Graphite Nanofibers Research Articles

Electrospinning preparation of g-C3N4/Nb2O5 nanofibers heterojunction for enhanced photocatalytic degradation of organic pollutants in water

In this study, graphitic carbon nitride (g-C3N4) and niobium pentoxide nanofibers (Nb2O5 NFs) heterojunction was prepared by means of a direct electrospinning approach combined with calcination process. The characterizations confirmed a well-defined morphology of the g-C3N4/Nb2O5 heterojunction in which Nb2O5 NFs were tightly attached onto g-C3N4 nanosheets. Compared to pure g-C3N4 and Nb2O5 NFs, the as-prepared g-C3N4/Nb2O5 heterojunction exhibited remarkably enhanced photocatalytic activity for degradation of rhodamine B and phenol under visible light irradiation. The enhanced catalytic activity was attributed predominantly to the synergistic effect between g-C3N4 sheets and Nb2O5 NFs, which promoted the transferring of carriers and prohibited their recombination, confirmed by the measurement of transient photocurrent responses and photoluminescence spectra. In addition, the active species trapping experiments indicated that superoxide radical anion (·O2–) and hole (h+) were the major active species contributing to the photocatalytic process. With its high efficacy and ease of preparation, g-C3N4/Nb2O5 heterojunction has great potentials for applications in treatment of organic pollutants and conversion of solar energy.

Thermal conductivity of graphite nanofibers electrospun from graphene oxide-doped polyimide

Thermal conductivity of graphite nanofibers electrospun from graphene oxide-doped polyimide

Preparation of N-doped graphitic carbon nanofibers composites via pyrolysis strategy and its application in the antibiotics treatment

In this study, we employed carbon nanofibers (CNFs) and melamine-formaldehyde resin-based N-doped graphitic carbon spheres (MFC) as precursor to prepare N-doped graphitic carbon nanofibers composites (CNFs-@-MFC) through pyrolysis strategies under nitrogen atmosphere. Compared with CNFs, the incorporation of MFC made CNFs-@-MFC have superior specific surface area (1295.33 m2 g−1), higher percent of nitrogen content (4.33%) and abundant porous structures, resulting in highly-efficient removal of tetracycline hydrochloride (TC) and ciprofloxacin (CIP). The maximum adsorption capacity of CNFs-@-MFC towards TC and CIP were 546.5 mg/g and 549.6 mg/g, respectively. In addition, the CNFs-@-MFC still maintain good adsorption performances towards pollutants after 5 cycles. The adsorptive mechanism studies indicated that the hydrogen bonding, pore capture and π-π interaction played the main functions in the antibiotics adsorption process by CNFs-@-MFC. This study not only provided a novel strategy to prepare the highly-efficient porous N-doped graphitic carbon nanofibers, but also evaluated the application prospect of the absorbent for antibiotics removal.

Thermal conductivity of graphite nanofibers electrospun from graphene oxide-doped polyimide

Aromatic polyimide (PI)-based graphite nanofibers were obtained from the graphitization of graphene oxide (GO)-doped electrospun PI nanofibers. GO improves the PI molecular orientation, crystalline structure and thermal conductivity of the resulting nanofibers. The degree of PI molecular orientation in the nanofibers is increased by the GO during fiber preparation. This improvement in molecular orientation produces an increase in the thermal conductivity of the graphite nanofibers, and the addition of only 0.1% GO has a significant effect. The GO not only affects the thermal conductivity, but improves the PI molecular orientation and its role as nucleation centers during graphitization. This approach and the resulting high thermal conductivity materials show great potential for practical applications.

