Department of Chemistry and Nano Science, Global Top 5 Program, Ewha Womans University, Seoul 120-750, Korea.
Phys Chem Chem Phys. 2013 Oct 7;15(37):15365-70. doi: 10.1039/c3cp51780b.
Nanocomposites of iridium nanoparticles (Ir NPs), supported on graphene nanosheets, are synthesized and their electrocatalytic acitivities in the oxygen reduction reaction (ORR) are studied depending on their Ir oxidation state. Graphene functionalized with poly(vinyl pyrrolidone) (pRGO) is a suitable support for Ir NPs, producing well-monodispersed Ir NPs anchored strongly on the pRGO surface (Ir NP/pRGO) with a very high density. This was confirmed by scanning electron microscopy and transmission electron microscopy. The ORR activity of the Ir NP/pRGO nanocomposites in 0.5 M H2SO4 solution was observed to be dependent on the oxidation state of the immobilized Ir NPs. In fact, the nanocomposite composed of Ir(0) metal NPs, rather than Ir oxide (IrOx) NPs, exhibits higher ORR activity, such as more positive onset potential, higher and flatter limiting current density, a greater n value, and a sharper curve shape in the rotating disk electrode voltammetry experiments. Higher ORR activity of Ir is ascribed to the stronger adsorption of oxygen on the surface of Ir compared to IrOx. The practical stability of the Ir NP/pRGO composite was also confirmed under O2 saturated/acidic conditions.
将氧化铱纳米粒子（Ir NPs）负载在石墨烯纳米片上的纳米复合材料被合成，并研究了其在氧还原反应（ORR）中的电催化活性，这取决于其 Ir 氧化态。用聚（N-乙烯基吡咯烷酮）（pRGO）功能化的石墨烯是 Ir NPs 的合适载体，可生成在 pRGO 表面上牢固固定的、具有非常高密度的单分散 Ir NPs（Ir NP/pRGO）。这一点通过扫描电子显微镜和透射电子显微镜得到了证实。在 0.5 M H2SO4溶液中，Ir NP/pRGO 纳米复合材料的 ORR 活性被观察到依赖于固定化 Ir NPs 的氧化态。实际上，由 Ir(0)金属 NPs 组成的纳米复合材料，而不是 IrOx NPs，表现出更高的 ORR 活性，例如具有更正的起始电位、更高和平坦的极限电流密度、更大的 n 值以及在旋转圆盘电极伏安法实验中更陡峭的曲线形状。Ir 的更高的 ORR 活性归因于氧在 Ir 表面上的吸附比在 IrOx 上更强。在 O2 饱和/酸性条件下，Ir NP/pRGO 复合材料的实际稳定性也得到了证实。
