Hollow Carbon Fibers Research Articles

Preparation of NiFe2O4@ slit modified hollow carbon fiber via electrospinning for supercapacitor electrode material

Nickel ferrite owns a lot of advantages as electrode materials for supercapacitor, such as high energy density and excellent theoretical capacity. Whereas, the electrochemical performances of NiFe2O4 in terms of rate performance and cycle stability are not satisfactory due to the low conductivity. While carbon fiber is a kind of material with high conductivity. Hence, NiFe2O4@ slit modified hollow carbon fiber is obtained through the coaxial electrospinning method. The slits on hollow carbon fibers are beneficial to the contact of inner NiFe2O4 nanoparticles with electrolyte. Results of electrochemical tests show that at a current density of 1 A/g, the specific capacitance of NiFe2O4@ slit modified hollow carbon fiber is calculated to be 225.4 F/g, higher than that of NiFe2O4 nanoparticles of 134.8 F/g. Moreover, a better cycle and rate performances (100 % vs 80 %; 71.9 % vs 47.5 %) are achieved. This work displays that slit modified hollow carbon fiber can improve the electrochemical performance of NiFe2O4 efficiently.

N-doped porous carbon network anchoring on hollow wooden carbon fibers for high-performance electrode materials in supercapacitors

N-doped porous carbon network anchoring on hollow wooden carbon fibers for high-performance electrode materials in supercapacitors

Calotropis gigantea fiber confined ZIF-67 derived Co, N in-situ assembled hollow carbon fiber to activate peroxymonosulfate for degradation of perfluorooctanoic acid

Perfluorinated compounds have serious impacts on ecosystems and threats to human health, and exploring technologies to remove them is urgently needed. Using Calotropis gigantea fiber (CGF) as the biological template, the precursor of ZIF-67 was firstly in-situ anchored in the inner/outer walls of the fiber and then pyrolyzed to yield the composite catalyst labelled as Co/C@C. In combination with peroxymonosulfate (PMS), the advanced oxidation system, i.e. Co/C@C/PMS, was constructed for the catalytic removal of perfluorooctanoic acid (PFOA) from water. The experimental results showed that under the optimized conditions of PMS dosage of 1.0 g/L, catalyst dosage of 0.5 g/L and pH 3.0, PFOA achieved the degradation efficiency of 72.2% within 4 h at ambient temperature. Combined with free radical quenching, electron paramagnetic resonance, electrochemistry and nitroblue tetrazolium dichloride-based UV-Vis analysis, the reactive oxygen species and diverse pathways were identified, including SO4•−, O2•−, O21 and electron transfer process in the Co/C@C/PMS system. The coexisting anions (HCO3−, Cl−, H2PO4− and NO3−) and real wastewaters showed no significant effects on PFOA degradation, demonstrating that the Co/C@C/PMS system has good resistance to external ions and different media. After four cycles, the degradation efficiency of PFOA was still 62.8%, indicating that Co/C@C has high stability and good reusability. The degradation products of PFOA were mainly short-chain perfluorinated carboxylic acids (C4-C7) and hydrogen-substituted perfluorinated compounds. Based on quantitative structure-activity relationship analysis, their ecotoxicity was finally evaluated via ECOSAR method. In short, natural CGF derived Co/C@C has great potential for the reduction of emerging PFOA to achieve a sustainable water environment for humans.

Integrating V-doped CoP on Ti3C2Tx MXene-incorporated hollow carbon nanofibers as a freestanding positrode and MOF-derived carbon nanotube negatrode for flexible supercapacitors

