Carbon Letters 2021 KCI Impact Factor : 0.52

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2021, Vol.31, No.6

  • 1.

    Thermal reduction of graphite oxide in the presence of nitrogen-containing dyes

    Barkauskas Jurgis , Gaidukevič Justina , Niaura Gediminas | 2021, 31(6) | pp.1097~1110 | number of Cited : 0
    Abstract
    Thermal reduction of graphite oxide (GO) is considered as a prospective method for the preparation of high-performance graphene-based materials. However, this method has certain limitations, and the major is that this exothermic process is diffcult to control. In this research, we focused on the kinetic studies of the reduction of graphite oxide using non-isothermal diferential calorimetry (DSC) method. Six GO nanocomposites with dyes were tested to study the shift in kinetic parameters. The apparent reaction order is determined to be ca 0.7 for the thermal decomposition of pure GO, while in the presence of dye molecules it increases sometimes reaching a value of 2.0 for higher dye concentrations. Decisively, the thermal decomposition of pure GO can be presented as an intermediate between a zero- and frst-order reaction, while the introduction of dye molecules turns a certain part of the energy consumption via the bimolecular pathway. Our research revealed that the process of GO thermal decomposition can be operated and properties of the fnal product (reduced graphene oxide (rGO) and its derivatives) can be adjusted more precisely using additive molecules, which interact with GO sheets.
  • 2.

    Performance evaluation of Al6061-graphene nanocomposites surface engineered by a novel multiple microchannel reinforcement approach in friction stir processing

    Sharma Abhishek , Das Tanmoy , Paul Jinu | 2021, 31(6) | pp.1111~1124 | number of Cited : 0
    Abstract
    In this paper, the performance evaluation of Al-graphene nanoplatelets (GNP) composites surface engineered by a modifed friction stir processing (FSP) is reported. Here, multiple micro channels (MCRF) are used to incorporate GNPs in the aluminium matrix instead of a single large groove (SCRF) that is usually used in conventional FSP. With the MCRF approach,~18% higher peak temperature (compared to SCRF) was observed owing to the presence of aluminium sandwiched between consecutive microgrooves and higher heat accumulation in the stir zone. The MCRF approach have signifcantly reduced the coefcient of friction and wear rates of the processed composites by~14% and~57%, respectively as compared to the SCRF approach. The proposed reinforcement flling method signifcantly improves the particle dispersion in the matrix, which in turn changes the adhesion mode of wear in SCRF to abrasive mode in MCRF fabricated composites. The uniformly squeezed out GNP tribolayer prevented the direct metal to metal contact between composite and its counterpart which have efectively reduced the deterioration rates.
  • 3.

    A new insight into the structural modulation of graphene oxide upon chemical reduction probed by Raman spectroscopy and X-ray diffraction

    Chadha Neakanshika , Sharma Rahul , Saini Parveen | 2021, 31(6) | pp.1125~1131 | number of Cited : 0
    Abstract
    Lately, Raman spectroscopy has become powerful tool for quality assessment of graphene analogues with identifcation of intensity ratio of Raman active D-band and G-band (ID/IG ratio) as a vital parameter for quantifcation of defects. However, during chemical reduction of graphitic oxide (GrO) to reduced GrO (RGrO), the increased ID/IG ratio is often wrongly recognized as defect augmentation, with “formation of more numerous yet smaller size sp2 domains” as its explanation. Herein, by giving due attention to normalized peak height, full-width half-maxima and integrated peak area of Raman D- and G-bands, and compliment the fndings by XRD data, we have shown that in-plane size of sp2 domains actually increases upon chemical reduction. Particularly, contrary to increased ID/IG ratio, the calculated decrease in integrated peak area ratio (AD/AG ratio) in conjunction with narrowing of D-band and broadening of G-band, evinced the decrease in in-plane defects. Finally, as duly supported by reduction induced broadening of interlayer-spacing characteristic XRD peak and narrowing of~43° centered XRD hump, we have also shown that the sp2 domains actually expands in size and the observed increase in ID/IG ratio is indeed due to increase in across-plane defects, formed via along-the-layer slicing of graphitic domains.
  • 4.

