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Paper   IPM / Physic / 15295
School of Physics
  Title:   Evolution of rough-surface geometry and crystalline structures of aligned TiO2 nanotubes for photoelectrochemical water splitting
1.  M. Zare
2.  Sh. Solaymani
3.  A. Shafiekhani
4.  S. Kulesza
5.  S. Talu
6.  M. Bramowicz
  Status:   Published
  Journal: Scientific Reports
  No.:  10870
  Vol.:  8
  Year:  2018
  Pages:   1-11
  Publisher(s):   Nature
  Supported by:  IPM
Nowadays, increasing awareness of environment and fossil fuels protection stimulates intensive research on clean and renewable sources of energy. Production of hydrogen from water through solar-driven splitting reactions is one of the most promising approaches in the field of photoelectrochemistry (PEC). In this work we have fabricated well-aligned, highly-ordered, smooth-mouth TiO2 nanotube arrays (TNAs) in a two-step anodization process of titanium foil, which were then used as photoelectrodes for PEC water splitting. It demonstrates for the first time correspondence between non-linear component characteristics of multiscale rough surface and crystalline structure of annealed TNAs measured at various fabrication stages and their photoelectrochemical response. The as-anodized TNAs with isotropic surface (deduced from AFM and SEM images) and largest figure of merit (according to their PEC performance) were annealed at 450�??°C in air. Scale-invariant descriptors of the surface structure of the deposits involved: fractal dimension, corner frequency, roughness, size of nanostructures and their dominant habits. Moreover, X-ray diffraction data processed using the Rietveld method confirmed co-existence of various oxides, for example: TiO2 in the form of anatase, TiO and Ti3O5 phases in the TNAs under study pointing that previous well-established mechanisms of the TNA growth were to certain degree incomplete.

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