Herring bone graphitic nanofibers grown on NiFe-silica nanocomposites by CVD method for HER activity in alkaline media

Replacement of platinum-based electrocatalytic materials by earth abundant counterparts for hydrogen evolution reaction (HER) in alkaline media is highly desirable. In this work we report synthesis of unique morphology graphitic nanofibers resembling to herring bone graphitic nanofibers (H-GNFs) by typical CVD method at growth temperature of 650 °C employing NiFe-silica nanocomposites as a nanocatalyst followed by its application in HER activity. The electrochemical performance of NiFe grown H-GNFs shows that it is far better electrocatalyst than bare nickel foam substrate in terms of overpotential, Tafel slope and charge transfer resistance. The grown H-GNF electrocatalytic material shows overpotential of 95 mV at current density of 10 mA/cm2 which is just 46 mV higher than commercial Pt/C (20 wt% Pt) and lower than many reported HER electrocatalyst in alkaline conditions.

Graphitic nanofibers supported NiMn bimetallic nanoalloys as catalysts for H2 generation from ammonia borane

Bimetallic nickel manganese nanoalloy-decorated graphitic nanofibers were prepared using electrospinning. The introduced catalysts were explored as an effective and inexpensive catalyst for H2 generation from ammonia borane using hydrolysis. Standard techniques were used to determine the morphology and chemical composition of the nanofibers. Characterization indicated successful formation of bimetallic nickel-manganese-decorated graphitic nanofibers. Introduced effective catalysts showed a high reusability for H2 generation using ammonia borane hydrolysis at low concentrations and temperatures. All formations of the introduced catalysts demonstrated a higher catalytic activity in H2 generation than nickel-decorated carbon nanofibers. Samples composed of 55 wt% nickel and 45 wt% manganese showed the best catalytic activity compared with other formulations. Initial turnover frequency (TOF) of this sample was 58.2 min−1, twice the TOF of the manganese-free catalyst. Kinetics and thermodynamics revealed that the catalyst concentration followed the pseudo-first order reaction while the ammonia borane concentration follow the pseudo-zero order reaction, providing activation energy of 38.9 kJ mol−1.

On the Physics and Atomic Mechanisms of Molecular Hydrogen Intercalation into Graphite Nanofibers

On the Physics and Atomic Mechanisms of Molecular Hydrogen Intercalation into Graphite Nanofibers

Reutilizing Methane Reforming Spent Catalysts as Efficient Overall Water-Splitting Electrocatalysts.

It is extremely prudent and highly challenging to design a greener bifunctional electrocatalyst that shows effective electrocatalytic activity and high stability toward electrochemical water splitting. As several hundred tons of catalysts are annually deactivated by deposition of carbon, herein, we came up with a strategy to reutilize spent methane reforming catalysts that were deactivated by the formation of graphitic carbon (GC) and carbon nanofibers (CNF). An electrocatalyst was successfully synthesized by in situ deposition of noble metal-free MoS2 over spent catalysts via a hydrothermal method that showed exceptional performance regarding the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). At 25 mA cm–2, phenomenal OER overpotentials (η25) of 128 and 154 mV and modest HER overpotentials of 186 and 207 mV were achieved for MoS2@CNF and MoS2@GC, respectively. Moreover, OER Tafel slopes of 41 and 71 mV dec–1 and HER Tafel slopes of 99 and 107 mV dec–1 were obtained for MoS2@CNF and MoS2@GC, respectively. Furthermore, the synthesized catalysts exhibited good long-term durability for about 18 h at 100 μA cm–2 with unnoticeable changes in the linear sweep voltammetry (LSV) curve of the HER after 1000 cycles. The carbon on the spent catalyst increased the conductivity, while MoS2 enhanced the electrocatalytic activity; hence, the synergistic effect of both materials resulted in enhanced electrocatalysts for overall water splitting. This work of synthesizing enhanced nanostructured electrocatalysts with minimal usage of inexpensive MoS2 gives a rationale for engineering potent greener electrocatalysts.

