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[Display omitted] • CO 2 -derived CNT/PCF free-standing electrode is synthesized for Li-S batteries. • Entangled CNTs on porous nanofibers maximize the utilization of active materials. • CCNT/PCF electrode with superior pore properties enhance the Li-ion movement. • Edge-site nitrogen has favorable thermodynamic roles to minimize the shuttle effect. • CCNT/PCF offers capacity of 3.34 mAh cm−2 and 412 mAh g cathode −1 at the 200th cycle. The implementation of a free-standing carbon electrode provides an excellent strategy for the development of lithium-sulfur (Li-S) batteries with a maximized sulfur portion as the electrode does not require auxiliary components including a conducting agent, binder, and current collector. Electrospinning using a polymer is an attractive approach to prepare a free-standing electrode based on high carbon yield, but effective distribution and utilization of sulfur are hindered by the low porosity of the synthesized carbon nanofiber. The present work tackles this problem of electrospinning-based free-standing electrodes by utilizing Ni precursors and CO 2 conversion to make porous materials by the resulting entangled CNTs as well as pores in the carbon nanofiber. The newly formed pores greatly improved the utilization of active sulfur materials and the movement of Li ions. While leading to CNT growth and pore formation, the Ni precursor also played a role in shifting nitrogen atoms from the graphene center to the edge-site, which could greatly improve the chemical interaction between lithium polysulfides and Li-ion as also confirmed by DFT calculations. The CNTs in porous carbon fibers, which are synthesized from CO 2 and have both morphological and chemical advantages, delivered an areal capacity of 3.34 mAh cm−2 up to the 200th cycle when driven at 0.2C with high content sulfur-based active materials of 6.52 mg cm−2. The CNT free-standing electrode can effectively provide a high capacity of 412 mAh g cathode −1 based on the total cathode weight. [ABSTRACT FROM AUTHOR]

• A unique free-standing electrode based on CoSe 2 nanoparticles-decorated CNFs is developed as a catalytic selenium host. • In Se/CoSe 2 @CNF, CoSe 2 provides catalytic sites to boost polyselenide conversion and guides uniform deposition of Li 2 Se. • DFT calculations show that the introduction of CoSe 2 nanoparticles lowers the redox barrier for Li 2 Se growth. Selenium cathodes have attracted widespread attention due to their high electronic conductivity and considerable volume capacity. However, the harmful shuttle of lithium polyselenides and irregular deposition of lithium selenide (Li 2 Se) severely degrade the redox rate of active selenium, causing poor cycling stability. Toward overcoming these limitations, herein, a catalytic electrode based on carbon nanofibers loaded with CoSe 2 nanoparticles (CoSe 2 @CNF) is designed and engineered to trap polyselenides and activate their conversion. Density functional theory (DFT) calculations show that the introduction of CoSe 2 nanoparticles lowers the redox barrier for Li 2 Se growth. Even more important, the presence of a homogeneous distribution of CoSe 2 provides abundant nucleation sites for uniform Li 2 Se deposition. As a result, Li-Se batteries based on Se/CoSe 2 @CNF free-standing electrodes exhibit outstanding cycle stability. After 800 cycles, Se/CoSe 2 @CNF electrodes display a high capacity of 435.1 mAh g−1 with a 0.032% capacity decay per cycle at 0.5C. Even at a selenium loading of 4.1 mg cm−2, a high capacity retention rate of 72.8% is measured. Overall, this work provides a new strategy for achieving high-performance Li-Se batteries by introducing efficient polyselenide electrocatalysts as selenium hosts to facilitate the conversion of polyselenides and regulate the homogenous growth of Li 2 Se. [ABSTRACT FROM AUTHOR]

The detection of the neurotransmitter dopamine in medicinal and human biological samples has attracted the huge interest of researchers in recent years. Carbon nanofiber is a potential nanocarbon material for the detection of dopamine (DA) due to its good electrochemical properties. In this work, carbon nanofiber (CNF) supported nickel nanoparticles (Ni@CNF) were prepared by wet impregnation method and characterized by TEM, EDS, XRD and FTIR analysis. The Ni@CNF modified screen printed electrode gave superior electrochemical response. Moreover, the Ni@/CNF shows a broad linear detection range (0.1-10 μM), a low detection limit (0.03 μM) by using DPV analysis and excellent selectivity. The developed electrode shows good reproducibility, stability, and repeatability. The Ni@CNF/SPCE has been also utilized for the detection of DA in pharmaceutical, human blood serum and urine samples with substantial recovery outcomes. Therefore, the prepared CNF@Ni/SPCE will be a capable platform for the electrochemical detection of DA in biological or medicinal samples. [Display omitted] • Preparation of Ni metal supported carbon nanofibers catalyst by wet impregnation method • Cyclic volammetric detection of dopamine by using Ni@CNF coated screen printed carbon paste electrode • Detection of DA in injectable medicine, blood serum and urine sample were used as real sample applications [ABSTRACT FROM AUTHOR]

