Co(OH)2 nanoflakes grown on 3D graphene foam as a binder-free hybrid electrode for high-performance supercapacitors

Using a simple hydrothermal method, porous Co(OH)2 nanoflakes were successfully deposited on 3D graphene foam grown by chemical vapor deposition. And the Co(OH)2/3D graphene hybrids were then employed as the binder-free electrode for supercapacitors. Structure and morphology of the hybrid materials were investigated and effect of hydrothermal temperature on electrochemical performance was optimized. The 90 °C-synthesized sample exhibits the highest specific capacitance of 1636 F/g at 0.5 A/g in the KOH electrolyte. Even as the current density increases 120 times to 60 A/g, the specific capacitance of 1180 F/g is still maintained, representing the excellent rate capability. The hybrid electrode also shows good cycling stability with capacity retention of 75% after 1000 cycles. The excellent electrochemical performance of the hybrid electrode is attributed to synergistic effect of the highly conductive graphene and the nano-porous Co(OH)2.