High energy Na-Ion capacitor employing graphitic carbon fibers from waste rubber with diglyme-based electrolyte

Co–intercalation process using glyme-based solvents has brought new prospects for the reversible Na-intercalation into the graphitic materials. We report a high-energy Na-ion capacitor (SIC) with graphitic carbon nanofibers (GCNF) as a battery-type component obtained from the depolymerization of waste rubber. The kinetic study reveals that ~ 51% contribution is originated from the diffusion-controlled Faradaic mechanism for GCNF compared to the ~ 61% for commercial graphite powder. The synthesis procedure and less crystalline nature of the GCNF lead to the lowered intercalation potential, and extended Na-ion storage capacity in the lower potential region (vs. Na+/Na) which is significant compared to the graphite powder. Further, the half-cell delivered a discharge capacity of ~ 118 mAh g−1 irrespective of the applied current rate, which signifies the importance of this concept. In a SIC configuration with activated carbon, the SIC renders an energy density of 55.58 Wh kg−1 at 25 °C. In addition, exceptional low-temperature performance (<10 °C) is noted with a maximum energy density of 54.69 Wh kg−1 and > 97% capacity retention after 5000 cycles. This low-temperature performance, high energy density, and exceptional cyclability certainly offer a unique hybrid charge storage system that eventually explores the possibility of using graphitic carbon fibers towards balanced energy and power capabilities. On a lighter note, this study also provides the opportunity to handle the waste materials effectively for sustained charge storage applications.

Graphitic biogas-derived nanofibers as cathodes for sodium dual-ion batteries: Intercalation of PF6− anions

The electrochemical intercalation of PF6− anions into graphitic nanomaterials of renewable origin with different degrees of structural order to be subsequently used as cathodes for sodium dual-ion batteries is herein investigated for the first time. Overall, the electrochemical performance of the biogas-derived carbon nanofibers depends on their graphitic structure, specifically on crystallite height which was found to be the determining parameter for the scope of electrochemical intercalation of PF6− anions into these nanomaterials.

An integrated separator/anode assembly based on electrospinning technique for advanced lithium-ion batteries

In this work, polyacrylonitrile (PAN) nanofiber separator is fabricated directly on the surface of the graphite anode of lithium-ion batteries, resulting in an integrated separator/anode assembly (SAA). On one hand, the porous structure and polar surface of PAN nanofiber separator enable the SAA with superior electrolyte affinity and wettability. On the other hand, the interlocking structure at the interface between graphite anode and nanofiber separator enhances the mechanical and thermal stabilities of the separator as well as the interface compatibility. As a result, the SAA possesses an electrolyte contact angle of about 0 o and a thermal shrinkage of less than 2% at 150 °C for 0.5 h, resulting from the coupling effect between nanofiber separator and graphite anode. The above advantages endow the LiCoO2/SAA full cell with better C-rate (capacity retention 44.3% at 32.0 C compared with that at 0.5 C) and cycling performances (capacity retention 98.0% after 200 cycles at 0.2 C) as well as higher thermal resistance compared with those of the common LiCoO2/polyolefin separator/graphite battery. Consequently, this work provides an advanced separator/anode assembly and the corresponding fabrication method, which may be a new strategy for improving the charge-discharge performance and assembly efficiency of lithium-ion batteries.

Synergetic Strategy for the Fabrication of Self-Standing Distorted Carbon Nanofibers with Heteroatom Doping for Sodium-Ion Batteries.

Currently, the limited availability of lithium sources is escalating the cost of lithium-ion batteries (LIBs). Considering the fluctuating economics of LIBs, sodium-ion batteries (SIBs) have now drawn attention because sodium is an earth-abundant, low-cost element that exhibits similar chemistry to that of LIBs. Despite developments in different anode materials, there still remain several challenges in SIBs, including lighter cell design for SIBs. The presented work designs a facile strategy to prepare nitrogen-doped free-standing pseudo-graphitic nanofibers via electrospinning. A structural and morphological study implies highly disordered graphitic structured nanofibers having diameters of ∼120–170 nm, with a smooth surface. X-ray photoelectron spectroscopy analysis showed that nitrogen was successfully doped in carbon nanofibers (CNFs). When served as an anode material for SIBs, the resultant material exhibits excellent sodium-ion storage properties in terms of long-term cycling stability and high rate capability. Notably, a binder-free self-standing CNF without a current collector was used as an anode for SIBs that delivered capacities of 210 and 87 mA h g–1 at 20 and 1600 mA g–1, respectively, retaining a capacity of 177 mA h g–1 when retained at 20 mA g–1. The as-synthesized CNFs demonstrate a long cycle life with a relatively high Columbic efficiency of 98.6% for the 900th cycle, with a stable and excellent rate capacity. The sodium storage mechanisms of the CNFs were examined with various nitrogen concentrations and carbonization temperatures. Furthermore, the diffusion coefficients of the sodium ions based on the electrochemical impedance spectra measurement have been calculated in the range of 10–15–10–12 cm2 s–1, revealing excellent diffusion mobility for Na atoms in the CNFs. This study demonstrates that optimum nitrogen doping and carbonization temperature demonstrated a lower Warburg coefficient and a higher Na-ion diffusion coefficient leads to enhanced stable electrochemical performance. Thus, our study shows that the nitrogen-doped CNFs will have potential for SIBs.