    Biomass-derived porous activated carbon nanofibers from Sapindus trifoliatus nut shells for high-performance symmetric supercapacitor applications

    Vinayagam Murugan , Suresh Babu Rajendran , Sivasamy Arumugam and 1 other persons | 2021, 31(6) | pp.1133~1143 | number of Cited : 0
    Abstract
    Cost-efective and sustainable high-performance supercapacitor material was successfully prepared from cellulosic waste (Sapindus trifoliatus nut shells) biomass-derived activated carbon (CBAC) by physical activation method. The CBAC displays nanofber morphology, high specifc surface area (786 m2 /g), large pore volume (0.212 cm3 g−1) which are evaluated using FESEM, BET and possessed excellent electrochemical behavior analyzed through various electrochemical methods. Moreover, the assembled symmetric CBAC//CBAC device exhibits high specifc capacitance of 240.8 F g−1 with current density of 0.2 A g−1 and it is maintained to 65.6 F g−1 at high current density of 2.0 A g−1. In addition, the symmetric device delivers an excellent specifc energy maximum of over 30 Wh kg−1 at 400 W kg−1 of specifc power and excellent cycling stability in long term over 5000 cycles. The operation of the device was tested by light-emitting diode. Hence, CBAC-based materials pave way for developing large-scale, low-cost materials for energy storage device applications.
  • 5.

    Promising nature-based activated carbon derived from flowers of Borassus flabellifer for supercapacitor applications

    Iro Zaharaddeen S. , Subramani C. , Rajendran Jerome and 1 other persons | 2021, 31(6) | pp.1145~1153 | number of Cited : 0
    Abstract
    Recently, activated carbon derived from diferent agricultural by-products or bio-waste is receiving a great deal of attention due to its low or zero cost and environmental friendliness. In this work, fowers obtained from Borassus fabellifer (BFL) is used as a carbon source and potassium hydroxide (KOH) as activation precursor to produce activated carbon with high specifc surface area and predominant micropore. The obtained carbon material was activated at 650 °C. The as-prepared sample had a specifc surface area of 930.3 m2 /g and pore size distribution of 1.96 nm. The carbon material exhibited high electrochemical performance with a specifc capacitance of 247 F/g at 0.5 A/g in 1 M H2SO4 electrolyte and an excellent cycling stability of 94% after 2500 cycles. A specifc energy of 101.1 Wh/kg and a specifc power of 4500 kW/kg were obtained. Based on the electrochemical properties exhibited by BFL, it could be used as an excellent electrode material for supercapacitor applications.
  • 6.

    Synthesis of γ-carboline derivatives via indole-2,3-dienolate

    Alugubelli Gopi Reddy , Musunuri Sivanadh , Sreenivasulu Reddymasu and 1 other persons | 2021, 31(6) | pp.1155~1161 | number of Cited : 0
    Abstract
    Anion assisted [4+2] cycloaddition reaction via indolo[2,3]-dienolate by reacting 1,2-dimethylindole-3-carboxaldehyde with aromatic nitriles using lithium diisopropylamide in terahydrofuran, a facile and convenient regiospecifc route designed and developed for the synthesis of γ-carbolines.
  • 7.

