Hongwei Che

Facile synthesis of porous cobalt oxide microplates and their lithium ion storage properties

Abstract Porous cobalt oxide (Co3O4) microplates have been successfully synthesised via a facile thermal decomposition from plate-like cobalt oxalate complex precursors. The microstructures and morphologies of the obtained Co3O4 materials are characterised by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and N2 adsorption–desorption techniques. The characterisation results show that the obtained Co3O4 microplates are composed of plate-like polycrystalline nanoparticles with lengths of ∼20 nm and widths of ∼10 nm. In addition, these nanoplates aggregate each other to form the porous network with an average pore size of ∼18·9 nm. The obtained porous Co3O4 microplates exhibit high discharge–charge capacities and good rate performances, suggesting a promising application as anode materials for Li ion batteries.

ZnCo2O4@MnCo2O4 heterojunction structured nanosheets for high-performance supercapacitor

ZnCo2O4@MnCo2O4 heterojunction structured nanosheets were successfully prepared by simple and effective hydrothermal reaction. The obtained heterojunction structured had large specific surface area, good structural stability, and excellent electrical conductivity. Therefore, they were expected to become ideal electrochemical materials. As expected, a series of electrochemical tests showed ZnCo2O4@MnCo2O4 heterojunction structured nanosheets demonstrate high specific capacitance (254xa0Fxa0g−1 at the current density of 1xa0Axa0g−1). Good stability of charge–discharge, when the current density was 10xa0Axa0g−1, the capacity can still maintain 186xa0Fxa0g−1. Especially, the maximum energy density of asymmetric supercapacitors based on ZnCo2O4@MnCo2O4 and activated carbon at 750xa0Wxa0Kg−1 was 19.12xa0Whxa0Kg−1, and the cycle stability was good, after 2000 cycles, the capacitance retention rate was 98.5%. For practice application, the commercial LED lights can be lighted by two supercapacitor units in series. It shows that the synthetic electrode material has great potential in the energy storage equipment.

Preparation of mesoporous nanocrystalline tetragonal zirconia for catalytic methane combustion

Abstract Mesoporous nanocrystalline tetragonal zirconia (ZrO2) materials were synthesised via combining the soft templating method with the solid–liquid method. In brief, mesostructured zirconium hybrids were first prepared via the soft templating method and then ground with solid copper nitrate salts followed by low temperature heat treatment and further high temperature calcination in air. Finally, mesoporous nanocrystalline tetragonal ZrO2 materials were obtained after etching in acid solution. The characterisation results indicate that the obtained mesoporous ZrO2 materials have higher specific surface areas in the range of 100–300 m2 g−1 and pore diameters centred at 4·0–5·0 nm. The pore walls are composed of tetragonal ZrO2 nanocrystalline particles with an average size of 1–15 nm. These mesoporous nanocrystalline tetragonal ZrO2 materials as catalysts demonstrate good catalytic activity toward methane combustion, characterised by lower conversion temperatures (650–700°C) and active energies (75–90 kJ mol−1) than those of the reported ZrO2 materials, meaning their potential applications as catalysts or catalyst supporters in methane combustion.

Hexagonal mesoporous fluorescent hybrid materials with electron acceptor viologen units in the framework

Mesoporous MCM-41-type fluorescent hybrid materials with methylene viologen units in the framework have been synthesized via the co-hydrolysis and -condensation of dichloride of N,N′-bis(triethoxysilylmethyl)-4,4′-bipyridinium (VP) and tetraethoxysilane (TEOS). The obtained hybrid materials are characterized by the small-angle X-ray diffraction (SAXRD), high-resolution transmission electron microscope (HR-TEM), Fourier transform infrared spectrometer (FTIR), solid-state 29Si NMR spectrum, nitrogen adsorption/desorption analyse, diffuse reflectance UV–VIS (DR UV-Vis), and confocal laser scanning fluorescence microscopy (CLSFM). The results show that the VP units are covalently bonded into the silica framework to form mesoporous hybrid materials. The obtained hexagonal mesoporous hybrid materials are found to emit fluorescence at ca.380xa0nm and 420xa0nm. The fluorescent intensity enhances with increasing the amount of the VP occupied in the silica framework, and it is not affected by the hexagonal or cubic array of the pore channels. It could be prospected that such hybrid materials would present great potential applications in drug delivery and fluorescence probing for medical diagnosis and synchronous therapy.

