Galvanic displacement assembly of ultrathin CoO nanosheet arrays on nickel foam for a high-performance supercapacitor.

High-performance supercapacitors are very desirable for many portable electronic devices, electric vehicles and high-power electronic devices. Herein, a facile and binder-free synthesis method, galvanic displacement of the precursor followed by heat treatment, is used to fabricate ultrathin CoO nanosheet arrays on nickel foam substrate. When used as a supercapacitor electrode the prepared CoO on nickel foam exhibits a maximum specific capacitance of 1095 F g at a current density of 1 A g and good cycling stability of 71% retention after 2000 cycling tests. This excellent electrochemical performance can be ascribed to the high specific surface area of each CoO nanosheet that comprises numerous nanoparticles.