Graphitic Carbon Structure Research Articles

Fe3+ stabilized 3D cross-linked glycine-melamine formaldehyde networks as precursor for highly efficient oxygen reduction catalyst in alkaline media

Development of inexpensive oxygen reduction electrocatalyst with high activity and durability is very important. Herein, iron carbide encapsulated pod-like graphitic carbon structures were prepared by simple pyrolysis involving Fe-glycine complex integrated melamine–formaldehyde resin precursor. The best catalyst among those studied, Fe-Gly 2 MF-C, possessing high degree of graphitization (ID/IG = 0.99) and enhanced specific surface area (205 m2/g) exhibited the highest ORR activity with a half-wave potential of 0.80 V in alkaline medium through the four-electron reduction pathway.

Preparation of activated carbon decorated with carbon dots and its electrochemical performance

Activated carbon decorated with carbon dots (ACD) was synthesized using an alkali activation process, in which metallic potassium expands the layer stacks and scissored turbostratic-structured carbon surface into nanosized particles. In addition, we demonstrated a capacitive effect in supercapacitors based on ACD, which has a high electrical conductivity because of the electronic pathway between the surface defects on activated carbon. The cyclic voltammogram curve was less distorted when the scan rate was increased to 100 mV s-1. Improved additional volumetric capacitance of up to 123.2 F cc-1 was achieved because the carbon dots provided additional capacitance resulting from intercalation into the graphitic carbon structure. The results obtained herein pave new ways for application of nanocarbons in energy storage.

Metal‐Organic Framework‐Templated Hollow Co3O4/C with Controllable Oxygen Vacancies for Efficient Oxygen Evolution Reaction

AbstractHydrogen production from water splitting is one of the effective methods to solve energy and environmental problems. However, the large overpotential of oxygen evolution reactions (OER) seriously impedes their development and application. Therefore, it is crucial to find a catalyst with low cost and high stability for OER. Herein, we report a simple method to fabricate a series of porous catalysts encapsulated with Co3O4 nanoparticles by carbonizing and then oxidizing MOF precursors, which can regulate and produce a large number of oxygen vacancies. The overpotentials of Z67‐Co3O4/C‐4 and Z9‐Co3O4/C‐4 are only 353 and 349 mV at a current density of 10 mA cm−2 with a small Tafel slope of 60 and 67 mV dec−1, respectively. These excellent properties can be attributed to the graphite carbon and unique hollow structure, as well as more water molecules adsorbed by oxygen vacancies, which effectively improve the conductivity and electron transfer and further promote OER activity. Thus, this preparation strategy can be applied to various MOF catalysts to regulate oxygen vacancies and thereby expanding their application in a wider range of fields.

Thermal Conversion Behavior of Medium–Low–Temperature Coal Tar Pitch During Liquid–Phase Carbonization Process

AbstractMedium–low temperature coal tar pitch (MLP) is a type of aromatic carbonaceous material obtained by the low temperature distillation of low rank coal, and is considered as a desirable raw material for the production of artificial carbon/graphite material. The thermal conversion behaviors of MLP during the liquid‐phase carbonization process were analyzed in detail in this study. Further, the changes of molecular structure and carbon microcrystalline structure of MLP and liquid‐phase carbonization products derived from it were quantitatively investigated by optical microscopy, fourier transform infrared spectroscopy, Raman spectroscopy, X‐ray diffraction, and curve‐fitting method. Results showed that both branched chain and the contents of C=O functional groups in the MLP played a key role in the reaction reactivity. Moreover, temperature of 450 °C was found to be a rapid changing temperature point on the enhancement of thermal conversion of MLP. The stacking height (Lc), parallel layers (N), average number of aromatic rings in each layer (n), ratio of ‘impurity’ structure (RI), ratio of amorphous carbon structure (RAC), ratio of graphite carbon structure (RGC), and ratio of defects graphite carbon structure (RDGC) exhibited a significant change with the improvement of liquid‐phase carbonization temperature.