Trifunctional Electrocatalytic Activities of Nitrogen‐Doped Graphitic Carbon Nanofibers Synthesized by Chemical Vapor Deposition

AbstractHigh performance multifunctional electrocatalysts are attracting significant importance for application in energy storage, energy conversion and various other electrochemical reactions. In this prospect, we report on the effective trifunctional electrocatalytic properties of nitrogen (N) doped graphitic carbon nanofibers (CNFs). The CNFs were synthesized on a nichrome (NiCr) foil by chemical vapor deposition (CVD) process. Incorporation of Ni and Cr was observed in the N doped CNFs sample from microscopic and spectroscopic analysis. The metal nanoparticles can be significant in boosting the trifunctional electrocatalytic behavior. The effective oxygen reduction reaction (ORR), oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) activities were obtained for the CNFs sample with relatively good overpotential values. The electron transfer number per O2 molecule calculated from Koutecky‐Levich (K‐L) plot was found to be 2e− for the ORR reaction. The OER activity of the CNFs is comparable to commercially available iridium oxide (IrO2), signifying the effectiveness of the developed catalyst. Our study revealed that N doped CNFs with incorporation of metal particles synthesized on a binary metal substrate can be significant as ORR, OER, HER trifunctional electrocatalyst.

Integrating the Essence of a Metal–Organic Framework with Electrospinning: A New Approach for Making a Metal Nanoparticle Confined N-Doped Carbon Nanotubes/Porous Carbon Nanofibrous Membrane for Energy Storage and Conversion

The fabrication of an economic and efficient multifunctional advanced nanomaterial with a rational composition and configuration by a facile methodology is a crucial challenge. Herein, we are the first to report the growth of Co nanoparticle-integrated nitrogen-doped carbon nanotubes (N-CNTs) on porous carbon nanofibers by simply heating in the situ-developed metal-organic framework (MOF)-based electrospun nanofibrous membrane with no need for an external supply of any additional precursors and reducing gases. The long and entangled N-CNTs originating from highly porous and graphitic carbon nanofibers offer good flexibility, large surface area, high porosity, high conductivity, the homogeneous incorporation of heteroatoms and metallic constituents, and an abundant exposure of active nanocatalytic sites. The as-developed nanoassembly demonstrates attractive characteristics for electrocatalytic hydrogen and oxygen evolution reactions and electrochemical energy storage. This strategy of integrating the essence of an MOF with electrospinning offers a new, direct, and cost-effective approach for making N-doped CNT-based multifunctional membranes.

Advanced Nafion nanocomposite membrane embedded with unzipped and functionalized graphite nanofibers for high-temperature hydrogen-air fuel cell system: The impact of filler on power density, chemical durability and hydrogen permeability of membrane

