Shanmu Dong

Nitrogen-doped graphene nanosheets with excellent lithium storage properties

In this work, nitrogen-doped graphene nanosheets serving as lithium storage materials are presented. The nitrogen-doped graphene nanosheets were prepared by heat treatment of graphite oxide under an ammonia atmosphere at 800 degrees C for 2 h. Scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy were employed to characterize the prepared product as nitrogen-doped graphene nanosheets with a doping level of ca. 2% nitrogen, where the N binding configuration of the graphene includes 57.4% pyridinic, 35.0% pyrrolic and 7.6% graphitic N atoms. Galvanostatic charge/discharge experiments revealed that these nitrogen-doped graphene nanosheets exhibited a high reversible capacity (900 mA h g(-1) at 42 mA g(-1) (1/20 C)), excellent rate performance (250 mA h g(-1) at a current density of 2.1 A g(-1) (2.5 C)), and significantly enhanced cycling stability, which demonstrated nitrogen-doped graphene nanosheets to be a promising candidate for anode materials in high rate lithium-ion batteries.

Synthesis of Nitrogen-Doped MnO/Graphene Nanosheets Hybrid Material for Lithium Ion Batteries

Nitrogen-doped MnO/graphene nanosheets (N-MnO/GNS) hybrid material was synthesized by a simple hydrothermal method followed by ammonia annealing. The samples were systematically investigated by X-ray diffraction analysis, Raman spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, and atomic force microscopy. N-doped MnO (N-MnO) nanoparticles were homogenously anchored on the thin layers of N-doped GNS (N-GNS) to form an efficient electronic/ionic mixed conducting network. This nanostructured hybrid exhibited a reversible electrochemical lithium storage capacity as high as 772 mAh g(-1) at 100 mA g(-1) after 90 cycles, and an excellent rate capability of 202 mA h g(-1) at a high current density of 5 A g(-1). It is expected that N-MnO/GNS hybrid could be a promising candidate material as a high capacity anode for lithium ion batteries.

One dimensional MnO2/titanium nitride nanotube coaxial arrays for high performance electrochemical capacitive energy storage

One dimensional MnO2/titanium nitride nanotube coaxial arrays have been designed for a high performance electrochemical capacitive energy storage system based on the concept of fabricating an efficient, fast charge separation network. This nanostructured composite material was prepared by electrodepositing mesoporous MnO2 into TiN nanotube arrays (TiN NTA), which are prepared by anodization of a Ti foil substrate and subsequent nitridation using ammonia annealing. The electrodeposited mesoporous MnO2 inside the electrically conductive framework of a TiN nanotube has been found to show high specific capacitance (681.0 F g−1 at 2 A g−1), excellent rate capability (55% capacitance retention from 2 to 2000 mV s−1), and a long cycle life (3% capacitance loss after 1000 cycles). These results demonstrate that this coaxial composite nanostructure is very promising for high performance supercapacitors.

Silica sol–gel composite film as an encapsulation matrix for the construction of an amperometric tyrosinase-based biosensor

An amperometric tyrosinase enzyme electrode for the determination of phenols was developed by a simple and effective immobilization method using sol-gel techniques. A grafting copolymer was introduced into sol-gel solution and the composition of the resultant organic-inorganic composite material was optimized, the tyrosinase retained its activity in the sol-gel thin film and its response to several phenol compounds was determined at 0 mV vs. Ag/AgCl (sat. KCl). The dependences of the current response on pH, oxygen level and temperature were studied, and the stability of the biosensor was also evaluated. The sensitivity of the biosensor for catechol, phenol and p-cresol was 59.6, 23.1 and 39.4 microA/mM, respectively. The enzyme electrode maintained 73% of its original activity after intermittent use for three weeks when storing in a dry state at 4 degrees C.

