Nickel-foam-supported ruthenium oxide/graphene sandwich composite constructed via one-step electrodeposition route for high-performance aqueous supercapacitors

Abstract A high-performance supercapacitor both considered high power and high energy density is needed for its applications such as portable electronics and electric vehicles. Herein, we construct a high-performance ruthenium oxide/graphene (RuO 2 -ERG) composite directly grown on Ni foam through cyclic voltammetric deposition process. The RuO 2 -ERG composite with sandwich structure is achieved effectively from a mixed solution of graphene oxide and ruthenium trichloride in the −1.4 V to 1.0 V potential range at a scan rate of 5 mV s −1 . The electrochemical performance is optimized by tuning the concentration of the ruthenium trichloride. This integrative RuO 2 -ERG composite electrode can effectively maintains the accessible surface for redox reaction and stable channels for electrolyte penetration, leading to an improved electrochemical performance. Symmetrical aqueous supercapacitors based on RuO 2 -ERG electrodes exhibit a wider operational voltage window of 1.5 V. The optimized RuO 2 -ERG electrode displays a superior specific capacitance with 89% capacitance retention upon increasing the current density by 50 times. A high energy density of 43.8 W h kg −1 at a power density of 0.75 kW kg −1 is also obtained, and as high as 39.1 W h kg −1 can be retained at a power density of 37.5 kW kg −1 . In addition, the capacitance retention is still maintained at 92.8% even after 10,000 cycles. The excellent electrochemical performance, long-term cycle stability, and the ease of preparation demonstrate that this typical RuO 2 -ERG electrode has great potentialities to develop high-performance supercapacitors.