    Effective removal of arsenide from aqueous solutions using mesoporous CoFe2O4/graphene oxide nanocomposites assisted by artificial intelligence

    Wu Xianliang , Hu Jiwei , Wang Xingfu and 3 other persons | 2021, 31(6) | pp.1163~1178 | number of Cited : 0
    Abstract
    This study investigated the arsenide removal by using mesoporous CoFe2O4/graphene oxide nanocomposites based on batch experiments optimized by artifcial intelligence tools. These nanocomposites were prepared by immobilizing cobalt ferrite on graphene oxide and then characterized using various techniques, including small angle X-ray difraction, high-resolution transmission electron microscopy and energy-dispersive X-ray spectroscopy. Artifcial intelligence tools associated with response surface methodology were employed to optimize the conditions of the arsenide removal process. The results showed that back propagation neural network combined with genetic algorithm was suitable for the arsenide removal from aqueous solutions by the nanocomposites based on the minimum average values of absolute errors and the value of R2 . The optimal values of the four variables (operating temperature, initial pH, initial arsenide concentration, and contact time) were found to be 25.66 °C, 7.58, 10.78 mg/L and 46.41 min, and the predicted arsenide removal percentage was 84.78%. The verifcation experiment showed that the arsenide removal percentage was 86.62%, which was close to the predicted value. Three evaluation methods (gradient boosted regression trees, Garson method and analysis of variance) all demonstrated that the temperature was the most important explanatory variable for the arsenide removal. In addition, the arsenide removal process can be depicted with pseudo-second-order kinetics model and Langmuir isotherm, respectively. The thermodynamics investigation disclosed that the adsorption process was of a spontaneously endothermic nature. In summary, this study showed that ANN-GA was an efcient and feasible method in determining the optimum conditions for arsenic removal by CoFe2O4/graphene oxide nanocomposites.
  • 8.

    Study of the ageing mechanisms of activated carbon supercapacitors by electrothermal simulation and experimental analysis

    Erradi Amine , Touhtouh Samira , El Ballouti Abdessamad and 1 other persons | 2021, 31(6) | pp.1179~1189 | number of Cited : 0
    Abstract
    In view of the growing need for clean energy, supercapacitors (SC), especially those based on activated carbon (AC) and organic electrolyte are attracting great attention for their theoretically infnite life span. However, they still age much faster than expected due to certain mechanisms. Several researches is being conducted to understand these mechanisms, but so far, the chemical reactions at the phase boundary of the activated carbon electrodes and organic electrolyte have been very unclear. Some pathways have not yet been investigated; there is no research on the reactions that can take place between acetonitrile in the vapor phase and the oxides presented on the surface of activated carbons. For this reason, in this study, divided into two parts, the frst based on a thermal simulation and the second based on an experimental study, we have systematically described the ageing mechanisms by determining the gas-phase reactions that can occur at the electrode–electrolyte interface. On the one hand, a thermal model of a supercapacitor cell using activated carbon and organic electrolyte technology has been developed. This model allowed us to study the temperature distribution of supercapacitors, and thus to determine the thermodynamic parameters related to the phenomena produced at the electrode–electrolyte interface. On the other hand, a thermo-gravimetric analysis coupled with gas phase infrared spectroscopy on the activated carbons of an aged supercapacitor of the same technology as that used in the simulation was carried out. The results obtained made it possible to identify the chemical groups produced by ageing.
  • 9.

    Raw and pyrolyzed (with and without melamine) graphene nanoplatelets with different surface areas as PEM fuel cell catalyst supports

    Öztürk Ayşenur , Bayrakçeken Yurtcan Ayşe | 2021, 31(6) | pp.1191~1214 | number of Cited : 0
    Abstract
    Platinum (Pt) catalysts dispersed on carbon-based support materials are generally used in the polymer electrolyte membrane (PEM) fuel cells. In this study, commercial graphene nanoplatelets (GNPs), with diferent surface areas (320, 530, 800 m2 g−1), were used as catalyst supports in PEM fuel cells. These GNPs were also pyrolyzed under the inert atmosphere, with and without melamine, as the nitrogen (N) source. Various characterizations (Elemental analysis, FTIR, Raman spectroscopy, BET, TEM, HRTEM, SAED, XRD, TGA, ICP-MS, contact angle measurement, CV, ORR, chronoamperometry, EIS, PEM fuel cell performance test) were performed for the detailed analysis of Pt/GNPs. Based on the three-electrode cell system, the lowest electrochemical surface area (ECSA) loss (29.9%), Pt mass activity loss (20.3%) and overall (charge and mass) resistance (42.2 Ω) were obtained with the Pt/M-530 catalyst. According to the in-situ PEM fuel cell performance results, the specifc peak power density was recorded as (450 mW mg Pt−1) for the Pt/R-530 catalyst, which has also the second most hydrophobic catalyst layer surface with the 146.5°±1.28° contact angle value. On the heels of Pt/R-530, the two best performances also belong to the Pt/M-530 (391 mW mg Pt−1) and Pt/P-530 (378 mW mg Pt−1) catalysts of the same group.
  • 10.

