Carbon Nanofiber Electrodes Research Articles

A two-pronged strategy to boost the capacitive deionization performance of nitrogen-doped porous carbon nanofiber membranes

Carbon-based capacitive deionization (CDI) systems are universally subject to the limited desalination capacity, due to the electrosorption characteristics and undesirable pore structures. Herein, a two-pronged strategy is proposed to boost the desalination performance of the electrospun carbon nanofibers (CNFs), where silicalite-1 nanoparticles as the internal porogen create mesopores and macropores, and layered zeolitic imidazolate framework (ZIF-L) leaves as the external carbon source provide micropores and mesopores. This combination results in the large surface area, well-developed graded pore structure, and increased nitrogen content of the core-shell polyacrylonitrile/silicalite-1@ZIF-L-derived CNFs (defined as PCNFs-SZ) electrode, which delivers a superior specific capacitance of 145.4 F g−1 in a neutral electrolyte. The symmetric CDI cell assembled by the self-supporting PCNFs-SZ membrane electrodes holds a prominent desalination capacity of 37.09 mg g−1 and a rapid salt removal rate of 10.36 mg g−1 min−1 at 1.2 V (initial NaCl concentration: 500 mg L−1), and demonstrates significant potential for real-world applications in the desalination and purification of reclaimed water. Furthermore, theory calculations confirm the enhanced Na+-capture capability of PCNFs-SZ. The present work highlights an effective and viable approach to enhance the desalination performance of carbon-based CDI cells.

Free‐Standing Si@C/CNFs Prepared by Simple Electrospinning as a Stable Anode for Lithium‐Ion Batteries

AbstractThe development of free‐standing and foldable electrodes with excellent electrochemical performance is paramount for flexible electronic devices. However, the silicon‐based free‐standing anodes lack a straightforward preparation process. Herein, we successfully designed a hierarchical Si@C/CNFs composite material by combining hydrothermal and electrospinning techniques, in which the carbon‐coated silicon (Si@C) is served as the primary nanostructure and carbon nanofibers (CNFs) from electrospinning are maintained as the network matrix, resulting in a free‐standing anode. Owing to the amorphous carbon coating on Si nanoparticles and the formation of a 3D network structure of CNFs, which tightly encases the primary Si@C nanostructure, the Si@C/CNFs electrode demonstrates exceptional conductivity and flexibility. This dual carbon‐layer structure further enhances kinetics and mitigates the volume expansion of Si nanoparticles. The Si@C/CNFs electrode exhibits a high specific capacity (1573 mAh g−1 at 0.1 A g−1), exceptional rate capability, and excellent cycling stability (78.5 % capacity retention after 100 cycles). Thus, Si@C/CNFs can be a promising material for the anode electrode in flexible lithium‐ion batteries.

Cooperative Control of Bioelectrocatalytic Activity for Thermo- and Photo-Switchable Cup-Stacked Carbon Nanofiber Electrodes Modified with Phase Transition Polymer and Heme Peptide.

Empowering biocatalyst-modified electrodes with the ability to both enforce and perceive will enable the development of intrinsically switchable bioelectrode systems, which exhibit autonomous and heteronomous actions specific to living organisms. However, the electrocatalytic activity of switchable bioelectrodes reported so far has been controlled by changes in the rate of substrate transport to biocatalysts. Here, we prepared a cup-stacked carbon nanofiber (CSCNF) electrode modified with a thermoresponsive N-isopropylacrylamide-based polymer containing peroxidase model compounds (HP). As CSCNFs worked as a converter from near-infrared (NIR) light to heat, bioelectrocatalytic activity of the electrode to H2O2 reduction was reversibly controlled by changes in the amount of electroactive HP, based on expanded and contracted states of the polymers induced by not only environmental temperature changes but also external NIR light irradiation. This intrinsically switchable bioelectrode technique would hold promise for adding new performances in electrochemical biosensors and biofuel cells, for example, autonomous and heteronomous tunable sensitivity and capacity.