Nafion, a perfluorosulfonic acid (PFSA) polymer, is a key electrolyte that has contributed to commercialization of hydrogen-air fuel cells (HAFCs). However, adoption of Nafion membranes in high-temperature (HT) HAFCs remains an unsolved challenge. In this work, sulfonic acid-functionalized, unzipped graphite nanofiber (SO3H-UGNF) is explored as a potential filler for Nafion to create a composite membrane for HT-HAFCs. The presence of –SO3H groups in SO3H-UGNF permits better dispersion of filler and boosts physiochemical, thermomechanical, and electrochemical properties of Nafion/SO3H-UGNF membrane compared to bare Nafion, Nafion/GNF, and Nafion/UGNF membranes. A range of concentrations of SO3H-UGNF (0.5, 1, or 1.5 wt%) are added to Nafion matrix to establish an optimal content for enhancing proton conductivity at 100, 50, and 18% relative humidity (RH). The optimized Nafion/SO3H-UGNF (1 wt%) membrane achieved a power output of 0.226 W cm˗2 and durability of over 129 h at 120 °C with 18% RH, which represents one of the best performances among reported Nafion-based membranes in HT-HAFCs. The hydrogen permeability, mechanical strength, and morphology of Nafion/SO3H-UGNF membrane were retained reasonably after durability test in HT-HAFC. This study provides valuable insights for design and optimization of potential Nafion composites for HT-HAFCs.

Cost-effective liquid-junction solar devices with plasma-implanted Ni/TiN/CNF hierarchically structured nanofibers

Carbon-based conductive materials have been recognized as promising alternatives to noble metals as the electrode in optoelectronic devices. Herein, by utilizing energetic plasma ion implantation, Ni-doped TiN nanowire (NWs) modified graphitic carbon nanofibers (CNF) are designed and prepared as the candidates of the platinum (Pt) counter electrode for low-cost hybrid perovskite-based liquid-junction photoelectrochemical solar cells (LPSCs). Notably, the photoelectrochemical (PEC) response of p-Rb0.05FA0.95PbI3 based-LPSCs equipped with the Ni/TiN/CNF counter electrode is almost identical to that with a typical Pt counter electrode. From electrochemical investigations, i.e., electrochemical impedance spectroscopy (EIS), we observe that the CNF-based materials show a similar redox activity compared with the Pt counter electrode, indicating low charge-transfer resistance (Rct) and large capacitance (C). The LPSCs, with a configuration of p-Rb0.05FA0.95PbI3/BQ (2 mM), BQ− (2 mM)/Ni/TiN/CNF-based counter electrode, exhibit an open-circuit photovoltage of 1.00 V and a short-circuit current density of 7.02 mA/cm2 under 100 mW/cm2 irradiation. The overall optical-to-electrical energy conversion efficiency is 5.06%. The PEC solar cell shows good stability for 5 h under irradiation. The CNF-based counter electrode enables potential applications, including but not limited to PEC solar devices, dye-sensitized solar cells (DSSCs), solar fuel devices and hydrogen evolution reaction.

Template-Based Synthesis of Hollow Nanotubular ZnO Structures and Nonlinear Electrical Properties under Field-Induced Trap-Assisted Tunneling

Hollow nanotubular ZnO structures were engineered using graphitic carbon nanofibers (GCNF) as removal templates by a modified coprecipitation method. Two dissimilar morphological ZnO-GCNF hybrids w...

Synthesis and Electocatalytic Activity of MnO2/RuO2/Carbon Nanocomposites to Enhance Lithium-Oxygen Battery Performance

