Metal ions incorporated titania nanotubes for hydrocarbon oxidation
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Metal ions incorporated titania nanotubes for hydrocarbon oxidation Huifang Xu1, Ganesh Vanamu2, Ziming Nie1, Jonathan Phillips3, and Yifeng Wang4 1 Department of Geology and Geophysics, University of Wisconsin, 1215 West Dayton Street, Madison, WI 53706 2 Department of Chemical and Nuclear Engineering, University of New Mexico, Albuquerque, NM 87131 3 Los Alamos National Laboratory, Engineering Science and Applications Division, MS C390, Los Alamos, NM 87545 4 Sandia National Laboratories, P.O. Box 5800, Albuquerque, NM 87185 ABSTRACT Present work shows that simple, standard methods of metal addition, without the need for ion implantation or other complex and expensive processes, can dramatically improve the performance of titania based structures compared to P25 for (i.e. hydrocarbon oxidation) photocatalytic reactions. In this work, Au and Pt were incorporated into titania nanotubes, and their photocatalytic activities were investigated in detail. The samples were analyzed using a JEOL FEG-2010F field emission gun scanning transmission electron microscopy (STEM) with attached Oxford Instruments’ X-ray energy-dispersive spectroscopy (EDS) system and Gatan imaging filtering (GIF) system. Both high-resolution TEM (HRTEM) images and high angle annular dark-field (HAAD) images were recorded for the specimens. The performance of the samples was tested for the oxidation of acetaldehyde using a continuous flow reactor. The pure nanotube is more photoreactive than commercial P25 titania. Both Au and Pt treated nanotube samples increased the photo reactivity. The most significant result of this work is that the activity of Pt (< 1 nm) containing nanotube is more than 10 times the rate of P25, and more than 6 times the rate of the pure nanotube. However, sizes of the Au and Pt nanoparticles on the nanotube surfaces likely affected the photo-reactivity. Large size of the Au and Pt particles decreased the photo-reactivity. Specifically, the addition of platinum without formation of obvious nanoparticles on the nanotube surfaces increased the maximum activity significantly, and increased the total yield. INTRODUCTION The main aim of this work is to prepare unique and highly active photocatalysts. Research in photocatalysis continues to grow [1-3], reflecting the demonstrated success of these catalysts for decontamination and purification of water and air polluted by volatile organic compounds [4]. In particular, illuminated semiconductors have been used to oxidize compounds typically found in low concentrations in industrial effluent streams including alkanes, alkenes, phenols, aromatic acids and surfactants [5]. Among photocatalytic materials, titanium dioxide is believed to be the most promising, due to its great capacity for oxidation, wide band gap, nontoxicity, low cost, widespread availability, and long term stability [6]. For the present work we tested the photocatalytic efficacy of a new form of titania, metal-doped nanotube titania, for the oxidation of acetaldehyde [7-8] and demonstrated that these nov
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