Enhancing electrochemical properties of bacterial cellulose-derived carbon nanofibers through physical CO2 activation

Carbon nanofiber (CNF) derived from carbonization of bacterial cellulose (BC), with a unique three-dimensional porous nanostructure, has received significant interest in electrochemical applications. In this study, CNF samples were physically activated in CO2 at different temperatures and durations. Raman spectroscopy and FTIR analysis showed that CO2 activation caused hexagonal lattice defects, disorder, and oxygen-related functional groups in an amorphous carbon structure. CNF surface morphology changed after physical activation, reducing fiber diameter to 55 nm and introducing mesopores. Through activation temperature and time adjustments, surface area (870.1 m2/g) and micropore surface area (535.6 m2/g) and pore volume (0.2148 cm3/g) increased. EDX elemental analysis showed that activated CNF had a carbon concentration of > 90 %, while XPS analysis showed surface functional groups like C-C (sp2) and C-C (sp3) hybridization, which could improve electrolyte ion adsorption and accessibility. Electrochemical properties improved owing to CO2 activation. The optimal activation condition of 800 ℃ for 60 min resulted in the highest specific area capacitance of 552 mF cm−2 at 1 mA cm−2. This activated CNF electrode retained capacitance nearly unchanged up to 3,000 cycles. It also achieved the highest energy density of 76.7 mWh cm−2 at 500 mW cm−2. This study demonstrates the efficacy of CO2 physical activation for enhancing the electrochemical properties of CNF electrodes. The findings also highlight the importance of tailoring activation conditions, providing valuable insights for the design of advanced energy storage materials.

Autonomous and heteronomous control of selectivity to pyrocatechol derivatives for near-infrared light-responsive cup-stacked carbon nanofiber/FTO electrodes modified with thermo-responsive polymers

Autonomous and heteronomous switchable selectivity for electrochemical reactions was examined in an electrolyte solution containing pyrocatechol (PC) and dopamine (DA) using a fabricated thermo- and photo-responsive poly(N-isopropylacrylamide) (PNIPA)-modified cup-stacked carbon nanofiber (CSCNF) electrode. PNIPA can be autonomously and reversibly switched by environmental temperature changes between hydrophilic expanded coil structure and hydrophobic collapsed globule structure. CSCNFs as the electrode materials can effectively convert absorbed external near-infrared (NIR) light into heat. Although the molecular size of DA is larger and the octanol-water partition coefficient of DA is smaller than those of PC, both PC and DA could permeate to the CSCNF electrode surface through the expanded coil structure of the PNIPA layer at 25 ˚C, which temperature is below the lower critical solution temperature (LCST), causing their electrochemical signal readout. In contrast, transport of DA to the electrode surface was selectively suppressed by exposing the polymer to temperature at 45 ˚C, which value is above the LCST, or NIR light irradiation (> 940 nm, ca. 77 mW cm–2) to the CSCNF electrode surface even at 25 ˚C due to the steric hindrance and hydrophobicity of collapsed globule structure of the polymer layer. This resulted in the preferential electrochemical signal of PC. The switchable sensitivity of the electrode also allowed it to be successfully demonstrated for the simultaneous determination of PC and DA even at a single transducer, though electrode arrays with different sensitivity and selectivity are widely used for the determination of multiple chemicals simultaneously.

Flexible Centrifugally Spun N, S-Doped SnS2-Including Porous Carbon Nanofiber Electrodes for Na-Ion Batteries.

Carbon nanofibers are promising for various applications such as energy storage, sensors, and biomedical applications; however, the brittle structure of nanofibers limits the usage of carbon nanofibers. For the first time, a facile and effective strategy is reported to fabricate flexible carbon nanofibers via a fast and safe nanofiber fabrication technique, centrifugal spinning, followed by heat treatment. Moreover, sulfidization was employed to fabricate high-performance flexible N, S-doped SnS2-including porous carbon nanofiber electrodes for sodium ion batteries via centrifugal spinning. Binder-free flexible centrifugally spun N, S-doped SnS2-including porous carbon nanofiber electrodes delivered a high reversible capacity of over 460 mAh/g at 100 mA/g. Furthermore, at a high current density of 1 A/g, the electrodes showed a reversible capacity of over 300 mAh/g with excellent cycling stability in 2000 cycles. This work reports a fast, low-cost, and facile way to prepare flexible carbon nanofibers with tunable morphology and various compositions, which could be applicable for different energy storage applications.