    Cost effective biosynthetic approach for graphene exhibiting superior sonochemical dye removal capacity

    Akhil Syed , Saeed Al Musawi Mahdi Jawad , Majety Syam Sundar and 6 other persons | 2021, 31(6) | pp.1215~1225 | number of Cited : 0
    Abstract
    Green synthesis of graphene using leaf extracts as sustainable reducing and capping agents is a thrust area of research owing to its simplicity, eco-friendly nature and the ease of access to graphene. Moringa (Moringa oleifera Lam) plant is widely cultivated in India owing to its important medicinal and nutritional values. Inspired by these reports, herein we report a simple, green and economic synthesis of graphene, Moringa leaf extract employed reduced graphene oxide (MRGO) with excellent dye removal efciencies. The MRGO is prepared by refuxing a mixture of aqueous dispersion of graphene oxide and Moringa leaf extract for 10 h. Further, we elucidated the role of synthesized MRGO in the removal of methylene blue (MB) and rhodamine B (RB) dyes through the sonochemical method. This as-synthesized material exhibited excellent dye removal efciencies of about 93% and 87% against MB and RB dyes, respectively. Graphene with huge surface area expedited the better adsorption of dye molecules, thus, facilitated the better removal of the latter. Therefore, the superior dye removal efciencies of MRGO were attributed to its adsorption capacity. This cost-efective synthetic approach of MRGO nanomaterial has a great potential for the innovative applications in water purifcation technology and fnd its place in further industrialization.
  • 11.

    Predicting an ideal 2D carbon nanostructure with negative Poisson's ratio from first principles: implications for nanomechanical devices

    Yuan Kun , Zhao Yaoxiao , Li Mengyang and 1 other persons | 2021, 31(6) | pp.1227~1235 | number of Cited : 0
    Abstract
    The intrinsic negative Poisson’s ratio efect at the level of molecule in two-dimensional nanomaterials, especially in the perfect planar nanostructures with a single atom thickness, is really rare and has attracted a lot of research interests because of its unique mechanical properties in the nanoscale and extensive applications in mechanical nanodevices. In this work, a novel ideal planar carbon nanostructure (PCNS) framework with a single atom thickness composed by carbon and hydrogen atoms is proposed and studied by means of frst-principles density functional calculation. The results showed that the PCNS is, simultaneously, of excellent thermodynamic, molecular dynamic and mechanical stabilities. In addition, the electronic structure, mechanical characters, and optical-electronic characteristics of PCNS are also explored. Excitedly, it is found that the PCNS has a signifcant negative Poisson’s ratio efect in plane, and the maximum value of Poisson’s ratio is as high as − 2.094. Meanwhile, the material has a wide range of elastic mechanics. Moreover, the PCNS presents an ideal UV absorption performance. It is hoped that this work could be a useful structural design strategy for the development of the ideal 2D carbon-based nanomechanical devices with the intrinsic negative Poisson’s ratio efect and other electronic functions.
  • 12.

