Titania-based heterogeneous photocatalysis. Materials, mechanistic
issues, and implications for environmental remediation*
Krishnan Rajeshwar, C. R. Chenthamarakshan, Scott Goeringer, and Miljana
Djukic
Department of Chemistry and Biochemistry, The University
of Texas at Arlington, Arlington, TX 76019-0065, USA
Abstract: Using hexavalent chromium [Cr(VI)] and methylene blue
(MB) as model substrates, we discuss three aspects of TiO2-based heterogeneous
photocatalysis. We show first that a given TiO2 sample may not be simultaneously
optimal for photocatalytically driving the reduction of Cr(VI) and the
oxidation of MB. We further show that a TiO2 sample that strongly adsorbs
either of these substrates in the dark is not optimal as a photocatalyst.
The other two aspects concern circumventing the rather poor surface
catalytic properties and visible light photoresponse of TiO2, respectively.
Strategies revolving around the visible light photoexcitation of the
substrate itself and metal-modification of the TiO2 surface, are described
as possible solutions.
* An issue of reviews and research papers based on
presentations made at the IUPAC/ICSU Workshop on
Electrochemistry and Interfacial Chemistry in Environmental Clean-up
and Green Chemical Processes, Coimbra, Portugal, 6-7 April, 2001.
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