraviolet light and in the dark. Also, the degradation of methylene blue was measured with and without photocatalyst. The photodegradation of methylene blue is highly increased using the ZnO sample prepared with psyllium husk. The photodegradation efficiency is found to be approximately 99.35% for this sample. The outperforming functionality of psyllium-husk-assisted ZnO sample is attributed to large surface area of carbon material from the psyllium husk and the synergetic effect between the incorporated carbon and ZnO itself. Based on the performance of the hybrid material, it is safe to say that psyllium husk has high potential for use where surface roughness, morphology alteration, and defects in the crystal structure are vital for the enhancing the functionality of a nanostructured material. The observed performance of ZnO in the presence of psyllium husk provides evidence for the fabrication of a low cost and efficient photocatalyst for the wastewater treatment problems.

Potassium citrate assisted synthesis of hierarchical porous carbon materials for high performance supercapacitors

Biomass resources are promising precursors for porous carbon materials attributing to their renewable, plentiful and low-cost characteristics. In this work, hierarchical porous carbon materials are synthesized by carbonizing the mixture of starch rich biomass precursor and potassium citrate. Potassium citrate is vital for the formation of hierarchical porous structure. The specific surface area of carbon material is greatly enhanced with the addition of potassium citrate and gradually increases with the rise of carbonization temperature. APCs-750 obtained from 750 °C displays the best capacitance performance attributing to a high specific surface area (1105.64 m2 g−1) and a high oxygen content (10.25 at.%). APCs-750 exhibits the highest specific capacitance of 242.5 F g−1 at 0.2 A g−1, good rate performance (119.0 F g−1 at 50 A g−1) and excellent stability (retaining 96.5 % after 20,000 cycles). In addition, the symmetric supercapacitor of APCs-750 shows a high energy density of 12.38 Wh kg−1 at the power density of 99.72 W kg−1 and keeps a capacitance retention of 91.3 % after 20,000 cycles. Hence, this work provides a facial strategy to synthesis high capacitance performance hierarchical porous carbon materials from starch rich precursor.

High-yield and nitrogen self-doped hierarchical porous carbon from polyurethane foam for high-performance supercapacitors

Confronted with the environmental pollution and energy crisis issues, upcycling of waste plastics for energy-storage applications has attracted broad interest. Polyurethane (PUR) is a potential candidate for the preparation of N-doped carbon materials. However, its low carbon yield limits the utilization of PUR waste. In this study, PUR foam was converted into N-doped hierarchical porous carbon (NHPC) through an autogenic atmosphere pyrolysis (AAP)-KOH activation approach. An ultra-high carbon yield of 55.0% was achieved through AAP, which is more than 17 times the carbon yield of conventional pyrolysis of PUR. AAP converted 83.2% of C and 61.0% of N in PUR into derived carbon material. The high conversion rate and self-doping effect can increase the environmental and economic benefits of this approach. KOH activation significantly increased the specific surface area of carbon materials to 2057 m2 g−1 and incorporated hierarchical porous structure and O-containing functional groups to the carbon materials. The obtained NHPCs were applied to improve the performance of supercapacitors. The electrochemical measurement revealed that NHPCs exhibited a high specific capacitance of 342 F g−1 (133 F cm−3) at 0.5 A g−1, low resistance, and outstanding cycling stability. The energy density and power density of the supercapacitor were improved to 11.3 W h kg−1 and 250 W kg−1, respectively. This research developed a possible solution to plastic pollution and energy shortage.