    An investigation on development of a molecular imprinted sensor with graphitic carbon nitride (g-C3N4) quantum dots for detection of acetaminophen

    Medetalibeyoğlu Hilal | 2021, 31(6) | pp.1237~1248 | number of Cited : 0
    Abstract
    In the present study, a novel electrochemical sensor for acetaminophen (AMP) which included quantum graphitic carbon nitride dots, g-C3N4QDs, was designed and conducted with molecular imprinted polymer (MIP). First, bulk g-C3N4 was generated with direct thermal polycondensation of melamine. After the treatment of the acidic solution containing H2SO4: HNO3 (1:1, v:v), the heating treatment at 200 °C on the dispersion provided g-C3N4QDs. In this respect, for nanomaterial characterization, some spectroscopic approaches were performed including Fourier-transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) as well as electroanalytical methods such as electrochemical impedance (EIS) and cyclic voltammetry (CV). In accordance with the aims of the study, AMP imprinted electrode was formed after high electrocatalytic performance and linear range of 1.0× 10–11–2.0× 10–8 M and the LODs of 2.0× 10–12 was achieved. Eventually, an AMP-printed sensor was also used for AMP identifcation in pharmaceutical samples.
  • 13.

    Nitrogen-doped and hierarchically porous carbon derived from spent coffee ground for efficient adsorption of organic dyes

    Dai Zhong , Ren Peng-Gang , Zhang Hua and 2 other persons | 2021, 31(6) | pp.1249~1260 | number of Cited : 0
    Abstract
    Here, a novel nitrogen-doped carbon nano-material (N-CGNM) with hierarchically porous structure was prepared from spent cofee ground for efcient adsorption of organic dyes by a simple one-step carbonization process (the uniform mixture consists of spent cofee ground, urea, and CaCl2 with the ratio of 1:1:1, which was heated to 1000 °C with a rate of 10 °C min−1 and held at 1000 °C for 90 min in N2 atmosphere to carry out carbonization, activation, and N-doping concurrently). The morphology and structure analysis show that the prepared N-CGNM exhibits hierarchical pore structure, high specifc surface area (544 m2 /g), and large numbers of positively charged nitrogen-containing groups. This unique structure and chemical composition endow N-CGNM with an excellent adsorption capacity toward anion Congo red (623.12±21.69 mg/g), which is obviously superior to that (216.47±18.43 mg/g) of untreated spent cofee ground-based carbon nano-materials (CGM). Oppositely, the adsorption capacity of N-CGNM towards cation methylene blue is inferior to that of CGM due to the existence of electrostatic repulsion. These fndings show a great guidance for the development of low-cost but efcient selective adsorbent.
  • 14.

    CO2 capture using activated carbon synthesized from date stone: breakthrough, equilibrium, and mass-transfer zone

    Danish Mohd , Parthasarthy Vijay , Al Mesfer Mohammed K. | 2021, 31(6) | pp.1261~1272 | number of Cited : 0
    Abstract
    Global warming and climate changes are the ultimate consequences of increased CO2 volume in the air. Physical activation was used to prepare high-throughput activated carbon from a low-cost date stone. The adsorption performance of activated carbon using fxed bed for CO2 separation was studied. The reliance of temperature, fow rate, and initial CO2 concentration levels on breakthrough behaviour was analysed. The adsorption response was explored in terms of breakthrough and saturation points, adsorption capacity, temperature profles, utilization factor, and length of mass-transfer zone. Increased temperatures lead to vary the breakthrough periods notably. The vastly steep breakthrough curves reveal satisfactory utilization of bed capacity. LMTZ is varied positively with increased feed rates and temperatures. The high utilization factor of 0.9738 with 1.66 mmol/g CO2 uptake was acquired at 298 K and 0.25 bars. The fndings recommend that the carbon prepared from date stone is encouraging to capture CO2 from CO2/N2 mixture.
  • 15.

