Capacitance performance of cobalt hydroxide-based capacitors with utilization of near-neutral electrolytes

Conventional alkaline solutions used for capacitive performance of electrodeposited cobalt hydroxides have a number of disadvantages as they are corrosive, environmentally unfriendly and provide a small working potential range. In this study, the capacitive properties of electrodeposited cobalt hydroxide/oxide were investigated in 1 M Na2SO4 solution with pH 5.5 by means of cyclic voltammetry, galvanostatic charging/discharging experiments and electrochemical impedance spectroscopy. The capacitance of the cobalt hydroxide/oxide was demonstrated to have high values of 141 F g−1 at scan rate 8 mV s−1 in this 1 M Na2SO4 solution. The anodic potential range is extended by 0.8–1.3 V vs. Ag/AgCl. A good cyclic stability and reversibility were observed.