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J Phys Chem Lett. 2014 Aug 21;5(16):2890-6. doi: 10.1021/jz5014505. Epub 2014 Aug 11.

Unveiling Two Electron-Transport Modes in Oxygen-Deficient TiO2 Nanowires and Their Influence on Photoelectrochemical Operation.

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Department of Chemistry, William Mong Institute of Nano Science and Technology, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.


Introducing oxygen vacancies (VO) into TiO2 materials is one of the most promising ways to significantly enhance light-harvesting and photocatalytic efficiencies of photoelectrochemical (PEC) cells for water splitting among others. However, the nature of electron transport in VO-TiO2 nanostructures is not well understood, especially in an operating device. In this work, we use the intensity-modulated photocurrent spectroscopy technique to study the electron-transport property of VO-TiO2 nanowires (NWs). It is found that the electron transport in pristine TiO2 NWs displays a single trap-limited mode, whereas two electron-transport modes were detected in VO-TiO2 NWs, a trap-free transport mode at the core, and a trap-limited transport mode near the surface. The considerably higher diffusion coefficient (Dn) of the trap-free transport mode grants a more rapid electron flow in VO-TiO2 NWs than that in pristine TiO2 NWs. This electron-transport feature is expected to be common in other oxygen-deficient metal oxides, lending a general strategy for promoting the PEC device performance.


TiO2 nanowires; oxygen-deficient; photoelectrochemical water splitting; trap-free electron transport


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