Chengchun Tang

Facile Synthesis of Graphene-Like Copper Oxide Nanofilms with Enhanced Electrochemical and Photocatalytic Properties in Energy and Environmental Applications

Novel graphene-like CuO nanofilms are grown on a copper foam substrate by in situ anodization for multifunctional applications as supercapacitor electrodes and photocatalysts for the degradation of dye pollutants. The as-prepared CuO consists of interconnected, highly crystalline, conductive CuO nanosheets with hierarchical open mesopores and a large surface area. The CuO nanofilms supported on a copper foam are employed as freestanding, binder-free electrodes for supercapacitors, which exhibit wonderful electrochemical performance with a large specific capacitance (919 F g(-1) at 1 A g(-1)), an excellent cycling stability (7% capacitance loss after 5000 cycles), and a good rate capability (748 F g(-1) at 30 A g(-1)). The porous CuO nanofilms also demonstrate excellent photocatalytic activities for degradation of methylene blue, with a degradation rate 99% much higher than 54% of the commercial CuO powders after 60 min. This excellent energy storage and photocatalytic performance of the graphene-like CuO nanofilms can open a new avenue for large-scale applications in energy and environmental fields.

Hierarchical, porous CuS microspheres integrated with carbon nanotubes for high-performance supercapacitors.

Carbon nanotubes (CNTs) incorporated porous 3-dimensional (3D) CuS microspheres have been successfully synthesized via a simple refluxing method assisted by PVP. The composites are composed of flower-shaped CuS secondary microspheres, which in turn are assembled with primary nanosheets of 15–30 nm in thickness and fully integrated with CNT. The composites possess a large specific surface area of 189.6 m2 g−1 and a high conductivity of 0.471 S cm−1. As electrode materials for supercapacitors, the nanocomposites show excellent cyclability and rate capability and deliver an average reversible capacitance as high as 1960 F g−1 at a current density of 10 mA cm−2 over 10000 cycles. The high electrochemical performance can be attributed to the synergistic effect of CNTs and the unique microstructure of CuS. The CNTs serve as not only a conductive agent to accelerate the transfer of electrons in the composites, but also as a buffer matrix to restrain the volume change and stabilize the electrode structure during the charge/discharge process. The porous structure of CuS also helps to stabilize the electrode structure and facilitates the transport for electrons.

Facile synthesis of α-Fe2O3 nanodisk with superior photocatalytic performance and mechanism insight

Abstract Intrinsic short hole diffusion length is a well-known problem for α-Fe2O3 as a visible-light photocatalytic material. In this paper, a nanodisk morphology was designed to remarkably enhance separation of electron-hole pairs of α-Fe2O3. As expected, α-Fe2O3 nanodisks presented superior photocatalytic activity toward methylene blue degradation: more than 90% of the dye could be photodegraded within 30 min in comparison with a degradation efficiency of 50% for conventional Fe2O3 powder. The unique multilayer structure is thought to play a key role in the remarkably improved photocatalytic performance. Further experiments involving mechanism investigations revealed that instead of high surface area, ·OH plays a crucial role in methylene blue degradation and that O·2− may also contribute effectively to the degradation process. This paper demonstrates a facile and energy-saving route to fabricating homogenous α-Fe2O3 nanodisks with superior photocatalytic activity that is suitable for the treatment of contaminated water and that meets the requirement of mass production.

Hierarchical porous CuO nanostructures with tunable properties for high performance supercapacitors

We report a novel, low-cost strategy to synthesize copper oxide (CuO) nanostructures as high-performance supercapacitor electrodes using an alkaline solution oxidation method. The structure, morphological features, surface area and pore size distribution of the products are tuned using different types of surfactants. The CuO electrode obtained from sodium dodecyl sulfate (SDS) presents the best electrochemical performance due to the synergies arising from the large surface area and pore volume created by the ultrathin nanoleaves constituting the flower-shape nanostructure. The electrode delivers a remarkable specific capacitance of 520 F g−1 at 1 A g−1 and a high rate capacitance of 405 F g−1 at 60 A g−1 with more than 95% Coulombic efficiency after 3500 cycles.

Blue emitting BCNO phosphors with high quantum yields

The blue emitting BCNO phosphors with high quantum yields were prepared at 625 °C using boric acid, melamine and hexamethylenetetramine as raw materials. The BCNO phosphors have turbostratic boron nitride structure and consist of nanocrystallites 5 nm in size. The emission and excitation spectra can be tuned by the contents of raw materials and sintering temperatures. The quantum yields of BCNO phosphors can be up to 99% with increasing boric acid. The FTIR spectra suggested that the quantum yield can be improved with increasing strength of B–N and B–N–B bonds, and formation of B–O–B bonds, while it decreased with enhancement of CC bonds. The emission decay curves indicated that the decay process was related to two luminescence centers corresponding to carbon and oxygen impurities. In addition, the high temperature emission spectra disclosed that the nitrogen vacancy would participate in the blue light emission process at a certain heating temperature. The blue emitting BCNO phosphors with high quantum yields have great potential application in luminescence and display areas.

