Stepwise Splitting Growth and Pseudocapacitive Properties of Hierarchical Three-Dimensional Co₃O₄ Nanobooks

Three-dimensional hierarchical Co₃O₄ nanobooks have been synthesized successfully on a large scale by calcining orthorhombic Co(CO₃) (OH)·0.11H₂O precursors with identical morphologies. Based on the influence of reaction time and urea concentration on the nanostructures of the precursors, a stepwise splitting growth mechanism can be proposed to understand the formation of the 3D nanobooks. The 3D Co₃O₄ nanobooks exhibit excellent pseudocapacitive performances with specific capacitances of 590, 539, 476, 453, and 421 F/g at current densities of 0.5, 1, 2, 4, and 8 A/g, respectively. The devices can retain ca. 97.4% of the original specific capacitances after undergoing charge-discharge cycle tests 1000 times continuously at 4 A/g.