Iridium‐ruthenium‐oxide coatings for supercapacitors

Electrochemical, topographical, and morphological properties of thermally‐prepared Ir x ‐Ru 1‐x ‐oxide coatings of various compositions (0 < x ≤ 1), formed on a Ti metal substrate, were investigated for their potential application as supercapacitor (SC) electrodes employing scanning electron microscopy and electrochemical techniques of cyclic voltammetry, galvanostatic charge/discharge cycling, and electrochemical impedance spectroscopy. A current state‐of‐the‐art pure ruthenium oxide (RuO 2 ) coating showed relatively low performance compared to other bimetallic Ir x Ru 1‐x ‐oxide coatings operated under the same experimental conditions. An electrochemically‐activated Ir 0.4 Ru 0.6 ‐oxide coating yielded the highest capacitance value (85 mF cm −2 ). Prolonged electrochemical cycling of the Ir/Ru‐oxide coatings in a corrosive phosphate‐buffered saline pH = 7.4, performed within an extreme potential window of 5 V, revealed an excellent stability of the coatings. In addition, this cycling procedure enabled a significant increase in capacitance for all coating compositions. It was shown that the areal capacitance (C GA ) of these coatings is strongly dependent upon the nature of the components of which the metal oxide is composed. The addition of IrO 2 to RuO 2 improved the stability and capacitive performance of the thermally‐prepared Ir‐Ru‐oxide coatings.