Coaxial RuO₂–ITO Nanopillars for Transparent Supercapacitor Application

Supercapacitive properties of ruthenium oxide (RuO₂) nanoparticles electrodeposited onto the indium tin oxide (ITO) nanopillars were investigated. Compared to conventional planar current collectors, this coaxially nanostructured current collector–electrode system can provide increased contact for efficient charge transport, and the internanopillar spacing allows easy access of electrolyte ions. The morphological and electrochemical properties depended on the thickness of the RuO₂ layers, i.e., the number of electrodeposition cycles. A maximum specific capacitance, C_sp, of 1235 F/g at a scan rate of 50 mV/s was achieved for the 30-cycle deposited RuO₂–ITO nanopillars. The other capacitive properties such as electrochemical reversibility and C_sp retention at high scan rates also improved greatly.