Electrospinning is a versatile and viable technique for generating ultrathin fibers. Remarkable progress has been made with regard to the development of electrospinning methods and engineering of electrospun nanofibers to suit or enable various applications. We aim to provide a comprehensive overview of electrospinning, including the principle, methods, materials, and applications. We begin with a brief introduction to the early history of electrospinning, followed by discussion of its principle and typical apparatus. We then discuss its renaissance over the past two decades as a powerful technology for the production of nanofibers with diversified compositions, structures, and properties. Afterward, we discuss the applications of electrospun nanofibers, including their use as "smart" mats, filtration membranes, catalytic supports, energy harvesting/conversion/storage components, and photonic and electronic devices, as well as biomedical scaffolds. We highlight the most relevant and recent advances related to the applications of electrospun nanofibers by focusing on the most representative examples. We also offer perspectives on the challenges, opportunities, and new directions for future development. At the end, we discuss approaches to the scale-up production of electrospun nanofibers and briefly discuss various types of commercial products based on electrospun nanofibers that have found widespread use in our everyday life.

Electrospinning and Electrospun Nanofibers: Methods, Materials, and Applications

A review on g-C3N4-based photocatalysts

Mesoporous photocatalytic materials with macroporous structures have attracted more and more attention because of their textural mesopores and intrinsic interconnected pore networks, which are able to efficiently transport guest species to framework binding sites. In this work, macro/mesoporous g-C 3 N 4 /TiO 2 heterojunction photocatalysts were fabricated without templates or additives by a facile calcination method using tetrabutyl titanate and melamine as the feedstocks. Photocatalytic experiments of the as-prepared samples were measured by the photocatalytic oxidation degradation of RhB solution at room temperature under visible light irradiation. The results indicated that the melamine content in the precursors had an important influence on photocatalytic activity of the as-prepared samples. At the optimal loading content, the apparent reaction rate constant ( k ) was 47.8 × 10 −3  min −1 for RhB degradation, exceeding that of pure TiO 2 (6.6 × 10 −3  min −1 ) and g-C 3 N 4 (15.2 × 10 −3  min −1 ) by factor of 7.2 and 3.1 respectively. The improved photocatalytic activity was attributed to high surface area and heterostructure formation of g-C 3 N 4 /TiO 2 composites. The trapping experiment results showed that O 2 − and h + were main active species in the decomposition of RhB. A possible enhanced photocatalytic mechanism of g-C 3 N 4 /TiO 2 heterojunction photocatalysts was proposed.

Template-free preparation of macro/mesoporous g-C3N4/TiO2 heterojunction photocatalysts with enhanced visible light photocatalytic activity

Photocatalysis fundamentals and surface modification of TiO2 nanomaterials

Constructing a TiO2 based heterostructure is a very effective strategy for enhancing photocatalytic performance. The details of the electronic structure, interfacial interaction, and photogenerated carrier separation are important for explaining the photocatalytic properties of a heterostructure. Herein, the density of states, charge distribution, and the band offset of the monolayer g-C3N4/TiO2 heterojunction are systematically investigated through the hybrid DFT method. Results indicated that the valence band offset and the conduction band offset of the g-C3N4/TiO2 heterostructure were 0.40 and 0.18 eV, respectively. Interfacial interaction made the TiO2 surface with negative charge, whereas the g-C3N4 surface with positive charge, which led to the formation of a built-in electric field at the interface. Under illumination, the built-in electric field accelerates the transfer of photoexcited electrons in the CB of TiO2 into the VB of g-C3N4, thus resulting in the photoexcited electrons and holes naturally accumulating in the CB of g-C3N4 and the VB of TiO2, respectively. The photoexcited electrons and holes gathering in different surface regions efficiently prolonged the lifetime of photogenerated carriers. Meanwhile, electrons in the CB of g-C3N4 and holes in the VB of TiO2 had a stronger redox ability. Therefore, g-C3N4/TiO2 is a direct Z-scheme photocatalyst, and the Z-scheme heterostructure mechanism can well explain the improved photocatalytic activity of the g-C3N4/TiO2 heterostructure.

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A new understanding of the photocatalytic mechanism of the direct Z-scheme g-C3N4/TiO2 heterostructure

g-C3N4 modified TiO2 nanosheets with enhanced photoelectric conversion efficiency in dye-sensitized solar cells

Bilayer hollow/spindle-like anatase TiO2 photoanode for high efficiency dye-sensitized solar cells

High-efficiency dye-sensitized solar cells based on electrospun TiO2 multi-layered composite film photoanodes

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Maximum thickness of non-buffer limited electro-active biofilms decreases at higher anode potentials

Nowadays biomass has become important sources for the synthesis of different carbon nanomaterials due to their low cost, easy accessibility, large quantity, and rapid regeneration properties. Although researchers have made great effort to convert different biomass into carbons for oxygen reduction reaction (ORR), few of these materials demonstrated good electrocatalytical performance in acidic medium. In this work, fresh daikon was selected as the precursor to synthesize three dimensional (3D) nitrogen doped carbons with hierarchical porous architecture by simple annealing treatment and NH3 activation. The daikon-derived material Daikon-NH3-900 exhibits excellent electrocatalytical performance towards oxygen reduction reaction in both alkaline and acidic medium. Besides, it also shows good durability, CO and methanol tolerance in different electrolytes. Daikon-NH3-900 was further applied as the cathode catalyst for proton exchange membrane (PEM) fuel cell and shows promising performance with a peak power density up to 245 W/g.

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Guanxi Wang

Papers

g-C3N4 modified TiO2 nanosheets with enhanced photoelectric conversion efficiency in dye-sensitized solar cells

Bilayer hollow/spindle-like anatase TiO2 photoanode for high efficiency dye-sensitized solar cells

High-efficiency dye-sensitized solar cells based on electrospun TiO2 multi-layered composite film photoanodes

Maximum thickness of non-buffer limited electro-active biofilms decreases at higher anode potentials

Nitrogen-doped hierarchical porous carbons derived from biomass for oxygen reduction reaction