Carbon Nanofiber Network Research Articles

Multimodal Capacitive and Piezoresistive Sensor for Simultaneous Measurement of Multiple Forces.

Quantitative information on the magnitudes and directions of multiple contacting forces is crucial for a wide range of applications including human-robot interaction, prosthetics, and bionic hands. Herein we report a highly stretchable sensor integrating capacitive and piezoresistive mechanisms that can simultaneously determine multiple forces. The sensor consists of three layers in a sandwich design. The two facesheets serve as both piezoresistive sensors and electrodes for the capacitive sensor, with the core being a porous structure made by using a simple sugar particle template technique to give them high stretchability. The two facesheets contain segregated conductive networks of silver nanowires (AgNWs) and carbon nanofibers (CNFs). By measuring the changes in the electrical resistance of the facesheets and the capacitance between the facesheets, three separate mechanical stimuli can be determined, including normal pressure, in-plane stretch, and transverse shear force. The newly developed multidirectional sensor offers a significant opportunity for the next generation of wearable sensors for human health monitoring and bionic skin for robots.

Mechanical, Electrical, and Piezoresistive Sensing Characteristics of Epoxy-Based Composites Incorporating Hybridized Networks of Carbon Nanotubes, Graphene, Carbon Nanofibers, or Graphite Nanoplatelets.

The present study compared the mechanical, electrical, morphological, and piezoresistive characteristics of epoxy-based sensing nanocomposites fabricated with inclusions of hybridized networks of four different carbon nanomaterials (CNMs), such as carbon nanotube (CNT), graphene, carbon nanofiber (CNF), and graphite nanoplatelet (GNP). Enhancements in elastic modulus and electrical conductivity were achieved by CNT–graphene composites and CNT–CNF composites, and these were explained by the morphological observations carried out in the present study and experimental studies found in the literature. The greatest gauge factor was accomplished by the CNT–GNP composite, followed by the CNT–CNF composite among composites where the CNM networks were sufficiently formed with a content ratio of 3%. The two types of the composites outperformed the composites incorporating solely CNT in terms of gauge factor, and this superiority was explained with the excluded volume theory.

Porous electrospun carbon nanofibers network as an integrated electrode@gas diffusion layer for high temperature polymer electrolyte membrane fuel cells

High temperature polymer electrolyte membrane fuel cells (HT-PEMFCs) utilize phosphoric acid imbibed polybenzimide membranes, which allow for improved reaction kinetics due to the higher operating temperatures, but suffer from the corrosive environment and the sluggish oxygen transport and associated transport limitations. The latter issue is addressed in this work by the integration of the gas diffusion layer (GDL) into the gas diffusion electrode (GDE) in an entirely electrospun concept. For this purpose, coaxial electrospinning is applied by spinning two immiscible polymer solutions simultaneously to create a core-shell structure. Porous carbon felt structures are obtained due to phase separation in the shell and a subsequent carbonization treatment (integrated GDE@GDL). Full cell tests (0.6 mgPt cm−2) demonstrate a 21% increase in the power density normalized to the platinum content compared to the spray-coated reference (1 mgPt cm−2). Electrochemical impedance spectroscopy (EIS) measurements coupled with the distribution of relaxation times (DRT) analysis show that the morphology of the GDE@GDL favors oxygen transport inside the electrode. Mass transport limitations were successfully remedied by our electrospun concept rendering an additional GDL sheet obsolete.

Scalable Alignment and Selective Deposition of Nanoparticles for Multifunctional Sensor Applications.

Here reported is the layer-by-layer-based advanced manufacturing that yields a simple, novel, and cost-effective technique for generating selective nanoparticle deposition and orientation in the form of well-controlled patterns. The surface roughness of the three-dimensionally printed patterns and the solid-liquid-air contact line, as well as the nanoparticle interactions in dipped suspensions, determine the carbon nanofiber (CNF) alignment, while the presence of triangular grooves supports the pinning of the meniscus, resulting in a configuration consisting of alternating CNF and polymer channels. The polymer/nanoparticle composites show 10 times lower resistance along with the particle alignment direction than the randomly distributed CNF networks and 6 orders of magnitude lower than that along the transverse direction. The unidirectional alignment of the CNF also demonstrates linear piezoresistivity behavior under small strain deformation along with high sensitivity and selectivity toward volatile organic compounds. The reported advanced manufacturing shows broad applications in microelectronics, energy transport, light composites, and multifunctional sensors.