Transformation of solid plastic waste to activated carbon fibres for wastewater treatment

In this study, the solid waste plastic was converted into activated carbon fibres through carbonization and chemical activation process. The morphological structure, composition, thermal stability and pore structure of the produced activated carbon materials were characterized. The results revealed that the activation process substantially increases the specific surface area of carbon materials via forming large micropores and mesopores (0.01–0.85 cm3g-1) within average nano size range of 50–100 nm. This study provides an effective means to remove the thymol blue dye via adsorption over activated carbon (ACs) as adsorbent. Batch adsorption of thymol blue was conducted to verify the effect of variety of pH, dye concentrations, contact time, adsorbent dose and temperature. The highest dye removal efficiency (approximately 98.05%) of ACs generated from waste plastic polybags, cups and bottles was observed at 10 ppm of thymol blue dye. The results also exhibited that the dye adsorption was favourable at basic pH (9.0) and increasing amount of adsorbent dosage promotes the dye removal efficiency. The excellent dye removal performance was primarily due to the presence of higher available surface area on the surface of developed carbon fibres. In addition, the current results have given the large overview and useful information of dye removal properties by adsorption isotherm and kinetic measurements. The adsorption kinetics and thermodynamic prospective of formed ACs explored the physical, spontaneous and endothermic adsorption process. The as prepared ACs provided easy regeneration of adsorbents with fast response which further suggests the efficiency of nanoparticles to promote their usage up to 5 consecutive cycles. The current work illustrated that better means to transform solid waste plastic into carbon fibres for providing effective and cheap viable option for the fast removal of thymol blue dye from waste water samples.

ОЦЕНКА ПОВЕРХНОСТИ УГЛЕРОДНОГО МАТЕРИАЛА ПУТЕМ ЕМКОСТНЫХ ИЗМЕРЕНИЙ ДВОЙНОСЛОЙНОГО СУПЕРКОНДЕНСАТОРА

The paper considers the possibility of calculating the surface of carbon materials by measuring the capacitance of symmetric supercapacitors. It is shown that this approach allows us to obtain results that are in good agreement with the BET method. Traditional carbon materials for symmetric supercapacitors - activated carbons and carbon composites based on carbon black - are considered and compared. The capacitances of supercapacitors at different charge rates were measured in the work. When using the exponential model for almost all samples, the values of the maximum possible specific area of the sorbed ions are close to the specific surface of the materials calculated by the BET method. The exception is SX1G, for which a twofold difference between the values of specific areas is observed. This difference may be due to the non-equipotential, mostly microporous structure of the material, which is difficult for large solvated cations. Based on the experimental data obtained, it was suggested that it is possible to estimate the specific surface area of carbon materials based on the calculated capacitance. An important conclusion for practice is made - the limit of supercapacitor capacity growth is reached for materials with a specific surface area of 1500 m2/g

Zero-waste: Carbon and SiO2 composite materials from the solid residue of the hydrothermal liquefaction of anaerobic digestion digestate for Li-ion batteries

Hydrothermal liquefaction (HTL) of wet biomass waste (e.g., from anaerobic digestion (AD) digestate) is an efficient technology to produce bio-crude, a hydrocarbon based renewable fuel. However, the solid waste by-product has limited use and could be an environmental nuisance if not managed appropriately. Herein, we demonstrate a sustainable way of transforming the solid residue generated through HTL of AD of sugarcane bagasse digestate into potential electrodes for lithium-ion battery (LIB). Briefly, the solid residue from the HTL process was converted into hard carbon (HC@WA) or converted through KOH activation to a carbon with a higher specific surface area carbon material (HC@AA). The structural and morphological characterizations confirm the encapsulation of SiO2 nanoparticles in the carbon matrix to form composite materials. When employed as anode materials in LIB, HC@WA and HC@AA achieve specific capacities of 452 mAh/g and 319 mAh/g respectively, and with long term cycling stability. The practical feasibility of the electrode materials was assessed by fabricating full cells with commercial LiFePO4 (LFP) cathode material. The full cells delivered good specific capacities and cycling stabilities, confirming the potential of the composite materials as electrodes for LiB. Thus, the solid residue after HTL of AD digestate could be one of the sustainable sources to develop materials for energy storage systems, thereby paving the way towards zero-waste and clean energy for a circular economy.

