IrOx nanofoils (IrOxNF) of high surface area are sputtered on multi-wall carbon nanotubes (CNT) in the preparation ofa structured electrode on a stainless steel (SUS) substrate for supercapacitor applications. ThisIrOx/CNT/SUS electrode is featuredwith intriguing IrOx curved foils of 2–3 nm in thickness and 400–500 nm in height, grownon top of the vertically aligned CNT film with a tube diameter of ∼ 40 nm. These nanofoils are moderately oxidized during reactive sputtering andappeared translucent under the electron microscope. Detailed structural analysisshows that they are comprised of contiguous grains of iridium metal, iridiumdioxide, and glassy iridium oxide. Considerable Raman line broadening isalso evidenced for the attributed nanosized iridium oxides. Two capacitiveproperties of the electrode are significantly enhanced with addition of the curvedIrOx foils.First, IrOxNF reduces the electrode Ohmic resistance, which was measured at 3.5 Ω cm2 for the CNT/SUSand 2.5 Ω cm2 forIrOxNF/CNT/SUS using impedancespectroscopy. Second, IrOxNF raises the electrode capacitance from 17.7 F g − 1 (CNT/SUS)to 317 F g − 1 (IrOx/CNT/SUS), measured with cyclic voltammetry. This notable increase is furtherconfirmed by the galvanostatic charge/discharge experiment, measuring 370 F g − 1 after 2000 uninterruptedcycles between − 1.0 and 0.0 V (versus Ag/AgCl).