Growth of Highly Single Crystalline IrO<sub>2</sub> Nanowires and Their Electrochemical Applications

Abstract

We present the facile growth of highly single crystalline iridium dioxide (IrO<sub>2</sub>) nanowires on SiO<sub>2</sub>/Si and Au substrates via a simple vapor phase transport process under atmospheric pressure without any catalyst. Particularly, high-density needle-like IrO<sub>2</sub> nanowires were readily obtained on a single Au microwire, suggesting that the melted surface layer of Au might effectively enhance the nucleation of gaseous IrO<sub>3</sub> precursors at the growth temperature. In addition, all the electrochemical observations of the directly grown IrO<sub>2</sub> nanowires on a single Au microwire support favorable electron-transfer kinetics of [Fe­(CN<sub>6</sub>)]<sup>4–/3–</sup> as well as Ru­(NH<sub>3</sub>)<sub>6</sub><sup>3+/2+</sup> at the highly oriented crystalline IrO<sub>2</sub> nanowire surface. Furthermore, stable pH response is shown, revealing potential for use as a miniaturized pH sensor, confirmed by the calibration curve exhibiting super-Nernstian behavior with a slope of 71.6 mV pH<sup>–1</sup>

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