Stable Structure and Fast Ion Diffusion: A Flexible MoO2@Carbon Hollow Nanofiber Film as a Binder-Free Anode for Sodium-Ion Batteries with Superior Kinetics and Excellent Rate Capability.

Designing innovative anode materials that exhibit excellent ion diffusion kinetics, enhanced structural stability, and superior electrical conductivity is imperative for advancing the rapid charge-discharge performance and widespread application of sodium-ion batteries. Hollow-structured materials have received significant attention in electrode design due to their rapid ion diffusion kinetics. Building upon this, we present a high-performance, free-standing MoO2@hollow carbon nanofiber (MoO2@HCNF) electrode, fabricated through facile coaxial electrospinning and subsequent heat treatment. In comparison to MoO2@carbon nanofibers (MoO2@CNFs), the MoO2@HCNF electrode demonstrates superior rate capability, attributed to its larger specific surface area, its higher pseudocapacitance contribution, and the enhanced diffusion kinetics of sodium ions. The discharge capacities of the MoO2@HCNF (MoO2@CNF) electrode at current densities of 0.1, 0.2, 0.5, 1.0, 2.0 and 5.0 A g-1 are 195.55 (155.49), 180.98 (135.20), 163.81 (109.71), 144.05 (90.46), 121.16 (71.21) and 88.90 (44.68) mAh g-1, respectively. Additionally, the diffusion coefficients of sodium ions in the MoO2@HCNFs are 8.74 × 10-12 to 1.37 × 10-12 cm2 s-1, which surpass those of the MoO2@CNFs (6.49 × 10-12 to 9.30 × 10-13 cm2 s-1) during the discharging process. In addition, these prepared electrode materials exhibit outstanding flexibility, which is crucial to the power storage industry and smart wearable devices.

Carbon nanofiber electrodes without commercial polymer precursors deliver superior electrochemical performance

Carbon nanofiber (CNF) electrodes are conductive and electrochemically stable, making excellent supercapacitor components. However, such fibers are commonly made from commercial polymer precursors, such as polyacrylonitrile (PAN), which are expensive to produce. Further, PAN carbon fibers are inert and lack porous surfaces, limiting their use as supercapacitor electrodes without further modification. We demonstrate the use of coal-derived polyurethane (CPU) in lieu of PAN, producing a cheap alternative precursor. Electrospinning and carbonization of this precursor produces porous fibers which are rich in nitrogen and oxygen species, creating an active surface facilitating fast faradaic reactions (FFRs). These electrodes offer superior electrochemical performance, with 604 F g−1 at 1 A g−1. After an initial activation period, this capacitance is stable over 10,000 cycles. In a symmetrical two electrode cell, this activated carbon offers superior rate performance and power-energy density trade-off compared to commercial and literature activated carbon electrodes with 20.9 Wh kg−1 energy density at a power density of 0.5 kW kg−1.

MOP-18-Derived CuO Fiber for Hybrid Supercapacitor Electrodes.

This study explores a simple method of fabricating hybrid supercapacitor electrodes, which could potentially broaden the application of this technology. The method involves electrospinning a uniform solution of Matrimid/Metal-Organic Polyhedra 18 (MOP-18) followed by carbonization at a relatively low temperature of 700 °C in air, rather than in an inert atmosphere, to create free-standing, redox-active hybrid supercapacitor electrodes. Additionally, the synthesis procedure requires no stabilization or activation steps, which enhances the cost effectiveness of the synthesized electrode materials. The resulting C/CuO composite was used as the working electrode, with a polyacrylonitrile (PAN)/Poly(methyl methacrylate) (PMMA) carbon nanofiber (CNF) electrode as the counter and 6 M KOH as the electrolyte in a T-cell configuration. The cell performance and redox activity were evaluated using cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), electrochemical impedance spectroscopy (EIS) and cycling stability tests. Additionally, the physical and chemical structures of the electrode materials were assessed using X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron spectroscopy (TEM), X-ray diffractometry (PXRD), surface area analysis and other characterization techniques. The electrode material demonstrated a specific capacitance of up to 206 F/g. Supercapacitors utilizing this material display an energy density of 10.3 Wh/kg (active material) at a current density of 1 A/g in electrochemical testing.

