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 (Co3O4) 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 Co3O4 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.