Graphitized Carbon Fibers Research Articles

Enabling highly concentrated tetracycline degradation with tailored FeCo nanocrystals in porous graphitic carbon fiber

Enabling highly concentrated tetracycline degradation with tailored FeCo nanocrystals in porous graphitic carbon fiber

Indole-3-Carbinol Upconversion with Copper Oxide Nanoparticles Supported Graphitic Carbon Nitride: A Sustainable Approach

Electro-organic chemistry offers a sustainable and efficient approach to organic synthesis by utilizing electrochemical processes. This field has gained significant attention due to its potential for minimizing waste, reducing energy consumption, and enabling selective transformations. Herein, we report the development of a graphitic carbon nitride-coated carbon fiber electrode modified with electropolymerized amino-2-thiazole and electrodeposited Cu2O nanoparticles from copper nitrate trihydrate for the oxidation of Indole-3-carbinol (IC). Scanning electron microscopy, X-ray diffraction analysis, and X-ray photoelectron spectroscopy studies were carried out to characterize the developed electrode. Cyclic voltammetry, electrochemical impedance spectroscopy, and bulk electrolysis techniques were employed for the electrochemical studies. The enhanced electrochemical activity of the Cu2O-pAT-GCN-TCFP electrode compared to the individual GCN and polymer electrode was studied using electrochemical characterization, which revealed a 3-fold increase in the current response for Cu2O-pAT-GCN-TCFP (0.0011 A) compared to the bare electrode. The reaction was carried out using an aqueous carbonate buffer solution as an electrolyte via bulk electrolysis at a set potential of 0.82 V. The product obtained was isolated by column chromatography to obtain a yield of 74% and characterized by proton nuclear magnetic resonance (1H NMR) spectroscopy. Additionally, the Cu2O-pAT-GCN-TCFP electrode was studied for its stability, reproducibility, and selectivity.

A Dual-Carbon Potassium-Ion Capacitor Enabled by Hollow Carbon Fibrous Electrodes with Reduced Graphitization.

The large size of K+ ions (1.38 Å) sets a challenge in achieving high kinetics and long lifespan of potassium storage devices. Here, a fibrous ZrO2 membrane is utilized as a reactive template to construct a dual-carbon K-ion capacitor. Unlike graphite, ZrO2-catalyzed graphitic carbon presents a relatively disordered layer arrangement with an expanded interlayer spacing of 0.378nm to accommodate K+ insertion/extraction. Pyridine-derived nitrogen sites can locally store K-ions without disrupting the formation of stage-1 graphite intercalation compounds (GICs). Consequently, N-doped hollow graphitic carbon fiber achieves a K+-storage capacity (primarily below 1V), which is 1.5 time that of commercial graphite. Potassium-ion hybrid capacitors are assembled using the hollow carbon fiber electrodes and the ZrO2 nanofiber membrane as the separator. The capacitor exhibits a high power of 40 000 W kg-1, full charge in 8.5 s, 93% capacity retention after 5000 cycles at 2 A g-1, and a low self-discharge rate of 8.6mV h-1. The scalability and high performance of the lattice-expanded tubular carbon electrodes underscores may advance the practical potassium-ion capacitors.

PbO2 /graphite and graphene/carbon fiber as an electrochemical cell for oxidation of organic contaminants in refinery wastewater by electrofenton process; electrodes preparation, characterization and performance

The electro-Fenton oxidation process was used to treat organic pollutants in industrial wastewater as it is one of the most efficient advanced oxidation processes. The novel cell in this process consists of a prepared PbO2 electrode by electrodeposition on graphite substrate and carbon fiber modified with graphene as a cathode. X-ray diffraction, fluorescence, analysis system, atomic force microscopy, and scan electron microscopy were used to characterize the prepared anode and cathode. XRD patterns clearly show the characteristic reflection of the mixture of  - and β phases of PbO2 on graphite and carbon fiber, and AFM results for cathode and anode present that PbO2 on graphite substrate and graphene on carbon fiber surface are on a nanoscale. Contact angle measurement was determined for the carbon fiber cathode before and after modification. The anodic polarization curve showed a higher anodic current when utilizing the PbO2 anode than the graphite anode. Phenol in simulated wastewater was removed by electro-Fenton oxidation at 8 mA/cm2 current density, 0.4 mM of ferrous ion concentration at 35 °C up to 6 h of electrolysis. Chemical oxygen demand for the treated solution was removed by 94.02 % using the cell consisting of modified anode and cathode compared with 81.23% using modified anode and unmodified cathode and 79.87 % when using unmodified anode and modified cathode.

