Heping Li

Novel heterostructured InN/TiO2 submicron fibers designed for high performance visible-light-driven photocatalysis

As a typical photocatalyst, TiO2 can only absorb UV light limited by its wide band gap, which severely limits its industrial application. Seeking effective strategies to enable its visible light absorption is in the spotlight. In this paper, InN with a band gap of 0.7 eV was incorporated into TiO2 nanofibers to obtain high-performance visible-light photocatalysts for the first time. Heterostructured InN/TiO2 submicron fibers were facilely fabricated via an electrospinning technique followed by a nitridation procedure. InN was homogeneously distributed in the TiO2 matrix, as characterized by transmission electron microscopy. Owing to the ultra-narrow band gap of InN, the light absorption of the InN/TiO2 hybrid submicron fibers was broadened to visible wavelengths. The photocatalytic performance of the heterostructure was assessed through the decomposition of rhodamine B under visible light irradiation. Approximately 80% rhodamine B was decomposed in just 15 min. The rate constant reached up to 0.089 min−1, which was enhanced 45 times compared with the electrospun TiO2 fibers. This great improvement in the photocatalytic properties was attributed to both the intense visible-light absorption and the efficient charge separation enabled by the homogeneous distribution of the InN phase in the TiO2 fibers. The photocatalytic efficiency achieved here was among the highest values of the currently reported photocatalysts. The results obtained in this work may pave a new way for the fabrication of high-performance visible-light photocatalysts.

Facile synthesis of highly conductive Ag/TiN nanofibers for cost-saving transparent electrodes

By homogeneously incorporating Ag into a conductive TiN matrix, ultra high electrical conductivity of 1181 S cm−1 was achieved in hybrid Ag/TiN nanofibers. In comparison to the state-of-the-art pure Ag nanowire transparent electrodes, the cost-saving Ag/TiN nanofiber network exhibited comparable optoelectronical performance. This newly developed material may serve as an alternative for cost-efficient transparent electrodes.

Copper-coated TiN nanofibers with high electrical conductivity: a new advance in conductive one-dimensional nanostructures

High electrical conductivity has been achieved in ceramics with a heterostructure design. We managed to incorporate an inexpensive metal into conductive nitride nanofibers. Low sheet resistance and high optical transparency were obtained on the nanofiber patterns, which indicate that it may serve as a new material for transparent electrodes.

Flexible 3D Fe@VO 2 core-shell mesh: A highly efficient and easy-recycling catalyst for the removal of organic dyes

Nowadays, it is extremely urgent to search for efficient and effective catalysts for water purification due to the severe worldwide water-contamination crises. Here, 3D Fe@VO2 core-shell mesh, a highly efficient catalyst toward removal of organic dyes with excellent recycling ability in the dark is designed and developed for the first time. This novel core-shell structure is actually 304 stainless steel mesh coated by VO2, fabricated by an electrophoretic deposition method. In such a core-shell structure, Fe as the core allows much easier separation from the water, endowing the catalyst with a flexible property for easy recycling, while VO2 as the shell is highly efficient in degradation of organic dyes with the addition of H2O2. More intriguingly, the 3D Fe@VO2 core-shell mesh exhibits favorable performance across a wide pH range. The 3D Fe@VO2 core-shell mesh can decompose organic dyes both in a light-free condition and under visible irradiation. The possible catalytic oxidation mechanism of Fe@VO2/H2O2 system is also proposed in this work. Considering its facile fabrication, remarkable catalytic efficiency across a wide pH range, and easy recycling characteristic, the 3D Fe@VO2 core-shell mesh is a newly developed high-performance catalyst for addressing the universal water crises.

Parallel patterning of SiO2 wafer via near-field electrospinning of metallic salts and polymeric solution mixtures

This paper describes a near-field electrospinning technique combined with heat treatment process used to directly align parallel metal oxide and metal nitride fibers on silicon dioxide substrate. The effects of near-field electrospinning parameters (including collector-to-needle distance, applied voltage and the moving speed of the collector) on the morphology of the resulted fibers have been studied. Metallic salt-contained precursor fibers are individually aligned via near-field electrospinning of metallic salts and polymeric solution mixtures. After applying calcination process to these well aligned precursor fibers, patterning by metal oxide and metal nitride fibers such as ZnO, Ga2O3, TiO2, GaN and TiN is successfully obtained. The optical microscope images and the scanning electron microscopy show the presence of fiber patterns, whose crystalline structure is characterized by x-ray diffraction and Raman spectroscopy measurement. The results demonstrate the potential of this approach for assembling ceramic fibers into parallel arrays with controllable orientation and position.

Novel flexible Fenton-like catalyst: Unique CuO nanowires arrays on copper mesh with high efficiency across a wide pH range

Free-standing and flexible Cu@CuO nanowires (NWs) mesh as an easily recycled Fenton-like catalyst is developed for the first time. Dense CuO nanowire arrays were uniformly grown on a copper mesh surface simply by wet etching accompanied with thermal dehydration. These dense CuO NWs provide a large specific area and therefore guarantee excellent catalytic performance toward the degradation of rhodamine B (RhB). With a k-value of 0.23 min-1, such a Cu@CuO NWs mesh is able to degrade 100% RhB in only 16 min. This Fenton-like catalyst is also appropriate for degrading other organic dyes, including crystal violet, methylene blue, and rhodamine 6G. Unlike the conventional Fenton catalyst implemented at a pH value around 3, the Cu@CuO NWs mesh could adapt to a wide pH range from 2.1 to 12.0. More intriguingly, the Cu@CuO NWs mesh with excellent flexibility could be easily recycled after catalysis, which is a significant advance compared to the previously reported Fenton catalysts in the form of powders or nanoparticles. In addition, the recycling performance of this Cu@CuO NWs mesh was also assessed. On the basis of electron spin resonance (ESR) results, O2- rather than OH is the main active species for the dye degradation by the Cu@CuO NWs mesh. With a marvelous combination of excellent flexibility, wide pH adaptation, and high efficiency, this easily recycled three dimensional Cu@CuO NWs architecture can afford new ideas for the Fenton chemistry.

Electrospun polyporous VN nanofibers for symmetric all-solid-state supercapacitors

To promote the energy density of symmetric all-solid-state supercapacitors (SCs), efforts have been dedicated to searching for high-performance electrode materials recently. In this paper, vanadium nitride (VN) nanofibers with mesoporous structure have been fabricated by a facile electrospinning method. Their crystal structures and morphology features were characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The mesoporous structure of VN nanofibers, which can provide short electrolyte diffusion routes and conducting electron transport pathways, is beneficial to their performance as a supercapacitor electrode. Under a stable electrochemical window of 1.0 V, VN nanofibers possess an excellent mass specific capacitance of 110.8 F/g at a scan rate of 5 mV/s. Moreover, the VN nanofibers were further assembled into symmetric all-solid-state SCs, achieving a high energy density of 0.89 mW·h/cm3 and a high power density of 0.016 W/cm3 over an operating potential range from 0 to 1.0 V. These results demonstrate that VN nanofibers could be potentially used for energy storage devices.