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Cobalt(II) tetrasulfophthalocyanine on titanium dioxide. 2. Kinetics and mechanisms of the photocatalytic oxidation of aqueous sulfur dioxide

Hong, Andrew P. and Bahnemann, Detlef W. and Hoffmann, Michael R. (1987) Cobalt(II) tetrasulfophthalocyanine on titanium dioxide. 2. Kinetics and mechanisms of the photocatalytic oxidation of aqueous sulfur dioxide. Journal of Physical Chemistry, 91 (24). pp. 6245-6251. ISSN 0022-3654. https://resolver.caltech.edu/CaltechAUTHORS:20150817-115453817

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Abstract

Cobalt(I1) 4,4'4″4‴-tetrasulfophthalocyanine, Co^(II)TSP, covalently linked to the surface of titanium dioxide particles, TiO_2-CoTSP, is shown to be an effective photocatalyst for the oxidation of sulfur(IV) to sulfur(VI) in aqueous suspensions. Upon band-gap illumination of the semiconductor, TiO_2, conduction-band electrons and valence-band holes are separated; the electrons are channeled to the bound Co^(II)TSP complex resulting in the reduction of dioxygen while the holes react with adsorbed S(IV) to produce S(VI) in the form of sulfate. The formation of S(V) radicals indicates that the reaction proceeds via successive one-electron transfers. Quantum yields in excess of unity were observed and attributed to desorption of SO_3^- from the TiO_2 surface and subsequent initiation of a homogeneous free radical chain reaction. Observed quantum yields between 0.5 and 300 depend on the concentration and nature of free radical inhibitors present in the suspension. A kinetic model that integrates the photon absorption properties of the solid, the heterogeneous redox reactions on the catalyst surface, and the homogeneous reactions of S(IV) is presented.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1021/j100308a035DOIArticle
http://pubs.acs.org/doi/abs/10.1021/j100308a035PublisherArticle
ORCID:
AuthorORCID
Hoffmann, Michael R.0000-0001-6495-1946
Additional Information:© 1987 American Chemical Society. Received: May 7, 1987. We gratefully acknowledge the financial support of the U.S. Environmental Protection Agency (R811612-01-0). In addition we want to thank Dr. Donald Carey for his encouragement and support. Samples of P25 TiO_2 were provided by the Degussa Corp.
Funders:
Funding AgencyGrant Number
Environmental Protection Agency (EPA)R811612-01-0
Issue or Number:24
Record Number:CaltechAUTHORS:20150817-115453817
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20150817-115453817
Official Citation:Cobalt(II) tetrasulfophthalocyanine on titanium dioxide. 2. Kinetics and mechanisms of the photocatalytic oxidation of aqueous sulfur dioxide Andrew P. Hong, Detlef W. Bahnemann, and Michael R. Hoffmann The Journal of Physical Chemistry 1987 91 (24), 6245-6251 DOI: 10.1021/j100308a035
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:59584
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:17 Aug 2015 22:24
Last Modified:03 Mar 2020 13:01

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