Reduced Graphene Oxide Nanofiber Research Articles

High-performance cathode promoted by reduced graphene oxide nanofibers with well-defined interconnected meso-/micro pores for rechargeable Li-Se batteries

Highly conductive nanostructures comprising one-dimensional (1D) reduced graphene oxide (rGO) nanofibers (NFs) and bimodal pores i.e., meso-/micropores, as efficient cathode hosts (Bi-P-rGO) for Li–Se batteries were prepared. The highly conductive rGO matrix acts as a self-supporting skeleton to enhance the structural integrity of the nanostructure besides providing numerous conducting pathways for rapid charge transfer. Moreover, highly interconnected chain-like mesopores guarantee efficient electrolyte percolation, whereas the micropores offer highly active material impregnation. Correspondingly, Bi-P-rGO@Se as a high-performance cathode was visualized, which demonstrated an overall enhanced electrochemical performance such as excellent rate capability (up to 20.0C) and overwhelming long-term cycling stability (73% capacity retention at the end of 800cycles with an average capacity decay rate of just 0.03% per cycle at 0.5C rate). The exceptional electrochemical performance of the Bi-P-rGO@Se cathode can be attributed to its highly porous structure, which promises efficient electrolyte infiltration and diffusion of charged species, high active material utilization within micropores, availability of conductive pathways for fast charge transfer, and high structural integrity. Therefore, we anticipate that the structural and electrochemical results presented in this work will provide significant insights into the synthesis of high-performance porous and conductive nanostructures for a wide range of applications.

AQDS-guided growth of nanocilia-like polyaniline on graphene nanofiber as cathode material for high-performance asymmetric supercapacitors

Reduced graphene oxide nanofiber (rGONF) modified by anthraquinone-1,5-disulfonate (AQDS) (AQDS-rGONF) was prepared by one-step hydrothermal reaction, and nanocilia-like polyaniline (PANI) grew uniformly on the surface of rGONF under the guidance of AQDS as a starting point of polymerization to fabricate successfully PANI/AQDS-rGONF composite. The results showed that PANI/AQDS-rGONF composite had a larger specific capacitance of 511 F/g than PANI/rGONF composite of 360 F/g or PANI of 312 F/g at a current density of 8 mA/cm2, and a greater electrochemical stability with the specific capacitance retention of 82.4% than PANI/rGONF of 63.2% or PANI of 52.2% after 2000 cycles, which were closely related to the synergistic effects of special nanocilia-like structure, large specific surface area, rGONF as a supporting skeleton and AQDS as a “bridge”. In addition, an asymmetric supercapacitor based on PANI/AQDS-rGONF composite as cathode was assembled, which exhibited a high energy density of 17.9 Wh/kg at a power density of 907 W/kg.

Capacitance Enhancement of Hydrothermally Reduced Graphene Oxide Nanofibers.

Nanocarbon materials present sp2-carbon domains skilled for electrochemical energy conversion or storage applications. In this work, we investigate graphene oxide nanofibers (GONFs) as a recent interesting carbon material class. This material combines the filamentous morphology of the starting carbon nanofibers (CNFs) and the interlayer spacing of graphene oxide, and exhibits a domain arrangement accessible for fast transport of electrons and ions. Reduced GONFs (RGONFs) present the partial removal of basal functional groups, resulting in higher mesoporosity, turbostratic stacking, and surface chemistry less restrictive for transport phenomena. Besides, the filament morphology minimizes the severe layer restacking shown in the reduction of conventional graphene oxide sheets. The influence of the reduction temperature (140–220 °C) on the electrochemical behaviour in aqueous 0.5 M H2SO4 of RGONFs is reported. RGONFs present an improved capacitance up to 16 times higher than GONFs, ascribed to the unique structure of RGONFs containing accessible turbostratic domains and restored electronic conductivity. Hydrothermal reduction at 140 °C results in the highest capacitance as evidenced by cyclic voltammetry and electrochemical impedance spectroscopy measurements (up to 137 F·g−1). Higher temperatures lead to the removal of sulphur groups and slightly thicker graphite domains, and consequently a decrease of the capacitance.

A method for producing conductive graphene biopolymer nanofibrous fabrics by exploitation of an ionic liquid dispersant in electrospinning

Owing to its high conductivity, graphene has been incorporated into polymeric nanofibers to create advanced materials for flexible electronics, sensors and tissue engineering. Typically, these graphene-based nanofibers are prepared by electrospinning synthetic polymers, whereas electrospun graphene-biopolymer nanofibers have been rarely reported due to poor compatibility of graphene with biopolymers. Herein, we report a new method for the preparation of graphene-biopolymer nanofibers using the judicious combination of an ionic liquid and electrospinning. Cellulose acetate (CA) has been used as the biopolymer, graphene oxide (GO) nanoparticles as the source of graphene and 1-butyl-3-methylimidazolium chloride ([BMIM]Cl) as the ionic liquid (IL) to create CA-[BMIM]Cl-GO nanofibers by electrospinning for the first time. Moreover, we developed a new route to convert CA-[BMIM]Cl-GO nanofibers to reduced GO nanofibers using hydrazine vapor under ambient conditions to enhance the conductivity of the hybrid nanofibers. The graphene sheets were shown to be uniformly incorporated in the hybrid nanofibers and only 0.43 wt% of GO increase the conductivity of CA-[BMIM]Cl nanofibers by more than four orders of magnitude (from 2.71× 10−7 S/cm to 5.30 × 10−3 S/cm). This ultra-high enhancement opens up a new route for conductive enhancement of biopolymer nanofibers to be used in smart (bio) electronic devices.

