Ming Yan

Hexagonal prism-like hierarchical Co9S8@Ni(OH)2 core–shell nanotubes on carbon fibers for high-performance asymmetric supercapacitors

In this work, novel hierarchical cobalt sulfide@nickel hydroxide [Co9S8@Ni(OH)2] core–shell nanotube arrays supported on carbon fibers have been designed logically and synthesized for use as supercapacitors. The one-dimensional Co9S8 nanotubes (NTs) serve as an ideal backbone to improve the electrical conductivity of Ni(OH)2 nanosheets, whereas the ultrathin and redox active Ni(OH)2 nanosheets electrodeposited on the Co9S8 NTs greatly enhance the surface area and provide more electroactive sites for faradaic reaction. The optimized Co9S8@Ni(OH)2 electrode shows high specific capacitances of 149.44 mA h g−1 at the current density of 1 A g−1 and 75 mA h g−1 even at 10 A g−1. An asymmetric supercapacitor was successfully assembled with this unique hybrid nanostructure as the anode and an active carbon film as the cathode. The as-fabricated device shows high energy density (31.35 W h kg−1 at 252.8 W kg−1), high power density (2500 W kg−1 at 12.5 W h kg−1), as well as a long-term cycle stability (97.3% retention of its initial capacitance after 5000 cycles). The as-prepared hierarchical nanostructure shows great potential as a promising electrode material for energy storage applications.

Construction of nitrogen-doped graphene quantum dots-BiVO4/g-C3N4 Z-scheme photocatalyst and enhanced photocatalytic degradation of antibiotics under visible light

Development of high-efficiency photocatalysts for photocatalysis research has been a hotspot in recent years. In this study, an effective nitrogen-doped graphene quantum dots (NGQDs)-BiVO4/g-C3N4 Z-scheme heterojunction has been successfully prepared for environmental remediation. Antibiotics (tetracycline (TC), oxytetracycline (OTC) and ciprofloxacin (CIP)) were chosen as target pollutants to explore the photocatalytic performance. Results showed that both the BiVO4/g-C3N4 ratio (Bi/CN ratio) and NGQDs amount have an important influence on the antibiotics degradation. Under our experimental conditions, the optimum Bi/CN ratio was 1u2006:u20062 and optimum NGQDs addition amount was 5 wt%, with the corresponding 5% NGQDs-Bi/2CN sample showing the highest photocatalytic efficiency (91.5% in 30 min with TC). By further study based on electron spin resonance (ESR) and active species trapping experiments, the enhanced photocatalytic property could be ascribed to the crucial role of NGQDs and Z-scheme photocatalytic system, which not only accelerated the separation of the charge carriers but also exhibited a strong oxidation and reduction ability for efficient degradation of organic pollutants.

Fabrication and evaluation of artemisinin-imprinted composite membranes by developing a surface functional monomer-directing prepolymerization system.

Inspired by a surface functional monomer-directing prepolymerization system, a straightforward and effective synthesis method was first developed to prepare highly regenerate and perm-selective molecularly imprinted composite membranes of artemisinin (Ars) molecules. Attributing to the formation of the prepolymerization system, Ars molecules are attracted and bound to the membrane surface, hence promoting the growth of homogeneous and high-density molecular recognition sites on the surface of membrane materials. Afterward, a two-step-temperature imprinting procedure was carried out to prepare the novel surface functional monomer capping molecularly imprinted membranes (FMIMs). The as-prepared FMIMs not only exhibited highly adsorption capacity (11.91 mg g(-1)) but also showed an outstanding specific selectivity (imprinting factor α is 4.50) and excellent perm-selectivity ability (separation factor β is 10.60) toward Ars molecules, which is promising for Ars separation and purification.

Construction of hierarchical FeCo2O4@MnO2 core-shell nanostructures on carbon fibers for high-performance asymmetric supercapacitor

In this work, the novel hierarchical FeCo2O4@MnO2 core-shell nanosheet arrays have been synthesized by a facile hydrothermal method, which are grown directly on a flexible carbon fiber (CF) as an integrated electrode for supercapacitors. Scanning electron microscopy and high-resolution transmission electron microscopy measurements illustrate that MnO2 nanoflakes uniformly wrap around the surface of two-dimensional FeCo2O4 nanosheets. The electrode exhibits high areal capacitance of 4.8Fcm-2 at a current density of 1mAcm-2. Moreover, an asymmetric FeCo2O4@MnO2//active carbon (AC) cell is successfully fabricated. The asymmetric supercapacitor (ASC) displays high energy density/power density (22.68Whkg-1 at 406.01Wkg-1 and 7.06Whkg-1 at 1802.5Wkg-1), as well as excellent cycling stability with 90.1% of the initial capacitance after 5000 continuous cycles. Moreover, two ASCs connected in series can light a LED. These performances demonstrate great potential of the designed ASC in the field of energy storage due to their remarkable electrochemical properties.

Flexible yolk-shelled NiCo2S4 hollow spheres/RGO film electrodes for efficient supercapacitive energy storage

Flexible yolk-shelled NiCo2S4 hollow spheres/reduced graphene oxide (RGO) hybrid lamellar films were successfully fabricated by developing a facile strategy of vacuum filtration. After constructing the sandwich-like structures, the NiCo2S4 hollow spheres were inserted in-between the RGO nanosheets, which effectively prevented the self-restacking of RGO nanosheets and increased the interlayer spacing, leading to fast ion penetration and diffusion. The as-prepared NiCo2S4/2RGO hybrid lamellar films with excellent conductivity delivered an appreciable capacitance of 1000.5 F g−1 at 1 A g−1. Moreover, an asymmetric supercapacitor (ASC) was successfully synthesized utilizing activated carbon (AC) and NiCo2S4/2RGO hybrid lamellar films as the negative electrode and positive electrode, which manifested a high energy density (15.4 W h kg−1) and power density (2227.3 W kg−1) coupled with remarkable cycling stability (80.5% retention over 5000 cycles). After charging, two ASC devices connected in series were capable of lighting two red LEDs connected in parallel for at least 2.0 minutes.

Synthesis of C/Co3O4 composite mesoporous hollow sphere sandwich graphene films for high-performance supercapacitors

Carbon/Co3O4 composite mesoporous hollow spheres (C/Co3O4 MHSs) and graphene oxide were successfully synthesized to fabricate hybrid films. Unique sandwich and mesoporous structures can provide more pathways for electrolyte transmission and achieve excellent electrochemical performance. After combining with C/Co3O4 MHSs, the hybrid films can achieve a specific capacity of 1266.0 F g−1 at a current density of 1 A g−1, which is much higher than that of the C/Co3O4 MHSs (153.9 F g−1) and reduced graphene oxide (rGO) films (213.5 F g−1). Moreover, a rGO/C/Co3O4//rGO asymmetric supercapacitor (ASC) device was fabricated. The ASC exhibits a high energy density of 32.7 Wh kg−1 (power density of 800 W kg−1) and an excellent cycling stability with 85.9% capacitance retention after 5000 cycles. Besides, white LED bulbs (3.2 V) can be lit by two ASCs in series.