Designed Assembly of Porous Cobalt Oxide/Carbon Nanotentacles on Electrospun Hollow Carbon Nanofibers Network for Supercapacitor

Porous and hollow nanomaterials have been an exciting research area for numerous next-generation technological applications. However, it is still a challenge to assemble porous and hollow nanostruc...

Synergistic Cu/CeO2 carbon nanofiber catalysts for efficient CO2 electroreduction

The electrochemical reduction of carbon dioxide (CO2RR) has attracted enormous interest because of the energy crisis and climate change; however, more efficient catalysts are required for practical applications. Herein, we present electrospinning as a facile strategy to synthesize a three-dimensional network of carbon nanofibers embedded with Cu and CeOx nanoparticles (Cu/CeOx@CNFs) as a CO2RR catalyst. The Cu–CeOx interface produced using this method offers synergistic geometric and electronic effects which optimize the adsorption strength of reaction intermediates for the electroreduction of CO2 to CO. In a flow cell configuration, a current density of 100 mA cm−2 and a CO faradaic efficiency of 59.2% can be obtained at −0.60 V vs. RHE.

Tunable confinement of Cu-Zn bimetallic oxides in carbon nanofiber networks by thermal diffusion for lithium-ion battery

In terms of solving the phase separation of metal oxides and polymer derived carbon matrix during the carbonization process, two active metal oxides with different thermal diffusion features are simultaneously introduced. The agglomeration and migration of copper-based species during the carbonization process are well suppressed by the existence of homogenous ZnO distributed in carbon matrix with less migration ability. The unique carbon-confined Cu-Zn bimetallic oxides films are constructed via a facile electrospinning method and subsequently annealing process. Taking advantage of the suppressive effect of ZnO, the agglomeration and migration of copper-based particles are restrained and thus realizes the size regulation of Cu2O/Cu particles as well as the confinement in carbon nanofibers. Our designed architecture not only maintains the intrinsic interface properties of carbon nanofiber, but also distinctively enhances a highly reversible lithium-ion storage nature. Moreover, the preparation technique can be applied for constructing self-supported flexible electrodes without the additional current collector, seasonably satisfying the requirement of flexible electronics industry and effectively avoiding the employment of superfluous electrode redundancy.

Robust Superhydrophobic Composite Featuring Three-Dimensional Porous Metal Rubber with an Embedded Carbon Nanofiber Network for Emulsion Separation

With increasing environmental pollution, super-wetting materials for emulsion separation have attracted considerable attention in recent years. However, there are still major challenges in separati...

Electrode Design for High-Performance Sodium-Ion Batteries: Coupling Nanorod-Assembled Na3V2(PO4)3@C Microspheres with a 3D Conductive Charge Transport Network.

As one of the most promising cathodes for sodium-ion batteries, the polyanionic compounds still suffer from unsatisfactory capacity and rate performance resulting from poor electron conductivity. Furthermore, the charge-transfer kinetics, especially for Na+, becomes limiting as the mass loading increases. Herein, a robust free-standing electrode coupling optimal porous Na3V2(PO4)3@C microspheres with a bicontinuous charge transport network is designed and prepared by a simple casting method. In the design, the optimal porous carbon-coated microspheres, composed of some continuous nanorods, along with interwoven carbon nanofiber networks offer efficient electron transport and facile ion diffusion. Such an elaborate design enables impressive electron/ion conductivity, contributing to remarkable rate performance (116.1 mA h g-1 at 0.2 C; 96 mA h g-1 at 30 C) and outstanding cycling stability (90% capacity retention in 500 cycles at 1 C; 80% capacity retention in 5000 cycles at 10 C), which has surpassed other similar Na3V2(PO4)3-based free-standing electrodes as reported. More importantly, when mass loading extends to 8 mg cm-2, an excellent capacity retention of 75% at 10 C can be obtained. The research offers a new avenue into the rational design of porous microspheres electrode with high conductive charge transport network, indicating its superiority in practical applications.