    Facile synthesis of silver nanoparticle-decorated zinc oxide nanocomposite-based pencil graphite electrode for selective electrochemical determination of nitrite

    Salagare Shridevi , Adarakatti Prashanth S. , Yarradoddappa Venkataramanappa | 2021, 31(6) | pp.1273~1286 | number of Cited : 0
    Abstract
    This work describes the facile synthesis of silver nanoparticle-decorated zinc oxide nanocomposite through a simple glycol reduction method. The silver nanoparticle-decorated zinc oxide nanocomposite-based pencil graphite electrode has been validated as a perceptive electrochemical sensing podium towards nitrite. The morphology of the prepared nanocomposite has been characterized via specifc spectroscopic and electrochemical techniques. The sensor exhibits a notable enhancement in the cyclic voltammetric response to nitrite oxidation at an ideal peak potential of 0.76 V in pH 6.0 acetate bufer. Under optimum conditions of nitrite directly expanded with their concentration in the range from 30 to 1400 μM with a detection limit of 14 μM.
  • 16.

    Effect of solvent exchange on the properties of carbon xerogel and carbon xerogel/polypyrrole composites for supercapacitors

    Samancı Meryem , Daş Elif , Yurtcan Ayşe Bayrakçeken | 2021, 31(6) | pp.1287~1308 | number of Cited : 0
    Abstract
    Carbon xerogels (CXs) with three-dimensional (3D) structure, unusual surface, physical, electrical and mechanical properties and their electrically conductive polymer polypyrrole (PPy) composites were synthesized as electrode materials for supercapacitors. The efect of diferent resorcinol/formaldehyde (R/C) ratios, whether solvent exchange with or without acetone and polypyrrole addition on the physicochemical (FTIR, XRD, BET, SEM and TGA) and electrochemical properties (CV, 1000 cycles) of the synthesized materials were investigated. It was observed that the R/C ratio and the solvent exchange process prior to drying afect the specifc surface areas and the pore size distributions, thereby positively afecting the specifc capacitance. PPy flm thickness was observed to be efective in the specifc capacitance of the electrode in PPy composite synthesis. Among the synthesized materials, the highest specifc capacitance values belong to polypyrrole/carbon xerogel composites. As a result of the analysis and calculations, it was found that the highest specifc capacitance belongs to CX2/PPy composite with 599 Fg−1 at 5 mVs−1. CX2/PPy composite has been found to have a capacitance retention rate of 80.30% at the end of 1000 cycles.
  • 17.

    Heteroatom-doped mesoporous carbon prepared from a covalent organic framework/α-MnO2 composite for high-performance supercapacitor

    Vargheese Stella , Pattappan Dhanaprabhu , Kavya K. V. and 3 other persons | 2021, 31(6) | pp.1309~1316 | number of Cited : 0
    Abstract
    In this report, we successfully prepared nitrogen-doped porous carbon (N-PC)/manganese dioxide (MnO2) composite for a high-performance supercapacitor. X-ray difraction data revealed the α-MnO2 phase. Transmission electron microscopy confrmed that the nanostructured α-MnO2 nanoparticles were coated on the surface of N-PC. The N-PC/α-MnO2 composite delivered a capacitance of 525.7 F g−1 at the charging current of 1.0 A g−1. The higher capacitance of the composite could be owing to the synergy of MnO2 and N-PC. Besides, the electrode exhibited a 14.7% capacitance loss after 6000 charge– discharge cycles at 10 A g−1 indicating good electrochemical stability.
  • 18.

    Analysis of pore formation and development in carbon blacks activated in a CO2 gas atmosphere through microstructural observation