Novel architectural electrode materials that are freestanding and exhibit improved electrochemical performances in flexible asymmetric supercapacitors are urgently needed; however, designing these materials is challenging. Herein, a Ti3C2TX MXene-aligned hollow carbon fiber (MX/HCF) is engineered and vanadium-doped cobalt phosphide nanorod arrays are grown on it (V-CoP@MX/HCF) and applied for supercapacitor positrode. V doping modulates the surface structure and electronic environment of CoP nanorods grown over conductive and flexible MX/HCFs. As expected, the optimized V-CoP@MX/HCF exhibits a better electrochemical performance (1896.8Fg−1) than that of CoP@MX/HCF and CoP@HCF. For the negative electrode, zeolitic imidazolate framework-67 (ZIF-67) grown on electrospun polyacrylonitrile (PAN) fibers is converted to cobalt nanoparticle-encapsulated nitrogen-doped carbon nanotubes at carbon nanofibers (Co-CNT@CNF) by a simple heat treatment without the burden of external catalysts and reducing gases. The as-designed freestanding Co-CNT@CNF delivers a specific capacitance of 405.5Fg−1 with superior cycling stability. A flexible asymmetric supercapacitor (V-CoP@MX/HCF//Co-CNT@CNF) is designed that unveil remarkable electrochemical properties, such as a high energy density of 72.4 Wh kg−1 at 800.12 W kg−1 and good capacitance retention (91.4 %) after 10,000 charge/discharge cycles. Furthermore, the device can maintain a consistent performance regardless of the bending degree. More importantly, this work provides new opportunities to rationally design novel freestanding cathodes and anodes for high-performance flexible asymmetric supercapacitors.

Boosting Potassium Storage via Multifunctional Interface with High Lattice-Matching.

Atomic-scale interface engineering is a prominent strategy to address the large volume expansions and sluggish redox kinetics for reinforcing K-storage. Here, to accelerate charge transport and lower the activation energy, dual carbon-modified interfacial regions are synthesized with high lattice-matching degree, which is formed from a CoSe2 /FeSe2 heterostructure coated onto hollow carbon fibers. State-of-the-art characterization techniques and theoretical analysis, including ex-situ soft X-ray absorption spectroscopy, synchrotron X-ray tomography, ultrasonic transmission mapping, and density functional theory, are conducted to probe local atomic structure evolution, mechanical degradation mechanisms, and ion/electron migration pathways. The results suggest that the heterostructure composed of the same crystal system and space group can sharply regulate the redox kinetics of transition metal selenium and dual carbon-modified approach can tailor physicochemical degradation. Overall, this work presents the design of a stable heterojunction synergistic superior hollow carbon substrate, inspiring a pathway of interface engineering strategy toward high-performance electrode.

Hollow carbon fiber from waste biomass of acacia leaves for Fe(II) removal from aqueous solution

Hollow carbon fiber from waste biomass of acacia leaves for Fe(II) removal from aqueous solution

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.

Biomass-derived nitrogen-doped carbon fiber driven δ-MnO2 for aqueous zinc-ion batteries with high energy and power density

Aqueous zinc-ion batteries (AZIBs) are considered potential devices for energy storage because of their low cost and high level of safety. However, the efficiency of AZIBs is influenced by the cathode reaction kinetics. Herein, we propose the δ-MnO2 nanorods grow in situ on natural loofah sponge-derived nitrogen-doped hollow carbon fibers (HCF), which can significantly improve both ion/electron transfer rate and provide structural stabilization. The self-assembled δ-MnO2-HCF (HCM) electrodes exhibit excellent electrochemical performances, including an impressively specific capacity (341 mAh g−1 at 0.2 A g−1), exceptional long cycling stability (87% capacity retention after 3500 cycles at 2 A g−1), and superb energy density and power density (540 Wh kg−1 at 288 W kg−1 and 164 Wh kg−1 at 5485 W kg−1), all based on the mass of cathode. In addition, the inclusion of HCF leads to a notable enhancement in the electrical conductivity of HCM, and a reduction in the energy barriers for Zn ions to diffuse between the δ-MnO2 layers, according to density functional theory (DFT) calculations. It is promising that the HCM will serve as a design guide for developing cost-effective and high-performance cathode materials for AZIBs.

