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Cobalt(II) tetrasulfophthalocyanine on titanium dioxide: A new efficient electron relay for the photocatalytic formation and depletion of hydrogen peroxide in aqueous suspensions

Hong, Andrew P. and Bahnemann, Detlef W. and Hoffmann, Michael R. (1987) Cobalt(II) tetrasulfophthalocyanine on titanium dioxide: A new efficient electron relay for the photocatalytic formation and depletion of hydrogen peroxide in aqueous suspensions. Journal of Physical Chemistry, 91 (8). pp. 2109-2117. ISSN 0022-3654. https://resolver.caltech.edu/CaltechAUTHORS:20150817-151000229

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Abstract

A novel synthesis for the covalent linkage of cobalt(II) tetrasulfophthalocyanine (Co^(II)TSP) to the surface of titanium dioxide (TiO_2) particles (d ≤ 0.5 µm) is described. Upon irradiation with light that exceeds the bandgap energy (E_g) of TiO_2 (i.e., ⋋ 5 380 nm), Co^(II)TSP is reduced to Co^ITSP under anoxic conditions both as a dry powder and in aqueous suspension. The photochemical reduction is shown to be fully reversible in the presence of molecular oxygen (O_2). Hydrogen peroxide (H_2O_2) is produced upon irradiation of an aerated aqueous suspension of the 'hybrid" catalyst, TiO__2-Co^(II)TSP. Formation kinetics are followed in situ with a polarographic detector (detection limit ≃ 10^(7-) M H_2O_2); quantum yields, ϕ_(H_2O_2) between 0.16 and 0.49 have been determined. The reactive photocatalytic center appears to be generated by the attachment of molecular oxygen in the open apical coordination site of the hybrid Co^(II)TSP complex. Formation of Co^(II)TSP-O_2^(•-) is enhanced by the binding of TiO^- surface groups in the opposite apical position. Hydrogen peroxide is produced in a two-step electron transfer from the conduction band via the Co(III) center. The involvement of free radical intermediates in this mechanism appears to be highly unlikely. On the basis of its observed chemical and photochemical stability and the high quantum yields for O_2 reduction, the newly developed hybrid material is proposed to be applicable as a potent and stable oxidation catalyst.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1021/j100292a027DOIArticle
http://pubs.acs.org/doi/abs/10.1021/j100292a027PublisherArticle
ORCID:
AuthorORCID
Hoffmann, Michael R.0000-0001-6495-1946
Additional Information:© 1987 American Chemical Society. Received: November 6, 1986. Publication Date: April 1987. We gratefully acknowledge the financial support of the U.S. EPA (Grants CR812356-01-0 and R811612-01-0), and in particular we want to thank Drs. Donald Carey and Marcia Dodge for their support. Free samples of titanium dioxide P25 from the Degussa Corp. were highly appreciated.
Funders:
Funding AgencyGrant Number
Environmental Protection Agency (EPA)CR812356-01-0
Environmental Protection Agency (EPA)R811612-01-0
Issue or Number:8
Record Number:CaltechAUTHORS:20150817-151000229
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20150817-151000229
Official Citation:Cobalt(II) tetrasulfophthalocyanine on titanium dioxide: A new efficient electron relay for the photocatalytic formation and depletion of hydrogen peroxide in aqueous suspensions Andrew P. Hong, Detlef W. Bahnemann, and Michael R. Hoffmann The Journal of Physical Chemistry 1987 91 (8), 2109-2117 DOI: 10.1021/j100292a027
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:59659
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:19 Aug 2015 17:34
Last Modified:03 Mar 2020 13:01

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