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TiO2-polyheptazine hybrid photoanodes: Effect of cocatalysts and external bias on visible light-driven water splitting

Published online by Cambridge University Press:  28 September 2012

Michal Bledowski
Department of Inorganic Chemistry II, Faculty of Chemistry and Biochemistry, Ruhr University Bochum, 44780 Bochum, Germany
Lidong Wang
Department of Inorganic Chemistry II, Faculty of Chemistry and Biochemistry, Ruhr University Bochum, 44780 Bochum, Germany
Ayyappan Ramakrishnan
Department of Inorganic Chemistry II, Faculty of Chemistry and Biochemistry, Ruhr University Bochum, 44780 Bochum, Germany
Radim Beranek*
Department of Inorganic Chemistry II, Faculty of Chemistry and Biochemistry, Ruhr University Bochum, 44780 Bochum, Germany
a)Address all correspondence to this author. e-mail:
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Photoanodes based on TiO2-polyheptazine (TiO2-PH) hybrids are, due to the energetics of photogenerated charges, very promising for solar water splitting in terms of possibly reduced need for external electric bias. Visible (λ > 420 nm) light-driven photooxidation of water at TiO2-PH electrodes loaded with two different metal oxide cocatalysts was investigated. As compared with TiO2-PH photoanodes loaded with colloidal [iridium (IV) oxide] IrO2 deposited by colloidal deposition, photoelectrodes modified with CoOx oxygen-evolving cocatalyst (Co-Pi) deposited by photoassisted deposition precipitation method showed both higher photocurrents and more efficient oxygen evolution under prolonged irradiation. The minimum external electric bias needed to observe complete photooxidation of water to dioxygen at TiO2-PH photoanodes modified with Co-Pi was estimated to be ∼0.6 V at pH 7. The key factor limiting the photoconversion efficiency at low bias potentials is the fast primary recombination of photogenerated charges.

Copyright © Materials Research Society 2012

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