Huilin Hou

General strategy for fabricating thoroughly mesoporous nanofibers.

Recently, preparation of mesoporous fibers has attracted extensive attentions because of their unique and broad applications in photocatalysis, optoelectronics, and biomaterials. However, it remains a great challenge to fabricate thoroughly mesoporous nanofibers with high purity and uniformity. Here, we report a general, simple and cost-effective strategy, namely, foaming-assisted electrospinning, for producing mesoporous nanofibers with high purity and enhanced specific surface areas. As a proof of concept, the as-fabricated mesoporous TiO2 fibers exhibit much higher photocatalytic activity and stability than both the conventional solid counterparts and the commercially available P25. The abundant vapors released from the introduced foaming agents are responsible for the creation of pores with uniform spatial distribution in the spun precursor fibers. The present work represents a critically important step in advancing the electrospinning technique for generating mesoporous fibers in a facile and universal manner.

Superior thoroughly mesoporous ternary hybrid photocatalysts of TiO2/WO3/g-C3N4 nanofibers for visible-light-driven hydrogen evolution

A novel and highly efficient visible-light-driven photocatalyst with robust stability, made up of thoroughly mesoporous TiO2/WO3/g-C3N4 ternary hybrid nanofibers, has been fabricated through a foaming-assisted electrospinning process followed by a solution dipping process. These fibers, without the assistance of a noble metal, yielded a high visible-light-driven photocatalytic H2 release rate of ∼286.6 μmol h−1, which was 65 times greater than that displayed by the pure TiO2 counterparts.

Efficient Photocatalytic Activities of TiO2 Hollow Fibers with Mixed Phases and Mesoporous Walls.

Currently, Degussa P25, with the typical mixed phases of anatase and rutile TiO2, is widely applied as the commercial photocatalysts. However, there are still some of obstacles for the P25 nanoparticles with totally high photocatalytic activities, especially for the catalytic stability due to their inevitable aggregation of the nanoparticles when used as the photocatalysts. In the present work, we reported the exploration of a novel TiO2 photocatalyst, which could offer an ideal platform for synergetic combination of the mixed-phase composition, hollow architecture and mesoporous walls for the desired excellent photocatalytic efficiency and robust stability. The mesoporous TiO2 hollow nanofibers were fabricated via a facile single capillary electrospinning technique, in which the foaming agents were used for creating mesopores throughout the walls of the hollow fibers. The obtained hollow fibers exhibit a high purity and possess the mixed phases of 94.6% anatase and 5.4% rutile TiO2. As compared to P25, the as-fabricated mesoporous TiO2 hollow fibers exhibited much higher efficient photocatalytic activities and stabilities toward the hydrogen evolution with a rate of ~499.1 μmol g−1·h−1 and ~99.5% degradation Rhodamine B (RhB) in 60 min, suggesting their promising application in efficient photocatalysts.

Highly Efficient Photocatalytic Hydrogen Evolution in Ternary Hybrid TiO2/CuO/Cu Thoroughly Mesoporous Nanofibers

Development of novel hybrid photocatalysts with high efficiency and durability for photocatalytic hydrogen generation is highly desired but still remains a grand challenge currently. In the present work, we reported the exploration of ternary hybrid TiO2/CuO/Cu thoroughly mesoporous nanofibers via a foaming-assisted electrospinning technique. It is found that by adjusting the Cu contents in the solutions, the unitary (TiO2), binary (TiO2/CuO, TiO2/Cu), and ternary (TiO2/CuO/Cu) mesoporous products can be obtained, enabling the growth of TiO2/CuO/Cu ternary hybrids in a tailored manner. The photocatalytic behavior of the as-synthesized products as well as P25 was evaluated in terms of their hydrogen evolution efficiency for the photodecomposition water under Xe lamp irradiation. The results showed that the ternary TiO2/CuO/Cu thoroughly mesoporous nanofibers exhibit a robust stability and the most efficient photocatalytic H2 evolution with the highest release rate of ∼851.3 μmol g(-1) h(-1), which was profoundly enhanced for more than 3.5 times with respect to those of the pristine TiO2 counterparts and commercial P25, suggesting their promising applications in clean energy production.

Tailored Fabrication of Thoroughly Mesoporous BiVO4 Nanofibers and Their Visible-Light Photocatalytic Activities

Bismuth vanadate (BiVO4) is considered as a potentially attractive candidate for the O2 evolution and photodegradation of organic pollutants. In an effort to develop visible-light-driven photocatalysts with high activities, the thoroughly mesoporous BiVO4 nanofibers were fabricated via a foaming-assisted electrospinning strategy. It was found that the introduced foaming agent of diisopropyl azodiformate within the solutions plays a crucial role on the formation of thoroughly mesoporous BiVO4 nanofibers, making their growth tunable. The obtained mesoporous BiVO4 nanofibers possess well-defined one-dimensional mesoporous architectures with high purity in their morphology and a surface area of 22.5 m(2)/g, which is ∼4 times that of conventional solid counterparts (5.8 m(2)/g). Accordingly, they exhibit much higher efficient photocatalytic activities toward the degradation of rhodamine B under visible-light irradiation, which is 3 times that of conventional solid counterparts, suggesting their promising application as novel and efficient photocatalysts for water purification.