Study on electrochemical lithiation stress model of graphite-carbon fiber bilayer electrode

Graphite–carbon fiber bilayer electrodes (GCBEs), as part of composite structural batteries, are capable of both energy storage and load bearing without the requirement of an extra structure. However, carbon fiber (CF) as a current collector exists lithiation stress, the stress of this bilayer electrode structure is still unclear. In this study, the relationship between the potential and deflection deformation of GCBEs at various thickness ratios is experimentally recorded using an in situ electrochemical cell device. The GCBE bends and recovers with a decrease and increase in potential, respectively. In addition, a cantilever stress model is established to depict the effect of the Li+ concentration difference and thickness ratio on the GCBE lithiation deflection and stress distribution. The results show that the concentration difference and thickness ratio are positively correlated with the deflection and stress, and the stress is discontinuous at the interlayer interface of the electrode. Finite element simulation shows that the Li+ concentration in the graphite layer is approximately three times more than CFs. Compared to the commercial graphite-copper bilayer electrode, the GCBE is experimentally proven to better suppress lithiation deformation. Meanwhile, the influence of solid electrolyte interphase (SEI) is considered by a simplified strain transfer model.

Demystifying the Influence of Precursor Structure on S‐Doped Hard Carbon Anode: Taking Glucose, Carbon Dots, and Carbon Fibers as Examples

AbstractHeteroatom doping is a promising strategy for adjusting the microstructure of hard carbon (HC) to promote its electrochemical sodium storage performance. However, clarifying the doping sites of heteroatoms and effectively regulating their doping levels remain serious challenges. Herein, this work reveals the impact of three distinct structural precursors on S‐doped hard carbon: namely glucose (small organic molecule), carbon dots (CDs, intermediate state between organic and inorganic), and graphitized carbon fibers (inorganic carbon materials). It is demonstrated that the S‐doped HC derived from CDs possesses a more significant number of C─S bonds within its carbon framework, which is attributed to the preferential bonding between sulfur and short polymeric chains abundant in unsaturated functional groups. And these chains cluster prominently on the surface of CDs, enhancing the affinity of sulfur. Furthermore, as a prominent feature of CDs, the extremely small size inherently distinguishes them from other precursors, enabling them to serve as fundamental units for constructing various carbon microstructures, such as three‐dimensional (3D) structure. In summary, this study explores the influence of different precursor structures on heteroatom doping, with CDs identified as the most useful precursor.

Carbon Fiber Film with Multi-Hollow Channels to Expedite Oxygen Electrocatalytic Reaction Kinetics for Flexible Zn-Air Battery.

The high oxygen electrocatalytic overpotential of flexible cathodes due to sluggish reaction kinetics result in low energy conversion efficiency of wearable zinc-air batteries (ZABs). Herein, lignin, as a 3D flexible carbon-rich macromolecule, is employed for partial replacement of polyacrylonitrile and constructing flexible freestanding air electrodes (FFAEs) with large amount of mesopores and multi-hollow channels via electrospinning combined with annealing strategy. The presence of lignin with disordered structure decreases the graphitization of carbon fibers, increases the structural defects, and optimizes the pore structure, facilitating the enhancement of electron-transfer kinetics. This unique structure effectively improves the accessibility of graphitic-N/pyridinic-N with oxygen reduction reaction (ORR) activity and pyridinic-N with oxygen evolution reaction (OER) activity for FFAEs, accelerating the mass transfer process of oxygen-active species. The resulting N-doped hollow carbon fiber films (NHCFs) exhibit superior bifunctional ORR/OER performance with a low potential difference of only 0.60V. The rechargeable ZABs with NHCFs as metal-free cathodes possess a long-term cycling stability. Furthermore, the NHCFs can be used as FFAEs for flexible ZABs which have a high specific capacity and good cycling stability under different bending states. This work paves the way to design and produce highly active metal-free bifunctional FFAEs for electrochemical energy devices.

