Facile growth of mesoporous Co3O4 nanowire arrays on Ni foam for high performance electrochemical capacitors

Mesoporous Co3O4 nanowire (NW) arrays freely standing on Ni foam substrate are prepared via two-step strategy: precipitating hydroxides followed by calcinating process. The slim Co3O4 NWs with average diameter of about 80 nm and length up to 10 mu m 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 Co3O4 NW arrays. Electrochemical tests show that Co3O4 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.