Terephthalate-based cobalt hydroxide: a new electrode material for supercapacitors with ultrahigh capacitance

Searching for new electrode materials is one of the key tasks in developing high-performance supercapacitors. In this work, as a layered hydroxyl derivative, terephthalate-based cobalt hydroxide, Co-2(OH)(2)(C8H4O4), is successfully prepared in situ on nickel foam through a simple hydrothermal route. The scanning electron microscopy results reveal that the products are composed of massive double-blade lath crystals grown along the a-axis. The as-obtained Ni-foam-supported Co-2(OH)(2)(C8H4O4) is directly used as the positive electrode of supercapacitors without further treatment. The resulting Co-2(OH)(2)(C8H4O4) electrode exhibits ultrahigh charge storage capacity with the specific capacity of 9.36 C cm(-2) (1261 C g(-1)) at a current density of 10 mA cm(-2) (0.5 A g(-1)) and good cycling stability with the capacity retention of 82.4% over 5000 cycles at a current density of 50 mA cm(-2). In combination with activated carbon as the negative electrode in 3 M KOH aqueous electrolyte, the constructed asymmetric supercapacitor delivers a high energy density of 30.62 W h kg(-1) at a power density of 221 W kg(-1) within a voltage window of 1.5 V. These encouraging electrochemical performances enable the developed terephthalate-based cobalt hydroxide to be a promising electrode material for supercapacitor applications.