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分段的铂/钌、铂/镍和铂/钌镍纳米棒作为甲醇氧化的双功能催化剂模型。

Segmented Pt/Ru, Pt/Ni, and Pt/RuNi nanorods as model bifunctional catalysts for methanol oxidation.

作者信息

Liu Fang, Lee Jim Yang, Zhou Wei Jiang

机构信息

Chemical & Biomolecular Engineering, National University of Singapore, 10 Kent Ridge Crescent, Singapore 119260, Singapore.

出版信息

Small. 2006 Jan;2(1):121-8. doi: 10.1002/smll.200500253.

Abstract

Five-segment (Pt-Ru-Pt-Ru-Pt, Pt-Ni-Pt-Ni-Pt, and Pt-RuNi-Pt-RuNi-Pt) nanorods with the same overall rod length and the same total Pt segment length were prepared by sequential electrodeposition of the metals into the pores of commercially available anodic aluminum oxide (AAO) membranes. Field-emission scanning electron microscopy (FESEM) showed that the nanorods were about 210 nm in diameter and about 1.5 microm in length. The alternating Pt and oxophilic metal(s) segments could be easily differentiated in backscattered-electron images. X-ray diffraction (XRD) analysis of the nanorods indicated that Pt and Ni were polycrystalline with fcc structures, Ru was hcp, and the co-deposited RuNi adopted the nickel fcc structure with some negative shifts in the Bragg angles. The chemical states of Pt, Ru, and Ni on the nanorod surface were assayed by X-ray photoelectron spectroscopy (XPS), and the presence of Pt(0), Pt(II), Pt(IV), Ru(0), Ru(VI), Ni(0), and Ni(II) was observed. The nanorods were catalytically active for the room-temperature electrooxidation of methanol in acidic solutions. The relative rates of reaction showed the Pt-RuNi pair sites as having the lowest overpotential to dissociate water, the highest catalytic activity in methanol oxidation, and the strongest CO-tolerance in the potential window employed. The use of segmented nanorods with identifiable Pt-oxophilic metal(s) interfaces removes many of the ambiguities in the interpretation of experimental data from conventional alloy catalysts, thereby enabling a direct comparison of the activities of various types of pair sites in methanol oxidation.

摘要

通过将金属依次电沉积到市售阳极氧化铝(AAO)膜的孔中,制备了具有相同总棒长度和相同总铂段长度的五段式(Pt-Ru-Pt-Ru-Pt、Pt-Ni-Pt-Ni-Pt和Pt-RuNi-Pt-RuNi-Pt)纳米棒。场发射扫描电子显微镜(FESEM)显示,纳米棒的直径约为210nm,长度约为1.5μm。在背散射电子图像中,可以很容易地区分交替的铂和亲氧金属段。纳米棒的X射线衍射(XRD)分析表明,铂和镍为具有面心立方结构的多晶体,钌为六方密堆积结构,共沉积的RuNi采用镍的面心立方结构,布拉格角有一些负向位移。通过X射线光电子能谱(XPS)测定了纳米棒表面铂、钌和镍的化学状态,观察到存在Pt(0)、Pt(II)、Pt(IV)、Ru(0)、Ru(VI)、Ni(0)和Ni(II)。这些纳米棒对酸性溶液中甲醇的室温电氧化具有催化活性。相对反应速率表明,Pt-RuNi双位点在解离水方面具有最低的过电位,在甲醇氧化中具有最高的催化活性,并且在所采用的电位窗口中具有最强的抗CO能力。使用具有可识别的铂-亲氧金属界面的分段纳米棒消除了传统合金催化剂实验数据解释中的许多模糊性,从而能够直接比较甲醇氧化中各种类型双位点的活性。

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