The Effects of Pt Doping on the Structure and Visible Light Photoactivity of Titania Nanotubes

Abstract

Platinum-doped titania nanotubes were prepared by a hydrothermal technique to produce visible light activated catalysts. Pt loading, however, also affected the morphology of the titania nanotubes. Scanning electron microscopy and scanning transmission electron microscopy (STEM) results reveal that up to 1 mol % loading Pt-doped titania retains its nanotubular structure, but at 2 and 4 mol % Pt the nanotubes collapse to a nanopowder. High-angle annular dark field STEM images show that the Pt nanoparticles have diameters of ∼2−5 nm and are uniformly distributed on the nanotube surface. Pt doping enhances the photoactivity of titania nanotubes in visible light for the photooxidation of acetaldehyde. Titania nanotubes doped with 0.5 mol % Pt show the maximum visible light photoactivity with a decay rate constant nearly 7 order of magnitude (0.0034 min−1) greater than commercially available P25 titania (0.0005 min−1). Electron paramagnetic resonance (EPR) spectroscopy was used to probe the mechanism by which Pt-doping alters the structure and function of the titania nanotubes. EPR spectra revealed that undercoordinated sites and oxygen deficiency on the surface of the titania nanotube are created in synthesis (calcination in hydrogen atmosphere). These surface features interact with the Pt centers to alter the optical, electronic, and chemical behavior of the titania nanotube. These results also suggest the potential for practical applications such as incorporating Pt-doped titania nanotubes with commercially available light sources for indoor air purification.

Optical properties and photocatalytic activities of tungsten oxide (WO3) with platinum co-catalyst addition

“…The energy gap decline from 2.840 eV for pure WO 3 film to 2.507 eV for WO 3 /Pt film with the weight percentage of Pt is 4%. Vijayan et al, [8] reported the same result that additional of Pt in the TiO2 nanotube change the optical band gap value. These two findings explain that the addition of Platinum will provide the new energy state slightly below the WO3 conduction band.…”

One-Dimensional Titanium Dioxide Nanomaterials: Nanotubes

“…Hydrothermally grown TiO 2 nanotubes can be doped with various elements including chromium, manganese, cobalt, niobium, vanadium, bismuth, boron, phosphor, gadolinium, platinum, iron, and neodymium 457,458,[460][461][462][464][465][466] . Different co-doped 459,463 and tri-doped 467 TiO 2 nanotubes were also reported.…”

“…462,464,465 Liu et al 463 co-doped TiO 2 nanotubes with gadolinium and nitrogen, with 1.5 at.% and 2.3…”

Light-Induced Processes in Plasmonic Gold/TiO2 Photocatalysts Studied by Electron Paramagnetic Resonance

“…Furthermore, although a recent review on TiO 2 modified with noble metals recognizes the importance of EPR as a unique tool to understand the superior photocatalytic activity of these materials [9], only few EPR studies have been reported on the topic [18][19][20][21][22][23].…”