Hydrous RuO2 nanoparticles coated on Co(OH)2 nanoflakes as advanced electrode material of supercapacitors

Cobalt hydroxide nanosheets/ruthenium oxide (Co(OH) 2 /RuO 2 ) nanocomposite on nickel foam was successfully synthesized via a simple electrodeposition process as an advanced supercapacitor electrode material. The microscopy studies reveal that RuO 2 nanoparticles are loaded uniformly on interconnected Co(OH) 2 nanosheets forming a three-dimensional (3D) network. The performance optimization of composite is come true through adjusting deposition time of RuO 2 nanoparticles. The electrochemical tests indicate that the optimized Co(OH) 2 /RuO 2 nanocomposite displays excellent super-capacitive properties. The specific capacitance is up to 2168 F g −1 as the current density is 1 A g −1 . Compared with the pure Co(OH) 2 and RuO 2 , the capacitance of the Co(OH) 2 /RuO 2 composite increases by 57% and 80%, respectively. The capacitance maintains at 86.0% after 5000 charging and discharging loops at the constant current density of 5 A g −1 , while the pure Co(OH) 2 only maintains 71.7% of the original capacitance after 5000 loops. The asymmetric capacitor assembled using Co(OH) 2 /RuO 2 nanocomposite as positive electrode and activated carbon (AC) as negative electrode exhibits a high energy density of 58.4 W h kg −1 at a power density of 1.2 kW kg −1 . The good pseudocapacitance behavior of the Co(OH) 2 /RuO 2 composite is mainly in virtue of the good synergies between Co(OH) 2 and RuO 2 insuring large surface area, rich electrochemical reactive sites, the short diffusion pathways of ions and good electroconductivity during the charge-discharge process.