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Hierarchical self-assembly with long-range order above centimeters widely exists in nature. Mimicking similar structures to promote reaction kinetics of electrochemical energy devices is of immense interest, yet remains challenging. Here, we report a bottom-up self-assembly approach to constructing ordered mesoporous nanofibers with a structure resembling vascular bundles via electrospinning. The synthesis involves self-assembling polystyrene (PS) homopolymer, amphiphilic diblock copolymer, and precursors into supramolecular micelles. Elongational dynamics of viscoelastic micelle solution together with fast solvent evaporation during electrospinning cause simultaneous close packing and uniaxial stretching of micelles, consequently producing polymer nanofibers consisting of oriented micelles. The method is versatile for the fabrication of large-scale ordered mesoporous nanofibers with adjustable pore diameter and various compositions such as carbon, SiO2, TiO2 and WO3. The aligned longitudinal mesopores connected side-by-side by tiny pores offer highly exposed active sites and expedite electron/ion transport. The assembled electrodes deliver outstanding performance for lithium metal batteries. [ABSTRACT FROM AUTHOR]

Owing to the clean and environment friendly advantages, electrochemical water splitting stands out among various hydrogen production strategies. Electrocatalysts play an important role in the hydrogen evolution reaction (HER). Hence, Pt-(Ni0.5Co0.5)2P/S-carbon fibers as electrocatalysts for highly efficient HER were prepared through the structural designing of CNF and heteroatom doping (sulfur (S) or boron (B)). First, three composites of the (Ni0.5Co0.5)2P/carbon fiber ((Ni0.5Co0.5)2P/CNF), (Ni0.5Co0.5)2P/porous carbon fiber ((Ni0.5Co0.5)2P/PCNF), and (Ni0.5Co0.5)2P/hollow porous carbon fiber ((Ni0.5Co0.5)2P/HPCNF) were fabricated via a facile electrospinning with a solvothermal method. (Ni0.5Co0.5)2P/PCNFs showed the smallest overpotential at a current density of 10 mA cm−2 among the three structures. (Ni0.5Co0.5)2P nanosheets loaded on the porous CNF with a large active surface area may expose active sites and shorten the ion transport channel. To improve the catalytic performance of (Ni0.5Co0.5)2P/PCNF, Pt nanoparticles were anchored on (Ni0.5Co0.5)2P/heteroatom doped-PCNF by the chemical reduction method. Pt-(Ni0.5Co0.5)2P/S doped-PCNF exhibited a small overpotential of 64 mV for the HER with 74.9 mV dec−1 Tafel slope and a good stability, which was attributed to the conductive S-doped PCNF facilitating electron transport, accompanying the synergistic effect between the bimetallic phosphide and Pt nanoparticles, thus providing a facile method for an efficient HER electrocatalysis. [ABSTRACT FROM AUTHOR]

Cellulose has a wide range of applications in many fields due to their naturally degradable and low-cost characteristics, but few studies can achieve cellulose-nanofibers by conventional electrospinning. Herein, we demonstrate that the freestanding cellulose-based carbon nanofibers are successfully obtained by a special design of electrospinning firstly, pre-oxidation and high-temperature carbonization (1600 °C), which display a superior electrical conductivity of 31.2 S·cm−1 and larger specific surface area of 35.61 m2·g−1 than that of the polyacrylonitrile-based carbon nanofibers (electrical conductivity of 18.5 S·cm−1, specific surface area of 12 m2·g−1). The NiCo2O4 nanoflake arrays are grown uniformly on the cellulose-based carbon nanofibers successfully by a facile one-step solvothermal and calcination method. The asprepared cellulose-based carbon nanofibers/NiCo2O4 nanoflake arrays are directly used as electrodes to achieve a high specific capacitance of 1010 F·g−1 at 1 A·g−1 and a good cycling stability with 90.84% capacitance retention after 3000 times at 10 A·g−1. Furthermore, the all-solid-state symmetric supercapacitors assembled from the cellulose-based carbon nanofibers/NiCo2O4 deliver a high energy density of 62 W·h·kg−1 at a power density of 1200 W·kg−1. Six all-solid-state symmetric supercapacitors in series can also power a 'DHU' logo consisted of 36 light emitting diodes, confirming that the cellulose-based carbon nanofiber is a promising carbon matrix material for energy storage devices. [ABSTRACT FROM AUTHOR]

The carbon nanofiber-based all-solid-state supercapacitors hold great promise in powering portable electronics, while the low specific capacitance and intrinsic fragility have hindered their practical application. Here, flexible N-doped hollow carbon nanofibers (HCNFs) were prepared using poly-(acrylonitrile-co-acrylamide) as a precursor by the coaxial electrospinning method. The leaf-like NiCo2O4 nanosheets are located on the inner and outer walls of the carbon layer via a simple solvothermal method to construct 3D freestanding NiCo2O4/HCNFs electrodes for a flexible all-solid-state supercapacitor. The hollow structure of HCNFs provides both inner and outer surfaces for NiCo2O4 nanosheets and shortens the distance of ion transportation. NiCo2O4/HCNFs possesses an enhanced specific capacitance of 1864.0 F g–1 at 1 A g–1 and a good capacitance retention capability of 91.7% after 5000 times cycling, which is one of the best reported cycling stabilities to date. The symmetrical all-solid-state supercapacitors (ASSCs) were directly prepared with NiCo2O4/HCNFs as an electrode without adding any conductive agents and binders, which have good flexibility and a maximum energy density of 44.3 W h kg–1 at a specific power of 814.8 W kg–1. Five series-connected ASSCs assembled by NiCo2O4/HCNFs can lighten a "DHU" logo composed of 36 light-emitting diodes, indicating their potential application prospect in wearable and portable devices. [ABSTRACT FROM AUTHOR]