Fe and N Codoped Mesoporous Carbon Nanofiber as a Nonprecious Metal Catalyst for Oxygen Reduction Reaction and a Durable Support for Pt Nanoparticles

Cost reduction and long-term durability are crucial issues for the commercialization of polymer electrolyte membrane fuel cells. To accomplish these goals, herein, we report an electrospun iron and nitrogen codoped mesoporous carbon nanofiber (Fe-N-MCNF) for use as both a low-cost nonprecious metal catalyst and a durable support of platinum nanoparticles. Silica nanoparticles and polyvinyl acetate are used together as porogens to create mesopores. As a synergetic effect of these two types of porogens, numerous mesopores are successfully formed inside of the carbon nanofibers. The highly mesoporous structure increases the specific surface area and improves the diffusion kinetics of the reactants, leading to an increase in the effective surface area of the Fe-N-MCNFs for electrochemical reactions. Therefore, the Fe-N-MCNFs can have high oxygen reduction reaction activity alone in an acidic solution and the ability to provide a large surface area for platinum nanoparticles as a support. The platinum nanoparticles on the Fe-N-MCNFs are highly stable under an oxidative potential condition of fuel cells due to the high corrosion resistance of the graphitized carbon structure. This work demonstrates that Fe-N-MCNF can be utilized as both a low-cost catalyst and a durable support in practical fuel cell applications.

Ag-doped graphitic carbon nitride photocatalyst with remarkably enhanced photocatalytic activity towards antibiotic in hospital wastewater under solar light

In this study a novel Ag-doped graphitic carbon nitride (g-C3N4) photocatalyst was synthesized and applied as high efficient material under solar light towards emerging antibiotic pollutant in hospital wastewater. The tetracycline (TC) was chosen as a target pollutant and the content of Ag doping at 3mmol revealed the highest photocatalytic degradation efficiency of TC (96.8%) after 120min under solar light irradiation. The photoluminescence and UV–vis analysis confirmed the enhancement of charge separation and transfer in the graphitic carbon structure after Ag-doping. The removal efficiency of TC using g-C3N4 and Ag-doped g-C3N4 (AgCN) under dark conditions was only 25.6 and 31.8%, respectively. While under solar light conditions, the removal efficiency of TC increased to 68.3 and 96.8% for g-C3N4 and AgCN, respectively. The reusability process showed that AgCN displayed extremely high stability after 6 cycles without significant drop in antibiotic degradation efficiency. The application of AgCN was tested for treatment of TC from hospital wastewater and it showed high removal efficiency of 89.6% within 120min reaction time. In addition, the intermediates generated and reduction of total organic carbon (TOC) during the photocatalytic reaction were detected to support information of possible TC removal mechanism.

Synthesis of carbon nanostructures from corn stalk using mechano-thermal method

Millions of tons of nuts are produced every year in the world (e.g. hazelnut shell, corn stalk, walnut shell) and these vegetal wastes create serious environmental problems. It is crucial that these wastes are converted into valuable products using simple and industrially applicable methods. The products obtained are widely used as adsorbents. Some studies utilizing these wastes as raw materials have obtained activated carbon using chemical methods, and employed this activated carbon as an adsorbent. In this study, a product containing carbon nanostructures was synthesized from corn stalk using mechno-thermal method. This product consists of many structures such as carbon nanotubes, carbon fibers, carbon nano-onion and amorphous carbon. We think that this synthesized product is an effective adsorbent. First, corn stalks were carbonized. The carbonized structure was milled for 20 h using a high-energy mill and the particle size was reduced to nano-scale. At the last stage of production, the milled sample was subjected to thermal treatment at 1400 °C. Analyses showed that the product is composed of graphitic carbon structures such as carbon nanotubes, nano-onion, and amorphous carbons. Very thin layers of graphite were also observed in some parts of the product. This study aimed to produce a structure containing carbon nanostructures from corn stalk and achieved this goal. Further research on the use of the product as an adsorbent is in progress.

Catalytic degradation of estrogen by persulfate activated with iron-doped graphitic biochar: Process variables effects and matrix effects

Advanced oxidation processes (AOPs) based on sulfate radicals (SO4∙-) is being actively investigated as an effective technology for aqueous organic pollutants degradation. In this work, a novel iron-doped graphitic biochar (Fe@GBC), which was synthesized by one-step method using biomass-derived biochar as precursor and potassium ferrate (K2FeO4) as activator, was applied to activate persulfate (PS) for the degradation of 17β-estradiol (E2). The characterizations indicated that Fe@GBC was successfully doped with iron particles and possessed a porous graphitic carbon structure. In order to evaluate the applicability of Fe@GBC, the effects of various reaction parameters, such as initial pH, catalyst dosage, PS concentration, as well as the reusability and stability of Fe@GBC were systematically investigated. With the synergistic effect of doped iron particles and porous graphitic carbon structure, Fe@GBC exhibited a high activity for PS activation and great degradation capacity to E2 (almost 100% degradation efficiency within 90 min). Through radical quenching experiments and electron spin resonance (ESR) analysis, it found that both SO4∙- and OH∙ were responsible for the degradation of E2, while SO4∙- played a dominant role. Moreover, Fe@GBC/PS also exhibited good degradation performance in complex water matrices. Overall, the facile one-step synthetic strategy and superior performance make Fe@GBC an alternative catalyst for persulfate activation and aqueous pollutants degradation.

