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

Abstract

Cobalt hydroxide nanosheets/ruthenium oxide (Co(OH)2/RuO2) nanocomposite on nickel foam was successfully synthesized via a simple electrodeposition process as an advanced supercapacitor electrode material. The microscopy studies reveal that RuO2 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 RuO2 nanoparticles. The electrochemical tests indicate that the optimized Co(OH)2/RuO2 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 RuO2, the capacitance of the Co(OH)2/RuO2 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/RuO2 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/RuO2 composite is mainly in virtue of the good synergies between Co(OH)2 and RuO2 insuring large surface area, rich electrochemical reactive sites, the short diffusion pathways of ions and good electroconductivity during the charge-discharge process.