Publication detail

Solar water splitting on porous-alumina-assisted TiO2-doped WOx nanorod photoanodes: Paradoxes and challenges

BENDOVÁ, M. GISPERT-GUIRADO, F. HASSEL, A. LLOBET, E. MOZALEV, A.

Original Title

Solar water splitting on porous-alumina-assisted TiO2-doped WOx nanorod photoanodes: Paradoxes and challenges

Type

journal article in Web of Science

Language

English

Original Abstract

Arrays of self-organized WO3-based semiconductor nanorods are prepared from a thin W layer, W/Ti bilayer (tungsten-on-titanium), and W-10at.%Ti alloy layer via the porous-anodic-alumina (PAA)-assisted anodization at various conditions to address the radius/length ratio of~13/130 and ~70/700 nm (respectively ‘small’ and ‘big’ nanorods). Doping the WO3 nanorods with TiO2 was achieved, for the first time, simply by anodizing the W/Ti and W-10at.%Ti layers through the alumina nanopores. The post-anodizing treatments combined PAA dissolution with annealing in air and vacuum at 500–550 °C to alter the film composition, crystal structure, and electrical properties. The air-annealed big nanorods comprising monoclinic and triclinic WO3 crystal phases reveal their superior performance in photoelectrochemical (PEC) water splitting, showing a low onset potential (0.5 VRHE) and a competitive value of photocurrent (15.5 mA·cm−2) in 0.1 mol·dm−3 Na2SO4 solution (pH 5.0) under chopped illumination at a single wavelength of 405 nm, 1 W·cm−2, with no sign of photocorrosion. Paradoxically, the presence of monoclinic WO2.9 phase in the vacuum-annealed nanorods worsens the PEC behavior and stimulates the peroxo-assisted dissolution. Unexpectedly, electrochemically doping both the WO3 and WO2.9 big nanorods with TiO2 causes the photocurrent to decrease dramatically. An advanced approach developed for modeling charge transport processes in the PAA-assisted WOx nanorods predicts a 7-fold further rise in the solar current should the big nanorods grow longer (1.5 μm) and wider (300 nm) to absorb a bigger portion of light and support a thicker depletion layer, without, however, getting fully depleted, which is the case of the small nanorods.

Keywords

anodizing; porous anodic alumina; tungsten oxide; titanium oxide; nanorods; photoelectrochemical water splitting

Authors

BENDOVÁ, M.; GISPERT-GUIRADO, F.; HASSEL, A.; LLOBET, E.; MOZALEV, A.

Released

23. 1. 2017

Publisher

Elsevier B.V.

Location

Amsterdam, The Netherlands

ISBN

2211-2855

Periodical

Nano Energy

Number

33

State

United States of America

Pages from

72

Pages to

87

Pages count

16

URL

http://dx.doi.org/10.1016/j.nanoen.2017.01.029

BibTex

@article{BUT132011,
  author="Mária {Bendová} and Francesc {Gispert-Guirado} and Achim Walter {Hassel} and Eduard {Llobet} and Alexander {Mozalev}",
  title="Solar water splitting on porous-alumina-assisted TiO2-doped WOx nanorod photoanodes: Paradoxes and challenges",
  journal="Nano Energy",
  year="2017",
  number="33",
  pages="72--87",
  doi="10.1016/j.nanoen.2017.01.029",
  issn="2211-2855",
  url="http://dx.doi.org/10.1016/j.nanoen.2017.01.029"
}