Yafei Liu

Degradation of methyl orange by composite photocatalysts nano-TiO2 immobilized on activated carbons of different porosities.

Composite photocatalysts TiO(2) immobilized on granular activated carbons with different porosities (TiO(2)/AC) were prepared by a novel approach, dip-hydrothermal method using peroxotitanate as precursor. The TiO(2)/AC composites were characterized by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy and the nitrogen absorption. Their photocatalytic activity was evaluated by degradation of methyl orange (MO). The results showed that nano-TiO(2) particles of anatase type were well deposited on the activated carbon surface. The porosity of activated carbon had significant influence on the adsorption, the amount of TiO(2) deposited on the external surface of AC and the activity of composite photocatalysts. The composite TiO(2)/AC made from proper mesoporosity AC exhibited higher catalytic activity than the mixture of powdered TiO(2) with AC. Furthermore, the mechanism of synergistic effect of AC adsorption and TiO(2) photocatalysis was discussed.

Carbon Electrode Material with High Densities of Energy and Power

Abstract Activated carbon (AC) samples as electrode materials were prepared by means of simultaneous physical-chemical activation using walnut shells as precursors. The porosity and surface chemistry of the resultant AC samples were studied by the nitrogen adsorption at 77 K, and FTIR spectrum. The testing supercapacitors were assembled with resultant carbon electrode and electrolyte of 6 mol·L −1 KOH solution. Their electrochemical properties were investigated by charge-discharge of constant current, cyclic voltammogram, impedance spectrum and so on. The results showed that the capacitor had low inner resistance, low leakage current, high stability, and capacitance retainability. The specific capacitance of AC increased with increasing BET specific surface area. The specific capacitance of the AC sample with a specific area of 1197 m 2 ·g −1 could be as high as 292 F·g −1 . At a discharge current of 80 mA, the corresponding specific energy density, power density, and maximum power of the supercapacitor are 7.3 Wh·kg −1 , 770 W·kg −1 , and 5.1 W·g −1 , respectively.

Novel 3D flower-like CoNi2S4/carbon nanotube composites as high-performance electrode materials for supercapacitors

Novel 3D flower-like CoNi2S4/carbon nanotube composites with a porous structure were designed through a facile precursor transformation approach as electrode materials for supercapacitors. The resulting samples are characterized by X-ray diffraction, Raman spectra, energy dispersive spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, and nitrogen adsorption–desorption. Their electrochemical performance was investigated by means of cyclic voltammetry, galvanostatic charge–discharge, impedance spectra and cycle life. By selecting carbon nanotubes as the conductive support for the growth of CoNi2S4, the as-obtained CoNi2S4/carbon nanotube composites displayed an ultrahigh specific capacitance of 2094 F g−1 at 1 A g−1 and a good rate capability (72% capacity retention at 10 A g−1). These results above suggest the great potential of the unique flower-like CoNi2S4/carbon nanotube composites in the development of high-performance electrode materials for supercapacitors.

Design and synthesis of hierarchical NiCo2S4@NiMoO4 core/shell nanospheres for high-performance supercapacitors

A novel electrode material of three-dimensional (3D) hierarchical NiCo2S4@NiMoO4 core/shell nanospheres for high-performance supercapacitors was successfully synthesized by a two-step method. First, ball-like NiCo2S4 was obtained by controlling the morphology through a hydrothermal method using diethanol amine as a new precipitant; second, the interconnected uniform NiMoO4 nanosheets were allowed to efficiently grow on the NiCo2S4 backbone by the hydrothermal method to form NiCo2S4@NiMoO4 core/shell nanospheres. The resultant hierarchical NiCo2S4@NiMoO4 core/shell nanospheres were characterized by X-ray diffraction, energy dispersive spectrometry, X-ray photoelectron spectroscopy, field-emission scanning electron microscopy, transmission electron microscopy and N2 adsorption and desorption. The electrochemical properties of the samples were evaluated though cyclic voltammetry, charge–discharge and electrochemical impedance spectroscopy in 6.0 M KOH electrolytic solution. The results showed that the hierarchical NiCo2S4@NiMoO4 core/shell nanospheres exhibited a very large specific capacitance of 1714 F g−1 at 1 A g−1, an outstanding cyclic stability with a capacitance retention of 96% after 5000 cycles of charge–discharge and a low resistance.

INFLUENCE OF PORE STRUCTURE ON THE ELECTROCHEMICAL PERFORMANCE OF ACTIVATED CARBON AS ELECTRODE MATERIAL FOR AQUEOUS SUPERCAPACITORS

Three activated carbon materials with different pore characteristics were prepared. The relationship between the electrochemical performances and the pore characteristics of the obtained carbons as electrode material for supercapacitors was elucidated. The results show that three carbon materials have almost equal specific-surface-area capacitance of 0.12 F ⋅ m-2. The energy density depends largely on the carbon surface area whereas the power density depends not only on the surface area, but also on the pore size and pore size distribution. The carbon sample with a BET surface area of 2000 m2 ⋅ g-1 and multimodal peak pore systems consisting of micropores at 1.5 nm and mesopores at about 3.8 nm exhibits excellent power density of 1662 W kg-1.

High performance of LiMnPO4/C prepared by hydrothermal reaction

Abstract LiMnPO4/C samples were prepared by hydrothermal reaction, and also by solid state reaction for the comparison. The samples characterised by X-ray diffraction, scanning electron microscope, particle size distribution and Roman spectra. The influence of solution pH and calcination temperature on the particle size of LiMnPO4 sample was studied. Results showed that the sample synthesised at the optimal conditions of pH=6·0 and 680°C had the biggest lattice of LiMnPO4 crystal and the narrowest particle size distribution. Compared with solid state reaction, the hydrothermal reaction produced a better carbon coating to form LiMnPO4/C composite. Electrochemical property was tested by charge–discharge and cyclic voltammetry. As a result, the capacity of the optimal sample is 108 mAh g–1 and the capacity retention is 70% after 30 cycles. The Electrochemical performance of LiMnPO4/C prepared by hydrothermal reaction is better than that produced by solid state reaction.