5 years ago

Photoelectrochemical H2 Generation from Suboxide TiO2 Nanotubes: Visible-Light Absorption versus Conductivity

Photoelectrochemical H2 Generation from Suboxide TiO2 Nanotubes: Visible-Light Absorption versus Conductivity
Shiva Mohajernia, Nhat Truong Nguyen, Patrik Schmuki, Anca Mazare, Seyedsina Hejazi
In the present work we report on the key factors dictating the photoelectrochemical (PEC) performance of suboxide titania (TiOx) nanotubes. TiOx nanotubes were produced by a systematic variation of reduction heat treatments of TiO2 in Ar/H2. The properties of the TiOx tubes were investigated by electron paramagnetic resonance (EPR), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), solid-state conductivity, reflectivity measurements, photocurrent spectroscopy, and photoelectrochemical hydrogen evolution. In line with earlier literature, these suboxide tubes show a drastically improved photoelectrochemical water-splitting performance compared to non-reduced anatase TiO2 tubes. In this work we show that the key improvement in water-splitting performance is due to the strongly improved conductivity of TiOx semimetalic tubes, reaching 13.5 KΩ per tube compared to 70 MΩ (for non-reduced anatase), and is not due to the enhanced visible-light absorbance. Ar/H2 treatment of anodic titania nanotube layers leads to drastically enhanced electron transport. Reduced TiOx nanotubes were obtained by a systematic variation of the reduction heat treatment. Such nanotubes show a significant enhancement in conductivity and photoelectrochemical performance, with a significantly enhanced photoresponse in the visible range compared to the pristine anatase TiO2 nanotubes (see scheme).

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/chem.201702245

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