Design of Co-doped hollow multi-channel carbon fibers for high performance lithium sulfur batteries

The low conductivity of active material and the detrimental shuttle effect of lithium polysulfides (LiPSs) intermediates in lithium sulfur batteries (LSBs) mainly limit their practical application. In this work, the well-designed “tube-in-fiber” structure is fabricated via confining carbon nanotubes (CNTs) in Co-doped hollow multi-channel carbon fibers (MCCFs-Co) as sulfur host material for LSBs. As a result, the MCCFs-Co/CNTs composite with hierarchically porous structure and high specific surface area demonstrate excellent electrolyte wettability and rapid Li ion diffusion rate. The addition of CNTs and Co nanoparticles improves the absorption capability and catalytic conversion activity of the composite towards LiPSs, thereby enhancing the redox kinetics and alleviating the shuttle effect. Consequently, the MCCFs-Co/CNTs/S cathode delivers remarkable cycling stability (843 mAh g−1 after 150 cycles at 0.5 C) and outstanding rate capability (698 mAh g−1 after 300 cycles at 2.0 C).

Phragmites-derived magnetic carbon fiber with hollow assembly architecture toward full-covered effective bandwidth at Ku band

Lightweight and efficient electromagnetic wave absorption (EMA) materials are in high demand, and magnetic carbon fiber composites show potential. However, impedance matching issues make achieving full coverage of the Ku band challenging, hindering improvements in effective absorption bandwidth. This study proposes innovative compositional and structural designs coupling magnetic carbon fibers to balance electromagnetic attenuation and impedance matching. We assemble 1D phragmites-derived hollow carbon fibers (PCF) with 3D CoFe2O4 (CFO) hollow nanoparticles to create a composite with two different dimensions and mechanisms of loss. CFO hollow nanoparticles uniformly distributed on the PCF conductively lose energy and enable multiple reflections. Furthermore, by designing the thermal decomposition temperature and magnetic components, high-frequency electromagnetic parameters can be controllably adjusted. Notably, PCF7-CFO exhibits excellent reflection loss of −57.8 dB at 14.8 GHz with a filling ratio of 20 wt% and matching thickness of 2.0 mm, with an effective absorption bandwidth reaching 5.9 GHz, almost covering the entire Ku band. The hollow-assembly structure balances impedance matching and high-frequency attenuation, achieving full-Ku-band coverage for developing efficient electromagnetic wave absorbers with biomass-derived carbon materials.

Amino acids functionalized vascular-like carbon fibers for efficient capacitive deionization

Porous carbons have attracted great attention in capacitive deionization (CDI), benefiting from their high surface areas and abundant adsorption sites. However, the sluggish adsorption rate and poor cycling stability of carbons are still concerns, which are caused by the insufficient ion-accessible networks and the side reactions (the co-ion repulsion and oxidative corrosion). Herein, inspired by the blood vessels in organisms, mesoporous hollow carbon fibers (HCF) were successfully synthesized via a template assisted coaxial electrospinning strategy. Subsequently, the surface charge of HCF was modified by various amino acids (arginine (HCF-Arg) and aspartic acid (HCF-Asp)). Combining structure design and surface modulation, these freestanding HCFs present enhanced desalination rate and stability, in which the hierarchal vasculature facilitates electron/ion transport, and the functionalized surface suppresses the side reactions. Impressively, when HCF-Asp and HCF-Arg serve as cathode and anode respectively, the asymmetric CDI device provides an excellent salt adsorption capacity of 45.6 mg g−1, a fast salt adsorption rate of 14.0 mg g−1 min−1 and a superior cycling stability up to 80 cycles. In short, this work evidenced an integrated strategy to exploiting carbon materials with outstanding capacity and stability for high-performance capacitive deionization.