Lithium-oxygen battery has received much attention as a potential energy storage system because of its ultra-high theoretical energy density (5,200 Wh kg−1), which remains to be the most promising future technology. However, there are several scientific/technical hurdles that must be overcome in order for a rechargeable Li–air battery to be commercialized in the market. In particular, the incomplete decomposition of solid discharge products such as Li2O2 etc. formed during discharge process passivates the cathode surface by clogging pores of the porous carbon cathode, resulting in diminishing the overall performance of battery. In order to solve these issues, great effort has been devoted to designing and developing novel electrocatalysts. It has been reported that electrocatalysts play an important role in ORR and OER, and hence improve the kinetics and efficiency of the Li–air battery.In this work, a suitable bifunctional catalyst was synthesized with MnO2 and RuO2, which are the well-known catalysts for oxygen reduction reaction(ORR) and oxygen evolution reaction(OER), respectively, by supporting on two different carbon supports such as graphite nanofiber(GNF) and graphene oxide(GO) for the application to oxygen cathode bifunctional catalysts of lithium-air batteries. MnO2/GNF was first prepared by a simple hydrothermal synthesis and was then decorated with various decorating ratios of RuO2 using a simple redox reaction technique. A good electrocatalytic performance was observed from a weight ratio of RuO2:MnO2/GNF=5:5. The Li-oxygen battery fabricated with the synthesized catalyst composition delivered a reduced overpotential with good cyclability and high specific capacity. In order to understand the effect of carbon, urchin-shaped α-MnO2/RuO2 nanostructures was first synthesized by a hydrothermal synthesis and was then loaded on GO with a weight ratio of 5:5 using a redox reaction technique. The synthesized α-MnO2/RuO2@GO (5:5) composite delivered high specific capacity with excellent electrocatalytic activity. Between the two different carbon supported composites, RuO2@MnO2/GNF showed excellent catalytic activity than α-MnO2/RuO2@GO. The increase in the surface area of carbon supports greatly influenced the performance of Li-air battery. Catalysts with carbon supports showed higher activity than without carbon. RuO2@MnO2/GNF was found to be the best catalyst which has two or tree times larger surface area than α-MnO2/RuO2@GO. Thus, RuO2@MnO2/GNF with 5:5 weight percentage was found to be the best electrocatalyst than all other synthesized catalysts.

Highly selective electrocatalytic Cl− oxidation reaction by oxygen-modified cobalt nanoparticles immobilized carbon nanofibers for coupling with brine water remediation and H2 production

Combining the H2 production with brine remediation is regarded as a sustainable approach to achieving clean H2 energy. However, designing stable Cl− oxidation reaction (COR) electrocatalyst is the key to realize this route. Herein, a type of oxygen-modified Co nanoparticles anchored graphitic carbon nanofibers catalyst (Co/GCFs) was synthesized through a two-step strategy of adsorption and pyrolysis. The Co/GCFs-2.4 exhibits high selectivity and stability for COR at neutral electrolyte. It is worth noting that unlike the water oxidation, the chemical valence of cobalt has not changed during the COR. Further results demonstrated that the oxygen-modified Co nanoparticles provide active sites for selective COR, meanwhile, the graphitic carbon gives rise to strong catalytic stability. Thanks to the superior COR and H2 production activity of Co/GCFs-2.4, a two-electrode brine electrocatalysis system employing Co/GCFs-2.4 as both cathode and anode for H2 production exhibited robust stability, efficient and high Faraday efficiency (98%-100%). We propose that this work provides a novel strategy for designing efficient and stable catalysts with electrocatalytic COR and HER activities at neutral brine water for practically coupling with H2 production by water electrolysis and brine water remediation.

Electrochemical hydrogen storage behavior of Ni-Ceria impregnated carbon micro-nanofibers

A hierarchical porous structured carbon micro-nanofiber containing the bimetallic configuration of the nickel (Ni) and ceria (CeO2) nanoparticles (NPs) was synthesized and tested for the electrochemical hydrogen (H2) storage capacity. The electrode exhibited a high H2 storage capacity of 498 mA h/g or 1.858% (w/w) at the charge-discharge current density of 500 mA/g. A mechanistic insight showcased the combined contributions of the high surface area containing activated carbon microfiber (ACF) substrate, the graphitic carbon nanofibers (CNFs), and the Ni and CeO2 NPs, towards the augmented electrochemical H2 storage capacity and cyclic stability of the fabricated Ni–CeO2–CNF/ACF electrode. Ni served as the catalyst for growing the CNFs via chemical vapor deposition as well as for storing H2 via spillover mechanism, while CeO2 created the charge carrier vacancies in the material. The measured cycle retention capacity of 99% and charge-discharge efficiency of 97.6% confirm the electrochemically stable characteristics of Ni–CeO2–CNF/ACF, and clearly indicate it to be an economically viable and efficient H2-storage material.