Laser‐Induced Carbon Nanofiber‐Based Redox Cycling System

AbstractInvited for this issue's Front Cover is the group of Nongnoot Wongkaew. The cover picture shows an example of a 3D‐electrochemical redox‐cycling system made from laser‐induced carbon nanofiber electrodes where a fibrous insulating layer with a thickness in the range of micrometers is placed vertically between two electrodes. The cyclic voltammograms in blue and green exhibit the current response from the generator and collector, respectively, while the orange‐pink one represents the situation without redox cycling. Read the full text of the Research Article at 10.1002/celc.202300271.

Polyacrylonitrile-based carbon nanofiber electrode fabricated via electrospun for supercapacitor application

The versatile properties of electrospun carbon nanofibers gaining attention for electrode materials for supercapacitors. The heat treatment process of stabilization played an important role before the carbonization process in electrode fabrication. In the present study, electrospun stabilized polyacrylonitrile nanofiber (St PAN) and carbonized Polyacrylonitrile nanofiber (CNF) at minimum temperature were used as active mass for supercapacitor electrodes. Stabilized CNF nanofiber sample showed a reduction in nanofiber diameter with increased carbon percentage. XRD results showed increased crystallinity in the CNF sample as compared with the Stabilized PAN sample. Electrochemical characterization was performed to measure specific capacitance and to analyze the charge storage mechanism. The proportion of capacitive and diffusion-controlled contributions to energy storage was estimated using Dunn’s model. The results obtained demonstrated that, in comparison to the St PAN electrode, the CNF electrode exhibited a greater capacitive-controlled contribution. The CNF sample has shown an increased capacitive contribution of 82.3% as compared with the St PAN sample. This work provides a method for making electrospun carbon nanofiber-based electrodes as well as a methodical methodology for examining the charge storage process.

Enhancing the performance of quasi-solid-state flexible supercapacitors with Ag and MnO2 co-decorated carbon nanofibrous electrodes

Flexible supercapacitors are gaining increasing popularity due to their potential in powering portable, wearable, and lightweight electronic devices. In this study, we have successfully developed a high-performance flexible electrode for quasi-solid-state supercapacitors by incorporating Ag into carbon nanofibers (CNF) through electrospinning, and growing MnO2 as an active material on the electrode using an in-situ redox method. The Ag and MnO2 co-decorated CNF electrode offers several advantages over conventional CNF electrodes, including an enlarged reaction area, higher charge storage capacity, and improved resistance to brittleness issues. Among all the quasi-solid-state supercapacitors tested, the MnO2-decorated electrode with an optimized Ag incorporation exhibited the highest specific capacitance of 184 F/g at a current density of 1 A/g, representing a remarkable 17-fold increase compared to the reference CNF electrode. Furthermore, the Ag and MnO2 co-decorated electrode demonstrated an energy density of 16.3 Wh/kg and a power density of 400 W/kg at the same current density. Notably, the electrode exhibited excellent flexibility, with a capacitance retention rate of 87 % when subjected to bending with a curvature ranging from 5 to 1.25 cm. Our results suggest that the Ag and MnO2 co-decorated CNF electrode holds great promise for flexible energy storage applications.

Gradient Pores Enhance Charge Storage Density of Carbonaceous Cathodes for Zn-Ion Capacitor.