    Lee Sang-Min , Lee Sang-Hye , Kim Suk Hwan and 1 other persons | 2021, 31(6) | pp.1317~1326 | number of Cited : 0
    Abstract
    The present study analyzed the pore formation and development process in carbon black that was activated by CO2 gas and the efect of the burn-of (BO) ratio on the process, particularly based on changes in the surface shape and internal microstructure. The activation process was performed as follows. Carbon blacks were injected into a horizontal tube furnace when the inside temperature reached 1000 °C. Carbon black samples with diferent BOs, i.e., 7.2%, 15.4%, 30.4%, 48.2%, 59.9%, and 83.2%, were prepared by varying the activation time. The microstructure of the activated samples was observed and examined using SEM and TEM. The results showed that pore passages were frst created on the surface of the primary particles of the carbon black, and then the inner portion of the carbon black with a lower degree of crystallinity started to be activated, thereby causing inner pores to be formed. These inner pores then started to grow and coalesce into larger pores, thereby causing the crystallite layers in the inner portion of the carbon black to be activated. The changes in the microstructure of the carbon black during the activation reaction were attributable to the carbon black manufacturing process, in which the nucleation and growth of the primary particles of the carbon black occurred within a very short period of time. Thus, the crystallization of the inner portion was suppressed, and therefore, the degree of crystallinity was lower in the inner portion than in the outer portion.
  • 19.

    Evaluation of carbon nanotubes dispersion in aqueous solution with various dispersing agents

    Kim Youn , Hong Ji Soo , Moon Su Young and 2 other persons | 2021, 31(6) | pp.1327~1337 | number of Cited : 0
    Abstract
    In order to extend the business viability of carbon nanotubes (CNTs), research on CNT dispersion in a solvent as well as in polymer matrix should be established. Herein, three kinds of dispersing agents, sodium deoxycholate (DOC), sodium dodecylbenzene sulfonate (NaDDBS), polyvinyl pyrrolidone (PVP), are selected and applied to quantify the dispersibility and dispersion stability of CNT aqueous dispersion. The dispersibility of CNT dispersion with the PVP, evaluated via viscosity and particle size analyses, are superior to those with the DOC and NaDDBS dispersing agents. CNT aqueous solution dispersed with PVP showed slightly higher viscosity and narrower particle size distribution than those with DOC and NaDDBS dispersing agents. In addition, the dispersion stability of CNT dispersion with the PVP, measured via lumisizer analyses, are superior to those with the DOC and NaDDBS dispersing agents. HR-TEM analysis verifes that the outstanding dispersibility and dispersion stability of CNTs in aqueous solution are due to the efect of the robust polymer wrapping of the PVP dispersing agent on the CNT surface. From the results of this study, the guidelines for the selection of the suitable dispersing agents and the systematic evaluation of dispersibility and dispersion stability of CNT dispersions can be suggested.
  • 20.

    Fabrication of nitrogen-doped porous carbon nanofibers for heavy metal ions removal

    Bae Joonwon , Hong Jin-Yong | 2021, 31(6) | pp.1339~1347 | number of Cited : 0
    Abstract
    In this article, nitrogen (N) doped porous carbon nanofbers (N-PCNF) were prepared by carbonization of polymer-silica nanocomposite precursor, and its application for heavy metal ion removal was demonstrated. Carbon–silica composite nanofbers were obtained by carbonization of electrospun polyacrylonitrile (PAN)-silica nanofber composites. Subsequent selective etching of silica porogen produced porous carbon nanofbers (PCNF). It was revealed by surface characterization with X-ray photoelectron spectroscopy (XPS) that the surface of the PCNF was nitrogen-doped because N atom from cyanide group in PAN chains remained in the hexagonal carbon structure. The use of the obtained N-PCNF for heavy metal ion (Hg2+) removal was demonstrated using a simple adsorption test apparatus and 5, 10, 15, 20-tetraphenylporphine tetrasulfonic acid (TPPS) as an indicator. The N-PCNF showed a removal efciency of 96 and 99% in 10 and 120 min, respectively, indicating a maximum heavy metal ion adsorption capacity at pH 7.0. In addition, heavy metal ion adsorption behavior was also analyzed using common adsorption isotherms. This article provides important information for future research activities regarding control over hazardous substances.
  • 21.