Free-standing N-doped hollow carbon fiber encapsulate P/GeP hybrid anode for rechargeable Li-ion battery

Red phosphorus (RP) with appropriate working voltage and high lithium storage specific capacity has been considered as high-performance anode for Li-ion battery (LiB). However, the volume expansion of the RP anode reached 350 % during the intercalation/deintercalation of Li-ion processes, resulting in the detachment of active material and poor specific capacity. Herein, flexible hollow nanochannel carbon nanofiber was prepared through simple electrospinning, then P/GeP nano powder were encapsulated in the N-rich carbon nanofiber using a facile in situ synthesis method, where the introduction of GeP not only innovatively served as the high conductive dispersant for P, but simultaneously acted as the active component in reacting with Li-ion. The unique designed nanoarchitecture not only boosted the structural stability and electronic conductivity of the hybrid composite, but also facilitated the transport of electrons and Li-ion. Upon served as free-standing LiB anode, the N-doped hollow carbon fiber encapsulate P/GeP (P/GeP/C) anode displayed remarkably reversible capacities, superior rate performances, and long-term cycle stability for lithium storage. For instance, P/GeP/C of only 10.6 wt% GeP and 28.5 wt% P delivered 290.2 mA h g−1 under a high current density of 5 A g−1 and showed a high capacity of 575.6 and 436.9 mA h g−1 at a current density of 0.1 A g−1 and 1.0 A g−1 after 50 cycles, respectively.

Phosphorus/nitrogen co-doped hollow carbon fibers enabling high-rate potassium storage

Phosphorus/nitrogen co-doped hollow carbon fibers enabling high-rate potassium storage

Engineering CSFe Bond Confinement Effect to Stabilize Metallic-Phase Sulfide for High Power Density Sodium-Ion Batteries.

Metallic-phase iron sulfide (e.g., Fe7 S8 ) is a promising candidate for high power density sodium storage anode due to the inherent metal electronic conductivity and unhindered sodium-ion diffusion kinetics. Nevertheless, long-cycle stability can not be achieved simultaneously while designing a fast-charging Fe7 S8 -based anode. Herein, Fe7 S8 encapsulated in carbon-sulfur bonds doped hollow carbon fibers (NHCFs-S-Fe7 S8 ) is designed and synthesized for sodium-ion storage. The NHCFs-S-Fe7 S8 including metallic-phase Fe7 S8 embrace higher electron specific conductivity, electrochemical reversibility, and fast sodium-ion diffusion. Moreover, the carbonaceous fibers with polar CSFe bonds of NHCFs-S-Fe7 S8 exhibit a fixed confinement effect for electrochemical conversion intermediates contributing to long cycle life. In conclusion, combined with theoretical study and experimental analysis, the multinomial optimized NHCFs-S-Fe7 S8 is demonstrated to integrate a suitable structure for higher capacity, fast charging, and longer cycle life. The full cell shows a power density of 1639.6Wkg-1 and an energy density of 204.5Whkg-1 , respectively, over 120 long cycles of stability at 1.1Ag-1 . The underlying mechanism of metal sulfide structure engineering is revealed by in-depth analysis, which provides constructive guidance for designing the next generation of durable high-power density sodium storage anodes.

Near-perfect suppression of Li dendrite growth by novel porous hollow carbon fibers embedded with ZnO nanoparticles as stable and efficient anode for Li metal batteries

For the practical application of next-generation Li metal batteries (LMBs), a Li metal anode with high safety and efficiency is essential. However, LMBs still suffer from the problems caused by the growth of Li dendrites at the Li metal anode. In this study, we introduce a novel way that could dramatically suppress the growth of Li dendrites and improve the performance of LMBs. A free-standing porous hollow carbon nanofiber embedded with lithiophilic ZnO nanoparticles (P-HCNF@ZnO) is fabricated using a dual-nozzle electrospinning technique followed by carbonization. The nano-sized pores formed in the shell of hollow carbon fiber provide passages for Li ions to penetrate into the core space of the hollow fiber, and the lithiophilic ZnO particles play a decisive role in inducing and plating Li ions inside the core efficiently and uniformly. Therefore, Li ions are mostly electroplated/stripped on the internal surface of the porous hollow fibers and dendrites are rarely formed on their exterior surface even under fast lithiation conditions, while numerous Li dendrites are formed on the exterior surface of the non-porous hollow fiber electrode (HCNF@ZnO). As a result, the P-HCNF@ZnO electrode exhibits a very low over-potential of about 87 mV, a stable capacity retention of about 95% at a high current density of 1.0 mA cm−2, and a much higher performance than HCNF@ZnO in a symmetric cell test. Furthermore, in full cell tests, the LiFePO4 (LFP) battery made of lithiated P-HCNF@ZnO anode exhibits a high capacity of 175.3 mAh g−1 and a lower over-potential by 0.29 V than the reference sample. Analytical works and theoretical interpretations, elucidated that the Li metal anode made of the P-HCNF@ZnO significantly improves the performance of LMBs.

