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Nanotubular Iridium–Cobalt Mixed Oxide Crystalline Architectures Inherited from Cobalt Oxide for Highly Efficient Oxygen Evolution Reaction Catalysis

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journal contribution
posted on 18.09.2017, 00:00 by Areum Yu, Chongmok Lee, Myung Hwa Kim, Youngmi Lee
Here, we report the unique transformation of one-dimensional tubular mixed oxide nanocomposites of iridium (Ir) and cobalt (Co) denoted as IrxCo1–xOy, where x is the relative Ir atomic content to the overall metal content. The formation of a variety of IrxCo1–xOy (0 ≤ x ≤ 1) crystalline tubular nanocomposites was readily achieved by electrospinning and subsequent calcination process. Structural characterization clearly confirmed that IrxCo1–xOy polycrystalline nanocomposites had a tubular morphology consisting of Ir/IrO2 and Co3O4, where Ir, Co, and O were homogeneously distributed throughout the entire nanostructures. The facile formation of IrxCo1–xOy nanotubes was mainly ascribed to the inclination of Co3O4 to form the nanotubes during the calcination process, which could play a critical role in providing a template of tubular structure and facilitating the formation of IrO2 by being incorporated with Ir precursors. Furthermore, the electroactivity of obtained IrxCo1–xOy nanotubes was characterized for oxygen evolution reaction (OER) with rotating disk electrode voltammetry in 1 M NaOH aqueous solution. Among diverse IrxCo1–xOy, Ir0.46Co0.54Oy nanotubes showed the best OER activity (the least-positive onset potential, greatest current density, and low Tafel slope), which was even better than that of commercial Ir/C. The Ir0.46Co0.54Oy nanotubes also exhibited a high stability in alkaline electrolyte. Expensive Ir mixed with cheap Co at an optimum ratio showed a greater OER catalytic activity than pure Ir oxide, one of the most efficient OER catalysts.