Improved pseudocapacitive performance and cycle life of cobalt hydroxide on an electrochemically derived nano-porous Ni framework

The pseudocapacitance and morphology of an electrodeposited cobalt hydroxide (Co(OH)2) significantly depends on the architecture of the electrode substrate. The nano-porous Ni framework, derived from the selective dissolution of Cu from a Ni–Cu alloy, effectively promotes the electrochemical utilization of deposited Co(OH)2 even at a high loading amount condition. The great electronic and ionic conduction within the nano-structured electrode improves the energy storage performance of Co(OH)2 as compared to that for a conventional flat Ni substrate. In this work, the Co(OH)2 mass specific capacitance, evaluated using cyclic voltammetry (CV), only slightly decreases from 2650 to 2470 F g−1 when the potential sweep rate is substantially increased from 5 to 200 mV s−1. The developed Ni(OH)2/NiOOH (from the nano-porous framework) incorporates with the deposited Co(OH)2 upon CV cycling; the mixed hydroxide shows a noticeably synergistic capacitance. Furthermore, the dissolution of Co(OH)2 in KOH electrolyte is greatly suppressed due to the incorporation of Ni(OH)2/NiOOH, consequently prolonging the electrode cycle life.

► Supercapacitor electrodes with nano-structures are prepared electrochemically.
► Exceptional specific capacitance (2650 F g−1) of Co(OH)2 is obtained.
► Nano-structured electrodes exhibit excellent high-rate performance.
► Co–Ni mixed hydroxide shows a noticeably synergistic capacitance.
► Cycle life of Co(OH)2 in KOH electrolyte can be significantly improved.