One-dimensional arrays of Co 3 O 4 nanoparticles were obtained via the thermal treatment of cobalt oxalate nanorods, which were synthesized through a convenient solvothermal route. The optical properties of Co 3 O 4 nanoparticles were investigated. The optical absorption spectrum indicates that the direct band gaps of Co 3 O 4 nanoparticles are 1.52 and 2.01 eV. The galvanostatic experiment shows the excellent electrochemical performance between 3.0 and 0.2 V.

b-FeOOH nanorods with a tunnel-type structure were synthesized via a hydrothermal method at low temperature and characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), thermal gravimetric analysis (TGA) and galvanostatic tests. From TEM bright-field images, a rodlike morphology with an average diameter of 30 ¡ 5 nm and an average length of 400 nm (aspect ratio # 13) is observed. Electrochemical tests show that thesew nanorods deliver a large discharge capacity of 275 mA h g 21 vs. Li metal at 0.1 mA cm 22 (voltage window 1.5-4.2 V). a-Fe 2 O 3 nanorods with a regular pore structure were obtained by calcining the as-synthesized FeOOH at 520 uC.

Nickel oxide nanoparticles with an average diameter of about 9 nm were synthesized via thermal decomposition of NiC2O4 precursor at 450 °C. The nanoparticles were investigated using XRD, TEM, TGA, and UV–vis spectrophotometry. The optical absorption spectrum indicates that the NiO nanoparticles have a direct band gap of 3.56 eV. The electrochemical tests show that the ultrafine NiO nanoparticles, as a promising electrode material, can deliver a large reversible discharge capacity of about 610 mA h g−1.

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