Interfacial MoO2 nanograins assembled over graphitic carbon nanofibers boosting efficient electrocatalytic reduction of nitrate to ammonia

Electrocatalytic nitrate reduction reaction (NO3-RR) for sustainable carbon-free hydrogen carrier (NH3) production from polluted NO3- sources of industrial wastewater is very promising. Mo-based catalysts are defined as popular electrocatalytic materials, but the rational performance achievement of Mo-based catalysts in the NO3-RR remains limited. In this study, to overcome the NO3-RR activity limitation, the interfacial MoO2 nanograins assembled on the N-functional carbon nanofibers (defined as MoO2/C) were constructed by electrospun and controlled graphitizing process. The comparative catalysts dominated by molybdenum oxides namely MoO2/MoO3 were synthesized by controlled calcination in air atmosphere. The MoO2 nanograins anchored in situ on carbon nanofibres could afford more interfacial active regions and accelerate the electron transfer efficiency of the electrocatalytic process by graphitic carbon fiber network. More importantly, MoO2/C was endowed with more oxygen vacancy sites which can trap the free NO3- ions over the reactive sites to enhance the surface interaction of NO3- with catalytic sites during the reaction process. The experimental results showed that the electrocatalytic nitrate reduction performance of the catalyst MoO2/C obviously outperformed that of MoO2/MoO3 in the light of the atomic activity efficiency with a near 7.5 folds enhancement. The MoO2/C affords the highest NH3 yield of 4838.5 µg h−1 mgcat−1 and Faraday efficiency of 30 % at –0.9 V vs.RHE and was endowed with 50 h of continuous reaction stability, proving the potential in practical electrochemical water treatment involving nitrate contamination.

Metal-chelating-membrane-derived TM/TMOx nitrogen-doped carbon fibers as efficient oxygen reduction electrocatalysts.

A metal-chelating membrane was exploited for the facile synthesis of N-doped graphitic carbon fibers (N-CFs) with abundant TM/TMOx nanoparticles completely exposed on the surfaces of the fibers. The ready accessiblity to multiple active sites and strong synergistic effects endowed the Fe/Fe3O4@N-CFs with optimal qualities, in particular delivering enhanced ORR performance in alkaline and neutral medium.

Tuning microstructures of polyacrylonitrile-based carbon fibers by catalytic influence of boron for enhancement of mechanical properties and oxidation resistance

Boron catalytic graphitization of carbon fibers (CFs) is an effective methodology for reducing energy costs with the enhancement of tensile and oxidation resistance properties by re-constructing the crystal structure of CFs. Herein, a microwave plasma graphitization system for boron catalytic graphitization was devised. The effect of boron on microstructure and properties of CFs during boron catalytic graphitization process was investigated and analyzed. The mechanism of boron doping in different graphitization times was proposed. Furthermore, the results show that the tensile properties and oxidation resistance of CFs are improved and directly related to the microstructure of CFs, which depends on the different boron catalytic graphitization stages. This work provides the effect of boron on microstructure and properties of CFs during microwave plasma catalytic graphitization in different graphitization times and has important implications for deeply understanding the boron catalytic graphitization process which is beneficial for the preparation of CFs with excellent performance.

