Anchoring Hydrous RuO2 on Graphene Sheets for High-Performance Electrochemical Capacitors

Hydrous ruthenium oxide (RuO2)/graphene sheet composites (ROGSCs) with different loadings of Ru are prepared by combining sol–gel and low‐temperature annealing processes. The graphene sheets (GSs) are well‐separated by fine RuO2 particles (5–20 nm) and, simultaneously, the RuO2 particles are anchored by the richly oxygen‐containing functional groups of reduced, chemically exfoliated GSs onto their surface. Benefits from the combined advantages of GSs and RuO2 in such a unique structure are that the ROGSC‐based supercapacitors exhibit high specific capacitance (∼570 F g−1 for 38.3 wt% Ru loading), enhanced rate capability, excellent electrochemical stability (∼97.9% retention after 1000 cycles), and high energy density (20.1 Wh kg−1) at low operation rate (100 mA g−1) or high power density (10000 W kg−1) at a reasonable energy density (4.3 Wh kg−1). Interestingly, the total specific capacitance of ROGSCs is higher than the sum of specific capacitances of pure GSs and pure RuO2 in their relative ratios, which is indicative of a positive synergistic effect of GSs and RuO2 on the improvement of electrochemical performance. These findings demonstrate the importance and great potential of graphene‐based composites in the development of high‐performance energy‐storage systems. Hydrous ruthenium oxide/graphene sheet composites (ROGSCs) are prepared by combining a sol–gel method and low‐temperature annealing. ROGSC‐based electrochemical capacitors display high specific capacitance (570 F g−1 for 38.3 wt% Ru), enhanced rate capability, excellent electrochemical stability (˜97.9% after 1000 cycles), and high energy density (20.1 Wh kg−1) or power density (10000 W kg−1), due to positive synergistic effect.