A carbon‐nanofiber glass composite with high electrical conductivity

AbstractThe use of oxide glasses is pervasive throughout everyday amenities and commodities. Such glasses are typically electrical insulators, and endowing them with electrical conductivity—without changing their salutary mechanical properties, weight, or thermoformability—enables new applications in multifunctional utensils, smart windows, and automotive parts. Previous strategies to impart electrical conductivity include modifying the glass composition or forming a solid‐in‐solid composite of the glass and a conductive phase. Here, we demonstrate—using the latter strategy—the highest reported room‐temperature electrical conductivity in a bulk oxide glass (~1800 S/m) corresponding to the theoretical limit for the loading fraction of the conductive phase. This is achieved through glass sintering of a mixture of carbon nanofibers (CNFs) and oxide flint (F2) or soda‐lime glasses, with the bulk conductivity further enhanced by a polyethylene‐block‐poly(ethylene glycol) additive. A theoretical model provides predictions that are in excellent agreement with the dependence of conductivity of these composites on the carbon‐loading fraction. Moreover, nanoscale electrical characterization of the composite samples provides evidence for the existence of a connected network of CNFs throughout the bulk. Our results establish a potentially low‐cost approach for producing large volumes of highly conductive glass independently of the glass composition.

Electrospun three-dimensional cobalt decorated nitrogen doped carbon nanofibers network as freestanding electrode for lithium/sulfur batteries

Cobalt decorated nitrogen doped carbon nanofibers (Co, N-CNFs) were successfully fabricated by electrospinning technique based the cobalt based zeolitic-imidazolate frameworks-67 (ZIF-67)/PAN solution as precursor. The as-synthesize fibrous Co, N-CNFs membrane was employed as positive current collector containing Li2S6 catholyte solution for lithium sulfur batteries. Co, N-CNFs inhibited the dissolution of polysulfides shuttle effect and demonstrated as positive catalyst accelerating kinetic redox reaction of lithium polysulfides/sulfide. In addition, metallic cobalt achieves the purpose of reducing polarization and increasing specific capacity by promoting nucleation of lithium sulfide on the surface of Co, N-CNFs. Li2S6 catholyte impregnated Co, N-CNFs electrode (sulfur loading: 4.74 mg) exhibits the first discharge capacity of 1166 mA h g−1 and matins at 938 mA h g−1 after 300 cycles at 0.2 C, which is superior cycling performance than N-CNFs. Even at 7.11 mg sulfur loading, the composite electrode shows a high area capacity of 6.47 mA h cm−2. Furthermore, a steady-state of lithium anode resulting through effective suppression of polysulfide shuttle effect is also demonstrated to contribute significantly to enhance electrochemical performance.

Unique three-dimensional Co3O4@N-CNFs derived from ZIFs and bacterial cellulose as advanced anode for sodium-ion batteries

A novel strategy is exploited herein to fabricate zeolitic-imidazolate frameworks (ZIFs) and bacterial cellulose-derived Co3O4 nanoparticles anchored on three-dimensional nitrogen-doped carbon nanofibers (Co3O4@N-CNFs) network by simply growing ZIFs on bacterial cellulose and then applying a two-step annealing process. When utilized as an anode for sodium ion batteries, the as-fabricated Co3O4@N-CNFs electrode exhibits a high capacity (864.2 mA h g−1 for the first discharge and 450.2 mA h g−1 after 50 cycles at 100 mA g−1), excellent rate performance, and an ultralong cycling life stability (220.1 mA h g−1 at 1.6 A g−1 after 1000 cycles), which are better than those of other ZIF-derived cobalt-based oxide composites. The excellent capability can be ascribed to the synergistic effect between the Co3O4 polyhedrons and carbon nanofibers network, in which the unique interconnected nanostructures can decrease the ion diffusion route and enhance the conductivity and structural stability. These results indicate that the as-fabricated Co3O4@N-CNFs can be a promising anode material for high-performance sodium ion batteries. The present strategy for Co3O4@N-CNFs architectures can provide a promising approach for other metal-organic framework-derived materials for high-performance energy storage equipment.

N- & S-co-doped carbon nanofiber network embedded with ultrafine NiCo nanoalloy for efficient oxygen electrocatalysis and Zn-air batteries.

A novel 3D N- & S-co-doped carbon nanofiber network embedded with ultrafine NiCo oxide nanoparticles is explored by a facile surfactant-assisted electrospinning method. This catalyst has several structural advantages including ultrafine active sites (2-8 nm), hierarchical pores, and abundant defects, allowing for much higher OER/ORR activity compared to commercial IrO2 and Pt/C catalysts. The potential gap (ΔE) of OER and ORR metrics for NSCFs/Ni-Co-NiCo2O is 0.69 V and the Zn-air battery equipped with NSCFs/Ni-Co-NiCo2O as the air cathode delivers a maximum power density of 171.24 mW cm-2 at 268 mA cm-2. Furthermore, the unique structure of the 3D carbon nanofiber network embedded with ultrafine nanoparticles results in superior stability with negligible degradation in activity after 380 h of continuous operation.