Multi-channel cellular carbon fiber as electrode for Zn-ion hybrid capacitor with enhanced capacity and energy density

Zn-ion hybrid capacitors (ZICs) recently receive an extensive attention owning to their theoretical energy density as well as high safety. Hollow porous carbon fibers (HPCF) are used as a promising cathode for ZICs due to abundant active sites. However, it is hard to deal with the “trade-off” between defect design and graphitic degree in HPCF electrode. In this work, hollow porous carbon fiber (HPCF) cathodes are prepared via a spinning-co-foaming technique, followed by zinc oxide nanoparticles as template and activation process. The aligned channels and hierarchical cavities in HPCF wall provide a high-speed diffusion path for electrolyte penetration via capillary force. Meanwhile, due to higher exposed surface area and metal-catalytic effect of reduce zinc during pyrolysis, self-standing ZHPCF-5 exhibits a good graphitic degree (ID/IG = 0.84). Its high electrical conductivity (158.3 S m−1) provides fast electron transport. The optimized ZHPCF-5 cathode displays a capacity of 220 mAh g−1 at 0.2 A g−1 and an energy density of 224 Wh kg−1 at a 14400 W kg−1 of power density. The assembled quasi-solid-state self-standing ZIC exhibits a high capacity (153.5 mAh g−1 at 0.5 A g−1). This work finds a way to simultaneously maintain abundant defects and high electric conductivity in self-standing carbon electrode for boosting Zn2+ storage.

Cobalt nanoparticles-embedded porous carbon nanocages uniformly dispersed hollow carbon fibers as the accelerated electrocatalysts toward water splitting

The fast, low-cost, and efficient design of zeolite imidazolate frameworks (ZIF) based derivatives with perfect hollow channels is an effective method for enhancing their full water-splitting catalytic activities and achieving their commercial use. In this study, the novel cobalt nanoparticles embedded in nitrogen-doped porous carbon nanocages uniformly dispersed over two curved surfaces of biomass-derived hollow carbon fibers (Co@NC nanocage/HCF) were synthesized via the carbonization of the ZIF-67/hollow biomass fiber precursors. After the usage amounts of biomass fibers were optimized, the optimal Co@NC nanocage/HCF200 exhibited a larger surface area and higher dispersion states of Co@NC nanocages than the tightly packed pure Co@NC nanocages. Particularly, owing to the hollow and porous structures of Co@NC nanocages, more electrocatalytic active centers (i.e. the pyridinic-N, Co-Nx-C, pyrrolic-N, graphitic-N, high-valence Co, and other oxygen-containing functional groups) were exposed along surfaces of the Co@NC nanocage/HCF200 catalyst. In an alkaline solution, the hydrogen evolution reaction potential at 10 mA cm−2 for Co@NC nanocage/HCF200 was 165 mV more negative than that of 20 wt% Pt/C. Particularly, the oxygen evolution reaction potential at 10 mA cm−2 for Co@NC nanocage/HCF200 was 17 mV more negative than that of RuO2. For overall water splitting, the bifunctional Co@NC nanocage/HCF200 catalyst-based electrolysis cell achieved a current density of 10 mA cm−2 at a cell voltage of 1.618 V, which is 4 mV smaller than that of the state-of-the-art 20 wt% Pt/C||RuO2 cell (1.614 V). The perfect hollow and porous structures, uniformly dispersed Co@NC nanocages (locked by vast in situ formed carbon nanotubes), and abundant electrocatalytic active sites along the inner and outer surfaces of Co@NC nanocage/HCF200 contributed to the excellent water splitting catalysis. Particularly, owing to the excellent stabilities of hollow structures and uniformly dispersed porous Co@NC nanocages, the Co@NC nanocage/HCF200 exhibited higher stability toward water electrolysis.