Influencing factors of the explosion characteristics of modified coal used for blast furnace injection

An in-depth investigation and accurate analysis of the blast furnace injection fuel explosion characteristics is important since it is a crucial factor affecting ironmaking safety, cost reduction, and rational use of coal resources. This current study investigated explosion characteristics, morphology, pore distributions, and carbon structure of modified coal. The results showed that although the volatile matter content of modified coal was similar to the anthracite coal, the explosiveness of the modified coal was stronger than the high-volatile raw coal and the bituminous coal at various oxygen concentrations. The specific surface area of modified coal was 271.5 m2/g and pores were well developed. This provided good kinetic conditions for oxygen molecules to diffuse into the particle's surface and interior. The lower graphitized carbon structure of modified coal had high carbon reactivity, which improved the explosion performance. The strong explosiveness of the modified coal was not attributed to the cracking and the combustion of volatile matter. The ID/IG value (the intensity ratio of the D band and G band) was considered an important factor for evaluating the explosion characteristics of the samples.

Fluorescent carbon nanoparticles from laser-ablated Bougainvillea alba flower extract for bioimaging applications

The present study employed laser ablation to obtain fluorescent carbon nanoparticles (CNPs) using inexpensive and easily available Bougainvillea alba flower juice extract as the source. The laser ablation of flower juice extract was carried out using 355 nm wavelength of Nd: YAG pulsed laser for 60 min. HR-TEM studies showed the presence of both larger (about 60 nm) and smaller size (about 10 nm) CNPs and average particle size was found to be about 25 nm. Crystalline structure was also observed in CNPs, whose interplanar lattice spacing was 0.27 nm, indicating the contracted lattice spacing from usual graphitic structure. XRD and Raman analysis showed that the crystalline CNPs correspond to non-perfect graphitic carbon structure. Optical spectroscopic studies revealed the down-conversion of photoluminescence emission at 485 nm under the excitation wavelength of 400 nm. The average fluorescence lifetime of carbon nanoparticles was estimated as 1.1 ns from time-resolved spectroscopy. The CNPs were found to be non-toxic to human vein endothelial cells and internalized into the cells with high intensity up to 24 h. Two distinct PL emissions were observed with the large particles emitting at the longer wavelength localized predominantly in the cytosol and smaller particles emitting at the shorter wavelength concentrated on the nuclear membrane. The results suggest that the CNPs are biocompatible and have the potential for bioimaging applications.

Fabrication and Characterization of Highly Ordered Graphite Nanofiber Network Structure for Lithium-Sulfur Batteries

Graphitic carbon fiber felt (GCFF) with a highly ordered crystalline graphitic carbon structure was fabricated by a combination of electrospinning and graphitization (2800 °C heat treatment) of carbon precursor polymer (PAN; Polyacrylonitrile) and was used as an interlayer between the cathode and separator in Li-S batteries. This GCFF interlayer trapped the polysulfides on the cathode side and increased the utilization of sulfur by suppressing the shuttle phenomenon. Also, the GCFF was shown to be able to act as an upper current collector to reduce the charge-transfer resistance owing to the high crystallinity of the graphitic carbon fibers. The sulfur cathode with the GCFF interlayer showed a high specific initial discharge capacity of 1280 mAh g−1 and excellent cycling stability (1004 mAh g−1 after 100 cycles) at 0.2 C. Also, an image of the glass fiber (GF) separator on the anode side confirmed the presence of an SEI(solid-electrolyte interphase) after 200 cycles, which apparently resulted from stable Li deposition on the Li metal because of the low or medium concentration of sulfur in the electrolyte solution. Our observations should contribute to elucidating the key features of complex three-dimensional carbon fabrics with crystalline graphitic structures that allow them, when inserted as interlayers, to markedly improve the performance of rechargeable batteries. Reference: Journal of Power Sources, Volume 360, 31 August 2017, Pages 559-568

