Facile growth of mesoporous Co 3O 4 nanowire arrays on Ni foam for high performance electrochemical capacitors

Abstract

Mesoporous Co 3O 4 nanowire (NW) arrays freely standing on Ni foam substrate are prepared via two-step strategy: precipitating hydroxides followed by calcinating process. The slim Co 3O 4 NWs with average diameter of about 80 nm and length up to 10 μm are observed by transmission electron microscopy and scanning electron microscopy. Cyclic voltammetry, chronopotentiometry, and electrochemical impedance measurements are applied to investigate the performance of the Co 3O 4 NW arrays. Electrochemical tests show that Co 3O 4 NW arrays deliver a specific capacitance (SC) of 1160 F g −1 at 2 A g −1, and even 820 F g −1 at 20 A g −1. Also, the SC degradation is only 9.6% after 5000 continuous charge–discharge cycles at 8 A g −1, indicating their excellent electrochemical stability. The improved performance is reasonably ascribed to their unique 3D hierarchical structure.