Nitrogen doped hollow porous carbon fibers derived from polyacrylonitrile for Li-S batteries

Hollow porous carbon fibers for Li-S battery electrodes were prepared by the KOH activation of carbon prepared from hollow polyacrylonitrile fibers. The fibers had a high specific surface area of 2 491 m2·g−1, a large pore volume of 1.22 cm3·g−1 and an initial specific capacity of 330 mAh·g−1 at a current density of 1 C. To improve their electrochemical performance, the fibers were modified by treatment with hydrazine hydrate to prepare nitrogen-doped hollow porous carbon fibers with a specific surface area of 1 690 m2·g−1, a pore volume of 0.84 cm3·g−1 and a high nitrogen content of 8.81 at%. Because of the increased polarity and adsorption capacity produced by the nitrogen doping, the initial specific capacity of the fibers was increased to 420 mAh·g−1 at a current density of 1 C.

Directional fiber framework wrapped by graphene flakes for supporting phase change material with fast thermal energy storage properties

Organic phase change materials (PCMs) have low thermal conductivity and poor form stability, which prohibit their usage in high-efficient heat storage and thermal management. This study demonstrated how to efficiently fabricate phase change composites (PCCs) with directional thermal conductivity and good form stability using vertically aligned carbon fibers as supporting scaffolds. Cotton blankets with aligned fibers were firstly impregnated with graphene flake solutions, which were then rolled to columns along the fiber direction and subsequently carbonized to obtain the porous carbon fiber scaffolds. PCCs were prepared by vacuum impregnation of paraffin into the scaffolds. The porous scaffolds supported PCCs showed good shape stability and greatly improved thermal transfer properties, which were especially endowed with a directional heat conductivity as a result of the vertically arranged hollow carbon fiber structure. The thermal conductivity of PCCs along the axial direction of the fibers was greater than along the lateral direction, because the arranged fibers provided the majority of the thermal transfer path in PCCs. With a carbon content of 19.46 wt%, the axial thermal conductivity was 2.13 W K−1 m−1, which was twice of the lateral one and 8.5 times of the PW. Last but not least, the PCCs also possessed high latent heat capacity, high thermal cycling and chemical stability. These results suggest that the novel carbon scaffolds may enable PCCs with directionally improved thermal transfer properties.

Surface iodine modification inducing robust CEI enables ultra-stable Li-Se batteries

Lithium-selenium batteries (LSeBs) have attracted increasing attention due to their excellent electronic conductivity and high theoretical specific capacity. However, there are still difficult problems such as low utilization rate and fast capacity decay in the actual application process. Herein, a surface iodine modified three-dimensional (3D) nano hollow carbon fiber (I-NHCF) network is designed and synthesized as Se host (Se@I-NHCF) for highly stable LSeBs. The surface iodine species induce the formation of robust cathode electrolyte interface (CEI), thus preventing the transformation of amorphous selenium to low-activity crystalline selenium and enabling stable electrochemical performance. Moreover, the surface iodine species promote rapid charge transfer, enhancing the chemical reaction kinetics and improving the utilization of the active Se species. As a result, the Se@I-NHCF cathode exhibits superior specific capacity of 581.8 mAh g−1 with a high stability (0.0054% capacity decay per cycle) after 500 cycles at 1C, and an excellent rate performance of 567.6 mAh g−1 at 2C. This work addresses the problem of rapid capacity decay by the formation of uniform and robust CEI to conserve highly reactive amorphous Se species, improve Se utilization, and achieve ultra-stable Li-Se batteries with high energy and long cycle life.