Synergetic Effect of Three-Dimensional Co₃O₄@Co(OH)₂ Hybrid Nanostructure for Electrochemical Energy Storage

Highlights: • A novel 3D porous Co₃O₄@Co(OH)₂ hybrid nanostructured electrode is synthesized. • The Co₃O₄@Co(OH)₂ exhibits a high specific capacity of 1876C g⁻¹ at 5 mA cm⁻². • The hybrid nanostructure allows the synergistic contribution of both materials. - Abstract: A novel three-dimensional (3D) Co₃O₄@Co(OH)₂ hybrid nanostructure is synthesized by using two-step hydrothermal and electrodeposition methods. The composite can be employed as an efficient electrode of a high-performance supercapacitor. Scanning electron microscopy and high-resolution transmission electron microscopy images show that Co(OH)₂ nanosheets can grow both in the space and on the tops of Co₃O₄ nanotubes. In comparison with the sole Co₃O₄ nanotubes and Co(OH)₂ nanosheets, the hybrid Co₃O₄@Co(OH)₂ electrode with a naturally formed nanostructure exhibits much improved battery-type performances in a 3 mol L⁻¹ KOH electrolyte solution, as evidenced by the high specific capacity of 1876 C g⁻¹ at a current density of 5 mA cm⁻². A good retention capability is also demonstrated, 83.1% of initial capacity value is maintained after 1000 cycles at a current density of 25 mA cm⁻². The observed high performances of Co₃O₄@Co(OH)₂ hybrid electrode with the 3D nanostructure make it attractive for the development of high-efficiency electrochemical energy storage devices.