Carbon: A Ubiquitous Electrode Material for Lithium-Based Rechargeable Batteries

In recent times, research has been directed to develop high-capacity anodes along with high-energy-density (high capacity and high voltage) and safe Lithium-ion battery (LIB) cathodes to power electric vehicles (EV’s). State-of-the-art lithium-ion cells use layered transition metal oxides (LiCoO2, LiNi1/3Mn1/3Co1/3 or LiNi0.8Co0.15Al0.15O2), or Phosphates (LiFePO4), Mn-based spinels (LiMn2O4) as cathodes and graphitic carbon as anode [1-2]. The nominal capacities of most of these cathodes range between 140-180 mAh g-1 when cycled up to 4.2 V. This is only half the specific capacity of graphite anode (372 mAh g-1). Thus, there has been intense research activity in the last decade to develop high-capacity anodes or high energy (high capacity and high voltage) and safe cathodes for lithium-ion batteries (LIBs) [1-2].Eliminating binders and carbon diluents and replacing carbon fiber-based 3D electrode architectures can improve the capacity utilization and C-rate performance, thereby improving energy density, cycle life, and safety of LIBs. The presentation will be focused on the development of organic binder and conducting diluent-free carbon fiber-based 3D electrodes architectures for LIBs, where the conventional copper (Cu) and aluminum foil (Al) foil current collectors are replaced with highly conductive carbon fibers (CFs). In this approach, the petroleum pitch (P-pitch) is used as a binder that adequately coats between the CFs and active nanoparticles (NPs) at high temperatures to form a uniform continuous layer of carbon coating along the exterior surfaces of NPs and 3D CFs. As a result, the electrodes assembly delivers superior electrochemical performances than conventional electrode fabrications. 3D electrode architecture of LiFePO4, FeF3, Li2MnSiO4 cathodes, and Si-C anodes will be presented [3-5].Dual carbon batteries (DCBs) based on LIB electrolytes have been evolving in recent times [5]. In DCBs, both electrodes consist of carbonaceous materials, and the ions from the electrolyte intercalate and deintercalate into the electrode matrix. During the charge, the cations and anions get inserted into the anode and cathode, respectively, and during discharge, the process is reversed. A DCB based on the 3D electrode architecture of carbon (zero transition metal ion) will be discussed. A DCB based on fully graphitic carbon fiber can have a nominal voltage of 4.65 V and can deliver energy densities of 92.7, and 110.9 Wh kg−1 at a power density of 114 W kg−1 for the cells cycled at 3.0–5.0 and 3.0–5.2 V, respectively. It is believed that the study presented here may contribute to the future development of carbon fiber-based dual-carbon and lithium-ion batteries.

Understanding the catalytic mechanism of calcium compounds for enhancing crystallinity in carbon fiber

Graphitized carbon fibers are attractive materials because of their high tensile modulus and thermal and electrical conductivities. These attributes derive from their crystalline structures that develop during heat treatments of up to 3000 °C. Despite the costly thermal processes, there is a structural limit for achieving these sought-after properties for polyacrylonitrile-based carbon fibers. Herein, the preparation of polyacrylonitrile-based carbon fibers with highly developed microstructures via calcium-assisted thermal treatments of up to 2700 °C is reported. Carbon fibers hydrothermally immersed in a solution of calcium carbonate were heat-treated and their chemical structures traced to investigate the calcium-assisted catalytic graphitization mechanism. Graphitic structures appeared at 1400 °C, accompanied by intermediate complexes of carbon and calcium on the carbon fibers surfaces. Further heat treatment of the calcium compounds at 1600 °C to incorporate carbon fibers resulted in an interlayer spacing of 0.3360 nm, which was unachievable solely through heat treatment at 2700 °C. In addition, the achieved tensile modulus and electrical conductivity of 480 GPa and 1.7 × 103 S/cm, respectively, were significantly higher than those of pure carbon fibers. The calcium ions penetrating the internal structure of the carbon fibers aligned the non-uniform graphene structure and developed the graphite structure of the carbon fibers by acting as catalysts, even at low temperatures.

Investigating K+ Storage Behavior of Highly Graphitized Carbon Fibers as Anodes for a Potassium-Ion Battery.

Many problems of potassium-ion batteries (PIBs) are hidden under a low mass load of the active material. However, developing research based on areal capacity is challenging for PIBs, due to the lack of an anode capable of delivering a stable capacity of more than 1 mAh cm-2. This work investigates the K+ storage behavior of highly graphitized carbon fibers (HG-CF), which exhibit automatic structural adjustments to mitigate voltage polarization. The created defects and residual K+ in the structure favor the reversible insertion/deinsertion of K+. HG-GF after structural adjustment realizes a capacity of 2 mAh (1.13 cm-2) without K deposition and a stable cyclic stability (>500 h). In situ X-ray diffraction and in situ Raman spectra were used to detect defect formation and structural evolution during cycles. This work demonstrates the feasibility of HG-GF as an anode for PIBs and provides a suitable anode for further research of PIBs based on areal capacity.

Improved net energy recovery in a sludge anaerobic digestion process by coupling an electrochemical system: electrode material and its impact on suspended microbial community.

