Photoelectrochemical reduction rate of ferricyanide at different TiO2 forms: comparison of SECM and cyclic voltammetric results
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Author list: Devkota, Manoj; Chuangchote, Surawut; La-o-vorakiat, Chan; Lertsathitphong, Panjaphong; Lertanantawong, Benchaporn; Somasundrum, Mithrane; Surareungchai, Werasak;
Publisher: Springer
Publication year: 2021
Volume number: 25
Issue number: 5
Start page: 1691
End page: 1698
Number of pages: 8
ISSN: 1432-8488
eISSN: 1433-0768
Languages: English-Great Britain (EN-GB)
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Abstract
The heterogeneous rate constant (k) for the reduction of Fe(CN)63- at different UV-illuminated TiO2 polymorphs was determined by (1) cyclic voltammetry (CV) where a TiO2-modified fluorine-doped tin oxide (FTO)-coated glass was the working electrode, and (2) SECM approach curves at the same electrodes at open circuit. The combination of Fe(CN)63- with photogenerated electrons was found to be the rate determining step. The magnitude of the SECM values of k were in the order: anatase-rutile > anatase > rutile > amorphous, which agrees with the generally accepted photocatalytic efficiencies of the TiO2 polymorphs. In contrast, the CV-determined values of k followed the sequence: amorphous > rutile > anatase-rutile > anatase and were approximately one order of magnitude lower than the SECM-determined values. We suggest this indicates the CV determination of rate constants at photoactive films is problematic, due to factors such as reaction at the underlying electrode and the uncompensated resistance of the film. © 2021, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.
Keywords
Rate constant, SECM
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