Loading effects of silver oxides upon generation of reactive oxygen species in semiconductor photocatalysis.
Superoxide anion radical (O(2)(-*)) and OH radical generations in suspensions of Ag metal-, Ag(2)O-, or AgO-loaded TiO(2) and BiVO(4) photocatalysts in alkaline conditions (pH 12.0) were examined by means of a luminol chemiluminescence (CL) technique and a spin-trapping fluorescence one in which terephthalic acid reacts with an OH radical to afford the highly fluorescent 2-hydroxyterephthalic acid (TAOH), respectively. The observed luminol CL intensity was remarkably enhanced by the AgO loading on TiO(2) as well as BiVO(4). This can be explained by enhancement of O(2)(-*) production on the AgO-loaded photocatalysts caused by the synergetic effects on the thermocatalytic activity upon the AgO surface and the efficient electron-hole separation at the photocatalyst/AgO interface. On the other hand, loading effects of AgO on the TAOH formation were not so significant compared to those on the CL observation, though the TAOH formation rates for the TiO(2) samples were much larger than those for the BiVO(4) ones by about three orders of magnitude. The properties of O(2)(-*) and OH radical generations on these photocatalysts are discussed on the basis of the luminol CL kinetics and approximate band edge positions of TiO(2), BiVO(4), and silver oxides.
Kohtani
Shigeru
S
Department of Pharmacy, School of Pharmacy, Hyogo University of Health Sciences, Chuo-ku, Kobe, 650-8530, Japan. kohtani@huhs.ac.jp
Yoshida
Kazuhiro
K
Maekawa
Toshiyasu
T
Iwase
Akihide
A
Kudo
Akihiko
A
Miyabe
Hideto
H
Nakagaki
Ryoichi
R
D001729:Bismuth / Q000737:chemistry*; D002384:Catalysis; D004578:Electron Spin Resonance Spectroscopy; D005453:Fluorescence; D006863:Hydrogen-Ion Concentration; D017665:Hydroxyl Radical / Q000737:chemistry; D008163:Luminescent Measurements; D008165:Luminol / Q000737:chemistry; D015394:Molecular Structure; D010087:Oxides / Q000737:chemistry*; D010777:Photochemistry; D010795:Phthalic Acids / Q000737:chemistry; D017382:Reactive Oxygen Species / Q000737:chemistry*; D012666:Semiconductors; D018030:Silver Compounds / Q000737:chemistry*; D013997:Time Factors; D014025:Titanium / Q000737:chemistry*; D014638:Vanadates / Q000737:chemistry*
D010087:Oxides; D010795:Phthalic Acids; D017382:Reactive Oxygen Species; D018030:Silver Compounds; C091754:bismuth vanadium tetraoxide; C009495:titanium dioxide; D017665:Hydroxyl Radical; D014638:Vanadates; D008165:Luminol; C406866:2-hydroxyterephthalic acid; C040225:disilver oxide; D014025:Titanium; D001729:Bismuth