The role of photoinduced defects in TiO2 and its effects on hydrogen evolution from aqueous methanol solution.
The hydrogen evolution from aqueous methanol solutions was found to follow two stages of zero order kinetics during photoreactions using TiO 2 as the photocatalyst. Maximal hydrogen evolution was found at the 10% (v/v) methanol solution. X-ray photoelectron spectroscopy (XPS) shows that Ti(1566) defects are formed on the surface of TiO 2 and X-ray powder diffraction (XRD) indicates that Ti(1566) defects are also formed in the bulk after photoreaction. Formation of defects is also shown by broadening of Bragg peaks and blue shifts and peak broadening in Raman spectroscopy. The defect disorder results in the increase of hydrogen evolution. UV-vis diffuse reflection spectra confirm that new absorptions in the visible light region are related to the defect content. At high methanol concentration, XPS implies that the active sites of the surface are blocked by hydroxyl groups, which results in the decrease of hydrogen evolution. TEM images showed that the photoreaction occurred on the surface of the photocatalyst as the surface of the TiO 2 became rough after the photoreaction.
Yang
Xiaoyi
X
Inorganic Chemistry Laboratory, University of Oxford, South Parks Road, OX1 3QR, United Kingdom.
Salzmann
Christoph
C
Shi
Huahong
H
Wang
Hongzhi
H
Green
Malcolm L H
ML
Xiao
Tiancun
T
D002384:Catalysis; D006859:Hydrogen / Q000737:chemistry*; D007700:Kinetics; D000432:Methanol / Q000737:chemistry*; D010316:Particle Size; D010777:Photochemistry; D012996:Solutions / Q000737:chemistry; D013053:Spectrophotometry; D013056:Spectrophotometry, Ultraviolet; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry*; D014867:Water / Q000737:chemistry; D014965:X-Rays
D012996:Solutions; D014867:Water; C009495:titanium dioxide; D006859:Hydrogen; D014025:Titanium; D000432:Methanol