Free-standing carbon nanofibrous membranes are prepared by carbonization and H 2 O 2 activation of electrospun polyimide nanofibrous membranes. The green and facile H 2 O 2 activation method not only regulates the pore structure of carbon nanofibers but also introduces rich oxygen species, rendering a hierarchically porous and heteroatom-doped carbon electrode for supercapacitors. The optimal electrode (PI800-8) shows a high specific capacitance of 339.9 F g−1 (0.5 A g−1, 6 M KOH electrolyte) and excellent cycle durability with a capacitance retention of 98.4 % after 50,000 cycles (5 A g−1). Particularly, a non-aqueous symmetric supercapacitor assembled with 1 M Et 4 NBF 4 electrolyte shows a high operating voltage of 2.8 V, and delivers the maximum energy/power density of 37.3 Wh kg−1 and 28.0 kW kg−1, respectively. The H 2 O 2 activation method provides a green, efficient, and versatile strategy to improve the pore properties and chemical compositions of porous carbon materials towards energy applications. [Display omitted] • The N/O-codoped carbon nanofibrous membranes were prepared by commercial electrospun polyimide nanofibrous membranes. • The green H 2 O 2 activation was proposed to ameliorate the pore and chemical properties of carbon nanofibrous membranes. • Excellent comprehensive performance was presented for both aqueous/non-aqueous symmetric supercapacitor. [ABSTRACT FROM AUTHOR]

Carbon materials are potential counter electrodes for all−inorganic hole transport layer (HTL)−free perovskite solar cells (PSCs), whereas the defects of the perovskite/carbon back interface are the dominant reason for the low power conversion efficiency (PCE) of this kind of device. To resolve this problem, carbon nanofiber (CNF) was first synthesized using electrospinning technique to construct a carbon counter electrode with porous network architecture by self−supporting nature of CNF. The CsPbBr 3 based all−inorganic HTL−free PSCs using the porous CNF counter electrode shows a PCE of 5.01%. To further modify the CsPbBr 3 /carbon back interface and energy level alignment, mesoporous CNF (m−CNF) and B doped m−CNF (m−BCNF) are synthesized, which can improve the conductivity of the carbon counter electrodes as well as decline the trap state densities and accelerate the carrier extraction and transport properties of the back interface. Accordingly, the all inorganic HTL−free PSCs using m−CNF and m−BCNF counter electrodes generate high PCE of 7.48% and 8.38%, with outstanding long−tern stability. The enhanced PCE improvements can be ascribe to strategies of construction of multilevel network and B doping which can modify the CsPbBr 3 /carbon back interface, optimize the energy level alignment of the device, and enhance the conductivity of the carbon counter electrode. This research is expected to provide meaningful support for development of new counter electrode materials and back interface engineering for high-performance all inorganic HTL−free PSCs. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • We provide a well-controlled carbon system to study thin-liquid-layer effects. • Our model system probes only geometrical factors – no chemical effects are present. • We show that we can still induce apparent electrocatalysis. • We can validate that these are thin-liquid-layer effects and not electrocatalysis. • If proper diagnostics are not used, thin-liquid-layer effects can remain unnoticed. Here we use an electrode consisting of carbon nanofibers (CNFs), the lengths and surface population density of which can be effectively controlled. It is shown that (i) a thin liquid layer forms when the thickness of the diffusion layer has a specific ratio to the dimensions of the nanostructured carbon surface. (ii) This leads to a decrease in the peak potential difference and a subsequent increase in the apparent heterogeneous electron transfer (HET) constant, both of which could be interpreted as a result of increased catalytic activity. (iii) However, we show that this explanation is not likely, as our materials are chemically identical, and we use an outer sphere redox (OSR) probe to minimize any specific chemical interactions. On the contrary, (iv) the results clearly show that the observed behavior is caused by a combination of the formation of a thin liquid layer and the increased apparent surface area of the electrodes. [ABSTRACT FROM AUTHOR]