    Size effect of metal–organic frameworks with iron single-atom catalysts on oxygen–reduction reactions

    Lee Seon Yeong , Jang Han Wool , Lee Hae Ri and 1 other persons | 2021, 31(6) | pp.1349~1355 | number of Cited : 0
    Abstract
    Metal–organic frameworks (MOFs) are widely used as supports for single-atom catalysts (SACs) owing to their high specifc surface area, porosity, and ordered metal–ligand structure. Their activity can be increased by increasing the number of electrochemically accessible active sites via the formation of atomically dispersed metal catalysts (M–Nx) that coordinate with nitrogen atoms on the MOF. Herein, we introduce the relationship between the size of the MOF as a starting material and the catalytic activity for the oxygen reduction reaction in alkaline media. The morphology and features of the MOFs are critically dependent on their size. Remarkably, cage-like MOFs below 33 nm are converted into collapsed structures and are connected between each MOF, even carbon fber- or tube-like features, after carbonization. SACs derived from medium-sized MOFs exhibit excellent activity and are comparable to commercial Pt/C catalysts owing to their porous structure. Therefore, we believed that controlling the size of MOFs containing active atoms is an efective method of modulating the morphological properties of the support and even the number of active sites that are closely related to the activity.
  • 22.

    Effect of kneading and carbonization temperature on the structure of the carbon block for thermally conductive bulk graphites

    An Donghae , Kim Kyung Hoon , Lim Chaehun and 1 other persons | 2021, 31(6) | pp.1357~1364 | number of Cited : 0
    Abstract
    Artifcial graphites have been used in various applications, for example, as anode materials for Li-ion batteries, C/C composites, and electrodes for aluminum smelting, due to their unique mechanical strength and high thermal and electrical conductivity. Artifcial graphites can be manufactured by a series of kneading, molding, carbonization and graphitization processes with an additional impregnation process. In this study, the infuence of the process variables in the kneading and carbonization/graphitization process on the properties of the resulting carbon block was systemically investigated. During the kneading process, the optimum kneading temperature was 90 °C higher than the softening point of the binder pitch; thus, the binder pitch reached its maximum fuidity. On the other hand, during the carbonization and graphitization process, the structural properties of carbon blocks prepared at diferent heat treatment temperatures were examined and their structural change and evolution were closely described according to the temperature and divided into low-temperature carbonization and high-temperature carbonization/graphitization. Based on this study, we expect to provide a better understanding of setting the parameters for thermally conductive carbon block manufacturing.
  • 23.

  • 24.

    Discussion on “Nonlinear buckling analysis of double-layered graphene nanoribbons based on molecular mechanics” by Namnabat et al. Carbon Letters, https://doi.org/10.1007/s42823-020-00194-2

    Korobeynikov S. N. | 2021, 31(6) | pp.1365~1366 | number of Cited : 0
    Abstract
    Namnabat et al. (cf., [Carbon Letters, https://doi.org/10.1007/s42823-020-00194-2]) employ the classical approach of Li and Chou (cf., [Int J Solids Struct 40: 2487–2499]) to the implementation of the molecular structural mechanics method using the Bernoulli–Euler beam elements for nonlinear buckling analysis of double-layered graphene nanoribbons. However, more recent studies by Eberhardt and Wallmersperger (cf., [Carbon 95: 166–180]) and others (see, e.g., [Int J Eng Sci 133: 109–131]) have shown that the classical approach of Li and Chou poorly reproduces both in-plane and out-of-plane mechanical moduli of graphene. We have shown that the 2D beam-based hexagonal material used by Namnabat et al. poorly simulates the mechanical moduli of graphene, especially the bending rigidity modulus, and this material cannot be used for the buckling simulation of graphene sheets (or nanoribbons). In addition, it is noted that in Int J Eng Sci 133: 109–131, a modifcation of the classical approach of Li and Chou is given which exactly reproduces both in-plane (2D Young’s modulus and Poisson’s ratio) and out-of-plane (bending rigidity modulus) mechanical moduli of graphene using beam elements.