Engineering carbonaceous cathode materials with adequately accessible active sites is crucial for unleashing their charge storage potential. Herein, activated meso-microporous shell carbon (MMSC-A)nanofibers are constructed to enhance the zinc ion storage density by forming a gradient-pore structure. A dominating pore size of 0.86nm is tailored to cater for the solvated [Zn(H2 O)6 ]2+ . Moreover, these gradient porous nanofibers feature rapid ion/electron dual conduction pathways and offer abundant active surfaces with high affinity to electrolyte. When employed in Zn-ion capacitors (ZICs), the electrode delivers significantly enhanced capacity (257 mAh g-1 ), energy density (200Wh kg-1 at 78W kg-1 ), and cyclic stability (95% retention after 10000 cycles) compared to nonactivated carbon nanofibers electrode. A series of in situ characterization techniques unveil that the improved Zn2+ storage capability stems from size compatibility between the pores and [Zn(H2 O)6 ]2+ , the co-adsorption of Zn2+ , H+ , and SO4 2- , as well as reversible surface chemical interaction. This work presents an effective method to engineering meso-microporous carbon materials toward high energy-density storage, and also offers insights into the Zn2+ storage mechanism in such gradient-pore structures.

Preparation of Zeolitic Imidazolate Framework and Carbon Nanofiber Composites for Nitrofurazone Detection

Metal–organic frame (MOF) materials may have the advantages of a regular pore structure, large porosity, and large specific surface area, which could provide better catalytic activity, but they have some disadvantages in electrocatalysis. In contrast, carbon nanofibers (CNFs) prepared by electrospinning methods have good conductivity and stability. Therefore, this research aimed to generate MOF/CNFs composite materials to improve the electrochemical properties of MOF materials and apply them to the field of electrochemical sensing. This experiment was based on the preparation of straight unidirectional CNFs by an electrospinning method at 2000 RPM. The original method of preparing zeolitic imidazolate frameworks (ZIF-8) was improved and ZIF-8 was uniformly dispersed on the surface of CNFs to form a ZIF-8/CNF composite with a fiber diameter of about 0.10 to 0.35 µm. The specific surface area of the CNFs was about 42.28 m2/g, while that of the ZIF-8/CNF composite was about 999.82 m2/g. The specific surface area of the ZIF-8/CNF composite was significantly larger than that of CNFs. The GCE/ZIF-8/CNF electrode had an excellent electrochemical reaction, with an oxidation peak at about 216 μA, which proved that the ZIF-8/CNF composite material would have good catalytic activity and excellent electrochemical properties for the detection of nitrofurazone compared to other modified electrodes.

Bioelectrocatalytic reduction by integrating pyrite assisted manganese cobalt-doped carbon nanofiber anode and bacteria for sustainable antimony catalytic removal

A novel manganese cobalt metal–organic framework based carbon nanofiber electrode (MnCo/CNF) was prepared and used as microbial fuel cell (MFC) anode. Pyrite was introduced into the anode chamber (MnCoPy_MFC). Synergistic function between pyrite and MnCo/CNF facilitated the pollutants removal and energy generation in MnCoPy_MFC. MnCoPy_MFC showed the highest chemical oxygen demand removal efficiency (82 ± 1%) and the highest coulombic efficiency (35 ± 1%). MnCoPy_MFC achieved both efficient electricity generation (maximum voltage: 658 mV; maximum power density: 3.2 W/m3) and total antimony (Sb) removal efficiency (99%). The application of MnCo/CNF significantly enhanced the biocatalytic efficiency of MnCoPy_MFC, attributed to its large surface area and abundant porous structure that provided ample attachment sites for electroactive microorganisms. This study revealed the synergistic interaction between pyrite and MnCo/CNF anode, which provided a new strategy for the application of composite anode MFC in heavy metal removal and energy recovery.

Review of electro-spun carbon nanofiber electrode materials for electrochemical capacitors

Schematic illustration demonstrating various approaches to enhance the electrochemical performance of carbon nanofiber electrode materials.

Hydrogen-bonded organic framework-derived, flower-on-fiber-like, carbon nanofiber electrodes for supercapacitors

Hydrogen-bonded organic frameworks (HOFs) are a new type of porous material and have great potential as electrode material precursors because of their high porosity.