• Flexible, freestanding, binder-free nanofiber electrodes for lithium-ion batteries are introduced. • Significance and limitations of electrospinning for fabrication of freestanding electrodes are discussed. • Parameters and polymers for the design of porous and core–shell nanofibers are analyzed. • Feasibility of decorating fibers with nanosheets, nanocones, and polyhedra of active materials is discussed. Carbon nanofibers derived from electrospun precursors show great promise for electronic applications owing to their flexibility, conductivity, high surface area, and open structure. The integration of metal oxides and sulfides in carbon nanofibers, rather than using them with other binders, eliminates many problems caused by poor adhesion, nanomaterial agglomeration, excess mass contributed by inactive binders, and low conductivity of embedded active materials. The engineering of electrospun fibers with novel morphologies, such as core–shell, hollow, or porous structures, and the use of decorated carbon nanofibers (e.g. , by electrodeposition or co-precipitation) are discussed in this review. Representative schematic illustrations of the lithium-storage mechanism for these binder-free electrodes are presented. We describe how the electrospinning technique can offer a cost-effective strategy for fabrication of lightweight lithium-ion batteries with high capacity and excellent bendability. This review presents the fascinating morphologies of these specially designed carbon nanofiber electrodes, which enhance the electrochemical performance of metal oxides and sulfides, illustrating their enormous potential for use in wearable electronic devices and hybrid electric vehicles. [ABSTRACT FROM AUTHOR]

• A hierarchical aligned carbon electrode was fabricated for aqueous flow batteries. • The specific surface area and the transport properties are simultaneously enhanced. • The as-prepared electrode enables 80.1% energy efficiency at 300 mA cm−2. • The battery with the prepared electrode exhibits favorable cycling stability. Enhancing the transport properties and enlarging the surface area of electrodes are critical for achieving a high-power-density aqueous redox flow battery. In this work, we design and fabricate a hierarchical and ordered carbon fibrous (CNF-AECF) electrode by in-situ growing a layer of carbon nanofibers on the surface of aligned electrospun carbon fibers. The aligned macroscopic structure provides electrolytes transport pathways, while the highly porous carbon nanofiber layer offers a large specific surface area of up to 108 m2 g−1, enabling abundant active sites for redox reactions. Cyclic voltammetry tests show that the positive side peak potential separation is reduced from 92.77 mV to as low as 55.01 mV, while the negative side peak potential separation is reduced from 92.77 mV to 88.65 mV at the scan rate of 10 mV s−1. The application of the as-prepared material to a vanadium redox flow battery as the positive electrode demonstrates an energy efficiency of 80.1% at the current density of 300 mA cm−2, and 75.0% at the current density of 400 mA cm−2, which is 5.0% and 6.6% higher than that with the pristine electrospun carbon fiber electrodes. All these results show that the custom-made carbon electrode with rationally designed geometric structures and surface properties offer the promise to achieve high power density for aqueous redox flow batteries. [ABSTRACT FROM AUTHOR]

• Advanced electrodes derived from carbon fiber-reinforced CF-CNF/MWCNT-HAs. • The HAs possess 3-D porous structure and strengthened mechanical property. • Used as a powerful platform for constructing high-performance flexible electrodes. • The flexible ASC device with significant energy density of 8.93 mWh/cm3. Developing electrodes with excellent electrochemical and mechanical properties is the key to achieve state-of-the-art flexible asymmetric supercapacitors (ASCs). This work proposes a facile and scalable strategy to prepare high-performance flexible electrodes based on carbon fiber-reinforced cellulose nanofiber/multiwalled carbon nanotube-hybrid aerogels (CF-CNF/MWCNT-HAs). The three-dimensional (3-D) porous structure, excellent conductivity, binder-free nature, and high strength of the CF-CNF/MWCNT-HAs enable it to serve as a powerful platform for constructing flexible electrodes with outstanding capacitive performance. The as-prepared CF-CNF/MWCNT/MnO 2 positive electrode and CF-CNF/MWCNT/active carbon (AC) negative electrode display remarkably high areal-specific capacitances (1745 and 1273 mF/cm2 at a current density of 1 mA/cm2, respectively). In addition, the carbon fiber-reinforced electrode also presented an excellent mechanical property with a maximum stress up to 27.9 MPa. The as-fabricated CF-CNF/MWCNT/MnO 2 //CF-CNF/MWCNT/AC flexible ASC device exhibits significant capacitance and energy density of 19.4 F/cm3 and 8.93 mWh/cm3, respectively. Additionally, this flexible ASC device can retain more than 96.7% of its capacitance after 3000 charge-discharge cycles. These results will enable us to fabricate flexible solid-state ASC devices from CF-CNF/MWCNT-HAs, and to expand its applications in the fields of portable and wearable electronics. [ABSTRACT FROM AUTHOR]