Shape-controlled synthesis of porous Co₃O₄ nanostructures for application in supercapacitors

In this work, we report a facile approach for the shape-controlled synthesis of cobalt carbonate/hydroxide intermediates. Three different structures, viz., one-dimensional (1D) needle-like nanorods, two-dimensional (2D) leaf-like nanosheets, and three-dimensional (3D) oval-shaped microparticles, have been synthesized through varying experimental parameters such as precursor (cobalt acetate) concentrations and volume ratio of polyethylene glycol to water. Phase-pure tricobalt tetroxide (Co ₃O₄) has been obtained by annealing these as-prepared intermediates without significant alterations in morphology. With relatively high specific surface areas of 86.1-121.5 m² g^-1, these products with distinct nanostructures were tested for their potential application in supercapacitors. The results show that these porous Co ₃O₄ structures exhibit promising capacitive properties with high capacitance and good retention. The needle-like nanorods show the highest capacitance of 111 F g^-1, and 88.2% of which can still be maintained after 1000 charge-discharge cycles. © 2010 The Royal Society of Chemistry.