A simple in situ self-assembly selective synthetic strategy for onestep controllable formation of various three-dimensional (3D) hierarchical Co3O4 micro/nanomaterials with peculiar morphologies, uniform size, and high quality is successfully developed. The Morphological control and related impact factors are investigated and clarified in detail. The results further clarify the corresponding mechanisms on the reaction process, product generation, and calcining process as well as the formation of specific morphologies. Furthermore, the superior catalytic properties of these materials are confirmed by two typical Co-based energy applications on the decomposition of an important solid rocket propellant, ammonium perchlorate (AP), and dye-sensitized solar cells (DSSCs). The addition of Co3O4 materials to AP obviously decreases the decomposition temperatures by about 118-140 degrees C and increases the exothermic heat to a great extent. As the substituted counter electrodes of DSSCs, the 3D hierarchical Co3O4 materials exhibit attractive photovoltaic performances. These findings provide a facile and: effective way for designing new types of 3D hierarchical materials toward high catalytic activity for energy devices.