Electrospun carbon nanofibers decorated with NiS2-FeS2 used as efficient counter electrode for quantum dot sensitized solar cells

NiS2-FeS2 composite material is uniformly coated on CNFs by a one-step hydrothermal method with carbon nanofibers (CNFs) prepared by the electrostatic spinning method. A composite NiS2-FeS2/CNFs with Ti-mesh substrate counter electrode (NiS2-FeS2/CNFs CE) is prepared by scraping and coating method on a metal titanium mesh and applied to quantum dot sensitized solar cells (QDSSCs). The photoelectric power conversion efficiency of QDSSCs assembled on NiS2-FeS2/CNFs electrode substrate is 9.85%, which is much higher than that of traditional Cu2S/brass (7.85%). The exceptional achievement can be attributed to the superb amalgamation of the Ti-mesh's excellent electrical conductivity and the NiS2-FeS2/CNFs nanostructure's high and stable catalytic activity. The co-loading of NiS2 and FeS2 reduces the particle size of the composite, enhancing the specific surface area of the counter electrode. It provides abundant catalytic active sites for QDSSCs. The experimental results show that NiS2-FeS2 is expected to be a competitive and efficient QDSSCs CE material.

ZnFe2O4-infused hierarchically porous carbon nanofiber electrode for enhanced capacitive deionization

Highly porous carbon materials with abundant active adsorption sites are desirable for capacitive deionization (CDI). However, their limited salt adsorption capacity, slow desalination rate, and sensitivity to salt concentrations hinder practical applications in low salinity water treatment. In this study, we successfully synthesized a hierarchically porous carbon nanofiber electrode infused with ZnFe2O4 prepared by electrospinning the FeⅢ-MOF-5/benzoxazine/polyacrylonitrile (FeⅢ-MOF-5/BA-a/PAN) system, followed by high-temperature curing, KOH activation, and carbonization processes. The activated electrode material exhibited remarkable characteristics, including an exceptionally high specific surface area of 2506.73 m2 g−1 and significantly enhanced mesoporosity. Results demonstrated pseudo-capacitive behavior with a specific capacitance of 149.3 F g−1 and excellent electrochemical cycling stability. Notably, the electrode showed significant adsorption capacities in a 1000 mg L−1 NaCl solution at applied potentials of 1.2 and 1.6 V, with values of 74.27 and 88.95 mg g−1, respectively. The adsorption process followed both the Freundlich isotherm and the pseudo-second-order kinetic models. These findings highlight the promising potential of the ZnFe2O4-infused porous carbon nanofiber electrode for efficient desalination and ion removal applications.

Structural energy storage system using electrospun carbon nanofibers with carbon nanotubes

AbstractIn the present study, carbon nanofibers containing multi‐walled carbon nanotubes (MWCNTs) were fabricated and employed as electrodes for structural supercapacitors. Carbon nanofibers were utilized as the electrode material in structural supercapacitors to increase the specific surface area. Electrospun polyacrylonitrile (PAN) nanofibers underwent conversion to carbon nanofibers through stabilization and carbonization processes aided by thermal treatment. The specific surface area of the electrospun carbon nanofiber electrodes was further increased approximately 118 times (1946.9 m2/g) using an activation process in comparison with that of non‐activated carbon nanofibers (16.43 m2/g). Multifunctional supercapacitors were fabricated by employing electrospun carbon nanofibers and a vacuum resin infusion technique. The specific capacitance of activated carbon nanofibers (ACNF) and ACNF‐MWCNT exhibited significant improvement (14.87 and 48.25 mF/cm2, respectively) compared to non‐activated carbon nanofibers (CNF‐MWCNT: 1.71 mF/cm2). This improvement was attributed to the reduction in equivalent series resistance and the increase of the surface area of the nanofiber electrodes. Additionally, the carbon nanofiber electrodes contributed to an increased interlaminar fracture toughness of structural supercapacitors, acting akin to “Velcro” between fabric interfaces. This work serves as a “proof of concept” for a straightforward and efficient method to manufacture electrodes for structural supercapacitors based on the electrospinning technique.Highlights Fabrication of carbon nanofibers containing MWCNTs using electrospinning. The carbon nanofiber as an electrode for structural supercapacitors. Simple and effective method. Dramatically improving specific capacitance of the supercapacitors.