Universal construction of ultrafine metal oxides coupled in N-enriched 3D carbon nanofibers for high-performance lithium/sodium storage

To develop high-performance lithium/sodium-ion batteries, new method for the mass production of distinctive nanomaterials with ultrafine transition metal oxides intimately coupled in 3D carbon matrix still remains challenging. Herein, a universal strategy for synthesizing ultrafine metal oxide quantum dots (3–6 nm) tightly embedded in nitrogen-enriched 3D carbon nanofiber networks {MO@NCFs (MO = Co3O4, Mn3O4, Fe3O4)} is reported in a scalable manner. The MO@NCFs are constructed by coordinating nanofibrous carboxymethyl chitosan (CMCh) hydrogels and metal ions to form a stable metal-polysaccharide framework, and then by pyrolyzing process to generate hierarchically porous structure. The in situ and confined coordination in the CMCh framework can not only generate the metal oxides quantum dots with ultrafine size, but also endow the quantum dots to be robustly embedded in N-enriched 3D carbon nanofiber networks, leading to fast electron and ion transport, and excellent structural stability. As expected, the Co3O4@ NCFs exhibit a high Li+ storage capacity of 1199 mAh g−1 at 200 mA g−1, and a good cycling lifespan with capacity retention of 721 mAh g−1 at 1000 mA g−1 after 400 discharge/charge cycles. For sodium storage, the Co3O4@NCFs display superior capacities of 645 mAh g−1 at 100 mA g−1, good rate capability (191 mAh g−1 at 4000 mA g−1), and remarkable capacity retention of 301 mAh g−1 at 1000 mA g−1 after 400 cycles. This work provides a facile pathway to construct firmly coupled carbon hybrids by utilizing sustainable polymers derived from seafood waste for enhancing energy storage.

Enhancement of charge transport in porous carbon nanofiber networks via ZIF-8-enabled welding for flexible supercapacitors

Lightweight, self-supporting, and flexible carbon nanofiber membranes are desirable electrode candidates for flexible supercapacitors. At present, inadequate electrical contact between adjacent nanofibers, poor wettability with electrolyte, and limited specific surface area are still challenges for further improving the capacitive property. In this work, a novel porous N-doped carbon nanofiber network membrane in which continuous ZIF-8-derived carbon layers “welding” adjacent carbon nanofibers is synthesized through bifunctional ZnO nanoparticles contained in the nanofibers. Here, ZnO nanoparticles not only serve as the pore-forming agent to create multiscale pores, but also provide zinc sources for in-situ growth of ZIF-8 nanoparticle layer. Because of highly interconnected networks, special spider-web-like surface nanostructure, and hierarchical pores, the as-prepared carbon membrane reveals superior electrical conductivity, high specific surface area and excellent wettability. An excellent rate performance with 75.5% capacitance retention even with 70-times current density increase and extraordinary cycling stability (98.8% capacitance retention after 100,000 cycles at 10 A g−1) could be found, when the optimized hierarchically porous N-doped welded carbon network membrane is used as the electrode. The quantitatively electrochemical kinetic analysis of the electrode indicates that fast double layer capacitive behavior is dominant at high current densities. Meanwhile, the flexible quasi-solid-state devices display excellent electrochemical stability in severely bending states.

Nitrogen-doped Carbon Nanofibers Network Derived from Bacterial Cellulose for the Oxygen Reduction Reaction

3D N-doped carbonized bacterial cellulose (NCBC) networks are successfully prepared through carbonizing a bacterial cellulose (BC) and urea mixture. The resultant optimized NCBC samples obtained at...

Metal–organic-frameworks-engaged formation of Co0.85Se@C nanoboxes embedded in carbon nanofibers film for enhanced potassium-ion storage

Potassium-ion batteries (PIBs) are considered as viable energy storage system due to the abundance and low cost of potassium. However, their development is still hampered by the lack of suitable electrode materials that can withstand the structural deterioration caused during intercalation/deintercalation of large potassium ions. Herein, a flexible and freestanding anode material consisting of Co0.85Se@carbon nanoboxes (Co0.85Se@C) embedded in carbon nanofibers films is fabricated through a metal‒organic-framework-engaged electrospinning strategy coupled to a one-step confined carbonization-selenidation process. The rationally designed electrode with high mass loading of active material offers attractive structural features, particularly Co0.85Se@C nanoboxes with large surface area and requisite void space to accommodate the large volumetric expansion for boosted cycling stability. Moreover, the robust conductive carbon nanofiber network not only improves the electronic conductivity, but also stabilizes the integral structure upon repeated K+ insertion/deinsertion. As a result, this unique nanoarchitecture demonstrates excellent cycling stability as an anode material for PIBs, with a high reversible capacity of 299 mA h g−1 at 1 A g−1 after 400 cycles and achieves remarkable rate performance with a specific capacity of 166 mA h g−1 at 5 A g−1. Most importantly, it is demonstrated that increasing the areal loading of active material in the electrode through a layer-by-layer stacking configuration further improves the energy density of the battery.