Despite its great potential to recover energy from waste sludge, anaerobic digestion (AD) still needs to solve issues such as slow hydrolysis and H2 inhibition. This study investigated the effects of coupling microbial electrolysis cell (MEC) with AD on the CH4 yield. Results and analysis show that the CH4 yield was significantly improved in MEC-AD reactors by two factors, i.e., enhanced and accelerated hydrolysis and acidogenesis, and enrichment of hydrogenotrophic methanogens in suspended culture. Compared with graphite rod and carbon fiber brush, carbon felt (CF) as an electrode showed the best performance in terms of net energy output. The CH4 yield of MEC-AD-CF was 40.2 L CH4/kg VS, 92.3% higher than in the control group, and the VS removal rate was also increased by 47.2%. Acetoclastic methanogens were dominant in the control AD reactor, while the relative abundance of Methanobacterium, which is electroactive and known as hydrogenotrophic methanogen, increased to 24.6% in MEC-AD with CF as electrodes.

Investigation on preparation and properties of carbon fiber graphite tailings conductive asphalt mixture: A new approach of graphite tailings application

The massive accumulation of graphite tailings (GT) brings huge pressure to environmental engineers. Meanwhile, the conductive asphalt pavement industry is suffering from the high construction cost and the complex acquisition of conductive materials. The application of GT in asphalt mixture as a conductive material may be a win–win solution for the above concerns. This study aims to evaluate the feasibility of preparing carbon fiber graphite tailings (CF-GT) conductive asphalt mixture. The optimum preparation technology and material ratio were explored. The service performance tests of the conductive asphalt mixture were conducted, including conductive characteristics, electrothermal performance and pavement performance. Based on the experimental results, 0.3% (mass fraction) 6 mm-polyacrylonitrile (PAN)-based carbon fiber (CF) and 12% (mass fraction) GT were selected as conductive materials to prepare conductive asphalt mixture with resistivity of 5.75 Ω∙m. The addition of GT reduced the resistance by a maximum of 59.8%. The temperature-sensitive and pressure-sensitive characteristics of the mixture have staged characteristics. Moreover, the resistance and stress of the mixture have an excellent linear correlation in the positive pressure coefficient (PPC) effect stage and negative pressure coefficient (NPC) effect stage respectively, especially NPC. Conductive asphalt mixture has a good heating effect after being powered on. GT combined with CF enhanced the high-&low-temperature performance but deteriorated the moisture damage resistance performance of the asphalt mixture. The feasibility of CF-GT conductive asphalt mixture was demonstrated.

N-doped graphitized carbon-coated Fe2O3 nanoparticles in highly graphitized carbon hollow fibers for advanced lithium-ion batteries anodes

Ferric oxide (Fe2O3) has become one of the most competitive candidates for the next-generation lithium-ion batteries anode materials due to its high theoretical reversible specific capacity (Cs, 1007 mAh g−1) and low price. However, the rapid capacity fading and poor rate performance deriving from drastic volume expansion (∼200 %), low Coulombic efficiency (CE), and poor electrical conductivity limit its application in LIBs. Herein, a novel encapsulation structure of Fe2O3 nanoparticles has been developed. Fe2O3 nanoparticles inlaid in the shells of hollow highly graphitized carbon fibers are coated by N-doped graphitized carbon (GF-FeO@NGC) by a catalytic graphitization, oxidation route of Fe-based catalyst. The GF-FeO@NGC electrode shows the first specific discharge/charge capacities of 1355/974 mAh g−1 with high initial Coulombic efficiency (ICE) of 72.0%, and excellent reversibility of lithiation/delithiation reaction. After 200 cycles at 0.1 A g−1, the GF-FeO@NGC electrode keeps a high reversible Cs of 918 mAh g−1 (retention of 94.3%) with a CE of 99.6%. It is noticeable that the GF-FeO@NGC electrode has good rate performance and robust cycling stability at high current density. After 300 cycles at 2 A g−1, the Cs retention is up to 97.1% with a CE of 99.7%. These are far superior to those of the GF-FeO (without NGC coating) and the most reported Fe2O3-based electrode materials. The mechanism behind these phenomena are studied.

