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Assessing the photoelectrochemical properties of C, N, F codoped TiO2 nanotubes of different lengths

Abstract

The aim of this work has been the photoelectrochemical (PEC) study of nanostructured photoanodes based on TiO2. Highly ordered and well adhered TiO2 nanotubes (TNTs) of different lengths (∼2–20 μm) were prepared in a two-step process in ethylene glycol solutions containing fluorides, and detailed XPS analysis showed that they have become co-doped with C, N and F. PEC measurements revealed that increasing surface area is not followed by increase in the photoconversion efficiency, but rather that an optimal balance between electroactive surface area (ESA) and charge carrier concentration exists. TNTs of around 10 μm show the optimum incident photon-to-current efficiency (IPCE) of ∼33% and an overall photoconversion efficiency of ∼6.3% under UV illumination of 4 mW cm−2 light intensity. Finally, Mott-Schottky analysis revealed significant frequency dispersion of the estimated space charge layer capacitance, which renders the accurate estimation of the flatband position and charge carrier concentration unreliable. On the other hand, more realistic charge carrier concentrations can be obtained by normalizing the capacitance per ESA.
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Category

Academic article

Client

  • Research Council of Norway (RCN) / 239211

Language

English

Author(s)

Affiliation

  • University of Oslo
  • SINTEF Industry / Materials and Nanotechnology
  • SINTEF Industry / Sustainable Energy Technology

Year

2017

Published in

Catalysis Today

ISSN

0920-5861

Publisher

Elsevier

Volume

287

Page(s)

161 - 168

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