title: Sonochemical oxidation of multiwalled carbon nanotubes.
abstract: Functionalization of carbon nanotubes (CNTs) is important for enhancing deposition of metal nanoparticles in the fabrication of supported catalysts. A facile approach for oxidizing CNTs is presented using a sonochemical method to promote the density of surface functional groups. This was successfully employed in a previous study [J. Phys. Chem. B 2004, 108, 19255] to prepare highly dispersed, high-loading Pt nanoparticles on CNTs as fuel cell catalysts. X-ray photoelectron spectroscopy (XPS), transmission electron microscopy, cyclic voltammetry, and settling speeds were used to characterize the degree of surface functionalization and coverage. The sonochemical method effectively functionalized the CNTs. A mixture of -C-O-/-C=O and -COO- was observed along with evidence for weakly bound CO at longer treatment times. The integrated XPS C 1s core level peak area ratios of the oxidized-to-graphitic C oxidation states, as well as the atom % oxygen from the O 1s level, showed an increase in peak intensity (attributed to -CO(x)()) with increased sonication times from 1 to 8 h; the increase in C surface oxidation correlated well with the measured atom %. Most of the CNT surface oxidation occurred between 1 and 2 h. The sonochemically treated CNTs were also studied by cyclic voltammetry and settling experiments, and the results were consistent with the XPS observations.
authors.affiliation: Departments of Chemical & Biological Engineering and Chemistry, University of Missouri-Rolla, Rolla, MO 65409-0010, USA. xingy@umr.edu
authors.forename: Yangchuan
authors.initials: Y
authors.lastname: Xing
authors.forename: Liang
authors.initials: L
authors.lastname: Li
authors.forename: Charles C
authors.initials: CC
authors.lastname: Chusuei
authors.forename: Robert V
authors.initials: RV
authors.lastname: Hull
mesh_terms: D004563:Electrochemistry; D046529:Microscopy, Electron, Transmission; D049329:Nanostructures / Q000737:chemistry*; D036103:Nanotechnology; D037742:Nanotubes, Carbon / Q000737:chemistry*; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry; D010984:Platinum / Q000737:chemistry; D013010:Sonication; D013052:Spectrometry, X-Ray Emission; D013499:Surface Properties; D013997:Time Factors
chemical_list: D037742:Nanotubes, Carbon; D010984:Platinum; D010100:Oxygen