Smaller is Faster and More Sensitive: The Effect of Wire Size on the Detection of Hydrogen by Single Palladium Nanowires

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• 作者：Fan Yang ; Sheng-Chin Kung ; Ming Cheng ; John C. Hemminger ; Reginald M. Penner
• 刊名：ACS Nano
• 出版年：2010
• 出版时间：September 28, 2010
• 年：2010
• 卷：4
• 期：9
• 页码：5233-5244
• 全文大小：800K
• 年卷期：0
• ISSN：1936-086X

文摘

Palladium nanowires prepared using the lithographically patterned nanowire electrodeposition (LPNE) method are used to detect hydrogen gas (H₂). These palladium nanowires are prepared by electrodepositing palladium from EDTA-containing solutions under conditions favoring the formation of β-phase PdH_x. The Pd nanowires produced by this procedure are characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, atomic force microscopy, and X-ray photoelectron spectroscopy. These nanowires have a mean grain diameter of 15 nm and are composed of pure Pd with no XPS-detectable bulk carbon. The four-point resistance of 50−100 μm segments of individual nanowires is used to detect H₂ in N₂ and air at concentrations ranging from 2 ppm to 10%. For low [H₂] < 1%, the response amplitude increases by a factor of 2−3 with a reduction in the lateral dimensions of the nanowire. Smaller nanowires show accelerated response and recovery rates at all H₂ concentrations from, 5 ppm to 10%. For 12 devices, response and recovery times are correlated with the surface area/volume ratio of the palladium detection element. We conclude that the kinetics of hydrogen adsorption limits the observed response rate seen for the nanowire, and that hydrogen desorption from the nanowire limits the observed recovery rate; proton diffusion within PdH_x does not limit the rates of either of these processes.