Supported ultrafine ruthenium oxides with specific capacitance up to 1099 F g−1 for a supercapacitor

•Ru nanoclusters with an average size of 1.7 nm were prepared in aqueous phase.•The Ru nanoclusters were loaded on various carbon-based substrates.•The Ru clusters were converted into ultrafine RuO2 on the carbon-based substrates.•The supported ultrafine RuO2 exhibit high specific capacitances up to 1099 F g−1.

Reducing the particle size is a straightforward way to increase the specific surface area of ruthenium oxide, which usually translates to the high specific capacitance for a supercapacitor. Herein, we report a facile strategy to fabricate ultrafine ruthenium oxides supported on various carbon-based substrates (carbon powders, carbon nanotubes, or reduced graphene oxides) as excellent electrode materials for a supercapacitor. The novelty of this work lies in its synthetic approach, which involves an aqueous synthesis of ruthenium nanoclusters under the control of pH value, and an air oxidation-based conversion process. In particular, owing to their ultrafine particle size, the as-prepared carbon-, carbon nanotube-, or reduced graphene oxide-supported ruthenium oxides exhibit specific capacitance as high as 879.1 F g−1, 966.8 F g−1 and 1099.6 F g−1, respectively, for a supercapacitor at a current density of 0.5 A g−1. The specific capacitance maintains 98.4% (for carbon supports), 98.0% (for carbon nanotube supports) and 98.4% (for reduced graphene oxide supports) at current density of 1 A g−1 with good cycling stability. The remarkable simplicity and environmental friendliness of this synthesis may provide a liable quantity production route to produce ruthenium oxides as highly efficient electrode materials for a supercapacitor.

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