Pd(1 1 1)/SnO2(1 0 1) heterostructure on porous N-carbon material as enhanced catalyst for formic acid electrooxidation

High specific surface area carbon materials act as a critical factor of fuel cell catalyst carriers. In this study, the PtxPdy/SnO2/GC nanocatalysts were successfully synthesized at different molar ratios of Pt and Pd to conduct the formic acid oxidation. In addition, the N-doped porous carbon carrier (GC) was prepared with graphene oxide and gelatin through the solvated volatilization/nanometer SiO2 template/KOH activation, and the prepared carrier GC took up a large specific surface area (SBET = 1104.5 m2/g). The fine-tuning of the atomic ratio of Pt and Pd was demonstrated to further guide the growth of ultra-small nanocrystals that achieved an average size of 2.52 nm and displayed uniform distributions on the prepared GC carrier. Compared with PtPd/GC, PtSnO2/GC and Pt/GC catalysts, Pt1Pd1/SnO2/GC took up a larger electrochemical activity area of 528.93 cm2/mg, and the positive sweep peak current density reached 2258.45 mA/mgPt at 0.75 V. As confirmed by the DFT analysis, the heterojunction structure formed between the Pt-Pd (111) and SnO2 (101) surfaces would contribute to the electron transport. The optimal electrochemical performance was reasonably attributed to the synergistic effect exerted by PtPd alloy and SnO2, as well as N-doped porous carbon carrier.

Activation of Asphalt to Prepare High Surface Area Carbon Material

High surface area porous carbon material was prepared via a method of activating asphalt with pretreatment. The crystalline, textural structure, morphology, and surface functionalities of the samples were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), diffuse reflectance FTIR spectroscopy (DRIFTS), and Brunauer-Emmett-Teller (BET) techniques. When the asphalt was pretreated at 400 °C for 3 h under Ar flow, and then activated using KOH as activating agent at 800 °C for 3 h under Ar flow, the prepared porous carbon material has an amorphous nature and possesses a high surface area of 2460 m2/g, a narrow pore size distribution of 3 ∼ 5 nm, and a mean pore diameter of 3.8 nm.

Preparation of cigarette butts/coal‐based porous carbon and its catalytic methane decomposition to hydrogen

AbstractA new type of cigarette butts/coal‐based composite porous carbon was prepared by potassium hydroxide chemical activation method and used for methane decomposition to hydrogen. The effects of mass mixing ratio of the used cigarette butts/coal and carbonization temperature on the surface properties and structure of carbon materials were studied. The results show that the optimal mass mixing ratio of cigarette butts/coal is 1:3, and the increase in temperature can promote the specific surface area of carbon materials from 1850 to 2785 m2/g, the distribution of pore size is also changed from a large number of micropores to mesopores, and the structure became more disordered. DT/YT‐3‐1023 has the highest initial activity, DT/YT‐3‐1123 has the highest stability, and a certain amount of carbon fibers are deposited on the surface of carbon materials after the reaction.

