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Catalysts 2019, 9(2), 204; https://doi.org/10.3390/catal9020204

Radiative and Non-Radiative Recombination Pathways in Mixed-Phase TiO2 Nanotubes for PEC Water-Splitting

1
Regional Centre of Advanced Technologies and Materials, Faculty of Science, Palacký University Olomouc, 17. listopadu 1192/12, 771 46 Olomouc, Czech Republic
2
Department of Materials Science and Engineering, University of Erlangen-Nuremberg, Martensstrasse 7, D-91058 Erlangen, Germany
*
Authors to whom correspondence should be addressed.
Received: 22 January 2019 / Revised: 18 February 2019 / Accepted: 19 February 2019 / Published: 23 February 2019
(This article belongs to the Special Issue Nanostructured Materials for Photocatalysis)
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Abstract

Anatase and rutile mixed-phase TiO2 with an ideal ratio has been proven to significantly enhance photoelectrochemical (PEC) activity in water-splitting applications due to suppressing the electron–hole recombination. However, the mechanism of this improvement has not been satisfactory described yet. The PEC water oxidation (oxygen evolution) at the interface of TiO2 photoanode and electrolyte solution is determined by the fraction of the photogenerated holes that reach the solution and it is defined as the hole transfer efficiency. The surface and bulk recombination processes in semiconductor photoanodes majorly influence the hole transfer efficiency. In this work, we study the hole transfer process involved in mixed-phase TiO2 nanotube arrays/solution junction using intensity-modulated photocurrent and photovoltage spectroscopy (IMPS and IMVS); then, we correlate the obtained hole transfer rate constants to (photo)electrochemical impedance spectroscopy (PEIS) measurements. The results suggest that the enhanced performance of the TiO2 mixed-phase is due to the improved hole transfer rate across the TiO2/liquid interface as well as to the decrease in the surface trap recombination of the holes. View Full-Text
Keywords: charge transfer; intensity-modulated photocurrent spectroscopy; phase transitions; photoelectrochemical impedance spectroscopy; water-splitting charge transfer; intensity-modulated photocurrent spectroscopy; phase transitions; photoelectrochemical impedance spectroscopy; water-splitting
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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Yalavarthi, R.; Naldoni, A.; Kment, Š.; Mascaretti, L.; Kmentová, H.; Tomanec, O.; Schmuki, P.; Zbořil, R. Radiative and Non-Radiative Recombination Pathways in Mixed-Phase TiO2 Nanotubes for PEC Water-Splitting. Catalysts 2019, 9, 204.

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