Ag/MnO2 Nanorod as Electrode Material for High-Performance Electrochemical Supercapacitors

A one-dimensional hierarchical Ag nanoparticle (AgNP)/MnO2 nanorod (MND) nanocomposite was synthesized by combining a simple solvothermal method and a facile reduction approach in situ. Owing to its high electrical conductivity, the resulting AgNP/MND nanocomposite displayed a high specific capacitance of 314 F g-1 at a current density of 2 A g-1, which was much higher than that of pure MNDs (178 F g-1). Resistances of the electrolyte (Rs) and charge transportation (Rct) of the nanocomposite were much lower than that of pure MNDs. Moreover, the nanocomposite exhibited outstanding long-term cycling ability (9% loss of initial capacity after 1000 cycles). These results indicated that the nanocomposite could serve as a promising and useful electrode material for future energy-storage applications.

One-dimensional photocatalysts of AVO 4 (A = Bi, Fe)/carbon nanofibers frameworks: an alternative strategy in improving photocatalytic activities

This work provided an efficient alternative strategy to improve the performance of AVO4 (Au2009=u2009Bi, Fe)-based materials for organic degradations under visible light. Carbon nanofibers (CNFs) as a flexible template were obtained by an electrospinning technique, then AVO4 as the primary visible light-absorbers were succesfully grown on the surface of template frameworks for producing AVO4/CNFs heterostructures via a hydrothermal method. Photocatalytic studies revealed removal efficiencies were greatly increased when CNFs were introduced into AVO4 heterostructures, compared with pure BiVO4 and FeVO4, with 94 and 90.6% of RB photocatalytically degraded by BiVO4/CNFs and FeVO4/CNFs heterostructures within 3xa0h under visible light irradiation. The enhanced photocatalytic activity might have arisen from the high separation efficiency of photogenerated electron–hole pairs based on positive synergetic effects between AVO4 and CNFs heterojunctions. These heterostructures were easily recycled without a decrease in photocatalytic activity benefited from the nanofibers frameworks. Moreover, this paper confirmed a simple and a general method for fabricating other VO4-containing oxides heterostructures.

Facile synthesis of hollow Ni 0.2 Mn 0.8 O 1.5 twin microspheres for electrochemical energy storage

AbstractNovel hollow Ni0.2Mn0.8O1.5 twin microspheres were synthesized through a facile solvothermal reaction followed by calcination. The prepared hollow twin microspheres were composed of a large number of aggregated nanoparticles, with many pores homogeneously distributed across the whole of the twin microspheres. Benefiting from such structural advantages, such as the void core and high porosity, the prepared hollow Ni0.2Mn0.8O1.5 twin microspheres, as an electrode for supercapacitors, exhibited remarkable electrochemical performance with a large specific capacitance (491xa0Fxa0g−1 at 0.5xa0Axa0g−1), desirable rate capability (81% of capacity retention at 5xa0Axa0g−1), and excellent cycling stability (94.6% of the initial capacity after 2000 cycles). Moreover, a fabricated asymmetric supercapacitor cell based on Ni0.2Mn0.8O1.5 and active carbon demonstrated an energy density of 19.5xa0Whxa0kg−1 at a power density of 799xa0Wxa0kg−1, suggesting a promising practical application for these microspheres in supercapacitors.Graphical AbstractNovel hollow Ni0.2Mn0.8O1.5 twin microspheres have been synthesized based on the oriented attachment and Ostwald ripening effects, demonstrating high energy density and power density for the promising application in energy storage devices.n