Hydrogen Storage on Nanoporous Carbon Foam for Electrochemical Applications

To be able to mitigate the threat of climate change, we need an alternative to fossil fuels. The use of hydrogen in fuel cells is an ideal candidate because hydrogen can be produced in many different ways and has a high energy density. However, one challenge in using hydrogen as a fuel is its storage. Storing hydrogen as compressed gas typically requires large pressures to meet US Department of Energy (DOE) targets, which leads to large losses during compression. By using solid state storage, we can use lower pressures for storage. Of the different kinds of solid state storage, physisorption on carbon materials has great potential because of its fast kinetics, reversibility, and the cost effectiveness of carbon materials.In this research, we investigate the storage of hydrogen gas through physical adsorption on a sodium ethoxide-derived carbon foam. This carbon foam has all the necessary requirements of a good hydrogen sorbent: very large surface area and a large micropore volume. This material is also easy to synthesize: sodium ethoxide is pyrolyzed in N2 to make carbon, which is then washed in DI water and vacuum filtered. Unlike many other high surface area carbon materials, this carbon foam does not require a two-step carbonization-activation process, nor does it require a sacrificial template. This means it is more scalable and energy efficient compared to other synthetic carbon materials. [1,2]The hydrogen adsorption capability of this material is tested at both 77K and 298K at elevated pressures (up to 9.5 MPa). Both the excess hydrogen uptake and the total hydrogen uptake are discussed. The values obtained are comparable with benchmark materials such as MOF-5 and IRMOF-20, which have 8 wt% and 10 wt% total uptake at 10 MPa, respectively, [3] and could plausibly meet US DOE targets for light duty vehicle application (5.5 wt% total uptake) at a much lower pressure than conventional compressed gas storage (usually 70 MPa). This work shows the potential of nanoporous carbon materials such as ours to work as a new storage system or as a ‘range extender’ of sorts for existing fuel cell vehicles.[1] Lyth, S. M., Shao, H., Liu, J., Sasaki, K., and Akiba, E., 2014, “Hydrogen Adsorption on Graphene Foam Synthesized by Combustion of Sodium Ethoxide,” Int. J. Hydrogen Energy, 39(1), pp. 376–380.[2] Choucair, M., and Mauron, P., 2015, “Versatile Preparation of Graphene-Based Nanocomposites and Their Hydrogen Adsorption,” Int. J. Hydrogen Energy, 40(18), pp. 6158–6164.[3] Ahmed, A., Seth, S., Purewal, J., Wong-Foy, A. G., Veenstra, M., Matzger, A. J., and Siegel, D. J., 2019, “Exceptional Hydrogen Storage Achieved by Screening Nearly Half a Million Metal-Organic Frameworks,” Nat. Commun., 10(1), pp. 1–9.

Study of Thermochemical Transformations of Bast of Birch Bark, Structure and Properties of the Produced Porous Carbon Materials

The porous structure and sorption properties of carbon materials produced by thermochemical activation of the bast of birch bark with potassium hydroxide at 800°C have been studied. The effect of the amount of introduced KOH on the specific surface area of carbon materials obtained from bast was established. The selection of the optimal conditions for the preliminary carbonization of the bast was carried out, providing after thermal activation with KOH the formation of porous carbon materials with a specific surface of up to 2469 m2 g–1, a total pore volume of up to 1.085 cm3 g–1, a micropore volume of up to 0.84 cm3 g–1, and an average size pores less than 2.0 nm. It is shown that preliminary carbonization of bast at 500–580°С and subsequent activation with KOH at 800°С shifts the pore distribution in the resulting carbon materials towards smaller sizes (0.5–1.0 nm). It was found that carbon materials produced from heat-treated birch bast have a sorption activity for benzene, which exceeds the performance of foreign industrial carbon sorbents by 2.4 times and domestic active carbons of SKT-3 and SKT-10 grades by 3.4 times. Pre-carbonization of birch bast increases the yield of porous carbon materials by a factor of 3–4 compared to their yield when using untreated bast.

The Effect of Polytetrafluoroethylene Content in Porous Carbon Materials on Their Structural and Electrochemical Characteristics by the Example of Oxygen Reduction to Hydrogen Peroxide

The results on how polytetrafluoroethylene (PTFE) affects the structural and electrochemical characteristics of porous composite materials based on furnace black СН600, acetylene black А437E, and mesostructured carbon СМК-3 are analyzed. Carbon materials differ by their preparation method, texture, wettability with respect to aqueous electrolyte, and specific surface area. The characteristics of the texture of original carbon materials and their mixtures with PTFE (5–70 wt %) are determined by the low-temperature adsorption of nitrogen. The composition materials are used as the electrode material in the working layer of gas-diffusion electrodes (GDE). The effect of PTFE on the volume and size of pores, the surface area of carbon materials, the volume of pores filled with electrolyte, the electric double layer capacitance, and the parameters of Н2О2 electrogeneration from О2 in aqueous sulfuric acid solutions at the current density of 150 mA/cm2 is described. It is shown that the effect of the PTFE concentration in composite materials on their characteristics depends on the properties of carbon materials. All carbon materials listed can be used in GDE for the reduction of О2 to Н2О2. For GDE with the optimal ratio of PTFE to the carbon material, the 5 h electrolysis produces the Н2О2 solution with the concentration of 1.9–2.4 М at 65–87% current efficiency.