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. doi:10.1021/j100292a027. 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.
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| 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. | |||||||||
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| Issue or Number: | 8 | |||||||||
| DOI: | 10.1021/j100292a027 | |||||||||
| 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: | 10 Nov 2021 22:23 |
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