Synthesis, Electron Microscopy and Photocatalytic Activity Studies of Hierarchical TiO 2 Based Nanofiber Catalysts for P
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Synthesis, Electron Microscopy and Photocatalytic Activity Studies of Hierarchical TiO2 Based Nanofiber Catalysts for Photocatalysis and Hydrogen-Generation Applications Srujan Mishra1 and Scott. P. Ahrenkiel1 1
Department of Nanoscience and Nanoengineering, South Dakota School of Mines and Technology, Rapid City, SD 57701, U.S.A. ABSTRACT A newly developed, focused-jet, vertical style electrospinning process was employed to synthesize nanofibers of TiO2 doped with 2% and 2.5% w/v Ag nanoparticles. The as-spun nanofibers were calcined at 510 oC for 24 h in a tube furnace, with a ramp-rate of 5 oC/min, to yield polycrystalline nanofibers. Structural characterization of the prepared nanofibers was done using HR-TEM operated at 200 kV. High-resolution lattice-fringe measurements showed the presence of a mixed-phase anatase and rutile TiO2 nanostructure along with elemental Ag nanoparticles. BET analysis showed an average specific surface-area of 18.31 m2/g for the catalyst nanofibers. To measure the photocatalytic activity, a model compound, rhodamine-B dye, was used. Experimental results showed decay rates of 10.64 x 10-3 min-1 and 12.32 x 10-3 min-1 for the decay of rhodamine-B dye by TiO2/2% Ag and TiO2/2.5% Ag nanoparticles respectively. INTRODUCTION Fiber membranes have been shown to be very useful for heterogeneous catalysis and also as supports for catalytic metal nanoparticles and nanowires. In this research, a few techniques have been presented to functionalize TiO2 nanofibers with Ag nanostructures with an aim to increase the specific surface area and effective photoactive sites for more efficient photocatalysis. There has been some recent research showing the embedding of noble-metal nanoparticles in TiO2 nanostructure matrix to enhance the photocatalytic activity [1-3]. The functionalization of TiO2 nanofibers with Ag nanostructures enhances the trapping of photoexcited electrons allowing for more electrons available to participate in redox reactions by minimizing electron-hole recombination. Titania has two common crystalline forms- rutile and anatase. Anatase titania, with an octahedral crystalline structure and a band gap of 3.2 eV, exhibits high activities for use in solar cell and photocatalysis [3]. Anatase titania can be excited under UV light, and rutile under visible light. The production of mixed-phase anatase and rutile nanocrystalline fibers is beneficial. Incorporation of noble metal nanoparticles is a recent method to enhance the photocatalytic behavior of titania. Nanostructured noble metals are believed to be excellent heterogeneous catalysts. The incorporation of Ag nanoparticles can increase the catalytic activity of TiO2 nanocomposite fiber membranes, and the mechanism has been well explained in many research articles. Our earlier research has shown successful incorporation of noble metal nanoparticles like Au and Ag in TiO2 nanofiber structures [3-4].
EXPERIMENTAL DETAILS Poly(vinyl pyrrolidone) (PVP, Mw = 1,300,000), titanium (IV) isopropoxide (TiIP), acetic acid and absolute ethanol