(Invited) Synthesis of Helical-CNT and Stacked Graphene-CNF Using a Copper Foil As Catalyst in a Chemical Vapor Deposition System

Helical carbon nanotubes (H-CNT) and stacked graphene carbon nanofibers (SG-CNF) were synthesized in an aerosol assisted chemical vapor deposition system (AACVD) using a copper foil as catalyst and substrate and ethanol vaporized as precursor. The copper foils were cleaned and pre-treated with ethanol, isopropanol and acetone in sonication bath during one hour each to obtain a slight surface modification. The AACVD was carried in one tubular furnace at 980 °C where several copper foils of 0.25 mm thickness and 4 cm x 1 cm area were placed inside the reactor from the highest to the coolest temperature zone. This carbon nanostructures were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction, Raman spectroscopy, atomic force microscopy (AFM) and cyclic voltammetry using a Calomel electrode in a KCl 0.5 M solution as electrolyte. A variety of carbon morphologies were found passing from the growing of graphite at the highest temperature to the formation of the H-CNT and SG-CNF at the temperature dropping zone (figure 1a-1f). Migration of sharp copper nanoparticles (10 nm – 200 nm) was observed as copper nanoparticles were found at the surface covered by carbon materials, while as we go out the furnace, faceted copper nanoparticles are partially covered of graphitic materials. A diminution of the Cu(200) crystalline plane of the copper foil as the temperature decreases is visible and the formation of copper oxide at the farthest position play a significant role in the growing of the carbon nanostructures. The H-CNT are helical structures with no practically gap between each coil with a pitch of ~27 nm by a tubular structure with ~20 graphitic layer in each wall (figure 1g-1i), in the case of the SG-CNF the graphitic layers are almost perpendicular to the CNT axis similar to a stacked short graphene layers directed outwards the structure that leds to the edge formation. Raman characterization illustrates differences between the graphitic carbon structures found at early stages from those at the dropping temperature zone where at the higher temperature mainly graphite the relation of the ID/IG bands is 0.88, while for the H-CNT and SG-CNF the ID/IG relation is 1.79 indicative of high defective graphitic structure which is related with the “herringbone structure” of the SG-CNF, in the case of the coolest zone the Raman spectra is characteristic of low sp3 amorphous carbon (ID/IG of 0.67). The cyclic voltammetry results indicates that the sample with the H-CNT and SG-CNF structures becomes more capacitive in a cuasi-reversible process with practically no modification of the standard oxide-reduction potential for Cu, while for the other sections this oxide-reduction potential increases. Another aspect of the sample with the H-CNT and SG-CNF is its hydrophobic surface with a contact angle of 122 °. With this work we demonstrate that a light surface modification of the copper foil and the temperature profile inside the furnace has a high influence in the formation of the H-CNT and the SG-CNF, also the shape of the copper nanoparticle influence the type of carbon nanostructure catalyzed over the copper substrate. This material could be a good for oxide-reduction reactions. Figure 1

Polyacrylonitrile/boron nitride nanotubes composite precursor and carbon fibers

Polyacrylonitrile (PAN)/boron nitride nanotubes (BNNTs) composite fibers were spun using gel spinning method and the resulting carbon fibers were processed after the fibers were stabilized in air and subsequently carbonized in nitrogen. PAN fibers containing 1 wt% BNNTs show comparable drawability to the control PAN fiber while the drawability of composite fibers significantly decreases as BNNT concentration increases from 1 to 5 wt%. Differential scanning calorimetry suggests that the presence of BNNTs reduces the activation energy of oxidation and crosslinking reactions but has little effect on the activation energy of cyclization reaction during stabilization. In the PAN/BNNTs based carbon fibers, the graphitic carbon structure that formed in the vicinity of BNNT was directly observed by transmission electron microscopy.

