Wire-like Co3O4 nanostructures were prepared by the combination of magnetic field-assisted hydrothermal reduction of cobalt ions and the subsequent ambient annealing at 500 degrees C. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to characterize the structure and morphological evolution of the products. The results show that the wire-like nanostructures possess diameters about 250 nm and lengths over 10 mu m. The possible formation mechanism of the wire-like Co3O4 nanostructures is also proposed based on the SEM results. Galvanostatic methods were used to characterize the electrochemical properties. The measurements indicate that the wire-like Co3O4 nanostructures show larger discharge and charge capacities than that of spherical Co3O4 nanoparticles prepared in the absence of magnetic field. In addition, the photocatalytic activity of the products was investigated by measuring the photodegradation of methyl orange solution under ultraviolet radiation, which shows that both the wire-like and spherical products have a good photocatalytic activity. Crown Copyright (C) 2012 Published by Elsevier Ltd. All rights reserved.