Cost-effective CuO nanotube electrodes for energy storage and non-enzymatic glucose detection

A facile strategy is developed for the in situ synthesis of low-cost, freestanding, binder-free CuO nanotube electrodes on a conducting Cu foil, totally eliminating non-active materials and extra processing steps. The synergy arising from the ameliorating structure, such as high porosity, large surface area and the ability for fast electron transport, make CuO nanotube electrodes ideal multi-functional electrochemical devices with excellent pseudocapacitive performance and a remarkable sensitivity to glucose for use as non-enzymatic biosensors (NGBs). The electrodes deliver remarkable specific capacitances of 442 and 358 F g−1 at current densities of 1 and 20 A g−1, respectively. The capacitance loss after 5000 cycles is only 4.6% at 1 A g−1, reflecting the excellent cyclic stability of the supercapacitor. The biosensor made from CuO nanotubes presents an extremely rapid and accurate response to glucose in blood in a wide, linear range of 100 μM to 3 mM, with a sensitivity of 2231 μA mM−1 cm−2. These interesting discoveries may open up the potential for the further development of new, multi-functional electrodes possessing both excellent energy storage and biosensory capabilities.

Degradation of methyl orange through synergistic effect of zirconia nanotubes and ultrasonic wave.

Zirconia nanotubes with a length of 25 μm, inner diameter of 80 nm, and wall thickness of 35 nm were prepared by anodization method in mixture of formamide and glycerol (volume ratio = 1:1) containing 1 wt% NH(4)F and 1 wt% H(2)O. Experiments showed that zirconia nanotubes and ultrasonic wave had synergistic degradation effect for methyl orange and the efficiency of ultrasonic wave increased by more than 7 times. The decolorization percentage was influenced by pH value of the solution. Methyl orange was easy to be degraded in acidic solution. The decolorization percentage of methyl orange reached 97.6% when degraded for 8h in 20mg/L methyl orange solution with optimal pH value 2. The reason of synergistic degradation effect for methyl orange might be that adsorption of methyl orange onto zirconia nanotubes resulted in the easy degradation of the methyl orange through ultrasonic wave.

Spectral properties and luminescence mechanism of red emitting BCNO phosphors

Red emitting (λem = 620 nm) BCNO phosphors were synthesized at 650 °C with solid state reaction method using boric acid and hexamethy lenetetramine as raw materials. The BCNO phosphors have turbostratic boron nitride structure and particle sizes are in micro scale. Carbon and oxygen elements were bonded to boron and nitrogen to form BCNO phosphors. The emission peaks were shifted from blue light (420–470 nm) to red light (590–620 nm) with increasing sintering temperature, heating time and the ratio of boric acid to hexamethy lenetetramine, which was induced by partially formed BCNO and completely formed BCNO phosphors. The decay curves and emission spectra indicated that the red emission was induced by two luminescence centers, corresponding to longer lifetime τ1 and short lifetime τ2. The ultraviolet visible absorption spectra disclosed that the optical band gap was changed from 1.75 eV to 2.0 eV with different preparation conditions. The high temperature emission spectra suggested that the nitrogen defects levels served as electron traps and attended the red emission. The luminescence mechanism of BCNO phosphors was stated by a simplified energy level diagram. The red emission BCNO phosphors have good thermal stability and great potential application on lighting, display, solar cell and biomedical fields.

Free-standing membranes made of activated boron nitride for efficient water cleaning

Developing membranes with excellent mechanical strength and chemical stability is a practically important issue for efficient removal of pollutants from wastewater. In this work, we report on a free-standing membrane fabrication from an activated boron nitride (ABN) micro-ribbon. The membrane techniques we used, combine the intrinsic active adsorption competence of ABN and the mechanical advantages of conventional membrane filtration. The obtained membranes show an excellent removal ability of water pollutants through a simple filtration adsorption process. The examined pollutants include toxic metallic ions and organics. We showed that the dye (like methylene blue) removal ability significantly exceeded that of activated carbon by an order of magnitude at least; lead ions (Pb2+) in wastewater can be nearly fully removed, the starting 5 mg L−1 concentration was reduced to less than 0.01 mg L−1 after the 600 μm-thickness membrane adsorption filtration. Moreover, the membranes can be stacked together to further improve the adsorption capacity because of their high permeability. The excellent reusable performance of the filtration membranes was also confirmed. We believe that the reported work should open the way toward the practical application of ABN membranes in the field of wastewater purification.

Catalytic activity of ZrO 2 nanotube arrays prepared by anodization method

ZrO2 nanotube arrays were prepared by anodization method in aqueous electrolyte containing (NH4)2SO4 and NH4F. The morphology and structure of nanotube arrays were characterized through scanning electron microscope, X-ray diffraction, and infrared spectra analysis. The zirconia nanotube arrays were used as catalyst in esterification reaction. The effects of calcination temperature and electrolyte concentration on catalytic esterification activity have been investigated in detail. Experiments indicate that nanotube arrays have highest catalytic activity when the concentration of (NH4)2SO4 is 1 mol/L, the concentration of NH4F is 1 wt%, and the calcination temperature is 400°C. Esterification reaction yield of as much as 97% could be obtained under optimal conditions.