Photocatalysis Involving a Visible Light-Induced Hole Injection in a Chromate(VI)鈥揟iO2 System

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• 作者：Joanna Kuncewicz ; Przemys艂aw Z膮bek ; Krzysztof Krucza艂a ; Konrad Szaci艂owski ; Wojciech Macyk
• 刊名：The Journal of Physical Chemistry C
• 出版年：2012
• 出版时间：October 18, 2012
• 年：2012
• 卷：116
• 期：41
• 页码：21762-21770
• 全文大小：389K
• 年卷期：v.116,no.41(October 18, 2012)
• ISSN：1932-7455

文摘

The photocatalytic activity of materials synthesized by titanium dioxide impregnation with chromates(VI) was studied in the processes of 4-chlorophenol oxidation and photocurrent generation. The materials show measurable activity when excited with visible light. Electron paramagnetic resonance (EPR) studies revealed the presence of chromium(V) species even without irradiation. Detection of photogenerated reactive oxygen species, together with elucidation of electrochemical properties of the materials, enabled assumption of a very unique mechanism of TiO₂ photosensitization, involving a photoinduced hole injection from the excited photosensitizer species to the valence band. Photoelectrochemical studies revealed that visible light induced both hole injection to the valence band and electron injection to the conduction band, depending on the electrode potential. The former process is responsible for anodic, whereas the latter is responsible for cathodic photocurrent generation. This counterintuitive behavior results from a peculiar arrangement of electronic levels in the studied systems. Although the (photo)stability of studied materials, as well as the efficiency of the photosensitization process are moderate, the system represents a very unique and therefore interesting mode of titania photosensitization.