Graphene oxide nanosheets/multi-walled carbon nanotubes hybrid as an excellent electrocatalytic material towards VO2+/VO2+ redox couples for vanadium redox flow batteries

A graphene oxide nanosheets/multi-walled carbon nanotubes (GO/MWCNTs) hybrid with excellent electrocatalytic redox reversibility towards VO2+/VO2+ redox couples for vanadium redox flow batteries (VRFB) has been prepared by an electrostatic spray technique after efficient ultrasonic treatment. The structures and electrochemical properties of GO/MWCNTs are investigated by transmission electron microscopy, scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy and cyclic voltammetry. GO/MWCNTs are shown to be cross-linked and form an electrocatalytic hybrid with an effective mixed conducting network, leading to efficiently fast ion and electron transport characteristics. Compared with the pure GO nanosheets and MWCNTs, GO/MWCNTs deliver a much better electrocatalytic redox reversibility towards the positive VO2+/VO2+ couple, especially for the reduction from VO2+ to VO2+. The excellent experimental results demonstrate that the newly developed hybrid material holds great promise in the application of VRFB.

Mesoporous NiCo2O4 nanoflakes as electrocatalysts for rechargeable Li–O2 batteries

Herein, we report the facile synthesis of mesoporous NiCo(2)O(4) nanoflakes and their application in nonaqueous Li-O(2) batteries as cathode catalysts. The assembled Li-O(2) batteries presented lower overpotentials and enhanced cyclability, which should be attributed to the superior electrocatalytic activity and the mesoporous nanostructure of NiCo(2)O(4).

Coaxial NixCo2x(OH)(6x)/TiN Nanotube Arrays as Supercapacitor Electrodes

NixCo2x(OH)6x, as a precursor of intensively studied NiCo2O4, has been directly deposited into self-standing titanium nitride nanotube array (TiN NTA) grid monolithic supports to form a coaxial nanostructured electrode for supercapacitors. With TiN NTA substrates providing a large surface area, fast electron transport, and enhanced structure stability, this NixCo2x(OH)6x/TiN electrode exhibits superior pseudocapacitive performance with a high specific capacitance of 2543 F g(-1) at 5 mV s(-1), remarkable rate performance of 660 F g(-1) even at 500 mV s(-1), and promising cycle performance (about 6.25% capacitance loss for 5000 cycles). Interestingly, the NixCo2x(OH)6x/TiN NTA electrode outperforms the NiCo2O4/TiN NTA electrode, indicating that this self-standing NixCo2x(OH)6x/TiN NTA monolith is a promising candidate for high-performance supercapacitor applications.

Mesoporous Coaxial Titanium Nitride-Vanadium Nitride Fibers of Core–shell Structures for High-Performance Supercapacitors

In this study, titanium nitride-vanadium nitride fibers of core-shell structures were prepared by the coaxial electrospinning, and subsequently annealed in the ammonia for supercapacitor applications. These core-shell (TiN-VN) fibers incorporated mesoporous structure into high electronic conducting transition nitride hybrids, which combined higher specific capacitance of VN and better rate capability of TiN. These hybrids exhibited higher specific capacitance (2 mV s(-1), 247.5 F g(-1)) and better rate capability (50 mV s(-1), 160.8 F g(-1)), which promise a good candidate for high-performance supercapacitors. It was also revealed by electrochemical impedance spectroscopy (EIS) and X-ray photoelectron spectroscopy (XPS) characterization that the minor capacitance fade originated from the surface oxidation of VN and TiN.

Facile Preparation of Mesoporous Titanium Nitride Microspheres for Electrochemical Energy Storage

In this study, mesoporous TiN spheres with tunable diameter have been fabricated via a facile template-free strategy. Under ammonia atmosphere, mesoporous TiO₂ spheres are directly converted into mesoporous TiN spheres with the addition of cyanamide to retain the original morphology. The electrochemical performance of the resultant mesoporous TiN spheres demonstrates that this material can be a promising electrode material for nonaqueous supercapacitors with high energy densities.

Molybdenum nitride based hybrid cathode for rechargeable lithium-O2 batteries

Molybdenum nitride/nitrogen-doped graphene nanosheets (MoN/NGS) are synthesized and used as an alternative O(2) electrode for Li-O(2) batteries. In comparison with electrocatalysts proposed previously, this hybrid cathode exhibits a high discharge potential (around 3.1 V) and a considerable specific capacity (1490 mA h g(-1), based on carbon + electrocatalyst).