Carbon shell encapsulated cobalt phosphide nanoparticles embedded in carbon nanotubes supported on carbon nanofibers: A promising anode for potassium ion battery

Despite transition metal phosphide (TMP)-based hybrid structures demonstrating desirable results for potassium ion battery applications, most of their preparation methods require complex multi-step procedures. Herein, a three-dimensional (3D) structural material in which amorphous carbon (AC) encapsulated CoP nanoparticles are embedded at the top of nitrogen-doped carbon nanotubes derived from ZIF-67/ZIF-8 grown on the surface of carbon nanofibers (AC@CoP/NCNTs/CNFs) is reported for the first time. The CoP acts as a core and the amorphous carbon layer acts as a shell, which restrains the volume expansion of active materials during charging and discharging. Furthermore, the carbon nanofiber network can improve the conductivity, and doped nitrogen can increase active sites. As a result, the electrochemical properties of the potassium ion battery are enhanced when an AC@CoP/NCNTs/CNFs nanocomposite is used as the anode electrode, and the electrode exhibits a reversible capacity of 247 mA h g−1 after 1000 cycles at 0.8 A g−1 in a potassium ion battery.

Free-Standing and Heteroatoms-Doped Carbon Nanofiber Networks as a Binder-Free Flexible Electrode for High-Performance Supercapacitors.

Flexible and heteroatoms-doped (N, O and P) activated carbon nanofiber networks (ACFNs) have been successfully prepared with a mixture of polyamic acid (PAA) and poly(diaryloxyphosphazene) (PDPP) as a solution through electrospinning, followed by a heat post-treatment. The resultant heteroatoms-doped ACFNs can be used as binder-free electrodes for high-performance flexible supercapacitors (SCs) due to lightweight, three-dimensional open-pore structure and good mechanical strength. Despite its surface area being lower than 130.6 m2·g−1, the heteroatoms-doped ACFNs exhibited a high heteroatoms (N, O and P) content of 17.9%, resulting in a highly specific capacitance of 182 F·g−1 at a current density of 1 A·g−1 in 6 M KOH electrolyte in a two-electrode cell and an excellent rate capability of 74.7% of its initial capacitance from 1 A·g−1 to 10 A·g−1 under the mass loading of 1.5 mg·cm−2. The electrical double-layer (EDL) capacitance and pseudocapacitance can be easily decoupled in the heteroatoms-doped mesoporous ACFNs. SCs device based on heteroatoms-doped ACFNs exhibited a high energy density of 6.3 W·h·kg−1 with a power density of 250 W·kg−1, as well as excellent cycling stability with 88% capacitance retention after 10,000 charge–discharge cycles. The excellent electrochemical performance was attributed to the mesoporous structure of ACFNs and pseudocapacitive heteroatoms.

Free-standing dual-network red phosphorus@porous multichannel carbon nanofibers/carbon nanotubes as a stable anode for lithium-ion batteries

Red phosphorus (P) suffers from dramatic capacity decay and poor conductivity as anodes for lithium-ion batteries (LIBs). Recently, the composite material made of red phosphorus and carbon matrix has become the mainstream route to solve these problems. In this work, we prepared a free-standing flexible P/C electrode by encapsulating phosphorus in a dual-conducting network of porous multichannel carbon nanofibers and in-situ carbon nanotubes (denoted as P@PMCNFs/CNTs) to achieve electrode conductivity and cycle stability. The nano-sized red P is adsorbed in three-dimensional carbon network and channel according to strong P–C chemical bond adsorption energy. Furthermore, the free-standing electrode can make full use of the overall capacity of the material and avoid inactive additives, which improving the overall volume functional density. When used as anodes for LIBs, the prepared free-standing P@PMCNFs/CNTs electrode shows excellent rate capability (601 mA h g−1 at 3 A g−1), cycle stability (802.3 mA h g−1 at 1 A g−1 after 500 cycle), and a surface-dominated contribution (70.2%).