Hongmei Ji

Preparation of Fe3O4 with high specific surface area and improved capacitance as a supercapacitor

Here, we report for the first time a facile ultrasonic synthesis of Fe3O4 nanoparticles using FeCl3 and the organic solvent ethanolamine (ETA). The intermediate of the ETA-Fe(II) complex produces Fe3O4 after hydrolysis and hydrothermal treatment. The moderate reduction of ETA and ultrasound play an important role in the synthesis of superfine Fe3O4 particles with a very high specific surface area (165.05 m(2) g(-1)). The Fe3O4 nanoparticles were characterized by X-ray diffraction (XRD), scanning and transmission electron microscopy (SEM and TEM), high-resolution transmission electron microscopy (HRTEM), and ultraviolet-visible absorption spectroscopy (UV-vis). Fe3O4 as an electrode material was fabricated into a supercapacitor and characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and galvanostatic charge-discharge measurements. The as-synthesized Fe3O4 exhibits remarkable pseudocapacitive activities including high specific capacitance (207.7 F g(-1) at 0.4 A g(-1)), good rate capability (90.4 F g(-1) at 10 A g(-1)), and excellent cycling stability (retention 100% after 2000 cycles). This novel synthetic route towards Fe3O4 is a convenient and potential way of producing a secondary energy material which is expected to be applicable in the synthesis of other metal oxide nanoparticles.

Large-scale preparation of shape controlled SnO and improved capacitance for supercapacitors: from nanoclusters to square microplates

Here, we first provide a facile ultrasonic-assisted synthesis of SnO using SnCl2 and the organic solvent of ethanolamine (ETA). The moderate alkalinity of ETA and ultrasound play very important roles in the synthesis of SnO. After the hydrolysis of the intermediate of ETA-Sn(II), the as-synthesized SnO nanoclusters undergo assembly, amalgamation, and preferential growth to microplates in hydrothermal treatment. The as-synthesized SnO was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), ultraviolet-visible absorption spectroscopy (UV-vis) and X-ray diffraction (XRD). To explore its potential applications in energy storage, SnO was fabricated into a supercapacitor electrode and characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and galvanostatic charge-discharge measurements. The as-synthesized SnO exhibits remarkable pseudocapacitive activity including high specific capacitance (208.9 F g(-1) at 0.1 A g(-1)), good rate capability (65.8 F g(-1) at 40 A g(-1)), and excellent cycling stability (retention 119.3% after 10,000 cycles) for application in supercapacitors. The capacitive behavior of SnO with various crystal morphologies was observed by fitted EIS using an equivalent circuit. The novel synthetic route for SnO is a convenient and potential way to large-scale production of microplates which is expected to be applicable in the synthesis of other metal oxide nanoparticles.

Rapid microwave-hydrothermal preparation of few-layer MoS 2 /C nanocomposite as anode for highly reversible lithium storage properties

Abstract3D nanohybrid structures with few-layered MoS2 nanosheets uniformly incorporated in the carbon substrate are prepared via using the rapid and homogeneous microwave-hydrothermal method, in which the size of the basic unit structure of MoS2/C was small. The samples were systematically investigated by X-ray diffraction, field emission scanning electron microscopy, X-Ray photoelectron spectroscopy and high-resolution transmission electron microscopy for structure and composition test. The electrochemical performances of the composites are evaluated by cyclic voltammogram, galvanostatic charge–discharge and electrochemical impedance spectroscopy. Electrochemical measurements reveal that the maximum-specific capacitance of the MoS2/C electrodes reaches up to 1003xa0mAhxa0g–1 at a discharge current density 100xa0mAxa0g–1. The MoS2/C hybrid composite remains 755 mAhxa0g–1 after 50 cycles at the current of 200xa0mAxa0g–1, much higher than that of the pure MoS2. The superior electrochemical performances of MoS2/C composites as Li-ion battery anodes are attributed to their enhanced available active sites for charges, decreased transmission resistance between interlayers, improved electronic conductivity as well as good mechanical stability.