Laser-induced hierarchical carbon patterns on polyimide substrates for flexible urea sensors

Thermochemical decomposition of organic materials under heat-treatment in the absence of oxygen, known as the pyrolysis process, is often employed to convert micro and nano patterned polymers into carbon structures, which are subsequently used as device components. Pyrolysis is performed at ≥900 °C, which entails substrate materials with a high thermal stability that excludes flexible, polymeric substrates. We use optimized laser radiation to pattern graphitic carbon structures onto commercially available polyimide (Kapton) sheets in the micrometer to millimeter scale by inducing a localized, rapid pyrolysis, for the fabrication of flexible devices. Resulting laser carbon films are electrically conductive and exhibit a high-surface area with a hierarchical porosity distribution along their cross-section. The material is obtained using various combinations of laser parameters and pyrolysis environment (oxygen-containing and inert). Extensive characterization of laser carbon is performed to understand the correlation between the material properties and laser parameters, primarily fluence and power. A photothermal carbonization mechanism based on the plume formation is proposed. Further, laser carbon is used for the fabrication of enzymatic, pH-based urea sensors using two approaches: (i) direct urease enzyme immobilization onto carbon and (ii) electrodeposition of an intermediate chitosan layer prior to urease immobilization. This flexible sensor is tested for quantitative urea detection down to 10−4 M concentrations, while a qualitative, color-indicative test is performed on a folded sensor placed inside a tube to demonstrate its compatibility with catheters. Laser carbon is suitable for a variety of other flexible electronics and sensors, can be conveniently integrated with an external circuitry, heating elements, and with other microfabrication techniques such as fluidic platforms.

Role of polyvinylpyrrolidone in the electrochemical performance of Li2MnO3 cathode for lithium-ion batteries.

While Li2MnO3 as an over-lithiated layered oxide (OLO) shows a significantly high reversible capacity of 250 mA h g−1 in lithium-ion batteries (LIBs), it has critical issues of poor cycling performance and deteriorated high rate performance. In this study, modified OLO cathode materials for improved LIB performance were obtained by heating the as-prepared OLO at different temperatures (400, 500, and 600 °C) in the presence of polyvinylpyrrolidone (PVP) under an N2 atmosphere. Compared to the as-prepared OLO, the OLO sample heated at 500 °C with PVP exhibited a high initial discharge capacity of 206 mA h g−1 and high rate capability of 111 mA h g−1 at 100 mA g−1. The superior performance of the OLO sample heated at 500 °C with PVP is attributed to an improved electronic conductivity and Li+ ionic motion, resulting from the formation of the graphitic carbon structure and increased Mn3+ ratio during the decomposition of PVP.

Constructing Conductive Graphitic Structure on Hard Carbon as an Efficient Free-Standing Anode for Sodium-Ion Batteries

Hard carbon as a candidate anode for sodium-ion batteries, its rate capability is still a big challenge due to poor conductivity. In this work, conductive graphitic carbon structure was constructed on hard carbon (HC/NF-1, HC/NF-2, and HC/NF-3) by a simple hydrothermal and catalytic graphitization method, and used as a freestanding anode for sodium-ion batteries. The graphitic carbon consists of ∼84 graphitic layers. HC/NF-2 displays high reversible capacity (285.6 mAh·g−1 at 0.1 A·g−1), excellent rate capability (107.1 mAh·g−1 at 5.0 A·g−1), and long-term cycle performance (166.2 mAh·g−1 at 1.0 A·g−1 after 1000 cycles). The remarkable electrochemical performances of HC/NF-2 are mainly attributed to the construction of graphitic carbon, which significantly improves the conductivity of hard carbon and accelerates the migration of electrons. In addition, HC/NF-2 with a suitable thickness of solid-phase hard carbon provides more sodium storage sites and shortens the sodium ions diffusion pathway during discharge/charge cycles. Importantly, the macroporous Ni foam used as a current collector can effectively expand the contact area between the electrolyte and electrode. These results indicate this work can provide a reference for designing other composite carbon-based material for high-performance energy storage systems.

Structure and dynamics of water confined in nanoporous carbon

We study the structure and dynamics of water confined in a nanoporous graphitic carbon structure using molecular-dynamics (MD) simulations. The carbon structure is generated by a reactive MD simulation of oxidation of a silicon carbide nanoparticle. We embed water molecules in the nanopores and study structural and dynamical properties of nanoconfined water as a function of temperature. MD simulation results indicate the presence of high-density water (HDW) and low-density water. Radial distribution functions and spatial density functions indicate that the second solvation shell of the HDW is broken. We calculate the self-diffusion coefficient of confined water molecules as a function of temperature and find a significant decrease in the diffusion of water molecules around $T=190\phantom{\rule{0.16em}{0ex}}\mathrm{K}$. The cage correlation function $c(t)$ of confined water molecules at $T=200\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ exhibits stretched exponential decay, $c(t)=\mathrm{exp}[\ensuremath{-}{(\mathrm{t}/\ensuremath{\tau})}^{\ensuremath{\beta}}]$, with $\ensuremath{\beta}=0.43$, which matches exactly with the theoretical prediction $\ensuremath{\beta}=3/7$. Furthermore, the self-intermediate scattering function at $T=200\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ indicates differences in small-scale and large-scale dynamics of water molecules.

