利用还原氧化石墨烯负载铂与碳纳米管负载铱的低贵金属负载混合催化体系用于氧还原
Low-Noble-Metal-Loading Hybrid Catalytic System for Oxygen Reduction Utilizing Reduced-Graphene-Oxide-Supported-Platinum Aligned with Carbon-Nanotube-Supported Iridium
摘要：
由还原的氧化石墨烯负载的铂和多壁碳纳米管负载的铱（两种贵金属分别以15和< 5 μ g cm-2的水平的低负载量使用）组成的混合系统已被认为是用于在酸性介质（0.5 mol dm-3 H2SO 4）中还原氧的催化材料。用旋转环-盘电极伏安法测试了该催化剂对氧还原和过氧化氢中间体形成的电催化活性。所提出的催化系统的效率也通过在80 °C下用气体扩散电极半电池进行电流动力学测量来解决。碳纳米管的作用是通过降低溶剂蒸发过程中还原氧化石墨烯重新堆积的程度来改善电催化界面处的电荷分布，并促进催化系统中氧气和电解质的传输。诊断电化学实验揭示，在含铱的系统中，不仅产生了更高的盘电流，而且产生了小得多的环电流（与还原的氧化石墨烯负载的铂及其与裸碳纳米管的复合物相比），清楚地表明形成了较少量的不期望的过氧化氢中间体。在低负载下使用的来自向Pt添加痕量铱（负载在碳纳米管上）的增强效应可能源于Ir诱导不期望的过氧化氢中间体分解的高能力。在混合体系中，Pt活性中心的活化（由于少量Ir的存在）和稀释（通过碳纳米管）之间存在竞争，因此特别注意调整它们的组成。
英文摘要：
Hybrid systems composed of the reduced graphene oxide-supported platinum and multiwall carbon nanotubes-supported iridium (both noble metals utilized at low loadings on the level of 15 and < 5 microg cm-2, respectively) have been considered as catalytic materials for the reduction of oxygen in acid media (0.5 mol dm-3 H2SO4). The electrocatalytic activity toward reduction of oxygen and formation of hydrogen peroxide intermediate have been tested using rotating ring-disk electrode voltammetric experiments. The efficiency of the proposed catalytic systems has also been addressed by performing galvanodynamic measurements with gas diffusion electrode half-cell at 80 °C. The role of carbon nanotubes is to improve charge distribution at the electrocatalytic interface and facilitate the transport of oxygen and electrolyte in the catalytic systems by lowering the extent of reduced graphene oxide restacking during solvent evaporation. The diagnostic electrochemical experiments reveal that at iridium-containing systems not only higher disk currents, but also much smaller ring currents have been produced (compared to reduced graphene oxide-supported platinum and its composite with bare carbon nanotubes), clearly implying formation of lower amounts of the undesirable hydrogen peroxide intermediate. The enhancement effect coming from the addition of traces of iridium (supported onto carbon nanotubes) to Pt, utilized at low loading, may originate from the high ability of Ir to induce decomposition of the undesirable hydrogen peroxide intermediate. There is a competition between activation (due to the presence of small amounts of Ir) and dilution (by carbon nanotubes) of Pt active centers in hybrid systems, therefore special attention is paid to the adjustment of their composition.
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