Facile synthesis of ultra-small ruthenium oxide nanoparticles anchored on reduced graphene oxide nanosheets for high-performance supercapacitors

Herein, we report a facile, low cost, and environmentally friendly approach to prepare reduced graphene oxide-ruthenium oxide hybrid (RGO-RuO2) materials for supercapacitor electrode applications by in situ sol-gel deposition of RuO2 nanoparticles on the surface of graphene oxide (GO), followed by a reduction of GO in a strong alkaline medium at a low temperature. The combination of the sol-gel route and the reduction of graphene oxide at low temperatures resulted in ultrafine, hydrated amorphous RuO2 particles with sizes of only 1.0-2.0 nm, which uniformly decorated the surfaces of RGO sheets. The obtained RGO-RuO2 supercapacitor exhibited excellent electrochemical capacitive performance in a 1 M H2SO4 electrolyte with a specific capacitance more than 500 F g(-1) at a current density of 1.0 A g(-1) and high rate performance with the capacitance retention of 86% when the current density was increased 20 times, from 1.0 to 20.0 A g(-1) in a two-electrode test cell configuration. The RGO-RuO2 system also showed good cycling stability with a capacitance retention of 87% after 2000 cycles. The excellent capacitive properties of RGO-RuO2 could be attributed to the uniform anchoring of ultra-small, hydrated amorphous RuO2 nanoparticles on the surface of RGO sheets, resulting in synergistic effects between them. The developed approach represents an exciting direction for enhancing the device performance of the graphene-metal oxide composite supercapacitors and can be used for designing the next generation of energy storage devices.