Highly thermally conductive polyamide 6 composites with favorable mechanical properties, processability and low water absorption using a hybrid filling of short carbon fiber, flake graphite and expanded graphite

Abstract It is a challenge to maintain the mechanical properties and processability of thermally conductive polymer composites in the presence of high filling of heat conductive filler. An optimized hybrid filler system composed of flake graphite (FG), expanded graphite (EG) and short carbon fiber (CF) was introduced into PA6 matrix. The addition of EG to PA6 was found to be more effective in improving its thermal conductivity, while the addition of FG maintained favorable processability due to its lubrication effect. Furthermore, the hybrid filling of FG and EG has a synergistic effect on the enhancement of thermal conductivity. The ternary filling of FG, EG and CF produced highly heat conductive PA6 composites with high strength, favorable processability, and low water absorption. The thermal conductivity of 10CF/20FG/10EG/PA6 composite reached 3.45 W/m k, which is 12.3 times of pure PA6. Additionally, the flexural strength increased to 110 MPa, which is 37 % higher than that of pure PA6, and the water absorption was reduced to one quarter that of pure PA6.

One dimensional pea-shaped NiSe2 nanoparticles encapsulated in N-doped graphitic carbon fibers to boost redox reversibility in sodium-ion batteries

In recent years, sodium-ion batteries (SIBs) have emerged as a promising technology for energy storage systems (ESSs) because of the abundance and affordability of sodium. Recently, metal selenides have been studied as promising high-performance conversion-type anode materials in SIBs. Among them, nickel selenide (NiSe2) has received considerable attention due to its high theoretical capacity of 495 mAh g–1 and conductivity. However, it still suffers from poor cycling stability because of the low electrochemical reactivity, large volume expansion, and structural instability during cycles. To address these challenges, NiSe2 nanoparticles encapsulated in N-doped graphitic carbon fibers (NiSe2@NGCF) were synthesized by using ZIF-8 as a template. NiSe2@NGCF showed a high discharge capacity of 558.3 mAh g–1 with a fading rate of 0.14% per cycle after 200 cycles at 0.5 A g–1 in 0.01–3.0 V. At a very high current density of 5 A g–1, the capacity still displayed excellent long-term cycle life with a discharge capacity of 406.1 mAh g–1 with a fading rate of 0.016% per cycle after 3000 cycles. The mechanism of the excellent electrochemical performance of NiSe2@NGCF was thoroughly investigated by ex-situ XRD, TEM, and SEM analyses. Furthermore, NiSe2@NGCF//Na3V2(PO4)3 full-cell also delivered an excellent reversible capacity of 378.7 mAh g−1 at 0.1 A g−1 after 50 cycles, demonstrating its potential for practical application in SIBs.

Study on Strength and Conductivity of Graphite and Carbon Fiber Concrete

In order to study the effects of graphite and carbon fiber on the strength and conductivity of concrete, the compressive strength and conductivity of three types of composite concrete with different mixing ratios of graphite, glueless fiber and rubberized carbon fiber were tested. The results show that the strength of 5000 mesh graphite is weakened, but the ability to reduce resistivity is improved, and the resistivity can be stabilized at about 10 Ω·m. The performance of glue-free carbon fiber in concrete is better than rubberized carbon fiber. Carbon fiber can significantly change the electrical conductivity of concrete without significantly affecting the compressive strength of concrete. In the experiment, the best mixing ratio of concrete was cement 600 kg/m3, water-binder ratio 0.56, and 12mm glue-free carbon fiber content 0.89%. The 28d compressive strength is 36.4 MPa and the resistivity is 12.8 Ω·m.

Fabrication of Graphitized Carbon Fibers from Fusible Lignin and Their Application in Supercapacitors.

Lignin-based carbon fibers (LCFs) with graphitized structures decorated on their surfaces were successfully prepared using the simultaneous catalyst loading and chemical stabilization of melt-spun lignin fibers, followed by quick carbonization functionalized as catalytic graphitization. This technique not only enables surficial graphitized LCF preparation at a relatively low temperature of 1200 °C but also avoids additional treatments used in conventional carbon fiber production. The LCFs were then used as electrode materials in a supercapacitor assembly. Electrochemical measurements confirmed that LCF-0.4, a sample with a relatively low specific surface area of 89.9 m2 g-1, exhibited the best electrochemical properties. The supercapacitor with LCF-0.4 had a specific capacitance of 10.7 F g-1 at 0.5 A g-1, a power density of 869.5 W kg-1, an energy density of 15.7 Wh kg-1, and a capacitance retention of 100% after 1500 cycles, even without activation.