Roll‐to‐Roll Production of Graphitic Petals on Carbon Fiber Tow

A scalable roll‐to‐roll process is employed to produce graphitic petals. A 1‐meter sample of graphitic petals on carbon fiber tow is produced with a roll‐to‐roll radio‐frequency plasma chemical vapor deposition method. Microscale characterization reveals increasingly graphitic carbon structures with production time. Correspondingly, macroscale characterization shows enhanced functional performance with production time: decreasing electrical resistance and increasing capacitance. Using optical emission spectroscopy, important species in the plasma are studied and used to determine the plasma gas temperature. The results demonstrate that 1) successful cost‐driven production of graphitic petals is possible, 2) a plasma diagnostic technique is capable of real‐time process monitoring, and 3) meaningful material characterization methods are amenable to a production setting. Finally, valuable experiential learnings are shared to inform future equipment design and process development.

Transformation of carbon-encapsulated metallic Co into ultrafine Co/CoO nanoparticles exposed on N-doped graphitic carbon for high-performance rechargeable zinc-air battery

In this work, Co-MOFs microrod structures were firstly fabricated using Co2+ source and trimesic acid (H3BTC) as reaction precursors by a simple solvothermal method, followed by pyrolysis treatment at 900 °C in N2 atmosphere to obtain metallic Co encapsulated into graphitic carbon structure (Co@C) with an average Co particle size of 7.7 ± 0.2 nm excluding large-sized Co particles (>20 nm) and a surface area of 184 g cm−2. Interestingly, ultrafine Co/CoO nanoparticles with an average size of 1.8 ± 0.2 nm anchored on graphitic carbon surface (Co/CoO-C) can be obtained through further acid/alkali rinsing treatment of the as-prepared Co@C using HNO3 and NH3·H2O aqueous solutions respectively, followed by thermal treatment at 900 °C in N2 atmosphere. The formation of Co/CoO-C with a surface area of 247 g cm−2 can be ascribed to the dissolution and reorganization process of carbon-encapsulated metallic Co under acid/alkali rinsing and post-thermal-treatment conditions. As the electrocatalyst, Co/CoO-C exhibits superior bifunctional electrocatalytic activities of the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in alkaline media, notably better than ORR and OER activities of Co@C. The characterization results show that Co-Nx and N doping can be found in both Co@C and Co/CoO-C due to triethylamine (TEA) as solvent providing N source during Co-MOFs synthesis, which are catalytic active species toward electrocatalytic oxygen reactions. Furthermore, the highly exposed ultrafine Co/CoO on graphitic carbon surface can provide more catalytic active sites for high-performance ORR and OER, while carbon-encapsulated metallic Co in Co@C is incapable of directly contacting the electrolyte (only influencing shell-layer carbon function work) with limitedly improved electrocatalytic performance. The fabricated Co/CoO-C with superior bifunctional ORR and OER activities as air cathode material was assembled into a rechargeable zinc-air battery, exhibiting high power density and long-term stability. Our work provides an approach to transform low catalytic active electrocatalyst to high catalytic active one for renewable energy applications.

Structural Characterization of Loblolly Pine Derived Biochar by X-ray Diffraction and Electron Energy Loss Spectroscopy

Biochar from lignocellulosic biomass is emerging as a sustainable material with versatile applications, but its detailed properties are poorly understood because of its structural complexity. We propose a biochar structural development model based on experimental results including composition analysis, surface area and pore analysis, X-ray diffraction analysis, electron microscopy imaging, and electron energy loss spectroscopy. Loblolly pine derived biochars were produced at different carbonization temperatures between 300 to 1000 °C. Fixed carbon, sp2 content, and number of graphene layers increased with increased carbonization temperature. Alternating average C–C bond length, interlayer spacing distance, and layer coherence length were observed. Bulk plasmon excitation energy was correlated to the average C–C bond length, and it serves as a good indicator of the carbon structure development when compared to the perfect graphitic carbon structure. On the basis of the experimental results, four different ...