RuO2·nH2O Nanoparticles Anchored on Carbon Nano-onions: An Efficient Electrode for Solid State Flexible Electrochemical Supercapacitor

A flexible solid state electrochemical capacitor based on hydrous RuO 2 nanoparticles, supported onto the nonporous and highly accessible ion adsorptive carbon nano-onions (CNOs), is fabricated in a novel process of modifying a conducting carbon paper to a flexible conducting substrate, separated with a poly(vinyl alcohol)/H 2 SO 4 gel electrolyte. The sol–gel technique tends to form homogeneously dispersed RuO 2 nanoparticles with the average size of ∼2.3 nm on the positive surface curvatures of multilayer fullerene (CNOs), which helps the high diffusivity of ions in both the aqueous and solid state gel electrolytes. The flexible substrate worked excellently as an electrical conductor as well as a stable mechanical support. This solid state flexible energy storage device showed a maximum energy density of 10.62 Whkg –1 and a maximum power density of 4.456 kWkg –1 for the hydrous RuO 2 /CNOs nanocomposite with 94.47% cycling stability even after 4000 cycles.