Friday, May 19, 2006

Chemistry of Materials:Pt Nanoparticle Binding on Functionalized Multiwalled Carbon Nanotubes

Comment: Application of 195Pt NMR?? Looks like an interesting system to characterize.

Chem. Mater., 18 (7), 1780 -1788, 2006. 10.1021/cm0518978 S0897-4756(05)01897-1 Web

Pt Nanoparticle Binding on Functionalized Multiwalled Carbon Nanotubes
Robert V. Hull,
Liang Li, Yangchuan Xing, and Charles C. Chusuei*
Departments of Chemistry and Chemical and Biological Engineering, University of Missouri-Rolla, Rolla, Missouri 65409-0010

To create new catalyst materials for fuel cell applications, multiwalled carbon nanotubes (CNTs) were functionalized with -C=O, -C-O-C-, -COO-, and -C-OH groups using a sonochemical treatment method under acidic aqueous solution (HNO3/H2SO4) conditions to make them amenable to deposition of highly dispersed, ~4 nm diameter Pt nanoparticles. The Pt-CNT interface was probed with X-ray photoelectron spectroscopy (XPS), extended X-ray absorption fine structure spectroscopy (EXAFS), and Raman and attenuated total reflection infrared (ATR-IR) spectroscopies to elucidate the nature of the Pt cluster-CNT surface binding. The degree of disorder of the sp3-hybridized C from the CNTs, as measured by the Raman D-to-G integrated peak area ratios, increased with the degree of surface oxidation of the CNTs. EXAFS of the Pt LIII edge showed Pt coordination with oxygen (in the form of PtOx) at the outermost perimeter of the Pt clusters while the majority of the bulk, as shown by the XPS Pt 4f core level, was in the metallic form. Infrared measurements showed that the carbonyl C=O stretching at 1700 cm-1 red shifted to ~1550 cm-1 following Pt cluster deposition. In addition, changes in the C-O structural features at ~1030 and 1150 cm-1 were observed, indicative of Pt cluster binding with the ionic form of carboxylate, COO(Pt), or ester-like, C(=O)CO(Pt), O atoms.

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