Construction of reduced graphene oxide nanofibers and cobalt sulfide nanocomposite for pseudocapacitors with enhanced performance

Abstract Construction of metal oxide/sulfide and carbon-based material nanocomposites is an effective strategy to obtain high-performance electrode materials for supercapacitors. In the present work, graphene oxide nanofibers (GONFs) are selected as the support materials, and the nanocomposite of reduced graphene oxide nanofiber and cobalt sulfide (rGONF/CoS2) is synthesized via a simple and facile method. As an electrode material for pseudocapacitors, the rGONF/CoS2 nanocomposite exhibits a high specific capacitance of 635.8 F g-1 at a current density of 1 A g-1 measured in 6 M KOH electrolyte, which is much higher than that of bare cobalt sulfide. Furthermore, the rGONF/CoS2 nanocomposite has also shown excellent cycling performance with 95.4% capacitance retention over 2000 cycles. In addition, the assembled asymmetric supercapacitor (ASC) device using rGONF/CoS2 nanocomposite as cathode material and activated carbon (AC) as anode material can work at a high operating voltage of 1.65 V and show a maximum energy density of 13.8 W h kg−1 at a power density of 824.6 W kg−1.

Supercapacitors Based on Reduced Graphene Oxide Nanofibers Supported Ni(OH)2 Nanoplates with Enhanced Electrochemical Performance

Pseudocapacitive materials are critical to the development of supercapacitors but usually suffer from poor conductivity and bad cycling property. Here, we describe the production of novel graphene oxide nanofibers (GONFs) via a partial oxidization and exfoliation method and concurrently report that highly crystallized Ni(OH)2 nanoplates uniformly grow on reduced GONFs' outer graphene nanosheets through the hydrothermal method. Because of their unique structure with high electric conductivity, the rGONF/Ni(OH)2 composite exhibits superior specific capacitance (SC), favorable rate capability and enhanced cycling stability relative to other composites or hybrids, e.g., 1433 F g(-1) at 5 mV s(-1) scan rate, 986 F g(-1) at 40 mV s(-1), and 90.5% capacitance retention after 2000 cycles, and as-fabricated rGONF/Ni(OH)2//active carbon asymmetric supercapacitor (ASC) exhibits a remarkable energy density and a 85.3% high retention (44.1 Wh kg(-1) at 467 W kg(-1) and 37.6 Wh kg(-1) at 3185 W kg(-1)) with a wide potential window of 0-1.7 V. Therefore, this study shows that rGONFs offers an exciting opportunity as substrate materials for supercapacior applications and opens up a new pathway for design and manufacture of novel supercapacitor electrode materials.

Fabrication, Characterization, and Biocompatibility of Polymer Cored Reduced Graphene Oxide Nanofibers.

Graphene nanofibers have shown a promising potential across a wide spectrum of areas, including biology, energy, and the environment. However, fabrication of graphene nanofibers remains a challenging issue due to the broad size distribution and extremely poor solubility of graphene. Herein, we report a facile yet efficient approach for fabricating a novel class of polymer core-reduced graphene oxide shell nanofiber mat (RGO-CSNFM) by direct heat-driven self-assembly of graphene oxide sheets onto the surface of electrospun polymeric nanofibers without any requirement of surface treatment. Thus-prepared RGO-CSNFM demonstrated excellent mechanical, electrical, and biocompatible properties. RGO-CSNFM also promoted a higher cell anchorage and proliferation of human bone marrow mesenchymal stem cells (hMSCs) compared to the free-standing RGO film without the nanoscale fibrous structure. Further, cell viability of hMSCs was comparable to that on the tissue culture plates (TCPs) with a distinctive healthy morphology, indicating that the nanoscale fibrous architecture plays a critically constructive role in supporting cellular activities. In addition, the RGO-CSNFM exhibited excellent electrical conductivity, making them an ideal candidate for conductive cell culture, biosensing, and tissue engineering applications. These findings could provide a new benchmark for preparing well-defined graphene-based nanomaterial configurations and interfaces for biomedical applications.

Elastic Reduced Graphene Oxide Nanosheets Embedded in Germanium Nanofiber Matrix as Anode Material for High-Performance Li-Ion Battery

Germanium, as a semiconductor material, has a poor electrical conductivity, but the high theoretical capacity of 1600mAhg−1 makes it as a promising high-capacity anode material for lithium-ion batteries (LIBs). The huge volume variation during charge and discharge leads to a poor cycling stability. In this paper, Ge with reduced graphene oxide nanofibers (Ge@RGO NFs) are firstly prepared by electrospinning. The nanofibers with a uniform diameter of 50nm combined RGO delivered a high specific capacity of 1727.0mAhg−1 in the fist discharging and 1205.1mAhg−1 after 100 cycles at the constant current density of 200mAg−1. RGO in the composites has two important roles: (i) as a conductive agent to improve electrical conductivity; (ii) as a buffer to protect Ge nanostructure from pulverization during charge and discharge processes. Electrochemical testing results show that the Ge@RGO nanofibers anode has a high specific capacity of 661.6mAhg−1 at the current density of 5000mAg−1, suggesting the Ge@RGO electrodes can be used to high current and high-power electronic equipments.

Electrospun hollow glassy carbon–reduced graphene oxide nanofibers with encapsulated ZnO nanoparticles: a free standing anode for Li-ion batteries

In this paper, a novel anode architecture for Li-ion batteries fabricated by encapsulation of ZnO nanoparticles in the hollow core of glassy carbon–reduced graphene oxide electrospun composite nanofibers, is described.