Tailored Electrospinning of WO3 Nanobelts as Efficient Ultraviolet Photodetectors with Photo-Dark Current Ratios up to 1000

In this work, polycrystalline WO3 nanobelts were fabricated via an electrospinning process combined with subsequent air calcination. The resultant products were characterized by X-ray diffraction, field-emission scanning electron microscopy, and high-resolution transmission electron microscopy in regard to the structures. It has been found that the applied voltage during the electrospinning process played the determined role in the formation of the WO3 nanobelts, allowing the controlled growth of the nanobelts. The ultraviolet (UV) photodetector assembled by an individual WO3 nanobelt exhibits a high sensitivity and a precise selectivity to the different wavelength lights, with a very low dark current and typical photo-dark current ratio up to 1000, which was the highest for any WO3 photodectectors ever reported. This work could not only push forward the facile preparation of WO3 nanobelts but also represent, for the first time, the possibility that the polycrystalline WO3 nanobelts could be a promising building block for the highly efficient UV photodetectors.

High-performance solar-blind ultraviolet photodetector based on electrospun TiO2-ZnTiO3 heterojunction nanowires

High-performance solar-blind UV (ultraviolet) photodetectors (PDs) based on low-dimension semiconducting nanostructures with high sensitivity, excellent cycle stability, and the ability to operate in harsh environments are critical for solar observations, space communication, UV astronomy, and missile tracking. In this study, TiO2-ZnTiO3 heterojunction nanowire-based PDs are successfully developed and used to detect solar-blind UV light. A photoconductive analysis indicates that the fabricated PDs are sensitive to UV illumination, with high sensitivity, good stability, and high reproducibility. Further analysis indicates that the rich existence of grain boundaries within the TiO2-ZnTiO3 nanowire can greatly decrease the dark current and recombination of the electron-hole pairs and thereby significantly increase the device’s photosensitivity, spectra responsivity (1.1 × 106), and external quantum efficiency (4.3 × 108 %). Moreover, the PDs exhibit good photodetective performance with fast photoresponse and recovery and excellent thermal stability at temperatures as high as 175 °C. According to these results, TiO2-ZnTiO3 heterojunction nanowires exhibit great potential for applications in high-performance optical electronics and PDs, particularly next-generation photodetectors with the ability to operate in harsh environments.

Foaming-assisted electrospinning of large-pore mesoporous ZnO nanofibers with tailored structures and enhanced photocatalytic activity

1D large-pore mesoporous ZnO materials have attracted tremendous attention because of their outstanding properties and promising applications in a wide range of fields. In the present work, we report the fabrication of large-pore mesoporous ZnO nanofibers via an improved electrospinning strategy, namely, the foaming-assisted electrospinning technique, combined with subsequent calcination treatment. The as-fabricated large-pore mesoporous nanofibers were systematically characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Brunauer–Emmett–Teller (BET) specific surface area (SBET). The obtained products possess well-designed 1D mesoporous nanostructure with high purity and homogeneous large pore sizes. It is found that the content of the foaming agent within the solutions plays a crucial role in the formation of large-pore mesoporous ZnO nanofibers, enabling the growth of the fibers in a controlled manner. The resultant large-pore mesoporous nanofibers exhibit excellent photocatalytic activity and significant stability for hydrogen production compared to conventional solid nanofibers. The present work suggests a facile preparation of the large-pore mesoporous ZnO nanofibers, which may open new doors for their potential applications in photocatalysts.

Shape-Enhanced Photocatalytic Activities of Thoroughly Mesoporous ZnO Nanofibers.

1D mesoporous materials have attracted extensive interest recently, owning to their fascinating properties and versatile applications. However, it remains as a grand challenge to develop a simple and efficient technique to produce oxide nanofibers with mesoporous architectures, controlled morphologies, large surface areas, and optimal performances. In this work, a facile foaming-assisted electrospinning strategy with foaming agent of tea saponin is used to produce thoroughly mesoporous ZnO nanofibers with high purity and controlled morphology. Interestingly, mesoporous fibers with elliptical cross-section exhibit the significantly enhanced photocatalytic activity for hydrogen production, as compared to the counterparts with circular and rectangular cross-sections, and they also perform better than the commercial ZnO nanopowders. The unexpected shape dependence of photocatalytic activities is attributed to the different stacking modes of the mesoporous fibers, and a geometrical model is developed to account for the shape dependence. This work represents an important step toward producing thoroughly mesoporous ZnO nanofibers with tailored morphologies, and the discovery that fibers with elliptical cross-section render the best performance provides a valuable guideline for improving the photocatalytic performance of such mesoporous nanomaterials.

Enhanced visible-light responsive photocatalytic activity of N-doped TiO2 thoroughly mesoporous nanofibers

Improving the photocatalytic efficiency of TiO2 semiconductor is crucially important and highly desired for its practical applications. In the present work, aiming to broaden the photoresponse window and limit the photocatalyst aggregation, we reported the exploration of N-doped TiO2 thoroughly mesoporous nanofibers with high purity in morphology via a foaming-assisted electrospinning strategy. The foaming agents and urea were introduced in the raw materials to create the mesopores and incorporate the N dopants into the conventional solid TiO2 nanofibers, respectively, which could be accomplished simultaneously over one-step calcination process. The synergetic combination of N dopants and one-dimensional mesoporous nanostructure allow the TiO2 fibers to exhibit significantly enhanced visible-light photocatalytic activity toward the Rhodamine B and hydrogen evolution, as compared to those of N-doped solid and intrinsic thoroughly mesoporous counterparts, suggesting their promising applications in water purification and energy supply.